Yak Tunnel/California Gulch Remedial Investigation February 28, 1986

! I *••-.. f"' YAK TUNNEL / CALIFORNIA GULCH REMEDIAL INVESTIGATION DMINISTR RECOR

PREPARED FOR STATE OF COLORADO DEPARTMENT OF LAW

FEBRUARY 28,1936

PREPARED BY ENGINEERING-SCIENCE, INC, 1100^TOUDENV^t, TCOLORAD STREETO 8020, SUIT4 E 1100 IN COOPERATION Wl THE U.S. ENVIRONMENTAL PROTECTION AGENCY TABLE OF CONTENTS

EXECUTIVE SUMMARY Goals of the Remedial Investigation i Site Description and Background Information i Major Findings ii CHAPTER 1 - INTRODUCTION 1-1 CHAPTER 2 - SITE DESCRIPTION AND BACKGROUND INFORMATION Sources, Pathways, and Receptors of Contamination 2-4 Sources 2-4 Pathways and Receptors 2-7 Hazard Evaluation of Selected Hazardous Substances 2-8 Human Health 2-8 Wildlife 2-9 Vegetation 2-9 Aquatic life 2-10 Demographics 2-10 Land Use 2-12 _jP.laiife 2-13 —- Climatology 2-13 CHAPTER 3 - SITE HISTORY AND GEOLOGY History 3-1 Historical Water Quality of Yak Tunnel Drainage 3-9 Historical Water Quality of the Leadville Mine Drainage Tunnel 3-9 Tailings and Mill History 3-12 Mining Activities 3-15 Underground Mining 3-15 Milling Processes 3-17 Smelter Residues and Emissions 3-18 Site Geology 3-19 Surficial Materials 3-19 Bedrock Geology 3-20 Ore Deposits 3-22 Geochemistry Metal Dispersion from Mineralization 3-24 Sulfide Oxidation Processes 3-26 Metal Dispersion in Surface and Ground Waters . 3-27 Metals in Soils 3-31 CHAPTER 4 - MINING WASTE INVESTIGATION Tailings Ponds-.-. 4-rl Waste Piles 4-8 California Gulch 4-8 Stray Horse Gulch 4-11 Contaminated Soils and Sediment 4-12 CHAPTER 5 - GROUND WATER INVESTIGATION Resources and Uses 5-2 Occurrence 5-2 Uses 5-5 Nature and Extent of Contamination 5-10 California Gulch 5-12 Arkansas River Alluvium 5-32 Environmental and Public Health Effects 5-33 CHAPTER 6 - SURFACE WATER INVESTIGATION Resources and Uses 6-1 Description 6-1 Potential for Flood Damage 6-5 Water Use and Supply 6-6 Nature and Extent of Contamination 6-9 Past Studies 6-9 CERCLA Investigations 6-15 EPA CERCLA Investigations 6-15 Engineering-Science CERCLA Investigations 6-42 Enviromental and Public Health Effects 6-81 CHAPTER 7 - AQUATIC BIOTA INVESTIGATION Resources and Use 7-2 Macrohabitat 7-2 Aquatic Biota 7-4 Nature and Extent of Contamination 7-5 Sampling Stations 7-5 Sampling Methods 7-6 Sampling Results " 7-7 Discussion of Contaminants 7-21 Contaminants of Concern and Their Extent in the Arkansas River 7-22 Impacts to the Aquatic Biota Resource 7-41 CHAPTER 8 - SOILS INVESTIGATION Resources and Use 8-1 Nature and Extent of Contamination 8-3 Soil Physical/Chemical Characteristics of Concern 8-3 Toxic Substances of Concern 8-6 Cumulative Geographic Extent of Contamination 8-17 Statistical Analysis of Data 8-26 Metals Concentrations 8-28 Environmental and Public Health Effects 8-36 CHAPTER 9 - VEGETATION INVESTIGATION Resources and Sse 9-1 Nature and Extent of Contamination 9-2 Contaminants of Concern 9-2 Geographic Extent of Contamination in Vegetation 9-9 Results 9-13 Tennessee Creek Valley and Arkansas River Valley Pastures 9-13 Tennessee Creek Valley and Arkansas River Valley Wetlands 9-23 California Gulch and Stray Horse Gulch 9-24 Environmental and Public Health Effects 9-24 CHAPTER 10 - AIR QUALITY INVESTIGATION Site Description 10-1 Nature and Extent of Contamination 10-2 Sources 10-3 Receptors 10-3 Transport Mechanism 10-5 Source/Receptor Relationship 10-5 Long-term Impact 10-9 Environmental and Public Health Effects 10-11 CHAPTER 11 - GENERAL RESPONSE ACTIONS AND TECHNOLOGIES Introduction 11-1 Summary of Site Problems 11-2 General Response Actions 11-2 Formation of Remedial Technologies 11-3 References Cited R-l LIST OF TABLES Number Title Page 2.1 Populations of Lake County and Leadville 1900-1983 with Forecasts through 2010 2-11 2.2 Annual and 10-Year Average Precipitation (inches) • 2-15 3.1 Yearly Concentrations of Hazardous Metals in the Yak Tunnel Drainage 3-10 3.2 Yearly Concentrations of Hazardous Metals (Zinc) in the Leadville Drainage Tunnel Discharge 3-11 3.3 Mobility of Some Elements in Surficial Environments 3-32 4.1 Chemical Analysis of Tailings Pond 3 4-4 4.2 Analysis of Tailings Samples from Leadville, Colorado (EPA Data) 4-6 4.3 Soils/Tailing EP-Toxicity Data (EPA Data) 4-7 4.4 Summary of Waste Rock Pile Geochemistry and Other Parameters, California Gulch and Stray Horse Gulch (ES Data) 4-10 4.5 Summary of Geochemistry and other Parameters for Soils and Sediments in California and Stray Horse Gulch (ES Data) 4-14 4.6 Analysis of Soils Samples from Leadville, Colorado (EPA Data) 4-16 5.1 Summary of PEA Monitoring Well Construction Data 5-7 5.2 Summary of Existing Well Construction Data 5-9 5.3 Private Wells Currently in Use 5-11 5.4 Yak Tunnel/California Gulch Summary of Ground Water Sampling Results (mg/1) 5-19 5.5 Federal and State Water Quality Standards 5-24 5.6 Summary of Private Well Sampled by EPA 5-28 5.7 Summary of results from Private Wells Sampled by ES 5-31 6.1 Arkansas River Basin Affected by Metal Mine Drainage 6-10 6.2 Water Quality Data from STORET on the Arkansas River from Leadville to Near Canon City 6-12 6.3 EPA and Es Sampling Location Descriptions for California Gulch and its Tributaries 6-16 6.4 EPA Surface Water Data Summary 6-19 6.5 Federal and State Water Quality Standards 6-28 6.6 EPA Surface Water Data Summary 6-34 6.7 Total Cadmium Loading Values from EPA Data 6-36 6.8 Total Copper Loading Values from EPA Data 6-37 6.9 Total Lead Loading Values from EPA Data 6-38 6.10 Total Zinc Loading Values from EPA Data 6-39 6.11 Total Metals in the Upper Arkansas River 6-70 7.1 Concentrations of Metals (mg/kg) from Invertebrates taken from the Arkansas River and Tributaries during May and October, 1985 7-8 7.2 Concentrations of Metals (mg/kg) from Sediment taken from the Arkansas River and Tributaries during October, 1985 7-9 7.3 Number of Aquatic Macroinvertebrates per Square Meter Collected from the Arkansas River and Associated Tributaries in 1985 (ES Data) 7-12 7.4 Habitat Description of Fish Sampling Stations 7-14 7.5 Fish Collected from the Arkansas River and Tributaries during September, 1985 7-16 7.6 Fish Collected from the Arkansas River and Tributaries during October, 1985 7-17 7.7 Maximum Allowable Concentrations (mg/1) for Specific Metals based on Toxicity Data 7-24 7.8 Acutely and Chronically Toxic Concentrations of Lead to Trout 7-26 7.9 Acutely and Chronically Toxic Concentrations of Copper to Trout 7-28 7.10 Acutely and Chronically Toxic Concentrations of Zinc to Trout 7-32 7.11 Acutely and Chronically Toxic Concentrations of Cadmium to Trout 7-36 7.12 Means and Ranges of Concentrations (mg/1) of Selected Metals in Water of the Arkansas River with Concentrations above EPA Criteria Levels Noted 7-38 8.1 Ranges of Total Metal Concentrations in Reference Locations, Contaminated Sites, "Normal" Levels, Regulatory Limits, and Known Toxic Levels 8-7 8.2 Arkansas River Valley Total Soil Metals and pH 8-17 8.3 Arkansas River Valley Plant-Available Metals 8-20 8.4 Vertical Distribution of Mean Total and Plant-Available Metal Concentrations in the Soil Profile-Arkansas River Valley 8-33 9.1 Summary of Metals Concentrations in Plant Tissues 9-4 9.2 Summary of Plant Cover Data for Irrigated Pastures 9-14 9.3 Plant Production and Percent Utilization 9-16 9.4 Summary of Plant Tissue, Cover and Production Data 9-17 10.1 Selected Toxic Composition of Tailings Pond and Dust Samples 10-4 10.2 Particle Size Analysis of Mine Tailings in California Gulch 10-6 10.3 Comparison of Dust Constituents (Percent of Metals Analyzed) 10-8 11.1 Mining Wastes 11-4 11.2 Ground Water 11-7 11.3 Surface-Water 11-8 11.4 Aquatic Biota, Soils and Vegetation, and Air Quality 11-11 LIST OF FIGURES Number Title 2.1 Location Map 2.2 Geographical Features and Outline of Productive Area, Leadville District, Colorado 2-3 2.3 Mine Wastes and Slag Piles in and Near the California Gulch Drainage Area 2-5 2.4 Precipitation 2-16 3.1 View of Leadville from Carbonate Hill 3-3 3.2 Carbonate Hill 3-4 3.3 Smelters with Mines Near Leadville Looking West 3-5 3.4 Plan View of Yak Tunnel 3-7 3.5 Location of Tailings Ponds 3-13 3.6 Mining/Process Schematic 3-16 3.7 Principal Faults and Areas of Principal Ore Bodies 3-21 3.8 Bedrock Geology Map 3-22 4.1 Waste Pile and Soil/Sediment Sample Locations- Stray Horse and California Gulches 4-2 5.1 Elevation of Potentiometrie Surface, 1944 5-4 5.2 Monitoring Well Location Map 5-6 5.3 private Wells Location Map 5-8 5.4 Surface Flow and Ground Water Level 5-14 5.5 Dissolved Cadmium Concentration 5-15 5.6 Sulfate Concentration 5-16 6.1 Location Map 6-3 6.2 Fryingpan-Arkansas Project Map 6-7 6.3 EPA Surface Water Sampling Map 6-18 6.4 Dissolved Zinc in California Gulch 6-30 6.5 Dissolved Zinc in California Gulch 6-31 6.6 Total Cadmium in California Gulch 6-32 6.7 Dissolved Cadmium in California Gulch 6-33 6.8 Cadmium Mass Loadings in California Gulch 6-40 6.9 Zinc Mass Loadings in California Gulch 6-41 6.10 Surface Water Sampling Locations along California Gulch 6-43 6.11 Surface Water Sampling Locations along the Arkansas River 6-44 6.12 California Gulch Reaches 6-47 6.13 Arkansas River Reaches 6-48 6.14 Cadmium in California Gulch (May, 1985) 6-49 6.15 Cadmium in California Gulch (June, 1985) 6-50 6.16 Cadmium in California Gulch (August, 1985) 6-51 6.17 Copper in California Gulch (May, 1985) 6-52 6.18 Copper in California Gulch (June, 1985) 6-53 6.19 Copper in California Gulch (August, 1985) 6-54 6.20 Lead in California Gulch (May, 1985) 6-55 6.21 Lead in California Gulch (June, 1985) 6-56 6.22 Lead in California Gulch (August, 1985) 6-57 6.23 Zinc in California Gulch (May, 1985) 6-58 6.24 Zinc in.California Gulch (June, 1985) 6-59 6.25 Zinc in California Gulch (August, 1985) 6-60 6.26 Cadmium Distribution in the Arkansas River System (August, 1985) 6-67 6.27 Copper Distribution in the Arkansas River System (August, 1985) 6-68 6.28 Zinc Distribution in the Arkansas River System (August, 1985) 6-69 6.29 Cadmium in the Arkansas River 6-73 6.30 Copper in the Arkansas River 6-74 6.31 Zinc in the Arkansas River 6-75 6.32 Arkansas River Sediments (Cadmium) 6-77 6.33 Arkansas River Sediments (Copper) 6-78 6.34 Arkansas River Sediments (Lead) 6-79 6.35 Arkansas River Sediments (Zinc) 6-80 7.1 Aquatic Life Sampling Stations 7-2 7.2 Length-Frequency Distribution of Brown Trout from the Arkansas River-October, 1985 7-20 8.1 Solubilities of Some Meal Species at Various pH Values 8-5 8.2 Range of Total Soil Arsenic Concentration in Control Areas and Areas above and below California Gulch 8-9 8.3 Range of Total Soil Cadmium Concentration in Control Areas and Areas above and below California Gulch 8-10 8.4 Range of Total Soil Copper Concentration in Control Areas and Areas above and below California Gulch 8-11 8.5 Range of Total Soil Lead Concentration in Control Areas and Areas above and below California Gulch 8-12 8.6 Range of Total Soil Zinc Concentration in Control Areas and Areas above and below California Gulch 8-13 8.7 Arkansas River Valley Maximum Total Metals 8-14 8.8 Soil Sample Locations in the Arkansas River Valley 8-13 8.9 Arkansas River Valley Maximum Available Metals 8-25 9.1 Location of Vegetation Sample Points 9-10 9.2 Maximum Concentration of Metals in Irrigated Pasture Vegetation of the Arkansas River Valley 9-18 9.3 Mean Concentration of Metals in Irrigated Pasture Vegetation of the Arkansas River Valley 9-19 10.1 Comparison of Dust Constituents for Selected Metals 10-10 Precipitation Monthly

0 o '"a.u

Nov-82 Way-83 Nov—83 May—84 Nov-84 May-85 Precipitation Cumulative _ > 16 - ; ^; 15 - > < T » s T» •« 14 - . • , - V • . V . 13 - > i > s V » 1 * • in 12 - . > , . > . > . , V s

Month Actual 10 Year Average T Sampling Event FIGURE 2.4 CALIFORNIA GULCPRECIPITATIOH Rl, LEADVILLEN , COLORADO YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION fairly regular annual cycle. The planned sample cycle of 1984-85 was close to average, and, therefore should be representative of normal behavior for the hydrologic regime of the California Gulch. The precipitation and weather cycle give rise to an annual peak runoff usually occurring during June. This is depicted in the hydro- graph for the middle flume presented in the streamflow section of EPA Appendix N.

2-17 YAK TUNNEL/CALIFORNIA GULCH REMEDIAL INVESTIGATION FEBRUARY 28, 1986

Prepared for State of Colorado Department of Law

BY Engineering-Science, Inc. 1100 Stout Street, Suite 1100 Denver, Colorado 8020A

In Cooperation with the U.S. Environmental Protection Agency YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION CHAPTER 3 SITE HISTORY AND GEOLOGY

Mining In the historic Leadville mining district began in 1860 following the discovery of placer gold in California Gulch. Placer deposits were quickly exhausted and beginning in the late 1870's mining activities were primarily underground. As the mines went deeper, ground water flooding became a problem. The water had to be pumped out, increasing the expense of mining. Between 1889 and 1913 the Yak Tunnel was constructed to dewater, underground mine working, and haul ore from a major portion of the district. The waters discharging from the Yak Tunnel contain several hazardous metals, cadmium, copper, lead, and zinc. Naturally occuring sulfide minerals are the source of acid, and the primary source of hazardous metals In the district. Prior to mining, sulfide minerals occured below the local ground water table but were not exposed at the surface. As a result of mining, sulfide minerals were brought to the surface and deposited in waste rock piles and tailings ponds, where oxidation and bacteriological activity produce sulfuric acid and release hazardous metals, arsenic, cadmium, copper, lead, and zinc. Prior to the extensive disturbance of the Leadville district by mining, the natural mineralization probably contributed little pollution to the upper Arkansas River. HISTORY Presented below is a brief synopsis of historical highlights according to Blair (1980).

3-1 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION I«S7 The discovery of gold in the California Gulch in-1957 brought a Colorado gold rush on the heels of the California gold rush. Small- scale placer raining continued for several years, bringing fortune seekers who failed to "strike it rich" in California. In 1868, gold ore veins were found and several small stamp mills were built. However, problems with water, labor, and transportation made mining the ore veins difficult so that by 1872 only a few miners remained. As the other miners left, two entrepreneurs, William H. Stevens and Alvinus B. Wood, bought up the abandoned mines, having discovered sometime earlier that lead and silver were components of the heavy black sand that had made placer mining difficult. Mining of the lead- and silver-laden carbonate ore began in 1875 with the Rock Mine. The news of this new ore caused another rush of miners to the Leadville area. Photographs of Leadville and California Gulch from this period are presented in Figures 3.1 through 3.3 A number of smelters were built in conjunction with mining of the lead ore. During the period from 1875 to 1880, 44 smelters were built, although some operated for only a short period of time (Blair, 1980). In the late 1880's, as the mines went deeper, flooding became a problem and the water had to be pumped out, increasing the expense of mining. Drainage tunnels were suggested to solve this problem. In 1889, A.A. Blow began developing the Yak Tunnel from California Gulch under Iron Hill. The portal is located about a mile southeast of Leadville. The tunnel provided drainage to the deeper mines, an alternative to hoisting the ores, and ventilation. In 1891, a concentrating mill was constructed outside the portal. In 1894, when the tunnel was 4,000 feet long, it was purchased by the Yak Mining, Mil- ling, and Tunnel Company which also owned a number of mining claims along the tunnel. The tunnel continued to be extended until, in 1904, it was 2 miles long and reached the Ibex No. 4 mine. The tunnel continued to be lengthened, going under Breece Hill and into the upper

3-2 Poor Quality Source Document The following document images have been scanned from the best available source copy. To view the actual hard copy, contact the Superfimd Records Center at 303-312-6473 FIGURE 3.1 VIEW OF LEADVILLE FROM CARBONATE HILL

SOURCE: COLORADO HISTORICAL SOCIETY FIGURE 3.2 CARBONATE HILL

SOURCE: COLORADO HISTORICAL SOCIETY FIGURE 3.3 SMELTERS WITH MINES NEAR LEADVILLE LOOKING WEST

SOURCE: COLORADO HISTORICAL SOCIETY YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION end of Evans Gufch. By 1909, the tunnel reached the Resurrection No. 2 mine and was 3.5 miles long. Another extension was completed in 1912 when the tunnel reached the Diamond mine. The distal end of the tunnel lies 800 feet below the surface, 400 feet northeast of Resurrection No. 2, and is about 4 miles from the portal (Luke, 1978). By mid-1913, an extension of the tunnel branched off into the Big Evans amphitheater area. Other extensions were built draining the Horseshoe mine, Ruby mine, North Mike mine, South Mike mine, Resur- rection No. 1 mine, Black Cloud mine through Irene No. 2, White Cap mine, and Diamond mine (Figure 3.4). Other mines were also drained by the Yak Tunnel through interconnections or through faults, cracks, and fissures in the rock. There are an estimated 65,000 feet of intercon- necting drifts and laterals at the Yak Tunnel level (ASARCO, 1984). In 1917, an undivided one-half interest in the Yak Tunnel was purchased by the American Smelting and Refining Company (ASARCO), which in the 1890' s had also purchased many of the lead smelters in the Rocky Mountain states. Miners paid far dewatering and transportation ser- vices, and also paid a 10 percent royalty on all ore shipped out through the tunnel. Two other major tunnels were built in the area. In 1921, the Leadville Mining Development Company was incorporated to construct the Canterbury Tunnel from Prospect Mountain southeast beneath the Evans Gulch, Fryer Hill, and Stray Horse Gulch area to dewater mines under Fryer Hill and the northern sections of Iron and Carbonate Hills. This project was discontinued in the 1920's after boring 4,000 feet and failing to discover any additional ore bodies. This tunnel contains relatively good quality water and is used today as part of Leadville's municipal water supply. In 1943, construction of the Leadville Mine Drainage Tunnel (Leadville Drain) was begun by the Bureau of Mines.

3-6 DOLLY B. SHAFT .DIAMOND SHAFT NORTH 11,^93 11.302 SCALE ONE INCH EQUALS RES. NO. 2 SHAFT APPROXIMATELY 1315 FEET 11,254

O RES. NO. 1 SHAFT 11,466

IBEX NO. 4 SHAFT 11,580 IBEX 11,58NO. 34 SHAFT

IRENE SHAFT 11.633

MINNIE SHAFT B 10.662 -« A.Y. NO. 3 SHAFT 10,670 A.Y. NO. 1 SHAFT 10,562 FIGURE 3.4 PLAN VIEW OF YAK TUNNEL

SOURCE: ASARCO YAK TUNNEL/CALIFORNIA GOLCH 2/28/86 REMEDIAL INVESTIGATION The ll,299~-f dot-long tunnel, was completed in 1952 with the Mikado lateral extension (URS/The Ken R. White Company, 1974). No attempt to use the tunnel for drainage or access has been made since 1953. Around the turn of the century, zinc became a minable commodity and several businesses were reorganized to mine and process zinc. In 1899, the incorporation of the American Smelting and Refining Company had been finalized. This smelter combine included operations in Utah, Missouri, Illinois, Montana, Nebraska, Texas, and Colorado. Two of the Colorado smelters included the Arkansas Valley Smelting Company and the Bimetallic Smelter (Griswold and Griswold, 1970). Several new mines were started in 1938 when the Newmont Mining Corporation, Hecla Mining Company, and the U.S. Smelting, Refining, and Mining Company purchased interests in the Yak Tunnel properties and formed a joint venture called Resurrection Mining Company. In 1956, a fire destroyed most of the surface facilities of the large Resurrection mine. By 1961, declining zinc and lead prices forced the longest continuing business, the Arkansas Valley Smelter of ASARCO's, to close and the tracks leading to the Yak Tunnel were removed. In the 1960's and 1970's, the Black Cloud mine was started by Res-ASARCO Joint Venture, and a new mill was constructed in Iowa Gulch. During the new mining and milling process of the Black Cloud mine, water was discharged through the Yak Tunnel to California Gulch. In 1983, as a result of an administrative order from the Colorado Department of Health, connections to the Irene Shaft and the laterals of the Black Cloud mine leading to the Yak Tunnel were sealed, so that the mine no longer actively discharged waters to the Yak Tunnel. The value of total production from the Leadville district was on the order of $500 million, from about 24 million tons of ore (U.S. Department of Interior, 1979). This was distributed as follows for the period from 1860 through 1966:

3-8 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Metal "'Value Quantity Silver $135,086,200 240,042,474 ounces = 7,501 tons Zinc $110,131,900 1,570,802,834 pounds = 785,401 tons Lead $107,434,900 2,176,340,160 pounds - 1,088,170 tons Gold $65,712,400 2,985,801 ounces = 93 tons Copper $17,410,400 106,222,634 pounds 53,111 tons 1,934,276 tons A chronological list of major activities in the Leadville raining district can be found in Engineering-Science Appendix A. Historical Water Quality of Yak Tunnel Drainage Water quality data collected by ASARCO on Yak Tunnel discharge is available for selected years beginning in 1946. Few parameters were analyzed in the early years of data collection, and detection limits were not as low as they have become with improved analytical procedures. Ranges of available yearly values for arsenic, cadmium, copper, lead, and zinc are presented in Table 3.1 for the years 1946 through 1984. The higher values in the ranges were usually collected during spring and summer, while the lower values are generally indicative of winter concentrations. Where only one value is given or where the range is small, samples were taken only during one season. Metal concentrations have been fairly constant over the period from 1966 to 1984, although zinc concentrations appear to have declined slightly since 1966. Based on historical data (Table 3.1), the Yak Tunnel has been discharging hazardous metals into California Gulch for at least 40 years and probably since the tunnel was built in the 1890's. These historical data show that EPA drinking water standards were exceeded for cadmium, copper, and lead. EPA aquatic criteria levels were exceeded for copper, cadmium, lead, and zinc. Historical Water Quality of the Leadville Mine Drainage Tunnel The U.S. Bureau of Mines and the U.S. Bureau of Reclamation have records of flow and selected water quality for the Leadville Mine Drainage Tunnel since 1950 (see Table 3.2). A maximum flow of 7.5

3-9 TABLE 3.1 YEARLY CONCENTRATIONS OF HAZARDOUS METALS IN THE YAK TUNNEL DRAINAGE 1946 through 1984 (mg/1) Year Arsenic Cadmium Copper ____Lead______Zinc 1946 — 41 to 315 1947 61 to 294 1948 __ 49 to 237 1966 2.1 29.8 1970 <0 .01 <0.01 0.35 0.01 — 1971 <0.01 to 0. 015 0.01 to 0.2 0.18 to 2.3 <0.01 to 1.9 22.75 to 80 •1972 <0 .01 0.12 to 0.22 0.4 to 1.2 <0.01 to 0.04 38 to 68 1973 <0.01 to 0.01 0.1 to 0.17 0.4 to 1.6 <0.05 to 0.16 20 to 76 1974 <0.01 to 0.04 <0.01 to 0.1 0.5 to 0.7 0.06 22 to 52 .1975 <0.01 to 0.02 0.19 0.21 to 1.6 0.04 to 0.16 64 to 76 1976 — 0.07 to 0.5 0.2 to 1 0.05 27 to 55 1977 — 0.06 to 0.09 0.1 to 0.48 0.1 to 0.5 2.5 to 40 1978 — 0.082 0.38 0.07 43 1979 — 0.1 0.43 0.08 45 .5 1980 — 0.28 2.2 0.08 89 1983 <0.008 0.127 to 0.13 0.47 to 0.88 0.14 to 0.17 53 to 58 -1984 — 0.23 to 0.24 0.97 to 0.98 0.067 to 0.083 53 to 54 Samples were not collected for every year during this period nor in each season, _ Concentrations are for unfiltered (total) samples. TABLE 3.2 YEARLY CONCENTRATIONS OF HAZARDOUS METALS (ZINC) IN THE LEADVILLE DRAINAGE TUNNEL DISCHARGE 1950 THROUGH 1982 Year Flow (cfs) Zinc (mg/1) 1950 3.25 to 4.35 1951 3.0 to 7.5 1952 (tunnel completed) 4.8 to 6.15 1953 4.0 to 4.1 1954 3.2 to 4.1 1955 2.9 to 3.6 1956 3.2 to 4.4 1957 3.65 to 4.9 1958 3.5 to 4.8 1959 4.1 to 4.4 1965 0.5 to 3.0 0.6 to 1.4 1966 1.5 to 3.3 0.4 to 1.0 1967 1.6 to 3.6 0.5 to 1.2 1968 2.5 to 3.6 0.6 to 1.5 1969 2.8 to 3.5 0.6 to 2.0 1970 2.9 to 3.6 1971 2.9 to 3.3 1972 2.8 to 5.3 1973 2.35 to 4.2 1974 2.85 to 3.35 1975 2.8 to 3.85 1976 1.9 to 3.7 1977 3.1 to 3.5 1978 3.0 to 7.4 3.4 to 10.0 1979 1.6 to 7.0 1.2 to 15.6 1980 4.2 to 18.0 1981 2.8 to 7.2 1982 3.2 to 15.4 U.S. Bureau of Mines, unpublished data, Metal concentrations are for unfiltared (total) samples. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION cubic feet pet" second (cfs) occurred during construction in 1951. Since then, discharge was fairly constant at 2 to 4 cfs until 1978. Flow fluctuated considerably in 1978 and 1979, ranging from 7.4 to 1.6 cfs. In 1975, the EPA issued an National Pollutant Discharge Elimina- tion System (NPDES) permit for the Leadville Drainage Tunnel. This permit required the Bureau of Reclamation to bring the tunnel discharge into compliance with effluent limitations established on the basis of metals criteria for aquatic life. Records for 1965 through 1982 show zinc concentrations ranging between 0.4 and 18 milligrams per liter (mg/1). Permitted levels are 0.6 mg/1 zinc. However, the highest zinc levels from the Leadville Drainage Tunnel are an order of magnitude less than the highest zinc levels from the Yak Tunnel. The U.S. Bureau of Reclamation has been studying ways to control drainage from the tunnel and to assess the effects on the upper Arkansas River. In 1979, the Bureau studied the effects of plugging the tunnel and, during the summer of 1985, drilled wells in the tunnel to further study ways to control the discharge. Tailings and Mill History Three tailings ponds (called tailings ponds 1, 2, and 3) are located in the California Gulch drainage immediately upstream of Leadville. One tailings pond (tailings pond 4) is located in Oregon Gulch as shown on Figure 3.5. Tailings have been placed in California Gulch at least since the early 1900's. In 1905, the Rho (or Rowe) magnetic separation mill was erected at the mouth of the Yak Tunnel. This mill replaced the old Yak concentrating mill (Emmons et al., 1927). The Rho Mill operated for several years, including 1905, 1906, and 1907, but was closed in 1911. It is thought that these early milling processes included the construction of tailings ponds where water could be separated from the slimes.

3-12 [ I FIGURE 3.5 LOCATION OF TAILINGS PONDS

LEADVILLE

DENVER -WESTERNAND RIO GRANGE

California Gulch

LEGEND TAILINGS POND 1 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION The deposition of the existing tailings ponds in California Gulch may cover several older tailings ponds and areas that were formerly placer-rained. The Resurrection Mill, which was located below the mouth of the Yak Tunnel, used the flotation process and operated from the late 1930's until approximately 1958 (Kuss, 1986; Stout, 1986). Much of the waste material from tailings ponds 1, 2, and 4 was a result of processing at the Resurrection Mill. The mill started with production at 250 tons per day (Ramsey, 1973). Information on the mill is limited, but based on information from the Resurrection Mining Company files, in 1951, the milling capacity was 750 tons per day, and both lead and zinc concentrates were produced. The last pond to be constructed was tailings pond 4 in Oregon Gulch. An ASARCO map from 1948 shows tailings ponds 1 and 2 labeled "Resurrection Old Tailings Pond" and tailings pond 4 labelled "Resurrection New Tailings Pond." Tailings pond 3 was deposited in California Gulch over placered ground (Kleff, 1948). The first mill constructed at this site was the Harrison Reduction Works which operated from the 1870*s until the early 1900's (Brown, 1986). According to Adolf Sadar (1986), the California Gulch Mill, which operated from 1939 until 1952 or 1953, also deposited waste material In tailings pond 3. This mill processed ore mainly from the Kokorao district and other mining districts outside of the Leadville district by flotation methods. According to Mr. Sadar (1986), 1,000 tons of ore per day were processed during full production. The mill produced lead, zinc, gold, and silver concentrates. Another source (ASARCO, Inc., 1948) called this pond the Leadville Mill Tailings Pond. ASARCO owned tailings pond 3 at least since the 1960's when ASARCO correspondence reflects an effort to sell the pond.

3-14 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

MINING ACTIVITIES The wastes in the California Gulch area are a result of mining, milling, and smelting activities conducted from the end of the 19th century through the middle of the 20th century. This section briefly describes "typical" mining, milling, and smelting processes for metals ores. Knowledge of these processes assists in understanding the chemistry of the waste rock and tailings found at the Yak Tunnel/California Gulch site. A mining and processing schematic is presented in Figure 3.6. Underground Mining In the Leadville mining district, following exhaustion of the placer deposits in California Gulch, ore deposits were mined using underground methods. Access to the ore bodies was obtained by exca- vating horizontal tunnels (adits) or vertical tunnels (shafts). Once an ore body was encountered, additional workings were excavated to remove the ore for processing. In the manto deposits, large caves have been developed underground. Typically, level drifts followed the ore body, level crosscuts connected drifts, and vertical or inclined raises connected different levels of workings. During the access and development of an ore body, the underground workings must be excavated through barren rock formations (well rock) and through noneconomic rock associated with the ore (gangue) in an attempt to locate economically mineable ore deposits. Much of this excavated material is deposited near the mine entrance as waste rock. The material is frequently composed of gangue minerals such as quartz, sericite, chlorite, dolomite, and limestone, but it may also contain pyrite and noneconomic concentrations of other sulfide and carbonate minerals.

3-15 1

1 UNDERGROUND 1 ORE ZONES 1 1 MINE DEWATERING 1 1 ^.v—'^-r'v.i-x^/'• W A S T E" *R OC Kc-'^c'-'- J >-iv 1 1 1 MINERAL PROCESSING METAL 1 CONCENTRATES 1 STACK EMISSION SMELTING 1 PROCESSES 1 PRIMARY METALS 1 TO MARKET KEY: t 1 •'»,-o.• •j'**~'~.^ */ t .r-s- -- *.w/?->".^\r-'.^-c'-.' / .r\:/'•»r' T Wastes Conalciarad In Rl FIGURE 3.6 T MINING/PROCESS SCHEMATIC i. CALIFORNIA GULCH Rl. LEADVILLE. COLORADO YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Milling Processes In addition to the wall rock and gangue minerals deposited in waste piles on the surface, gangue minerals are removed from the mine with the ores. Mineral processing (milling) upgrades the concentration of the desired minerals and rejects the majority of gangue material as waste, known as mill tailings. At the Yak Tunnel/California Gulch site, mill tailings have been deposited in four tailings ponds located in California and Oregon Gulches (Figure 3.5). Typically, ores from mines are transported to central mills (concentrators) where the ores are crushed and ground into small-sized particles to liberate the desired minerals from the gangue minerals. The ground ore is then treated by gravity separation and/or froth flotation. Gravity separation processes rely on the difference in specific gravity of the desired sulfide minerals and precious metals and the lighter gangue, to separate and concentrate desired metals. The ground ore is then treated in jigs or tables to recover the metals values as concentrates. In the froth flotation process, the ground ore (100-200 mesh) is agitated in a tank with finely dispersed air bubbles and various reagents (collectors, activators, depressants). Certain sulfide minerals containing the desired metals attach to the bubbles and are floated to the surface where the foam (concentrate) is collected and then sent to a smelter for further processing. The tailings (gangue material) are then deposited in tailings impoundments (ponds). In the early days, tailings were commonly dumped on the ground or into the nearest stream. Pyrite (FeS-) often contained no desired metal values that could be recovered; so It was suppressed and reported to the tailings as waste.

3-17 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION confined to three dolomite units in the stratigraphic sequence. Of these, the uppermost or Leadville Dolomite is the most productive. Most ore bodies are on the underside of porphyry sills and, particularly, beneath sills that occupy unconformities. Many replacement bodies have vein roots or branch from veins. The veins occupy faults and are productive mainly in the section of quartzites and dolomites and included sills. The primary ores consist principally of pyrite, marma- tltic sphalerite, and galena but locally contain chalco- pyrite, silver minerals, bismuth minerals, and gold. Prin- cipal gangue minerals are manganosiderite and jasperoid. A more complete list of minerals identified in the Leadville district is provided in Engineering-Science Appendix B. Much of the mineralization occurs as sulfide ores. In general, deposition of sulfide ores occurred during late stage degasification of magmas which intruded the quartzite and limestone sediments of the area. These late stage fluids, commonly termed "hydrothermal solutions" contained high concentrations of metals and sulfur. GEOCHEMISTRY Metal Dispersion from Mineralization In a mineralized area, such as the Leadville district, natural weathering processes can potentially release metals to surface and ground waters and to soils. Mining activities accelerate this process and greatly increase the release of metals to the environment. Rose et al. (1979) have estimated that water draining old workings and ore piles may be 10 or even 100 times higher in concentrations of metals than if the deposits had not been mined. A general estimation of metal

3-24 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION dispersion from mineralization may be based upon the type of mineralization and the cross-sectional area of the ore body exposed at the surface. In the Leadville mining district, both sulfide and carbonate ores were mined. As discussed above, sulfide ores are the source of acid waters and a primary source of hazardous metals. The carbonate ores are secondary ores resulting from the oxidation of the primary sulfide ores. The carbonate ores also contain hazardous metals, but these ores are not subject to oxidation and are relatively insoluble. Although the carbonate ores can release hazardous metals, they do so at a much slower rate than sulfide ores. In the Leadville district, with the exception of Iowa Gulch, only the carbonate ores occur at or near the surface. Tweto (1968) indicates that the original ore deposits were oxidized to depths of several hundred feet during the Miocene Epoch (5 million to 24 million years ago). This was apparently a period of pedimentation, graben faulting, and canyon cutting. These events lowered the ground water table and exposed the sulfide mineralization to oxidation. In general, the ground water level limits the depth of oxidation. Ground water levels probably began rising as the Arkansas River valley filled with Pliocene lake sediments (1.8 million to 5 million years ago) and continued to rise as the valley was further filled with glacial deposits in Pleisto- cene time (1.8 million to 10,000 years ago). Once the ground water levels rose above the sulfide mineralization, oxidation essentially ceased. Emmons et al. (1927) indicates that, prior to mining, ground water levels were hundreds of feet above the sulfide mineralization. Sulfide minerals currently occur at the surface, where they are subject to oxidation and bacteriologic activity, primarily as a result of the extensive mining activities in the area. Prior to the extensive

3-25 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION disturbance of the Leadville area by mining starting in the mid-1800's, natural mineralization probably contributed little pollution to the upper Arkansas River and its tributaries. Sulfide Oxidation Processes Sulfide minerals are very stable under reducing conditions, but when they are exposed to oxidizing conditions, they become unstable. In the tunnels and underground mine workings, the sulfides remaining after mining are exposed to oxidizing ground water. The tailings ponds and waste piles are also subject to oxidation by exposure to air and by exposure to oxidizing precipitation, surface runoff, and ground water. The major sulfide mineral in the underground mine workings, tailings, and waste piles is pyrite (FeS,). As pyrite is oxidized, Fe , SO. , and H are formed. The formation of Fe is the rate- determining step for the reaction (Singer and Stumm, 1970; Nordstrom et al., 1979), which is slow without the presence of bacteria. Bacteria have been found to increase the formation of Fe3 + by 5 to 6 orders of magnitude (a 100,000- to 1,000,000-fold increase). The result of this oxidation is an acidic, sulfate-rich water. The oxidation of pyrite and other sulfides also results in the release of metal ions and an increase in the aqueous concentration of the metals. Other sulfides in the contaminant sources are sphalerite and galena, which were the main ore minerals. A complete list of ore minerals from the Leadville district is Included in Engineering-Science Appendix B. Many of the metals found in the tailings ponds, such as arsenic, cadmium, copper, lead, nickel, and zinc, occur in relatively small amounts as a substitute for iron in the pyrite mineral. Cadmium also substitutes for zinc in sphalerite and other zinc minerals (Hem, 1972; Forstner and Wittmann, 1983; Fleischer et al., 1974). Siderite (FeCO,), which is also found in the contaminant sources, is unstable in acidic, oxidizing waters and releases F2e+ . Siderite forms a solid solution between manganese and iron, so manganese is also released.

3-26 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

Metal Dispersion in Surface and Ground Waters Metals occur in surface and ground waters in a variety of forms. According to Rose et al. (1979), the most important mobile phases are: Cations - examples include Zn2 + , Cu2 + , Co2 + , and cationic complexes. Anions - for example, HAs2O- Uncharged ion pairs - for example, PbCO- . Organic complexes - metals can be complexed by organic molecules. If the complex is small, the metal is essentially dissolved, but if it is large and charged, it is colloidal. Suspended colloidal particles - metals may form colloidal oxides or they may be coprecipitated in iron and manganese- oxide particles. Ions adsorbed on suspended matter - suspended matter has a high exchange capacity (small particle size and large surface area). A summary of the major geochemical processes for dissolved metals and solid metal species in surface waters is given in Figure 3.9. Cations, anions, uncharged ion pairs, and adsorbed ions can readily exchange from one form to another in very short periods of time in response to a change in the chemistry of the solution (Rose et al., 1979). Organic complexes and suspended particles tend to react more slowly and may persist over long distances and for long periods of time. Most of the metals in surface waters are carried in non-ionic form, mainly in soluble organic matter and in suspended inorganic and organic particles (Perhac and Whelan, 1972). Ground water, however, carries metals in ionic form with a smaller proportion traveling as colloidal particles and organic complexes (Rose et al., 1979).

3-27 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION A number o-J f — studies have shown that the free metal ion is the toxic species for organisms (Sunda and Guillard, 1976; Gillespie and Vaccaro, 1978). However, in the environment, metal ions can be changed chemically so they are not found in the free state. A change in chemical conditions can cause precipitation or adsorption of the metal ion from flowing surface or ground waters. Perlman (1967) and Rose et al. (1979) have summarized the major types of chemical changes and the elements affected: Oxidation. Oxidation of reducing solutions causes iron and manganese oxides to precipitate. This is usually a result of the emergence of ground water at the surface. Reduction. Reduction of oxidizing water is caused by the water encountering organic matter or mixing with reducing waters. In this case, uranium, vanadium, copper, selenium, and silver can be precipitated as metals or oxides. Sulfide Reduction. Reduction of oxidizing sulfate waters can result in the precipitation of iron, copper, silver, zinc, lead, mercury, nickel, cobalt, arsenic, and molybdenum as sulfides. Increased pH. Metals such as calcium, magnesium, strontium, manganese, iron, copper, zinc, lead, and cadmium are precipitated by increased pH as a result of interaction of acid waters with carbonates or silicate rocks, by mixing with alkaline waters, and/or by mixing with neutral waters in the case of some metals. Adsorption. This refers to the adsorption or coprecipitation of ions on iron and manganese oxides, clays, and organic materials. Cations of transition metals and those with higher valences tend to be more strongly adsorbed than anions and low-valent cations. Increasing the pH increases the adsorption of metal cations. The pH of adsorption increases in the order Pb < Cu < Zn < Cd < Ag and in the order SeO, <

3-28 Metal flux from deposited sediments cCO

2 §o 5 =m5 SHI •O- a-O CO "f'. :m• T» a cCO «:-»-:o2 03 c•oo j o.*3 •a* zm o" mo ipzoO iii . CO C J ••:< o "z = m > 5W B" -II n-: £ H o Mg 03 i i:i5 3 H i:co o* am 1 < •• » * •• * 1 1 om L Metal flux from deposited sediments L YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION CrO '< SeO- < AsO. In otherwise Identical conditions. Thus, lead and copper are more strongly bound to these surfaces than zinc and cadmium. In normal pH conditions of surface waters, silica, clay minerals, feldspars, and manganese oxides are negatively charged and can exhibit a stronger affinity for sorption of positively charged metal cations than amorphous iron oxyhydrates or alumina. The processes described above can be caused by waters of one type intermixing with other waters, interaction of waters with solids (sediments or rocks), or the loss or addition of gases when ground waters emerge at the surface (Rose et al., 1979). For example, in seepage or spring areas, ground waters emerging at the surface become oxidized. The Fe 2+ carried by the water Is oxidized to ferric Iron and precipitates as limonite. Other metals can be coprecipitated with the limonite or with the organic matter accumulating within the seepage or spring area. Metals can also be precipitated in areas where acid waters emerge from the reducing environment of a wetland and flow Into an oxidizing environment of an open stream channel (Rose et al., 1979). Again, precipitation of hydrous iron and manganese oxides occurs in the stream bed, in which metals can be coprecipitated. Mixing of waters of two confluent streams which have very different chemistries can also result in precipitation of hydrous iron and manganese oxides together with associated trace metals immediately below the confluence. Because ground water has a lower content of free oxygen and less biological activity than surface waters, the precipitation processes discussed above have lesser effects. However, there are examples of precipitation of metals from ground water as it moves into more chemically reactive environments, such as zones of secondary enrichment in copper deposits and the formation of uranium roll-type deposits.

3-30 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION A summary of the mobility of some elements in surficial environments is shown in Table 3.3. This table is based on information on coefficients of aqueous migration and practical experience in exploration geochemistry (Rose et al., 1979). In wetlands and other organic- rich environments, conditions will be reducing; in normal surface weathering conditions, the environment will be oxidizing with pH 5 to 8. Near oxidizing sulfides, the environment will also be oxidizing with pH less than 4. Metals in Soils The most important constituents of soils that contribute to the aquatic cycling of trace metals are colloidal inorganic particles and organic matter. The colloidal fraction, which is less than 0.2 microns in diameter, contains clays and hydrous oxides. Clays function as cation exchangers while hydrous oxides have limited ion-exchange properties and also act as adsorbents for metals (Bowen, 1979). Some types of clay minerals fix and adsorb anions and cations more than others (Overcash and Pal, 1979). Hydrous iron oxides strongly adsorb arsenic, chromium, molybdenum, selenium, and vanadium in acid soils and hydrous manganese oxides carry most of the cobalt together with some barium, nickel, and lanthanides (Brady, 1974; Bowen, 1979). In alkaline soil, calcium phosphate adsorbs arsenic, barium, cadmium, iron, lead, and other elements. The cation exchange capacity of organic soils is largely due to organic matter. It appears that the pH-dependent exchange capacity of the mineral phase results from the dissociation of hydrogen ions (H ) from structural elements at the crystalline edges of aluminosilicate minerals (Aubert and Pinta, 1977). Soil organic matter is composed of mainly polymeric weak acids of the type of humic and fulvic acids (Salomons and Forstner, 1984). Studies by Bowen (1979) show that .2+ Cu, Pb, and Sn2+ are exceptionally tightly bound by humates, while M2+n and the alkali and alkaline earth metals are most loosely bound. In

3-31 TABLE 3.3 ,/ MOBILITY OF SOME ELEMENTS IN SURFICIAL ENVIRONMENTS ' Relative Mobility Oxidizing Oxidizing Reducing (pH 5-8) (pH<4) Highly Mobile 9 ' Moderately Mobile Zn, Ag, As Zn, Cd, Cu, Ag, Mn (K=l-10) (Hg, Sb?) Go, Ni, As, Mn Slightly Mobile Mn, Pb, Cu, Fe3' (K-0.1-1) Ni Immobile Fe Fe, As 4/ , Se 4/' Fe, Cu, Ag, Pb, (K<0.1) Zn, Cd, Hg, Ni, As, Sb, Se, Cr Modified from Rose et al. (1979) after Perl'man (1967). 2/ K is an indication of mobility; the content of an element in fresh water relative to content in its associated rock. Intermediate oxidation potential. 4/ In presence of iron oxides. RESURRECTION MILL YARD

EXPLANATION SEDIMENTARY ROCKS CARBONIFEROUS OROOVICIAN Leadvllle ("Blue") limestone Parting quartzlte member (pg) Whlte"llmestone member (wl) PRE - CAMBRIAN Qranlte.gne'.ss.i schist INTRUSIVE IGNEOUS ROCKS \ ATE CRETACEOUS OR EARLY TERTIARY

agglomeratRhyollte e FIGURE 3.8 BEDROCK GEOLOGY MAP 0 500 1000 Scil* In feet YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION some cases, M'?•+n • can increase 30 percent in solubility at the 50 percent organic matter level (Overcash and Pal, 1979). Other processes, such as bonding between a metal and chelating ligand, can result in the formation of soluble complexes. These complexes, made more readily mobile through the soil profile, may become more plant-available (Overcash and Pal, 1979).

3-33 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION CHAPTER 4 MINING WASTE INVESTIGATION Two major types of mining waste, tailings and waste rock, have been identified at the Yak Tunnel/California Gulch site. This material is the source of several hazardous substances, as defined under CERCLA, found at the site. Arsenic, cadmium, copper, lead, mercury, nickel, selenium, silver, and zinc are present in all four tailings ponds. Most of the waste rock piles contain high concentrations of arsenic, cadmium, copper, lead, nickel, and zinc. Hazardous metals are transported from the waste rock piles and tailings ponds as windborne dust and as sediment transported by surface water. In addition, cadmium, copper, lead, nickel, and zinc are leached from the mining waste during snowmelt and other precipitation events, contributing to the contamination of surface and ground water at the site. TAILINGS PONDS Four tailings ponds covering a combined area of 44.8 acres (Colorado Mined Land Reclamation Division, 1986) are located at the Yak Tunnel/California Gulch site (Figure 4.1). Three tailings ponds, called tailings ponds 1, 2, and 3, are in the California Gulch drainage immediately upstream of Leadville. California Gulch passes through a portion of tailings pond 3, which has been estimated by Apache Energy and Minerals to contain approximately 936,000 tons of material. The stream was diverted around tailings ponds 1 and 2 in 1984. Tailings pond 4 is located in the headwaters of Oregon Gulch. Tailings are also deposited in Multa Gulch; however, they were not included in these inve s tiga tions. Runoff and seepage from the tailings ponds affect water quality in California Gulch during snowmelt and other precipitation events. Direct precipitation and water collected in the tailings ponds seep

4-1 I I FIGURE 4.1 WASTE PILE AND SOIL/SEDIMENT SAMPLE LOCATIONS STRAY HORSE AND CALIFORNIA GULCHES

Stray Horse Qulch 12

Oregon Gulch Pigtail Qulch

California Qulch

LEQEND • SOIL/SEDIMENT SAMPLES ES-1A ENGINEERING-SCIENCE DRILL HOLE • WASTE PILE SAMPLES NORTH NOTE: ALL SAMPLES LOCATED IN STRAY HOHSE QULCH ARE NOTED ON TABLE 4.3 AS "SHQ", AND THOSE OF CALIFORNIA QULCH AS "CO! SCALE 1:24,000 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION through the tailings and enter the surface or ground water systems. This water reacts with the sulfide minerals in the tailings and becomes acidic and concentrated in metals. Surface runoff erodes the tailings ponds and transports contaminated sediment downstream. Investigations of the tailings ponds have been conducted by Engineering-Science for the State of Colorado, by the EPA, and by [Dames & Moore for ASARCOJ To define stability and chemistry of tailings pond 3, Engineering-Science auger drilled two test holes at the locations shown in Figure 4.1. Both borings were 30 feet deep and did not penetrate into the alluvium underlying the ponds. Samples were collected at 5-foot intervals. Based on visual observation of samples from the two Engineering- Science drill holes at tailings pond 3, the tailings mineralogy includes pyrite, quartz, and siderite. Apache Energy and Minerals, Inc. has determined from channel sampling that the average pyrite content is 24.6 percent. The size gradations and moisture content of several samples from the Engineering-Science drill holes were determined. Based on one sample from ES-1 at 9 to 10 feet, the size distribution was 60 percent sand and 40 percent silt. The data from ES-2 is listed below: 9-10 feet - 13 percent sand, 87 percent silt 19-20 feet - 58 percent sand, 42 percent mixture of silt and clay 24-25 feet - 56 percent sand, 44 percent clay Moisture content of ES-1 at 9 to 10 feet was 13 percent. The average moisture content for the three samples listed above from ES-2 is 20 percent. Samples from drill hole ES-1 were composited by Engineering- Science for chemical analysis. The results of these chemical analyses (Table 4.1) show that tailings pond 3 contains several hazardous substances, including arsenic, cadmium, copper, lead, nickel, silver, 4-3 TABLE 4.1 CHEMICAL ANALYSES OF CALIFORNIA GULCH TAILINGS POND 3 (ENGINEERING-SCIENCE DATA) Total Recoverable Snow Leachate Acid Leachate EP Toxicity Metals mg/kg mg/1 mg/1 mg/1 Antimony 34 ND ND Arsenic 450 ND ND ND Barium 0.012 Cadmium 41 0.116 0.048 0.33 Chromium ND ND ND ND Cobalt 15 0.025 0.005 Copper 890 0.012 0.026 Iron 153,000 ND ND Lead 2,390 0.09 ND 4.48 Manganese 3,350 36.9 11.3 Mercury ND Molybdenum 5 ND ND Nickel 8 0.03 0.02 Selenium ND Silver 23 ND ND ND Zinc 5,480 10.4 3.39 — Analysis not run ND Not detected YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION and zinc. The results of agitation leach tests indicate that cadmium, copper, lead, nickel, and zinc would be leached from the tailings pond during snowmelt and other precipitation events. The results of EP- Toxicity tests for the composite sample from tailings pond 3 were below the maximum concentrations set by RCRA. However, the EP-Toxicity test reproduces a landfill environment and is not indicative of the geochemical environment of the tailings ponds. The slope stability analysis conducted on the tailings pond profiles at the locations of test holes ES-1 and ES-2 used a computer program based on the Modified Bishop Method of Slices (see Engineering- Science Appendix B). The calculated factor of safety is 1.4 for the ES-1 profile, and 1.6 for the ES-2 profile. These factors indicate that the stability of the tailings dam is questionable. (A factor of 1.5 is considered to be a minimum for dams.) The stability is further suspect based on the steepness of the side slopes (1.2:1 versus a maximum recommended slope of 1.3:1). In addition, liquifaction and failure during an earthquake could be expected, as could overtopping and erosion during a major flood event. The EPA also collected tailings samples for geochemical analysis. The samples were augered to 7 feet from the surface of each pond and analyzed for total metals and key anions. A compilation of the geochemical data (Table 4.2) shows that hazardous substances, including arsenic, cadmium, copper, lead, mercury, nickel, selenium, silver, and zinc are present in all four tailings ponds. In addition, thallium occurs in tailings ponds 1, 3, and 4, and beryllium occurs in tailings pond 3. The tailings samples show pH values ranging from 5.2 to 6.7 and high total sulfur and sulfate contents. Again, the results of EP-Toxicity analyses for most metals (Table 4.3) fell below maximum concentrations (40 CFR 261.24). Only the cadmium concentrations from tailings pond 1 exceeded these maximum concentrations.

