348516 Report ADMINISTRATIVE RECORD
Zinc Slag Pile RemediaAR l P8SV Investigation KEYWORDS ^ at the LeadvilleCaliforni, Colorada Gulco h Site,FILfc tL (Administrative Order on Consent CERCLA-VIII-92-06) Denver prepare& Rid foor Grande Western Railroad Company
prepared by Morrison Knudsen Corporation Environmental Services Division December 11,1992 FINAL REPORT ZINC SLAG PILE REMEDIAL INVESTIGATION AT THE CALIFORNIA GULCH SITE LEADVILLE, COLORADO TABLE OF CONTENTS Executive Summary Section Title Page 1.0 INTRODUCTION 1-1 1.1 Purpose of the Remedial Investigation 1-1 1.2 Report Organization 1-2 2.0 SITE AND DESCRIPTION 2-1 2.1 Site Description 2-1 2.2 Zinc Slag Description 2-4 2.3 Previous Investigations 2-4 3.0 ZINC SLAG PILE INVESTIGATION 3-1 3.1 Historical Research 3-1 3.2 Field Activities 3-1 3.2.1 Reconnaissance 3-2 3.2.2 Surveying 3-2 3.2.3 Sampling 3-3 3.3 Laboratory Activities 3-4 3.3.1 Compositional Analyses 3-5 3.3.2 Leachability Testing 3-7 3.3.3 Physical Testing 3-8 3.4 Air Quality Investigation 3-9 3.4.1 Meteorological Data 3-10 3.4.2 Emission Rate Estimates 3-10 3.5 Relationship With Other Investigation Programs 3-15 3.5.1 ASARCO Meteorologic Monitoring Program 3-15 4.0 CHARACTERISTICS OF THE ZINC SLAG PILE 4-1 4.1 Smelter History and Slag Pile Development Summary 4-1 4.1.1 Brief History of Leadville Smelting 4-1 4.1.2 Western Zinc Smelter and Slag Pile History 4-1 4.2 Field Reconnaissance of the Zinc Slag Pile and Smelter Area 4-2 4.2.1 The Western Zinc Smelter 4-2 4.3 Physical Characteristics 4-2 4.3.1 Particle Size 4-3
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-RI i [Rev 001/13/93] TABLE OF CONTENTS, Continued Section Title Page 4.3.2 Historic and Current Zinc Slag Pile Surface Areas and Volumes 4-4 4.4 Slag Pile Stability 4-5 4.4.1 Analysis of Structural Stability 4-5 4.4.2 Deflation/Emissions Potential 4-6 4.4.3 Effects of Freeze/Thaw Cycling 4-6 4.5 Chemical Characteristics of Zinc Slag Material 4-7 4.5.1 Compositional Analyses 4-8 4.5.2 Leaching Analyses 4-10 4.6 Analytical Data Validation 4-12 4.6.1 CLP Data Validation 4-14 4.6.2 Non-CLP Data Validation 4-15 5.0 INTERPRETATION OF RESULTS 5-1 5.1 Statistics 5-1 5.1.1 Methodology 5-1 5.1.2 Statistical Results 5-2 5.1.3 Cumulative Probability Plots 5-4 5.1.4 Statistical Summary 5-5 5.2 Potential for Water Quality Impacts 5-5 5.2.1 Metals Loading Based on SPLP Results 5-6 5.2.2 Metals Loading Based on Column Leach Results 5-7 5.2.3 Metals Loading Based on Combination of SPLP and Column Leach Results 5-8 5.3 Potential for Soil Impacts 5-9 5.4 Slag Pile Stability 5-9 5.5 Potential for Air Quality Impacts 5-9 5.6 Anthropogenic Distribution 5-10 6.0 SUMMARY AND CONCLUSIONS 6-1 6.1 Summary of Zinc Slag Characteristics 6-1 6.2 Conclusions Regarding the Site Conceptual Model 6-3 7.0 REFERENCES 7-1
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Rnal-RI H [Rev 001/13/93] LIST OF TABLES Table Title 3-1 Zinc Slag Sample Analysis Summary 3-2 Matrix, Analysis, Analytical Methods and Modifications and Sample Size Requirements 3-3 Summary of Selected Colorado High Country Station Annual Precipitation Weighted Average pH Values (NADP, 1990) 4-1 Particle Size Testing Results 4-2 Weight Percents of Zinc Slag Samples That Are Potentially Inspirable and Respirable 4-3 Frequency of Occurrence - TAL Metals 4-4 Zinc Slag Sample Acid Forming Potential 4-5 Column Leach Test Results 5-1 Concentration Ranges of Populations for Analyses