4-5 TABLE 4.2 ANALYSIS OF TAILINGS SAMPLES FROM LEADVILLE, COLORADO (EPA Data) Parameter as Dg/kg Tailings Pond 1 Tailings Pond 2 Tailings Pond 3 Tailings Pond 4 unless indicated As Rec'd Dry As Rec'd Dry As Rec'd Dry As Rec'd Dry Aluminum, Al . / 225 258 252 296 534 578 242 303 Chromium, total Cr 2.91 4.49 4.10 4.82 • 1.63 1.76 1.59 1.99 Barium, Ba 2.15 2.47 1.80 2.12 1.96 2.12 2.65 3.32 Beryllium, Be <0.2 <0.2 <0.2 <0.2 0.2 0.2 <0.2 <0.2 Cadmium, Cd 90.0 103 29.2 34.3 18.6 20.1 34.4 43.1 Cobalt, Co 4.31 4.94 5.41 6.36 5.09 5.51 6.12 7.68 Copper, Cu .. 354 406 254 298 166 180 460 577 Iron, total Fe 1.55 % 2/ ' 1.78Z 2.16Z 2.54Z 8,680 9,390 2,630 3,300 Lead, Pb 5.28 6.06 12.9 15.2 2.16 2.34 29.4 36.9 Nickel, Nl 7.24 8.31 7.70 9.05 8.81 9.53 8.93 11.2 Manganese, Mn 5,560 6,380 4,320 5,080 2,580 2,790 1.14Z 1.43% Zinc, Zn 9,350 1.07Z 3,800 4,470 2,500 2,700 5,720 7,180 Boron, B 78 89 <16 <19 <20 <21 <17 <21 Vanadium, V <2 <2 <2 <2 <2 <2 <2 <2 Calcium, Ca 9,350 1.07Z 7,960 9,360 1.31Z 1.42Z 2.05Z 2.57* Magnesium, Mg 6,540 7,500 4,420 5,200 4,660 5,040 9,750 1.22Z Sodium, Na 3.33 3.82 2.46 2.89 3.52 3.81 4.14 5.19 Potassium, K 1.17 1.34 1.47 1.73 <1.0 4.0 <0.83 <1.00 Arsenic, As 54.8 62.9 59.0 69.4 1.96 2.12 18.2 22.9 Antimony, Sb 15.7 18.0 11.5 13.5 9.8 10.6 14.9 18.7 Selenium, Se 0.29 0.33 0.18 0.21 0.14 0.15 0.25 0.31 Thallium, Tl 1.9 2.2 <0.2 <0.2 3.9 4.2 1.6 2.0 Mercury, llg 0.090 0.100 0.135 0.159 0.048 0.052 0.070 0.088 Tin, Sn <20 <23 ' <16 <19 <20 <21 <17 <21 Silver, Ag 0.20 0.23 0.16 0.19 0.30 0.22 0.33 0.41 Cyanide, total CN <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 Sulfur, total S 3,770 - 5,890 - 2,960 - 3,060 - pll, standard units 5.8 - 5.7 - 6.7 - 5.2 - Moisture, Z 12.8 - 15.0 - 7.6 - 20.3 - Sulfate, SO,, Soluble 8,540 - 9,120 - 6,200 - 7,780 - Chloride, CI 1,070 - 978 - 227 - 751 - II Total represents all metal species. 2/ Levels above 10,000 mg/kg are expressed as percent (10,000 rag/kg - 1 percent). TABLE 4.3 SOILS AND TAILING EP-TOXICITY DATA I/ (EPA DATA) Maximum Concentration Tailings Tailings Tailings Tailings SW-12 SU-12 of Contaminants for Parameter Pond Pond Pond Pond Soil Soil/Clay Characteristic of as mg/1 11 12 13 04 Oxidized Layers ____EP Toxlclty Arsenic, As <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 5.0 Barium, Ba 0.07 0.07 0.06 0.06 <0.05 <0.05 100.0 Cadmium, Cd , 1.68 0.640 0.043 0.026 0.068 0.0007 1.0 Chromium, total Cr <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 5.0 Lead, Pb 1.80 0.42 <0.005 1.20 9.20 0.031 5.0 Mercury, Hg <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 0.2 Selenium, Se <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 1.0 Stiver, Ag <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.02 II Samples were analyzed on an as-received basis according to the RCRA guidelines concerning the extraction procedure for toxlclty (EP-TOX). All test are performed In accordance with current Environmental Protection Agency guidelines as published In the Federal Register. Total represents all chromium species. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION ASARCO has conducted chemical analyses on samples collected from tailings ponds 1, 2, and 4 (Engineering-Science Appendix B). The results of EP-Toxicity analyses shows that cadmium and lead concentrations in some samples collected from the ponds exceed the maximum contaminant levels. ASARCO also conducted snow leach tests on selected samples (Engineering-Science Appendix B) which indicate the ability of snowmelt to mobilize cadmium and lead. Dames & Moore has conducted a slope stability analysis for ASARCO on tailings ponds 1, 3, and 4, but the results of this analysis have not yet been made available.

WASTE PILES A sampling program to investigate contamination from the numerous waste piles in Calfornia Gulch and Stray Horse Gulch was conducted during December 1985, and January 1986. Waste piles were selected for sampling based on their potential to affect surface water systems. Samples were collected by use of a 4-inch bucket auger and/or by digging with a rock pick at three points within a waste pile. Each sample analyzed was a composite of three subsamples collected within a 5-foot radius of the sample point at equal radial and angular distances. At each sampling point, material was collected from 0 to 6 inches, and, if possible, from 12 to 24 inches and was designated as "S" (surface) and "SS" (subsurface), respectively. California Gulch A combined area consisting of approximately 50 acres (as determined from aerial photographs) in California Gulch contains waste piles, including mine dumps, slag heaps, tailings and placer tailings. Locations of the piles sampled are shown on Figure 4.1. Runoff and seepage from the disturbed areas containing the waste piles affects water quality, especially during snowmelt. Many of the

4-8 •"'" YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION waste piles show evidence of erosion, including sheet, rill, and gully erosion. Surface runoff has transported the finer sediment from the waste piles and deposited it downstream. The waste material consists of a wide range of materials, including pyrite and other sulfides, altered igneous rocks, and sedimentary rocks, including dolomite and quartzite (Engineering-Science Appendix B). Total sulfide content ranges up to 7.5 percent. Sizes of the materials range from clay to coarse gravel. Chemistry and other physical characteristics for the waste piles in California Gulch are summarized in Table 4.4. Complete chemical information is given in Engineering-Science Appendix B. High total concentrations of arsenic, cadmium, copper, lead, manganese, nickel, and zinc were detected in most of the waste piles. Based on these analyses, all of the waste piles sampled contain concentrations of metals that may be toxic to plants (U.S. Environmental Protection Agency, 1983). Although manganese is not considered to be hazardous under CERCLA, it has a deleterious effect on plant life. Based on extraction analyses for plant-available metals, manganese occurs at levels considered to be phytotoxic to plants (U.S. Environmental Protection Agency, 1983). Visual observation during sampling indicated that in many cases little vegetation grows upon or adjacent to the waste piles. Acid extractable tests were conducted on the samples to determine the potential for release of metals in the waste piles to surface and ground waters. Based on these tests, most of the piles could release hazardous metals, including cadmium, copper, lead, manganese, nickel, or zinc, to ground and surface waters (Engineering-Science Appendix B). In general, zinc and manganese were more readily extracted than the other metals.

4-9 TABLE 4.4 SUMMARY OF WASTE PILE GEOCHEMISTRY AND OTHER PARAMETERS, CALIFORNIA GULCH AND STRAY HORSE GULCH (ENGINEERING-SCIENCE DATA)

Arsenic Cadmium Copper Lead Manganese Zinc pll plant- plant- plant- plant- plant- plant- total available total available total available total available total available total available Location ag/kg mg/1 mg/kg mg/1 ag/kg rog/1 nig/kg ng/1 ng/kg mg/1 ng/kg mg/1 California Gulch CG-l-S 43* <3.0 9.2* 4.76* 75.7* 17.44 915 151.6 1,290* 122.4 962* 252 5.89 CG-3-S 68* 0.0 7* 0.52 97* 4.84 2,250* 119.2 3,470* 11.96 1,730* 55.0 9.28 CG-4-S 59* <3.0 12* 1.22 39 1.872 1,490* 92.4 11,200* 15.56 2,450* 150 7.79 CG-5-S 520* <3.0 73* 5.14* 108* 2.36 4,780* 136.2 53,400* 7.06 7,960* 284 8.91 CG-5-SS 354* <3.0 62.8* 5.06* 85.6* 1.492 2,590* 115.6 44,700* 0.514 5,230* 256 7.66 CG-6-S 140* 3.8 98* 8.24* 63 1.616 1,360* 8.08 7,720* 0.310 13,200* 452 9.08 CG-7-S 69* 0.0 15.4* 5.56* 137* 3.68 9,220* 163.8 1,630* 47.0 2,190* 338* 3.67 CG-8-S 173* O.O 25* 6.96* 124* 3.46 7,770* 3.94 958* 1.230 4,740* 482* 5.28 CG-9-S 1,220* O.O 73* 5.26* 622* 5.68 25,700* 59.6 434 11.18 8,790* 366* 2.57 CG-ll-S 36* O.O 10.7* 4.12* 96.6* 16.02 502 37.0 427 . 29.8 752* 179.8 6 CG-12-S-A 38* O.O 2.8* 0.076 162* 15.78 275 0.62 19 3.98 99.7 3.68 3.43 CG-12-S-B 36* O.O 2.1 0.064 154* 13.70 237 1.14 17.8 2.46 109 4.44 3.44 CG-14-S-A 25* O.O 2.2 0.304 79* 3.94 59 2.14 31.1 11.76 143 23.8 4.24 CG-14-S-B 25* O.O 2.3 0.282 79* 4 66 1.46 • 18 10.68 116 21.0 4.08 Stray Horse Gulch SHG-1-S-A 340* O.O 57.5* 8.32* 1,460* 70.4* 12,100* 11.48 3,410* 3.16 9,910* 414* 5.24 SIIG-1-S-B 340* O.O 57.8* 7.68* 1,440* 75.6* 11,900* 6.08 3,890* 1.884 10,400* 340* 4.68 SHG-1-SS-A 210* O.O 172* 8.56* 1,240* 96.6* 14,900* 40 6,770* 2.94 16,000* 432* 5.8 SIIG-1-SS-B 210* • O.O 160* 10.92* 1,290* 141.0* 12,900* 16.4 6,590* 3.6 15,200* 442* 4.95 SHG-2-S 240* O.O 93.5* 5.90* 172* 2.44 7,460* 164.8 39,000* 0.16 11,100* 330* 6.56 SHG-2-SS 260* O.O 402* 13.90* 324* 0.836 8,530* 0.62 142,000* 0.12 75,800* 414* 6.81 SHG-3-S 370* O.O 189* 9.52* 1,050* 48.2 11,800* 6.2 12,400* 0.636 22,700* 420* 5.72 SHG-4-S 380* O.O 44* 0.986 261* 2.12 12,900* 358 7,280* 3.72 9,070* 121.2 6.2 SHG-5-S 140* O.O 203* 0.984 702* 68.2 13,800* 12.72 1,780* 1.302 44,200* 712* 5.63 SHG-6-S 89* O.O 252* 0.48 396* 18.06 10,200* 3.44 5,340* 0.798 40,200* 602* 5.48 SHG-6-SS 120* O.O 226* 0.862 614* 36.8 13,700* 3.76 1,950* 1.312 35,700* 518* 5.17 SHG-7-S 350* O.O 70* 1.658 1,200* 0.426 13,400* 14. 0* 434 72 7,550* 248 2.7 SHG-8-S 170* O.O 9.4* 0.648 192* 2.84 2,610* 52.2 528* 218 392* 44.4 3.06 SHG-8-SS 450* O.O 28* 6.44* 361* 4.64 9,240* 3.16 603* 102.2 2,460* 276 2.83 SHG-9-S 172* O.O 20.6* 2.58* 453* 10.52 15,800* 284 371 88.6 2,080* 136.8 3.28 SHG-10-S 43* O.O 6.1* 0.970 47.4 0.92 408 22.6 2,360* 10.24 836* 42 6.56 SHG-10-SS 44* O.O 5.1* 1.974 63 11.62 865 178.8 649* 79.6 588* 74.4 5.26 SIIG-11-S 53* O.O 7.4* 3.78* 76.7* 4.94 572 146.4 596* 114 609* 222 5.09 SHG-14-S 64* O.O 3.3* 0.116 272* 17.02 335 5.48 281 38 145 7.24 4.84 SHG-15-S 929* <5.8 13* 0.524 502* 30.6 6,750* 314 221 26.8 296 14.16 6.05 SHG-16-S 594* O.O 11* 0.386 719* 36.4 938 19.4 461 13.2 161 11.74 3.48 SHG-20-S 270* 0.0 129* 3.2* 1,210* <0.12 5,260* <1.0 8,440* 2,540* 8,800* 1,314* 2.55 SHG-20-SS 280* 0.0 86* 0.52 1,200* 15.56 5,720* <5.0 7,360* 274 12,200* 804* 2.88 Concentration potentially toxic to plants based on total soil metals levels (see Table 8.1). •"'" YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Stray Horse Gulch Approximately 100 acres (as determined from aerial photography) In Stray Horse Gulch contain waste piles, including mine dumps, tailings, and prospect pits. Locations of the waste piles sampled are shown on Figure 4.1. Surface water runoff and ground water seepage from the waste piles probably affects the water quality in Stray Horse Gulch, particularly during the spring snowmelt. Sheet, rill, and gully erosion were observed on the piles. Compared to Upper California Gulch, waste piles in Stray Horse Gulch have more surface area exposed so that during precipitation, water has more contact with waste piles, contaminated soils, and sediment. The uncontrolled flow of surface water through the waste materials has resulted in the breaching of culverts, berms, and dikes. Stray Horse Gulch drains into Starr Ditch, which flows through residential areas of Leadville and enters California Gulch below the tailings ponds (Figure 4.1). The material sampled in Stray Horse Gulch was similar to that found in California Gulch (Engineering-Science Appendix B). It included pyrite and other sulfldes, altered Igneous rocks, and sedimentary rocks. Total sulfide content ranged up to 22 percent. The size of the material ranged from clays to coarse gravel. The chemistry and physical characteristics of the waste piles are summarized in Table 4.4. High total concentrations of arsenic, cadmium, copper, lead, manganese, nickel, and zinc were found in most of the waste piles. Based on extraction analyses for plant-available metals (Table 4.4), manganese, cadmium, and zinc occur at levels considered phytotoxic to plants (U.S. Environmental Protection Agency, 1983) in several of the waste piles. Visual observation indicated that in most cases little vegetation occurs on or adjacent to the waste piles. Samples were tested for acid extractable metals to determine the potential for the release of metals in the waste piles to surface and

4-11 ""• YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION ground waters. The results show that many of the piles release metals, including cadmium, copper, lead, manganese, nickel, or zinc, to ground and surface waters based on the acid extractable results (Engineering- Science Appendix B). Generally, zinc and manganese are the most readily released metals. The waste piles are slightly acidic to highly acidic (pH 2.55 to 6.81). Acid-base potential data (Engineering-Science Appendix B) shows that sample sites SHG-5-S, SHG-6-SS, SHG-7-S, SHG-8-S, SHG-8-SS, SHG-9-S, SHG-16-S, SHG-17-S, SHG-20-S, and SHG-20-SS have acid producing potential. The highest hazardous metal concentrations occur in an area in the lower portion of Stray Horse Gulch that encompasses sampling sites SHG-1, SHG-2, SHG-3, SHG-4, SHG-5, SHG-6, SHG-7, SHG-8, and SHG-20. This area of approximately 16 acres (Colorado Mined Land Reclamation Division, 1986) contains numerous large mine dumps and is located immediately east of Leadville. It may contribute to windblown contamination discussed in Chapter 10. Sand dunes of depths up to 3 feet occur in this area. Runoff from this area drains into Starr Ditch which flows through residential areas of Leadville. Flow in Starr Ditch contains EP Toxic concentrations of cadmium. CONTAMINATED SOILS AND SEDIMENT Soils and sediment in California and Stray Horse Gulches were sampled to determine the effects of runoff from the waste piles. Figure 4.1 shows the sample locations for these materials. In California Gulch, samples CG-2-S, CG-10-S, and CG-13-S were collected from the drainage channel, which consists of fine to coarse sands and some gravel. In Stray Horse Gulch, samples were taken from the 20-acre (Colorado Mined Land Reclamation Division, 1986) Adelaide Park wetland (samples SHG-12-S, SHG-12-SS, SHG-13-S, and SHG-13-SS);

4-12 " -"" YAK TUNNEL/CALIFORNIA GDLCH 02/28/86 REMEDIAL INVESTIGATION from Stray Horse Gulch sediment (SHG-19-S); and from Starr Ditch sediment (SHG-17-S and SHG-18-S). The wetland samples at 0 to 6 inches were organic-rich clay and sand, and from 12 to 24 inches were lirao- nitic- (iron oxide) stained clay, silt, sand, and gravel. The sediment in Starr Ditch was sand that had been stained reddish-brown by iron oxides. High total metal concentrations of arsenic, cadmium, copper, lead, manganese, nickel, and zinc were found in most of the samples collected in California and Stray Horse Gulches (Table 4.5). The sediment samples from Stray Horse Gulch and Starr Ditch contained the highest concentrations of metals. Metals such as arsenic, cadmium, copper, lead, manganese, and zinc were found in the same ranges of concentration as were found in the mine dumps in the lower portion of Stray Horse Gulch. This indicates that the mine dumps are the likely source of contaminated sediment. The wetland samples from Stray Horse Gulch were high in metal contents but were lower than the sediment samples. Plant-available concentrations for several metals well above phytotoxic and EPA guidelines for soils metals-loading rates occurred at all soil/sediment sampling locations in both Stray Horse and California Gulchs. See Section 8, Soils Investigation for information on EPA guidelines and phytotoxic levels of metals in soils. Metals occurring at plant- available levels capable of producing phytotoxic effects are cadmium, copper, lead, manganese, and zinc. Samples were also tested for acid extractable metals to determine the potential for the release of metals from the soils or sediment to surface and ground water. The wetlands and sediments in Stray Horse Gulch are releasing cadmium (except SHG-17), copper, lead, manganese, and zinc to ground and surface waters based on the acid extractable

4-13 TABLE 4.5 SUMMARY OF GEOCHEMISTRY AND OTHER PARAMETERS FOR SOILS AND SEDIMENTS IN CALIFORNIA GULCH AND STRAY HORSE GULCH (ENGINEERING-SCIENCE DATA) Arsenic Copper Manganese Zinc plant- —————Cadmiupi t- m plant- Lea~ dplant- plant- plant- total available total anavailable total available total available total available total available Locationmg/kg rog/1 mg/kg mg/1 mg/kg ing/l mg/kg mg/1 «g/kg mg/1 rog/kg ag/1 California Gulch CG-2-S 250 <3.0 30.2* 11.38* 400* 2.94 22,800* 1.66 897* 19.12 5,360* 404* 3.23 CG-10-S 52 <3.0 3.4* 0.246 239* 27.0 813 49.0 639* 46.4 461* 33.6 4.47 CG-13-S 70 <3.0 4.6* 0.954 278* 56.6 1,920* 141.6 396 66.4 618 78.8 4.07 Stray Horse Gulch SG-12-S-A 77 — 6.8* — 125* — 2,980* — 883* — 755* — 5.68 SG-12-S-B 41.2 — 5.02* — 94.6* — 2,060* — 1,160* — 540* — 5.66 SG-12-SS-A 44 <3.0 2.1 0.340 59.7 4.8 339 84.8 585 52 98.8 16.44 4.51 SC-12-SS-B 43 <3.0 2.1 0.306 64.4 4.48 341 84.6 598 68.8 89.3 13.54 4.68 SG-13-S 63.2 — 10.6* — 257* — 2,440* — 1,890* — 910* — 6.88 SG-13-SS 146 <3.0 6.8* 2.14 510* 113.4* 5,040* 550 496 62.8 780* 84 6.04 SG-17-S 300 <3.0 55* 2.16 1,100* 53.8 9,800* 478 7,970* 34.6 9,230* 160.8 5.78 SG-18-S 170 <3.0 62* 5.52* 871* 100.4* 7,380* 128 10,600* 10.66 8,860* 272 6.59 SG-19-S 227 <3.0 83* 7.94* 607* 19.82 13,000* 4 3,950* 1.584 13,900* 478* 5.66 * Concentration potentially toxic to plants based on total soil metals levels (See Table 8.1). " •-•"- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION results (Engineering-Science Appendix B). Zinc and manganese are the most readily released metals in the sediment, while lead and manganese are more readily released in the wetland samples. Acidity of the soils and sediments ranged from slightly to strongly acidic (pH 6.88 to 3.23). Acid conditions tend to favor heavy metals uptake by plants (U.S. Environmental Protection Agency, 1983), as do the reducing environment and high levels of organic matter in the wetland in Stray Horse Gulch. Low pH in California Gulch sediments would also lead to increased mobility of metals, which could increase their potential for being transported downstream. EPA collected two soil samples at the site of the lower flume (SW-12) in California Gulch (see Figure 6.3 in Chapter 6). These samples were collected from material excavated from the installation of the flume. Much of this material probably was tailings and other types of mining waste that had been transported as sediment. The results of geochemical analyses (Table 4.6) show that these samples contain the hazardous substances arsenic, copper, lead, mercury, nickel, silver and zinc. In addition, the samples described as "soil/clay layers" contained antimony, beryllium, and selenium. The lead concentration in the soil sample described as "oxidized" was high, and exceeded the EP-Toxicity concentration of 5.0 mg/1.

4-15 TABLE 4.6 ANALYSES OF SOILS SAMPLES FROM LOWER FLUME SITE NEAR LEADVILLE, COLORADO (EPA Data) SW-12 SW-12 Soil Soil/Clay Parameter ___Oxidized______Layers______as mg/kg As Rec'd Dry As Rec'd Dry Aluminum, Al 1,680 1,920 9,590 1.40%lyf Chromium, tota l Cr 7/ ' 3.55 4.05 20.9 30.6 Barium, Ba 154 176 78.3 115 Beryllium, Be <0.2 <0.2 1.26 1.85 Cadmium, Cd 9.89 11.3 0.088 0.129 Cobalt, Co 2.17 2.48 4.92 7.21 Copper, Cu z/ 52.6 60.2 8.08 11.8 Iron, total Fe 9 / 1.36% 1.55% 6,550 9,600 Lead, Pb 1,790 2,040 15.9 23.3 Nickel, Ni 2.37 2.71 8.21 12.0 Manganese, Mn 1,030 1,180 454 665 Zinc, Zn 1,550 1,770 351 514 Boron, B 39 44 12.6 18.5 Vanadium, V 3.9 4.4 26.5 38.8 Calcium, Ca 456 521 2,310 3,390 Magnesium, Mg 266 304 2,640 3,870 Sodium, Na 26.4 30.2 15.1 22.1 Potassium, K 185 211 258 378 Arsenic, As 18.4 21.0 4.17 6.11 Antimony, Sb <10 <11 6.3 9.2 Selenium, Se <1.10 <1.10 0.10 0.15 Thallium, Tl <2 <2 <1 <2 Mercury, Hg 4.21 4.81 0.660 0.967 Tin, Sn <20 <23 <13 <19 Silver, Ag 5.73 6.55 0.13 0.19 Cyanide, total CN <0.02 <0.02 <0.02 <0.02 Sulfur, total S 2,260 - 1,200 pH 3.9 - 5.0 Moisture, % 12.5 - 31.8 Sulfate, SO,, Soluble 6,580 - 2,620 Chloride, Cl 696 - 2,680 Levels above 10,000 mg/kg are expressed as percent (10,000 mg/kg = 1 percent). 21 Total represents all metal species. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION CHAPTER 5 GROUND WATER INVESTIGATION At the Yak Tunnel/California Gulch site, the uppermost aquifer is comprised of valley fill with a shallow, less transmissable zone from the surface to about 50 feet and a deeper, more transmissable zone from about 50 feet to bedrock. Recharge from contaminated surface water in California Gulch and seepage from tailings ponds in the area have contaminated the shallow aquifer with several hazardous metals. Metals considered hazardous by CERCLA found in contaminated ground water were arsenic, antimony, beryllium, cadmium, copper, cyanide, lead, mercury, nickel, selenium, silver, and zinc. Elevated levels of arsenic, cadmium, copper, lead, and zinc were detected in ground water collected from the entire length of California Gulch. Several people living near California Gulch are currently using ground water that contains levels of cadmium and zinc above EPA Drink- ing Water Standards, while others, have abandoned their wells because of color, taste, and/or odor problems, toxic cadmium levels, or the availability of a public water supply. Insufficient Information is available to characterize heavy metal contamination of Arkansas River alluvial ground water. Surface water samples from the Arkansas River contained hazardous metals, however, and as a result, the alluvial ground water in close proximity to the river probably also contains hazardous metals. Other possible sources of contamination to the Arkansas River alluvium are seepage or infiltration of contaminated irrigation water, and infiltration through contaminated soils.

5-1 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

RESOURCES AND USES Occurrence Ground water at the Yak Tunnel/California Gulch site occurs in bedrock and in unconsolidated Tertiary and Quaternary deposits. The bedrock consists of Precambrian granite overlain by quartzite, limestone, and sandstone of Paleozoic age. Intrusive porphyritic rocks of Tertiary age form dikes and sills. Above the bedrock, the Quaternary age deposits are composed of unconsolidated stream deposits, terrace deposits, outwash gravels, and glacial drift. West of the Pendery Fault, Tertiary lake beds occur between bedrock and the Quaternary deposits. The unconsolidated deposits that are found at the site will be collectively referred to as valley fill. In general, the type of bedrock found at the site has relatively low permeability. However, extensive faulting occurred in late Ter- tiary time. The effect of the faulting, coupled with the mining activities, is an increase in the permeability and creation of hydraulic connections between units (Turk and Taylor, 1979). Thus, the bedrock and valley fill form a single hydrologic system. Based on studies by the U.S. Bureau of Mines (1949) and the U.S. Bureau of Reclamation (1979), the Leadville area is divided into the following structural basins: Carbonate Hill, Downtown, Fryer Hill, Iron Hill, Breece Hill, Evans Gulch, Printer Boy Hill, Rock Hill, Resurrection, and Yankee Hill. These studies conclude that the basins are bounded by large fault blocks which act as flow barriers. There- fore, each basin is believed to contain a separate aquifer. Early mine records state that large amounts of ground water were sometimes encountered when shafts or tunnels crossed a fault block into a separate basin. However, these inflows may have resulted from dewatering the more permeable fault zone. The oxidation at depth along

5-2 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION the faults as Suggested by Emmons et al. (1927) supports the flow conduit theory of Turk and Taylor. It may be that some faults act as flow barriers and others as conduits for ground water flow. In 1889, construction began on the Yak Tunnel for the purpose of exploring and draining the Iron Hill area. The tunnel was eventually extended to penetrate Breece Hill and Little Ellen Hill. For at least 50 years, the Yak Tunnel has drained the area east of Leadvilie and discharged mine waters into California Gulch. Turk and Taylor (1979) estimated the rate of ground water movement in the mine workings east of Leadville using pumping data in the mine shafts and a po tantieme trie surface map developed from 1944 water levels in the mine shafts. The mine shafts used in the study are shown on Figure 5.1. The gradient depicted on the figure is toward the southwest. However, extension of the Leadville Drainage Tunnel between 1944 and 1952 may have diverted much of this flow to the northwest. Transmissivities calculated from steady pumping from mine shafts were estimated using Darcy's law and the Thiem equation to be 400 to 1,000 square feet per day. Estimates of the hydraulic conductivity of the aquifer east of Leadville have yielded values up to 1.5 feet per day, which implies a potential flow of 1.3 cfs across an aquifer thickness of 1,000 feet, 1 mile wide (Turk and Taylor, 1979). Recharge to the bedrock aquifer is primarily from infiltration of snowmelt and rainfall. The average annual precipitation is approximately 18 inches. Fluctuations in the water table of 7 to 15 feet occur seasonally. Discharge of the ground water in the bedrock east of Leadville is to California Gulch and the Leadville Drainage Tunnel. In the upper reaches of the gulch, ground water may discharge to the thin valley fill. However, most of the discharge from the aquifer is intercepted by the Yak Tunnel, where normal discharge rates have been measured from 1.22 to 3.35 cfs.

5-3 EXPLANATION O10.21 8 MINE SIIAI:T-Number js altitude of water level, in feet, 1944. COMI'LETED TUNNEL. 1944 10.330— POTENTIOMETRIC CONTOUR - Shows altitudeContour, intervain feetl. is1944. 50 feet •',. APPROXIMATE ! DIRECriON Ol GROUND-WATER MOVEMENT SHAFTS A Villa 0 Capitol C Pcnrosc D Home Extension E Valentine F Califomin Gulch G Greenback II Pyrenees

liasc from U. S. Geological Survey FIGURE 5.1 1:24 0()(l Lcsidvillc South. 19*9 0 1 MILE anil l.ratlvillr Nntlli. 1970 J ELEVATION OF 0h 1 KILOMETER POTENTIOMETRIC SURFACE, 1944 Ret: Turk and Taylor. 1979 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION In California Gulch, the complex nature of the ores, and the mining of different ores at different times based upon demand, coupled with varying milling technologies have probably resulted in tailings of varying mineralogy and chemistry within the study area. Smelter Residues and Emissions Numerous smelters, reduction works, and zinc oxide plants were built and operated in the vicinity of the Leadville mining district. These facilities refined the high-grade ores and concentrates from the mines and mills to produce higher grade products. They also produced additional wastes such as slag, dust, and off-gases. The slag typically contains calcium, magnesium, iron and zinc oxides, and silica, as well as minor amounts of sulfur, lead, and copper. Much of the metal in slag has been oxidized in the smelting process and is in a relatively stable oxide mineral form. In addition, smelting results in the encapsulation of much of the metal in refrac- tory sites and in the formation of silicate minerals. Therefore, altough numerous slag piles occur throughout the study area, they are not expected to be a major source of hazardous metal contamination. Off-gas from early lead and copper smelting probably contained substantial amounts of potentially toxic pollutants because little technology was available to collect the solids or gases. In addition to the sulfur dioxide and sulfur trioxide gases that form sulfurous and sulfuric acids, the off-gas probably contained oxides numerous metals, including arsenic, lead, cadmium, copper, and other metals. This material was dispersed by wind currents and particulates deposited in the adjacent areas.

3-18 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

SITE GEOLOGY Several detailed descriptions of the geology and the ore deposits of the Leadville area have been published (Emmons et al., 1927; Behre, 1953 and Tweto, 1968, 1974). A brief summary of the site geology based upon these published reports is provided below. Surficial Materials Several types of surficial deposits occur in the project area. Talus, landslide deposits, and rock glaciers are found sporadically in areas of higher elevation. Glacial, glaciofluvial, and alluvial deposits, which are found in areas of lower elevation, are the surficial deposits of primary interest. Glacial Deposits Two, and possibly three, glacial stages have been recognized in the project area. Alpine glaciers starting along the crest of the Mosquito Range carved out U-shaped valleys, eroded, and consequently deposited large quantities of earth materials. Five valley glaciers were active in the area: the Evans glacier, East Fork glacier, South Evans glacier, Iowa glacier, and Empire glacier. Glacial and glaciofluvial deposits identified in the study area primarily include glacial drift deposited as terminal moraines, lateral moraines, and ground moraines, and the outwash material that was carried down into the Arkansas River valley by water from the melting ice. Subsequent erosion of the outwash deposits formed the high and low terraces identified in the Leadville area. Alluvial Deposits Modern stream alluvium is associated primarily with the Arkansas River. This material generally consists of reworked glacial till,

3-19 YAK TUNNEL/CALIFORNIA GOLCH 2/28/86 REMEDIAL INVESTIGATION outwash, and miscellaneous alluvial deposits. The lateral extent, character, and depth of these deposits have not been well defined in the project area. California Gulch was not glaciated. As a result, it is the only tributary draining the mining district that contains alluvial deposits of consequence (Emmons et al., 1927). These deposits have been worked over by placer mining and piled up to such a degree that previous geologic mapping of the area (Emmons et al., 1927) did not attempt to designate alluvial boundaries. Bedrock Geology Structure The Mosquito Range is the eroded eastern limb of the Sawatch anticline. The north-trending axis of this anticline ran roughly where the Arkansas River is located. Folding is not pronounced in the Leadville district. The sedimentary rocks and sills dip about 15° E and are broken by many faults. Faulting along the western side of the range consists of both high-angle normal and reverse faults (Figure 3.7). Dips along many of the faults approach vertical and may change along the trace of the fault. Most of the faults trend north-south and are downthrown to the west. Fault zones range from several feet to hundreds of feet wide. Faulting has produced a series of structural blocks in step-like succession from the crest of the Mosquito range westward toward the Arkansas River valley (Figure 3.7). Surficial evidence of faulting is in many places obscured by glacial deposits. Many of the faults have been thoroughly mapped in underground workings and their structure is well understood. Minor drag folding and breccia or gouge zones are commonly associated with the faults. Several episodes (pre-mineral-

3-20 FIGURE 3.7 A. PRINCIPAL FAULTS AND AREAS OF PRINCIPAL ORE BODIES, LEADVILLE DISTRICT, COLORADO I06°I5'

39°I5'

B. GENERALIZED CROSS-SECTION A-A'

«umim PLIOCENE AND PLEISTOCENE DEPOSITS TOP OF BASEMENT FROM; TWETO, 1968 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION ization and poVt-mineralization) of faulting are documented. The intense fracturing played a significant role in the igneous intrusion, mineralization, and oxidation of the district. The faults also played a significant role in the hydrogeology of the area, particularly prior to mining. Turk and Taylor (1979) report that the net effect of the faulting was to increase permeabilities and create hydraulic connections between geologic units. The recorded mining history of the area states that when mining operations penetrated a fault, water from "behind the fault" would rush into the shaft. However, since the faults act as conduits to ground water flow, when miners penetrated a fault zone they dewatered the highly permeable saturated zone. If the entire width of the fault zone was penetrated, then water from the opposite block entered the workings. Stratigraphy Bedrock in the area consists of Precambrian crystalline rocks overlain by beds quartzite, shale, limestone, dolomite, and sandstone of Paleozoic age (Figure 3.8). Those sedimentary deposits were exten- sively intruded by porphyry sills, dikes, and plugs during the Tertiary period. A brief description of these units is provided in Engineer- ing-Science Appendix 5. Ore Deposits Ore deposits of the Leadville mining district are discussed in detail in the published literature (Emmons et al., 1927; Behre, 1953; Tweto, 1968). A brief summary is provided below. The ore deposits are significant because they are the reason for the mining activity which has disturbed the area. As described by Tweto (1968, p. 682): The ore deposits are principally blanket or manto replacement deposits, but in the eastern part of the district many veins occur also. The replacement deposits are largely

3-22 LOCATION OF PENDERY FAULT

LEGEND • MW-1 MONITORING WELL 1 MONITORING WELL O 1000 2000 LOCATION MAP SCALE IN FEET TABLE 5.1 SUMMARY OF EPA MONITORING WELL CONSTRUCTION DATA Top of Steel Ground Casing Casing Level Total Screened Elevation Stickup Elevation Completion Well Location Deptit h Interval (ft) (ft) (ft) Date NW-1 Yak Tunnel UPGD 22 5-22 10,340.47 2.08 10,338.39 11/01/84 NW-2 Yak Tunnel DNGD 28 8-28 10,324.16 1.92 10,322.24 11/02/84 NW-3 Apache 96 26-76 10,067.15 1.50 10,065.54 10/25/84 NW-4 Oregon Gulch 45 5-45 10,135.23 1.75 10,133.48 11/03/84 NW-5 ASARCO/ Intermed 108 48-108 10,114.83 2.60 10,112.23 10/25/84 NW-5A ASARCO/ Shallow 35 15-35 10,114.78 2.02 10,112.76 11/02/84 NW-5B ASARCO/Bedrock 220 160-220 10,115.45 2.00 10,113.45 11/13/84 NW-6 Mid Flm Deep 123 90-110 9,974.11 2.15 9,971.96 10/20/84 NW-6A Mid Flm Shallow 29 9-29 9,974.23 2.00 9,972.23 11/02/84 NW-7 Asphalt Plant 130 90-130 9,909.27 1.96 9,907.31 10/22/84 NW-8 Diedrich Slag PI 53 16-53 9,746.34 2.35 9,743.99 11/06/84 NW-9 Hecla UPGD 50 10-50 9,874.62 1.94 9,872.68 11/04/84 NW-10 Hecla DNGD 50 10-50 9,787.71 2.71 9,785.00 11/03/84 NW-11 Diedrich House 55 25-55 9,816.24 2.17 9,814.07 11/04/84 NW-12 Malta Gulch 50 10-50 9,615.40 2.31 9,613.09 11/06/84 NW-1 3 Molleur Fid Deep 100 20-100 9,621.59 2.58 9,619.01 10/23/84 NW-13A Molleur Fid Shallow 25 14.5-25 9,622.27 2.58 9,619.69 11/05/84 NW-14 Trailer Park 50 10-50 9,530.49 2.92 9,527.57 11/05/84 NW-1 5 Super 8 35 14-35 9,897.61 2.13 9,895.48 11/06/84 NW-1 6 Starr Ditch 80 40-80 10,125.42 1.46 10,123.96 11/07/84 NW-17 Diedrich Slag PI 100 60-100 9,818.19 2.67 9,815.52 10/23/84 Source: EPA Appendix, Volume 1. [ I I I I I 1 TABLE 5.2 SUMMARY OF EXISTING WELL CONSTRUCTION DATA Top of Steel Ground Casing Casing Level Total Screened Elevation Stlckup Elevation Completion Well Location Depth Interval (ft) (ft) (ft) Date BW-1 Elk Horn Shaft 500.00 0-500 NA NA 10,600.00 NA EW-1 Airport 200.00 170-200 NA NA 9,930.00 11/20/72 EW-2 Molleur/House 120.00 85-120 NA NA 9,615.00 10/25/72 EW-3 Seppi 37.00 NA NA NA 9,530.00 01/01/57 EW-4 Casias 65.00 NA 9,528.15 -5.92 9,534.07 01/01/79 EW-5 Beck 35.00 NA NA NA 9,525.00 07/01/78 EW-6 Lk Fk Trlr Park 50.00 NA NA NA 9,515.00 01/01/78 EW-7 Schmidt 55.00 31-55 NA NA 9,530.00 07/13/66 EW-8 Baughman 45.00 21-45 9,530.97 -10.97 9,520.00 08/01/66 EW-9 Martinez 50.00 25-50 9,840.14 1.08 9,839.06 08/30/73 EW-10 Figuero 30.00 0.30 9,853.27 1.75 9,851.52 NA EW-11 Gardner 39.00 27-39 9,545.85 -3.50 9,549.35 09/30/74 EW-12 Chase/Shop 125.00 NA 9,627.50 -7.50 9,635.00 01/01/62 EW-13 Chase/House 92.00 77-92 9,660.61 2.17 9,658.44 09/15/83 EW-14 Mestsas 34.00 22-34 9,838.08 -5.50 9,843.58 09/16/63 EW-15 Hecla 575.00 161-575 NA NA 9,855.00 06/01/59 EW-16 Hlnsley 530.00 500-530 NA NA 10,600.00 09/01/80 EW-17 Zakralsek 50.00 NA 9,866.15 -6.17 9,872.32 01/01/65 EW-18 F. Shober 90.00 66-90 9,871.87 -5.75 9,877.62 12/16/66 EW-19 R. Shober 45.00 NA 9,874.99 -4.50 9,879.49 01/01/62 EW-20 Bain 90.00 NA NA NA 10,620.00 01/01/80 EW-21 Archuletta 90.00 NA 9,829.15 -5.75 9,834.90 01/01/65 EW-23 WInkler 39.00 17-39 9,839.67 -3.67 9,843.34 09/12/72 EW-24 Wlbbenmeyer 76.00 NA NA NA 9,750.00 01/01/76 EW-25 Myers/Well 42.00 NA 9,930.14 -5.92 9,936.07 NA EW-26 Gruden 43.00 NA 9,958.13 0.17 9,957.96 10/01/85 EW-27 Flores 15.00 0-15 9,854.50 2.67 9,851.83 NA EW-28 Molleur/Ponzle 110.00 85-110 9,626.52 -6.71 9,633.23 10/12/72 EW-29 Molleur/Fleld 100.00 65-100 9,622.15 2.00 9,620.15 09/28/74 EW-32 Myers/Crlbbed 20.00 0-20 9,928.71 -7.08 9,935.79 NA EW-33 Leadvllle Gold 130.00 NA 9,812.89 2.00 9,810.09 NA EW-35 Cerise 60.00 NA 9,502.05 -54.52 9,806.57 NA EW-36 Zadra 180.00 135-180 NA NA 9,685.00 01/01/79 NA - Not Available. Source: State Engineer's Office Water records. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION well, and 1,278 gdf in the deeper well. Using Darcy's equation, ground water velocity was calculated to be 0.01 cfs and 0.05 cfs in the shallow and deep wells, respectively, with total flow being the sum, or 0.06 cfs. Drilling activities show that the alluvial aquifer is generally low yield and appears to be unconfined. The results of the pumping test also show the valley fill is comprised of shallow and deep zones, which are hydraulically connected. As discussed previously, the valley fill is heterogeneous, being comprised of a variety of materials deposited by different geologic processes. In addition, in a typical valley fill (Davis, 1966), the finer materials (sands, silts, and clays) overlie coarser materials (gravels and cobbles). This results in an overlying slightly impermeable layer of fine sands, silts, and clays which would attenuate metal contamination and impede vertical migration of hazardous metal contamination. Typically, fine materials are less permeable than coarse materials by several orders of magnitude (Freeze and Cherry, 1979). The presence of two zones in the valley fill is also indicated by the difference in water chemistry. Alkalinity, chloride, and sulfate values differed between shallow and deep wells. Also, hazardous metals concentrations in the shallow wells were substantially higher than the deep wells (see following sections for complete discussion). The primary source of surface flow in California Gulch is the discharge from the Yak Tunnel. Surface water in the gulch recharges the shallow alluvial aquifer in the area. Hazardous metals in surface flows are carried into the shallow ground water system. Water levels in wells adjacent to the gulch are at elevations similar to channel elevations (EPA, 1985), suggesting a hydraulic connection between surface waters and shallow ground waters. Response of the monitoring wells during periods of high flow in the gulch is illustrated in Figures 5.4, 5.5, and 5.6. Figure 5.4 shows a correlation between

5-13 FIGURE 5.4 SURFACE FLOCORRELATIOW ANN D GROUNNOV 84 Dthr u WATENOV R85 LEVEL JUN NW~2 NOV NW—6MAR' A Tro3 NOV Eo MAR AUG' 03 Ul NOV II_JI CC III MAY JUN tn NOV DEC

O SEP NOV u_.j SW-7 ~T ~T 6 8 1O 12 APPROXIMATE DISTANCE FROM CONFLUENCE (ft)(000) x SURF FLOW v GND WATER BASED UPON DATA IN EPA APPENDIX. VOL. 1 AND VOL. 2 FIGURE 5.5 DISSOLVED CADMIUM CONCENTRATION Ground Water / Surface Water 45O 4OO - 35O - 3OO

O O 4 6 8 10 1 2 MW-13SW-12A/ MW-SW-98 / MW-6SW-7A / SW-4MW-5/ SW-3AMW-2 / Distance from Confluence (ft) D Surface Water______-t- Ground Water BASED UPON DATA IN EPA APPENDIX. VOL. 1 AND VOL. 2 SULFATE CONCENTRATIOFIGURE 5.6 N Ground Water / Surface Water 2.3 2.2 2.1 2 1.9 1 .8 1.7 1 .6 QE. 1 .5 CL 1.4 1 .3 -S-«-».o_ 1.2 -gD S' — ' 1.1 UQ) 1 C O.9 oo 0.8 0.7 0.6 0.5 0.4 O.3 O.2 1———— O 4 6 8 10 I 2 MW-13SW-12A/ MW-SW-98/ MW-6SW-7/A MW-SW-45/ SW-3AMW-2 / Distance from Confluence (ft) D Surface Water -f Ground Water BASED UPON DATA IN EPA APPENDIX,VOL. 1 AND VOL. 2 EW-14(PW1S

• EW-28 PRIVATE WELL SAMPLED BY EPA FIGURE 5.3 (PW2) CORRESPONDING ES SAMPLE NUMBER 0 1000 2000 PRIVATE WELL ^3552!?!!^^^ SCALE IN FEET LOCATION MAP YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION when a publifxf water supply was installed. Several wells along the gulch were abandoned because of color, taste, and/or odor problems, and the presence of cadmium. ES performed a ground water use survey in the Stringtown area. Any resident currently using ground water or who had used ground water within the previous 2 years was contacted. The survey identified nine private wells still in use. These wells are included on Table 5.3. Several of the residents surveyed complained of color, odor, and/or taste problems. Others used ground water sparingly because of low yield or because they had been informed by the EPA that their water contained cadmium (Mestas, 1985). George Rodriguez (1985) stated that his well was abandoned 10 years ago because of taste and odor problems. ES Appendix C contains the complete results of the survey. Residents of Leadville and all adjacent residential areas, including the residents of Stringtown not identified above, obtain potable water from the Parkville Water District. Parkville uses water from Canterbury Tunnel Wells, the Elkhorn Shaft and Big Evans Gulch Reser- voir (Parkville, 1986). Further discussion of public water supply in the study area is located in Chapter 6. NATURE AND EXTENT OF CONTAMINATION The uppermost aquifer along California Gulch is contained in the valley fill, and is comprised of two zones, shallow (less than 50 feet) and deep (50 feet to bedrock), as evidenced by differing geologic materials, water chemistry, and aquifer transmissivity. Surface flow and shallow ground waters are hydraulically connected and, as a result, hazardous metal contamination carried by surface flows in California Gulch has contaminated the shallow aquifer. Seepage from the tailings ponds located in California and Oregon Gulches probably also contribute to hazardous metal contamination in the shallow aquifer.

5-10 TABLE 5.3 PRIVATE WELLS CURRENTLY IN USE ES Sample EPA Sample Owner No. No. Lee Chase #1 PW8 EW-12 Lee Chase #2 PW25 EW-13 Orin Diedrlch PW27 EW-15 Adelia MartInez PW12 EW-9 Juan Mestas PW18 EW-14 The Molleur's PW2 EW-28 Cora Schmidt PW6 EW-7 Edith Seppi PW9 EW-3 Louis Zakraisek PW24 EW-17 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION California Gulch Upstream from the Pendery Fault, the California Gulch valley fill is generally comprised of alluvium, colluvium, and reworked mining debris. In the upper reaches of the gulch, the alluvium is a relatively thin layer overlying bedrock when compared to alluvium below the Pendery Fault. Information from the drilling logs for private wells shows an alluvial thickness greater than 500 feet in areas east of Stringtown (EPA, 1985). The lateral extent, character, and depth of these deposits have not been well defined for the project area. EPA (1985) performed several pumping tests on the monitoring wells in the study area to further investigate the valley fill. The tests consisted of withdrawal of water from one well, and either monitoring water level recovery in the withdrawal well or water level fluctuation in nearby wells. Aquifer characteristics such as transmissivity, storativity, and flow rate were obtained from the results. A complete presentation of the data and results is located in the EPA Appendix, Volume 2. At well cluster MW-13 and MW-13A, water was pumped from nearby private well EW-29 and water level drawdown was monitored. At a continuous pumping rate of 25 gpra for approximately 16 hours, a draw - 04 down of about 4 feet was seen in MW-13 compared with 1.7 inches of drawdown in MW-13A. The pumped well and MW-13 are deep wells which are screened at approximately the same depth, while MW-13A is shallow (25 feet). Monitoring wells MW-13 and MW-13A are located 92 feet north of EW-28 and are about 25 feet apart. Transmissivity for the shallow and deep zones of the uppermost aquifer was determined by matching field drawdown curves from pumping tests to type curves (see EPA Appendix, Volume 2). Transmissivity was calculated to be 316 gallons per day per foot (gdf) in the shallow

5-12 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION stream flows' and ground water levels, and indicates that surface and ground waters are hydraulically connected. Figures 5.5 and 5.6 show five pairs of surface water and ground water sample points selected on the basis of close proximity to one another along the length of the gulch. At each observation point, the time response curves for cadmium and sulfate ions have been plotted for both ground and surface water over the same flow period. The response in the ground water is much less dramatic than that in surface water. However, there is a correspondence in response to peak runoff during June at each point. In August 1985, surface water flow measurements indicated that California Gulch between Stringtown and the Leadville Sewage Treatment Plant (STP) is a losing stream. Thus, water flowing in the gulch recharges the gulch alluvium. Ground water in this alluvial aquifer may ultimately recharge the bedrock aquifer or flow down-valley and discharge to the Arkansas River or the Arkansas River alluvium. Water levels obtained by the EPA in 1985, indicate a general down-valley movement of ground water from MW-1 to MW-13A. The water levels in June 1985 ranged from 10,333 feet, mean sea level (ft., msl) at MW-1 to 9,603 ft., msl at MW-13A. Because the monitoring wells are in such close proximity to the stream in California Gulch, they are strongly influenced by surface flow and may not be indicative of flow in other parts of the valley. Monitoring Wells During late 1984 and throughout 1985, the EPA's consultant sampled ground water at the monitoring wells located along California Gulch. In addition, several private wells were sampled. ES accompanied the EPA consultant during sampling of the monitoring wells and split samples on two occasions. Arsenic, cadmium, copper, lead, and zinc are the primary hazardous metals resulting from the mining activities in the study area and were detected in surface water from the gulch. Other hazardous metals such

5-17 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

In NovemberS-j ^ 1984, EPA consultants installed 21 monitoring wells to delineate the hydrogeologic system in California Gulch. Figure 5.2 shows the location of each well, and Table 5.1 contains specific well construction details. The monitoring wells were completed at varying depths in the California Gulch valley fill. Ground water samples were collected from these wells by EPA and Engineering-Science (ES>. Dril- ling and sampling methods were performed in accordance with Section 6 of EPA's REM/FIT Quality Assurance Manual, and the ES_Quality Assurance

The EPA boring logs show that unconsolidated deposits (valley fill) in California Gulch range in thickness from 45 feet at MW-1 in the upper reaches of California Gulch to at least 260 feet of valley fill downstream at MW-5 where drilling was not advanced to bedrock. Valley fill increases in thickness west of the Pendery Fault (see Figure 5.2), which crosses California Gulch immediately upstream of the well cluster MW-5. The Pendery Fault, described by Tweto (1968), identifies a 200-foot subsurface fault scarp east of Leadville. The downdropped block west of the fault has been filled with thick valley fill. Further downstream, the maximum thickness of valley fill is greater than 100 feet as shown in the boring logs for MW-17. None of the boreholes down valley from MW-1 were advanced to the bedrock contact, so the total depth of the valley fill has not been determined. Uses Ground water in the Yak Tunnel/California Gulch study area is used for water supply on a limited basis. Review of the State Engineer's Office records and field investigations by the EPA identified 33 permitted wells along California Gulch. Their locations are shown in Figure 5.3 and Table 5.2 contains general Information on each of the 33 private wells. Most of these wells are designated for domestic or irrigation uses. Several additional wells were identified within the Leadville city limits, all of which were abandoned for domestic use

5-5 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION as beryllium, mercury, nickel, and selenium were detected in EPA samples less frequently and at lower concentrations (see EPA Appendix, Vol. 1 and 2). Table 5.4 is a summary of the sampling results for each monitoring well for each of the hazardous metals of primary concern. A complete list of the results for the EPA samples is located in EPA Appendix, Volume 2, and for ES samples in Appendix C. Ground water in the study area was found to be a calcium magnesium sulfate water containing varying concentrations of hazardous metals. Piper diagrams illustrating the typing of waters have been included in Appendix C. In general, wells that contained elevated levels of hazardous metals were also very high in sulfate and total dissolved solids. Field measurements of pH indicate that ground water varies from moderately to slightly acidic. Acidity increased in wells that contained elevated metal levels. The shallow wells placed down-valley of tailings impoundments and in the slag pile areas contained relatively high levels of metals. The results of ES split-samples were very similar to EPA results on the June and September 1985 sampling events. Beryllium and mercury were detected only in wells in the upper reaches of the gulch, from MW-1 to MW-7. Nickel was detected in several wells along the entire reach of California Gulch. Well MW-17, was the only well that contained selenium, with the concentration exceeding the Drinking Water Standard in November 1984. At a few wells, higher levels of the contaminants were detected in June than in November. During June, the levels of hazardous metals probably increased because there was more runoff from areas containing mining wastes and more precipitation to infiltrate into the ground wa ter. The most contaminated well is MW-4, located below the tailings pond in Oregon Gulch. Well MW-4 contained higher levels of arsenic, copper, and zinc than any of the other wells. EPA Drinking Water Standards (see Table 5.5) were exceeded for each of these metals, and

5-18 TABLE 5.4 YAK TUNNEL/CALIFORNIA GULCH SUMMARY OF GROUND WATER SAMPLING RESULTS (mg/l)(6) Depth to Screened EPA EPA EPA EPA EPA Well Interval (ft) 11/84 03/85 06/85 09/85 11/85 MW-1 (5-22) As 0.005 * ND(3) * ND * 0.007* - -(2) 0.014, Cd 1.220 (1) 1.120 1.290 1.500* 1.560, Cu 0.936 0.829 0.964* 1.040 1.100 Pb 0.088* 0.069* 0.080* ND * 0.141, Zn 175.600 151.000 165.000 192.000 190.000 CN ND ND ND NM(5) ND MW-2 (8-28) As ND ND 3.00% 0.004 ND Cd 0.305 0.438 0.411 0.460 0.461 Cu 0.249* 0.744* 0.328* 0.300* 0.410 Pb 0.338 0.570 1.140 1.360 0.248* Zn 78.110 66.900 66.800 75.000 87.100 CN ND ND ND NM ND MW-3 (26-76) As ND ND ND ND ND ND ND Cd ND ND ND ND ND ND ND Cu ND 0.003 0.003 ND 0.003 ND ND Pb 0.050 ND ND ND ND ND ND Zn 0.081 0.332 0.160 0.066 0. 120 0.055 0.051 CN ND ND ND NM ND NM ND MW-4 (5-45) As ND * ND * 0.430* 0.024, 1.320, Cd 0.706* 1.130*(4) 0.742* 0.750, 1.270, Cu 5.276 3.930 3.200 3.700, 4.570 Pb 0.472* ND 0.055* 0.380, ND , Zn 783.600 982.000 411.000 430.000 834.000 CN ND 0.007 0.022 NM 0.031 MW-5 (48-108) As ND ND ND ND ND Cd ND ND ND ND ND Cu 0.114 ND ND ND 0.004 TABLE 5.4 CONTINUED Depth to Screened EPA EPA EPA ES EPA EPA Well // Interval (ft) 11/84 03/85 06/85 06/85 09/85 11/85 MW-5 Continued Pb 0.005 ND ND ND ND Zn 2.353 0.021 0.051 0.013 0.184 CN ND ND ND ND ND MW-5A (15-35) As Dry Dry ND ND Dry Dry Dry Cd ND ND Cu ND ND Pb ND ND Zn 0.574 0.130 CN ND NM MW-5B (160-220) As ND ND ND 0.002 ND ND Cd ND ND ND ND ND ND Cu ND 0.003 0.003 ND 0.004 ND Pb ND ND ND ND ND ND Zn 0.032 0.026 0.095 0.022 0.019 0.058 CN ND ND ND NM ND ND MW-6 (90-110) As ND ND ND 0.002 ND ND ND Cd ND ND ND ND 0.006 ND ND Cu ND 0.006 0.004 0.003 0.005 ND 0.007 Pb ND ND ND ND ND ND ND Zn 0.121 0.715 0.103 0.061 0.071 0.053 0.061 CN ND ND ND NM ND NM ND MH-6A (9-29) As ND ND ND ND ^ ND ND Cd 0.040 0.052 0.061 0.050 0.055* 0.063 Cu ND * 0.008 0.006 0.006 0.006 0.037 Pb 0.118 ND ND ND ND 0.010^ Zn 14.27JH/ 14.300 16.700 11.100* 13.000* 17.700 CN 0.021 ND ND ND NM ND TABLI E 5.4I CONTINUE1 D Depth to Screened EPA EPA EPA ES EPA EPA Well // Interval (ft) 11/84 03/85 06/85 06/85 09/85 11/85 MW-7 (90-130) As ND ND ND ND ND ND ND Cd ND ND ND ND ND ND ND Cu 0.013 0.009 0.031 0.006 0.007 0.005 0.008 Pb ND ND ND ND ND ND ND Zn 0.117 1.020 0.458 0.170 0.153 0.064 0.110 CN ND ND ND NM ND NM ND MW-8 (16-53) As ND ND ^ ND 0.002^ ND ^ ND ND Cd 0.04 6 # 0.037 0.114 0.100 0.106 0.140* 0.116* Cu ND 0.004 ND 0.020 0.003 0.003 0.003 Pb ND £ ND * ND ^ 0.049 ^ ND * ND ND Zn 15.330 14.800 31.400 26.000 22.900 28.000* 188.000 CN ND ND ND NM ND NM ND MW-9 (10-50) As ND(4) ND ND ND Dry Cd ND ND ND ND Cu 0.097^ 0.006 0.004 ND Pb 0.067 0.011 ND ND Zn 1.897 0.320 0.264 0.120 CN ND ND ND NM MW-10 (10-50) As ND . ND ND . ND * ND ND Cd 0.207 0.007 0.032 0.019 0.020* 0.007 Cu 0.025 0.006 0.004 0.003 0.003 0.004 Pb ND . ND ND ND ND ND Zn 30.160 1.040 4.930 3.510 3.600 1.540 CN ND ND ND ND NM ND MW-11 (25-55) As ND ND ND ND ND ND Cd ND ND ND ND ND ND Cu ND 0.027 ND ND ND ND Pb ND ND ND ND ND ND Zn 0.124 0.229 0.200 0.203 0.087 0.112 CN ND ND ND ND NM ND TABLI E 5.4I CONTINUEI D Depth to Screened EPA EPA EPA ES EPA EPA Well I Interval (ft) 11/84 03/85 06/85 06/85 09/85 11/85 MW-12 (10-50) As ND ND ND ND ND ND Cd ND ND ND ND ND ND Cu ND 0.002 ND 0.007 ND ND Pb ND ND ND ND ND ND Zn 0.042 0.102 0.112 0.087 0.059 0.092 CN ND 0.089 0.061 NM 0.083 0.078 MW-13 (20-100) As ND ND , ND ND * ND ND , Cd 0.014 0.063 0.07 2 t 0.080 0.114 0.059 Cu ND * 0.048 0.053 0.054 0.061 0.055 Pb 0.102 ND , ND ND , ND , ND Zn 1.938 9.070 9.600 11.000 13.700 8.680 CN ND 0.083 0.041 NM ND 0.081 MW-13A (14.5-25) As ND ND * ND * 0.003 * ND * ND j Cd 0.301 0.231 0.240 0.270 0.204 0.233 Cu 0.240 0.711 0.688 0.770 0.517* 0.631 Pb ND * 0.019* 0.014* 0.030* 0.051* 0.016^ Zn 43.780 33.000 34.500 40.000 29.500 31.700 CN ND ND ND NM ND ND MW-14 (10-50) As ND * ND ND ND ND ND Cd 0.014 ND ND 0.005 0.010 0.008 Cu ND 0.003 ND ND ND ND Pb ND ND 0.002 ND ND ND Zn 1.829 1.730 0.571 0.720 1.410 1.490 CN ND 0.007 ND NM ND ND MW-15 (14-35) As ND i ND * ND ND * ND * ND ND * Cd 0.030 0.027 0.03 2 4 0.032 0.035 0.027* 0.027 Cu ND 0.004 0.006 ND 0.003 ND 0.007 Pb ND i ND * ND , ND * ND * ND ND * Zn 7.867 6.780 6.700 7.100 6.180 6.600* 5.410 CN 0.175 ND ND NM ND NM ND TABLE 5.4 CONTINUED Depth to Screened EPA EPA EPA ES EPA ES EPA Well # Interval (ft) 11/84 03/85 06/85 06/85 09/85 09/85 11/85 MW-16 (40-80) As ND ND ND ND — ND Cd 0.006 0.006 ND ND — ND — Cu 0.03013 0,008 0. 008 0.004 0. 006 Pb 0 ND 0. 004 0.003 — ND ' ': h Zn 5 •.994°* 1.450 1. 110 0.627 — 0. 664 CN ND ND ND ND — ND MW-17 (60-100) As ND ND 0. 007 0.007, 0.004 0. 004. Cd 0.107* 0.030 0. 027 0.013 ND 0. 016 Cu ND 0.011 0. 017 0.006 ND 0. 009 Pb ND 0.050 ND ND ND ND Zn 0.722 0.553 0. 463 0.157 0.087 0. 321 CN ND ND ND ND NM ND (1) *- Value exceeds EPA Primary or Secondary Drinking Water Standard (2) — Well not sampled. (3) ND - not detected a specified detection limit. See EPA and Engineering-Science Appendices for detection limits (4) All values for CN, and MW-4, 3/85 sampling date, and MW-9, 11/84 sampling date are TOTALS not dissolved. (5) NM - not measured. (6) All values are dissolved, unless otherwise specified • TABLE 5.5 FEDERAL AND STATE WATER QUALITY STANDARDS Proposed EPA EPA EPA Primary Secondary Colorado Primary Drinking Drinking Drinking Drinking Water Water Water Water Parameter Units Standard Standard Standard Standard Arsenic mg/1 0.050 — 0.050 0.050 Barium mg/1 1.000 — 1.500 1.000 Cadmium mg/1 0.010 — 0.005 0.010 Chloride mg/1 — 250 — — Chromium mg/1 0.050 — 0.120 0.050 Copper mg/1 — 1.000 1.300 • — Cyanide(l) mg/1 — — — — Iron mg/1 — 0.300 — — Lead mg/1 0.050 — 0.020 0.050 Manganese mg/1 — 0.050 — — Mercury mg/1 0.002 — 0.003 0.005 Nickel mg/1 — — — — Nitrate mg/1 10 — 10 10 Selenium mg/1 0.010 — 0.045 0.010 Silver mg/1 0.050 — — 0.050 Sulfate mg/1 — 250 — — TDS mg/1 — 500 — — Zinc mg/1 — 5.000 — — (1) Cyanide is very rarely encountered in drinking water. Therefore, the EPA is proposing a guidance level of 0.75 mg/1 for adults and a 10-day exposure limit for children of 0.22 mg/1, instead of standards. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION arsenic andj^copper levels were as much as 26 and 5 times higher, respectively, than the standards. Zinc levels ranged from 82 to 196 times higher than the standard. These elevated levels are probably a result of seepage from the tailings due to the location and of the relatively shallow total depth (45 feet) of MW-4. Total cyanide was detected in EPA samples on several sampling dates. No source for the cyanide has been determined. Wells MW-1 and MW-2, located in California Gulch above and below the Yak Tunnel, also showed elevated levels of arsenic, cadmium, copper, and zinc. EPA Drinking Water Standards were exceeded for each of these metals except copper during several of the sampling periods. Zinc levels exceeded EPA Drinking Water Standards by as much as 38 and 15 times for MW-1 and MW-2, respectively. Concentrations of cadmium exceeded the standards by as much as 150 and 45 times at MW-1 and MW-2, respectively. Copper and arsenic levels at MW-1 were slightly above standards only during the November 1985 sampling event, while at MW-2, arsenic was above standards during the June 1985 sampling event while copper levels were below the standard. In addition, well MW-2 has a high level of lead which exceeded the standard by 27 times in June 1985. These hazardous metals have been identified as major contaminants in California Gulch surface water samples from the same locations. Well MW-1 is located directly upstream from where the Yak Tunnel discharges into California Gulch. Upstream of this point, California Gulch flows in and near several waste rock piles, and probably carries shallow contamination to MW-1. Well MW-2 is located directly downstream of the point where the Yak Tunnel discharges into California Gulch and is also a shallow well. Data indicate shallow ground waters adjacent to California Gulch at this point have been contaminated by the Yak Tunnel discharges. Further downstream on California Gulch, elevated levels of heavy metals are primarily present in wells less than 50 feet deep. At well

5-25 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION cluster MW-SV- MW-5A and MW-5B have total depths of 35 and 260 feet, respectively. The zinc concentration in MW-5A was, on the average, approximately six times higher than in MW-5B. Monitoring wells MW-6 and MW-6A also differed substantially. MW-6A is 29. feet deep and contained zinc concentrations one to three orders of magnitude higher than concentrations detected in MW-6, which is 110 feet deep. For wells MW-13 and MW-13A (100 and 25 feet deep, respectively), MW-13A showed substantially higher levels of cadmium, copper, and zinc than MW-13. Therefore, it appears that high concentrations of heavy metals are confined to the upper 50 feet of the aquifer and relatively little vertical migration occurs. Well cluster MW-5 is located immediately downgradient of tailings pond 2. Seepage from this pond contributes to the elevated levels of hazardous metals found in water from MW-5A. Hazardous metals were detected in groundwater at varying concentrations along the entire length of California Gulch from above the Yak Tunnel to the confluence with the Arkansas River. The Pendery Fault crosses the gulch below Carbonate Hill in the vicinity of the MW-5 nest of wells. Results from well cluster MW-5 do not show high zinc contamination at depths greater than 50 feet. This suggests that the source of contamination is at the surface rather than at depth from the fault zone. Cyanide was detected by the EPA in the ground water at MW-4, MW-12, MW-13, and MW-14. EPA surface water sampling found cyanide in the discharge from the Leadville Sewage Treatment Plant (SW-11), which might explain its presence in MW-13 and MW-14. However, for MW-4 and MW-12, the source of cyanide has not been located. Private Wells During 1984 and 1985, 31 of the 33 private wells identified by the EPA along California Gulch and immediately below the confluence of the

5-26 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION gulch and the. Arkansas River were sampled by EPA. . ES personnel obtained water samples only at each of the nine households identified as currently or recently using their wells during the Stringtown water use survey. ES obtained a representative sample of water directly from the faucet in each home after the aerator was removed and the water had been running for several minutes. EPA obtained a sample in the same manner as ES or by pumping directly from the well. Two wells, EW-25 and EW-33 were not sampled at any time by the EPA or ES. The locations of the private wells are shown on Figure 5.3. Table 5.6 contains a summary of hazardous metal concentrations detected by the EPA at 12 private wells in the study area. These 12 wells were chosen as overall representatives of the ground water quality along the length of Cali- fornia Gulch to its confluence with the Arkansas River. Table 5.7 contains the results of ground water analyses from the ES sampling activities. A complete tabulation of sampling results is located in Appendix, Volume 2 and Appendix C for the EPA and ES data, respectively. Every private well sampled contained detectable levels of zinc. Both ES and EPA data for wells PW8 (EW-12), PW18 (EW-14), and PW25 (EW-13) indicated zinc levels ranging from one to six times the EPA Secondary Drinking Water Standard. All of these wells are currently in use for domestic purposes. In addition, EPA found zinc levels at a maximum of seven times the standard at EW-19. Cadmium was detected in several wells. The EPA Primary Drinking Water Standard for cadmium was exceeded by factors of as much as four and 11 at PW18 (EW-14) and PW8 (EW-12), respectively. Both wells are currently in use for domestic purposes, and both were sampled by ES and EPA. EPA data also indicates that private wells EW-19 and EW-32 exceeded the cadmium standard during some of the sampling dates. Detectable levels of cyanide were encountered by EPA in EW-1, EW-2, EW-3, EW-6, EW-12, EW-13, and EW-29. As stated previously, no

5-27 TABLE 5.6 SUMMARY OF RESULTS FROM PRIVATE WELL SAMPLED BY EPA(6) (all results In mg/1) Screened Interval Well No./Date (feet) As Cd Cu Pb Zn CN EW-1 170-200 3/84 ND(1) ND ND ND 0.231 ND 6/84 ND ND ND ND 0.241 NM 11/84 0.005 ND ND ND 0.424 ND 3/85 ND ND 0.006 ND 0.266 ND 6/85 ND ND 0.006 ND 0.335 ND 9/85 ND ND 0.006 ND 0.206 ND 11/85 ND ND 0.006 ND 0.328 1.030* EW-2 85-120 3/84 ND ND ND ND 0.017 0.030 6/84 ND ND ND ND ND 0.036 11/84 ND ND ND ND ND ND 3/85 ND ND ND ND 0.173 0.075 6/85 0.010 ND 0.003 ND 0.007 0.088*(2) 9/85 ND ND ND ND 0.023 0.084* 11/85 ND ND ND ND 0.020 0.165 EW-3 NA(5) 3/84 ND ND ND 0.008 0.053 0.012 6/84 ND ND ND ND 0.109 NM 11/84 ND ND 0.010 ND 0.051 ND 3/85 ND ND 0.004 ND 0.026 ND 6/85 ND ND ND ND 0.061 ND 9/85 ND ND ND ND 0.071 ND 11/85 ND ND 0.004 ND 0.256 0.020 EW-5 NA 3/84 ND ND ND ND 0.144 ND 6/84 —(4) ""^ 11/84 — — — — 3/85 6/85 9/85 ND ND 0.039 ND 0.150 ND 11/85 ND ND 0.036 ND 0.334 ND EW-6 NA 3/84 ND ND ND ND 0.037 ND 6/84 ND 0.009 ND ND 0.771 NM 11/84 ND ND ND ND 0.106 ND 3/85 ND ND 0.004 ND 0.070 ND 6/85 ND ND ND ND 0.212 ND 9/85 ND 0.004 0.003 ND 0.162 ND 11/85 ND ND ND ND 0.068 2.060* TABLE 5.6 (CONTINUED) SUMMARY OF RESULTS FROM PRIVATE WELL SAMPLED BY EPA (all results in mg/1)

Well No./Date Interval As Cd Cu Pb Zn CN EW-9 25-50 3/84 ND ND ND ND 0.125 ND 6/84 ND ND ND ND 0.068 NM 11/84 3/85 6/85 9/85 11/85 ND ND 0.025 ND 0.088 ND EW-12 NA 3/84 ND 0.115* ND ND 25. 885* ND 6/84 ND 0.099* ND ND 26. 100* NM(3) 11/84 ND 0.116* ND ND 32. 520* 0.088* 3/85 ND 0.068* ND ND 19. 800* 0.099* 6/85 ND 0.085* ND ND 22. 100* 0.093* 9/85 ND 0.080* 0.007 ND 20. 800* 0.101* 11/85 ND 0.088* ND ND 21. 900* 5.270* EW-13 77-92 3/84 ND ND ND ND ND 0.016 6/84 ND ND ND ND 0.034 0.155* 11/84 ND ND ND ND 0.249 0.046 3/85 6/85 ND ND ND ND 0.269 0.204* 9/85 ND ND 0.004 ND 0.114 0.203* 11/85 ND ND ND ND 0.217 0.476* EW-14 22-34 3/84 ND 0.012* ND ND 2 .513 ND 6/84 ND 0.009 ND ND 1.540 NM 11/84 ND ND ND ND 0.732 ND 3/85 ND ND 0.004 ND 0.414 ND 6/85 ND 0.015* ND ND 4.930 ND 9/85 ND ND ND ND 1.110 ND 11/85 ND 0.009 0.004 ND 1.300 0.014 EW-17 NA 3/84 ND 0.006 ND ND 1.334 ND 6/84 ND 0.010 ND ND 5.200* NM 11/84 ND ND 0.012 ND 1.870 ND 3/85 ND ND 0.002 ND 0.974 ND 6/85 ND ND ND ND 1.550 ND 9/85 ND ND ND ND 1.090 ND 11/85 ND 0.005 0.014 ND 1.420 ND TABLE 5.6 (CONTINUED) SUMMARY OF RESULTS FROM PRIVATE WELL SAMPLED BY EPA (all results in mg/1) Well No./Date Interval As Cd Cu Pb Zn CN EW-26 NA 3/84 ND ND ND ND ND ND 6/84 ND ND ND ND 0.011 NM 11/84 ND ND ND ND 0.101 ND 3/85 ND ND 0.002 ND 0.029 ND 6/85 ND ND 0.005 ND 0.138 ND 9/85 ND ND 0.008 ND 0.136 ND 11/85 ND ND 0.006 ND 0.089 ND EW-29 65-100 3/84 6/84 ND 0.048* ND ND 13.000* 0.100* 11/84 ND ND 0.012 ND 0.658 0.057 3/85 ND ND ND ND 0.557 0.162* 6/85 ND ND 0.004 ND 0.267 0.165* 9/85 ND 0.006 ND ND 0.650 0.165* 11/85 ND 0.004 0.004 ND 0.516 0.187

NOTES: (1) ND - Not detected at specified detection limit. See EPA Appendices for detection limit. (2) * - Value exceeds EPA Primary or Secondary Drinking Water Standard, or proposed guidance level. (3) NM - Not measured. (4) — - Not sampled. (5) NA - Not available. (6) All values dissolved unless otherwise specified. TABLE 5.7 SUMMARY OF RESULTS FROM PRIVATE WELLS SAMPLED BY ES (all results in mg/1) ES Sample EPA Sample Owner No. No. As Cd Cu Pb Zn Lee Chase #1 PW8 EW-12 ND(1) 0.076 ND ND 19.0(2) Lee Chase #2 PW25 EW-13 ND ND ND ND 5.90 Orin Diedrich PW27 EW-15 ND ND ND ND 0.085 Adelia Martinez PW12 EW-9 ND ND 0 .057 ND 0.063 Juan Mestas PW18 EW-14 ND 0.045 0.010 ND 11.00 The Molleur's PW2 EW-28 ND ND ND ND 0.03 Cora Schmidt PW6 EW-7 ND ND 0 .066 ND 0.23 Edith Seppi PW9 EW-3 ND ND ND ND 0.10 Louis Zakraisek PW24 EW-17 ND 0.005 ND ND 1.20 Detection Limit 0.002 0.004 0,003 0.025 (1) ND - Not detected at specified detection limit. (2) All values are dissolved. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION source for cyanide has been identified. Wells EW-1, EW-6, EW-12, and EW-13, exceeded proposed EPA guidance levels of either the 0.22 mg/1 10-day limit for exposure to children or 0.75 mg/1 for exposure to adults. Ecology and Environment (1983) sampled nineteen private wells in the vicinity of California Gulch to evaluate ground water quality. The results indicate that ground water is generally sulfate enriched, slightly acidic to neutral, and shows evidence of contamination by cadmium and zinc. The contamination identified in their study appeared to occur only in the vicinity of California Gulch and did not extend into the Arkansas River Valley. Arkansas River Alluvium Elevated concentrations of heavy metals in shallow ground water of the Arkansas River alluvium probably occurs because of contamination by polluted surface water, as is found in California Gulch alluvium. Also, infiltration from contaminated irrigation water and/or precipitation infiltration through contaminated soils probably reaches alluvial ground water. The Arkansas River below California Gulch showed high levels of cadmium, copper, and zinc* Because of surface water infiltration, the near-surface ground water in the immediate vicinity of the Arkansas River is probably contaminated. However, the extent of contamination (if any) is unknown at present. Further investigation involving the installation of monitoring wells would be required to determine the extent of contamination in the Arkansas River alluvium. Currently, there is one monitoring well located in the Arkansas River alluvium (MW-14). Well MW-14 consistently contained detectable levels of cadmium and zinc, and on isolated sampling dates contained copper and lead. None of the hazardous metals detected exceeded the EPA Drinking Water Standards. Cyanide was detected in March 1985, but was not detected in subsequent sampling periods.

5-32 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

Studies of private wells by Ecology and Environment (1983) found that hazardous metal contamination did not extend into the Arkansas River alluvium. However, detailed information concerning total depth, screened interval, and materials in which the private wells were completed was not available. Concentrations of hazardous metals may decrease in much the same manner as found along California Gulch, if the wells were screened at depths greater than 50 feet, and, contamination occurring at shallower depths would not be detected. Crouch et al. (1984) found that wells completed in the Arkansas River valley fill near Leadville contain high dissolved solids concentrations and attributed the degradation to mine drainage. They also found that sulfate is the dominant or codominant anion in the areas and that is is also the dominant anion found in mine-drainage water. Sulfate's presence in large concentrations in water from these wells is further evidence of degradation by mine drainage. The study did not include hazardous metals investigations. ENVIRONMENTAL AND PUBLIC HEALTH EFFECTS Ground water studies have shown that California Gulch valley fill is contaminated with hazardous metals resulting from recharge by contaminated surface water, and seepage from tailings ponds. The extent of contamination in the California Gulch alluvium is probably limited to a narrow band surrounding the gulch. In addition, hazardous metals concentrations above standards appears to be confined to the upper 50 feet of the aquifer. All of the private wells sampled in the vicinity of California Gulch contained detectable levels of zinc, with some concentrations exceeding EPA Drinking Water Standards. Three private wells with zinc concentrations exceeding the standard are currently in use for domestic purposes. Cadmium was found in two wells currently in use at levels

5-33 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION above the -£PA Primary Drinking Water Standard. Acute and chronic exposure to cadmium In humans can result in renal disfunction, hypertension, anemia, and altered liver microsomal activity. Cyanide was detected at several locations along California Gulch. Since cyanide is so rarely encountered in water, the EPA has proposed guidance levels instead of standards. Cyanides are readily absorbed through the lungs, the gastrointestinal tract, and skin. The toxic effects of cyanide result in hypoxia, a deficiency of oxygen reaching the tissues of the body. Arkansas River alluvium is probably contaminated as a result of discharge of contaminated ground water from California Gulch, Inter- action of ground water with contaminated surface water, seepage and infiltration of contaminated Irrigation water, and infiltration through contaminated soils. The contamination may exhibit the same horizontal and vertical migration patterns as that found in California Gulch. Studies by Crouch et al. (1984) indicate that the ground water In the Arkansas River alluvium has been adversely affected by mining activities In the Leadville area. However, further investigations are needed to determine the effect of hazardous metal contamination on the ground water in this area.

5-34 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION CHAPTER 6 SURFACE WATER INVESTIGATION The primary sources of contamination in the surface water in California Gulch are Yak Tunnel, the tailings ponds deposited in California Gulch, Starr Ditch, and drainage from the upper California Gulch basin. Starr Ditch and the upper gulch drain large areas of mine dumps that have been shown to leach hazardous metals. These sources contribute a number of hazardous substances, including arsenic, beryllium, cadmium, chromium, copper, cyanide, lead, nickel, selenium, and zinc to the surface water in California Gulch. Surface waters transport the contaminants into the uppermost aquifer along California Gulch and to the Arkansas River. Metals in surface waters produce adverse impacts to aquatic life in California Gulch and in the Arkansas River from the confluence with California Gulch as far as Salida and possibly to Canon City. Metals transported by surface waters also affect soils and vegetation in the upper Arkansas Valley that have been irrigated with water from the Arkansas River below California Gulch. Human health impacts may exist for people directly exposed to contaminated surface water, including residents of the cities of Aurora and Colorado Springs which divert water from the Arkansas River below Granite. RESOURCES AND USES Description The Arkansas River is the major surface water resource in the Leadville area. The headwaters of the East Fork of the river are found approximately 9 miles north of Leadville, at an elevation of 12,540 feet. The Arkansas River is formed by the confluence of the East Fork of the Arkansas River and Tennessee Creek, north of the town of Lead- ville. The river flows generally south from this point through a 6-1 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION valley varying In width from approximately 1 to 4 miles. Below Lake Greek the Arkansas River Valley narrows considerably. An area map is provided in Figure 6.1. The Leadville mining district is drained by several gulches that are tributary to the Arkansas River, including California Gulch. Many of these gulches flow only in response to major precipitation events and snowmelt. Most of the mining cost of Leadville has involved recovery of subsurface ores and has resulted in the construction of numerous underground mines and shafts. To prevent flooding of the early underground workings, costly pumping was required, and drainage tunnels were constructed as a solution to this problem. The Yak Tunnel is the most extensive of these drainage tunnels. The Yak Tunnel collects ground water and discharges it as a point discharge to Calif- ornia Gulch. This discharge is the primary source of flow for hazardous metal transport into the Arkansas River. The California Gulch watershed is approximately 11.5 square miles (7,400 acres) in area (McLaughlin Engineers, 1981). The gulch flows generally east to west through a narrow valley which widens south of the town of Leadville. Upstream of the Yak Tunnel, California Gulch flows only during snowmelt or storm events. During 1985, Engineering- Science measured the flow in the gulch just above Yak Tunnel at 3.20 cfs in May, and 2.31 cfs in June. There was no flow in the gulch of this location in August. EPA consultants measured a flow of 1.31 cfs in June 1984. The flows they measured decreased to between 0.16 and 0.49 vfs from August through November 1984. During 1985, they noted that the gulch was dry in March. A flow of 2.67 cfs was measured in June, with no flow noted for August through November 1985. McLaughlin Engineers (1981) reported a flow of only 0.1 cfs in June 1981 just above the Yak Tunnel portal and did not observe any flow during their August and November sampling.

6-2 FIGURE 6.1 LOCATION MAP

DENVER AND RIO SRANOE WESTERN J\ ^x^f—\L CLOTWORTHY RANCH TCS2W A« •-" / / .4*V .CANTERBURY TUNNEU i9V",J?7--^ / / - y

/•* — •— — " -LEAOVIULE DRAINAOE TUNNEL ,»^^ ~ -

Stray Horst Gulch

SEPPl'S RANCH- California Gulch ARS4W X ST. HWY 300 | ^

SMITH RANCH">^ \ ^ft.

NORTH 0 I/2 1 Mile YAK TUNNEL/CALIFORNIA GULCH 2/28/86 -'" REMEDIAL INVESTIGATION The Yak Tunnel, which drains a large number of mines in the Lead- ville area, is the primary source of flow in California Gulch. Flows from the tunnel measured by ES in May and June of 1985 were 1.98 and 2.27 cfs. During the EPA study, it was found that the discharges from Yak Tunnel ranged between 1.035 and 2.7 cfs, with the highest flows occurring during the months of May and June. Downstream from the Yak Tunnel portal, California Gulch flows around three tailings ponds deposited within the drainage. In the springtime, two tributary streams, Starr Ditch and Oregon Gulch, contribute flow to California Gulch just downstream of the lowest tailings pond in the gulch. Starr Ditch was originally built to divert flow from Evans Gulch to California Gulch for placer mining. Diversion of water from Evans Gulch has been discontinued. However, the ditch continues to intercept surface runoff from Stray Horse Gulch, which drains the Carbonate Hill mining area, and collects storm runoff from the eastern part of the town of Leadville (see Figure 6.1). Flows in Starr Ditch above the confluence with California Gulch ranged from dry conditions to 2.85 cfs. Oregon Gulch is the site of the fourth tailings pond in the area. This gulch flows into California Gulch just downstream from the confluence of California Gulch with Starr Ditch. California Gulch continues to flow westward through Stringtown, a small residential community, past the site of the old ASARCO smelter. It receives effluent from the Leadville Sewage Treatment Plant (STP) slightly more than a mile upstream from the confluence of California Gulch with the Arkansas River. The Leadville STP is a secondary treatment plant to which a polishing pond was added in 1985. The discharge pH is generally neutral to slightly alkaline, with a flow averaging 0.65 millon gallons per day (MGD) or 1.01 cfs. (Colorado Department of Health, 1982).

6-4 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 •"" REMEDIAL INVESTIGATION A series of flumes and gaging stations were installed by the EPA contractor to monitor the flow in California Gulch. These data are tabulated in the EPA Appendices K and N. At the confluence of Calif- ornia Gulch and the Arkansas River, maximum flows in the Arkansas River ranged up to 300 cfs. The range of flow in California Gulch at the confluence was 0.619 and 7.2AO cfs. during the study period except during the October 1985 surge event when a flow of 9.84 cfs was recorded. Monthly average flows in the Arkansas River at Leadville Junction (above California Gulch) ranged from 13.6 cfs. to 350 cfs for water years 1968 through 83 (USGS WATSTOR Data, 1985). Below the confluence with California Gulch, the Arkansas River flows south for approximately 1.5 miles to the confluence with the Lake Fork of the Arkansas. The flow ratio between the Arkansas River and Lake Fork is about 1 to 1. The river valley remains broad until below the river's confluence with Lake Creek, where the valley narrows considerably. Potential for Flood Damage The flood damage potential in California Gulch is quite high because of the lack of vegetative cover. A report prepared by the Corps of Engineers (COE) in 1983 estimates the capacity of California Gulch to be 50 cfs. Currently, the three tailings impoundments in California Gulch and the impoundment in Oregon Gulch are major structures that could both restrict flood flows and be damaged by floods. Because the tailings ponds contain hazardous materials (see Chapter 4), heavy surface runoff could result in substantial contributions to the surface water system through mass wasting as well as potential stability problems. Examples of breaching of the drainage channel that diverts water around the tailings ponds during periods of high runoff have been noted by EPA contractors.

6-5 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION The determination of the dam tailings stability for tailings ponds 1, 2, and 4 has been assigned to EPA's Emergency Response Team (ERT). The stability of tailings pond 3 is discussed in Chapter 4. The results of the ERT study, considered with the information contained in the report by the Army Corps of Engineer (COE, 1983) will be considered relative to the preparation of the environmental assessment and the feasibility study. Water Use and Supply The primary uses of the Arkansas River in the upper Arkansas River Valley are irrigation of ranch land and water for stock. Several ranchers in the area divert water from the Arkansas River (Figure 6.1). Irrigation generally occurs from early June to early August. The Hayden Ranch has water rights for diversion of a total of 50 cfs from several diversion ditches on the Arkansas River above the confluence with Empire Gulch. The Smith Ranch switched from diverting Arkansas River water to diverting Lake Fork water 2 years ago because of damages they perceived from metals contamination (Smith, 1985). Further north, at the Seppi Ranch, California Gulch was previously used as an irrigation source, but the water right was abandoned because of the poor water quality in California Gulch (Seppi, 1985). The Sappi Ranch now diverts 3.5 cfs of irrigation water from the Arkansas River above California Gulch. Water samples collected from irrigation ditches in late June 1985 contained cadmium, copper, lead, and zinc. The total zinc concentration in the sample from the Hayden Ranch was 0.41 mg/1, approximately 10 times greater than in samples from the Smith Ranch (0.04 mg/1) and the Clothworthy Ranch (0.029 mg/1). The Bureau of Reclamation's Fryingpan-Arkansas Project (see Figure 6.2) provides irrigation, municipal and industrial water; recreation; flood control; and power generation from the Mt. Elbert Pumped-Storage Powerplant (Roline and Boehmke, 1981). This project diverts water from

6-6 ( - • :; •• —- '-% >, ij _2 »' 0Breekaridqe - ' N.

EASTERN COLORADO WATER CONSERVANCY OISTRI

• \: ... S

MT. ELBERT PUMPED- "Li!»jr;" \ STORAGE POWERPLANT^ c / :> LAKES^

WESTERN AND UPPER EASTERN SLOPE AREAS

FIGURE 6.2 Fryingpan - Arkansas Project Map (Source: Sartoris, et al., 1977) YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION the Fryingpan River basin on the West Slope into Turquoise Lake northwest of Leadville. The water is released into Lake Fork. From 15 to 370 cfs of the flow of Lake Fork and 7 to 150 cfs of the flow of Halfmoon Creek are diverted to the Mt. Elbert Conduit, which carries this flow to the forebay of the Mt. Elbert Pumped-Storage Powerplant (Kilgore, 1985). The diversions, which began on May 5, 1982, now occur from May through early August. The flow from the project that is released into Twin Lakes is discharged to Lake Creek and then into the Arkansas River north of Granite. Flow is diverted from the Arkansas River below Granite into the Homestake Conduit where it flows to the cities of Aurora and Colorado Springs for municipal water supply. During the period 1980 through 1985, diverted flow, measured on a monthly basis, ranged from 15 to 91 cfs (Martinez, 1985). The Otero pipeline, which will transport water directly from Twin Lakes to the Homestake Conduit has been constructed. It is currently being tested prior to beginning opera- tion. When the pipeline becomes functional, the municipal water for Aurora and Colorado Springs will no longer be discharged Into Lake Creek and into the Arkansas River. At that time, the flow in Lake Creek available to dilute metals in the Arkansas River will be reduced and the contamination may extend further downstream. The Parkville Water District supplies water to Leadville, String- town, Silver Hills, and Matchless and has 1,307 paying customers (Herald Democrat, 1985). Its sources of water include th Canterbury Tunnel wells, the Elkhorn Shaft, and Big Evans Gulch Reservoir. There are five reservoirs along Evans Gulch, but three of them are considered emergency sources and are not normally used by the Parkville Water District. The primary water source during the summer is the Big Evans Reservoir. Another, much smaller reservoir on Evans Gulch is also used. During the winter months, the Canterbury Tunnel, located 1

6-8 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION mile north of Leadville toward Climax, Colorado (see Figure 6.1) is used as the major source of raw water because it is warmer. Average flow from the water treatment plant is 0.15 MGD (0.23 cfs). Outside of the Parkville Water District well, water is used for domestic supplies, irrigation, commercial, municipal, and industrial uses. EPA identified 33 existing wells located near California Gulch. A number of people in Stringtown and on the lower part of California Gulch have used for domestic well purposes. These wells are discussed in Chapter 5. NATURE AND EXTENT OF CONTAMINATION Past Studies Several surface water studies were conducted in the upper Arkansas River basin prior to 1984. Wentz (1974) conducted a study to determine the extent of contamination by acid mine drainage in Colorado's streams. He identified approximately 69 miles of the Arkansas River basin that had been affected by acid mine drainage (Table 6.1). A study was conducted by Moran and Wentz (1974) to determine the extent to which mining activities had affected the water quality in 18 mining areas in the mineral belt of Colorado, including the Leadville district. The results of their study identified several sources of hazardous metals and acid mine drainage contaminaition to the Arkansas River: California Gulch, including the Yak Tunnel, other draining mines, and tailings; . St. Kevin Gulch; . Leadville Drain;^ Iowa Gulch from Sherman Tunnel downstream, including below the Black Cloud Mine; and

6-9 TABLE 6.1 ARKANSAS RIVER BASIN AFFECTED BY METAL-MINE DRAINAGE(l) Estimated Miles of Stream Point or Approximate Stream Tributary(ies) Reach Affected Affected(2) Arkansas River Confluence of East Fork and 15 Tennessee Creek to lake Creek California Gulch Source to mouth 8 East Fork Above Climax to below French Gulch 10 and Leadville Drain to mouth Evans Gulch Near mouth 5 Leadville Drain Source to mouth 1 Iowa Gulch Source to mouth 11 Lake Creek Confluence of North and South Forks 3 to below Crystal Lake Creek South Fork Lake Mouth Creek t Pine Gulch Above West Pierce Gulch - 5 Tennessee Creek St. Kevin Gulch to mouth 3 St. Kevin Gulch Mouth 2 (1) Wentz, Dennis A. 1974. (2) Distances are shown to the nearest mile; distances less than 1 mile are shown as 1 mile. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

Evans Gulch (which only flows part of the year). Moran and Wentz identified the Yak Tunnel as the main contributor of metals to California Gulch and the most important source of contamination to the Arkansas River. Of all the sources of contamination, it is believed that the major contributor of metals and acid to the Arkansas River is California Gulch, which results in a significant deterioration of water quaity at least down to the inflow of Lake Creek (Moran and Ventz, 1974). Further degradation of the Arkansas River could result if water diversions are implemented on Halfmoon Creek and .the Lake Fork of the Arkansas River. Any reduction of the flow of these streams would be detrimental to the dilution capacity which helps to dilute the metals and acid from the California Gulch. A study by LaBounty et al. (1975) examined the magnitude of metal contamination in the upper Arkansas River from above the inflow from the Leadville Drainage Tunnel to the confluence with Lake Creek. LaBounty et al. (1975) collected samples of surface water, sediment, macroinvertebrates, and fish. Their findings identified three main sources of hazardous metal contamination: Leadville Drain; . California Gulch; and Diffuse sources of heavy metal between California Gulch and Lake Creek. Of these sources, hazardous metal discharge (primarily copper, cadmium, and zinc) from California Gulch were identified as the most damaging to the aquatic life in the Arkansas River. The Bureau of Reclamation conducted a limnology study on a 30 kilometer (km) section of the upper Arkansas River to determine the effects of heavy metals pollution on the distribution of the aquatic 6-11 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION macrofauna (Rolme and Boehmke, 1981). They evaluated fish populations to determine their density and heavy metal content of their tissue. Physical and chemical water parameters were measured and aquatic macroinvertebrates were collected. Roline and Buehmke (1981) identified the Leadville Drainage Tunnel, California Gulch, and a number of intermittent flows entering between Lake Fork and Lake Creek as the sources of hazardous metal contamination to the Arkansas River. After examining water quality, macroinvertebrate species diversity, fish populations, and metal accumulation in fish tissue, their report concluded that metal pollution of the upper Arkansas River near Leadville, Colorado is very severe, and that conditions for aquatic life are generally poor. Furthermore, Roline and Boehmke (1981) state that historical river flows which dilute hazardous metal concentrations were lower than those occurring since transmountain diversions began. It is possible that hazardous metals concentrations in the Arkansas River were greater In the past. Any substantial reduction or elimination of the freshening inflows will result in additional a degradation of water quality and adversely affect the aquatic organisms. McLaughlin (1981) showed that concentrations of hazardous metal (except nickel) rise dramatically in the Arkansas River below the confluence with California Gulch. A dramatic decrease in hazardous metals concentrations was found in the Arkansas River below the confluence of Lake Fork (1.5 miles below the gulch), but the levels of cadmium and zinc remained high. The Yak Tunnel was identified as the primary source of acidity and metals in California Gulch. Water quality data was retrieved from the STORET system for the Arkansas River near Canon City to below Leadville, Colorado. The requested parameters obtained were pH, total alkalinity, total hardness, and total concentrations of cadmium, copper, zinc, lead, iron, and manganese. Table 6.2 is a summary of the data collected from 1977 to 1985.

6-12 TABLE 6.2 WATER QUALITY DATA FROM STORET ON THE ARKANSAS RIVER FROM LEADVILLE TO NEAR CANON CITY (mg/1) Parameter PH Cadmium Copper Lead Zinc No. No. No. No. No. Year /area Samples Max. Hln. Mean i^BHH^^^^^Samples ^ Max. Mln. Mean Samples Max. Mln. Mean Samples Max. Mln. Mean Samples Max. Mln. Mean 1977 , Lead vl lie 4 8.5 8.2 8.3 4 1.8 0.0 0.45 4 28.0 8.0 16.5 4 39.0 6.0 24.0 4 650.0 0.0 325'.1 0 Sal Ida 3 8.3 7.4 7.7 4 9.0 0.0 2.4 3 21.0 8.0 13.0 4 22.0 0.0 12.5 4 150*. 0 0.0 87 '. 5 Canon City 3 7.9 7.3 7.6 3 0.0 0.0 0.0 3 7.0 0.0 4.3 3 105.0 0.0 35.0 3 100.0 20.0 66.6 1978 Leadvtlle 2 7.9 7.2 7.6 3 3.6 1.4 2.5 3 30.0 21.0 24.0 4 18.0 12.0 15.3 4 960.0 640.0 805.0 Saltda 2 8.0 7.7 7.9 1 1.4 1.4 1.4 1 9.0 9.0 9.0 1 0.0 0.0 0.0 1 90.0 90.0 90.0 Canon City 6 9.1 6.5 8.0 5 49.0 0.5 11.6 6 39.0 0.0 12.6 6 140.0 0.0 29.3 6 860.0 20.0 286.7 1979 Leadvllle 5 7.8 6.6 7.2 6 6.9 1.0 2.5 6 26.0 11.0 16.8 6 54.0 0.0 15.3 6 1100.0 240.0 568.3 Sallda — — . — __ -_ — — __ — — — __ — — — — — . — -- Canon City 6 8.4 7.8 8.2 5 3.4 0.3 1.0 6 10.0 6.0 7.0 6 9.0 0.0 3.0 6 140.0 34.0 78.3 1980 Leadvllle 5 8.0 7.0 7.5 6 2.1 1.4 1.7 6 15.0 5.0 9.0 6 24.0 5.0 10.8 6 800.0 350.0 486.7 Sallda 5 8.4 7.7 8.0 5 1.1 0.0 0.5 6 13.0 0.0 4.8 6 39.0 0.0 11.8 6 480.0 120.0 196.7 Canon City 6 8.3 7.4 7.8 6 2.6 0.3 1.1 6 46.0 5.0 14.5 6 110.0 0.0 26.8 6 480.0 60.0 158.3 1981 Leadvllle 7 8.0 7.4 7.7 7 7.0 2.1 3.5 8 23.0 7.0 12.0 8 81.0 8.0 35.3 8 2400.0 400.0 845.0 Sallda 5 8.3 7.4 7.8 5 1.0 0.4 0.74 5 18.0 5.0 7.6 5 34.0 5.0 14.2 5 140.0 100.0 124.0 Canon City 5 8.1 7.3 7.8 6 4.0 0.3 1.4 6 12.0 5.0 6.7 6 77.0 9.0 26.2 6 520.0 60.0 173.3 1982 Leadvllle 5 7.7 6.9 7.3 5 5.6 0.9 3.2 5 36.0 5.0 24.0 5 47.0 10.0 30.8 5 1400.0 460.0 938.0 Sallda 6 7.9 7.0 7.4 5 1.6 0.3 0.74 6 11.0 5.0 6.5 6 29.0 5.0 15.2 6 320.0 120.0 188.3 Canon City 6 8.2 7.1 7.7 6 1.9 0.3 0.78 6 130.0 5.0 34.8 5 53.0 6.0 24.6 6 400.0 70.0 170..0 1983 Leadvllle 5 7.5 6.9 7.1 5 5.3 1.1 3.1 5 19.0 5.0 15.2 5 23.0 11.0 15.8 5 1200.0 130.0 754.0 Sallda 6 7.9 7.0 7.4 6 1.2 0.5 0.72 6 6.0 5.0 5.3 6 17.0 5.0 8.6 6 210.0 90.0 151.7 Canon City 6 7.8 7.1 7.3 6 1.0 0.5 0.65 6 8.0 5.0 6.2 6 25.0 5.0 10.5 6 210.0 3.0 112.2 1984 Leadvllle 5 8.2 7.1 7.8 5 2.6 1.8 2.3 5 19.0 5.0 11.0 5 32.0 11.0 19.2 5 770.0 430.0 588.0 Sallda 6 8.3 6.7 7.4 6 2.6 0.3 0.89 6 11.0 5.0 6.2 6 28.0 5.0 9.1 6 240.0 120.0 165.0 Canon City 6 8.1 7.1 7.6 6 0.9 0.3 0.6 6 16.0 5.0 7.7 6 21.0 5.0 10.5 6 220.0 75.0 132.8 TABLE 6.2 (CONTINUED) WATER QUALITY DATA FROM STORET ON THE ARKANSAS RIVER FROM LEADVILLE TO NEAR CANON CITY (mg/D Parameter PH Cadmium Copper Lead Zinc No. No. No. Ho. No. Year/area Samples Max. Mln. Mean Samples Max. Mln. Mean Sanples Max. Mln. Mean Samples Max. Mln. Mean Samples Max. Mln. Mean 1985 i Lead vl lie 4 7.9 7.1 7.6 5 10.3 1.6 3.7 5 21.0 5.5 11.3 5 33.0 5.0 12.2 5 1400.0 430.0 672/;0 Sal Ida 5 8.2 5.8 7.5 5 2.3 0.3 0.82 5 13.0 5.0 7.2 5 35.0 5.0 11.0 5 240.0 90.0 154''.0 Canon City 3 8.4 6.3 7.6 4 2.9 0.5 1.2 4 17.0 5.0 9.6 4 42.0 5.0 14.3 4 250.0 50.0 125.0 TOTAL Lead vl lie 42 8.5 6.6 7.5 46 10.3 0.0 2.6 47 36.0 5.0 14.8 48 81.0 0.5 20.5 48 2400.0 0.0 682.7 Sal Ida 38 8.4 5.8 7.6 37 9.0 0.0 0.94 38 21.0 0.0 6.8 39 39.0 0.0 11.4 39 480.0 0.0 154.9 Canon City 47 9.1 6.3 7.8 47 49.0 0.0 2.0 48 130.0 0.0 12.1 48 140.0 0.0 19.2 49 860.0 3.0 1150.4 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION The data show that the above metals are present from Leadville to near Canon City but decreasing in concentration as Canon City is approached. Zinc appears to be the most elevated of the metals (other than iron and manganese) which is of concern due to its mobility and toxicity to aquatic life. CERCLA Investigations EPA and the State of Colorado conducted investigations in the Leadville area during 1984 and 1985. The EPA surface water investigation focused on the California Gulch area to identify sources of contamination. Engineering-Science, working for the states sampled California Gulch to identify contamination sources and the Arkansas River to define the nature and extent of surface water contamination. The sampling locations on Califorinia Gulch and its tributaries for both studies are described in Table 6.3. EPA CERCLA Investigations Surface water sampling was conducted quarterly from June 1984 to November 1985 by EPA contractors. Surface and ground water sampling was closely coordinated from November 1984 to November 1985. The sampling procedures were in accordance with EPA's standard operating procedures for field sampling as found in of the Quality Assurance Project Plan (EPA, 1984). Surface water samples were taken by EPA contractors at 14 surface water or spring sampling locations and six intermittent sampling locations on interittent waterways (Figure 6.3). Twelve of the stations were located along California Gulch and its tributaries and two stations were located on the Arkansas River. Rainfall and snowmelt during the sampling period was only slightly less than during an average year and can be considered representative. A summary of the analyses over the study period is presented in Table 6.4. From November 1984 to November 1985, all mainstream surface 6-15 TABLE 6.3 ES & EPA SURFACE WATER SAMPLING STATIONS ON CALIFORNIA GULCH AND ITS TRIBUTARIES Station Description ES# EPA# 1) Upper California Gulch — SW-1 2) Spring (Parkville Water Line Break) SW-2 3) California Gulch just above CG-10 — Yak Tunnel 4) Yak Tunnel Discharge YT-1SW-03 5) California Gulch just below CG-20 SW-3A Yak Tunnel 6) California Gulch below Tailings CG-30 SW-4 Pond #2 7) California Gulch below Apache CG-40 SW-4A Minerals 8) Starr Ditch at Highway 24, SD-10SW-5 Landfill Road Junction 9) Spring behind Berthod Trucking Co. SW-6 10) California Gulch between Oregon & CG-50 SW-7 Georgia Gulch (behind Berthod) 11) Super 8 Spring — SW-8 12) California Gulch above Stringtown CG-60 — 13) California Gulch above slag pile CG-70 SW-9 (Sec. 27) below Stringtown 14) Spring below slag pile — SW-10 15) California Gulch below slag pile CG-80 16) Leadville Wastewater Treatment — SW-11 Plant Discharge 17) California Gulch below CG-90 Leadville STP 18) California Gulch in Molleur's CG-95 Pasture 19) California Gulch above confluence CG-100 SW-12 with Arkansas River TABLE 6.3 (CONTINUED)

Station Description E§£ - EPA# 20) Oregon Gulch OG-10 SWI-1 21) Leadville Storm Drain — SWI-2 22) Georgia Gulch Culvert — SWI-3 23) Pawnee Gulch Culvert — SWI-4 24) Airport Road Gulch Culvert — SWI-5 25) Malta Gulch Culvert — SWI-6 Table 6.4 EPA Surface Water Data Summary (mg/D Nov 1984 March 1985 June 1985 Sept 1985 Nov 1985 Dies. Total Dlsa. Total D188. Total Dlsa. Total Dlss. Total SW-01 As ND ND Dry ND ND Dry Dry Be ND ND 0.0026 0.0015 Cd 0.012** 0.011** 0.081** 0.075** Ct ND ND ND ND Cu 0.025* 0.044* 0.644 0.600 Nl ND ND 0.027 0.022 Pb 0.149 12.600 0.382 0.364 Zn 1.506 1.823 12.700** 11.600* CN •*~* ND — — ND SW-02 As ND ND Dry Dry Dry Dry Be ND ND Cd ND ND Cr ND ND , Cu ND* 0.015* HI ND ND , Pb 0.025 13.600 Zn 0.111 0.193 CN — - ND SW-03 As ND 0.011 ND* ND* 0.003 0.0091 0.0045 0.016 ND 0.0077 Be ND ND ND 0.0016 0.0024 0.0014 0.0007 0.0011 ND 0.0006 Cd 0.244** 0.207** 0.169** 0.195** 0.552** 0.520** 0.310** 0.304** 0.270** 0.225** Cr ND 0.015 0.0035 ND 0.012 0.0072 ND 0.005 0.0048 0.0059 Cu 0.736* 0.980* 0.437 0,731 5.970** 5.730** 1.490** 1.650** 0.714 1.070** Nl 0.033 0.073 0.021 0.029 0.087 0.072 0.052 0.050 0.048 0.046 Pb ND 0.020 ND 0.0091 0.116** 0.117** ND* 0.035 ND* 0.028 Zn 58.250** 56.460** 43.700** 50.100** 109.000** 101.000** 70.000** 69.300** 65.900** 64.300** CN — ND ND • ND — ND* ND* Table 6.4 (Continued) EPA Surface Water Data Summary («g/D Nov 1984 March 1985 June 1985 Sept 1985 Nov 1985 Pise. Total Piss, Total DtBS. Total Pisa. Total Dtsa. Total SW-03A As ND* 0.010* ND 0.0078 0.0053 0.014 «» «»-~ Be ND 0.0014 0.0025 0.0015 0.0007 0.0009 Cd 0.177 0.199 0.429 0.390 0.310 0.302 — — Cr ND ND 0.0049 0.0065 ND 0.0054 Cu (1) 0.456 0.736 4.670 4.280 1.520 1.580 — — Nl 0.020 0.035 0.065 0.055 0.049 0.048 Pb ND 0.0095 0.218 0.239 ND* 0.062 — — Zn 46.100 50.600 82 .100 75.000 69 .300 68.000 — —— CN ——— ND _— ND ••— ND* ~~ ~ SU-04 As NO* 0.013* ND* 0.0088* ND 0.0073 ND 0.015 ND 0.010 Be ND ND ND 0.0019 0.0024 0.0012 ND 0.0013 ND 0.001 Cd 0.201** 0.178** 0.167** 0.198** 0.431** 0.395** 0.308** 0.306** 0.230** 0.230** Cr ND ND ND ND 0.0048 0.0049 ND ' ND' 0.0059 0.0057 Cu 0.072 0.810 0.049 0.961 4.610** 3.980** 1.070** 1.610** 0.156 1.180** Nl 0.032 0.042 0.024 0.037 0.067 0.056 0.051 0.044 0.045 0.046 Pb 0.006* 0.032* ND 0.122** 0.266** 0.270** ND* 0.058 ** ND* 0.083** Zn 52.920** 50.390** 42.600** 51.000** 85 .300** 75.900** 69 .500** 68.000** 62,100** 62.600** CN — ND — ND — ND — ND* — ND* Table 6.4 (Continued) EPA Surface Water Data Summary (mg/1) Nov 1984 Harch 1985 June 1985 Sept 1985 Nov 1985 Dlss. Total Dlss. Total Dlss. Total Dlsa. Total Dlss. Total SU-4A As ND 0.0068 Be ™— ND 0.0008 Cd 0.265** 0.200** Cr — ND 0.0072 Cu -- -- 0.122 0.778 HI — (1) 0.044 0.042 Pb — ND* 0.055 Zn 63.200 56.100 CN ND* SV-05 As ND* ND* ND* 0. 042* ND 0.0067 Dry Dry Be ND ND ND 0. 0013 0. 0017 0.0015 Cd ND ND 0.005 0. 017** 0. 285** 0.261** Cl ND ND ND 0. 0059 ND ND Cu ND 0.030 0.014 0. 147 0. 531 0.482 Nl ND ND ND ND 0. 022 0.021 Pb ND* 0.021* ND 0. 967** 0. 210** 0.235** Zn 0.362 0.599 1.620 3. 170 37. 100** 33 .400** CN — ND — ND — ND SW-06 As — — ND* ND* ND ND ND ND Be — — ND 0. 0011 ND ND ND ND Cd — — 0. 177**0. 199** 0. 166** 0. 155** 0.132** 0.118** Cr — — ND ND ND 0.0044 ND 0.0059 Cu — — 0.056 0. 058 0. 020 0.019 0.028 0.029 Nl 0.038 0. 042 0. 063 0.052 (1) 0.072 0.070 Pb — — 0. 175**0. 240** 0. 138** 0.134** 0.036 0.078** Zn — — 45 .700** 51 .300** 56. 200** 50 .800** 69.500** 63.300** CN — — — ND — ND — ND* Table 6.4 (Continued) EPA Surface Water Data Summary

Nov 1984 March 1985 June 1985 Sept 1985 Nov 1985 Dies. Total Dlaa. Total Dlss. Total Dlss. Total Dlss. Total SW-07 As ND* 0.109* ND 0.0068 ND 0.012 ND 0.0066 Be ND 0.0043 0.0022 0.0012 0.0008 0.0011 0.0006 0.0011 Cd 0.071** 0.130** 0.390** 0.382** 0.323** 0.282** 0.250** 0.196** Cr ND 0.0058 0.0047 0.0065 ND 0.0054 0.0062 0.0087 Cu (1) 0.028 1.590** 3.750** 3.620** 1.230** 1.340** 0.487 0.774 Nl 0.012 0.037 0.065 0.058 0.064 0.055 0.058 0.052 Pb ND 3.500** 0.318** 0.372** 0.036 0.105** 0.019* 0.131** Zn 21.200** 37.600** 79.800** 76.600** 76.100** 67 .100** 67.400** 59.000** CH — • ND .... ND ~"~ ND* —•~ ND* SU-08 As ND* ND* ND* ND* ND ND Dry Dry Be ND ND ND 0.0013 ND ND Cd 0.062** 0.048** 0.013** 0.023** 0.043** 0.040 ** Cr ND ND 0.0035 0.0042 ND ND . Cu 0.041 0.056 0.0044 0.030 0.075 0.079 Nl 0.040 ND ND ND ND ND Pb 0.047* 0.150* ND 0.134** 0.046 0.110** Zn 9 .120** 7.915** 3.330 4.040 6.190** 5.660** CN ..•» ND —•" ND — ND Stf-09 As ND ND* ND* 0.146* ND 0.0072 ND 0.016 ND 0.030 Be ND ND ND 0.0043 0.0022 0.0011 ND 0.0011 ND 0.0011 Cd 0.159** 0.125** 0.056** 0.105** 0.405** 0.384** 0.273** 0.270** 0.240** 0.192** Cr ND ND ND 0.017 0.0056 0.0063 ND ND ND 0.009 Cu 0.036 0.441 0.020 1.680** 3.900** 3.470** 0.598 1.250** 0.619 0.847 Nl 0.052 0.113 0.011 0.021 0.064 0.060 0.055 0.049 0.057 0.055 Pb ND* 0.410* ND 4.740** 0.362** 0.420** ND* 0.146** 0.065** 0.202** Zn 48.070** 40.770** 14.200** 27.000** 81.000** 77.300** 65.700** 61 .900** 67.300** 59.200** CN — ND — ND — ND ' ND* — ND* Table 6.4 (Continued) EPA Surface Water Data Summary (mg/1) Nov 1984 March 1985 June 1985 Sept 1985 Nov 1985 Piss. Total Piss. Total Piss. Total Diaa. Total Piss. Total SW-10 As HD ND ND* ND* ND ND 0.0052 0.0061 Be ND ND ND 0.0011 ND ND ND ND Cd 0.091** 0.068** 0.069** 0.080** 0.087** 0.087** 0.044** 0.044** Cr ND ND ND ND ND ND ND 0.0045 Cu 0.025* 0.027* 0.011 0.029 0.018 0.017 0.012 0.019 (1) Nl 0.092 0.030 0.021 0.031 0.026 0.022 0.025 0.026 Pb ND 0.059** ND 0.067** 0.0028 0.0059 0.012* 0.078** Zn 44.170** 34 .730** 35.500** 38.100** 32.500** 32.600** 30 .900** 29.600** CN " '"• ND ——— ND *"* ND — — ND* SW-11 As ND* ND* ND ND ND ND ND ND Be ND ND ND ND ND ND ND ND Cd ND ND ND ND ND ND ND ND Cr ND ND ND ND ND ND ND ND Cu ND 0.024 (1) 0.0047 0.011 0.0093 0.013 0.0047 0.013 Nl 0.023 ND ND ND ND ND ND ND Pb ND* ND* ND 0.0041 ND* 0.031 ND* ND Zn 0.720 0.681 0.188 0.336 0.066 0.200 0.222 0.249 CN — — ND — • 0.016 — — 0.0051* — 0.008* SW-12 As ND ND ND* 0,082* ND 0.0083 ND 0.012 ND 0.0053 Be ND ND ND 0.0032 0.0012 0.0014 ND 0.0006 ND ND Cd 0.047** 0.062** 0.061** 0.099** 0.277** 0.282** 0.060** 0.102** 0.073** 0.079** Cr ND ND ND 0.0039 ND 0.0072 ND ND ND 0.004 Cu 0.013* 0.026* 0.015 1.100** 2.500** 2.560** 0.052 0.541 0.025 0.0305 Nl ND 0.039 0.020 0.021 0.047 0.046 0.020 0.023 0.024 0.025 Pb ND 0.016 ND 2.860** 0.188** 0.386** ND* 0.197** ND* 0.122** Zn 14.710** 20 .170** 19.300** 28.700** 55.600** 57.700** J3 .000** 25.200** 22.400** 26.400** CN — ND — ND — ND — 0.0068* — ND* Table 6.4 (Continued) EPA Surface Water Data Summary (mg/1) Nov 1984 March 1985 June 1985 Sept 1985 Nov 1985 plSB. Total Dies. Total Digs, Total Piss. Total Dlaa. Total SW-13 As NO* ND* ND* ND* ND ND ND ND ND ND Be ND ND ND 0.0011 ND ND ND ND ND ND Cd ND ND ND ND ND ND ND ND ND ND Cr 0.010 ND ND ND ND ND ND ND ND ND Cu ND 0.012 0.0041 0.0038 0.0049 0.004 ND 0.0046 ND 0.006 Nl ND ND ND ND ND ND ND ND ND ND Pb ND* ND* ND ND ND ND ND* ND ND* ND Zn 0.240 0.331 0.569 0.637 '0.109 0.132 0.217 0.353 0.438 0.391 CN ——— ND — — ND — _» ND — — ND* *" ~ ND* SU-14 As ND ND ND* ND* ND ND ND ND ND ND Be ND ND ND 0.0011 ND ND ND ND ND ND Cd ND ND 0.011** 0.023** 0.0073 ND 0.0073 0.0058 0.0048 0.0057 Cr ND ND ND 0.0039 ND ND ND ND ND ND Cu ND* ND* 0.0081 0.189 0.021 0.029 0.0074 0.037 0.0034 0.024 Nl ND 0.044 ND ND ND ND ND ND ND ND Pb ND ND ND 0.439** ND 0.025 ND* 0.0068 ND* 0.0097 Zn 1.317 1.625 2.970 5.630** 0.594 0.709 1.260 2.060 1.740 1.870 CN "•~ ND —~ ND —— ND — ' " ND* — • ND* SWI-01 As Dry Dry 0.090 0.446 Dry Dry Be 0.046 0.053 Cd 0.380** 0.404** Cr 0.154 0.096 Cu 9.520** 10.500** Nl 0.640 0.618 Pb 0.310** 0.320** Zn 263.000** 272.000** CN 0.097 Table 6.4 (Continued) EPA Surface Water Data Summary

Nov 1984 March 1985 June 1985 Sept 1985 Nov 1985 Dlss. Total Disa. Total Dlss. Total Dlss. Total Dlss. Total SUI-02 As ND* 0.094* Dry Dry Dry Be ND 0.0013 Cd 0.011** 0.041** Cr ND 0.014 Cu 0.024 0.308 Nl ND ND Pb 0.015 2.620** Zn 1.390 6.830** CN ND SWI-03 As ND* ND* ND ND ND ND ND ND Be ND ND ND ND ND ND ND ND Cd 0.022** 0.038** 0.030** 0.028** 0.040** 0.037** 0.050** 0.038** Cr ND ND ND ND 0.0066 ND 0.0083 0.0086 Cu (1) 0.0033 0.029 0.0075 0.0096 0.0065 0.009 0.012 0.013 Nl 0.019 0.035 0.023 0.020 0.047 0.044 0.066 0.061 Pb ND 0.057** ND 0.0097 ND* 0.025 0.100** 0.155** Zn 30.000** 49.900** 21.700** 21.600** 52.500** 54.000** 77.100** 72.200** CN ND — ND — ND* — ND* SWI-04 As Cd Dry Dry Dry Dry Dry Cu Pb Zn CN Table 6.4 (Continued) EPA Surface Water Data Summary <»g/D Nov 1984 March 1985 June 198S Sept 1985 Nov 1985 Pisa. Total Plan. Total Dtaa. Total Plae. Total Diga. Total SWI-05 As Dry Dry Dry Dry Dry Cd Cu Pb Zn CN SWI-06 As Dry Dry Dry Dry Dry Cd Cu Pb Zn CN * Spike recovery out of control ** Exceeds EPA primary or secondary drinking wwater standards * No analysis 1) Data outalde quality control guidelines YAK TUNNEL/CALIFORNIA GULCH 2/28/86 "•"" REMEDIAL INVESTIGATION water sampling points in California Gulch exceeded drinking water standards shown in Table 6.5, for at least one of four metals: cadmium, copper, lead, and zinc. In June 1985 in California Gulch below Yak Tunnel, dissolved cadmium was more than 40 times the drinking water standard, dissolved copper and lead were more than 4 times the standard, and dissolved zinc was over 15 times the EPA drinking water standard. Other metals occurring in California Gulch include arsenic, beyullium, chromium, and nicekl. Figures 6.4 through 6.7 show zinc and cadmium surface water profile maps in California Gulch for four samplings by EPA between November 1984 and September 1985. The concentrations of total and dissolved zinc in California Gulch generally increase from above Yak Tunnel (SW-1) to below tailings pond 2 (Stf-4). The concentration remain relatively high until station SW-9, below Stringtown, and then, depending on the season, remain level or decrease slightly to point SW-12, just above the confluence with the Arkansas River. EPA Drinking Water Standards for either cadmium, copper, lead, or zinc were exceeded for all California Gulch samples (Figure 6.4). Cadmium concentrations increase in California Gulch below Yak Tunnel and generally decrease slowly to the point just above the confluence with the Arkansas River. The trends are fairly constant from one sampling to the next, but the concentrations vary seasonally, with the highest cadmium concentrations occurring in June. The range of cadmium concentrations in California Gulch at the confluence with the Arkansas River is 0.047 to 0.295 mg/1 (dissolved cadmium) and 0.062 to 0.290 mg/1 (total cadmium). The Yak Tunnel, upper California Gulch, and Starr Ditch exhibit seasonal trends in hazardous metals concentration (Table 6.6). The highest concentrations of metals occur in June during s no wine It and the lowest concentrations occur during November and March.