of Slag Determined from Cumulative Probability Plots 5-2 Major Constituents (mg/kg) in Slag and Subsoils with Values Assigned to Concentration Range Populations 5-3 Trace Metals (mg/kg) in Slag and Subsoils with Values Assigned to Concentration Range Populations 5-4 Miscellaneous Measurements (mg/kg) and Sulfur Species (%) in Slag and Subsoils with Values Assigned to Populations LIST OF FIGURES Figure Title 1-1 Site Map with Zinc Slag Pile Location 3-1 Zinc Slag Pile Sample Locations and Reconnaissance Information 4-1 Zinc Slag Pile Current Surface Area, Volume, and Angles of Repose 4-2 Zinc Slag Pile Historic Volume 4-3 Column Leach Results - Zinc Slag Cations 4-4 Column Leach Results - Zinc Slag Anions
MORRISON KNUDSEN CORPORATION
BB\1893\2INCRPT\F!nal-W 111 [Rev 001/13/93] APPENDIX Appendix Title A Field Work Documentation Al Sample Logs B Subcontractor Reports Bl Resource Technologies Group, Inc., Column Leach Test Results B2 Interpro, Inc. Preparation and Size Analysis Report C Statistics D Calculation Documentation Dl Pile Volume Calculations D2 Pile Metals Loading Calculations E Analytical Documentation El SDG Data Validation Reports E2 Analytical Data Base E3 Analytical Data Packages - Form I Summary Sheets F Air Quality - Emission Rate Estimate Documentation Fl Relevant pages from Simiu & Scanlan, 1978 F2 Table 11.2.1-1 from AP-42
MORRISON KNUOSEN CORPORATION
BB\1893\ZINCRFT\FinaJ-R1 IV [Rev 001/13/93) FINAL REPORT ZINC SLAG PILE REMEDIAL INVESTIGATION AT THE CALIFORNIA GULCH SITE
EXECUTIVE SUMMARY
In late 1991 and 1992, Denver & Rio Grande Western Railroad Company (D&RGW) undertook a remedial investigation (RI) of the slag pile associated with the former Western Zinc Smelter within the California Gulch site at Leadville, Colorado. Lake County is the current owner of this pile. Although D&RGW has never owned the zinc slag pile or used it for any purpose, they agreed to undertake the investigation concurrent with a remedial investigation for the lead slag piles at the site. D&RGW was named a Potentially Responsible Party at the California Gulch site in 1986 due to their ownership of three lead slag piles, which had been purchased for use as railroad ballast. Both remedial investigations were performed under Administrative Order on Consent CERCLA-Vni- 92006. The purpose of the RI was to characterize the zinc slag pile in sufficient detail such that its chemical and physical properties could be evaluated for potential impacts on human health and the environment. No previous investigations of this pile had been undertaken at the site and, therefore, no data existed for the pile. During the scoping process, data gaps were identified as the pile size and volume, particle sizes, geochemical characteristics, leachability, deflation potential, and geotechnical stability. RI data was collected to fill these gaps, as well as to assess the viability of five potential release mechanisms identified in the site conceptual model. These five release mechanisms included wind, leaching, mixing by human activities, runoff by particulates, and direct contact. Direct contact was discounted in the baseline human health assessment conducted by EPA, leaving four remaining mechanisms to be evaluated during this RI. The investigation consisted of several major tasks, including literature and document review, field investigation and sampling, laboratory testing and analysis, and data evaluation and summary.