6-27 TABLE 6.5 FEDERAL AND STATE WATER QUALITY STANDARDS Colorado Stream Proposed Standards Aquatic Life EPA EPA Colorado EPA for the One Hour Primary Secondary Drinking Drinking Arkansas Acute Drinking Drinking Water Water River Toxic! ty Parameter Units Water Water Standard Standard Segment 3 Guideline* Arsenic mg/1 0.050 0.050 0.050 0.050 — Barium mg/1 1.000 1.500 1.000 — — Cadmium mg/1 0.010 0.005 0.010 0.003 0.0018 Chloride mg/1 250 • — — — Chromium mg/1 0.050 0.120 0.050 0.100 — Copper mg/1 1.000 — — 0.063 0.0092 Cyanide mg/1 — — — — — Iron mg/1 0.300 — — 4.000 — Lead mg/1 0.050 0.020 0.050 0.025 0.0340 Manganese mg/1 0.050 — — 2.000 — Mercury mg/1 0.002 0.003 0.005 0.05 — Nickel mg/1 — — — 0.050 — Nitrate mg/1 10 10 10 — — TABLE 6.5 (CONTINUED) FEDERAL AND STATE WATER QUALITY STANDARDS Colorado Stream Proposed Standards Aquatic 'Life EPA EPA Colorado EPA for the One Hoftr Primary Secondary Drinking Drinking Arkansas Acute Drinking Drinking Water Water River Toxicity Parameter Units Water Water Standard Standard Segment 3 Guideline* Selenium mg/1 0.010 — 0.045 0.010 0.020 — Silver mg/1 0.050 — — 0.050 0.1 — Sulfate mg/1 — 250 ' — — — TDS mg/1 — 500 — — — — Zinc mg/1 — 5.000 — — 4.600 0.1800 * For selected metals at a water hardness of 50 mg/1 CaCO- from U.S. Environmental Protection Agency 1980, 1985a, 1985b, and 1985c. SAMPLES

265 - JUKJE '85

«50 •- ISO - 115 - 110 - I II \OS - wig/1

TAIUM6& SEPT 'as 1 I •ng/l 30- o - SW-tl SW-IO 6W-9 SWl-3 *»I-V 6SA/-1 YAK TUHMG.U FIGURE 6.4 DISSOLVED ZINC IN CALIFORNIA GULCH (ERA DATA) NOV I U 45- iO- 15- 0- fcW-tl sw-10 s.w-6 sw-s STAWPITCH? YAK.

MARCH '85 TAIUMfaS ftJMPS. 60 - 1 U 30- 15 - O -

iw fiw/l-*' <-'«- STARR YAK.

FIGURE 6.5 DISSOLVED ZINC IN CALIFORNIA GULCH (EPA DATA) I.OOO - T U 0.500- 0.150- 0- + * * * ^ + ' — r-* SM'tl SW-II SW-'lO fcu^l «*o-8 ftkM-3 6W-7 &u>'-5 6W-4- fiM>3Ali Sw-l *TAdR e. , « J V- . . . WTCtxrtil H yA5W-4K ' »^SW-« «Z•

I.00O- MAPC1 •f^r^rH , 'Bw^5 TAJI_l»4tt4 POMPS O.1SO- m /l O.500- 1 U 3 o.tso- 0- J ______,_____ ,*• ——— -< ——————— • + i !•• I yilibi iiTb 6 flW*!• ! dm*IIO Ift^* H Illlfti)*0 &cUl*& 9***"7 £rf*J''l 5 fitO—^4* |llSu^**3A ^^^m*! l OlTCH %<* **''* TUMU6L i.ooo- SEPT '85 TAJUW6S PtoNP9 O.TSO- VQ/l O.SDO- ^ u 0,150 • O- 1 1 PITCH TUtJ»C(. FIGURE 6.6 TOTAL CADMIUM IN CALIFORNIA GULCH (EPA DATA) GOt-04 SAHPl.CS 1.000 0.150 O.500 4 U 0.150 O- sw-ti ew-io *w-i 5m. e ew-7 tw-s em-f SW-I tiTAftOcrtHR 1.000 O.150 li O.1SO O

6k»-l| %u>-IO Qui-4 9u>-6 ftW-7 Sui-5 «u>-3A3A A AV 'STAXorreiiK ) / i.ooo ,0.160 I O.SCO U "V o.wo O Su)-8I IS*Ji - I I ^ I T n i UlTCH I.OOO SEPT 'ffi? TAJUWCA O.1SO U mg /1 0.5QO 0.150 O SWI-II f(t PITCH FIGURE 6.7 DISSOLVED CADMIUM IN CALIFORNIA GULCH (ERA DATA) Table 6.6 EPA Surface Water Data Summary (B.g/1) June 1985(2) Nov 1984 March 1985 May 1985 June 1985(1) (6/12/85) Aug 1985 Sept 1985 Nov 1985 Diss. Total DlSB. Total Dlss. Total Dlss. Total Dlss. Total Dlss. Total Dlss. Total Dlss. Total Upper California Gulch Cd 0.012 0.011 Dry Dry 0.197 0.180 0.081 0.075 0.084 0.085 Dry Dry Dry Dry Dry Dry Cu 0.025 0.044 1.750 1.700 0.644 0.600 0.633 0.590 Pb 0.149 12.600 0.757 3.000 0.382 0.364 0.473 0.513 Zn 1.506 1.823 28.667 26.333 12.700 11.600 13.000 12.667 Yak Tunnel Cd 0.244 0.207 0.169 0.390 0.403 0.367 0.552 0.520 0.523 0.547 Access denied 0.310 0.304 0.270 0.225 Cu 0.736 0.980 0.437 4.280 0.067 0.243 5.970 5.730 4.533 4.367 1.490 1.650 0.714 1.070 Pb ND(3> 0.020 ND 0.239 ND 0.093 0.116 0.117 ND ND ND 0.035 ND 0.028 Zn 58.250 56.460 43.700 75.000 81.000 72.333 109.000 101.000 107.000 108.333 70.000 69.300 65.900 64.300 Start Ditch Cd ND ND 0.005 0.017 1.997 1.800 0.285 0.261 0.230 0.240 ND 0.004 Dry Dry Cu NO 0.030 0.014 0.147 3.973 3.800 0.531 0.482 0.440 0.465 0.040 0.063 Pb ND 0.021 ND 0.967 1.250 2.500 0.210 0.235 1.100 1.750 ND 0.388 Zn 0.362 0.599 1.620 3.170 259.333 242.333 37.100 33.400 28.500 30.000 0.092 0.775 (1) EPA data (2) ES data (3) ND « not detected YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

Surface water and shallow ground water samples collected at the same time at proximal sampling points by the EPA contractor indicate a strong interconnection between the two regimes. The relationship between surface water and ground water in the gulch was discussed in Chapter 5. Mass loadings calculations for copper, cadmium, lead, and zinc for the sample periods (Tables 6.7 to 6.10) were used to identify sources of hazardous substances in California Gulch. To assist in the interpretation, cadmium and zinc mass loading have been plotted over the surface profile of the gulch. Mass loading was also graphed on a seasonal basis, showing all five sampling periods' mass loads for stations on California Gulch. Both dissolved and total concentrations have been plotted. Results for zinc and cadmium are shown in Figures 6.8 and 6.9, respectively. Conclusions from the mass loading calculations include: Yak Tunnel is the major source of cadmium, copper, and zinc in California Gulch. There is a large difference in seasonal mass loadings, with peak loads for the sampling periods occurring in June 1985. In summary, it appears that the major contributors of flow in California Gulch are the Yak Tunnel and the Leadville STP. The Yak Tunnel is the major contributor of metals to California Gulch. Flow and contaminants are also contributed by tributary drainages such as Starr Ditch and Oregon Gulch for limited periods during seasonal runoff and storm events. Surface water flow down California Gulch is the principal contaminant transport system for heavy metals to the Arkansas River. The data collected by EPA supports the conclusions drawn from the Engineering-Science study.

6-35 TABLE 6.7 TOTAL CADMIUM LOADING VALUES FROM EPA DATA (lb/day) November 1984 March 1985 June 1985 September 1985 November 1985 SW-1 0.02 Dry 1.08 Dry Dry SW-2 NDL Dry Dry Dry Dry SH-3 1.23 1.11 7.57 2.24 1.33 SW-3A (1) , 1.06 7.40 2.20 (2) SW-4 0.85 ' 0.59 13.09 2.03 0.86 SW-4A (2) (2) (2) (1) 1.02 SW-5 NDL 0.15 0.49 Dry Dry SW-6 (2) 0.04 0.07 (1) 0.01 SW-7 (1) 1.92 7.99 1.93 1.13 SW-8 0.003 (2) 0.22 Dry Dry SW-9 1.60 (2) 11.92 1.86 1.31 SU-10 0.04 0.01 0.01 (2) (1) SW-11 NDL (1) NDL NDL SW-12 0.51 2.68 5.85 1.43 0.83 SWI-1 Dry Dry 0.087 Dry Dry SWI-2 Dry 0.01 Dry Dry Dry SWI-3 (1) 0.004 0.005 0.01 0.004 NDL = no detectable loading (1) Water quality data outside quality control guidelines. (2) No water quality data or flow data. TABLE 6.9 TOTAL LEAD LOADING VALUES FROM EPA DATA (Ib/day) November 1984 March 1985 June 1985 September 1985 November 1985 SW-1 21.05 Dry 5.24 Dry Dry SW-2 11.00 Dry Dry Dry Dry SW-3 0.12 0.05 1.70 0.26 0.17 SW-3A (1) 0.05 4.53 0.45 (2) SW-4 0.15 0.36 8.95 0.38 0.31 SW-4A (2) (2) (2) (1) 0.28 SW-5 0.07 0.83 0.44 Dry Dry SW-6 (2) 0.05 0.06 (1) 0.004 SW-7 (1) 51.69 7.78 0.72 0.76 SW-8 0.008 (2) 0.60 Dry Dry SU-9 5.26 (2) 13.04 1.01 1.38 SW-10 0.03 0.01 0.001 (2) (1) SW-11 NDL (1) 0.02 0.27 SW-1 2 0.13 77.39 8.01 2.76 1.28 SWI-1 Dry Dry 0.07 Dry Dry SWI-2 Dry 0.71 Dry Dry Dry SWI-3 (1) 0.006 0.002 0.007 0.02 (1) Water quality data outside quality control guidelines. (2) No water quality or flow data. TABLE 6.10 TOTAL ZINC LOADING VALUES FROM EPA DATA (Ib/day) November 1984 March 1985 June 1985 September 1985 November 1985 SW-1 3.05 Dry 166.94 Dry Dry SW-2 0.16 Dry Dry Dry Dry SW-3 334.75 286.24 1469.85 511.73 381.23 SW-3A (1) 270.01 1422.96 494.80 (2) SW-4 241.73 151.19 2515.97 450.82 232.82 SW-4A (2) (2) (2) (1) 287.26 SW-5 1.87 2.73 63.01 Dry Dry SW-6 (2) 11.06 21.90 (1) 3.41 SW-7 (1) 555.30 1601.95 459.32 340.27 SW-8 0.43 (2) 31.12 Dry Dry SW-9 523.01 (2) 2399.89 427.06 405.24 SW-10 20.59 6.16 5.27 (2) (1) SW-11 4.15 (1) 1.68 1.71 SW-1 2 165.25 776.56 1197.36 353.15 276.05 SWI-1 Dry Dry 58.64 Dry Dry SWI-2 Dry 1.84 Dry Dry Dry SWI-3 (1) 5.38 3.49 14.55 7.78 NDL = no detectable loading (1) Water quality data outside quality control guidelines. (2) No water quality or flow data. DISSOLVED Cd (Ib/day) TOTAL Cd (Ib/day) o» O)

O O>

CO CO 3o>8r H H O. cz z CsO Zfeg ••_• ao•> m CO m co am .<*o >O w® THI

cO Or- f J TIJD Oz N ^lOOO O

sw-ia tW-f I aw-* •w-r «w-« •W-»A STATION NUMBER

ZO N 11O1 <010000 - (50

3w- I »W-I I 8W-7 3W-8 STATION NUMBER

FIGURE 6.9 ZINC MASS LOADINGS IN CALIFORNIA GULCH, EPA DATA, JUNE 1985 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Engineering-Science CERCLA Investigations In 1985, from May through August, surface water samples were collected by Engineering-Science along California Gulch, the Arkansas River, and their tributaries. During May and June, samples were collected along California Gulch. August sampling included California Gulch and the Arkansas River down to Granite. Figures 6.10 and 6.11 SHOW sample locations. The sampling program was designed to accomplish the following objectives: Sample Yak Tunnel flow to evaluate seasonal variations in flow and water quality, so that values for metals loadings could be calculated. . Sample water quality of California Gulch and its tributaries to determine the contributions of heavy metals from various sources. Sampling during lower flows, in addition to the summer sampling, was conducted to determine seasonal variation in water quality. Measure flow along California Gulch and its tributaries to identify losing and gaining stretches of the stream during average and lower flow conditions. Measure the flow in the Arkansas River and sample water quality upstream and downstream of California Gulch to determine the impacts of flow from California Gulch on water quality in the Arkansas River. Sample flow and water quality on the Arkansas River downstream of California Gulch to define the extent of contamination in the river. Sample major tributaries to the Arkansas River to identify the water quality and flow of the major contributing streams.

6-42 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Surface water quality samples were collected using the Equal Width Increment (EWI) method and a depth integrating sampler unless the stream flow was so low that a representative sample could not be obtained. For stations where depth integrating was not possible, grab samples were collected at regular intervals across the stream with a 1-liter glass bottle. Care was taken during collection of grab samples not to disturb sediments on the bottom of the stream. The samples collected from each stream width at a sampling location were composited in a churn splitter. At each of the sample stations, flow, pH, and conductivity were measured, and filtered (dissolved) and unfiltered (total) water quality samples were collected. All sampling by Engi- neering-Science followed the procedures outlined in the QAPP (1985). Triplicate samples were collected at the majority of the sampling sites (see Engineering-Science Appendix D). The arithmetic mean value of the triplicates is used in this discussion. Flow was measured using either a Price flow meter, a Pygmy flow meter, or a portable flume. Extremely low flows «0.1 cfs) were estimated by measuring surface velocity and the cross sectional area of the stream. Stations were sampled from downstream to upstream on the Arkansas River and California Gulch. During the August sampling, the Arkansas River samples were collected before the sampling on California Gulch was begun. The only exception to this procedure was station AR-100, the Arkansas River at Granite. The data from this station is not considered in the water quality analysis because the dissolved zinc concentration is more than 15 percent higher than the total zinc concentration. Cross contamination of sampling equipment is suspected. Preparation of samples for lab analysis introduces variablility into the lab results. All sample results presented here should be considered accurate to plus or minus 15 percent. The samples appear to have higher concentrations of dissolved metals than total metals. However, the actual numerical concentration may be 15 percent higher or

6-45 --"- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION lower than the number reported. For all the data presented where the reported dissolved metal concentrations exceeds the total concentration for the same metal, (except station AR-100) the total and dissolved concentrations are within 15 percent of one another and, therefore, are not considered as actually different numbers. The surface water sampling program did not include "background" or "reference" water quality stations. Background water quality stations (stations that have not been affected by mining) do not exist in the Leadville area. The same mineralization that attracted miners to Leadville has become the source of contamination in California Gulch and the Arkansas River. The mineralized regions in the area have all been disturbed to some extent by past mining activities. To compare the water quality that currently exists in California Gulch to the water quality in drainages that have a similar geology but undisturbed by mining activities is not possible. In order to facilitate discussion of contaminant levels and sources, California Gulch and the Arkansas River have been divided into reaches as illustrated in Figures 6.12 and 6.13. A comparison of ES and EPA sampling locations on California Gulch can be found in Table 6.1. California Gulch Reaches The variation of metal levels and other parameters at different stations along California Gulch are depicted on Figures 6.14 through 6.25 for May, June, and August sampling. Changes in parameters are discussed by reach. Stream flow was measured in May, June, and August in California Gulch and its tributaries to attempt to identify the sections of the stream that are contributing water to the uppermost aquifer in Calif- ornia Gulch. In May, the Yak Tunnel reach was shown to lose 0.81 cfs of flow. California Gulch gained 1.60 cfs of flow through the tailings

6-46 FIGURE 6.12 CALIFORNIA GULCH REACHES

CALIFORNIA GULCH UPPER STRINGTOWCALIFORNIN TOA ARKANSAGULCH THROUGS RIVEHR (5) THROUGH TAILINGSC3) CALIFORNIA GULCH (1) CALIFORNIA GULCH NEAR CALIFORNIA GULCH STAROREGOR N DITCGULCH HAN (4D) AT YAK TUNNEL(2)

ANDDENVER RIO GRANDS

SP-IO California Gulch AR-IO LEGEND AR-21 O SAMPLE LOCATION SP SPRING CG CALIFORNIA GULCH SO STARR DITCH OG OREGON GULCH AR ARKANSAS RIVER t£*3 TAILINGS POND FIGURE 6.10 SURFACE WATER SAMPLING LOCATIONS ALONG CALIFORNIA GULCH

DENVER ANDKIOGRANDEWESTERN

SP-IO California Gulch LEGEND O SAMPLE LOCATION SP SPRING CG CALIFORNIA GULCH SD STARR DITCH 06 OREGON GULCH AR ARKANSAS RIVER [SSJ TAILINGS POND NORTH One Mile

LF-1CX AR-40 AR-45 IG-10

LEGEND SAMPLE LOCATION CALIFORNIA GULCH ARKANSAS RIVER LAKE FORK LAKE CREEK EMPIRE GULCH

FIGURE 6.11 SURFACE WATER SAMPLING LOCATIONS ALONG THE r\. GRANITE ARKANSAS RIVER Turquoise Lake ^^•^^^ NORTH i- -4 One Mile RiverArkansas UPPER ARKANSAS RIVER TO CALIFORNIGULCH {1A)

CALIFORNIA GULCH TO LAKE FORK (2)

AR-50 AR-60-^

LAKE FORK TO LAKE CREEK(3) LEGEND o SAMPLE LOCATION CG CALIFORNIA GULCH AR ARKANSAS RIVER LF LAKE FORK LC LAKE CREEK Arkansas River EG EMPIRE GULCH

Lakes Reservoir AR-80 AR-90

Arkansas LAKE CREEK TO River GRANITE (4) FIGURE 6.13 ARKANSAS RIVER REACHES GRANITE 0.290 0.200 FIGURE 6.14 0.270 0.180 6.334 3.127 CADMIUM 4.4 3.2 IN CALIFORNIA GULCH 3.7 3.3 (May 1985)

LEADVLLE Stray Horse Gulch Yak Tunnel W-H DitchStarr

STRINQTOWN U.S. HIGHWAY 24

California Gulch California Gulch TAILINGS POND SAMPLE SITES AR-10 80-10 OQ-10 YT-10 CG-100 STATION <0.004 2.00 0.080 0.400 DISSOLVED (mg/D* <0.009 1.80 0.078 0.360 0.370 TOTAL (mg/l) * 6.2 not 39 not 0.34280 SEDIMENT (mg/kg) sampled 6.9 sampled 11 FLOLOAWD (Ibs/day(cfs) ) 0.71 6.0 PH 2.9 IScaln Milee s 4.0 * 15% VARIABILITY IN CALIBRATION CG-1OO 0.210 FIGURE 6.15 0.210 CADMIUM IN CALIFORNIA GULCH (June, 1985)

AR-10 AR-20 8D-10 OQ-10 YT-10 SP-10 CQ-100 STATION 0.230 0.390 0.520 0.26 0.210 DISSOLVETOTAL D(mg/l (mfl/0) ** 0.240 0.410 0.550 0.24 0.210 SEDIMENT (mg/kg) not not LOAD (Ibs/day) sampled samplee 0.85 0.01 6.7 6.9 FLOW (cfa) 0.66 0.005 2.3 6.0 PH 3.6 2.8 3.7 5.5 IScaln Milee s 4.8 16% VARIABILITY IN CALIBRATION CQ-100.1170 FIGURE 6.16 0.156 CADMIUM IN CALIFORNIA GULCH

AB-10 AR-2O SO-10 OQ-10 VT-10 8P-10 CQ-100 STATION <0.004 0.006 <0.004 0.117 DISSOLVED (mg/D* <0.004 0.005 0.004 NORTH 0.156 TOTAL (mg/l) * !_.£ 16 no not no SEDIMENLOAD (Ibs/dayT (mg/kg) ) 1.2 flow sampled flow 1/2 1.5~ FLOW (cfs) 45 43 0.12 1.8 PH 7.0 6.9 7.5 IScaln Milee s 6.8 # 16% VARIABILITY IN CALIBRATION FIGURE 6.17 not COPPER sampled IN CALIFORNIA GULCH (May 1985)

LEADVILLE Stray Horn Gulch Yak Tunnel

STRINQTOWN U.S. HIGHWAY 24 Co//for/} i a Gulch California Gulch TAILINGS POND SAMPLE SITES AR-10 OQ-10 YT-10 CG-100 STATION <0.003 1.23 0.067 0.880 DISSOLVED (mg/0* <0.003 1.20 0.24 0.900 TOTAL (mg/l) « 18 not not 320 SEDIMENT (mo/kg) samplee sampled 29 FLOLOAWD (Ibs/day(cfa) ) 6.0 PH IScaln Milee s 4.0 * 15% VARIABILITY IN CALIBRATION FIGURE 6.18 COPPER IN CALIFORNIA GULCH

AH-10 AR-20 8D-10 OO-10 YT-10 8P-10 CO-100 STATION 0.530 9.40 4.50 0.200 1.20 DISSOLVED (mg/0* 0.730 9.20 4.40 0.193 NORT*H TOTAL (mg/l) * not not 1.30 SEDIMENT (mg/kg) sampled sampled 1.7 0.25 53 1/2 41 FLOLOAWD (Ibs/day(cfs) ) 0.66 0.005 2.3 6.0 PH 3.6 2.8 3.7 5.5 IScaln Milee s 4.8 * 15% VARIABILITY IN CALIBRATION CQ-100 CO-96 CO-90 CO-50 CO-40 CO-20 CO-1O 0.041 0.044 0.557 0.976 1.49 FIGURE 6.19 0.930 0.705 1.25 1.37 1.80 not no COPPER sampled flow IN CALIFORNIA GULCH (August, 1985)

SAMPLE SITES AR-10 AR-20 SD-10 OQ-10 YT-10 SP-10 CQ-100 STATION <0.003 <0.003 0.04 0.091 DISSOLVED (mg/D* <0.003 0.045 0.063 0.930 TOTAL (mg/l) * 17 150 no not no NORTH SEDIMENT (mg/kg) 10 0.04 flow sampled flow 1/2 9.1 FLOLOAWD (Ibs/day(cfs) ) 45 43 0.12 1.8 PH 7.0 6.9 7.5 IScaln Milee s 6.8 15% VARIABILITY IN CALIBRATION) CO-95 CG-100 CO-60 CO-50 CO-40 CO-20 CO-10 FIGURE 6.20 0.460.8500 0.630 0.430 0.760 2800 1600 1.50 2.00 3.00 27 not not 2100 9800 19,000 LEAD 6.0 sampled sampled 6.048 47 52 4.0 4.4 3.2 IN CALIFORNIA GULCH 3.6 3.7 3.3 (May 1985)

AR-10 AR-20 80-10 OQ-10 YT-10 8P-10 CO-100 STATION <0.025 1.25 0.062 <0.025 0.460 DISSOLVED (mg/l)* <0.025 2.50 0.076 0.090 NORTH 0.850 TOTAL (mg/l) * 98 16 4200 not 2800 SEDIMENLOAD (Ibs/dayT (ma/kg) ) 9.6 0.17 677 sampled 1/2 27 FLOW (cfs) 250 0.71 0.42 2.0 6.0 PH 7.2 2.9 3.1 6.2 IScaln Milee s 6.0 * 15% VARIABILITY IN CALIBRATION CO-100 CQ-40 CQ-20 CO-1O FIGURE 6.21 <0.020.3850 0.330 0.260 0.470 not 0.410 0.360 0.510 sampled LEAD IN CALIFORNIA GULCH (June, 1985)

LEADVILLE Stray Horse Gulch Yak Tunnel n^ DitchStarr STRINGTOWN

HIGHWAU.S. Y 24 California Gulch California Gulch TAILINGS POND SAMPLE SITES 30-10 YT-10 8P-10 CQ-100 STATION 1.87 <0.25oa-io0 <0.250 <0.250 <0.250 DISSOLVED (mg/l)* 4.50 0.280 <0.250 TOTAL (mg/l) * not not 0.320 0.380 SEDIMENT (mg/kg) sampled sampled 0.01 FLOLOAWD (Ibs/day(cfs) ) 0.005 PH 2.8 IScaln Milee s * 15% VARIABILITY IN CALIBRATION <0.02co-eo5 0.135 LEAD IN CALIFORNIA GULCH (August, 1985)

AR-10 AR-20 8D-10 OO-10 YT-10 8P-10 CO-100 STATION kO.025 <0.025 <0.025 :0.025 DISSOLVED (mg/D* :0.025 <0.025 0.388 NORTH 0.098 TOTAL (mg/l) * 28 1100 no not not SEDIMENT (mg/kg) 0.25 flow sampled sampled 1/2 0.96 FLOLOAWD (Ibs/day(cfs) ) 45 43 0.12 1.8 PH 7.0 6.9 7.5 IScaln Milee s 6.8 * 16% VARIABILITY IN CALIBRATION! CO-100 CQ-40 FIGURE 6.23 61.66.0 71.75.0 4200 not not 3600 2000 sampled sampled 2300 ZINC 6.0 6.0 IN CALIFORNIA GULCH 4.0 3.6 (May 1985)

LEADV LLE Stray Horsa Gulch Yak Tunne rr^+-Starr Ditch STRINGTOWN U.S. HIGHWAY 24 California Gulch California Gulch TAILINGS POND SAMPLE SITES SD-10 YT-10 STATION 259 oa-i50.0 o 81.0 DISSOLVED (mo/I)* 242 47.0 72.0 TOTAL (mg/l) * 26,000 not SEDIMENT (mg/ke) 930 sampled FLOLOAWD (Ibs/day(cfa) ) 0.71 PH 2.9 IScaln Milee s # 16% VARIABILITY IN CALIBRATION CQ-40 CG-20 CO-10 CQ-1045.0 0 72.0 69.0 13.0 FIGURE 6.24 47.0 76.0 71.0 13.0 not not not ZINC 1500 sampled sampled sampled 1200 1100 6.0 2.9 2.9 IN CALIFORNIA GULCH 4.8 3.6 3.6 (June, 1985)

LEADVILLE Stray Horse Gulch Yak Tunnel

STRINGTOWN U.S. HIGHWAY 24

California Gulch California Gulch TAILINGS POND SAMPLE SITES so-10 OG-10 YT-10 SP-10 CQ-10O STATION 29.0 268 107 4.40 45.0 DISSOLVED (mg/l) * 32.0 279 108 4.30 47.0 TOTAL (mg/l) not not SEDIMENT (mo/kg) sampled sampled 110 7.5 1500 FLOLOAWD (Ibs/day(cfs) ) 0.66 0.005 6.0 PH 3.6 2.8 IScaln Milee s 4.8 15% VARIABILITY IN CALIBRATION CO-OS CO-60 CQ-SO CG-40 CO-1029.0O 24.0 55.8 64.6 71.8 FIGURE 6.25 40.0 37.0 61.0 69.0 74.0 not not ZINC sampled sampled IN CALIFORNIA GULCH (August, 1985)

LEADVILLE Stray Horse Gulch Yak Tunqel

STRINGTOWN U.S. HIGHWAY 24 California Gulch California Gulch TAILINGS POND SAMPLE SITES AR-10 AH-20 8D-10 CO-100 STATION 0.112 1.28 0.092 29.0 DISSOLVED (mg/0* 0.148 1.86 0.775 40.0 TOTAL (mg/0 230 2700 not SEDIMENT (mg/kg) 36 430 0.50 sampled FLOLOAWD (Ibs/day(cfs) ) 45 43 0.12 PH 6.9 7.0 7.5 IScaln Milee s * 16% VARIABILITY IN CALIBRATION -•,.5-- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION ponds in the gulch. From below the tailings to the mouth of California Gulch, the gulch loses 2.14 cfs. The June study indicated the California Gulch is a losing stream in the Yak Tunnel reach and remains roughly even in flow through the tailings ponds. The gulch gains 0.91 cfs from below tailings pond 3 to below Oregon Gulch. The gulch loses 0.46 cfs through Stringtown, then gains 1.07 cfs from below Stringtown to just above the Leadville STP. There is little change in flow from the Leadville STP to the mouth of the gulch. The major losing reaches in August on California Gulch were the gulch through tailings ponds 1, 2, and 3 (loss of 0.37 cfs) and the gulch through Stingtown (0.24 cfs). The gulch gained flow (0.25 cfs) below the tailings ponds and near the sewage treatment plant (0.69 cfs). Upper California Gulch (1) This reach is located along California Gulch above Yak Tunnel. Two sampling locations, SP-10 and CG-10, are located along this reach. The spring (SP-10) was only sampled during the June sampling event because it was not flowing during the August sampling. Discharge from the spring contained beryllium, cadmium, copper, lead and zinc. Although the spring is located in an area disturbed by mining, levels of total copper and total and dissolved arsenic, cobalt, and zinc are much lower than those seen downstream in the Yak Tunnel discharge. Upper California Gulch was shown in May to contain cadmium (0.180 mg/1 total), copper (1.70 mg/1 total), lead (3.00 mg/1 total), and zinc (26.0 mg/1 total). In June, the same hazardous metals were detected, but in concentrations generally less than half those seen in May (0.085 mg/1, 0.590 mg/1, 0.510 mg/1, 13.0 mg/1 for total cadmium, copper, lead, and zinc, respectively). The upper gulch contributes a large portion of the loadings for cadmium, copper, lead, and zinc in May. 6-61 - ._, YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION The loading values in June are approximately one-fourth of the values seen in May. There was no flow observed during the August sampling period in the gulch above Yak Tunnel. California Gulch at Yak Tunnel (2). This reach is located along California Gulch at Yak Tunnel. The Yak Tunnel effluent was the only surface water inflow in this reach and, therefore, is the primary contributor of hazardous metals in the reach. The Yak Tunnel drainage in May contained total cadmium, copper, lead, and zinc concentrations of 0.360 mg/1, 0.24 mg/1, 0.09 mg/1, and 72.0 mg/1, respectively. Total concentrations of cadmium and zinc were increased by 50 percent and 85 percent from the previous reach. In May cadmium and zinc loadings both increased by more than 100 percent above levels in the previous reach, from 3.1 to 6.3 pounds per day (Ib/day) cadmium and from 450 to 1,100 Ib/day of zinc) and by more than 500 percent in June (from 1.1 to 5.4 Ib/day cadmium and from 160 to 1,100 Ib/day zinc). Yak Tunnel effluent was above EPA Drinking Water Standards for cadmium, lead, and zinc during May and above standards for cadmium, copper, and zinc in June. Yak Tunnel and California Gulch below the tunnel were not sampled in August due to denial of access to ASARCO property. California Gulch Through Tailings (3). This reach is located along California Gulch from below the tunnel to California Gulch above Starr Ditch (CG-40). The concentrations of cadmium, lead, and zinc increase between California Gulch below Yak Tunnel (CG-20) and Cali- fornia Gulch above Starr Ditch (CG-40), indicating a source of metals in this stretch. Loadings of cadmium, copper, and zinc, increased by 90.5 percent, 35.7 percent and 109.1 percent above those in the previous reach in May. The concentrations of total cadmium, copper, lead, and zinc at CG-40 exceeded EPA Drinking Water Standards by 3,900 percent, 120 percent, 3,000 percent, and 1,420 percent, respectively. Since no drainages to the gulch were observed in this segment during the May and June sampling events, the three tailings ponds are the

6-62 ...-.- YAK TDNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION likely source of hazardous metals in this reach. These ponds have been shown to contain arsenic, beryllium, copper, lead, mercury, nickel, selenium, silver, thallium, and zinc (see Chapter 4). California Gulch Near Starr Ditch and Oregon Gulch (4). Starr Ditch enters California Gulch just below the third tailings pond. Oregon Gulch, which drains the fourth tailings pond in the area, flows into California Gulch approximately 20 yards downstream of the confluence of Starr Ditch and California Gulch. The majority of metals loading to California Gulch from Starr Ditch occurred during May and June samplings. Flow in Starr Ditch contained cadmium, copper, lead, and zinc during the May and June samplings. In August, lower concentrations of total lead, total and dissolved copper, molybdenum, and zinc were observed in Starr Ditch compared to sampling done in May and June. The flow from Starr Ditch was highest during May, at 0.71 cfs, and decreased to 0.12 cfs by August. Mass loading values for Starr Ditch in May were 6.9 Ib/day cadmium, 15 Ib/day copper, 9.6 Ib/day lead, and 930 Ib/day zinc. During the May sampling, the mass loadings of cadmium, copper, lead, and zinc were higher from starr Ditch than from the Yak Tunnel. In June, the loadings decreased so that mass loading contributions by Starr Ditch to California Gulch was much lower than Yak Tunnel contributions for cadmium, copper, and zinc. The lead mass loadings from Starr Ditch remained relatively high in June at 6.2 Ib/day. Drainage from Stray Horse Gulch was observed flowing into Starr Ditch during the May and June sampling, but no flow was observed in Stray Horse Gulch in August. The most likely source of metals are the numerous mine dumps along Stray Horse Gulch. These dumps have been shown to contain arsenic, cadmium, copper, lead, nickel, and zinc (Chapter 4). Leachate tests indicate that most of the piles could release cadmium, copper, lead, nickel, and zinc to surface waters.

6-63 - ... YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Oregon Gulch had fairly small flows during May and June, with 0.42 cfs and 0.005 cfs, respectively. Metal concentrations of copper and zinc were very high. Drainage from Oregon Gulch during May 1985 contributed 2.7 Ib/day of copper, 0.17 Ib/day of lead, and 110 Ib/day of zinc to California Gulch. California Gulch Through Stringtown to Arkansas River (5). In this reach, California Gulch follows Highway 24 through Stringtown, past the Leadville STP discharge point, to the confluence with the Arkansas River. Metal concentrations in this reach remained fairly constant in August from below the tailings ponds to above the sewage treatment plant discharge. The sewage discharge pH ranges from 6.5 to 9.0 (Colorado Department of Health, 1985). This discharge helps to neutralize the pH of the flow in California Gulch and to lower the concentrations of dissolved metals in California Gulch downstream of the discharge point. Mass loading values indicate little change in total metals loading in this reach. Just above the confluence with the Arkansas River, California Gulch contained detectable levels of cadmium, copper, lead, and zinc. The concentrations of these four metals (total and dissolved) were highest in May and decreased in June and August. This trend is at least partially due to the increased metals loading from to tailings ponds 1, 2, and 3 and Starr Ditch to California Gulch during late spring and early summer. Statistical analysis of the ES California Gulch data is presented in Appendix B. The analysis included four California Gulch stations; above Yak Tunnel, below Yak Tunnel, below the tailings pond 3, and above the confluence with the Arkansas River. The results for total cadmium, copper, lead, and zinc indicate that the variation between stations for a given sampling period was statistically significant and that the variation at a given sampling station between sampling periods was also statistically significant.

6-64 - s_. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 . REMEDIAL INVESTIGATION

Of the four stations examined statistically upper California Gulch contained the highest concentrations of the above-listed metals during the May sampling. In June, California Gulch below Yak Tunnel contained the highest concentrations of cadmium, copper, and zinc. The concentrations of all four metals at the mouth of the gulch are the lowest in August. Zinc, cadmium, and lead concentrations at this station are highest in May and copper is highest in June. Total lead concentrations seem to be unrelated to the Yak Tunnel flow. The major lead contributions to California Gulch may be sediment loading from waste piles in the upper gulch and from the tailings ponds in California Gulch. An analysis of mass loading along California Gulch indicates that Yak Tunnel is a source of metals for all sampling periods, but upper California Gulch, tailings ponds 1, 2, and 3, and Starr Ditch are major sources of cadmium, copper, and zinc in May. The major source of lead in May appears to be the upper gulch, which was found to contribute 52 Ib/day during the ES May sampling. Yak Tunnel was found to contribute the majority of the cadmium, copper, and zinc of the sources sampled in June. The upper gulch and Starr Ditch mass loading values for lead, 6.4 Ib/day and 6.2 Ib/day, respectively, were greater than the loadings from the upper gulch, Yak Tunnel, or the tailings ponds. Flow in California Gulch above tailings pond 3 and the Yak Tunnel effluent were not sampled in August due to denial of access to ASARCO property, so no conclusions can be drawn as to relative loadings from Yak Tunnel and tailings ponds 1, 2, and 3.

6-65 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Arkansas River Reaches The variation of specific metal concentrations and other water quality parameters along the Arkansas River during the August, 1985 sampling are depicted on Figures 6.26 through 6.28. The changes in metal concentrations and loading are discussed by reach. Upper Arkansas River above California Gulch (1). This reach consists of the Arkansas River from its headwaters to just above its confluence with California Gulch. From the headwaters to the confluence with the Leadville Drainage Tunnel, the East Fork of the Arkansas River flows through areas that are relatively undisturbed by mining activities. Previous studies by McLaughlin Engineers (1981) and Roline and Boehmke (1981) have shown that the concentrations of cadmium, copper, lead, and zinc in the East Fork above the Leadville Tunnel area are very low or not detectable during most sampling events (see Table 6.11). The Leadville Drainage Tunnel contributes cadmium, copper, lead, and zinc to the East Fork of the Arkansas River, but the concentrations of these metals are reduced in the Arkansas River just upstream of California Gulch. The study by Roline and Boehmke (1981) found that cadmium, copper and zinc concentrations in the Arkansas River just above California Gulch did not exceed EPA Drinking Water Standards. Although lead sometimes exceeded the standard, the mean lead value for the 19 samples is lower than the standard. The Arkansas River was sampled upstream of California Gulch by ES in May and August. Zinc was detected at very low levels compared to the metal concentrations detected along California Gulch. Cadmium, copper, and lead were not detected. California Gulch to Lake Fork (2). This reach is located along the Arkansas River from below the confluence of California Gulch to the confluence with Lake Fork. Engineering-Science sampled two sites along the Arkansas River and one site along Lake Fork. The Arkansas River below California Gulch showed increased concentrations of total and 6-66 AR-80 AR-90 3.004** «0.003 <0.000.003*3* D.003*0.045* CO0.06. 0034 D.003*0.017 * 0.0040.017* 0.004*0.014 * 0.010.004*5 * 3.011** 5.007** 17 150

FIGURE 6.27 COPPER IN THE ARKANSAS RIVER SYSTEM

YAK TUNNEL ( AUGUST, 1985)

SAMPLE SITES AR-20 STATION 0.040.0053 PISSOLVED (mg/D* 150 TOTAL Cmg/l) * 10 SEDIMENLOAD (Ibs/dayT (mg/kg) ) 43 FLOW (cfs) LEADVILLE 6.9 PH California Gulch * ± 15% VARIABILITY IN CALIBRATION

above detection limit but below confidence limit Turquoise Lake

CG-100 LF-10 IG-10 EG-10 LC-10 0.041 <0.002 <0.003 <0.003 <0.003 0.930 0.004** 0.004** 3.005** 0.006* AR-10 AR-2O AR-40 AR-45 AR-50 AR-60 AR-65 At 3 AR-9O <0.004 0.006* <0,OQAR-304

SAMPLE SITES AR-20 STATION 0.006 DISSOLVED (mg/1)* TOTAL (mg/1) * 0.005 SEDIMENT (mg/kg) 16 LOAD (Ibs/day) 41.52 FLOW (cfs) 7.0 PH

* ±15% VARIABILITY IN CALIBRATION

** above detection limit but below confidence limit

CG-100 LF-10 IG-10 EG-10 LC-10 0.117 <0.004 <0.004 <0.004 0,156 <0.00

SAMPLE SITES AR-20 STATION 1.2R pISSOLVED (mg/D* 1.86 TOTAL (mg/l) * 2700 SEDIMENT (mg/kg) 430 LOAD (Ibs/day) 43 FLOW (cfs) LEADVILLE 6.9 PH California Gulch * ±15% VARIABILITY IN CALIBRATION

Turquoise Lake

CG-100 IG-10 EG-10 LCi-10 29.1 0.151 CO. 004 <0.p04 40.0 0.203 0.014 0.008 i— 2 Miles I6.- 4 I '

TABLE 6.11 TOTAL METALS IN THE UPPER ARKANSAS RIVER (MG/L)

Sampling Station Statistics Cd Cu Pb Zn Fe Mo Arkansas River 19 Range ND-0.0070 ND-0.113 ND-0.0071 ND-0.03 ND-1.94 HD-0.10 above Leadvllle Mean 0.00066 • 0.0088 0.0021 0.006 0.385 0.247 Tunnel Standard Deviation 0.0017 0.0255 0.0024 0.008 0.508 0.0295 Arkansas River Range ND-0.0017 ND-0.1510 ND-0.6066 0.13-0.90 ND-1.19 ND-0.23 above California Hean 0.0013 0.0107 0.0466 0.2669 0.30 0.0831 Gulch Standard Deviation 0.0012 0.0342 0.1413 0.1695 0.31 0.0605 Source: Rollne and Boehrake (1981) - .... YAK TUNNEL/CALIFORNIA GULCH 2/28/86 . REMEDIAL INVESTIGATION dissolved cadmium, total copper, and total and dissolved zinc during the August sampling compared to the reach immediately upstream. The total metals concentrations exceeded the maximum allowable concentrations for one-hour acute toxicity to aquatic life. The total mass loadings for cadmium, copper, and zinc increased from undetectable to amounts to 1.2 Ib/day, from undetectable amounts to 10 Ib/day and from 36 to 430 Ib/day, respectively, from above to below California Gulch. Concentrations of cadmium, copper, and zinc remained consistant downstream to the sampling point just above the confluence with Lake Fork. Lake Fork to above Lake Creek (3). This reach is located along the Arkansas River from below the confluence with Lake Fork to above the confluence with Lake Creek. The ratio of flow in Lake Fork to flow in the Arkansas River at the confluence is approximately 1:1. Lake Fork had a diluting effect on metals concentrations in the Arkansas River, generally reducing metals concentrations in the Arkansas River by 50 percent. Total copper, and total and dissolved zinc remained above detection limits in the Arkansas River below the confluence with Lake Fork. All total copper and zinc concentrations were above the one-hour aquatic life acute toxicity guidelines. Concentrations remained fairly constant downstream to the Highway 24 bridge over the Arkansas River, but decreased between this point and the Arkansas River above Lake Creek. Iowa Gulch and Empire Gulch, tributaries to the Arkansas River, contributed minor mass loads of copper and zinc to the Arkansas River. Cadmium was not detected in either of these tributaries. Above Lake Creek to Below Lake Creek (4). This reach is located along the Arkansas River from above Lake Creek to the town of Granite. Two sites were sampled in August along this reach, the Arkansas River above and below Lake Creek. Although Lake Creek has a diluting effect, total copper and zinc concentrations remained above detection limits below the confluence with Lake Creek. The concentrations of copper and 6-71 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION zinc are below the 1-hour acute toxicity guidelines for aquatic life, but remain above the 96-hour chronic toxicity guidelines. Concentra- tions of copper and zinc in the Arkansas River below Lake Creek remain above the concentrations found in the Arkansas River above California Gulch, copper and zinc remain above one hour acute toxicity guidelines for aquatic life. The concentrations of cadmium, copper, and zinc for all stations of the Arkansas River are shown in Figures 6.29 to 6.31. A statistically significant increase in concentrations of cadmium, copper, and zinc is seen in August 1985 from the Arkansas River above California Gulch to the Arkansas River below the gulch. A similiar significant increase in loading values is also seen for cadmium, copper, and zinc. Copper loading increases from below California Gulch to above Lake Fork, indicating a nonpoint source of copper in the reach. Lake Fork dilutes the metals in the Arkansas River and contributes relatively low amounts of copper, cadmium, and zinc. Cadmium was not detected in the Arkansas River in any of the samples taken below the confluence with Lake Fork. Copper and zinc remain detectable, and are in concentrations above the 1-hour acutely toxic aquatic life guidelines (see Table 6.5) as far downstream as the Arkansas River above Lake Creek. Copper and zinc loadings decrease from the confluence with Lake Fork to the confluence with Lake Creek except for an increase in copper loading between Iowa Gulch and Empire Gulch. The source of this loading is not known. Surges In addition to the continual discharge from Yak Tunnel, the tunnel is subject to occasional surges. One recent surge occurred on October 22, 1985 during the course of this study. The surge was probably due to a breach of a blocked area in the tunnel. Blockages occur due to collapses when the tunnel and mines are not maintained. Analysis of water taken during the surge indicated that iron was the most prevalent metal. Copper and zinc were also detected. Water quality results from

6-72 Cadmium Concentration (rng/l)

D o a_ 3 O p O p p p p p c* b b b o o O b b b b O b 3 UoJ o o o> -*o» o 0o1 eon Uol oen O o > CO a» CD N> O) DO —J!. U>(A O_ o < trox ND O >O to Drl- ocr. U3J > 10 /*~C\ C •D \Si o U>rt- I c- •^ wye 5 Ul CO w o Um) tOn o Ic' Iu (D I D en o 3 O Ort- en m -

50 I CD O Copper Concentration (mg/l) Zinc Concentration (mg/l) n NJ pop pop pop o3* '—* k> w 4^ In en xj co to Q. to (6

M O 3o > to C. 1c0 T>Ut (£/ I cCnD 7>7 o TO „Um) -jp^51" •a- D Q. UIl •&» o- o o o 2?- >W - r-^ i-l- •S- S Z• I3 Q_ D o> 22 7rn5 CID

COD - ,.-. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION the samples taken during the surge are presented in Appendix D. At the EPA flume at the mouth of Yak Tunnel a discharge of 1.33 cfs was measured at 3:50 p.m. on October 22, 1985 with a high water mark of 7.42 cfs indicated by iron staining on the flume. This does not account for bypass flow, and the actual peak flow was probably higher. At California Gulch above the confluence with the Arkansas River, a discharge of 1.7 cfs was recorded, with a high flow of 7.94 cfs. The following day, readings were taken from the flume on California Gulch below the Yak Tunnel. The flow measured 1.31 cfs with a high flow of 10.12 cfs indicated. Water intakes along the Arkansas River were closed for several days after the surge to prevent metals contamination and sediment clogging municipal water treatment systems. Arkansas River Sediment Sediment was collected in conjunction with aquatics sampling in the Arkansas River during the months of May and September. The metals in sediments have two main sources. Increases of 560 percent in zinc, 200 percent in copper, 1,100 percent in lead, and 380 percent in cadmium concentrations in the sediment were observed at the sampling station below the Leadville Drainage Tunnel (AR-6). Below the inflow of Tennessee Creek, metal concentrations in sediments declined to levels which were even lower than those above the Leadville Drainage Tunnel. Immediately below California Gulch (AR20) increases in sediment concentrations of zinc by 1,200 percent, copper by 890 percent, lead by 3,900 percent, and cadmium by 1,000 percent were observed. Concentrations of zinc, lead, and cadmium in the sediments remained high downstream to County Road 55 at Kobe (AR70). Concentrations of copper were very high at the Highway 24 overpass and then declined between the overpass and Kobe to a level that was 500 percent higher than that observed above California Gulch. Changes in metal concentrations for spring and fall sampling in the Arkansas River are depicted graphically in Figures 6.37 through 6.39.