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-RI 1 [Rev 001/13/93] Available literature was reviewed to summarize the history of zinc smelting and slag pile development. Aerial photographs were also reviewed to determine gross changes in volume over time, indicating use of the slag. During site reconnaissance, the former smelter site was investigated for evidence of slag, other smelter debris or byproducts, general physical properties, and visual indications of impact to the surrounding environment. Structural features of the piles were mapped for input to geotechnical stability determinations and the pile was surveyed for accurate calculation of the current pile volume. Indications of environmental impacts from zinc slag, particulate movement from precipitation runoff, and stability concerns were not observed. Sampling locations were selected by identifying grid locations using a random number generator. Four discrete samples were then collected from the surface to a depth of 3 feet using shovels and a backhoe. Appropriate quality assurance procedures were adhered to during the sampling phase, as well as the analytical phase, of the work. Each of the samples was submitted for laboratory compositional, leachability, and particle size testing. A portion of each sample was also sent to Resurrection's field laboratory for incorporation in the Resurrection/ASARCO metals speciation program. Compositional analyses included total metals, water-soluble anions, and acid-base accounting. Leachability testing included Synthetic Precipitation Leaching Procedure (EPA Method 1312) and column leach tests, which were intended to simulate, as closely as possible, in situ conditions. Compositional results showed that the slag is an iron silicate with substantial amounts of aluminum, manganese, calcium, and zinc. Geometric mean concentrations for the four primary metals of concern at the site are as follows: - Arsenic 211 mg/kg - Cadmium 14.1 mg/kg - Lead 568 mg/kg -Zinc 66,000 mg/kg The dominant form of sulfur is sulfate. Acid generation potential, when detected, was more than compensated for by the neutralization potential due to the presence of carbonate.
MORRISON KNUOSEN CORPORATION BB\iea3\ZINCRPT\Flna.-K 2 IRw 001/13/93] Leaching analysis, which included both SPLP and column leach studies, showed minimal leaching of metals of concern. SPLP results for all elements tested in slag were below the toxicity characteristic criteria, listed in 40 CFR 261.24. Mean values for the contaminants of concern were generally two orders of magnitude lower than these regulatory thresholds. Column leach tests showed similar low levels of leaching, although studies were not continued long enough to determine the steady state concentrations of lead in leachate for two of the piles. It should be noted that several test design factors make the leaching results more conservative than what is expected under normal site conditions. These factors include the following: The lixiviant used contained none of the carbonates typically found in natural rainwater. The lixiviant was a sulfuric/nitric acid mixture which is a more aggressive solution. The leaching test used equal periods of wet and dry simulating an eight year period of precipitation. Insitu conditions would indicate that the piles are generally dry the majority of the time. • Leaching of metals did not begin until approximately half way through the testing period indicating that leaching does not begin until surface conditions are altered to be conducive to leaching. SPLP leach testing, assumed to be at equilibrium, showed leached metals values less than the maximal values in cycles at the end of the column leach test. In situ leaching conditions would more closely approximate equilibrium. • Analysis of subslag materials from beneath three major lead slag piles showed low values of metals of concern, indicating that any leaching produced by the piles has not severely impacted the materials under the piles. The buffering capacity of the slag was still in effect at the conclusion of both the SPLP and column leach tests, evidenced by the raising of pH values from the initial 5.0 to greater than 7.0 in the lixiviant.
MORMSON KNUDSEN CORPORATION BB\1883\ZlNCRFT\Flnal-RI J [R»001/13/B3] Particle size data and site-specific meteorological data were used to determine whether zinc slag fines have the ability to become airborne. Threshold friction velocities (the wind speed above which the surface material becomes airborne) were calculated using the mode of the aggregate size distribution. Wind data and the height of the piles were used to calculate the friction velocity. Results for the pile are: Threshold Friction Velocity 1.0 m/sec Friction Velocity 0.55 m/sec A friction velocity lower than the threshold demonstrates that sustained wind gusts in Leadville are not fast enough to cause wind erosion of the zinc slag. As with the leaching tests, several factors built in to the calculations make the results more conservative than what would be expected at the site. These factors include the following: If values more representative of air flow over rough terrain were used in the calculations, the friction velocity would have been lower than estimated. Air density, and therefore the lifting force of the wind at the same speed, is lower in Leadville. • Periods of high moisture, snow cover and frozen ground would also limit the potential for dust emissions. The results of the remedial investigation were compared to the site conceptual model developed during the scoping process. Of the five potential release mechanisms for waste piles (wind, leaching, mixing by human activities, runoff of particulates, and direct contact), only leaching of metals through contact with precipitation or other site waters was retained as viable for zinc slag piles within the California Gulch site.