6-76 Cadmium Concentration (mg/kg)

oO 3a. 3E*

to ff cro. 4- u /*~v o c"5

I !a° . O €o 2"~*." "5 o u anC>T r^-;- 3S Copper Concentration (mg/kg} Lead Concentration (mg/kg) (Thousands) I I ZINC IN ARKANSAFIGURS ERIVE 6.35R SEDIMENTS (Engineering-Science Data — 1985)

en r I? Qc) J:0 o0 co N

AR-3 AR-6 AR-10 AR-20 AR-45 AR-65 AR-70 Stations (upstream to downstream) D Zinc May -\- Zinc — October YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

ENVIRONMENTAL AND PUBLIC HEALTH EFFECTS Sampling of the Arkansas River in August 1985 indicated that the levels of cadmium remain elevated in the Arkansas River from below the confluence with California Gulch to above the confluence with Lake Fork (see Figures 6.37 to 6.39). Copper and zinc concentrations downstream below Lke Creek are higher than those found in the Arkansas River above California Gulch. Elevated metals concentrations impact stream users in this area. The metals in irrigation waters cause high levels of metals in the soils in irrigated areas of the upper Arkansas River Valley. High metals concentrations in the soils impact vegetation growth and may spread the metals through the food chain to grazing livestock. A lack of vegetative growth increases soil erosion and loads the streams in the area with sediment during snowmelt and precipitation events. The effects of metals on vegetation are further discussed in Chapter 9. Concentrations of copper, lead, cadmium, and zinc at the concentration seen in California Gulch and the Arkansas River impact aquatic life. All samples in California Gulch and in the Araknsas River to above Lake Creek had metals concentrations that are considered acutely toxic to aquatic life. Lower concentraionts of these metals can have a chronic toxic effect on aquatic life. Chapter 7 details the toxic effects of various levels of these metals and presents the data from aquatics investigations in California Gulch and the Arkansas River. California Gulch and Stray Horse Gulch are used by Leadville residents and people vacationing in the area for recreation. Stray Horse Gulch runs through the eastern section of Leadville in front of residences prior to emptying into Starr Ditch. Dissolved cadmium concentrations in Starr Ditch in May were above EP toxicity levels. The EP toxicity test is used to determine if industrial waste are considered hazardous under the Resource Conservation and Recovery Act.

6-81 ..... YAK TUNNEL/CALIFORNIA GOLCH 2/28/86 REMEDIAL INVESTIGATION Children have been observed playing in the drainage. Panning for gold is also a popular recreational activity of summer vacationers to the area.

6-82 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION

CHAPTER 7 AQUATIC BIOTA INVESTIGATION

Recent studies of the upper Arkansas River near Leadvilie, Colo- rado found the aquatic system severely polluted by hazardous substances (LaBounty et al., 1975; Roline and Boehmke, 1981). Hazardous substances have been found to contaminate the surface water, the sediments, and the biota of the Arkansas River from Leadville to Salida, a distance of nearly 75 river miles. Heavy metal contamination has dras- tically reduced the potential of the Arkansas River resource from Leadville to Salida by creating poor conditions for aquatic life. Contamination of the Arkansas River has led to a change in the structure of the macroinvertebrate community so that an inferior food base is provided for the trout populations. The macroinvertebrates are also contaminated by bioaccumulation of heavy metals. The contaminated surface water and food base provide two pathways of toxicity by which heavy metals can act on the fish populations. Significantly reduced trout standing crops are found downstream from California Gulch. The low standing crops are attributable to heavy metals concentrations which reach lethal levels and to long-term exposure to heavy metals which reduces the reproductive capacity of trout. The loss of reproductive capacity is effected by polluted stream segments that repel migrating trout and prevent them from reaching suitable, uncontaminated spawning grounds; by reducing the viability of eggs which are laid in contaminated areas; by reducing the number of large trout available for reproduction; by retarding the growth of juvenile trout; and by exposure of the young, sensitive life-stages to acutely toxic levels of heavy metals.

7-1 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION The discussion of the aquatic biota investigation begins with a general description of the study area. It proceeds to describe methods used to sample ma cro invertebrates and fish and the results from the sampling efforts. The toxicity to trout by contaminants found in sufficient concentrations to cause concern is then discussed. This discussion includes information which describes concentrations found to have impacts on trout and the extent to which these concentrations are found in the Arkansas River. This information is related to the observations made by the field studies described in this report and to observations made by other studies on the Arkansas River. The implications of this information on the aquatic biota resource of the Arkansas River are then reviewed. RESOURCES AND USE Macrohabitat The Arkansas River near Leadville is a cold-water, high-gradient mountain stream close to its origins at the crest of the Continental Divide. The river flows generally from north to south through a broad valley, alternately meandering through low-gradient wetlands and rushing through high-gradient rocky stretches. The elevation of the study area ranges from 9,150 feet to 10,000 feet above mean sea level and the stream gradient within the study area ranges from 0.8 to 1.5 percent. A general map of the aquatic resources study area is provided in Figure 7.1. The upper Arkansas River is slightly alkaline; the pH fluctuates between 7 and 8.5, but is generally 7.6 to 8.0. Dissolved oxygen is greater than 90 percent saturation and may exceed 100 percent saturation. Total dissolved solids and hardness are generally between 100 and 200 mg/1 upstream from Tennessee Creek and below or near 100 mg/1

7-2 FIGURE 7.1 AQUATIC LIFE SAMPLING STATIONS

V-UEADVILLE DRAINAGE TUNNEL

\_ Stray Horsa Salch

California Salch OS.HWY Z4

t» Mt. Wa**iv* Udkt* YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION downstream frora-Lake Fork to Salida. High concentrations of nitrogen and phosphorus enter the Arkansas River from California Gulch because of contributions from the Leadville sewage treatment plant (Roline and Boehmke, 1981). The Leadville Drainage Tunnel, California Gulch, and non-point sources between Lake Fork and Lake Creek were found to be the major contributors of the metal loadings. California Gulch was identified as the most important source. Tennessee Creek provides diluting flows to the Arkansas River downstream from the Leadville Drainage Tunnel, and Lake Fork and Lake Creek dilute metals concentrations in the Arkansas River downstream from California Gulch. Although tributaries dilute the metals concentrations, their soft water reduces the hardness of the Arkansas River. Hardness generally provides protection to aquatic life from heavy metals contamination. Aquatic Biota The biota are typical of a cold-water mountain river. The aquatic insects are clingers and sprawlers adapted to erosional habitats. Mayflies (Ephemeroptera), especially the genus Baetis, dominate the benthic community. Stoneflies (Plecoptera), particularly the family Chloroperlidae, and caddisflies (Trichoptera) are also common. Below Lake Fork, the caddisfly Brachycentrus americanus is relatively abundant, possibly because of warmer water and an increase in organic material. This species also appears to be tolerant of metals pollution (Roline and Boehmke, 1981). The fish community is dominated by brown trout (Salmo trutta). The Arkansas River above California Gulch is considered a fair fishery with self-sustaining populations of brown and brook trout (Salvelinus fontinalis) (Finnell, 1977). The fish population is severely reduced in the river between California Gulch and Lake Fork because of high concentrations of metals (LaBounty et al., 1975; Finnell, 1977; Roline and Boehmke, 1981). The loss of a potentially high-quality fishery

7-4 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION from Leadville -to Salida, Colorado due to heavy metal pollution was suggested by Nehring and Anderson (1984) after overfishing and a poor food base were considered and eliminated as possible causes. NATURE AND EXTENT OF CONTAMINATION Sampling Stations The Arkansas River was divided into segments based on areas with little human impact and on areas with possible influences from tributaries, towns, and mining activities. Based on accessibility, these segments were reduced into reaches 440 to 720 feet long which were sampled for fish and evaluated for fish habitat. The reaches were labeled with numbers increasing from upstream to downstream (Figure 7.1). Within each reach, accessible areas of riffles were chosen as stations for aquatic macroinvertebrate and sediment sampling. The Arkansas River sampling stations were located upstream of the Leadville Drainage Tunnel where State Highway 91 crosses the Arkansas River, downstream of the Drainage Tunnel where U.S. Highway 24 crosses the Arkansas River, downstream of Tennessee Creek where County Road 300 crosses (northern crossing) the Arkansas River about 500 feet downstream from California Gulch, downstream from Lake Fork near the Smith Ranch Road, downstream from Iowa Gulch near U.S. Highway 24 overpass, and downstream from Spring Creek where County Road 55 crosses the Arkansas River near Kobe. Lake Fork and Halfmoon Creek were chosen as reference streams for aquatic invertebrate and fish sampling, respectively. Both were sampled just upstream from the County Road 11 crossing, about one-half mile from the confluence of Lake Fork with the Arkansas River. Station AR10 was located about 2 miles upstream from surface water sampling station AR10 because the lower area was difficult to access and sample for fish. California Gulch was not sampled because preliminary studies revealed that it supported no fish life and very little invertebrate life.

7-5 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION

Sampling Methods Aquatic Macroinvertebrates Benthic macroinvertebrates were captured for metals analyses with a kick-sampler until at least 100 milligrams of bioraass were collected. Two samples per study site were collected in May and October 1985. The organisms were immediately picked from the debris, washed with filtered water, frozen, and delivered to the laboratory for whole-body analysis of metals. Samples of benthic organisms for quantitative estimates of density were collected from riffles in September and October with a modified Hess sampler which covered a 0.114 square meter area (Merritt and Cummins, 1984). Three samples were taken from each site, preserved in 70 percent ethyl alcohol, and delivered to Henry Zimmerman, an expert taxonomist of Colorado aquatic invertebrates, for enumeration and identification. May samples were enumerated and identified by Eco- systems Research Institute, Inc., Logan, Utah. Fish Fish were sampled with a gasoline-powered backpack electroshocker. Two passes were made at each reach unless fewer than five fish were collected on the first pass. Captured fish were removed from the stream and kept alive until sampling was completed. All captured fish were weighed, measured, and released. Population estimates were calculated by the Moran-Zippin method (Bagenal, 1978). Trout less than 80 millimeters in length were enumerated but were not used in the population calculations.

7-6 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Sampling Results'^ Aquatic Macroinvertebrates Sampling of the macroinvertebrate community revealed the organisms were contaminated with heavy metals through the process of bioaccumulation. A reduction in the abundance of organisms was observed below the Leadville Drainage Tunnel and California Gulch, and a change in the community structure occurred below California Gulch. Metal concentration. The lowest concentrations of metals in macroinvertebrates were found in organisms taken from Lake Fork (LF1) and the Arkansas River upstream from Leadville (AR3) (Table 7.1). Values from those two sampling sites are considered to represent background concentrations. Elevated levels of metals in macroinvertebrates relative to the background concentrations occurred downstream from the Leadville Drainage Tunnel (AR6). However, the effects of the tunnel were short-lived as concentrations of metals in the benthic organisms declined upstream from California Gulch (AR10). A similar decline was observed in the metals concentrations in the sediments (Table 7.2). Tennessee Creek flows into the Arkansas River between these two stations and dilutes the metals concentrations in this reach of the Arkansas River. Bioaccumulation of metals by macroinvertebrates increased downstream from the California Gulch inflow (AR20) (Table 7.1). The downstream extent of bioaccumulation varied by metal and by sampling period. Bioaccumulation of zinc was generally higher in the spring than the fall. Elevated levels of zinc were found in the macroinvertebrates throughout the study area, but bioaccumulation was particularly notable below California Gulch and extended at least to the lowermost station (AR70) (Table 7.1). Roline and Boehmke (1981) found that zinc concentrations in the water remained relatively constant from the Smith Ranch to Lake Creek. During this study, zinc concentrations in the sediments were found to remain more than 500

7-7 TABLE 7.1 CONCENTRATIONS OF METALS (MG/KG) FROM INVERTEBRATES TAKEN FROM THE ARKANSAS RIVER AND TRIBUTARIES DURING MAY AND OCTOBER, 1985 Zinc Copper Cadmium Lead _tmpling Station May Oct May Oct May Oct May Oct *rkansas River above — 2/ 411 — 20 — ••• 3 — 12 Leadville (AR3) Arkansas River below highway 24 — 1360 — 24 8 — 16 above Leadville (AR6) Arkansas River above 1600 1012 48 17 16 5 600 10 California Gulch (AR10) Arkansas River below 2400 2955 270 164 17 18 120 104 California Gulch (AR20) Arkansas River at Smith Ranch 10400 996 175 58 56 6 440 26 Road (AR45) »*-kansas River below Highway 24 9000 1053 150 46 49 7 560 31 Bridge (AR65) _:kansas River at Co. Road — 1260 — 63 __ g — 36 55 (AR70) ike Fork (LF1) _ 286 — 26 __ 2 9 17 Mean of two samples, except (D-K) in which two samples from eight stations were pooled. 27 Indicates no samples collected. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION percent higher from California Gulch to the lowermost station than zinc in baseline sediments (AR70) (Table 7.2). Water quality and sediment analyses show contamination of the aquatic environment by zinc occurs at least to the lowermost station. Thus, at least two pathways for bioaccumulation of zinc are available to the macroinvertebrates. Macroinvertebrates contained more copper in the spring than the fall (Table 7.1). The influence of the Leadville Drainage Tunnel effluent on bioaccumulation of copper appears to be minimal, but analysis of organisms downstream from the confluence with California Gulch (AR20) reveals a marked increase (greater than five-fold) in bioaccumulation of copper. Downstream from Lake Fork (AR45), organisms did not accumulate as much copper as upstream from the confluence with that stream. However, the whole-body copper concentrations in macroinvertebrates remained elevated at least to the sampling location downstream from Spring Creek (AR70). At Station AR70 copper concentrations remained more than three times as high as those observed from organisms collected upstream from California Gulch. These trends were also reported by LaBounty et al. (1975). Cadmium uptake by the macroinvertebrates was also observed (Table 7.1). As with the other metals, the downstream extent of bioaccumulation was generally greater in the spring. During low flow, substantial cadmium accumulation was observed only immediately below California Gulch (AR20). Concentrations of lead in macroinvertebrates collected in the fall increased by more than 900 percent below California Gulch (AR20), and then declined by 70 percent within 2 miles (AR45) (Table 7.1). Cali- fornia Gulch has previously been identified as the greatest point- source of lead in the study area (Roline and Boehmke, 1981). Macroin- vertebrates showed a relatively high degree of lead bioaccumulation in the spring.

7-10 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Density and-'-Community Composition. A mean decline of 60 percent in the number of individual macroinvertebrates was observed downstream from the Leadville Drainage Tunnel (AR6) and downstream from California Gulch (AR20) compared to macroinvertebrates densities at sampling stations upstream from these sampling points (AR3 and AR10, respectively) (Table 7.3). In general, total numbers were greater from the Smith Ranch downstream than those at stations upstream from California Gulch. The community structure downstream from California Gulch was also different from that upstream from California Gulch. Although fairly common upstream from Califoria Gulch, the mayfly family, Heptageniidae, and the beetle family, Elmidae, were virtually absent from samples collected downstream from the gulch. Pteronarcyidae (a stonefly family), although never common, was consistently observed at the upper stations, but was found only at one station during one sampling period downstream from California Gulch. Heavy metal and organic loadings from California Gulch effected a shift in the macroinvertebrate community from one dominated by a stonefly-mayfly complex to one dominated by caddisflies, especially case-building caddisflies, and flies. This community composition provides a food-base for trout which is inferior to a stonefly-mayfly complex. Chironomids and caddisflies (Trichopterans), especially case-builders like Brachycentridae, appear to be more tolerant of heavy metals pollution than mayflies and stoneflies (Winner et al., 1980). Loading from the Leadville sewage effluent, which is discharged into California Gulch, and nutrients from Turquoise Lake that enter the Arkansas River via Lake Fork, contribute to a substantial' increase in organic material in the river. The nutrients promote greater primary production which was readily apparent as algae on the substrate. The organic loading and resulting primary production provides a food source for insect herbivores and detritivores and for microorganisms which are

7-11 TABLE 7.2 CONCENTRATIONS OF METALS (MG/KG) FROM SEDIMENT TAKEN FROM THE ARKANSAS RIVER AND.TRIBUTARIES DURING OCTOBER, 1985 Zinc Copper Lead Cadmium Arkansas River above 435 22 32 1.8 Leadville (AR3) Arkansas River below US Highway 24 1225 46 348 6.7 above Leadville (AR6) Arkansas River above 231 16 28 1.5 California Gulch (AR10) Arkansas River below 2695 147 1082 15 California Gulch (AR20) Arkansas River above Smith Ranch 2760 162 1066 19 Road (AR45) Arkansas River below Highway 24 2800 748 833 17 below Leadville (AR65) Arkansas River at County Road 3240 99 824 19 55 (AR70) Lake Fork (LF1) 344 25 70 4.5 Mean of two samples. TABLE 7.3 NUMBER OF AQUATIC MACROINVERTEBRATES PER SQUARE METER1/ COLLECTED FROM THE ARKANSAS RIVER AND ASSOCIATED TRIBUTARIES IN 1985 (ES DATA) Highway 24 Above Above Above Below Smith Ranch Highway 24 Co. Rd. Leadvllle Leadvllle California Gulch California Gulch Road Below Leadvllle 55 Lake Fork (AR 3) (AR 6) (AR 10) (AR 20) (AR 45) (AR 65) (AR 70) __t LF) Sept Oct Sept Oct Hay Sep Oct Hay Sep Oct May Sep Oct Hay Sep Pet Sep Oct Sep Oct INSECTA Ephemeroptera Baetldae 193 9 88 26 193 53 88 — 26 202 70 105 1061 377 158 325 175 210 96 237 Ephemerellidae 18 53 — 35 61 105 342 — 70 18 35 — 123 210 -- — 9 — 79 Hep tageni Idae 579 754 88 18 237 9 44 -— -- -— 9 . — j — __ — — — — • — — — Plecoptera Capnildae 9 — — — — — — — Chloroperlldae 88 605 96 149 26 140 368 -- 96 114 — — 421 9 26 228 105 35 298 518 Nemourldae 9 9 __ __ 132 — — — 9 —— *•» 149 26 -- 35 -- — __ __ -- — • Perlldae —— l1 o ft Perlodldae .... —-. 18 9 53 — . _ . 9—9 18 — 228 26 — — — 18 — __ Pteronarcyldae 9 — 9 9 18 9 9 __ __ 44 -— ~ — • — — — — . -- — — Trichoptera Br achycen tr Idae — — 53 — — 18 35 53 500 386 439 263 105 193 482 579 96 184 Glos aosona tldae — 9 44 — 18 53 140 M 4A 4t 70 Hydropaychldae __ — 44 S3 — 18 __ — . __ __ 18 18 368 132 9 35 18 9 __ Hydroptllldae — 9 — — — — — — Llmneplillldae — — 18 — — — — — — — — — — — — Rhyacophllldae 9 18 26 18 61 18 70 — 44 61 26 26 79 26 — 9 — 26 26 Coleop tera Elraldae 44 263 9 228 79 53 9 99-- 9 — 9 — 9 — 35 9 Dip tera Blephar leer Idae — — — 26 123 — — — — — 26 — — — — Ceratopogonldae — — 9 9 — — — — — — — — — — — Chlrononldae — 158 53 368 9 26 9 35 53 974 465 851 1447 395 1684 1368 167 9 53 Psychodldae — — 44 — 26 — — — — — — — — — — Slmulltdae — . __ 9 -- -- 18 — __ — — . « __ __ — — — . -- — _- 193 — Tlpulldae — — 9 — — 9 — __ 18 — 61 *~ — — — 9 26 Lepldoptera Pyralldae «_ «_ ULIUOCim&ni Tf^A^II 4 iG"P AA 307 79 TURBELLARIA Trlcadlda «« __ _ l1 o*l ARACUNIDA Hydracarlna — — 9 __ — — — — 9 — — — — — ——— Total Number a of Organisms/m 2 949 1720 545 598 1396 476 1105 71 315 554 1844 1070 3588 2639 746 2623 2236 1071 1139 1325 I/ Mean of three samples. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION consumed by various insect feeding groups. The appearance of Glossoso- matidae, which scrapes algae, and Chironomidae, represented predominantly by a herbivore (Cricotopus sp.), are obvious indicators of the increase in primary productivity. Brachycentridae (Bra chycen tru s americanus) and Hydropsychidae (Arctopsyche grandis) are collector- gatherers and collector-filterers, respectively, which appear when increased productivity increases the particulate material in the water which can be filtered or on the substrate which can be gathered. Fish Field observations indicated that habitat ranging from good to poor occurred at fish sampling stations both within and outside contaminated areas of the Arkansas River. Fish habitat appeared to have little correlation with fish standing crop. Results of the fish sampling efforts showed significant differences in standing crop between stations above and below California Gulch. The data also suggested that migrating trout were prevented from reaching suitable spawning areas by chemical barrier caused by severe heavy metal pollution. Habitat. Because habitat influences the standing crop of fish that any particular stream section can support, certain features relevent to trout habitat were visually evaluated. They are described for each station in Table 7.4. The quality of trout habitat varied noticeably between sampling stations. The station immediately upstream from California Gulch (AR10) offered little habitat other than the overhanging vegetation along the banks. It was a straight channel of high velocity water over large cobbles. The Smith Ranch station (AR45) offered the best habitat and consisted of the deep pools associated with undercut banks in a low-gradient reach. The station immediately downstream from California Gulch (AR20) contained some poor habitat because of eroding banks, but it also offered large, deep pools, vegetated undercut banks, and sufficient depth. Similarly, stations

7-13 TABLE 7.4 HABITAT DESCRIPTION OF FISH SAMPLING STATIONS Station Number Location Habitat Description AR3 Upstream from highway 91 Low gradient; sand and gravel; where it crosses the East vegetated banks; 10 percent Fork of the Arkansas River undercut banks; 0.1-1.0 feet (above Leadville). deep. AR6 Downstream from highway 24 High gradient; alternating where it crosses the East pool-riffle areas; 50 percent Fork of the Arkansas River undercut banks; 50 percent (above Tennessee Creek) overhanging vegetation; small- medium cobble in riffles and silt in pools; 0.5-2.5 feet deep. AR10 Downstream from County Road High gradient; all riffle; 300 where it crosses the large-medium cobble; 75 percent Arkansas River (above overhang; rocky banks; 0.5- California Gulch) 1.5 feet deep. AR20 Downstream from California Moderate gradient; alternating Gulch about 500 feet pool-riffle areas; small-medium cobble; heavily grazed; 10 percent vegetated, undercut banks; 25 percent eroding banks; 0.5-2.5 feet deep. AR45 Upstream from Smith Ranch Moderate gradient; pool-riffle Road where it crosses the areas; 20 percent undercut Arkansas River banks; 15 percent pools; 80 percent rocky banks ^mall- large cobble; heavy algal growth; 0.5-3.0 feet deep. AR65 Downstream from highway 24 Low-moderate gradient; riffle- where it crosses the run area; small cobble; heavily Arkansas River (Snowden grazed; 25 percent undercut Overpass) banks; heavy algal growth; 0.5-1.5 feet deep. HM1 Upstream from County Road Moderate gradient; mainly riffle crossing on Halfmoon area; 75 percent overhanging Creek, one-half mile from vegetation; small cobble; 10 confluence with Arkansas percent undercut bank; 0.5-1.0 River. feet deep. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION AR6 and AR65~ contained some poor habitat because of- swift, shallow water in the riffles, but undercut banks occurred in these areas. Station AR6 also had a large pool but the reach was narrow compared to other stations. Although the velocity at the uppermost station (AR3) was low and a small section of it contained undercut banks and a pool, much of it was bordered by sandy, grazed banks. The Halfmoon Creek reach (HM1) was a small, shallow tributary. Extensive overhanging vegetation was its best habitat feature. None of the fish sampling reaches was ideal habitat throughout its entire length, but good habitat was found at stations both upstream and downstream from California Gulch. Differences in habitat between stations probably explain only minor differences in trout standing crop between stations. Species Composition and Abundance. The fish community of the Arkansas River is dominated by brown trout (Tables 7.5 and 7.6). Rainbow trout (Salmo gairdneri) were found at two stations upstream from California Gulch (AR6 and ARID). Brook trout were more abundant in Halfmoon Creek, a small, shallow tributary, than in the Arkansas River. Cutthroat trout (Salmo clarki) were found in the Arkansas River upstream from California Gulch during the September and October samplings. Numbers of trout in September at all stations below California Gulch were significantly (P<0.05) lower than numbers at the station immediately upstream from California Gulch (AR10) and the uppermost station (AR3). The wide confidence interval about the population estimate at Station AR6 above Leadvilie precluded that estimate from being significantly greater than the estimate from the lowest station (AR65), but it is obvious that the density of trout is greater at the upper station (743 trout/acre at AR6, 50 trout/acre at AR65; Table 7.5). Wide confidence intervals are the result of a large standard error when the number of fish captured in the second pass is large

7-15 TABLE 7.5 FISH COLLECTED FROM THE ARKANSAS RIVER AND TRIBUTARIES DURING SEPTEMBER, 1985 Reach Reach No . of Elsh Mean Length Width .. Caught"" Height No. Flab. No. Fish Confidence Pounds Sampling Station (ft) (ft) Species 1st 2nd (Ibs) < 80 mm per Acre Interval per Acre

Arkansas River upstream of 700 23 BRN 64 29 0.25 0 389 V./ 275-503 89 Leadvllle (AR3) BRK 7 7 0.09 (58) Arkansas River below US Highway 24 A65 26 BRN 17 13 0.24 0 743 47-3652 178 above Leadvllle (AR6) BRK 1 0.03 0 (1484) BOW 7 9 0.24 0 Arkansas River above California 720 33 BRN 33 7 0.29 0 112 98-126 31 Gulch (AR10) BOW 10 4 0.26 0 (7) CUT 1 0.25 0 H 1 0.19 0 Arkansas River below California 600 33 BRN 1 No 2nd 0.44 0 4 6 1 Gulch (AR20) BOW 1 Pass 0.31 0 (0) Arkansas River at Smith 730 44 BRN 3 No 2nd 0.31 0 7 7 2 Ranch Road (AR45) BRK 1 Pass 0.06 0 (0) BOW 1 0.44 0 Arkansas River below US Highway 24 600 59 BRN 15 10 0.29 0 50 14-8169 below Leadvllle (AR65) BRK 3 0.13 . 0 (18) HaIfmoon Creek 440 21 BRN 8 No 2nd 0.19 0 (HM1) BRK 10 pass 0.20 0 No Estimate BOW 1 0.19 0 I/ BRN°Brown trout; BRK-Brook trout; BOW-Ralnbou trout; CUT-Cutthroat trout; H-Ralnbou x cutthroat hybrid. 2/ Ist-flrst pass; 2nd~second pass. Does not Include fish £ 80 urn. 3/ Trout £ 80 mm were not Included In the analysis. *~ 4/ Number In parentheses Is the standard error. 5/ When low end of confidence Interval Is less than zero, total fish captured Is used as lower end. TABLE 7.6 FISH COLLECTED FROM THE ARKANSAS RIVER AND TRIBUTARIES DURING OCTOBER, 1985 Reach Reach No. Fish Mean Length Width 1 Caught ' Weight No. Trout No. Fish Confidence Pounds Sampling Station (ft) (ft) Species ^ 1st 2nd (Ibs) < 80 ton per acre Interval ' per Acre Arkansas River above 700 23 BRN 66 25 0.27 6 338 A./, 295-381 85 Leadvllle (AR3) BRK 17 3 0.13 0 (22) 1 Arkansas River below US Highway 24 46465 26 BRN 16 15 0.19 0 280 40-520 70 ";;• above Leadvllle (AR6) BOW 9 3 0.40 0 (123) CUT 3 0.29 0 Arkansas River above California 720 33 BRN 16 6 0.31 0 120 82-158 38 Gulch (AR10) BOW 13 7 0.28 0 (19) CUT 2 0.31 0 H 5 3 0.44 0 Arkansas River below California 600 33 BRK 1 No 2nd 0.12 0 4 5 1 Gulch (AR20) BOW 1 Pass 0.44 0 (0) Arkansas River at Smith 730 44 BRN 17 10 0.63 0 60 36-84 34 Ranch Road (AR45) BRK 5 1 0.38 0 (12) LNS 2 0.31 0 Arkansas River below US Highway 24 600 59 BRN 14 5 0.53 0 32 21-43 15 below Leadvllle (AR65) BRK 2 1 0.19 0 (6) Halfmoon Creek (11M1) 440 21 BRN 9 4 0.30 0 172 58-286 40 BRK 7 5 0.16 0 (58) BOW 1 0.25 0 I/ BRN-Brown trout; BRK»Brook trout; BOW<*Ralnbow trout; CUT-Cutthroat trout; ll»Ralnbow x cutthroat hybrid; LNS-I.ongnose sucker. 2/ Ist-flrst pass; Znd-eecond pass. Does not Include fish _< 80 nn. 3/ Trout. < 80 mm were not included in the analysis ~~ 4/ Number**ln parentheses Is the standard error. 5/ When low end of confidence Interval is less than zero, total fish captured is used as lower end. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION relative to the/fiumber captured in the first pass. This usually occurs where the habitat makes capture, even of stunned fish, difficult. In September, before larger spawning fish migrated into the study area, the mean weights of trout were similar throughout the study area. Because fewer numbers of trout occurred downstream from California Gulch, the biomass (pounds/acre) was lower. A population estimate of trout in Half moon Creek was not calculated but the community was made up of small brown and brook trout. Based on the results of one shock- ing pass, it appears the density of trout was higher than that observed in the Arkansas River below California Gulch (Table 7.5). Results from the October sampling also showed that the trout density in the Arkansas River is greater upstream from California Gulch than downstream from it (Table 7.6). Again, a wide confidence interval about the estimate at the second station upstream from Leadville (AR6) prevented the estimate from being statistically different at the 95 percent level of confidence when compared to the two lowermost stations (AR45 and AR65). However, the density at Station AR6 was clearly higher than the two lowermost stations (AR45 and AR65). Biomass was still low downstream from California Gulch compared to upstream from it, but it was higher than in September because of the movement of larger mature trout into the area. Trout density in Halfmoon Creek, the reference tributary, was similar to the densities found at the sampling stations upstream from California Gulch, and greater than the densities found downstream from California Gulch. Although brown trout are strongly territorial, they normally migrate upstream to headwaters and tributaries to spawn during the fall. The results of the October sampling indicate that larger, mature brown trout had migrated into the lower portions of the study area. However, these trout had not migrated into or past the stream reach immediately downstream from California Gulch. Fish, including trout,

7-18 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION will avoid concentrations of metals or other contaminants that are well below chronic toxic concentrations. For this reason, polluted stream segments can become chemical barriers to fish movements. In September, the mean weight of brown trout was similar between stations. In October, however, the mean weight of brown trout upstream from California Gulch was 0.28 pounds with a 95 percent confidence interval of 0.24 to 0.32 pounds; downstream from California Gulch the mean weight in October was 0.59 pounds with a 95 percent confidence interval of 0.37 to 0.81 pounds. This indicates that in October the mean weight of brown trout in the Arkansas River below California Gulch was significantly (P<0.05) greater than the mean weight of brown trout collected upstream from California Gulch. The length-frequency distribution of brown trout, shown in Figure 7.2, displays this difference. Female brown trout typically mature at 3 to 4 years of age and males mature a year earlier (Carlander, 1969; Avery, 1985). Brown trout in the Arkansas River mature at a similar age (Colorado Division of Wildlife, 1986). Of the brown trout caught at the three sampling stations upstream from California Gulch, 5 to 19 percent were ready or nearly ready to spawn, whereas 58 to 67 percent of the brown trout taken downstream from California Gulch were ready or nearly ready to spawn. These observations further illustrate the movement of larger brown trout spawners into the lower study area, but not into the upper portion of the study area. Upstream from California Gulch where suitable substrate occurred in meandering, low-gradient reaches, active congregations of brown and brook trout (another fall-spawner) were observed. Downstream from California Gulch in similar types of habitat, no trout were observed. This information strongly suggests that while spawning occurred in the Arkansas River upstream from California Gulch, the spawning population was made up of smaller fish. Although small trout may spawn, their

7-19 FIGURE 7.2 LENGTH-FREQUENCY DISTRIBUTION OF BROWN TROUT FROM THE ARKANSAS RIVER OCTOBER, 1985

AR3 n = 91

AR6 a: uCO

AR10 oH n-22 Ou. I- Ou UflCJ Q. AR45 n=27

> 570

AR65 n = 19

LENGTH (mm) YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION reproductive potential is lower than that of larger fish (Avery, 1985). Larger trout had migrated into the study area in October. However, these fish had not moved past California Gulch to the good spawning areas upstream and there was no evidence that they were spawning downstream from California Gulch. Discussion of Contaminants Knowledge of both acute and chronic toxicities is important to understand the impact of metal pollution on an aquatic ecosystem. Acute (short-term) toxicities are the easiest impacts to detect because they can cause fish kills or the absence of aquatic organisms (either the absence of one or more sensitive species or complete absence of aquatic organisms) from a specific stream reach. The biota of a stream may be completely wiped out by an acutely toxic event, but after the toxins have passed through the system, relatively rapid recovery to pre-event conditions can occur. Acute concentrations are typically designated as LC5Q, the concentration which is lethal to 50 percent of the test organisms within a specified period of time, usually 96 hours. Chronic (long-term) toxicity responses are much more difficult to detect in a stream ecosystem, but in many situations chronic toxicity can have a much larger impact on the stream than impacts associated with periodic events that cause acute toxicity. Much lower concentrations of contaminants are required to produce chronic effects than are necessary to produce acute effects (death). Impaired physiological and behavioral functions are associated with chronic toxicity. Ab- normal or reduced growth, reduced reproductive potential, improper behavior patterns for feeding and reproduction, increased embryo mortality, and weakened resistance to disease and parasites are examples of damage from chronic toxicity. The chronic toxicity of a substance is usually expressed as maximum acceptable toxicant concentration

7-21 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION (MATC). The 'MATC is determined from laboratory studies and is the greatest concentration of a toxicant at which no chronic effects are expected to occur for the test species. Contaminants of Concern and Their Extent in the Arkansas River Water quality and sediment data from this and other studies (LaBounty et al., 1975; Roline and Boehmke, 1981) have shown that Cali- fornia Gulch is a major source of metals contamination in the upper Arkansas River, although some contamination occurs in the Arkansas River upstream from the Tennessee Creek confluence via the Leadville Drainage Tunnel. Tennessee Creek, Lake Fork, and Lake Creek dilute the contamination, but surface water metals concentrations consistently remain above EPA criteria for protection from acute toxicity at least to 1 mile below Lake Creek and above chronic toxicity criteria to Canon City (Table 7.12). An increase of an order of magnitude or more of zinc, copper, cadmium, and lead in the sediments downstream from California Gulch emphasizes the contamination of the aquatic system by these metals. Copper levels appear to decline near County Road 55 (AR70), but the other metals persist at high concentrations in sediments downstream to this point (Table 7.2). Water and sediment contamination of the Arkansas River are reflected in the bioaccumulation of these metals by macroinvertebrates at least 6.5 miles downstream from California Gulch. During spring runoff when sediments are suspended in the water column, macroinvertebrates generally contained much higher concentrations of metals than during low flow. Reported concentrations of the various metals in the Arkansas River and its tributaries near Leadville were evaluated in relation to reported acute and chronic toxicity ranges of each metal to aquatic organisms. Based on these evaluations, it was determined that lead,

7-22 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION copper, zinc, "and cadmium are the four most abundant metal contaminants in the upper Arkansas River that are highly toxic to aquatic life. These four metals have been identified as the metals of concern for aquatic life. For each of the metals of concern, the EPA has established guideline concentrations in water that should not be exceeded more than once every 3 years to protect aquatic life (U.S. Environmental Protection Agency 1980, 1985a, 1985b, 1985c). These guidelines were developed as acute toxicities (one-hour concentration) and chronic toxicities (96-hour concentration). These concentrations are not to be confused with acutely toxic concentrations such as a 96-hour I-C,-0. These criteria guidelines are meant to protect most aquatic life if they are not exceeded for the specified period more than once every 3 years. Extensive discussions on the toxic effects of these four metals occurs in the literature, most of which EPA reviewed and considered in es- tablishing its guidelines. EPA recommends using the acid-soluble measurement method to determine metals concentrations when conducting toxicity studies. Acid-soluble measurement provides a concentration that usually falls between total and dissolved concentrations. However, the guidelines were developed using data based primarily on total recoverable concentrations. EPA suggests cause for concern may exist if the total concentration of a metal is much above an applicable limit, even though the acid-soluble concentration is not above the limit (U.S. Environ- mental Protection Agency, 1985b). An extensive review of the literature by the EPA to establish these criteria revealed that, except for the chronic toxicity of zinc, both the acute and chronic toxicities of the four metals were inversely related to the hardness of the water. EPA developed equations to determine criteria for metals based on the hardness of the water (Table 7.7).

7-23 - ...;.-. TABLE 7.7 MAXIMUM ALLOWABLE CONCENTRATIONS (MG/L) OF SPECIFIC METALS IN WATER BASED ON TOXICITY DATA Water Hardnessi^rng/1) CaCo. Durat ion/Metal Equation 2/ 50 100 200 One-Hour Acute Toxicity Cadmium (1.128[ln(hardness)]-3.828) 0.0018 0.0039 0.0086 Copper (0.9422[ln(hardness) 1-1.464) 0.0092 0.0180 0.0340 Lead (1.273[ln(hardness)l-1.460) 0.0340 0.0820 0.2000 Zinc (0.83Un(hardness)]+1.95) 0.1800 0.3200 0.5700 — 96-Hour Chronic Toxicity Cadmium (0.7852[(ln(hardness)l-3.490) 0.00066 0.0011 0.0020 Copper (0.8545[(ln(hardness)1-1.465) 0.00650 0.0120 0.0210 Lead ®(1.273[ln(hardness)]-4.705) 0.00130 0.0032 0.0077 Zinc No equation 0.04700 0.0470 0.0470 I/ Allowable concentration is dependent on hardness of water except for 96-hour criteria for zinc. *•2'/ Equation results are in ug/1. Source: U.S. Environmental Protection Agency 1980, 1985a, 1985b, 1985c YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION

The toxicity criteria shown in Table 7.7 were developed for single metals and do not take into account synergistic or antagonistic effects metals may have on each other. For aquatic organisms, the presence of copper and zinc has a synergistic effect on the toxicity of cadmium (McKee and Wolf, 1963); cadmium has a synergistic effect on the toxicity of lead (Demayo et al., 1980); and copper and zinc together have a synergistic effect (McKee and Wolfe, 1963; Taylor and Demayo, 1980; Taylor et al., 1982). A synergistic effect of the metals of concern could be expected and probably make the metals more toxic than indicated by the EPA criteria. However, because site-specific criteria are absent, the EPA guidelines will be used to evaluate the impacts of the concentrations of these four metals on the aquatic ecosystem in the Arkansas River. Lead. Lead has been reported to cause spinal curvature and excessive mucous production on the gills. Mucous production on the gills can result in suffocation (McKee and Wolfe, 1963). Lead may also cause internal changes and affect the physical properties of the epidermal mucous (Demayo et al., 1980). The toxicity of lead in water is strongly related to the water hardness. Four-day exposures to lead near 1.0 mg/1 were toxic to trout in soft water, but trout could tolerate nearly 500 mg/1 when the water hardness was near 300 mg/1 (Table 7.8). Davies et al. (1976) reported a 20 percent mortality of rainbow trout at lead concentrations of 0.07 to 0.19 mg/1 in soft water, depending on the temperature. They also determined that long-term exposure to lead concentrations between 0.007 to 0.015 mg/1 caused deleterious effects, such as spinal deformities, in unacclimated rainbow trout. Acclimated rainbow trout and brook trout exposed for a short period (2 months) could withstand higher concentrations before effects were observed (Table 7.8). Spinal

7-25 I I 1 1 TAfl 7.81 I I I ACUTELY AND CHRONICALLY TOXIC CONCENTRATIONS OF LEAD TO TROUT

% Lethal 1 96-h Effect @ Chronic MATC' Species Hardness LC50 Cone. Effects 2/ - 3/ References (mg/1) GSg/T) (mg/rr (mg/i) (mg/1) Salmo gairdneri 290 542 Goettl et al., 1972; Davies and Everhart, 1973; Davies et al.t 1976 Salmo gairdneri 353 471 ibid '\i> Salimo galrdneri 28 1.2 ibid Salvelinus fontlnalis 44 4.1 Holcombe et al., 1976 Salmo galrdneri 30-34 20% @ 0.007-.015 Davies et al, 1976 0.19 unacclimated Salmo gairdneri 20% @ 0.004-.008 0.007 acclimated Salvelinus fontinalis <100 .058-. 119 Holcombe et al., 1976 Salmo galrdneri 28 Spinal Davies et al., 1976 Deformities 32% @ .027 44% @ .044 97% @ .062 Salmo gairdnerjt 35 Spinal Sauter et al., 1976 Deformitiee .102 s Salvelinus fontinalis 44 Spinal Holcombe et al., 1976 Deformities @ .083 I/ MATC - Maximum acceptable toxicant concentration 21 Concentration showing no effect 3/ Concentration giving deleterious effect YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION deformities were-observed in rainbow and brook trout at concentrations that were one to two orders of magnitude lower than acutely toxic concentrations (Table 7.8). Mean surface water concentrations of lead in the Arkansas River exceed EPA criteria for protection of aquatic life from chronic toxicity from downstream from the Leadville Drainage Trunnel to Canon City (Table 7.12). Mean lead concentrations throughout this length of the Arkansas River exceed concentrations which have been found to cause spinal deformities in unacclimated rainbow trout and deformities in about 50 percent of acclimated rainbow trout (Table 7.8). Lead concentrations throughout this length of the river have also reached concentrations which have been found to be lethal to about 20 percent of exposed rainbow trout (Table 7.8). Copper. The actual mechanism of copper toxicity is unknown (Deraayo et al., 1982a) although it is clearly toxic to aquatic organisms. Trout are among the more sensitive species to copper contamination. Acutely toxic concentrations have been found to range between 0.022 mg/1 and 0.37 mg/1, depending on the water hardness, species, and life stage (Table 7.9). McKim et al. (1978) reported that fish larvae and early juveniles of brook trout, rainbow trout, brown trout, lake trout, northern pike, white sucker, herring, and smallmouth bass were more sensitive to copper toxicity than embryos. Chapman (1978) found that the swim-up stage was the most sensitive early life stage of rainbow trout to copper toxicity. Trout weighing 0.7 and 10 grams were tested for sensitivity to copper toxicity and the larger fish were found to be 2.5 times more resistant (Howarth and Sprague, 1978). Copper concentrations which have been reported to be chronically toxic to trout are between 0.01 and O.OA3 mg/1 (Table 7.9). Copper concentrations ranging from 0.032 to 0.044 mg/1 were found to reduce the standing crop of brook trout, rainbow trout, brown trout, lake trout, white sucker, herring, and smallmouth bass (McKim et al., 1978).

7-27 111! TAlf- 7.9 [ [111 ACUTELY AND CHRONICALLY TOXIC CONCENTRATIONS OF COPPER TO TROUT % Lethal 96-h Effect @ MATC Species Hardness LC50 Cone . 2/ - 3/ References (mg/1) (IgTT) (IgTTT (mg/1) Salmo clarki 205 ,23-. 37 Chakoumakos et al., 1979 Salmo clarki 160 .091 ibid Salmo clarki 83 .162 ibid ";; Salmo clarki 74 .044 ibid Salmo clarki 70 .186 ibid Salmo clarki 18 .037 ibid Salmo gairdneri 361-371 .08-. 30 Howarth and Sprague, 1978 Salmo gairdneri 98-101 .031-. 176 ibid Salmo gairdneri 30 .02-. 03 ibid Salmo gairdneri 194 .08-. 51 Chakoumakos et al., 1979 Salmo gairdneri 120 .08 Selm et al., 1984 Salmo gairdneri 125 .190-.210 Spear, 1977; Anderson and Spear, 1980 Salmo gairdneri 36 .052 10% @ .022 Davies and Goettl, 1977 100 .056 20% @ .029 Salmo gairdneri .012-. 019 Goettle et al., 1977 acclimated .012-.019 ibid unacclimated [ I 1 TAT~ 7.9| '~>NTr"D) I I I I ACUTELY AND CHRONICALLY TOXIC CONCENTRATIONS OF COPPER TO TROUT % Lethal 96-h Effect @ MATC ' Species Hardness LC 50 Cone. 21 - 31 References Ug/i) ' (igTTT (ig/IT (mg/1) Salvelinus fontinalis 45 .010-. 017 McKim and Benoit, 1971 acclimated Salmo trutta 45 .022-. 043 McKlm et al., 1978 I/ Maximum acceptable toxicant concentration 2/ Concentration showing no effect 31 Concentration giving deleterious effects YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Decreases in the growth and survival of rainbow trout intermittantly exposed to copper were reported by Seim et al. (1984). Geckler et al. (1976) found that egg production of fathead minnows (Pimephales promelas) was significantly reduced at 0.037 mg/1 compared to no significant effect at 0.012 mg/1. Copper was found to bioaccummulate in the liver of rainbow trout exposed to copper concentrations of 0.003 to 0.037 mg/1 over a 48-week period (Goettl et al., 1974). Mean concentrations of copper in the Arkansas River exceed EPA criteria for protection of aquatic life from acute toxicity from downstream from the Leadville Drainage Tunnel to a mile below Lake Creek. Mean copper concentrations exceed criteria for protection from chronic toxicity to Canon City (Table 7.12). The mean concentration of copper downstream from California Gulch is similar to concentrations found to be lethal to 50 percent of exposed rainbow trout (Table 7.9). Copper concentrations found to be lethal to trout have been observed from upstream from the Leadville Drainage Tunnel to Canon City, but the frequency of occurrence of these concentrations is highest from Cali- fornia Gulch to downstream from Lake Creek (Table 7.12). The mean copper concentration below California Gulch is greater than concentrations found by several studies to reduce growth and reproduction of fish species more tolerant to heavy metals than trout. Bioaccumulation of copper in trout liver has been observed in the laboratory at the mean concentrations of copper determined for Arkansas River sites which extend downstream from the Leadville Drainage Tunnel to Canon City. Bioaccumulation of copper was found in the livers of trout taken from the Arkansas River from above Leadville to Salida. Furthermore, levels of copper in livers of trout taken downstream from the Leadville Drainage Tunnel to. Salida clearly increased with the age of the fish (Colorado Division of Wildlife, 1986a).

7-30 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION

Contamination of the Arkansas River with copper is also reflected in the bioaccuraulation copper by macroinvertebrates from the confluence of California Gulch at least to County Road 55, about 6.5 miles downstream. The importance of this contaminated food base to the pathway of bioaccumulation of copper by resident trout is suggested by differences in copper accumulation between hatchery trout raised in contaminated Arkansas River water and resident trout. The liver copper levels of yearling brown trout from the river contained more than three times as much copper as the yearling rainbow trout from the hatchery. Similarly, Eagle Lake yearling rainbows stocked in the Arkansas River in May-June 1985 and sacrificed in late October 1985 had significantly higher liver copper levels compared to the hatchery rainbows. The hatchery rainbows had an average liver copper accumulation of 218 micrograms (ug) Cu per gram(g) compared to an average of 491 ug Cu/g in the liver tissue of rainbow trout that had lived in the Arkansas River for approximately 6 months. Furthermore, a statistical comparison between yearling brown trout from the Arkansas River with yearling rainbows stocked in the Arkansas River indicated no significant difference in copper accumulation in the liver tissue (Colorado Division of Wildlife, 1986a). Trout in the river are receiving copper through the food source as well as surface water. Zinc. Zinc is more toxic to aquatic organisms than to terrestrial organisms. Zinc is thought to act on fish by forming insoluble compounds with the mucous that covers the gills, by damaging the epithelium of the gills, and possibly by poisoning the fish internally (McKee and Wolfe, 1963). Acutely toxic concentrations of zinc (described as LC_ concentrations) have been found to range from approximately 0.10 mg/1 to 7.00 mg/1, but are typically less than 1.0 mg/1 when water hardness is less than 100 mg/1 (Table 7.10). Chapman (1978) found that larval and juvenile rainbow trout were more sensitive to zinc than embryos or

7-31 I I [ I ABU .101 ( [ I ACUTELY AND CHRONICALLY TOXIC CONCENTRATIONS OF ZINC TO TROUT % Lethal 96-h Effect @ MATC Hardness LC 50 Cone. 2/ - 3/ Species (mg/1) (mg/1) (mg/1) (mg/1) References Salmo clarki .09 Rabe and Sappington, 1970 Salmo gairdneri, alevin 22 0.815 Chapman, 1978 swim-up 22 .09 ibid parr 24 0.136 ibid Salmo gairdneri 83 1.76 Chapman and Stevens, 1978 Salmo gairdneri 20 .09 Carton, 1972 Salmo gairdneri 350 1.19-4.52 Goettl et al., 1972 Salmo gairdneri 30 .24-. 83 Geottl et al., 1972 Salmo gairdneri 47 .37-. 76 Holdombe and Andrew, 1978 Salmo gairdneri 170-179 1.91-2.96 ibid Salvelinus fontinalis 44-47 1.55-2.4 Holcombe and Andrew, 1978 Salvelinus fontinalis 170-179 4.98-6.98 ibid Salvelinus fontinalis .96*' Nehring and Goettl, 1974 Salmo trutta .645/ ibid Salmo gairdneri 22 .24 30% @ .11 Davies and Geottl, 1977 Salmo gairdneri 23 .56 10% @ .13 ibid I i I ( -&BLT ' 10 [ | | | ACUTELY AND CHRONICALLY TOXIC CONCENTRATIONS OF ZINC TO TROUT % Lethal ,, 96-h Effect @ MATC Species Hardness LC 50 Cone. 2/ - 3/ References (mg/1) (ing/1) (mg/lj (mg/l) Salmo galrdnerl 23 90% @ 1.3 Ibid Salmo gairdneri 98 .80 20% @ .43 ibid Salmo galrdnerl 32 .43 30% @ .36 .036-. 71 Sinley et al., 1974 Salmo galrdnerl 32 90% @ .67 unacclimat Ibid Salmo galrdnerl .140-. 26 Ibid acclimated I/ Maximum acceptable toxicant concentration 2/ Concentration showing no effect 3/ Concentration giving deleterious effect 4/ 8-day exposure 5/ 9-day exposure YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION adults. Raihfcbw trout are generally the most sensitive species, followed by brown trout, while brook trout are the most tolerant species. Lethal effects to rainbow trout were found at concentrations of 0.13 mg/1, which caused a 10 percent mortality, to 0.67 mg/1 and 1.3 mg/1, which caused 90 percent mortalities (Table 7.10). Davies and Woodling (no date) found that instream bioassays correlated well with the findings of laboratory studies. A 100 percent mortality of resident brook and brown trout was observed in the Slate River within six hours where the zinc concentration was 2.78 mg/1. When the instream concentration of zinc was 0.35 mg/1, 50 percent of the unacclimated (hatchery-reared) rainbow trout exposed to the river water died within 72 hours. Hardness in the Slate River ranged from 44 to 128 mg/1. Sub-lethal effects of exposure to zinc have also been described. Hoi combe et al. (1979) reported that a zinc concentration of 1.4 mg/1 sufficiently reduced the strength of the chorion in brook trout eggs to cause serious problems during spawning. Consequently, the survival of embryos and 12-week larvae was significantly reduced. Rainbow trout have been reported to avoid solutions of zinc sulfate with a concentration as low as 0.0056 mg/1 (Taylor and Demayo, 1980). Mean surface water concentrations of zinc in the Arkansas River exceed EPA criteria for protection of aquatic life from acute toxicity from downstream from the Leadville Drainage Tunnel to one mile downstream from Lake Creek (Table 7.12). The chronic toxicity criterion for zinc is exceeded on an average basis downstream to Canon City. From the confluence of California Gulch to 2 miles downstream at the Smith Ranch Road, mean zinc concentrations are similar to those found to be toxic to 50 to 90 percent of exposed rainbow and brown trout within four to nine days (Table 7.10). Mean concentrations of zinc which have been found to be lethal to 20 percent of an exposed trout population are observed from downstream from the Leadville Drainage Tunnel to one mile below Lake Creek. Similar concentrations of zinc

7-34 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION

* have been observed to occur downstream to Canon City. Highly toxic concentrations of zinc occur regularly from California Gulch to two miles downstream at the Smith Ranch Road (Table 7.12). These concentrations are similar to those reported to cause 100 percent mortality of resident brook and brown trout within six hours (Davies and Woodling, no date). Mean concentrations of zinc which have been found to be lethal to the sensitive swim-up and parr life stages of rainbow trout occur downstream to Canon City. Cadmium. Cadmium has been reported to cause defective development of fish embryos and to change behavior patterns of fish (Reeder et al., 1979). Abnormal behavior, such as uncontrolled swimming and loss of equilibrium, in a number of fish species, especially the males, was also noted by Spehar (1976) and Benoit et al. (1976). These aber- rations were attributed to an inhibition of acetylcholinesterase, which is important in nervous functions. Cadmium has also been reported to cause bone deformities in fish (Muramoto, 1981a; 1982b). Cadmium is one of the most toxic metals to aquatic life. Concen- trations acutely toxic to trout have been reported as LC^'s which range between 0.001 and 0.03.1 mg/1, depending on water hardness, species, and life-stage (Table 7.11). A cadmium concentration of 0.0056 mg/1 was lethal to 95 percent of the test rainbow trout at a water hardness of 31 mg/1, and 95 percent of the test brook trout were killed by 0.012 mg/1 at a water hardness of 44 mg/1 (Table 7.11). Chapman (1978) found that larvae and juveniles were the most sensitive life stages of rainbow trout. Exposure to sublethal concentrations of cadmium has been found to lower the reproductive potential of brook trout by reducing the number of viable embryos produced and by retarding the growth of young trout. Reduced juvenile brook trout growth at concentrations of 0.0038 mg/1 and 0.0034 mg/1 were reported by Eaton et al. (1978) and Benoit et al. (1976), respectively. Benoit et al. (1976) further found that at

7-35 J ELM ) CJ ICAI T03( CONI .'RAH 5 01 DMIi K) 1 T I % Lethal 96-h Effect @ Species Hardness ( LC 50 Cone. 21 - 3/ References Tmg/1) «"s7iT (m8/1> Salmo gairdneri alevin 23 .027 Chapman, 1975, 1978 swim-up 23 .0013 ibid parr 23 .001 ibid smolt 23 .0029-. 0041 ibid Salmo gairdneri 31 .031 Davtes, 1976 55-79 .010 Spehar and Carlson, 1984 39-48 .023 ibid Salmo trutta 55-79 .015 ibid Salvelinus fontinalis 42 .0015 Carroll et al., 1979 Salmo gat rdneri 14 .003 40% @ .0024 Davies and Goettl, 1977 31 .003 5% @ .0015 ibid ,31 95% @ .0056 Davies, 1976 Salvelinus fontinalis 44 95% @ .012 Benoit et al., 1976 Salmo gairdneri .007-.0015 Davies, 1976 unaccllmated .0034-.0071 Goettle and Davies, 1976 acclimated .0017-.0034 Benoit et al., 1976 acclimated Salvelinus fontinalis .0011-.0038 Eaton et al., 1978 Salmo trutta .0038-.012 ibid H Maximum acceptable toxicant concentration 21 Concentration showing no effect 3/ Concentration giving deleterious effect 4/ 8-day exposure YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION 0.0034 rag/1 cadmium, male brook trout became hyperactive during spawning and died. Due to these effects on males, the mean number of fertilized embryos per female was reduced. Although the embryos which were fertilized survived through hatching and juvenile stages, weights of 16 week-old juveniles were significantly lower than control juveniles. The combined reduction of viable embryos per female and re- tarded growth of offspring markedly reduced the total weight of juveniles produced from exposed fish. Survival to sexual maturity was normal in second generation trout, but as with the first generation, males became hyperactive during spawning and died. Similar results were found for third-generation trout. Additionally, Reeder et al. (1979) concluded that the presence of cadmium during only a few days at .01 mg/1 to 0.025 mg/1 was sufficient to reduce the breeding capability of male brook trout due to hemorrhagic testicular necrosis. Cadmium accumulates in the liver and kidney tissue of trout (Benoit et al., 1976; Goettl and Davies, 1978). Liver cadmium levels reached 130 ug/g and kidney cadmium levels reached 180 ug/g after two years of exposure to 0.0035 to 0.0071 mg/1 cadmium. The maximum acceptable toxicant concentration has been determined to lie between 0.0007 mg/1 and 0.0015 mg/1 for unacclimated rainbow trout, and .0017 mg/1 and .0034 mg/1 for acclimated rainbow trout (Table 7.11). Similar suggestions have been made for brown and brook trout (Table 7.11). Mean surface water concentrations of cadmium in the Arkansas River exceed EPA criteria for protection of aquatic life from acute toxicity from the confluence of California Gulch to a mile downstream from Lake Creek, and mean cadmium concentrations which exceed the chronic criteria are observed to Canon City (Table 7.12). The mean cadmium concentrations recorded from California Gulch to below Lake Creek have been found to be lethal to 50 percent of exposed trout within four days (Table 7.11). Concentrations of cadmium which are lethal to 95 percent

7-37 TABLE 7.12 MEANS AND RANGES OP CONCENTRATIONS (MG/L) OF SELECTED HETALS IN WATERS OF THE ARKANSAS RIVER I/ WITH CONCENTRATIONS ABOVE EPA CRITERIA LEVELS NOTED Number of Hardness Location/Study Samples "•™*™™"™"™J"(CaCo..™ ) Cadmium Copper I xi ad Zinc Above Leadvllle Drain Rollne & Boehmke 1981 19 Mean 85 .0007 .0088 .0021 .0047 Range ,. 38-114 0-.007 0-.113 0-.0071 0-.03 Z chronic. ' 21 26 42 0 Z acute ' 5 0 42 0 Upstream of Tennessee Creek ^ Rollne & Boehmke 1981 17 Mean 142 .0029 .018 * .0048 .500 ** Range _. 46-258 0-.006 0-.215 0-.016 .22-. 70 Z chronic. ' 65 12 35 100 Z acute *' 23 12 0 71 Downstream of Tennessee Creek ^ Rollne & Boehnke 1981 IS Mean 107 .0022 .019 ** .0138 .4.4 ,** Range . 36-228 .0008-. 004 0-2.44 0-.130 .18-1.55 Z chronic. 80 27 67 100 Z acute *' 13 20 7 60 Above California Gulch Rollne S Boehmke 1981 19 Mean 108 .0024* .013* .015* .41 ** Range ,, 38-168 0-.004 0-.15 0-.17 .13-2.8 Z chronic/' 42 32 32 100 Z acute *' 0 5 5 26 Engineering-Science AR10 3 ND2> ND ND .15* .14-. 15 Below California Gulch Rollne & Boehmke 1981 19 Mean 128 .0084** .046** .037 * 1.57 ** Range 41-215 0-.01 .008-. 09 .003-. 110 .21-4.8 Z chronic . 3/ 84 89 89 100 Z acute " 68 63 16 100 Engineering-Science AR20 3 .005** .045** ND 1.86** .004-. 006 .043-. 046 1.77-1.95 Smith Ranch Road Rollne & Boehmke 1981 18 Mean 51 .0048** .0184** .029* .63** Range - 28-84 0-.02 .0007-.04 O-.ll .24-1.16 Z chronic . 3 93 80 87 100 Z acute 80 67 33 100 Engineering-Science AR45 1 ND .017** ND 0.6„ 4,,** TABLE 7.12 (CONTINUED) Number of Hardness Location/Study Samples (CaCo3) Cadmium Copper Lead Zinc Highway 24 Overpass ** ** ** Rollne & Boehmke 1981 19 Mean 47 .0036 .0142 .0348* .525 Range 32-88 0-0.12 .002-. 039 0-.215 .25-1.06 X chronic . 3/ 95 79 79 100 X acute ' 63 53 16 100 Engineering-Science AR6R65 1 ND .016** ND .313** County Road 55 Near Kobe ** Rollne & Boehmke 1981 15 Mean 55 .0036 ** .0145 ** .0488 ** .558 Range 32-84 .001-. 0085 .002-. 027 .005-. 15 .31-1.06 X chronic , 3/ 100 73 100 100 X acute 87 67 53 100 Below Lake Creek ** Rollne & Boehmke 1981 18 Mean 48 .003 ** .011 ** .038 ** .472 Range _. 36-76 0-.012 .0016-. 028 0-.14 .14-1.9 Z chronic q/. 89 67 94 100 X acute 61 55 44 94 . Engineering-Science AR9900 1 ND .007 ND 0.168* Near SalIda Colorado Department 2A-39 84 .0009* .007* .011* .154* of Health 1977-1985 38-130 0-.009 0-.021 0-.039 0-.480 Near Canon City Colorado Department 31-49 118 .002* .012* .019* .150* of Health 1977-1905 57-160 0-.049 0-.130 0-.140 .00 3-. 860 I/ Data of described sampling sites from 1979-1980 sample results In Rollne and Boehmke (1981). AR sample sites show August 1985 data taken by Engineering-Science at locations similar to those described. 2/ NONot Detected 3/ Percent of samples with concentrations above the EPA 96-hour criterion at the ambient hardness. Percent of samples with concentrations above the EPA 1-hour criterion at the ambient hardness. Concentration above EPA 96-hour criterion at the Indicated hardness. Concentration above EPA 1-hour criterion at the-Indicated hardness. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION of exposed treat have been frequently observed from - the California Gulch confluence to Canon City (Tables 7.11 and 7.12). Cadmium concentrations from California Gulch to Canon City consistently exceeded cadmium levels found to reduce trout growth and to cause death of males during spawning. Cadmium concentrations were also observed from California Gulch to Canon City which could have caused sufficient physiological damage through short-terra exposure to reduce the reproductive capability of resident trout without being lethal or even reducing growth (see the introduction to this section on contaminants of concern), Analyses of trout liver and kidney tissues revealed that trout from the Arkansas River from below the Leadville Drainage Tunnel to Salida contained burdens of cadmium similar to those of trout exposed in the laboratory to cadmium concentrations between 0.0017 to 0.0035 mg/1 (Colorado Division of Wildlife, 1986a). Liver cadmium levels were found to be highly significantly correlated to cadmium concentrations of Arkansas River water from upstream of the Leadville Drainage Tunnel to about a mile below Lake Creek. The effects on the trout population by bioaccumulation of cadmium can be inferred by a comparison of trout population estimates and cadmium content of tissue taken from trout at sites similar to the population estimate sites. High negative correlations were found between the cadmium content of liver and kidney tissues and the population density of trout from about the Leadville Drainage Tunnel to Salida. As the concentration of cadmium increased in tissues of trout, the trout density decreased. Kidney cadmium accumulation accounted for about 89 percent of the variation in the population of 2-year-old brown trout and about 94 percent of the variation in the population of 3-year-old brown trout (Colorado Division of Wildlife, 1986a).

7-40 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Concentrations of cadmium in kidney and liver tissue were also highly correlated with the age of the trout (exposure), except for 4-year-old fish which are rare in the Arkansas River brown trout population. The 4-year-old trout had relatively low levels of cadmium in these tissues. These results, in conjunction with those described above, suggest that only trout with a low cadmium burden in the liver and kidney survive beyond age four (Colorado Division of Wildlife, 1986a). These findings correspond well with the results reported by Benoit et al. (1976). In that study, brook trout accumulated compara- ble cadmium levels in kidney and liver tissue when water cadmium concentrations were similar to those observed in the Arkansas River. Male trout died upon reaching maturity and attempting to spawn. Male brown trout in the Arkansas River typically mature at two to three years. Impacts to the Aquatic Biota Resource Habitat degradation by metals contamination has reduced the capacity of the Arkansas River to support aquatic life from California Gulch to Salida. Aquatic macroinvertebrate density has been reduced immediately downstream from California Gulch. Further below California Gulch, the community structure is dominated by organisms more tolerant of metals and organic pollution but which provide an inferior food base for trout. The macroinvertebrate community downstream from California Gulch is also contaminated by bioaccumulation of heavy metals. The cumulative impact of acute and chronic toxicity from heavy metals, chemical barriers to spawning migrations, and an inferior, contaminated food base has led to a reduced trout population from California Gulch at least to four miles downstream. Work conducted in October and November 1985 by the Colorado Division of Wildlife (1986b) corroborated these fish population reductions and extended the decreased standing crop of trout to Salida. That study found the density of trout in the Arkansas River ranged from 617 to 1,067 trout per acre

7-41 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION upstream from-Tennessee Creek, but downstream from Lake Fork to Salida the standing crop ranged from 66 to 221 trout per acre. The reduced trout standing crop is attributable to heavy metals concentrations which reach lethal levels and to chronic exposure of trout to high metals concentrations. Concentrations of lead, copper, zinc, and cadmium between Cali- forniaa Gulch and Lake Creek regularly reach levels which as single metals are known to be lethal to trout within a matter of days. It should be emphasized that these metals occur in a complex and that within that complex are combinations observed to act synergistically. Copper and zinc have a synergistic effect on cadmium, and copper and zinc act synergistically. Because fish tend to avoid areas with toxic concentrations of contaminants, this severely polluted stretch of the Arkansas River may be repelling many trout. The impact of chronic exposure of the trout populations to sublethal concentrations of these metals is probably more severe and reaches further downstream than losses due to acute toxicity. The most important effect of chronic exposure of trout to metals in the Arkansas River appears to be a decline in the reproductive potential of the wild trout population. The factors reducing the reproductive potential are a chemical barrier to good spawning grounds, acute toxicity of sensitive life-stages, and the loss of large individuals from the spawning population due to bioaccumulation of cadmium. The data from this study suggest that contamination from Califor- nia Gulch has created a chemical barrier to larger trout seeking spawning grounds above California Gulch. These fish also appear to avoid suitable spawning sites in the contaminated reaches downstream from California Gulch. Even if spawning were accomplished in the few miles downstream from California Gulch, the viability of the eggs may be reduced due to high levels of zinc. Reduced contributions to the

7-42 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION annual reproductive effort by these migrating spawners because of a barrier to suitable spawning grounds would lower the reproductive potential of the upper Arkansas wild trout population. Young trout newly-emerged from redds produced by the population upstream from California Gulch may be swept into the severely polluted downstream reaches during spring runoff. Juvenile trout are more sensitive than adults to heavy metals and would be exposed to lethal metal concentrations for the period of time required to drift through four miles of highly contaminated water before being able to move to areas with more a tolerable water quality. Acute toxicity to these fish would further reduce the reproductive success of the wild trout population. Evidence strongly indicates that chronic exposure to cadmium is severely limiting the reproduction potential and the quality of the brown trout fishery of the Arkansas River from Leadville to Salida and perhaps to Canon City. Bioaccumulation of cadmium in brown trout kidneys and livers is firmly linked to water cadmium concentrations in the Arkansas River and to reduced densities of two-year and three- year-old trout. Upon reaching three years of age, brown trout in the Arkansas River are dying, probably due to the combined stresses of cadmium burdens, spawning, and overwintering. Not only is the quality of the fishery reduced without fish older than three years, but the reproductive potential of the trout population is severely limited due to the loss in numbers and maturity of the spawning population. The loss of so many miles of aquatic habitat and the degraded water quality is important to local economies, particularly those wishing to develop recreation resources as other resources, such as mining, decline. Free-flowing streams such as the upper Arkansas River are becoming increasingly rare and valuable because of the rising number of impoundments built to satisfy urban water demands. Demand for quality fisheries in streams such as the Arkansas River will

7-43 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION continue to grow, as Front Range urban growth continues. The upper Arkansas River would be particularly valuable as a quality fishery because of its scenic setting. Currently, the people of Colorado are being deprived of a potentially valuable fishery because of. heavy metal pollution from California Gulch to the Arkansas River.

7-44 CHAPTER 8 SOILS INVESTIGATION The soils resources of irrigated pastures and native grazing lands along lower California Gulch and the Arkansas River were investigated fby Engineering-Science from March to December, 1985^ Elevated concentrations of arsenic, cadmium, copper, lead, and zinc were found in soils affected by irrigation sources from the Arkansas River and California Gulch, at depths up to three feet. High soils metals concentrations have resulted in increased availability to plants and the likelihood of metals toxicity in livestock, via grazing of affected vegetation and direct consumption. Water quality is also affected due to decreased plant cover, and resultant soil erosion and sediment loading. Many of the contaminated areas displayed metals concentrations that either approached or exceeded the guidelines established to protect biota from toxic or lethal effects. High levels of soil zinc and cadmium, in particular, correspond to toxic symptoms found in livestock grazing in these contaminated areas. RESOURCES AND USE The soils in the Yak Tunnel/California Gulch study area vary from level or gently sloping terraces, flood plains, and swales adjacent to the Arkansas River, to sloping or very steep fans, terraces, and mountain side-slopes along California and Stray Horse Gulches east to the Continental Divide. Based upon publications by the U.S. Soil Conserva- tion Service (1975, 1983) and the U.S. Bureau of Land Management (1980), three general soil associations occur within the project area. The soils in the vicinities of California and Stray Horse Gulches are classed as the Troutville-Leadville association. These soils are deep,

8-1 - s._ YAK TUNNEL/CALIFORNIA GULCH 02/28/86 . REMEDIAL INVESTIGATION well-drained, gravelly loams and clays, and are derived from glacial outwash and till. The area directly adjacent to and including the Arkansas River has been classed as the Newfork-Marsh-Rosane association. These soils are moderately deep, poorly-drained loams and sandy loams overlying gravelly, sandy material. These soils are derived from mixed alluvium. The third soils grouping, located on nearly level to steep, high terraces along the Arkansas River, is the Pierian-Poncha association. These soils are moderately deep and well-drained, gravelly, sandy loams, and are derived from mixed alluvium and glacial outwash. All soils in the study area are classified as being capable of supporting land uses such as woodland, wildlife habitat, rangeland, and recreation. None of the lands in Lake County are considered to be Prime Farm- land or High Potential Dry Cropland (U.S. Soil Conservation Service, 1982). However, the soils identified as suitable for irrigation are classed as "Irrigated Lands, Not Prime," and are identified as being Farmland of ~ Statewide Importance. These soils, which account for approximately 2,300 acres within the study area, can be used as irrigated hay meadows. Specific soil series include the Newfork, Ouray, Rosane, and Poncha soils. Many of these irrigated soils are currently used to produce grass-clover hay for winter feeding in local livestock enterprises. Based upon an agricultural survey conducted during the summer of 1985, about 1,500 acres are currently irrigated with Arkansas River water downstream from the confluence with California Gulch between Malta and Kobe. In the past, up to 1,870 acres have been irrigated with Arkansas River or California Gulch waters. Changes in uses of Arkansas River water through the years have been caused by altera- tions of water rights and a concern for the quality of the waters (Seppi, 1985; Smith, 1985). Since the time of settlement in the Leadville area, agriculture has been an important land use in the form of irrigated, native hay

8-2 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION cropland and ranching. Beginning in the 1940's and continuing to the present, local farmers have noted clinical illness resembling zinc toxicosis in some livestock in the Arkansas River Valley below the confluence of the river with California Gulch /(Frank, 1981; Smith, 1984)77 Symptoms included below-average weight gains in livestock, including gains only 40 to 50 percent of normal. Local citizens have attributed this clinical disease to an increase in raining activity in the area during the early 1940's. Attempts by local ranchers to mitigate the toxic symptoms have included supplying supplemental copper to cattle feed and replacing Arkansas River water for pasture irrigation with water from other sources (Seppi, 1985; Smith, 1985). Pasture yields were reported to increase by up to 25 percent, and weight gains among livestock increased by 12 to 25 percent on lands removed from river water irrigation (Holier and Smith, 1985). Ranchers operating cattle on pastures irrigated with Arkansas River water feel that "cattie...cannot compete with cattle from other areas, causing economic losses" (Clotworthy, 1985, ranch manager for Hayden Ranch). Soil discoloration is evident in the surface and subsurface horizons of soils in both the California Gulch area and Arkansas River valley below California Gulch (Holler and Smith, 1985). Local citizens have attributed this occurrence to frequent discharges of metal-laden materials (often referred to as "yellow-boy") from California Gulch over a period of 50 years. NATURE AND EXTENT OF CONTAHINATION Physical and Chemical Soil Characteristics of Concern Numerous physical and chemical soil characteristics directly or indirectly influence trace metals mobility and toxicity. These factors ultimately influence plant germination, growth, and metals concentrations in plant tissues. Toxic concentrations of metals in plants result in livestock symptomology characteristic of chronic poisoning. 8-3 _ YAK TUNNEL/CALIFORNIA GULCH 02/28/86 . REMEDIAL INVESTIGATION Among the most Important soil factors controlling metals concentrations in plants are acidity, cation exchange capacity, percent organic matter content, and presence and chemical form of soil metals. Other important soil characteristics which interact with the above factors to influence soil metals mobility include soil fertility (availability of nutrients), temperature, moisture, and texture. The following discussion describes how each of these factors regulates metals mobility and toxicity in soils. Soil acidity, as indicated by pH, is often the most important parameter in controlling metals availability to plants (U.S. Environ- mental Protection Agency, 1983). As soil pH decreases, the solubility of many toxic metals tends to increase. Figure 8.1 depicts metal solubility in relation to pH. As solubility increases, the metals become more available for uptake by plants. Soil pH can also alter soil physical properties such as structure, permeability, water holding capacity, root penetration, and fertility, which can also affect metals availability for plant uptake. Soils high in organic matter tend to have high cation exchange capacities, which usually make soil metals less mobile. However, as the organic matter decomposes, conditions such as low pH, warm temp- eratures, and seasonal moisture will allow the metals to become mobile again. Low molecular weight humic acids, under low pH conditions, will increase the solubility of heavy metals. Trace metals occur in soils in a variety of forms. They are present as insoluble precipitates, are adsorbed by organic matter or on soil colloid exchange sites, or occur in soil solution (U.S. Environ- mental Protection Agency, 1983). If a metal is weakly adsorbed or is soluble, it can be made available for plant uptake or transport by surface water runoff. Metals in soil are thus analyzed and expressed in two different concentrations: total and extractable, or plant- available. The plant-available fraction of soils metals directly 8-4 SOLUBILITY (LOG ACTIVITY!

OCO 09 o *? mw CO > m Oa O"" 22 TO CO 39 (0 X m 00 —— Utf 1*c* m r 5CO ra CD m CO CO m•D Omm (mA . YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION affects vegetation response, although the level of total soil metals indicates the amount stored and gradually made available for plant uptake. Standards for soils metals concentrations adopted as guidelines by federal agencies have used total soils metals concentrations in determining soils metals loading rates considered phytotoxic to plants and animals. Therefore, technical literature that links physical and chemical soil characteristics with metals mobility must be used to infer potential plant toxicities based on total soil metals concentrations. Soil fertility is a measure of the occurrence of trace elements such as iron, copper, and zinc, as well as macronutrients such as nitrogen, phosphorus, and potassium. If the levels of metals are higher than those required for basic nutrition, adverse effects on plants can result. As discussed previously, soil acidity has an impact on the mobility of these elements. Soil temperature and moisture retention are also critical in determining metals mobility. Increased soil moisture increases the amount of soil water available to support chemical reactions, while increased soil temperature increases the rate of reactions (U.S. Environmental Protection Agency, 1983). Soil texture influences the metals-retaining capacity of soils through the presence of organic matter and its moisture content (U.S. Environmental Protection Agency, 1983). Toxic Substances of Concern Field studies, laboratory results, and statistical analyses demon- strate that several metals exist in concentrations potentially toxic to plants throughout the study area. The metals of concern in soils include arsenic, cadmium, lead, and zinc. Copper is of potential concern because of its synergistic relationship with other metals. Metals such as molybdenum and nickel were not found to differ throughout the project area during initial investigations, nor did they occur in soils at elevated concentrations considered by themselves to be potentially 8-6 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 """" REMEDIAL INVESTIGATION toxic to plants and animals. They were therefore eliminated from this discussion. However, a discussion of molybdenum and its relationship to livestock is found in Chapter 9. The previous metals are of concern for two reasons. First, the reported metals concentrations either approach or exceed the guidelines established to protect biota from toxic or lethal effects. Second, although levels of the metals may not exceed federal guidelines or phytotoxic thresholds, the metals act synergistically to influence potential toxicities of other metals occurring in greater abundance. A discussion of metals contamination in the soils of Stray Horse Gulch and California Gulch was presented in Chapter 4.0, Mining Waste Investigation. Table 8.1 summarizes the ranges of total soils metals concentrations found within the Arkansas River Valley study area, as well as ranges of soils metals concentrations found in normal uncontaminated U.S. soils (Lindsay, 1979). Ranges of total soil metal concentrations found to be phytotoxic to plants through research on agricultural and native lands are also included in Table 8.1. In this context, phytotoxicity is defined as a measure of plant stress and includes effects ranging from reduced growth to death. Federal guidelines in Table 8.1 refer to soils metals concentrations identified by the U.S. Environmental Protection Agency (1983), and the National Academy of Science (1972) as causing adverse effects on plants grown on irrigated agricultural lands. These guidelines are intended to provide a measure of how some plants will respond to differing levels of soils metals. Soils metals concentrations are not now regulated by federal agencies. Through the use of scientific literature, parallels between reported trends on agricultural and native soils metals concentrations were drawn with those trends identified on the study area. Figures 8.2 through 8.7 portray total soils metals concentrations occurring at the

8-7 --.,-..-- TABLE 8.1 RANGES OF TOTAL SOIL METAL CONCENTRATIONS IN REFERENCE LOCATIONS AND CONTAMINATED SITES AT THE YAK TUNNEL/CALIFORNIA GULCH STUDY AREA, ALONG WITH "NORMAL" LEVELS, REGULATORY LIMITS, AND KNOWN TOXIC LEVELS (mg/kg) Above Range of Calif- Below "Normal1/ Potentially Federal Control, ornia... California Levels ' Phy to toxic Guideline Metal Areas ' Gulch ' Gulch ' (Mean) Levels ' Levels 5/ — As 18-44 24-55 21-272 1-50 (5) >1Q6,7,8/ 300 Cd 0.9-2.3 2.8-6.9 1-50.01-0.0 7 (0.06) 2.S-56/ 3 ~~ Cu 6.4-44 24-69 17-750 2-100 (30) 70-6409'10' 250 4/r Pb 8.7-49 57-372 14-5,800 2-200 (10) i,ooo 1,000 Zn 30-108 151-693 101-19,200 10-300 (50) 300-2,000 2 ' 1 1 '/ 500 ~1/ Data collected by ES during summer, 1985 21 Normal range in uncontaminated U.S. soils (Lindsay, 1979) 3/ Variable among different plant species. -4/ U.S. Environmental Protection Agency, 1983 5/ Mean concentration within reported range 6/ Overcash and Pal, 1979 -7/ National Academy of Science, 1972 8/ Jacobs and Keeney, 1970 9/ Kline et al, 1979 .07 Mitchell et al, 1978 ^l/ Brown and Rasmussen, 1971, in EPA, 1983 FIGURE 8.2 RANGE OF TOTAL SOIL ARSENIC CONCENTRATION IN CONTROL AREAS AND AREAS ABOVE AND BELOW CALIFORNIA GULCH

FEDERAL GUIDELINE (EPA, 1983) 30O

250- _J O

O UZl 200-

150 o*• O* ~ - ou. *•E* Z O H I- 100- tZu ZO o 50-—

PHYTOTOXIC LEVEL (NAS. 1972) CONTROL ABOVE BELOW AREA CALIFORNIA CALIFORNIA SOILS GULCH GULCH SOILS SOILS RANGE (mg/kg) (18-44) (24-65) (21-272) FIGURE 8.3 RANGE OF TOTAL SOIL CADMIUM CONCENTRATION IN CONTROL AREAS AND AREAS ABOVE AND BELOW CALIFORNIA GULCH

5O-i

oCO 3s oi o 30- 2s

z 20- oH

UZl ZU o 10- POTENTIAL PHYTOTOXIC LEVEL FEDERAL GUIDELINE (OVERCASH AND 3- (EPA, 1983) PAL. 1979) / 0- L CONTROL ABOVE BELOW AREA CALIFORNIA CALIFORNIA SOILS GULCH GULCH SOILS SOILS RANGE (mg/kg) (0.9-2.3) (2.8-6.9) (1-50) FIGURE 8.4 RANGE OF TOTAL SOIL COPPER CONCENTRATION IN CONTROL AREAS AND AREAS ABOVE AND BELOW CALIFORNIA GULCH

1000-1

FEDERAL GUIDELINE (EPA. 1983) = 250- O CO oc POTENTIAL PHYTOTOXICITY U&l 100- -(KLINE, 1979JMITCHELL, 1978) u,0Q. 3O° -J o« I<-

z 3oO —o Hoe 10- Ul oz o

CONTROL ABOVE BELOW AREA CALIFORNIA CALIFORNIA SOILS GULCH GULCH SOILS SOILS RANGE (mg/kg) (6.4-44) (24-69) (17-750) FIGURE 3.5 RANGE OF TOTAL SOIL LEAD CONCENTRATION IN CONTROL AREAS AND AREAS ABOVE AND BELOW CALIFORNIA GULCH

10,000-1

0o) FEDERAL GUIDELINE (EPA, 1983) 2 1000- POTENTIAL PHYTOTOXIC LEVEL (EPA, 1983) O 111 s 100- 32

IU 10- Oz o

CONTROL ABOVE BELOW AREA CALIFORNIA CALIFORNIA SOILS GULCH GULCH SOILS SOILS

RANGE (rng/kg) (8.7-49) (57-372) (14-5800) FIGURE 8.6 RANGE OF TOTAL SOIL ZINC CONCENTRATION IN CONTROL AREAS AND AREAS ABOVE AND BELOW CALIFORNIA GULCH

10,000-

COO zo N Ul -1 o 1000- CO I- w FEDERAL GUIDELINE u o Jt, (EPA, 1983) i u. CD 500- O E cc 300- o O POTENTIAL PHYTOTOXIC o LEVEL (BROWN AND p RASMUSSEN, 1971, IN EPA, 1983) u zo 100- o

10- CONTROL ABOVE BELOW AREA CALIFORNIA CALIFORNIA SOILS GULCH GULCH SOILS SOILS

RANGE (mg/kg) (30-108) (151-693) (101-19,200) FIGURE 8.7 ARKANSAS RIVER VALLEY MAXIMUM AND MINIMUM TOTAL SOILS METALS

•siiV 1 1 n I™- 1'i.i n / y 1 r?ii u i f\ i !j T r i o 1 '' (5 j LJ i i f,/ i / /_j~EPA BELO WGUIDELINE CAL. GULCH I: r ABOVE CAL. GULCH UIKr i 'CONTROL

f-t C0 CJ£D CJ HEAVY METAL CONCENTRATION IN SOIL . _ YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Yak Tunnel/California Gulch site, compared to potentially phytotoxlc levels and federal guidelines or criteria (U.S. Environmental Protection Agency, 1983). Laboratory and statistical analyses indicate that the contaminated areas exhibit much higher ranges of metals concentrations than the control areas, for all five metals of concern. Furthermore, at least some samples from areas below California Gulch exceed normal concentrations, phytotoxic limits and federal guidelines for all of the metals except arsenic. Figure 8.7 displays the maximum and minimum concentrations encountered in the control areas and at sampling location above and below California Gulch and compares them to the EPA guidelines. The magnitude and severity of contamination by these five elements can be appreciated when it is recognized that the metal concentration values are plotted on a logarithmic scale. The increase in concentrations of soil metals below California Gulch is attributed to metals discharged from the gulch. Metals found In soils below the gulch occur In the same relative proportions to each other as metals in the soils and sediments within California and Stray Horse Gulches, but are usually found in much lower concentrations than in the gulches. Roline and Boehmke (1981) have demonstrated that concentrations of cadmium, copper, lead, and zinc increase in the Arkansas River water below California Gulch. Cadmium, copper, lead, and zinc concentrations also increase in the river sediments below California Gulch. Metals and contaminated sediments are transported downstream during spring runoff (Roline and Boehmke, 1981). Irrigation of haylands or pastures along the Arkansas River with the contaminated water was probably the means by which most of the metals were added to the soil system. Concentrations of cadmium and zinc at some irrigated locations immediately above California Gulch were found to be above both EPA guidelines and concentrations from the control areas. These high concentrations may be attributed to past Irrigation activities

8-15 - .._.-„-_ YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION using California Gulch water, as well as Arkansas River water during the period when the East Fork of the Arkansas River was actively releasing metals-laden materials discharged upstream. Other potential sources of soils contamination by trace metals were considered, but discounted as major sources of metals dispersion. These were (1) past smelter operations, and (2) application of ferti- lizer and other soil amendments. Smelter operations formerly occurring in the Leadville and Stringtown areas were considered because of their potential to disperse air-borne, metals-laden particulates to areas of the Arkansas River Valley and California Gulch. Studies performed by ES confirm that prevailing diurnal winds could disperse airborne pollutants over some distances. Studies by Buchauer (1973) confirm the impact of smelter emissions on zinc, cadmium, copper and lead soil levels. However, these studies found that the high metals concentrations occurred at a much closer distance to the emissions sources than those areas found within the Yak Tunnel/California Gulch study area. Also, the concentrations of all metals decreased sharply with depth in the soil profile unlike ES' results, which indicated high metals levels to depths up to three feet. Furthermore, if the smelters were to be a major source of soils contamination, it would be expected that reference areas nearto and below California Gulch would also contain elevated levels as great as those of the contaminated areas. This is not the case. Therefore, smelter emissions cannot be considered a major source of soils contamination. Application of fertilizers and sewage sludges were also discounted as major trace metals contributors due to their marginal uses by local ranchers (Smith, 1985; Seppi, 1985). Accumulation of toxic levels of soils metals due to application of nitrogen, phosphorus and potassium fertilizers and associated trace metals are rare occurrences, particularly in the absence of persistent use. Application of sewage sludge 8-16 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION has been documented in localized areas of the Arkansas River Valley below California Gulch, however, ES did not sample soils within these areas. Furthermore, to apply sewage sludge to the number of acres found which currently contain high levels of soils metals would be time-consuming, costly, inefficient, and in all likelihood, well beyond the means of local ranchers. Cumulative Geographic Extent of Contamination As indicated in the previous discussion, soil samples were obtained from four types of areas: Control or reference areas below California Gulch, which were relatively uncontaminated by mining activities but were similar in soil type and physiography and were proximal to the affected areas; Control or reference areas above the confluence of California Gulch and Arkansas River; . Contaminated areas below the confluence of California Gulch and the Arkansas River; and Contaminated areas in Stray Horse and California Gulches. Tennessee Creek and Arkansas River valley soil sampling locations are shown in Figure 8.8. Soil sampling locations in Stray Horse and California Gulches were included previously in Figure 4.1. Representative soil types in each area were sampled from the surface to six-inch depth range and at subsurface depths ranging from 6 to 36 inches, depending on the best available depth in the soil profile. Soil samples were collected using a 4-inch bucket auger and/or an Oakfield tube sampler. Each sample analyzed was a composite of three subsamples collected within a five-foot radius of the sample

8-17 FIGURE 8.8 SOIL SAMPLE LOCATIONS IN THE ARKANSAS RIVER VALLEY

DENVER AND RIO GRANOE WESTERN

V-LEAOVILLE DRAINAGE TUNNEL

\_ Stray Horst Gulch

ARSI5L ^California Sal ell ARS3nARS4 O ARS

ARS30* ARS3 ARS22A *

LEGEND • SOIL SAMPLE REFERENCE LOCATION o SOIL SAMPLE AFFECTED LOCATION 1/2 1 Mile BELOW CALIFORNIA GULCH O SOIL SAMPLE AFFECTED LOCATION ABOVE CALIFORNIA GULCH YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION point at equal radial and angular distances. One-third of the locations were randomly selected and subsequently sampled at a subsurface composite depth in order to provide a measure of the vertical extent of contamination. Each soil sample was analyzed for total and AB-DTPA-extractable (plant-available) levels of metals that are known to occur in raining wastes and that have high toxicities, that affect soil fertility and plant and animal nutrition, and/or that are potentially mobile. Phy- sical and chemical properties of the soils which affect the release of soil metals and influence plant growth were also analyzed. Sample sites and numbers of samples were chosen to assure representativeness for assessment of the geographical and vertical distribution of contamination. The results of analyses for total soils concentrations of arsenic, cadmium, copper, lead, and zinc at reference and affected sample locations in the Arkansas River Valley are presented in Table 8.2. The total concentration of these metals in the soil is an important indicator of the extent of contamination and potential for future release for plant uptake. With the exception of arsenic, areas below California Gulch that have been irrigated with water from the Arkansas River indicate a pattern of elevated metals concentrations, often by orders of magnitude, above metals concentrations found in control areas. This pattern is consistent with concentrations of metals found in river waters below California Gulch by Roline and Boehmke (1981). Based upon irrigation patterns in pastures below California Gulch, it is probable that the entire area of a pasture that contains several sampling points with elevated concentrations of metals will be contaminated. The acreage affected by either present or past use of Arkansas River water exceeds 1,800 acres.

8-19 TABLE 8.2 ARKANSAS RIVER VALLEY TOTAL SOIL METALS AND pH II

Soil Sampling Depth Total Metal Concentration (aig/kg) Location (inches) Arsenic Cadmium Copper Lead Zinc PH

Control: a TC-S-1A 0-6 30 1. 1 13 36 53 6 .29 24 TC-S-1B 24-30 aa 0. 6 7. 5 8.7 36 6 .42 TC-S-2A 0-6 25a 1. 6 13 39 56 6 .74 TC-S-2B 22-36 18a 0. 9 6. 4 9.2 30 6 .94 TC-S-4 0-6 44a 1. 5 44 23 100 6 .44 AR-S-22 0-6 28a 2. 2 16 49 78 6 .69 AR-S-18A 0-6 35 2. 3 20 37 108 7.01 2/ a Mean 29 a 1. 5 17 29 66 NA Surface Soil Mean 32a 1. 7 21 37 79 NA Subsurface Mean 21 0. 8 7 9 33 NA Above California Gulch: a ab Sb AR-S-3 0-6 24a 5. 2ab 45 210 516 6 .58 AR-S-4A 0-6 24a 4. 7a 24 130 290 8.97 AR-S-15 0-6 34a 2. 8 52 57 154 7 .06 AR-S-16 0-6 55 6. ab 69 372 693 6 .59 Mean 34a 4. 9a 43 192 424a NA Below California Gulch: a ab 793 ab ab AR-S-25A 0-6 a 50. 0a 230 5,800 6,100 a 6 .20 AR-S-25B 30-36 28 2. 5ab 21 102 440ab 6 .60 AR-S-26A 0-6 a 13. 0 59 190 l,400 7.00 AR-S-26B 30-36 2?a 1. 4ab 17 14a.b 210a.b 7.13 AR-S-5A 0-6 272 a 48. o 750aabb 4,500ab 7,900ab 6 .12 AR-S-5B 6-12 23 6a 40. Qab 700 4,000 8,600 6 .17 AR-S-23 12-18 32a 1. g3.D 25 44 160 5 .07 g 30 AR-S-24 0-6 31a 3. 3D vab 80aD 260ab 7.37 AR-S-19A 0-6 132a 16. o3D 270 4,OOO 8,600ab 3 .47 AR-S-19B 30-36 29a 4. 6ab 55a 380a.b 960a 4.70 AR-S-20 0-6 92a 40. 0ab 220 5,100 19,200arb 6 .76 AR-S-21 0-6 44a 35. ab 32a 800a.b l,400 7.23 AR-S-27 0-6 164 a 14. o 197 2,260 6 .16 AR-S-28 0-6 23a 3. 6ab 63a 309 337a^b 6 .76 AR-S-29A 0-6 53a 8. 4 132 192 999ab 6 .44 AR-S-29B ab 29?ab 10-17 75a 14. 0ab a 288 l,780a 6 .92 AR-S-30A 0-6 45a 33. 0 91a 749 2,180 ? 6.94 ab 1 AR-S-3 OB 6-12 36a 7. 5 82a 91aD. 7.01 AR-S-3 1 0-6 104a 48. 0ab 222 5,800 »°°°ab 6.99 AR-S-3 2 0-9 26a 1. 0 37 21 116a 6.68 AR-S-3 4 0-6 35 4. 4ab 44 153 330 7.89 TABLE 8.2 (continued)

Soil Sampling Depth Total Metal Concentration (mg/kg) Location (inches) Arsenic Cadmium Copper Lead Zinc pH AR-S-35A 0-6 53a 5.9ab 62 171 802ab 7.43 AR-S-35B 12-18 ab_ i_ 62 62 1;9o 7 .15 AR-S-39 0-6 36a 3 .7 63 356 8460 a 6 .89 7 51 105 AR-S-40 0-6 39a l-Qv Vab 63aD ia.b 7.78 AR-S-41 0-6 203a 14 ab 262a 5,020 1,420ab 3 .98 AR-S-42 0-6 41 26 .o• ll 82 118 3;240 7.50 a »ab a ab ab Mean 70a 16 • o ab « 144a l,403ab 2 ,569 NA Surface Soil Mean 75a 19aD 145a l,700 3,QQ7**ab NA Subsurface Mean 57a 8on 135 505 1,447 NA I/ Data collected by ES in June and August 1985, 21 Arithmetic means. a Concentration potentially toxic to plants. b Exceeds recommended EPA guideline _.,.. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION The Immediate phytotoxicity (toxicity to plants) of soils metals is indicated by the AB-DTPA-extractable soil metal concentrations. AB-DTPA-extractable data are presented in Table 8.3 for the sampling locations. Areas sampled below the confluence of California Gulch with the Arkansas River exhibit substantially increased levels of available soils metals of concern, except arsenic. Maximum and minimum levels of plant-available metals are portrayed in Figure 8.9. Phytotoxic concentrations presented in Figure 8.9 are based on total concentrations of metals in soils. This figure suggests that plant-toxic levels of cadmium, and possibly zinc and lead occur in some affected areas below California Gulch. These metals are acting synergistically with each other, and in some cases, high zinc levels are reducing cadmium availability. Analyses of total soils metals indicate that the highest concentrations of most metals analyzed occur in irrigated areas of the Seppi Ranch (AR-S-27 and AR-S-29), the Smith Ranch (AR-S-20 and AR-S-31), the Hayden Ranch (AR-S-25, AR-S-38, and AR-S-41), and selected wetland areas adjacent to the Arkansas River (AR-S-19 and AR-S-37). These areas exceeded recommended EPA guidelines for soils metals loading rates for at least three metals: cadmium, lead and zinc. Plant- available cadmium and zinc from numerous, affected, irrigated areas were also found to exceed total metals guidelines established by the EPA (U.S. Environmental Protection Agency, 1983). Areas with metals concentrations exceeding EPA guidelines also exceed the minimum levels at which plant-toxic effects would occur. The majority of high concentrations are evident in the surface layers (0 to 6 inches); however, decades of irrigation have caused leaching of metals to depths up to, and possibly exceeding, three feet. Evidence of significantly elevated plant-available concentrations of soils metals in affected areas indicates that application of irrigation water onto pasture lands has elevated soils metals concentra-

8-22 TABLE 8.3 -ARKANSAS RIVER VALLEY PLANT-AVAILABLE METALS I/ Soil Sampling Depth Plant- Available Metal Concentration (rag/kg) Location (inches) Arsenic Cadmium Copper Lead Zinc Control: TC-S-1A 0-6 1.2 0.2 4 14 3 TC-S-1B 24-30 1.6 0.1 3 3 1 TC-S-2A 0-6 1.0 0.6 4 17 5 TC-S-2B 22-36 1.2 0.1 1 1 1 TC-S-4 0-6 1.9 0.3 3 6 3 AR-S-22 0-6 1.4 0.7 5 17 8 AR-S-18A 0-6 1.0 0.6 5 12 11 Mean2' 1.3 0.4 4 10 5 Surface Soil Mean 1.3 0.5 4 13 6 Subsurface Mean 1.4 0.1 2 2 1 Above California Gulch: AR-S-3 0-6 1.0 2.8° 11 70 228 AR-S-4A 0-6 1.6 2.2 8 38 84 AR-S-15 0-6 0.6 ab 6 13 14 AR-S-16 0-6 0.8 °'.3 11 105 289 Mean 1.0 2.5' 57 154 Below California Gulch: AR-S-25A 0-6 1.6 30. Q v 38 320 940 v AR-S-25B 30-36 1.6 0.9 ab 5 50 176a,b AR-S-26A 0-6 2.0 7.6 7 24 500 AR-S-26B 30-36 1.6 0.3ab a4 3 66ab AR-S-5A 0-6 1.4 u!s aQ bVk 80a 30 560aa bPI AR-S-5B 6-12 1.0 10.6 70 24 580 AR-S-23 12-18 1.0 0.5 7 14 40 AR-S-24 0-6 1.0 1.4 ab 7 22 56a AR-S-19A 0-6 1.2 6.6 38 3 340 AR-S-19B 30-36 1.0 2 5 4 420 AR-S-20 0-6 1.8 17 '°a8 b 24 ab 2 ' ab 136 74of AR-S-21 0-6 1.2 ab 7 178 420 AR-S-27 0-6 1.5 °'°a6.1b 43 528 258 AR-S-28 0-6 0.4 21.83 21 119 61 AR-S-29A 0-6 1.2 29a 31 97 AR-S-29B 10-17 1.6 2.7' a\ 70 26 108 AR-S-3 0 A 0-6 3b a 1.0 14.02 8 7 63 319 AR-S-3 OB 6-12 1.0 ab 13 12 2623 AR-S-3 1 0-6 2.5 18.0' ab 20 130 334 AR-S-3 2 0-9 1.6 0.2 4 5 12 AR-S-34 0-6 1.4 1.5 6 30 30 TABLE 8.3 (continued) Soil Sampling Depth Plant- Available Metal Concentration (mg/kg) Location (inches) Arsenic Cadmium Copper Lead Zinc AR-S-35A 0-6 1.3 1.3 8 34 179 AR-S-35B 12-18 1.5 0.2 3 4 9 AR-S-36A 0-6 1.8 0.32 9 11 13 a AR-S-36B 12-18 1.5 15°' ab 7 4 3_ AR-S-37 0-12 1.1 ab 4 29 383 AR-S-38A 0-6 1.5 12.0-°ab 27 47 391 AR-S-38B 12-22 1.1 2.9\ab 5 8 262 AR-S-39 0-6 1.2 3.7 17 130 164 AR-S-40 0-6 1.5 0.37 5 14 556 AR-S-41 0-6 1.7 ab 19 172 a AR-S-42 0-6 2.1 15.0°' ab 3 4 490a

ab Mean 1.4 9.8 ab, 19 69 259 Surface Soil Mean 1.4 12.6a 18 90 276 Subsurface Mean 1.4 2.6 21 17 214 II Data collected by ES in June and August, 1985. 2/ Arithmetic mean. a Concentration potentially toxic to plants. b Exceeds recommended EPA guideline for total concentration. FIGURE 8.9 ARKANSAS RIVER VALLEY MAXIMUM AND MINIMUM PLANT-AVAILABLE SOILS METALS

n _PHYTOTOXIC BELOW CALGULCH f_ABOVECAL GULCH CONTROL

t~ijar CO S S £L03 HEAVY METAL CONCENTRATION IN SOIL YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION tions to phytotoxic levels. Evidence of zinc and cadmium toxicosis in farm animals grazing on vegetation is evident on the Smith Ranch, particularly in the vicinities of sampling points AR-S-20 and AR-S-31 (near vegetation sampling point ARV-5). At this sampling point, cadmium was detected in both soils and vegetation at plant-toxic levels. Further discussion of the localized effects of elevated soils metals on livestock is provided in Chapter 9. Visual examination of the soils containing elevated levels of one or more metals confirm that plant-growth inhibition is occurring in these areas. Barren areas, which frequently contain visually apparent iron oxides, correspond with those areas containing highly elevated metals concentrations. Areas of particular note include sample points AR-S-5, located along California Gulch, AR-S-19, located along the Arkansas River above Lake Fork; AR-S-20 and AR-S-31, located on the Smith Ranch; and AR-S-25, located on the central portion of the Hayden Ranch. These areas have soil pH's ranging from strongly acidic to neutral (3.5 to 7.0). These lower pH materials increase the availability of soils metals for plant uptake. The implications of the loss of plant cover are increased wind and water erosion, contribution of sediment to adjacent waterways, loss of nutrients, and decreased soil productivity. Statistical Analysis of Data Soil metal concentrations were subjected to statistical analyses, including Analysis of Variance (ANOVA), a powerful test that determines whether or not two populations can be considered significantly different at a high level of confidence. Where ANOVA could not be used because of overlap in data, Kruskal-Wallis statistics were employed. The results of these analyses are shown in Engineering-Science Appendix E, Tables E-l and E-2, for total metals and AB-DTPA-extractable metals, respectively. The Bartletts test of homogeneity of variances was also

8-26 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION performed and the results are presented as footnotes In Tables E-l and E-2 (Engineering-Science Appendix E) for all metals assayed, both for actual concentrations and for the logarithms of their values. For total metals, ANOVA and Kruskal-Wallis statistics indicate with a very high degree of confidence (99.9 percent) that the samples obtained from contaminated areas below California Gulch are significantly higher in cadmium, copper, lead, and zinc than those obtained from control areas. For arsenic, the level of confidence for the difference is 95 percent. A similar pattern of significance for the elevated concentrations of plant-available soil metals was observed for the contaminated versus control areas (Table E-2, Engineering-Science Appendix E), except in the case of arsenic where confidence levels below 95 percent do not permit designation of the significant difference. A statistical test was performed to determine whether or not the AB-DTPA-extractable concentrations of each metal in the soil correlated with the corresponding total concentrations of soil metals at each sample location throughout the study area. The correlation coefficients obtained did not indicate a significant relationship between total and plant-available fractions for any of the five metals of concern. The results are shown in Engineering-Science Appendix E, Table E-3. The main reason for this lack of correlation is that variables such as pH, cation exchange capacity, moisture content, organic matter content, and soil mineral composition, which affect soils metals solubility and extractability, play widely different roles at different locations. The relevant parameter, however, Is the reservoir of total metals tied up temporarily on the soil exchange sites. The metals are complexed with organic matter and held in precipitated forms until the exchange sites are re-occupied, the organic matter is decomposed, or soil chemistry (pH, redox potential) is changed. These changes are constantly taking place as seasons

8-27 . YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION change and as external weathering processes, as well as human activities, occur. In the California Gulch/Yak Tunnel study area, this has resulted in gradual releases of soils metals, that are available for plant uptake, over a period of years. Metal Concentrations The following discussion describes each metal's concentration, persistence, transport pathways and potential receptors, and implications to other resources. Soil physical and chemical factors that influence each metal's potential toxicity are also discussed. Arsenic Reported arsenic concentrations in uncontaminated U.S. soils range from 1 to 50 ppm (Lindsay, 1979), a range within which reference area soils fall. Total arsenic was detected in contaminated areas at concentrations up to six times the highest concentration found at a reference location (see Table 8.1). As indicated on Table 8.2, five sample locations had total soil concentrations of arsenic at least 10 times greater than the minimum level in soils considered phytotoxic to plants (10 ppm; U.S. Environmental Protection Agency, 1983). These areas were located along California Gulch, the Arkansas River, and In irrigated areas throughout the Arkansas River Valley. However, there were no sample sites that exceeded EPA (1983) guidelines for total soil arsenic. Areas of high total soils metals concentrations nearing the EPA guideline for arsenic (300 ppm; U.S. Environmental Protection Agency, 1983), such as AR-S-5 in California Gulch, indicate the presence of a large arsenic reservoir. Under a reduced soil condition (which occurs in intensely irrigated areas and in Arkansas River Valley wetlands and lowlands), the stored arsenic could be solubilized under low pH conditions and made available for plant uptake and transport by surface or ground waters.

8-28 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION

The availability of soil arsenic to plants is primarily a function of soil clays, soil moisture conditions, and acidity. Plant-available soil arsenic concentrations as low as 10 ppra causes moderate to severe toxicity in some plants (U.S. Environmental Protection Agency, 1983). Potential transport pathways for arsenic at the Yak Tunnel/Calif- ornia Gulch site include surface water and airborne dispersion. The immediate potential receptor of soil arsenic is vegetation. A moderate level of total soil arsenic occurs throughout the study area, with the exception of the five previously mentioned areas. However, based upon plant lab analyses for arsenic, few effects on plants from plant- available arsenic seem to be evident. The absence of such effects is explained in Chapter 9. Cadmium Reported cadmium contents in normal, uncontaminated U.S. soils range from 0.1 to 0.7 ppra (Lindsay, 1979), a value that was exceeded by all but one of the reference sites. This high level may be due to a higher than normal level of cadmium naturally occurring in the soils in the Leadville area. Despite this occurrence, total cadmium was detected in affected areas below California Gulch at levels up to 22 times the highest reference level (see Table 8.1). The study area locations with the highest total cadmium concentrations were primarily irrigated lands below the confluence of California Gulch with the Arkansas River. Sample locations above the confluence also showed elevated values as compared to the control points. This may be attributed to past irrigation with contaminated waters from both California Gulch, and the East Fork of the Arkansas River downstream from the the Leadville Drainage Tunnel. However, the highest cadmium value from above the confluence is only 14 percent of the highest value detected below California Gulch. Numerous sample locations throughout the irrigated areas of the Arkansas River Valley exceed potentially phytotoxic levels and EPA guidelines for cadmium, with a high of 50 ppm occurring

8-29 . .._ YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION at point AR-S-25. Soil cadmium concentrations were found to be significantly higher in both total and plant-available concentrations in contaminated areas versus reference areas, at the 99.9 percent confidence levels. The geometric mean concentration of total soil cadmium at all affected locations below California Gulch is 8.97 ppm, which is 7.2 times the average geometric mean reference level (1.25 ppm) and 3.0 times the federal guideline established for cadmium (U.S. Environmental Protection Agency, 1983). Cadmium mobility in soils is dependent primarily upon pH, cation exchange capacity (CEC), and ionic strength (Griffin et al., 1977). Cation exchange capacity data in the study area indicate that average or normal reactivities are occurring at affected locations and suggest that CEC is an important, though not a predominant, factor in affecting cadmium availability to plants. Cadmium is most available to plants in the divalent, Cd2 + , form. When compared to other metals like lead, cadmium is much more mobile and available to plants (Santillan-Medrano and Jurinak, 1975). Toxic effects in plants are induced by very low levels of soil cadmium, as evidenced by the EPA guidelines. Within study area sampling locations found to have high cadmium concentrations, plants either showed stressed growth or were nonexistent. Such areas occur in California Gulch (AR-S-5), along the Arkansas River (AR-S-19 and AR-S-37), and on portions of the Smith and Hayden ranches (AR-S-20, AR-S-31, and AR-S-25). Surface water is the primary transport pathway for cadmium. Based upon geochemical information as provided in previous sections, potential cadmium sources include the tailings ponds and waste piles and the

8-30 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION stream sediments found in California and Stray Horse Gulches. Re- ceptors of cadmium released from these sources are soils, vegetation (through root translocation), livestock (through water, vegetation, or direct soil consumption), and surface water. Lead Total soil lead was detected in affected areas at concentrations almost 120 times the highest reference value (see Table 8.2). The reported range of concentrations of lead in uncontaminated soils is 2 to 200 ppm (Lindsay, 1979), a range within which all of the values from the reference areas fall. The EPA guideline for lead has been established at 1,000 ppm in areas restricted for human use, although concentrations of lead below 1,000 ppm have been known to produce toxic effects in plants (Koeppe, 1981; Kovda et al., 1979; Overcash and Pal, 1979; U.S. Environmental Protection Agency, 1983; Wilkens, 1957). Study area locations with soil lead levels exceeding EPA guidelines are located in California Gulch, along the Arkansas River, and throughout irrigated areas of the Smith and Hayden ranches. Total lead concentrations in contaminated areas were found to be significantly higher than those found in reference areas at the 99.9 percent confidence level (see Engineering-Science Appendix E). The geometric mean concentration of total lead from all reference locations is 25 ppm. The geometric mean concentration of total lead at all locations below California Gulch is 347 ppm, or 14 times the average reference value. Analyses of plant-available lead concentrations in soils indicated a significant difference between reference and affected areas at the 95 percent confidence level. Some locations occurring on the Seppi, Smith, and Hayden ranches exhibit high plant-available soil lead concentrations that could induce plant toxic effects. Levels of plant-available lead in the surface layers of soil below California

8-31 - ... YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Gulch averaged 1.6 times higher than those above the gulch. These levels correspond with those obtained from plant tissue analyses at the same sites, indicating a fair degree of lead mobility. Many variables affect lead availability from soils to plants. Lead uptake by plants is generally favored by low pH's and low organic matter (Demayo et al., 1982a). Generally, lead is retained in soil in its hydroxide form, which is relatively insoluble. In addition, binding mechanisms such as soil moisture and chelating clays usually make soil lead relatively unavailable to plants except under certain conditions. However, under reduced, acid conditions, lead availability and uptake by plants is enhanced. When lead accumulates in soils, most will collect in the litter and humus layers. These sites favor lead uptake by shallow-rooted plants. Current levels of lead found in vegetation at points ARV-5 and ARV-4 on the Smith Ranch, ARV-2 on the Seppi Ranch, and ARV-7 and ARV-8 on the Hayden Ranch suggest that sufficient lead is already available in the soil for plants to accumulate toxic concentrations of lead (see Chapter 9). Barren ground that will not support vegetation also attests to the toxicity of this metal in the soil, either by itself or synergistically with other heavy metals from mining. In addition, the total lead concentrations found in some study area soils represent a tremendous reservoir of this toxic element, which can be mobilized in the environment given a change in soil chemistry. As natural processes, such as the decomposition of organic material in the soil and the oxidation of sulfide-rich minerals (which increases soil acidity), make soils lead available, toxic effects of lead to plants and animals will be manifested. Zinc The highest total zinc concentration detected in affected areas was almost 180 times the highest reference area value (see Table 8.2). Reference area concentrations of total zinc ranged from 30 to 108 ppm,

8-32 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION which is within the reported normal range of concentrations in uncontaminated soils of 10 to 300 ppm (Lindsay, 1979). The EPA guideline for total soil zinc is 500 ppm (U.S. Environmental Protection Agency, 1983); however, levels as low as 300 ppm in soils have caused adverse effects in plants (Broawn and Rasmussen, 1971 in U.S. Environmental Protection Agency, 1983). Numerous locations in the study area exceed the federal guideline for total zinc. These locations are found throughout irrigated pastures in the Arkansas River valley, particularly on the Smith and Hayden ranches. Two locations in irrigated areas above California Gulch slightly exceed the EPA guideline. These two areas had either been irrigated in the past with California Gulch water or were influenced by waters of the East Fork of the Arkansas River (Seppi, 1985). Total zinc concentrations in contaminated areas below California Gulch were found to be significantly higher than those found in reference areas at the 99.9 percent confidence level (see Engineering- Science Appendix E). The geometric mean concentration of total zinc at all reference locations is 63.1 ppm, well within the range considered to be normal in uncontaminated soils (Lindsay, 1979). The geometric mean concentration of total soil zinc at contaminated locations below California Gulch is 1,000 ppm, or 15.8 times the average reference value, and twice the EPA guideline established for soils (U.S. Environmental Protection Agency, 1983). Thirteen locations contained plant-available zinc levels above the EPA guideline of 500 ppm total soil zinc, and were within the range of the total soil zinc concentration known to be phytotoxic to plants (Table 8.2). Statistical analyses indicate that a significant difference exists for plant-available zinc between reference and contaminated areas, at the 99.9 percent confidence level (see Engineering-Science Appendix E).