MORNSON KNUDSEN CORPORATION BB\1883\ZINCRPT\Flnal-RI 4 [Rev 0 01/13/93] FINAL REPORT ZINC SLAG PILE REMEDIAL INVESTIGATION AT THE CALIFORNIA GULCH SITE LEADVILLE, COLORADO
1.0 INTRODUCTION This document presents the results of the Zinc Slag Pile Remedial Investigation (RI) at the California Gulch Superfund site at Leadville, located in Lake County, Colorado. The report was prepared by Morrison Knudsen Corporation (MK) for the Denver and Rio Grande Western Railroad Company (D&RGW) in compliance with Administrative Order on Consent (AOC) CERCLA-VIII-92-06. D&RGW was named as a Potentially Responsible Party in 1986 (Civil Action No. 86-C-1675, United States District Court, State of Colorado) due to their ownership of three lead slag piles in the California Gulch that had been purchased for use as railroad ballast. Although D&RGW does not own the zinc slag pile in Leadville, nor use it for any purpose, they have investigated it as part of an overall RI for slag piles within the California Gulch site. The Zinc Slag Pile RI was performed concurrent with the Lead Slag Pile RI in accordance with the Work Plan for Slag Pile Remedial Investigation at California Gulch Site (MK, 1991a) and the Sampling and Analysis Plan for Slag Pile Remedial Investigation at California Gulch Site Plan (MK, 1991b). 1.1 Purpose of the Remedial Investigation The purpose of the RI was to characterize the single zinc slag pile located within the California Gulch site in sufficient detail such that its chemical, physical, and mineralogical properties could be evaluated for potential impacts on human health and the environment. The RI fills data gaps relating to pile size and volume, slag particle sizes, geochemical characteristics, teachability, deflation potential, and geotechnical stability. The scope of this remedial investigation includes only the zinc slag pile associated with the Western Zinc Smelter. It is often referred to as the High School pile, based on its location (Figure 1-1), or the County pile, based on its ownership by Lake County. D&RGW has also investigated the major lead smelter-derived slag piles within the California Gulch site. As the lead slag (MK, 1992) is distinctly different from zinc slag, the RI reports have been submitted separately. MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 1-1 (Rev 001/13/93] HISTORIC SMELTER LOCATION RI/FS SITE BOUNDARY
ZINC SLAG VENEER OR SCATTERED ZINC SLAG PIECES SAMPLE LOCATION
CALIFORNIA GULCH CERCLA SITE ZINC SLALJADVIUEG PILE , COLORADINVESTIGATIOO N
SITSLAEG MAPILP E WITLOCATIOH ZINNC DENVER & DENVERRIO CRAND. COLORADE WESTERON RAILROAD NOTE: MORRISON-KNUDSEN CORPORATION TOPOGRAPHIC CONTOURS AND SURFACE FEATURES FIII NAUC (CM)) 1B93N054/XR893039 IDATtJ/M/92 PHOTOGRAPHDIGITIZED YB Y ANINTRASEARCD PROVIDED H BFROY ROMY 199F.0 WESTONAERIA. LINC. 1.2 Report Organization This report is organized to present RI field and laboratory activity summaries, data validation, analytical results and interpretations, and conclusions. Section 2.0 presents an overview of site conditions. No previous investigations have been conducted for the zinc slag at the site and, therefore, no historical information is included in this section. The scope of the Zinc Slag Pile Remedial Investigation, including all field, laboratory, and data analysis activities, is presented in Section 3.0. Section 4.0 presents the physical and chemical characteristics of the zinc slag pile determined during the RI, and Section 5.0 presents an interpretation of these results. Section 6.0 presents the summary and conclusions. Section 7.0 contains references. The appendices provide field documentation, the analytical database, data validation reports, summary sheets of laboratory data packages, calculation documentation, and statistical analysis backup.
MORRtSON KNUOSEN CORPORATION BB\1893\ZINCRFT\Final-RI 1-2 [Rev 001/13/93] 2.0 SITE AND DESCRIPTION The following description of the California Gulch site includes a brief history of the Leadville mining district, a general description of the physiographic and hydrologic properties of the site, and a description of zinc slag. Site information presented in this section is summarized primarily from studies performed prior to the 1991-1992 remedial investigation work. 2.1 Site Description The California Gulch site has experienced over 130 years of mining and smelting activity. The site encompasses the town of Leadville, Colorado, which is approximately 100 miles southwest of Denver at an elevation of 10,000 feet above mean sea level. Silver, gold, copper, lead, and zinc were mined by underground and placer methods from the major sulfide/carbonate ore deposit in the Leadville Mining District. Approximately 17 smelters are reported to have operated here. Only a few small- to moderate-sized mining operations now exist and no smelters currently operate in Leadville. The main mining-related features in the Leadville area today include the following: Tailings impoundments Slag piles More than two thousand waste rock dumps Abandoned mine, milling, and smelting facilities A few active mining and reprocessing operations • Mine water drainage tunnels The Yak Tunnel, which drains into California Gulch, was the main point-source discharge of acidic metal-laden water to California Gulch before treatment plant operations began in 1992. This tunnel drains underground mining areas east of Leadville. In 1983, the California Gulch site was placed on the EPA's National Priorities List because of heavy metals loading to the Arkansas River. Climatology The climate of the Leadville area is typical of mountainous areas in central Colorado. The area has extreme temperature changes from summer to winter and in any season can experience rapid changes of weather caused by storms travelling primarily from west to east. Local topographic features strongly influence climatic variations in the study area. Average
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-Rl 2-1 [Rev 001/13/93] annual precipitation is 12.67 inches (Res-Asarco, 1991). July and August have the most precipitation, and December and January have the least. Summertime precipitation is usually associated with convective showers. Precipitation occurs sporadically, causing occasional flash floods. Annual snowfall depths for mountains in the area range between 200 and 300 inches. During winter months, the depth of snow on the ground in Leadville is commonly 6 inches. The precipitation and temperature cycles give rise to an annual peak runoff, usually occurring during June. The temperature extremes range from 86 ° F to -30 ° F, with an average minimum daily temperature of 21.9 °. The average frost-free season is 79 days. Wind is predominately from the northwest (CDL, 1986). Geology The geology of the Leadville Mining District is complex. Bedrock consists of the Precambrian crystalline rocks overlain by quartzites, shales, limestones, dolomites, and sandstones of the Paleozoic era. Numerous faults exist at the eastern edge of the site, ranging in width from several feet to hundreds of feet. Several episodes of faulting, both pre-mineralization and post-mineralization, have been documented (EPA, 1989c). The primary minerals deposited by hydrothermal solutions were predominantly sulfides of iron, zinc, and lead, but also included copper, silver, and gold. Late-Tertiary tectonic activity faulted the mineralized zones into blocks and exposed them to oxygenated ground waters. Sulfide minerals were oxidized, formed sulfuric acid, and released metals into solution. These solutions were transported to carbonate zones, where precipitation reactions occurred between the mineralized sulfuric acid solutions and the carbonate rock. This deposition zone of secondary, or remobilized, minerals is termed the oxidized zone. The resulting carbonate ores formed the dominant ore zones in many of the area's early mines (EPA, 1989c). The change in geology is significant west of the Pendry Fault, which is often used to demarcate upper from lower California Gulch and is located at the eastern edge of Leadville. Above the fault, Precambrian crystalline rocks are an upthrust relative to stratigraphic units of sediments or alluvium. Below the fault, three identifiable geologic units are noted: bedrock, lake bed sediments, and high-terrace gravels. The thickness of the upper and middle stratigraphic units (gravels and lake bed sediments) increases from east to west. The upper unit varies in thickness from approximately 50 feet near the Pendry Fault to several hundred feet near the Arkansas River. Placer operations and mine waste
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 2-2 [Rev 0 01/13/93] disposal probably altered the surface and near-surface features of the high-terrace gravels stratigraphic unit (EPA, 1989c). Ground Water The complex geology in the upper California Gulch area has a significant impact on ground- water movement. Ground water occurs in both bedrock and alluvial systems, and recharge is principally from infiltration of snowmelt and rainfall. Ground water migrating through the bedrock system east and southeast of Leadville discharges directly to California Gulch surface waters, into mine workings and the Yak Tunnel, or into downgradient bedrock or alluvial ground-water systems (EPA, 1989c). In lower California Gulch, there is an active interchange between the shallow ground-water system and the surface water. Therefore, a pathway exists for metal contaminants originating from the Yak Tunnel, or other sources that contribute to surface water contamination, to affect ground-water quality. Ground-water quality is strongly influenced by depth, with the poorest quality found at the shallowest depths. Generally, the highest metal concentrations are within 25 to 50 feet of the surface (EPA, 1989c). Surface Water The California Gulch site encompasses about 15 square miles of surface water drainage upstream from the confluence of California Gulch with the Arkansas River. The main stem of California Gulch flows east to west, just south of Leadville, and drains water from several small tributaries to the north and south. The Stray Horse Gulch/Starr Ditch watershed is the largest subbasin and drains lands extensively affected by mining operations. All tributaries to California Gulch, as well as the upper California Gulch itself, are ephemeral drainages. California Gulch receives flows from two continuous point-source discharges: the Yak Tunnel treatment plant at 1 to 2 cubic feet per second (cfs), and the Leadville wastewater treatment plant at approximately 1 cfs (EPA, 1989c). Annual flows in both the Arkansas River and California Gulch are normally highest in the spring during snowmelt and lowest in the fall and winter. Local summer thunderstorms are, however, capable of producing high-intensity, short-duration flows in the Gulch. Flooding potential in the Gulch is high because of lack of vegetative cover. Maximum flood conditions in the area are expected in the May-June snowmelt period (EPA, 1989c).