8-33 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION The geometric mean, plant-available soil zinc concentration in reference areas was 3.2 ppm. The geometric mean concentration of plant- available soil zinc in contaminated areas below California Gulch was 125.9 ppm. Zinc generally accumulates more in surface soil horizons than subsurface horizons because of cation exchange capacity and the formation of organic complexes. Zinc has been shown to be more available in the presence of high organic matter and low pH (Taylor et al., 1982). Zinc is predominantly available in the divalent form, Zn2+ , over a wide pH. It has also been demonstrated by several studies to be more available to plants in moderately acid to strongly acid conditions than under alkaline conditions (Tisdale and Nelson, 1966). By releasing chelatlng agents, plants can readily absorb zinc, which is an essential element. Zinc can, however, be toxic at elevated levels. Buchauer (1973) has reported that levels of 200 ppm and 20 ppm of zinc in plants can cause toxicosis and chlorosis, respectively. Therefore, based on the high, plant-available, soil zinc levels at some locations in the Arkansas River Valley, it is probable that current zinc levels are detrimental to plants. Zinc is a highly mobile and soluble element and has a high potential for widespread dispersion throughout the study area. Zinc occurs in concentrations exceeding one percent in sediments along Stray Horse and California Gulches, and these areas appear to be sources of zinc which is discharged into lowland areas of the Arkansas River Valley, which contain high organic matter (a prime zinc-accumulating condition). Locations with high zinc levels adjacent to California Gulch and the Arkansas River (AR-S-5, AR-S-19, and AR-S-37), suggest that surface water is the transport mechanism for depositing zinc downstream. Judging by the locations of some of the highest concentrations of total soil zinc, surface water also appears to be transporting zinc onto irrigated areas of the Arkansas River Valley. 8-34 YAK TDNNEL/CALIFORNIA GDLCH 02/28/86 REMEDIAL INVESTIGATION

Copper The geometric mean total soil copper concentration at affected locations (87 ppm) is 5.5 times as high as the geometric mean concentration in reference areas (16 ppm). Significantly different total metals concentrations occur between reference and contaminated locations, at the 99.9 percent confidence level. Of the four sites exceeding EPA guidelines for copper, there is one that greatly exceeds the others for reported total soil copper concentrations. This is site AR-S-5, located in California Gulch. There are no locations that contain plant-available copper concentrations within the range reported to be detrimental to some plants (Demayo et al., 1982b; D.S. Environmental Protection Agency, 1983). However, statistical analyses indicate a significant difference in plant-available concentrations of copper between affected areas and reference areas at the 99.9 percent level of confidence. The geometric mean, plant-available copper concentration at contaminated locations is 12 ppm, versus 3 ppm at reference sites. Detrimental effects of copper toxicity include reduced germination rates, seed viability, and plant growth. Copper adsorption generally occurs in plant roots as a result of its accumulation in the upper soil horizons and organic layers (Tisdale and Nelson, 1966). It is primarily influenced by pH, clay content, the presence of iron and manganese oxides, and organic matter. The presence of iron at locations such as AR-S-5 and AR-S-19, which contained visible iron stains on rocks and within the sediment to a depth exceeding three feet, and low pH's such as at point AR-S-19, where the pH was below 4.0, indicate an enhanced copper-availability condition. Surface water is a major transport pathway of copper to soils. Portions of the Hayden and Seppi ranches and streambank areas of the Arkansas River are accumulating elevated amounts of copper in relation

8-35 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION to control areas. Sediment data from California and Stray Horse Gulches indicate a large reservoir of copper is available for release downstream towards the Arkansas River. Vertical Distribution of Metals in Soil Profile As shown in Tables 8.2 and 8.3, samples were obtained from the surface to a depth of six inches at most locations. It was presumed that the relative immobility of soil metals would cause the highest concentrations to remain bound in the top layers of the soil. However, samples were also obtained from deeper strata at randomly selected locations to determine the extent of movement of the metals down the soil profile. The average concentrations for surface and subsurface samples were separately computed and are summarized in Table 8.4. From these data, ratios of surface to entire profile and subsurface to overall mean concentrations were calculated and depicted in Table 8.4. The data suggest that the primary zone of metals accumulation in the soil is in the upper six inches of the profile. These computations, however, reveal that during the period of irrigation (often as long as 50 years), toxic metals in affected soils have migrated downward into the underlying layers at least to the same relative extent as occurs naturally in the control areas. Copper and zinc tend to have moved downward to a greater extent in affected areas than in reference areas. This is explained by the slightly increased acidity of some contaminated soils, and intense Irrigation making these metals more mobile than under natural, more neutral conditions. It is believed from data presented here that contamination of subsurface soils by toxic metals extends below the 36-inch maximum depth surveyed in this study, and affects the entire soil profile and root zone. ENVIRONMENTAL AND PUBLIC HEALTH EFFECTS Increased acidity and accumulation and distribution of heavy metals in the soil profile have contaminated agricultural and native 8-36 TABLE 8.4 VERTICAL DISTRIBUTION OF MEAN TOTAL AND PLANT-AVAILABLE METAL CONCENTRATIONS IN THE SOIL PROFILE ARKANSAS RIVER VALLEY ' Total Concentration (mg/kg) Arsenic_ Cadmium Copper Lead Zinc Control: surface 32 1.7 21 37 79 subsurface 21 0.8 7 9 33 entire profile 29 1.5 17 29 66 Below California Gulch: surface 75 19 145 1,700 3,007 subsurface 57 8 135 505 1,447 entire profile 70 16.3 144 1,403 2,569 Stratum to Entire Profile Ratio for Total Concentrations Control: surface 110 113 124 128 120 subsurface 72 53 41 31 50 Below California Gulch: surface 107 117 101 121 117 subsurface 81 49 94 36 56 AB-DTPA (Plant-Available) Concentration (mg/kg) Control: surface 1.3 0.5 4 13 6 subsurface 1.4 0.1 2 2 1 entire profile 1.4 0.4 4 10 5 Below California Gulch: surface 1.4 12.6 18 90 276 subsurface 1.4 2.6 21 17 214 entire profile 1.4 9.8 19 69 259 Stratum to Entire Profile .Ratio for Plant-Available (AB-DTPA) Concentrations Control: surface 93 125 100 130 120 subsurface 100 25 50 20 20 Below California Gulch: surface 100 129 95 130 107 subsurface 100 27 111 25 83 Data collected by ES in June and August, 1985. 21 The ratios were computed by dividing the average concentration of each metal at each layer by the overall mean and multiplying the result by 100. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION soils from just above the confluence of California Gulch and the Arkansas River south to Kobe (the Hayden Ranch) and possibly further downstream. Areas immediately above the confluence containing high soils metals levels have been irrigated in the past with California Gulch water. Some areas were irrigated with Arkansas River water originating from the East Fork of the Arkansas River, below the Lead- ville Drainage Tunnel. This soil contamination has indirect, though important, environmental and public health implications. The plants grown on contaminated soils have absorbed and accumulated trace metals often to phytotoxic levels. Animals grazing on contaminated plants have developed symptoms of metals toxicity. Metals toxicity symptoms in livestock is evident at the Smith Ranch, and is discussed in more detail in Chapter 9. Along the food chain, plants, animals, and possibly humans are threatened to varying degrees by toxic metals contamination of the soils in the study area. Livestock is particularly at risk because of habitat restrictions. Elevated metals concentrations in soil affect the growth and survivability of vegetation, and threaten water quality through increased soil erosion and sedimentation.

8-38 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION CHAPTER 9 VEGETATION INVESTIGATION The vegetation resources of irrigated pastures and haylands and wetlands along the Arkansas River were investigated by Engineering- Science. Elevated concentrations of cadmium, copper, lead, molybdenum, nickel, and zinc were found in plant tissues sampled in contaminated areas. The adverse effects of these metals on plants is expressed as reduced plant cover and forage production in contaminated versus reference areas. Many of the plant tissue concentrations of metals were within or above the range considered toxic to livestock under chronic exposures. Symptoms of metals toxiclty reported in livestock in recent years Included scours (diarrhea), stiff joints, depression, low weight gain, and death. These symptoms are characteristic of chronic poisoning by cadmium, lead, molybdenum, and zinc. RESOURCES AND USE The Yak Tunnel/California Gulch study area supports a variety of plant communities, including subalpine and upper montane forests on the mountain slopes and grasslands, shrublands, and wetlands in the valley bottoms. Agricultural land uses occur in the Arkansas River valley. Pastures and haylands occur on approximately 4,100 acres in the study area. Cattle, sheep, and horses graze over much of the study area. Leadville is located in a region where elk and deer hunting are important recreational activities. Hunter success and ratio of bull elk harvested by hunters is relatively high or above average for Colorado. The elk population In the area is gradually increasing.

9-1 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION The area is also very popular for deer hunting. The deer population in this area is gradually increasing, although it is of average size on a statewide basis. Hunter success and the ratio of buck deer harvested by hunters is about average for Colorado. NATURE AND EXTENT OF CONTAMINATION Many factors affect the ability of plants to absorb metals, including, but not limited to, physical and chemical characteristics of the soils; concentration, mobility, ionic form, and availability of metals in the soils; soil and air temperature; season; plant species; and plant vigor. Plants absorb available metals primarily through the roots, although some absorption may occur through the leaves when they have been coated with contaminated dust (Haghiri, 1973). Plant species vary widely in their ability to absorb and accumulate metals. Some species can tolerate and concentrate relatively high levels of metals and are termed accumulator species. For instance, willow (Salix spp.) is an accumulator of zinc (Nriagu, 1980), a fact supported by the study area plant tissue analysis. Metals generally accumulate in different plant tissues at different rates. The highest concentrations are usually found in the roots, with lesser concentrations in the leaves and steins (Haghiri, 1973; Cannon, 1976; Miles and Parker, 1979; Nriagu, 1980; Demayo et al., 1982b; King et al., 1984). This is particularly true for arsenic, lead, and nickel (U.S. Fish and Wildlife Service, 1978). Cadmium, copper, and zinc are more readily translocated to the stems and leaves. Therefore, the toxic effects of metals result in varied responses in different plant tissues. Phytotoxic concentrations reported in the literature are generally defined as concentrations of metals which resulted in a 25 percent reduction in yield in a variety of plant species (Haghiri, 1973; Miles and Parker, 1979; Page et al. , 1981; U.S. Environmental Protection

9-2 YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Agency, 1983). Phytotoxic concentrations which affect plant germination, growth, viability, or photosynthesis are reported as well (Hag- hiri, 1973; Miles and Parker, 1979; Collins, 1981; Koeppe, 1981). Be- cause of the wide range of phytotoxic effects among species reported in the literature, phytotoxic or excessive concentrations referenced in this report are used as guidelines to suggest that metals concentrations of concern occur in particular areas or in particular plant species. Contaminants of Concern Metals concentrations found in study area plant tissues are compared to normal, contaminated, and toxic concentrations reported in the literature in Table 9.1 Based on a literature review and field results, the contaminants of concern are cadmium, copper, lead, molybdenum, nickel, and zinc. These metals are of concern because of their generally high concentrations in plants in the study area, the potential synergistic effects of these metals in plants, and/or their potential toxicity to livestock. Arsenic and boron occurred at concentrations which were not considered toxic to livestock or plants. Cadmium Cadmium is a nonessential element in plants (Fleischer et al., 1974). The normal cadmium concentration in plants is less than 2.3 parts per million (ppm) (Table 9.1). Concentrations greater than 3 ppm dry weight in plant tissues have resulted in toxic responses in some plant species (Allaway, 1968; Bingham et al., 1975). Phytotoxic effects on crop plants occur over the range of 5 to 700 ppm, dry weight (U.S. Environmental Protection Agency, 1983). Cadmium can act synergistically with copper, nickel, and zinc to produce phytotoxic effects (Wallace and Rornney, 1977; Taylor et al., 1982). Cadmium can inhibit iron uptake in plants resulting in iron deficiency (Peterson and Girling, 1981).

9-3 TABLE 9.1 SUMMARY OF METALS CONCENTRATIONS IN PLANT TISSUES Range of Element Arkansas Rlvec Valley.. Range of Normal Range of Contaminated Range of Toxic/ Blologlcal Element Concentration (Detection Limit Sample Concentrations Expected Concentration Concentration Excessive Concentra- Requirements In Plants Toxic to ppm) Reference Contaminated (ppm, mg/kg) (ppra, mg/kg) tlon (ppm, mg/kg) Plants Animals Livestock (ppm, mg/kg Sites Sites Arsenic ND2/ ND-4.3 <1. 0-1.0 (I)3' 0.5-75.5 (22,23) <1. 0-76.0 (2) N4/ N MO (1) , (2.5) ';!' Boron 2.9-26 5.4-27 5-30 (1) >200 (24) >75 (1,25) E E >150 (1) (0.2) Cadmium 0.4-24 1-34 <0.1-2.3 (4,5,6) 0.6-50 (7,21) >3.0 (5,8,9,10) N N >0.5 (i) (0.2) Copper 2.7-8.9 3.9-12 4.0-15.0 (1,4) 1.0-100 (10,11) >20.0 (1,12) E E MO (1,12) (0.15) Lead 35-150 34-980 0.1-20 (3,4,13) 57-485 (6,11,14) MOO (15,16) N N 5-30 (1,13) (1.25) Molybdenum ND-2.9 0,3-10 1-100 (1) >8 (24) >1000 (1) E E >5 (1,4) (0.25) Nickel 2.3-10 1.7-86 0.1-16.0 (1,17,18) 2-902 (18) 28-200 (1,18) E-N E >50 (1) (0.5) Zinc 14-480 190-960 15-150 (1,19,20) 40-3000 (20) 60-500 (1,3) E E 300-1000 (1) (0.2) Parts per million-dry weight ND - Not Detected 3./, References are presented within parenthesis N • Nonessentlal; E - Essential References 1 U.S. EPA, 1983 15 Wllklns, 1957 2 National Academy of Sciences, 1977 16 Koeppe, 1981 3 Colllngs, 1981 17 Conner and Shacklette, 1975 4 Gough et al., 1979 18 Hutchlnson, 1981 5 Allaway, 1968 19 Taylor, et al., 1982 6 Smith, 1973 20 Nrlagu, 1980 7 Flelscher et al., 1974 21 Shacklette, 1972 8 Miles and Parker, 1979 22 Wild, 1974 9 llaghlri, 1973 23 Williams and Whetstone, 1940 10 Blngham et al., 1975 24 Heck et al., 1978 11 Van Loon, 1976 25 Mortvedt et al., 1972 12 Demayo et al., 1982a 13 Demayo et al., 1982b 14 Cannon, 1976 - ,s-- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Soil concentrations of 2.5 ppm total cadmium have resulted in toxic effects in soybean and wheat (Miles and Parker, 1979). Soil concentrations of 10 to 30 ppm cadmium can adversely affect the germination, survival, and yield of native plant species (Miles and Parker, 1979). Fleischer et al. (1974) report the death of a horse which consumed forage containing less than 10 ppm cadmium. The upper level cadmium concentration in livestock forage recommended by the U.S. Environmental Protection Agency (1983) is 0.5 ppm. Mammals lack the ability to excrete cadmium; consequently, absorption occurs throughout life even though body burdens may already be high (Berry and Wallace, 1974). Cadmium adversely affects the res- piratory, cardiovascular, nervous, and reproductive systems. Cadmium contamination of animals through the food chain is well documented (Everett and Anthony, 1976; Munshower, 1977; Sileo and Beyer, 1985). Cadmium can inhibit copper uptake in livestock, resulting in copper deficiency (Gunson et al., 1982). In the Yak Tunnel/California Gulch study area, plant tissue concentrations as high as 34 ppm and total soil cadmium concentrations as high as 48 ppm were found in contaminated irrigated pastures. Many of the plant tissue concentrations of samples from the contaminated areas are within the range considered toxic to plants and livestock. These contaminated areas will be discussed in detail in later sections. Copper Copper is an essential element for plants and animals. Expected copper concentrations in vegetation range from 4 to 15 ppm (U.S. En- vironmental Protection Agency, 1983) (Table 9.1). Plant concentrations greater than 20 ppm are generally considered toxic to plants (Demayo et

9-5 ?. YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION al., 1982a; U.S. Environmental Protection Agency, 1983).. Copper can act synergistically with cadmium and nickel to produce phytotoxic effects at lower concentrations (Wallace and Roraney, 1977). As little as 10 mg/kg of copper in the diet may produce toxic responses in sheep (Demayo and Taylor, 1981) although the U.S. Environ- mental Protection Agency (1983) considers 100 and 250 ppra copper to be the threshold value for cattle and sheep toxicity, respectively. Copper utilization in livestock can vary according to the ratio of other metals in the diet. For example, as little as 1 to 2 ppm of molybdenum can have toxic effects in livestock if copper concentrations are below 8 ppm in plants. High dietary intakes of zinc and cadmium can also inhibit copper utilization in livestock (Gunson et al., 1982). The highest copper concentration found in any plants in the study area was 12 ppm. Copper concentrations of less than 12 ppm, when combined with concentrations of molybdenum greater than 5 ppm, can result in molybdenosis (copper deficiency) in livestock (Demayo et al., 1982a). Because of potential molybdenosis and other copper deficiency diseases in livestock, copper was included as a potential metal of concern in this study even though copper concentrations toxic to plants probably do not occur. Lead Lead is considered nonessential for both plants and animals (Gough et al., 1979; U.S. Environmental Protection Agency, 1983). Normal lead concentrations in plants reported in the literature range from 0.1 to 20 ppm (Table 9.1). Toxic responses occur in some plants at 100 ppm, although usually much higher concentrations are required for phytotoxic effects to appear (Demayo et al., 1982b; U.S. Environmental Protection Agency, 1983). Lead uptake generally increases in plants grown in acid sulfide environments and symptoms of lead toxicity are found only in plants grown on acidic soils (Cannon, 1976; U.S. Environmental Pro- tection Agency, 1983). Concentrations of lead below 1,000 ppm In soil

9-6 YAK TUNNEL/CALIFORNIA GDLCH 02/28/86 REMEDIAL INVESTIGATION have caused phytotoxic effects (Overcash and Pal, 1979; U.S. Environ- mental Protection Agency, 1983). Contaminated soils in the Arkansas River Valley have total lead levels up to 5,800 ppm. Lead has been shown to be toxic to horses at 5 ppm (dry weight) in grass (Demayo et al., 1982b). The U.S. Environmental Protection Agency (1983) lists an upper level of chronic dietary exposure to lead without loss of production of 30 ppm for cattle. Symptoms of lead poisoning in livestock include maniacal excitement, depression, anorexia, colic, diarrhea, blindness, movement in a circle, and pushing against objects. More severe poisoning can cause death (Demayo et al., 1982b). Lead toxicosis has also been documented in a wide variety of wildlife species, including waterfowl (National Academy of Science, 1972; Anderson, 1975; Demayo et al., 1982b; Zwank et al., 1985), rap- tors (Pattee et al., 1981; Benson et al., 1974), and deer (Harrison and Dyer, 1984; Sileo and Beyer, 1985). Documentation exists for the translocation of lead into wildlife from mine tailings (Johnson et al., 1978; Roberts and Johnson, 1978; Smith and Rongstad, 1982) and other sources of lead contamination (Jefferies and French, 1972; Williamson and Evans, 1972; Quarles et al., 1974; Welch and Dick, 1975; Mierau and Favara, 1975; Goldsmith and Scanlon, 1977; Erickson and Lindsey, 1983). These studies indicate that body burdens of lead are directly propor- tional to the prevailing environmental exposure and that contaminated vegetation and soils are the primary pathways of lead translocation. Lead concentrations in plants sampled in the Yak Tunnel/California Gulch study area ranged from 34 to 980 ppm (Table 9.1). All of the plant samples, even those taken in reference areas, contained sufficiently elevated lead levels to warrant concern about the effects on plants, livestock, and wildlife.

9-7 ;i_-. YAK TUNNEL/CALIFORNIA GULCH 02/28/8.6 REMEDIAL INVESTIGATION Molybdenum Molybdenum is an essential plant micronutrient. Molybdenum normally occurs in plants at concentrations of less than 100 ppm (U.S. En- vironmental Protection Agency, 1983). Concentrations greater than 1,000 ppm in plant tissues are excessive or phytotoxic. Livestock toxicity can be caused by 5 ppm molybdenum in plant tissues, especially when copper concentrations are low or normal (8-11 ppm). Under these conditions, molybdenosis (also called teart disease or peat scours) may occur. Molybdenum impairs the utilization of dietary coppper (Gough et al., 1979; Demayo et al., 1982a; Gunson et al., 1982). If copper levels occur much below 8 ppm, then only 1 to 2 ppm of molybdenum can be toxic to cattle (Demayo et al., 1982a). In the contaminated irrigated pastures studied in the Arkansas River Valley, molybdenum concentrations ranged from 0.3 to 10 ppm. Because of the relatively low concentrations of copper found in forage plants, livestock in all of the areas sampled are exposed to conditions that could lead to molybdenosis. Nickel Nickel is a nonessential element to plants which normally occurs at concentrations of less than 16 ppm in plant tissues (Table 9.1). The toxic or excessive range is considered to be 28 to 200 ppm (Hutch- inson, 1981; U.S. Environmental Protection Agency, 1983). A chronic exposure limit for livestock of 50 ppm has been suggested by the U.S. Environmental Protection Agency (1983). In the study area, a range of 1.7 to 86 ppm of nickel was detected in contaminated area vegetation. Tissue concentrations fall within the lower phytotoxic limits identified in the literature and at levels within the range of livestock-toxic concentrations.

9-8 ,.i--- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Zinc Zinc is an essential plant element. The normal range for zinc in vegetation is 15 to 150 ppm, with 60 to 500 ppm being considered phytotoxic or excessive (Table 9.1). Zinc can act synergistically with cadmium to produce phytotoxic effects (Taylor et al., 1982). An excess of zinc can inhibit iron uptake in plants resulting in iron chlorosis (Peterson and Girling, 1981; Taylor et al., 1982). Plant tissue concentrations considered toxic to livestock are 300 to 1,000 ppm (U.S. Environmental Protection Agency, 1983). Signs of zinc toxicosis in foals include lameness and swollen joints (Gunson et al., 1982; Sileo and Beyer, 1985). Zinc can inhibit copper uptake in animals (Gunson et al., 1982; Sileo and Beyer, 1985). One effect of the resulting copper deficiency is weak connective tissue in limb joints (Gunson et al., 1982). Most of the plant samples taken from the study area contained zinc concentrations falling within the range considered toxic to plants or animals (Table 9.1). Geographic Extent of Contamination in Vegetation Description of Vegetation Sampling Areas Vegetation studies were conducted in wetlands and irrigated pastures along Tennessee Creek and the Arkansas River. The locations of sample points are shown in Figure 9.1. The four general areas sampled were selected to determine incremental effects of metals from Califor- nia Gulch and other source waters on agriculture in the Arkansas River Valley. The four areas studied were Clotworthy's ranch and an adjacent wetland along Tennessee Creek, Seppi's ranch, Smith's ranch, and the Hayden ranch. The Tennessee Creek sample areas (points TCV-1 and TCV-2) served as reference areas. Seppi's ranch (sample points ARV-1 and ARV-2), located downstream of the East Fork of the Arkansas River and downstream of the Leadville Drainage Tunnel, but above California Gulch, was also considered a reference area even though concentrations

9-9 FIGURE 9.1 LOCATION OF VEGETATION SAMPLE POINTS

DENVER AND RIO GRANGE WESTERN

«-tEADVILLE DRAINAGE TUNNEL Sulell \ x t Stray" - Horst Gulch

California Gulch California Gulch U.S. HWY 24

LEGEND • VEGETATION REFERENCE AREA SAMPLE LOCATION • VEGETATION CONTAMINATED AREA NORTH SAMPLE LOCATION 0 I/2 1 Mile -"• YAK TUNNEL/CALIFORNIA GOLCH 02/28/86 REMEDIAL INVESTIGATION of metals in plant tissues are higher than those found in the Tennessee Creek valley. Smith's ranch (sample points ARV-3, ARV-4, ARV-5 and ARV-6), located downstream of the California Gulch and Arkansas River confluence, was considered a contaminated area, as was the Hayden ranch (sample points ARV-7 and ARV-8), located about 5 miles downstream of the California Gulch confluence and about 1 mile north of Kobe. The Clotworthy ranch is irrigated with Tennessee Creek water. Mr. Clotworthy raises 1,000 cattle on property he owns or manages, including this ranch and the Hayden ranch. Many cattle were grazing the areas sampled for this study in August, 1985. He has noted poorer weight gain in cattle grazing in pastures on the Hayden ranch, which were irrigated with Arkansas River water (Clotworthy, 1985). Seppi's ranch, irrigated with Arkansas River water (diverted upstream of California Gulch), supports 47 cattle and 2 horses on 185 acres. Only horses were grazing in the pasture sampled for this study in August, 1985. Seppi gave up a 3.64 cfs water right to California Gulch in 1978, because the water was "heavily polluted" and would "kill the vegetation" (Seppi, 1985). She now irrigates only 50 acres of land. Environmental effects caused by the use of California Gulch water noted by Mrs. Seppi include barren land, lower hay yields, illness and death in colts, and poor weight gain and death in calves. These effects and symptoms are consistent with effects caused by metals contamination (U.S. Environmental Protection Agency, 1983; Fleischer et al., 1974; Demayo and Taylor, 1981; Demayo et al., 1982; Gunson et al., 1982). An increase in weight gain occurred when calves were given shots of copper (Seppi, 1985). Smith's ranch was irrigated with Arkansas River water from 1881 to 1983. During this period, water was diverted through the Young-Smith ditch. Dr. Smith now diverts 4 cfs from Lake Creek because of pollution in the Arkansas River (Smith, 1985). Dr. Smith currently raises

9-11 • - - YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION 100 cattle, 15 horses, and 25 sheep on 350 acres of land. No animals were grazing the pasture sampled for this study in August, 1985, although the pasture was later cut for hay. Environmental impacts from Arkansas River irrigation water noted by Dr. Smith, a veterinarian, include barren soil, chlorotic plants, lower hay yield, and lower conception rates, weaning ratios, weight gain, milk production and wool production in livestock. Dr. Smith stated (1985) that he had to remove calves from pastures within 2 weeks after initial irrigation in the spring or they would develop diarrhea and stiffening of joints. Dr. Smith reported (1985) a 52 percent mortality in breeding stock and has noted clinical illness resembling zinc toxicosis in some livestock on his property. Copper deficiency is a major problem in livestock, especially calves. Such symptoms are indicative of cadmium, molybdenum or zinc toxicity, as reported in the literature. Greater livestock weight gain was observed following copper supplements (Smith, 1985). Vegetation Sampling Methods Vegetation sampling conducted for this study in the four general areas included plant tissue sampling at all points and cover and production sampling in the irrigated pastures. At all sample locations shown in Figure 9.1, about 200 grams of above-ground plant tissue for each species were collected within a 50-foot radius of the corresponding soil sample point. The plant species sampled were selected because they commonly occurred in the pastures or wetlands and were important forage or browse for livestock or recreationally important game species. Plant tissue sampling followed all procedures outlined in the quality assurance project plan. The irrigated pastures (sample points TCV-2, ARV-2, ARV-5, and ARV-8) were sampled for cover and plant production. Cover was determined through the use of 3 to 6 50-meter point-intercept transects in each pasture. Cover transects were established in a random orientation

9-12 " •<"- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION from the edge of each of the production and utilization plots described below. Except for sample point ARV-5 on Dr. Smith's ranch, livestock were not excluded from grazing the areas sampled for cover. Plant productivity was estimated at each of the four irrigated pastures by harvesting plants within 3 1-square-meter conical exclosures. All of the current year's growth was clipped from each exclosure, dried, and weighed. The production data from each exclosure in each pasture were averaged to provide an estimate of plant productivity. Three unprotected (not exclosed) 1-square-meter plots were randomly selected in each of two pastures (ARV-2 and ARV-8) for estimation of livestock utilization using the paired plot method (U.S. Bureau of Land Management, 1984). Production data were obtained in a manner identical to that of the exclosures. Results Tennessee Creek Valley and Arkansas River Valley Pastures. A summary of plant cover data is presented in Table 9.2. A general decline in plant cover was noted from the northern reference areas in the Tennessee Creek Valley and Arkansas River Valley above the confluence with California Gulch to the contaminated areas south of the California Gulch confluence (Table 9.2). The two reference areas, TCV-2 (Clotworthy's ranch) and ARV-2 (Seppi's ranch) have identical cover values of 97 percent. Forbs provided more ground cover at ARV-2 than at ARV-1. Both areas were grazed by livestock. Sample point ARV-5 (Smith's ranch) was not grazed by livestock in 1985. Total plant cover in this pasture was 86 percent. Sample ARV-8 located on the Hayden Ranch was in a pasture grazed by livestock. Total plant cover was 78 percent. A portion of the pasture (especially near sample station ARV-7) consisted of barren soil, probably because of metals contamination. Plant-available concentrations of lead and

9-13 TABLE 9.2 SUMMARY OF PLANT COVER DATA FOR IRRIGATED PASTURES

Location/Life Form I/ Mean Plant Cover (percent) TCV-2 (Clotworthy's Ranch) (R) Forbs 8 Perennial Graminoids 2-L Total 97 ARV-2 (Seppi's Ranch) (R) Forbs 31 Annual Graminoids 1 Perennial Graminoids 11 Total 97 ARV-5 (Smith's Ranch) (C) Forbs 5 Perennial Graminoids Total 1816 ARV-8 (Hayden Ranch) (C) Forbs 9 Perennial Graminoids Total £278.

II Data derived from 50-meter transects which were sampled by ES in August, 1985. R= Reference Area C= Contaminated Area -"- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION zinc in the soil at Station ARV-7 (soil station AR-S-25) were the highest of all soils samples taken in irrigated pastures sampled for vegetation. Plant production data, presented in Table 9.3, show a trend toward lower production in the contaminated areas similar to that portrayed by the cover data. Production estimates from protected (enclosed) plots in reference areas were 2 to A times higher than those from contaminated areas. Production estimates from unprotected plots were 2.5 to 5 times higher in reference areas than in contaminated areas. This demonstrates that the forage value of contaminated pastures has been significantly reduced by metals contamination. Approximately 34 percent of the available forage was consumed by livestock at location ARV-2, while 53 percent was consumed at location ARV-8. Hence, livestock are consuming significant amounts of potentially toxic forage. No utilization data were collected at the other sample points. The decline in plant cover and productivity in contaminated areas was paralleled by a general increase in boron, copper, lead, molybdenum, nickel, and zinc in plant tissues (Table 9.4, Figure 9.2, Figure 9.3) and an increase in total and plant-available cadmium, copper, lead, and zinc in soils (Tables 8.2 and 8.3). Figures 9.2 and 9.3 graphically portray maximum and mean concentrations of metals in plant tissues on a logarithmic scale. In these figures the trend of generally increasing metals concentrations in pasture plants from the reference area along Tennessee Creek to the stations above and below California Gulch can be seen. Maximum concentrations of cadmium, copper, lead, molybdenum, nickel, and zinc in samples taken from below the confluence of Calif- ornia Gulch all exceed concentrations potentially toxic to livestock

9-15 TABLE 9.3 PLANT PRODUCTION AND PERCENT UTILIZATION Mean Production.in Mean Production in. Percent Station/Ranch Protected Plots ' Unprotected Plots ' Utilization 3/ 5/m Ibs/acre g/m 2 Ibs/acre REFERENCE AREAS TCV-2 Clotworthy's Ranch 412 3,676 158 4/ 1,414 ARV-2 Seppi's Ranch 482 4,297 320 2,856 34 CONTAMINATED AREAS ARV-5 Smith's Ranch 5/ 189 1,683 ARV-8 Hayden Ranch 134 1,200 63 564 53 II Samples obtained by ES in August, 1985 from 1-m 2 caged plots in pasture. 21 Samples obtained by ES in August, 1985 from grazed 1-m plots in ,, pasture. Calculated from equation presented in U.S. Bureau of Land Management (1984). 4/', Based on one unprotected plot sample. Livestock were not using pasture, therefore no unprotected plots were sampled. TABLE 9.4 SUMMARY OF PLANT TISSUE, COVER, AND PRODUCTION DATA Mean Mean Concentration (ppra) Plant . Plant . Vepetatlon Type Station Species As B Cd Cu Mo Nl Pb Zn Cover (%) f ' Production (Ibs/acre)'' 78 Pasture (R) TCV 2 Deschampsla cespitosa ND 2.9 0.4 2.7 1.8 3.3 b 14 Clotworthy Ranch Phlegm pra tense ND 4.8 0.4 3.4 1.2 2.5 41b 17 Mean ND 3.8 0.4 3.0 1.5 2.9 59.5 15.5 97 3,676 ab Pasture (R) ARV 2 Deschampsla cespltosa ND 4.6 Bb 8.9 2.9 10 .0 1508 210° a Seppl Ranch Phleum pra tense ND 2.9 24.0 6.1 1.0 4.6 120 130 Mean ND 3.8 12.5 7.5 2.0 7.3 135 170 97 4,297 ab ab ab Pasture (C) ARV 4 Deschampsla cespltosa ND 5.4 4.2 8.6 4.2" 23 .0 610ab 430ab Smith Ranch Juncus arctlcus ND tt 16.0 ab 5.4.b 0.7b 3.3 ab. 710ab 280ab Koelerla macrantha 4.3 10.0 34.0 12 .O 10.0 86 .O 980 400 Mean 4.3 10.5 13.1 8• 7 5.0 3/ .4 766.7 370 8b b ab Pasture (C) ARV 5 Deschampsla cespltosa ND 6.2 37J. *K 5.8 1.7 5.0 300a Smith Ranch Juncus arctlcus ND 7.7 2.2?b 6 .6 1.9 2.3 230 ab 19 Oa.b Phleum pra tense ND 6.6 2.4 5.4 2.4 8.9 160 250 Mean ND 6.8 2.8 5.9 2.0 5.4 158 246.7 86 1,683 Pasture (C) Juncus arctlcus ND , *ab „«»> Hayden Ranch ab 8b a Pasture (C) ARV 8 Deachampala cespltosa ND 8.4 3.9 11.0 1.3 8.8 400ab 290 ab Hayden Ranch Juncus arctlcus ND 13.0 3.4 ab 10.0 4.1 53.0 670 490 Mean ND 10.7 3.6 10.5 2.7 30.9 535 390 78 1,200 Wetland (R) TCV 1 Salix montlcola ND 20.0 3.3 ab 5.5 ND 4.7 78" 240" Tennessee Creek

Wetland (R) ARV 1 Salix laslandra var. B u Seppl Ranch caudata ND 26 .0 7.3,a"b 4.2 0.8 3. 6 75" 480"ab jS.. laslandra var. 8b 5 caudata (duplicate) ND 23 .0 9• a'Ib 5.8 0.8 2. 3 b 460ab Salix planlfolta ND 14 .0 8 2 5.7 0.5 2. 7 «35! 440 li planlfolla ab b Bb (duplicate) ND 15 .0 7.9 5 .2 ND 3. 5 71 480 Mean ND 19 .5 8.2 5 .2 0.7 3. 0 56.5 465 ab ab Wetland (C) ARV 3 Salix geyertana ND 14 .0 2 3.9 2.2 8. 5 700b 940ab Smith Ranch Salix montlcola ND 27 .0 3 5.3 0.3 3. 2 65 960 Mean ND 20 .5 2.£9 4.6 1.2 5. 8 382.5 950 Wetland (C) ARV 6 Sallx geyortana ND 19 .0 13 .Oab 5 .2 0.3 5. 0 34b 520ab Smith Ranch R-Reference sampling area. O=Con laminated sampling area. ARV-Arkanaas River Valley vegetation sampling station number. Stations were sampled by ES In August, 1985. TCV=Tennesaee Creek Valley vegetation sampling station number. Stations were sampled by ES In August, 1985. Scientific names from Weber & Johnston (1979) and subsequent revisions. ppm*>parts per million (dry weight basis). ND=Not Detected, concentration below detection limits. 5/ Mean values based on concentrations above detection limits. 6/ Data derived from 50-meter transects In selected Irrigated pastures. 7/ Data from protected plots as presented In Table 9.3. Excessive or phytotoxlc concentration. Concentration which may be toxic to livestock FIGURE 9.2 MAXIMUM CONCENTRATION OF METALS IN IRRIGATED PASTURE VEGETATION OF THE ARKANSAS RIVER VALLEY

^•^B

/ / / L/

/ / aO. / /

9-21 • - YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Station ARV-5 on the Smith ranch was located about 500 meters southeast of ARV-4 in a pasture which had better plant growth than ARV-4. At Station ARV-5, cadmium and lead occurred at concentrations potentially toxic to livestock in all plants sampled. Additionally, zinc occurred at concentrations toxic to livestock in tufted hairgrass (Deschampsia cespitosa), which comprised 24 percent of the plant cover in this pasture. The soil samples obtained at Station ARV-5 (soils station AR-S-21) had the second highest plant-available concentrations of cadmium and lead of all irrigated pasture samples. Two areas were sampled in an irrigated pasture on the Hayden Ranch; Stations ARV-7 and ARV-8. Station ARV-7 was located in an area having only a sparse cover of rush (Juncus arcticus). This nearly barren area was located immediately adjacent to and downslope from an irrigation ditch. According to Clotworthy (1985), manager of the Hayden ranch, contaminated water from the Arkansas River has raised the metals content of the soil to the extent that few plants can grow on it. An analysis of the metals concentrations in soil samples obtained in this area (Soils Station AR-S-25) reveals that the highest plant- available metals concentrations of cadmium, copper, lead, and zinc found in pastures sampled for plant tissues occurred here. Plant- available cadmium concentrations were above U.S. Environmental Protec- tion Agency (1983) guidelines for cadmium levels in soils. Rush samples taken at Station ARV-7 contained cadmium, lead, and zinc at concentrations potentially toxic to livestock. Cadmium and zinc were also present at levels reported as phytotoxic or excessive in plants. Station ARV-8, also on the Hayden ranch, was located in a portion of the pasture having much better plant growth than Station ARV-7. Total plant cover was 78 percent, considerably lower than the other stations sampled for cover (Table 9.2). Cadmium and lead occurred at concentrations potentially toxic to livestock in all of the plants 9-22 "•--"- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION sampled. Copper was potentially toxic to livestock in tufted hairgrass and nickel and zinc were potentially livestock-toxic in rush. Cadmium, lead, nickel, and zinc occurred within the excessive or phytotoxic range (Table 9.4). Metals concentrations in the soils were generally less at Station ARV-8 (Soils Station AR-S-26) than at ARV-7. However, plant-available arsenic concentrations in the soil at ARV-8 were the highest of all irrigated pastures sampled for plant tissue analysis. Arsenic was not detected in plants sampled at Station ARV-8, probably due to the fact that arsenic is not readily translocated to stems and leaves (National Academy of Sciences, 1977 ; U.S. Fish and Wildlife Service, 1978). Tennessee Creek Valley and Arkansas River Valley Wetlands. The wetland plant tissues do not display a trend of Increased metals when reference areas are compared to contaminated areas. As shown in Table 9.4, cadmium and lead occurred at concentrations potentially toxic to livestock in willows (Salix) sampled in both reference and contaminated areas. Zinc occurred at concentrations toxic to livestock in all samples except those obtained along Tennessee Creek (Station TCV-1) at the northern-most reference station. Willow is an accumulator of zinc (Nriagu, 1980), thus accounting for the consistently high concentrations of zinc in all willow samples. Wetlands and riparian areas are used by wildlife to a dispropor- tionately greater extent than other habitat types in Colorado if proper structural characteristics are present (Hoover and Wills, 1984). A diverse assemblage of plant species and plant life-forms is desirable for overall wildlife value. Livestock also use wetlands for forage, thermal cover, and as a source of water. The contaminated wetland sample area ARV-3, located on the Smith ranch, had very sparse undergrowth. Willows were also sparse in the

9-23 - vi,- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION area. The willows sampled had the highest concentrations of boron and zinc of all plant samples (Table 9.4). Cadmium, lead, and zinc occurred at concentrations potentially toxic to livestock at Station ARV-3. The value of wetlands studied south of the California Gulch confluence has been significantly reduced. The sparse undergrowth provides little forage for livestock and wildlife. Little thermal cover is available because of the sparse willow stands. Willow tissues sampled contained concentrations of metals toxic to animals. Although other plant species were not sampled in the wetlands, results of willow tissue analysis and soil samples obtained in these areas suggest concentrations of metals toxic to livestock and wildlife probably occur in all wetland plants growing in the study area along the Arkansas River south of the California Gulch confluence. Thus, livestock and wildlife are not only ingesting toxic concentrations of metals in the contaminated irrigated pastures, but also in the adjacent wetlands and riparian areas. California Gulch and Stray Horse Gulch. Because agricultural land uses do not occur in California Gulch and Stray Horse Gulch, no vegetation sampling was conducted in these areas. However, soils samples were taken and the results indicate that plants are probably accumulating metals at potentially phytotoxic and livestock-toxic concentrations. ENVIRONMENTAL AND PUBLIC HEALTH EFFECTS The evidence of heavy metals contamination and adverse effects in plants in the Arkansas River Valley is expressed as reduced plant cover and forage production in contaminated areas versus reference areas and elevated metals concentrations in plants from the contaminated areas. The plant cover data showed a 19 percent decline from reference areas

9-24 ,s--- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION to contaminated areas. Plant production data showed a reduction of 60 to 70 percent between protected plots in reference areas and protected plots in contaminated areas. Metals concentrations in plant tissues generally increased south- ward through the Arkansas River Valley because of contamination from California Gulch. Metals have entered the pasture soils and vegetation through contaminated irrigation water. Barren soil or sparse vegetation cover was evident near the confluence of California Gulch and the Arkansas River, at several places along the Arkansas River on the Smith Ranch, and along an irrigation ditch carrying Arkansas River water on the Hayden Ranch. These areas contained elevated levels of metals in the soil and plants as compared to reference areas. In many cases, the plant tissues contained concentrations of metals within the ranges reported in the literature to be excessive or phytotoxic in plants. Equally import- antly, many of the plant tissue concentrations were within or above the range considered toxic to livestock under chronic exposures. The effects of toxic metals concentrations in pasture vegetation is manifested in livestock symptomology noted by local ranchers, including Dr. Bernard Smith, a Leadvilie veterinarian. Dr. Smith has noted toxic symptoms in area livestock since the 1940*s (Smith, 1985). Symptoms reported in livestock in recent years included scours (diarrhea), stiff joints, depression, low weight gain, and death (Clot- worthy, 1985; Seppi, 1985; Smith, 1985). These symptoms are characteristic of chronic poisoning by cadmium, lead, molybdenum, and zinc. A primary effect of metals toxicity on livestock is copper deficiency. Cadmium, molybdenum, and zinc inhibit dietary utilization of copper in livestock. Copper shots given to sick livestock often relieved at least some of the symptoms (Seppi, 1985; Smith, 1985), thus confirming the diagnosis of copper deficiency.

9-25 >- YAK TUNNEL/CALIFORNIA GULCH 02/28/86 REMEDIAL INVESTIGATION Contaminated soils and vegetation have been noted in the Arkansas River Valley. Metals concentrations increase downstream of the Cali- fornia Gulch confluence. Livestock have developed symptoms of metals toxicity in contaminated pastures. The public health implications of consumption of these livestock are unknown at this time.

9-26 ..;.-, YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION CHAPTER 10 AIR QUALITY INVESTIGATION The tailings ponds, waste piles and contaminated soils resulting from mining in the Leadville mining district are a source of air pollution because they lack vegetation and are thus subject to wind erosion. The fine grained particles are transported through the air in the form of dust which can create serious health problems and increases the areal extent of contamination. Since the tailings ponds generally consist of finer grained material, which are very susceptible to blowing, the study centers on airborne contamination from the tailings ponds. SITE DESCRIPTION Three tailings ponds were established in California Gulch for disposal of ore processing wastes. The location of the ponds are shown in Figure 4.1. Pond 3 is located approximately 300 yards from the town of Leadville. Ponds 1 and 2 are within approximately 1 mile of the town. A fourth pond is located in Oregon Gulch. The tailings pond surfaces are unvegetated and consist of particles the size of coarse sand and smaller. Some areas of the tailings surface, such as near standing water, exhibit a very fine particle structure of silty clay. The surfaces also show evidence of wind erosion, sorting, and deposition of particles. Two types of meteorological conditions are conducive to blowing the tailings: strong synoptic (upper levels) winds, and local flows. The synoptic winds are the prevailing westerlies that exist in this region of the country. Since the Leadville area is located at such a high elevation, the synoptic winds influence the surface winds to a large extent. These synoptic flows are channeled by the valleys and rugged terrain surrounding the Leadville areas. This redirection of

10-1 YAK TUNNEL/CALIFORNIA GULCH 2/28/8d REMEDIAL INVESTIGATION air flow by terrain features would favor the up-and-down valley flows, i.e., mountain/valley flows, that would transport the tailings into Leadville and the surrounding areas. The local flows are caused by the diurnal, i.e., day and night, heating and cooling cycle. This creates up-and-down valley flows that can, especially if coupled with the synoptic flows, create high wind conditions moving the tailings particles to the populated areas of Leadville and Stringtown. The critical effects of this type of flow are: The dispersion and mixing of the lowest air layers and the pollutants they contain are restricted by the valley walls, and Relatively strong winds occur on a diurnal basis, especially in summer. Although strong winds aid in overall ventilation, they are also a key factor in the emissions of fugitive dust since such emissions are closely tied to wind speed. Onsite observations indicate that the California Gulch tailings pond locations are subject to these classic mountain/valley flow patterns. Likely impact areas would include those areas located up and down the gulch from the tailings ponds as well as all areas near to and downwind from the ponds. Because of its proximity to the tailings ponds, portions of Leadville would be within this affected area. In the winter time, the snow cover in Leadville would help to reduce emissions from the tailings ponds. NATURE AND EXTENT OF CONTAMINATION An initial inspection of the tailings sites indicated that they could be significant sources of suspended particulates and may also be sources of toxic air contaminants. A review of previous analyses of 10-2 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION similar tailings material, which had been conducted to establish the potential for economic mineral recovery, indicated a number of components which had potential to become toxic air contaminants. Sources To better identify the composition of the potentially hazardous air contaminants in the tailings, sampling and analysis of surface materials from each of the tailings ponds in California Gulch was conducted. Two composite samples were taken from tailings pond 3 where the proximity to Leadville represented the most significant exposure potential. Tailings ponds 1 and 2 were also sampled, with two com- posites taken from each pond. These composite samples were taken in selected areas to clarify any composition differences related to the variable surface color that was visually apparent. The six composite samples were analyzed for the toxic materials identified in Table 10.1. As can be seen in the table, the tailings contain substantial fractions of lead. Smaller concentrations of silver, copper, arsenic, manganese and cadmium are also present. In addition to these materials, the samples were found to be approximately 20 percent iron, by far the most significant metallic component. Although iron is not considered hazardous under CERCLA, it is useful for typing the materials. Receptors In order to determine if the tailings ponds are a source of air contamination, dust samples from Leadville and a filter from a Colorado Department of Health air monitoring station were analyzed. Correlation between the tailings materials, dust and the filter would indicate a relationship between the source and receptors. Unfortunately, because of recent precipitation, large accumulations of dust were difficult to obtain, especially in circumstances that were suitable for the subsequent metal analysis. However, three useful samples were obtained. The filter from the air monitoring station located on top of the County

10-3 TABLE 10.1 SELECTED TOXIC COMPOSITION OF TAILINGS POND AND DUST SAMPLES (mg/kg) SAMPLE LOCATION COMPONENT CONCENTRATIONS AND NUMBER As Cd Cu Pb Mn Ag Fe Tailings Pond 1 001 740 35 421 11,800 268 57 272,000 002 210 24 420 5,330 1,790 26 82,900 Tailings Pond 2 001 570 21 505 7,160 298 45 251,000 002 830 77 933 10,200 3,080 44 237,000 Tailings Pond 3 001 320 12 122 2,280 467 31 220,000 002 500 14 85 1,350 395 30 197,000 Leadvilie Dust 001 278 21 446 3,680 3,210 5 54,600 002 630 38 811 5,030 6,290 13 118,000 003 140 69 267 5,500 5,270 21 39,500 Filter Paper 1.95 1.1 16.3 96 83.6 0.38 597 .;i.- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Courthouse in Leadville, was a composite of the June, July, and August, 1985 sampling period. The results of these dust analyses are also shown in Table 10.1. Transport Mechanism To ascertain the size of the particulate matter in the tailings, and, therefore, its ability to become airborne, each of the composite samples was analyzed to determine silt and clay content. Investiga- tions by EPA and others have determined that particulate sizes greater than those typical of silt materials play no significant role in ambient particulate loadings due to fugitive dust. Size analyses shown in Table 10.2 indicate that samples from tailings ponds 1 and 2 consisted of an average 9.6 and 11 percent by mass of silt and smaller materials, respectively. This size distribution shows a clear potential for emissions from the tailings. Samples from tailings pond 3 showed a coarser particle make-up, with an average of 3.5 percent of the material falling in the silt or smaller size range. Fugitive dust emissions are associated with dry conditions and relatively high wind speeds. In this area of Colorado, such conditions exist in the spring and summer months after snowmelt and initial drying. The greatest impact would occur when wind speeds exceed about 12 mph, or under generally gusty conditions. Information from local residents indicates substantial visible dust emissions occur from the tailings during the summer months, a time when Leadville has its largest tourist population. Source/Receptor Relationship One method to establish a source/receptor relationship is with the use of air quality models. The choice of a model was limited due to the terrain considerations and the lack of meteorological data suitable for modeling. The valley model was selected since it has the capability to simulate worst case meteorological conditions in the calculation

10-5 TABLE 10.2 PARTICLE SIZE ANALYSIS OF MINE TAILINGS IN CALIFORNIA GULCH Percent of Sample of Sample Name Silt Size and Smaller Tailings Pond 1 001 10.5 002 8.8 Tailings Pond 2 001 7.7 002 14.8 Tailings Pond 3 001 1.3 002 5.8 - ._.;.-. YAK TUNNEL/CALIFORNIA GULCH 2/28/86. REMEDIAL INVESTIGATION of the short term average. Emission factors were selected following guidance from the Colorado Department of Health fugitive particulate emission approaches (Tistinic, personal communication, 1984). Since these emission factors are for conditions under more normal wind conditions, adjustments were made for the high wind conditions. Measurements have shown that particulate loading of the air at operating mines generally is in the neighborhood of 30 to 50 micrograms per cubic meter. However, under high wind conditions these values can reach levels of 300 to 500 micrograms per cubic meter. Based on these observations, the emission values used in the modeling were increased by a factor of ten as a means of simulating high wind emission values. The model was run assuming a down valley or southeast wind direction, resulting in a maximum calculated concentration of 1,322 micrograms per cubic meter over a 24-hour period. The Colorado primary TSP 24-hour standard is 260 micrograms per cubic meter and the secondary TSP 24-hour standard is 150 micrograms per cubic meter. This level of atmospheric dust loading would produce deposits of dust sufficient for sampling. Such deposits of dust were found and sampled. During down valley wind flows in the California Gulch, as modeled above, the high winds would transport dust from the tailings piles and deposit it in the Leadvilla area. Model results were supported by the dust samples and filter papers reviewed to assess a possible relationship between the collected samples and the soil samples from the tailings ponds. The following presents an approach to this question. A comparison between the sources, the Leadville dust and the filter paper, can be made by calculating the proportionate composition for the seven parameters which were analyzed. The average concentrations were added together to get a total. The average concentration for each parameter was then divided by the total, resulting in a ratio which would be used for comparison purposes. The results of these calculations are presented in Table 10.3. Note that the ratios were 10-7 TABLE 10.3 COMPARISON OF DUST CONSTITUENTS (PERCENT OF METALS ANALYZED) Leadville Tailings Tailings Air Monitoring Ponds Pond Leadville Station Filter Component 1 and 2 3 Dust Paper___ Arsenic 0.3 0.2 0.4 0.2 Cadmium Less than 0.1 Less than 0.1 0.1 0.1 Copper 0.3 Less than 0.1 0.6 2.0 Lead 3.9 0.9 5.8 12.1 Manganese 0.6 0.2 6.1 10.5 Silver Less than 0.1 Less than 0.1 Less than 0.1 Less than 0.1 Iron 94.9 98.7 87.0 75.0 Total 100.0 100.0 100.0 99.9 - ?,- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION determined only for the parameters that were analyzed. Other constituents were also present in the samples, but their presence does not affect this discussion. Figure 10.1 is a visual representation of Table 10.3. As shown on the table and figure, the tailings pond materials and the Leadville dust and filter paper have similar characteristics. Arsenic and copper were at moderate levels. Cadmium and silver were all at low levels and lead was proportionately high. Manganese values were between the high lead levels and low cadmium and silver levels in all cases except for the Leadville dust. Analysis of additional samples would provide further statistical support for the analysis. However, it is apparent from the data that a relationship between the source and the receiver does exist. This relationship coupled with the existance of a transport mechanism make it obvious that materials from tailings ponds 1,2, and 3 have become airborne and must be considered air contaminants which have settled as dust and are present in the air in and adjacent to the town of Lead- ville. Long-term Impact Although many fuguitive dust sources tend to diminish with time because of loss of fine particles or stabilization by protective plant life, no such emission reduction can be forecast for the tailings ponds. Because the tailings ponds have fixed particle sizes, they will present a consistent fraction of fine materials for surface erosion. Although some diminution of fine particles in the surface layers can be anticipated with time, the tailings materials do not form a significant crust as a result of precipitation or other meteorological factors. Routine exposure of new erodible materials should be expected.

10-9 FIGURE 10.1 COMPARISON OF DUST CONSTITUENTS FOR SELECTED METALS

<0 LEADVILLE AIR MONITORING UJ STATION FILTER PAPER ttQl N> 2<

OH OH (0 UHl zO Ou.

09 - ._-, YAK TUNNEL/CALIFORNIA GULCH 2/28/86. REMEDIAL INVESTIGATION In addition to this long-term potential for wind blown particle movement, the tailings ponds themselves have remained essentially free of stabilizing vegetation. Only on tailings pond 1 was there any sign of vegetation. This plant life was established in an area of alluvi- ally deposited soil which covered the tailings. There is no indication that vegetation will begin to grow in the tailing themselves for many years to come because of the hostile growing conditions. As a result, emissions from each of the tailings areas can be expected to remain near present levels for some time Into the future. ENVIRONMENTAL AND PUBLIC HEALTH EFFECTS The adverse environmental effects resulting from the distribution of contaminants through the air has been addressed in previous chapters of this report. Aquatic biota and vegetation have both been shown to be adversely affected by metals contamination. High levels of contaminants in the air can affect human populations through inhalation or through direct contact with contaminated dust. The two metals of most concern to human health which occur in the tailings ponds, waste piles and contaminated soils are lead and cadmium. Lead exerts an adverse effect on neuropsychological function at relatively low exposure levels, especially in children. Other adverse effects of low-level lead exposure on human health include renal damage which may be manifest as hypertension and adverse reproductive effects from both male and female exposures. The most sensitive indicator of cadmium exposure is widely accept- ed as renal tubular damage which results in escape of protein into the urine (proteinuria). Chronic exposure to cadmium which results In kidney cortex levels of cadmium of aproximately 200 ppm or greater are associated with such effects. Because both lead and cadmium do accumulate in humans, chronic exposure to low levels of these metals can concentrate these metals in human tissues over time. 10-11 -"- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

The other metal found in the sources which increases human disease risk is arsenic. Inhaled arsenic has been shown to cause lung cancer, and arsenic ingested from drinking water is strongly suspected of causing skin cancer. As with most suspected environmental carcinogens, cumulative exposure to low levels over long periods is sufficient to produce an increase in cancer risk. For this reason, it is not possible to set threshold levels of exposure below which there is no incremental risk to public health.

10-12 ,--- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

CHAPTER 11 GENERAL RESPONSE ACTIONS AND TECHNOLOGIES INTRODUCTION The overall goal of remedial action is to protect public health and welfare and the environment from the release of hazardous substances. Protection should be provided in the most technically sound and cost-effective manner. The remedial investigation/feasibility study (RI/FS) process is the means to gather data on the nature and extent of contamination and evaluate remedial action measures. The National Contingency Plan (NCP) [40 CFR 300.68 (e)], states that response actions should be preliminarily scoped during the RI phase to help assure that data collection meets the needs of the project. This scoping can then serve as a basis for either additional RI studies or the FS phase of the project. This section Identifies the preliminary general response actions and technologies that may be suitable for providing long-term solutions to the identified site problems. The evaluation represents the initial phase of formulating general response actions and technologies. At this stage in the RI/FS process, general response actions and technologies are evaluated using site and waste characteristics and engineering judgement. A more detailed formulation, evaluation, and screening process will be completed during the FS. The response actions and technologies in this RI are preliminary. They were not evaluated with respect to compliance with current regu- lation, with respect to cost or feasibility, or with respect to possible legal access problems. They are subject to change based on findings of an Environmental Assessment (EA) and are to be used primarily as guidelines to the FS.

11-1 - ,.:-- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION SUMMARY OF SITE PROBLEMS Remedial actions were developed based on contaminated media identified at the site. These media include mining waste piles, ground water, surface water, aquatic biota, soils, vegetation, and air. Investigations associated with each contaminated medium were described earlier in this RI in Chapters 4 through 10. All of the media are contaminated with hazardous substances related to mining activities. The primary sources of contaminants are the mining wastes (waste piles and tailings ponds) and surface waters (Yak Tunnel, Starr Drainage Ditch, upper California Gulch and other tributaries). Ground waters are contaminated by waste pile leachate and contaminated surface water; aquatic biota are impacted by contaminated surface water and shallow ground water; soils and vegetation are impacted by contaminated surface water and shallow ground water; and air quality is impacted by fugitive dust from mining waste piles. The interrelationships between the primary contaminant sources and the various environmental receptors occur continuously and ultimately affect the overall ecosystem. GENERAL RESPONSE ACTIONS Chapter 2 of EPA's "Guidance on Feasibility Studies Under CERCLA" (EPA, 1985) presents a variety of general response actions for remedial action at uncontrolled hazardous waste sites. The general response actions were evaluated using Information concerning sources and migration pathways for contaminants at the site, and engineering judgment. This evaluation resulted in the selection of the general response actions presented in Tables 11.1 through 11.4 for the various contaminated media. These response actions are based on current site information. They are subject to revision based on additional data or an EA. The FS will evaluate and address additional response actions, but such an evaluation is beyond the scope of the current phase of the RI/FS process.

11-2 -•.."-- YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

FORMATION OF REMEDIAL TECHNOLOGIES For each general response and action listed, remedial technologies that may be applicable to the site were identified. Chapter 2 of EPA's "Guidance on Feasibility Studies Under CERCLA" (EPA, 1985) was con- sulted during this task. Each technology was evaluated according to compatability with the physical and waste characteristics of the site. Only those technologies that were considered to fit the needs of the site were included. Additional technologies will be investigated during the FS through the initial and detailed screening processes. Lists of remedial technologies and brief summaries of the technical evaluations performed are presented in Tables 11.1 through 11.4. The general response actions and technologies presented here provide an initial evaluation of actions that will be considered in the FS based upon current data interpretation. In addition, these actions allow for an evaluation of the adequacy of existing data to address the following FS issues: . Treatability; . Areal extent and nature of contaminant sources; . Migration pathways; Technical feasibility of technologies; and . Implementability of technologies. During the FS process, alternatives and technologies will be assembled for each contaminated media at the site. These alternatives and technologies will be initially screened according to technical criteria, such as implementability and reliability, and environmental and public health concerns. The results of this screening will identify remedial action alternatives that are applicable to site and waste conditions. Applicable alternatives will undergo detailed screening using technical, public health, cost, environmental, and institutional criteria. Results of the detailed screening will rank the remedial action alternatives.

11-3 YAK TUNNEL/CALIFORNIA GULCH 2/28/S6 REMEDIAL INVESTIGATION TABLE 11.1 (Continued) MINING WASTES SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS Upper California Gulch Containment Runon Controls Ditches, diversions and/or culverts could route surface waters around waste rock piles and reduce sediment loading Into upper California Gulch. Surface Controls Sediment control ponds, revegetatlon, and/or geotextlle fabric may limit erosion, and reduce stream sediment loading. '•,.. Removal/Partial Excavation Complete or partial removal of waste rock could be accomplished with conventional equipment. Treatment Crushing/Reprocessing Depending on geocheralcal properties, waste rock could be crushed and reprocessed to recover metals and sulfur or utilized for landscaping or construction. Waste byproducts from reprocessing would need proper handling and/or disposal. Disposal Onslte Disposal Small waste rock dumps could be consolidated Into an appropriate centralized disposal facility. Offalte Disposal Offsite disposal In an appropriate facility would be technically feasible, however, disposal volumes and transportation requirements could be significant. Partial offslte disposal may be more attractive. Tailings Ponds Containment Runon/Runoff Improved surface water diversion and conveyance structures could Controls reduce tailings erosion Into California Gulch and Oregon Gulch as well as help reduce pile saturation from runon. Rapid conveyance of waters off the piles would reduce leachate volumes and expedite dewaterlng of the piles. Surface Controls Sediment control basins, vegetation and/or geotextlle fabric may limit erosion. Such measures would need to be Incorporated with other containment actions. Stabilization/Capping Grading of piles could limit potential Instability problems and reduce eroslonal rates. Capping could provide further erosion protection and.could reduce rates of percolation/Infiltration. Various grading and cap designs would need to be considered to accommodate site-specific topography. Removal/Partial Excavation Total or partial removal may be performed using conventional equipment. Removal Implementation would need to consider erosion control, access and material volumes. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION TABLE 11.1 (Continued) MINING WASTES SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS Treatment Reprocessing Residual metals and sulfur could be recovered using various techniques Including, but not limited to, conventional roasting, chemical precipitation, , flotation, or conventional railing techniques. Waste byproducts would need proper handling and/or disposal. ' Neutralization Tailings could be lime neutralized to reduce metals solubility. '' Disposal Onslte Disposal The tailings ponds could be consolidated Into an appropriate centralized disposal facility. Offalte Disposal Offalte disposal In an appropriate facility would be technically feasible, however, disposal volumes and transportation requirements could be significant. Partial offslte disposal may be more attractive. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION TABLE 11.2 GROUND WATER REMEDIAL TECHNOLOGIES FOR SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS All Contaminated No Action None Consideration required by National Contingency Plan. ground water In the area Access Restriction Seal Wells Wells could be sealed or plugged to prevent collection and use of ; contaminated ground water. ,i' Containment Isolation Isolation techniques such as slurry walls, grout curtains or hydraulic barriers could be applied near or around contaminant sources to Impede the migration of contaminants Into California Gulch alluvium. Pumping Wells and Collection Pumping of contaminated ground water via single wells, well fields, or Galleries collection galleries could be performed as part of an aquifer restoration program. Collected waters could be treated or disposed. Treatment Physical Treatment Physical treatment techniques available to remove metals from solution .Include, but are not limited to, Ion exchange, reverse osmosis, electrodlalysls and distillation. Several filtration steps would need to preceed each of these processes. Sludges produced during treatment would need to be properly handled and/or disposed. They may also have an economic value. Physical/Chemical PhyBiochemical treatment techniques available Include, but are not limited Treatment to: chemical precipitation followed by filtration, and oxidation followed by filtration. Sludges produced during treatment would need to be properly handled and/or disposed. They may also be of economic value. Disposal Discharge of Treated Treated ground water could be released to a surface water body such as Ground Water to California Gulch or the Arkansas River. An NPDES permit might be required Receiving Stream for discharged effluent. Discharge of Untreated Release of untreated ground water to surface waters may or may not be Ground Water to feasible. The relative quality of both ground and surface waters would need Receiving Stream to be evaluated. An NPDES permit might also be necessary. Relnjection of Treated Relnjection of treated ground water Into the California Gulch alluvium or Ground Water upper Arkansas River alluvium may be viable. Deep well Injection of treated or untreated ground waters may also be viable. Alternative Water Municipal Water System Affected Strlngtown residents could tie into the existing Parkvllle Water Supply District main to replace contaminated wells. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION TABLE 11.3 REMEDIAL TECHNOLOGIES FOR SURFACE HATER SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS All Surface No Action None Consideration required by the National Contingency Plan. Haters In the Study Area Access Restrictions Fence Fences nay restrict public and wildlife access to contaminated drainages. Deed Restrictions Deed restrictions may limit water usage In or near contaminated drainages. Feasibility may depend on western water law doctrine. Yak Tunnel Containment Plug Tunnel Adit Sealing of the tunnel adit may or may not provide a long-term solution because mine drainage may discharge from other nine openings, Including the Leadvllle Tunnel, and/or faults and fractures Intersected by tunnel and mine workings. Mine drainage at these locations may be of similar quality to that of Yak Tunnel discharge. Selective Tunnel Selective 'tunnel plugging using bulkheads may reduce flow and/or contaminants Plugging contributions from mine headings which can be effectively sealed. The •quantity and quality of Yak Tunnel discharge could be Improved as a result. Surge Prevention Surge prevention using partial plugs or "flow restrlctors" within various tunnel headings may be effective In reducing future Impacts from flow surges created by tunnel cave-Ins or high Inflow events. Tunnel Lining Lining of the tunnel with ahoterete or a sealant may help to reduce Inflow Into the tunnel workings and possibly Improve the structural Integrity of the workings against cave-Ins. Backstoplng with Haste Backstoplng the tunnel with waste rock, slag or tailings may help to prevent Material surging of tunnel discharge and, at the same time, consolidate contaminant source material Into an existing point source. Handling of tunnel discharge and waste material leachate could be performed concurrently. Collection Diversion Diversion of surface flow around areas of suspected Infiltration may.aid In limiting recharge Into the mine. Such arena may consist of open shafts or vents, or fractured areas mapped at the surface that may Intersect the tunnel mine workings, either directly or Indirectly. Treatment Physical/Chemical Treatment processes applicable to removing metals from solution Include, but Treatment are not limited to, chemical precipitation, oxidation, filtration, Ion exchange, solvent extraction, electrodlalysls, reverse osmosis, flotation, and distillation. Sludges generated during treatment would need to be properly handled and/or disposed. Sludges may also have an economic value. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION TABLE 11.3 (Continued) REMEDIAL TECHNOLOGIES FOR SURFACE WATER SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS Disposal OnsIte Treated Treated tunnel waters could be released directly Into California Gulch. Discharge However, maintaining an unconlaminated surface flow In the gulch would be possible only If other contaminant sources adjacent or tributary to the gulch we re removed. Offsite Treated Treated water could be piped to the Arkansas River and discharged. Discharge Offslte Untreated Discharge of untreated water to the Arkansas River nay not be technically Discharge viable because It may not result In a reduction of contaminant loading. Starr Ditch/ Collection Diversion Starr Ditch and upper California Gulch waters could be diverted around Upper California California Gulch and routed Into the Arkansas River. This diversion could Gulch eliminate potential Interaction problems of waste piles along California Gulch. However, It would not solve metals loading problems being contributed from sources upstream from the diversion point. Culverts Where the Starr Ditch passes through Leadvllle, the open ditch flow could be piped via culverts so as to reduce the potential for public exposure to this water. Disposal Ons Ite Treated See discussion under Yak Tunnel. Discharge Offslte Treated See discussion under Yak Tunnel. Discharge Offslte Untreated See discussion under Yak Tunnel. Discharge Miscellaneous Collection Drainages/Gulches Diversion See discussion under Starr Ditch/upper California Gulch Culverts Culverts or pipelines could be utilized to convey contaminated waters to Unit the potential for public exposure. Treatment Physical/Chemical With the exception of Oregon Gulch, these drainages may each contribute a Treatment small portion of the flow and contaminants to California Gulch. Treatment processes such as pH adjustment, flocculatlon and settling may be sufficient to pretreat these waters. Oregon Gulch waters may require more elaborate treatment methods such as those described under Yak Tunnel. Disposal OnsIte Treated See discussion under Yak Tunnel. Discharge Offslte Treated See discussion under Yak Tunnel. Discharge Offslte Untreated See discussion under Yak Tunnel. Discharge YAK TUNNEL/CALIFORNIA GUl.CH 2/28/86 REMEDIAL INVESTIGATION TABLE I1.1 (Continued) MINING WASTES SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS Upper California Gulch Containment Runon Controls Ditches, diversions and/or culverts could route surface waters around waste rock piles and reduce sediment loading Into upper California Gulch. Surface Controls Sediment control ponds, revegetatlon, and/or geotextlle fabric may limit erosion, and reduce stream sediment loading. Renoval/Partlal Excava tlon Complete or partial removal of waste rock could be accomplished with conventional equipment. \i Treatment Crushing/Reprocessing Depending on geochemlcal properties, waste rock could be crushed and reprocessed to recover metals and sulfur or utilized for landscaping or construction. Waste byproducts from reprocessing would need proper handling and/or disposal. Disposal Onslte Disposal Small waste rock dumps could be consolidated Into an appropriate centralized disposal facility. Offsite Disposal Offslte disposal In an appropriate facility would be technically feasible, however, disposal volumes and transportation requirements could be significant. Partial offslte disposal may be more attractive. Tailings Ponds Containment Runoc/Runoff Improved surface water diversion and conveyance structures could Controls reduce tailings erosion into California Gulch and Oregon Gulch as well as help reduce pile saturation from runon. Rapid conveyance of waters off the piles would reduce leachate volumes and expedite dewaterIng of the piles. Surface Controls Sediment control basins, vegetation and/or geotextlle fabric may limit erosion. Such measures would need to be Incorporated with other containment actions. Stabilization/Capping Grading of piles could limit potential instability problems and reduce eroslonal rates. Capping could provide further erosion protection and could reduce rates of percolation/infiltration. Various grading and cap designs would need to be considered to accommodate site-specific topography. Removal/Partial Excavation Total or partial removal may be performed using conventional equipment. Removal Implementation would need to consider erosion control,' access and material volumes. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION TABLE 11.1 REMEDIAL TECHNOLOGIES FOR MINING WASTES SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS All mining waste No Action None Consideration required by National Contingency Plan. sites Access Restrictions Fence Fences would limit public and wildlife access to waste rock and tailings ponds. They could also reduce potential for direct exposure and aggrevatlon of slope Instability and erosion. > Stray Horse Gulch Containment Runon/Runoff Controls such as ditches and culverts could route surface water around waste Controls rock piles and tailings, and route waters off the piles more rapidly. Erosion rates, leachate volumes, and sediment loading Into Starr Ditch could be reduced. Surface Controls Sediment control ponds, revegetatlon and/or geotextlle fabric applied at the base and/or over piles could limit erosion and reduce stream sediment loading. Stabilization/Capping Surface stabilization or grading of piles could limit Instability problems and erosion potential. Capping would provide further erosion protection and . reduce percolation/Infiltration rates. Various cap designs would need to be considered to accomodate site-specific topography. Removal/Partial Excavation Total or partial removal could be accomplished using conventional equipment. Removal Implementation would need to consider erosion control, access, and material volumes. Treatment Reprocessing Tailings could be reprocessed to recover residual metals and sulfur. Techniques could Include, but not be United to conventional roasting, conventional milling, chemical precipitation, or floatation. Waste rock would require crushing prior to reprocessing. Depending on geochemlcal properties, crushed waste rock might be suitable for landscaping or and/oconstructionr disposal. . Waste byproducts from reprocessing would need proper handling Neutralization Mill tailings or waste rock could be lime neutralized to reduce metals solubility. Disposal Onslte Disposal Numerous waste rock piles and/or tailings ponds could be consolidated Into an appropriate centralized disposal facility located onsite. Offalte Disposal Offsite disposal In an appropriate facility would be technically feasible. However, disposal volumes and transportation requirements could be significant. Partial offslte disposal may be more attractive. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION TABLE 11.4 REMEDIAL TECHNOLOGIES FOR AQUATIC BIOTA, SOILS AND VEGETATION, AND AIR QUALITY RESOURCE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS Aquatic Biota No Action None Consideration required by National Contingency Flan. Removal Bank Excavation Sections of the stream banks which contain contamination could be excavated and removed using conventional equipment. Proper disposal would be required. Sediment Excavation Excavation and removal of contaminated stream sediment might aid In Restoring the aquatic habitat. Excavated material would require proper disposal. Streambed disturbance Might create substantial sedimentation and turbidity problems downstream, however, these problems would be short-term. Treatment Habitat Restoration Ultimately, restoring water quality in California Gulch to that which is not toxic to fish nay be the most effective remedial action. Treatment techniques were presented earlier under Yak Tunnel. Replacement Restocking Restocking of fish in the upper reaches of the Arkansas River may provide a short-term solution to the problem. This may be required annually until the 'aquatic habitat is restored. Soils and Vegetation No Action None Consideration required by National Contingency Plan. Access Restriction Fence Limit public and wildlife access to denuded pasture lands and other impacted areas. Removal Bank Excavation See discussion under Aquatic Biota. Selective Excavation Selective excavation and removal of contaminated soils could be technically feasible where soils are contaminated. Proper disposal of excavated material would be required. Treatment Neu tralization Neutralization of soils with lime may be effective in correcting acidic soil conditions and limiting metals migration. Topsoll Addition Topsoll addition may be technically feasible in areas where vegetation is severely stressed or non-exlstant. Simple lime addition in these areas may not be sufficient. Mulching Discing of mulch into damaged soils may restore essential mlcroblal activity and replenish nutrients needed to sustain plant growth. Mulch may be added to low-productivity soils either in lieu of, or in conjunction with, lime. TABLE 11.4 (Continuedi ) REMEDIAL A.TECHNOLOGIE, S FOR AQUATIC BIOTA, SOILS AND VEGETATION, AND AIR QUALITY SITE GENERAL RESPONSE ACTION TECHNOLOGY TECHNICAL COMMENTS Disposal Onalte Disposal Onslte disposal of contaminated soils may be accomplished In conjunction with onslte disposal of other mining wastes. The disposal facility may need to be an appropriate landfill or surface Impoundment located onslte. OffBite Disposal Offslte disposal would Involve use of an appropriate offslte facility. Waste volumes and transportation requirements could be substantial. Air Quality No Action None Consideration required by National Contingency Plan. Containment Capping and Waste rock and tailings could be regraded, capped, and/or revegetated to Revegetatlng Piles eliminate the fugitive dust problem. ';" Removal Removal of Piles Waste rock and tailings could be removed during site cleanup to eliminate the fugitive dust problem. General Reloca tlon Resident Relocation It may be feasible to relocate the residents of Leadvllle, Stringtown, and the surrounding areas who are adversely impacted by the California Gulch/Yak Tunnel site. Relocation may be temporary until the site is restored to acceptable conditions, or may be permanent. YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION REFERENCES CITED Allaway, H.W. 1968. Agronomic controls over the environmental cycling of trace elements. ,-^In A.G. Norman (ed.). Advances in Agronomy 20:235-271. . .-,: , Anderson, P. D., and P. A« Spear. 1980. Copper pharmacokinetics in fish gills - Volume II. Body size relationships for accumulation and tolerance. Water Resources 14:1107. Anderson, W.L. 1975. Lead poisoning in waterfowl at Rice Lake. Illinois Journal of Wildlife Management, 39 (2):264-270. . ASARCO, Inc. 1983. Some Facts Concerning the Yak Tunnel. Unpub- lished. Wallace, Idaho. ASARCO, Inc. 1984. Reports on Feasibility, Effects, and Legality of Plugging the Yak Tunnel, Leadville, Colorado. Wallace, Idaho. Aubert, H. and M. Pinta. 1977. Trace elements in soils. Develop. Soil Science 7: 135. Avery, E. L. 1985. Sexual maturity and fecundity of brown trout in central and northern -Wisconsin streams. Technical Bulletin No. 154. .Department of Natural Resources, Madison, Wisconsin. Bagenal, T. 1978. Methods for assessment of fish production in fresh waters. IBP Handbook No. 3. Blackwell Scientific Publications, Oxford. Baxter, J. C., D. Johnson, W. D. Burge, E. Keinholz, and W. N. Cramer. 1983. Effects on Cattle from Exposure to Sewage Sludge: Project Summary. U.S. Environmental Protection Agency, EPA-600/52-83-012. Behre, C. H., Jr. 1953. Geology and Ore Deposits of the West Slope of the Mosquito Range. U.S. Geological Survey Professional Paper 235. Benson, N.R., R. P. Covey, and W. Hagland. 1978. The apple replant problem in Washington State. Journal of the American Society Horticulture Science 103:156-158. Benson, W.W., B. Pharaoh, and P. Miller. 1974. Lead poisoning in a bird of prey. Bulletin of Environmental Contamination and Toxi- cology 11:105-108. Benoit, D. A., E. N. Leonard, G. M. Christensen, and J. T. Fiandt. 1976. Toxic effects of cadmium on three generations of brook trout (Salvecinus fontinalis). Transactions of the "American Fisheries Society 105:550-560.

R-l YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Berry, W. L., _and A. Wallace. 1974. Trace elements in the environment - their role and potential toxicity as related to fossil fuels - a preliminary study. University of California Laboratory of Nuclear Medicine and Radiation Biology. Bingham, F.T., A.L. Page, R.J. Mahler, and T.J. Garje. 1975. Growth and cadmium accumulation of plants grown on a soil treated with a cadmium-enriched sewage sludge. Journal of Environmental Quality 4 (2): 207-211. Blair, E. 1980. Leadville: Colorado's Magic City. Pruett Publishing Company. Boulder, Colorado. Bowen, H.J.M. 1979. Environmental Chemistry of the Elements. Acade- mic Press. London, New York, Toronto. Brady, N.C. 1974. The Nature and Properties of Soil. 8th edition. Macmillan Publishing Co., Inc. New York, New York. Brown, G. 1986. Personal communication. Historian, Leadville, Colorado. Buchauer, M. J. 1973. Contamination of soil and vegetation near a zinc smelter by zinc, cadmium, copper, and lead. EST. 7:131-135. Cannon, H. L. 1976. Lead in vegetation. In T. G. Levering (ed.). Lead in the Environment. U.S. Geological Survey Professional Paper 957. Washington D.C. Carlander, K. D. 1969. Handbook of Freshwater Fishery Biology. Volume I. The Iowa State University Press, Ames, Iowa. Carroll, J. J., S. J. Ellis, and W. S. Oliver. 1979. Influences of hardness constituents on the acute toxicity of cadmium to brook trout. Bulletin of Environmental Contamination and Toxicology 22:575-581. Chakoumakos, C., R. C. Russo, and R. V. Thurston. 1979. The toxicity of copper to cutthroat trout under different conditions of alkalinity, pH, and hardness. Environmental Science and Technology 13:213-219. Chapman, G. A. 1975. Toxicity of copper, cadmium and zinc to Pacific northwest salmonids. U.S. Environmental Protection Agency, Corvallis, Oregon. Chapman, G. A. 1978. Toxicitles of cadmium, copper, and zinc to four juvenile stages of Chinook salmon and steelhead. Transactions of the American Fisheries Society 107:841-847. Chapman, G. A. and D. G. Stevens. 1978. Acutely lethal levels of cadmium, copper, and zinc to adult male coho salmon and steelhead. Transactions of the American Fisheries Society 107:837-840. R-2 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Chapman, H. D. (ed.). 1966. Diagnostic Criteria for Plants and Soils. University of California, Riverside, California. Chupp, N. R. and P. D. Dalke. 196A. Waterfowl mortality in the Coeur D'Alene River Valley, Idaho. Journal of Wildlife Management 28(4):692-702. Clotworthy, M. 1985. Personal communication. Rancher, Leadville, Colorado. Ceilings, J.C. 1981. Zinc. JEn N.W. Lepp (ed.). Effect of Heavy Metal Pollution on Plants. Volume 1. Applied Science Publishers, New Jersey. Colorado Department of Health. 1982. Unpublished NPDES self reporting data for permit number CO-0021164 submitted for 1980 through 1982. Denver, Colorado. Colorado Division of Wildlife. 1986a. An evaluation of the possible impacts of heavy metal pollution on the brown trout population of the upper Arkansas River. Unpublished manuscript. Colorado Division of Wildlife, Denver, Colorado. Colorado Division of Wildlife. 1986b, Unpublished data. Denver, Colorado. Colorado Mined Land Reclamation Division. 1986. Unpublished data. Connor, J.J., and H.T. Shacklette. 1975. Background Geochemistry of some Rocks, Soils, Plants, and Vegetables in the Conterminous United States. U.S. Geological Survey Paper 574-F. Crouch, T. M. 1984. Water Resources Appraisal of the Upper Arkansas River Basin from Leadville to Pueblo, Colorado. U.S. Geological Survey Resources Investigation Report 82-4114. Davies, P. H., and W. E. Everhart. 1973. Effects of chemical variations in aquatic environments: lead toxicity to rainbow trout and testing application factor concept. EPA-R3-73-011C. National Technical Information Service, Springfield, Virginia. Davies, P. H. 1976a. The need to establish heavy metal standards on the basis of dissolved metals. In R. Andrew, P. V. Hodson, and D. E. Konasewich (eds.). Toxicity to Biota of Metal Forms in Natural Water. International Joint Commission, Great Lakes Res. Advisory Board. Windsor, Ontario. Davies, P. H. 1976a. Use of dialysis tubing in defining the toxic fraction of heavy metals in natural waters. In R. W. Andrew, P. V. Hodson, and D. E. Konasewich (eds.). Toxicity to Biota of Metal Forms in Natural Water. International Joint Commission, Windsor, Ontario.

R-3 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Davies, P. H. J. P. Goettl, J. R. Sinley, and N. F. Smith. 1976. Acute and chronic toxlcity of lead to rainbow trout (Salmo gardneri) in hard and soft water. Water Resources 10:199-206. Davies, P. H., and: J. P. Goettl,- Jr. 1977. -Aquatic life — water quality recommendations for heavy metals and other inorganic toxicants in freshwater. Water pollution studies. Federal Aid Project F-33-R-12. Colorado Division of Wildlife, Ft. Collins, Colorado. Davies, P. H., and J. D. Woodling. No Date. Importance of laboratory-derived metal toxicity results in predicting instream response of salmonids. Unpublished manuscript. Colorado Division of Wildlife, Denver, Colorado. '•••'• •--.••••-.- Davis, S. N., and R. J. M. DeWiest, 1966. Hydrogeology. John Wiley and Sons, Inc. New York. Demayo, A., M. C. Taylor, and S. W. Reeder. 1979. Guidelines for Surface Water Quality. Volume 1. Inorganic Chemical Substances. Arsenic, Environment Canada, Inland Waters Directorate, Water Quality Branch, Ottawa, Canada. Demayo, A., M. C. Taylor, and S. W. Reeder. 1980. Guidelines for Surface Water Quality. Volume I: Inorganic Chemical Substances. Lead. Environment Canada, Inland Waters Directorate, Water Quality Branch, Ottawa, Canada. Demayo, A., and M. C. Taylor. 1981. Guidelines for Surface Water. Volume I: Inorganic Chemical Substances. Copper. Environment Canada, Inland Waters Directorate, Water Quality Branch, Ottawa, Canada. Demayo, A., M. C. Taylor, and K. W. Taylor. 1982a. Effects of copper on humans, laboratory and farm animals, terrestrial plants, and aquatic life. CRC Critical Reviews in Environmental Control, August 1982:183-255. Demayo, A., M. C. Taylor, K. W. Taylor, and P. V. Hodson. 1982b. Toxic effects of lead and lead compounds on human health, aquatic life, wildlife, plants, and livestock. CRC Critical Reviews in Environmental Control 12 (4): 257-305. Eaton, J. G,, J. W. McKim, and C. W. Holcombe. 1978. Metal toxicity to embryos and larvae of seven freshwater fish species - I. Cadmium. Bulletin of Environmental Contamination and Toxicology :95-103. Ecology and Environment, Inc. 1983. Interpretive Report - Surface and Groundwater Investigation California Gulch, Leadville, Colorado. Prepared for CHjM Hill, Denver, Colorado.

R-4 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Emmons, S. F. 1886. Geology and Mining Industry of Leadville, Colo- rado (with Atlas). U.S. Geological Survey Monograph 12. Emmons, S. F., J. D. Irving, and G. F. Loughlin. 1927. Geology and Ore Deposits of the Leadville Mining District, Colorado. U.S. Geological Survey Professional Paper No. 148. Engineering-Science. -,1985. Yak Tunnel California Gulch, Preliminary Consultant's Report. Prepared for Colorado Department of Law, Attorney General's Office, Denver, Colorado. Environmental Protection Agency. 1985. Guidance on Feasibility Studies under CERCLA. Hazardous Waste Engineering Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio. Erickson, D. W., and J. S. Lindsey. 1983. Lead and cadmium in muskrat and cattail tissues. Journal of Wildlife Management 47 (2):550- 555. Everett, J. J., and R. G. Anthony. 1976. Heavy metal accumulation in muskrats in relation to water quality. Transactions of the Northeastern Section, The Wildlife Society. 33rd Northeast Fish and Wildlife Conferences, Hershey, Pennsylvania. Fell, E. Jr. 1979. .Ores to Metals: The Rocky Mountain Smelting Industry. University of Nebraska Press, Lincoln, Nebraska. Finnell, L. M. 1977. Fryingpan-Arkansas Fish Research Investigations, Final Report. Colorado Department of Natural Resources, Division of Wildlife, Fort Collins, Colorado. Fleischer, M., A. F. Sarofim, D. W. Fassett, P. Hammond, H. T. Shacklette, I. C. T. Nisbet, and S. Epstein. 1974. Environmental impact of cadmium: a review by the panel on hazardous trace substances. Environmental Health Perspectives 7:253-323. Forstner, U., and Wittmaun, G. T. W. 1983. Metal Pollution in the Aquatic Environment. Springer-Verlag, New York, New York. Frank, W. 1981. Aspects of Leadville Area Mine Drainage Affecting the Upper Arkansas River. Unpublished. Leadville, Colorado. Freeze, A. R. and J. A. Cherry. 1979. Groundwater. Prentice-Hall, Inc. Englewood, Cliffs, New Jersey. Carton, R. R. 1972. Biological effects of cooling tower blowdown. American Institute of . Chemical Engineering Symposium Series. 69:284. Geckler, J. R., W. B. Horning, T. M. Neiheisel, Q. H. Pickering, E. L. Robinson, and C. E. Stephen. 1976. Validity of laboratory tests for predicting copper toxicity In streams. EPA-600/3-76-116. U.S. Environmental Protection Agency, Duluth, Minnesota. R-5 !' YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION

Gilgulin, U. "1-9" 85. Personal communication with CH2M Hill. Gillespie, P. A. and R. F. Vaccaro. 1978. A bacterial bioassay for measuring the copper chelating capacity of sea water. Limnology and Oceanography 23:543-548. Goettl, J. P., Jr., J. R. Sinley, and P. H. Davies. 1972. Water pollution studies. Colorado Fish Research Review. No. 7:36-44. Division of Game Fish and Parks, fort Collins, Colorado. Goettl, J. P., Jr., J. R. Sinley, and P. H. Davies. 1974. The toxicity of copper to rainbow trout. Water pollution studies. Federal Aid Project F-33-R-9. Colorado Division of Wildlife. Fort Collins, Colorado. Goettl, J. P., Jr., and P. H. Davies. 1976. Cadmium. Water pollution studies. Federal Aid Project F-33-R-11. Colorado Division of Wildlife. Fort Collins, Colorado. Goettl, J. P., Jr., and P. H. Davies. 1978. Water pollution studies. Job Progress Report. Federal Aid Project F-33-R-13. Colorado Division of Wildlife. Denver, Colorado. Goldsmith, C. D., Jr., and P. F. Scanlon. 1977. Lead levels in small mammals and selected invertebrates associated with highways of different traffic densities. Bulletin of Environmental Contami- nation and Toxicology 17 (3):311-316. Gough, L. P., H. T. Shacklette, and A. A. Case. 1979. Element concentrations toxic to plants, animals, and man. U.S. Geological Survey Bulletin 1466. Griffin, R. A. et al. 1977. Attenuation of pollutants in municipal landfill leachate by clay minerals. II. Heavy-metal adsorption. Illinois State Gelogical Survey Environmental Geology Notes No. 79. Urbana, Illinois. Griswold, D., and J. Griswold. 1965-1969. Leadville: A City of Contrast. A series of articles in The Harold Democrat, Leadville, Colorado. Gunson, D.E., D.F. Kowakzyk, C.R. Snoop, and C.F. Ramberg, Jr. 1982. Environmental zinc and cadmium pollution associated with generalized osteochondrosis, osteoporosis, and rephrocalcinosis in horses. JAVMA 180(3):295-299. Haghiri, F. 1973. Cadmium uptake by plants. Journal of Environmental Quality 2 (l):93-95. Hamburg, G. 1985. Personal communication. Hydrologist, State Engin- eers Office, Denver, Colorado.

R-6 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Harrison, P. D., and M. I. Dyer. Lead in mule deer forage in Rocky Mountain National Park, Colorado. Journal of Wildlife Management. 48(2):510-517. Heck, W. W., S. V. Krupa, and S. N. Linzon. 1978. Methodology for the assessment of air pollution effects on vegetation. Air Pollution Control Association Conference, April 19-21. Minneapolis, Minne- sota. Hem, John D. 1970. Study and interpretation of the chemical characteristics of natural water. U.S. Geological Survey Water-Supply Paper 1473. Herald Democrat, The. Various Articles. Hoffman, G.R. and R.R. Alexander. 1983. Forest vegetation of the White River National Forest in western Colorado: a habitat type classification. U.S. Forest Service Research Paper RM-249. Rocky Mountain Forest and Range Experiment Station, Fort Colllns, Colorado. Holcombe, G. W., D. A. Benoit, E. N. Leonard, and J. M. McKim. 1976. Long term effects of lead exposure on three generations of brook trout (Salvilinys fontinalis). Journal of the Fisheries Research Board. Canada 33:1731-1741. Holcombe, G. W., and R. W. Andrew. 1978. The acute toxicity of zinc to rainbow and brook trout: Comparisons in hard and soft water EPA-600/3-78-094. U.S. Environmental Protection Agency, Duluth, Minnesota. Hoover, R. L., and D. L. Wills (eds.). 1984. Managing Forested Lands for Wildlife. Colorado Division of Wildlife in cooperation with the U.S. Forest Service, Denver, Colorado. Howarth, R. S., and J. B. Sprague. 1978. Copper lethality to rainbow trout in waters of various hardness and pH. Water Resources 12:455-462. HRS Water Consultants, Inc. 1984. Hydrogeologic Evaluation of the Yak Tunnel and California Gulch. Lakewood, Colorado. Hutchinson, T. C. 1981. Nickel. In N. W. Lepp (ed.). Effect of Heavy Metal Pollution on Plants. Volume 1. Applied Science Publishers, New Jersey. Ingham, G. T. 1881. Digging Gold among the Rockies, Cottage Library Publishing House, Philadelphia, Pennsylvania. Jacobs, L. W., and D. R. Keeney. 1970. Arsenic-phosphorus inter- actions of corn. Communications In Soil Science Plant Analysis 1:85-93.

R-7 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Jefferies, D._J. and M. C. French. 1972. Lead concentrations in small mammals trapped on roadside verges and field sites. Environmental Pollution 3:147-156. Johnson, M. S., R. D. Roberts, M. Hutton, and M. J. Inskip. 1978. Distribution of lead, zinc, and cadmium in small .mammals from polluted environments. Oikos 30 (1):153-159. Kilgore, D. 1986. Personal communication. Bureau of Reclamation. King, H. D., G. C. Curtin, and H. T. Shacklette. 1984. Metal uptake by young conifer trees. U.S. Geological Survey Bulletin 1617, Washington, D.C. Kleff, J. M. 1948. Letter to Mrs. Marie P. Crane, American Smelting & Refining Company, Salt Lake City, Utah. Klein, H., V. E. Jensch, and H. J. lager. 1979. Heavy metal uptake by maize plants from soil contaminated with zinc, cadmium, and copper oxide. Angewandte Botanik 53:19-30. Koeppe, D. E. 1981. Lead: Understanding the minimal toxicity of lead in plants. JLix N.W. Lepp (ed.) Effect of Heavy Metal Pollution on Plants. Volume I. Applied Science Publishers, New Jersey. Kovda, V. A., B. N. Zolotareva, and I. T. Skripnichenko. 1979. The biological reaction of plants to heavy metals in the substrate. Dolelady Akademii Nauk SSSR 247 (3):766-768. Kuss, A. 1986. Personal communication. Former Resurrection Mill Foreman, Leadville, Colorado. LaBounty, J. F., J. J. Sartoris, L. D. Klein, E. F. Monk, and H. A. Salman, 1975. Assessment of Heavy Metals Pollution in the Upper Arkansas River of Colorado. U.S. Department of the Interior, Bureau of Reclamation, Denver, Colorado. Lamborn, J. E. and C. S. Peterson. 1985. The substance of the land: Agriculture v. industry in the smelter cases of 1904 and 1906. Utah Historical Quarterly (53)4:308-325. Lindsay, W. L. 1979. Chemical Equilibria in Soils. John WIley and Sons, New York. (Luke, J. 1978. A brief history of the Yak Tunnel. Mountain Diggings *- 8(1):20. LCCCA, Leadville, Colorado. Marr, J. W. 1967. Ecosystems of the East Slope of the Front Range in Colorado. University of Colorado Studies, Series in Biology No. 8. University of Colorado Press, Boulder, Colorado. Martinez, E. 1986. Personal communication. City of Colorado Springs, Water Division, Colorado Springs, Colorado. R-8 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION McKim, J., and_ D. A. Benoit. 1971. Effects of long-term exposures of copper on survival growth, and reproduction of brook trout Salvlinus fontinalis. Journal of the Fisheries Research Board of Canada 25:655-662. McKim, J. M., J. G. Eaton, and E. G. Holcomb. 1978. Metal toxicity to embryos and larvae of eight species of freshwater fish. II. Copper. Bulletin of Environmental Contamination and Toxicology 19:608-616. McKee, S. E., and H. W. Wolf. 1963. Water Quality Criteria. Calif- ornia State Water Resources Control Board Publication 3-A, Sacra- mento, California. McLaughlin Engineers. 1981. Colorado Inactive Mine Drainage Water Quality and Impact Abatement. Preliminary Engineering Report. Prepared for the Divison of Mined Land Reclamation, Colorado Department of Natural Resources, Denver, Colorado. Merritt, R.W., and K.W. Cummins. 1984. An Introduction to the Aquatic Insects of North America. Kendall Hunt Publishing Co., Dubuque, Iowa. Mierau, G.W., and B.E. Favara. 1975. Lead poisoning in roadside populations of deer mice. Environmental Pollution 8:55-64. Miles, L. J., and G. R. Parker. 1979. The effect of soil-added cadmium on several plant species. Journal of Environmental Quality 8 (2):229-232. Mitchell, G. A., F. T. Bingham, and A. L. Page. 1978. Yield and metal composition of lettuce and wheat grown on soils amended with sewage sludge enriched with cadmium, copper, nickel and zinc. Journal of Environmental Quality 7 (2): 165-171. Holler, P., and B. Smith. 1985. Personal communication. Lake County Environmental Task Force members. Leadville, Colorado. Moran, R. E. and D. A. Wentz. 1974. Effects of metal-mine drainage on water quality in selected areas of Colorado, 1972-73. Colorado Water Resources Circular No. 25. Prepared by the U.S. Geological Survey in Cooperation with the Colorado Water Pollution Control Commission, Denver, Colorado. Mortvedt, J. J., P. M. Giordano, and W. L. Lindsay. 1972. Micronu- trients in Agriculture. Soil Science Society of America, Inc. Madison, Wisconsin. Munshower, F. F. 1977. Cadmium accumulation in plants and animals of polluted and nonpolluted grasslands. Journal of Environmental Quality 6 (4):411-413.

R-9 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION National Academy.---of Sciences. 1972. Biologic Effects-of Atmospheric Pollutants. Lead. Airborne Lead in Perspective. Committee on Biological Effects of Atmosphere Pollutants, Division Medical Science, Washington, D.C. National Academy of Sciences. 1977. Arsenic. Medical and Biologic Effects of Environmental Pollutants. Division of Medical Sciences, Washington, D.C. Nehring, R. B., and J. P. Goettl, Jr. 1974. Acute toxicity of a zinc-polluted stream to four species of salmonids. Bulletin of Environmental Contamination and Toxicology 12:464-469. Nehring, R. B., and R. M. Anderson. 1984. Special regulations evaluations. Stream Fisheries Investigations. Job Progress Report. Federal aid Project F-51-R-9. Nordstrom, D. K., E. A. Jenne, and J. W. Ball. 1984. Redox equilibria of iron in acid mine waters. In E.A. Jenne (ed.). Chemical Modeling in Aqueous Systems. American Chemical Society Symposium Series, No. 93. Nriagu, J. 0. (ed.). 1980b. Zinc in the Environment. Part 1: Ecolo- gical Cycling. J. Wiley & Sons. New York, New York. Overcash, M. R., and D. Pal. 1979. Design of Land Treatment Systems for Industrial Wastes - Theory and Practice. Ann Arbor Science. Ann Arbor, Michigan. Page, A. L., F. T. Bingham, and A. C. Chang. 1981. Cadmium. .In N. W. Lepp (ed.). Effect of Heavy Metal Pollution on Plants. Volume 1. Applied Science Publishers, New Jersey. Parkville Water District. 1986. Personal communication. Leadville, Colorado. Pattee, 0. H., S. N. Wiemeyer, B. M. Mulhern, L. Sileo, and J. W. Carpenter. 1981. Experimental lead-shot poisoning in bald eagles. Journal of Wildlife Management 45(3):806-810. Perl'man, A. I. 1967. Geochemistry of Epigenesis. Plenum Press, New York, New York. Perhac, R. M., and C. J. Whelan. 1972. A comparison of water, suspended solids, and bottom sediment analysis for geochemical prospecting in a northeast Tennessee zinc district. Journal of Geochemical Exploration 1:47-53. Peterson, P. J., and C. A. Girling. Other trace metals. Jfo N. W. Lepp (ed.). Effect of Heavy Metal Pollution on Plants. Volume 1. Applied Science Publishers, New Jersey. Quality Assurance Project Plan. 1984. California Gulch RI/FS February 22, 1984 CH2M Hill EPA 25.8V29.029.0. . R-10 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Quality Assurance Project Plan for Sample Collection, Processing, and Analysis. 1985. Prepared by Geotrans, Inc., Rocky Mountain Con- sultants, Inc., ERI Logan, Inc., Engineering-Science, Inc., and Rocky Mountain Analytical Laboratory for the State of Colorado Department of Law, Office of the Attorney General. Quarles, H. D., Ill, R. B. Hanawalt, and V. E. Odum. 1974. Lead in small mammals, plants, and soils at varying distances from a highway. Journal of Applied Ecology 11:937-949. Ramsey, R. H. 1973. Men and Mines of Newmont. Octagon Books, New York. Reeder, S. W., A. Demayo, and M. C. Taylor. 1979. Guidelines for Surface Water Quality. Volume I. Inorganic Chemical Substances. Cadmium. Environment Canada, Inland Water Directorate, Water Quality Branch, Ottawa, Canada. Roberts, R. D., and M. S. Johnson. 1978. Dispersal of heavy metals from abandoned mine workings and their transference through terrestrial food chains. Environmental Pollution 16:293-310. Rodriguez, G. 1985. Personal communication with Engineering-Science personnel. Resident, Stringtown, Colorado. Roline, R. A., and J. R. Boehmke. 1981. Heavy Metals Pollution of the Upper Arkansas River, Colorado, and Its Effects on the Distribu- tion of the Aquatic Macrofauna. U.S. Department of the Interior, Bureau of Reclamation, Denver, Colorado. Rose, A. W., H. E. Hawkes, and J. S. Webb. 1979. Geochemistry in Mineral Exploration. Academic Press, New York, New York. Sadar, A. 1986. Personal communication. Former operator of the California Gulch Mill, Leadville, Colorado. Salomons, W., and U. Forstner. 1984. Metals in the Hydrocycle. Springer-Verlag, Berlin. Santillan-Mediano, J. and J. J. Jurinak. 1975. The chemistry of lead and cadmium in soil: solid phase formation. Soil Science Society American Proceedings 39: 851-856. Sartories, J. J., J. F. LaBounty, and H. D. Newkirk. 1977. Histori- cal, Physical, and Chemical Limnology of Twin Lakes, Colorado. U.S. Bureau of Reclamation. Sauter, S., E. S. Buxton, K. J. Macek, and S. R. Petrocelli. 1976. Effects of exposure to heavy metals on selected freshwater fish. Toxicity of commper, cadmium, chromium and lead to eggs and fry of seven fish species. EPA 600/3-76-105. National Technical Infor- mation Service, Springfield, Virginia. R-ll YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Schroeder, H.- ?A_., J. J. Balassa, and W. H. Vinton, Jr. 1965. Chromium, cadmium, and lead in rats: effects on life span, tumors, and tissue levels. Jounral of Nutrition 86:51-66. Schroeder, H. A., and M. Kitchener. 1971. Toxic effects of trace elements on the reporduction of mice and rats. Archives of Environmental Schuhmann, R. 1952. Metallurgical Engineering. Addison Wesley, Reading, Pennsylvania. Seim, W. K., et al. 1984. Growth and survival of developing steelhead trout (Salmo gairdneri) continuously or intermittantly exposed to copper. Canadian Journal of Fisheries and Aquatic Sciences 41:33. Seppi, E. 1985. Personal communication. Rancher, Leadville, Colorado. Seppi, E. 1986. Personal communication. Rancher, Leadville, Colorado. Shacklette, H. T. 1972. Cadmium in Plants. U.S. Geological Survey Bulletin 1314-G, Washington, D.C. Shroyer, D. 1986. Personal communication with CH M Hill. Lake County Land Use Commissioner, Colorado. 2 Sileo, L., and W. N. Beyer. 1985. Heavy metals in white-tailed deer living near a zinc smelter in Pennsylvania. Journal of Wildlife Diseases 21 (3):289-296. Singer, P.C., and W. Stumm. 1970. Acid mine drainage: the rate determining step. Science 167:1121-1123. Sinley, J. R., J. P. Goettl, Jr., and P. H. Davies. 1974. The effects of zinc on rainbow trout (Salmo gairdneri) in hard and soft water. Bulletin of Environmental Contamination and Toxicology 12:193-201. Smith, B. J. 1984. Concerns of the Lake County Environmental Task Force on California Gulch, August, 17, 1984. Leadville, Colorado. Smith, B. J. 1985. Personal communication. Rancher, Leadville, Colorado. Smith, G. J., and 0. J. Rongstad. 1982. Small mammal heavy metal concentrations from mined and control sites. Environmental Pollution (Series A) 28:121-134. Smith, W. H. 1973. Metal contamination of urban woody plants. En- vironmental Science and Technology 7 (7):631-636. Sowers, G. B., and G. F. Sowers. 1970. Introductory Soil Mechanics and Foundations. Macmillan Publishing Company, Inc., New York, New York. R-12 YAK TUNNEL/CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION Spear, P. A. 1977. Copper accumulation kinetics and lethal tolerance in relation to fish size. M.S. Thesis. Concordla University, Mon tera1, Canada. Spehar, R. L. 1976. Cadmium and zinc toxicity to flagfish, Jordanella floridae. Journal of the Fisheries Research Board of Canada 33:1939-1945. Spehar, R. L., and A. R. Carlson. 1984. Derivation of site-specific water quality criteria for cadmium and the St Louis River Basin, Duluth Minnesota. Environmental Toxicology and Chemistry. 3:651. State Demographers Office. 1985. State of Colorado. Stout, C. 1986. Personal communication. Former Resident and ASARCO Mine Superintendant, Leadville, Colorado. Sunda, W. G., and R. R. L. Guillard. 1976. The relationship between cupric ion activity and the toxicity of copper to phytoplankton. Journal of Marine Research 34:511-519. Taylor, M. C., and A. Demayo. 1980. Guidelines for Surface Water Quality. Volume I. Inorganic Chemical Substances. Zinc. Environment Canada, Inland Water Directorate, Water Quality Branch, Ottawa, Canada. Taylor, M. C., A. Demayo, and K. W. Taylor. 1982. Effects of zinc on humans, laboratory and farm animals, terrestrial plants, and freshwater aquatic life. CRC Critical Reviews in Environmental Control. April 1982:113-181. Tisdale, S. L., and W. L. Nelson. 1966. Soil Fertility and Fertili- zers. Second edition. The Macmillan Company, New York, New York. Turk, J. T. and 0. J. Taylor. 1979. Appraisal of Ground Water in the Vicinity of the Leadville Drainage Tunnel, Lake County, Colorado. U.S. Geological Survey on Open File Report 79-1538. Lakewood, Colorado. Tweto, 0. 1968. Leadville District, Colorado: In Ore Deposits in the United States 1933-1967. Volume 1. American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Tweto, 0. 1974. Geologic Map and Sections of the Holy Cross Quad- rangle, Eagle, Lake, Pitkin, and Summit Counties, Colorado. U.S. Geological Survey, Miscellaneous Investigations Series Map 1-830. Topielec, R., J. Coray, and T. French. Comprehensive Plan 1977 Lake County, CO. Upper Arkansas Area Council of Governments, 1977. URS/The Ken R. White Company. 1974. Pollution Study of the Yak Tunnel Discharge Lake County, Colorado. URS/KRW No. 4067. Prepared for the Lake County Commissioners. Denver, Colorado. R-13 YAK TUNNEL/CALIFORNIA GOLCH 2/28/86 REMEDIAL INVESTIGATION U.S. Army Corps of Engineers, Omaha District, California Gulch Tailings Dams. 1983. Prepared for the EPA-Phase I Inspection Reports, Project C9672, Disk 387C. U.S. Bureau of Land Management. 1980. Draft Environmental Impact Statement for Royal Gorge EIS Area, Colorado. Proposed Domestic Livestock Grazing Program. U.S. Bureau of Land Management, Colorado State Office, Denver, Colorado. U.S. Bureau of Land Management. 1984. Rangeland Monitoring, Utiliza- tion Studies. U.S. Bureau of Land Management Denver, Colorado. U.S. Bureau of Mines. 1949. Effect of water upon the Leadville district. JLn Report of Investigations 4493: The Leadville Drainage Tunnel. U.S. Bureau of Reclamation. 1979. Special Report, Study of Effects on Plugging the Leadville Drainage Tunnel. U.S. Department of the Interior. 1979. Study of Effects on Plugging the Leadville Drainage Tunnel. Bureau of Reclamation, Geological Survey, Bureau of Mines. U.S. Environmental Protection Agency. 1980. Ambient Water Quality for Zinc. EPA 440/5-80 079. Washington, D.C. U.S. Environmental Protection Agency. 1983. Hazardous Waste Land Treatment. EPA/SW-874/1983. Cincinnati, Ohio. U.S. Environmental Protection Agency. 1985a. Ambient Water Quality Criteria for Cadmium-1984. EPA 440/5-85-032. Washington, D.C. U.S. Environmental Protection Agency. 1985b. Ambient Water Quality Criteria for Copper-1984. EPA 440/5-84-031. Washington, D.C. U.S. Environmental Protection Agency. 1985c. Ambient Water Quality Critera for Lead-1984. EPA 440/5-84-027. Washington, D.C. U.S. Environmental Protection Agency. 1985d. Guidance on feasibility Studies under CERCLA, Hazardous Waste Engineering Reserach Lab- oratory, Office of Research and Development. Cincinnati, Ohio. U.S. Fish and Wildlife Service. 1978. Impacts of Coal-Fired Power Plants on Fish, Wildlife, and Their Habitats. FWS/OBS-78/29. Ann Arbor, Michigan. U.S. Forest Service. 1979. User Guide to Soils. General Technical Report INT-68. Intermountain Forest and Range Experiment Station, Ogden, Utah. U.S. Geological Survey. 1985. WATSTOR Computer Data Base, for data years 1968-1983, R-14 YAK TUNNEL/ CALIFORNIA GULCH 2/28/86 REMEDIAL INVESTIGATION U.S. Soil Conservation Service. 1965. Arkansas River Basin Coopera- tive Study Report. U.S. Soil Conservation Service. 1975. Chaffee-Lake Area, Colorado Soil Survey. U.S. Department of Agriculture, Denver, Colorado. U.S. Soil Conservation Service. 1982. Important Farmland Inventory- Colorado. U.S. Department of Agriculture, Denver, Colorado. U.S. Soil Conservation Service. 1983. Soils of Colorado - Loss Factors and Erodibility, Hydrologic Groupings. U.S. Department of Agriculture, Denver, Colorado. Van Loon, J. 1976. Heavy Metals in Domestic Sewage Treatment Plant Sludge: A Threat to Human Health. University of Toronto, Inst. Environmental Studies Publication EL-4. Wallace, A., and E. M. Rommey. 1977. Synergistic trace metal effects in plants. Communication in Soil Science and Plant Analysis 8(9):699-707. Welch, W. R. , and D. L. Dick. 1975. Lead concentrations in tissues of roadside mice. Environmental Pollution 8:15-21. Wentz, D. A. 1974. Effect of Mine Drainage on the Quality of Streams in Colorado. 1971-72. Colorado Water Resources Circular No. 21. Prepared by the U.S. Geological Survey in Cooperation with the Colorado Water Pollution Control Commission, Denver, Colorado. Wild, H. 1974. Geobotanical prospecting in Rhodesia. 4. The vegetation of arsenical soils, Kirkia 9:265-278. Wilkins, D. A. 1957. A technique for the measurement of lead tolerance in plants. Nature 1980:37-38. Williams, K. T. , and R. R. Whetstone. 1940. Arsenic distribution in soils and its presence in certain plants. U.S. Department of Agriculture Technical Bulletin 732. Washington, D.C. Williamson, P., and P. R. Evans. 1972. Lead: levels in roadside invertebrates and small mammals. Bulletin of Environmental Contamination and Toxicology 8 (5):280-288. Winner, R. W. , T. Keeling, R. Yeager, and M. P. Farrell. 1977. Effect of food type on the acute and chronic toxicity of copper to Daphnia magna. Freshwater Biology 7:343-349. Winner, R. W. , M. W. Boesel, and M. P. Farrell. 1980. Insect community structure as an index of heavy-metal pollution in lotic ecosystems. Canadian Journal of Fisheries and Aquatic Sciences 37:647-655.

R-15