MORRMON KNUDSEN CORPORATION B8\1883\ZINCRPT\Fina!-RI 2-3 [Rw 001/13/93] According to previous data, water quality in the upper Arkansas River is degraded below the discharge from the Leadville Drainage Tunnel, markedly degraded below California Gulch, and improved by the clean water inflow from creeks further downstream. The highest metal concentrations occur in the spring during snowmelt. During the 1984, 1985, and 1987 investigations by EPA, primary drinking water standards for cadmium and lead were commonly exceeded, as were the Aquatic Water Quality Criteria (AWQC) for cadmium, copper, lead, and zinc (EPA, 1989c). 22 Zinc Slag Description Slag in the vicinity of the Western Zinc Smelter area is a mineralized by-product resulting from the volatilization of zinc from zinc oxide and carbonate ores in a Wetherill furnace. In this furnace, briquettes of ore and anthracite were fed onto fuel burning on a cast-iron grate. A zinc vapor evolved and was subsequently oxidized. The fumes, generally zinc oxide, were collected in the baghouse as the smelting product. The zinc smelter by-products are scoriaceous slag, coal clinker, and ash. The slag is a highly vesicular material, often with a yellow or reddish oxide rind. The specific gravity of the zinc slag resulting from the Wetherill process is notably less than that of lead slag, likely due to the vesicles formed by the expansion of gases. The slag typically contains approximately 16 percent iron and 14 percent silicon, substantial amounts of aluminum, manganese, calcium and zinc, as well as traces of other residual base metals. Figure 1-1 is a map of the site that shows the historic zinc smelter location and the slag pile sampled under this RI. The general characteristics and history of this slag pile are discussed in following sections. 2.3 Previous Investigations Several previous investigations at the California Gulch site have addressed lead slag; however, no existing data is available for the Western Zinc slag pile.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 2-4 [Rev 001/13/93] 3.0 ZINC SLAG PILE INVESTIGATION The Zinc Slag Pile RI consisted of literature research, field investigation, and laboratory analyses. Historical research was performed relating to the development of the Western Zinc smelter and its associated slag pile. Field activities included inspecting, surveying, and sampling the pile. Laboratory activities included compositional, teachability, and physical testing of the slag and subslag samples. The samples were also submitted to the metals speciation program undertaken by ASARCO and Resurrection Mining Corporation, other PRPs at the California Gulch site. 3.1 Historical Research Available literature was reviewed to summarize the history of Leadville area smelters and the development of associated slag piles. The key resource for this summary was Historical Mineral Processing Operations of the Leadville Mining District, (EPA, 1991), a report of historical smelter and milling operations prepared for the site by Jacobs Engineering Group. Other references reviewed include: Leadville: Colorado's Magic City, by Edward Blair. Pruett Publishing Company, Boulder, Colorado, 1980. Draft Remedial Investigation Scoping Document California Gulch Site, Leadville, Colorado, Prepared by Woodward-Clyde Consultants for Res- ASARCO Joint Venture, April 1991. Ores to Metals, by James E. Fell, Jr., University of Nebraska Press, Lincoln, Nebraska, 1979. 32 Field Activities The Zinc Slag Pile RI activities included field reconnaissance to describe the Western Zinc slag pile and materials in the vicinity of the pile. Additionally, the pile was surveyed to document its size and location. Samples were obtained from locations randomly selected from a grid system established for the pile.
MORM80N KNUDSEN CORPORATION BB\1893\ZINCRPT\Fln«l-RI ,?-! [Raw 001/13/93] 3.2.1 Reconnaissance Several decades of aerial photography were used to assist in identifying the gross characteristics of the smelter and slag area. A summary of the photography reviewed is as follows: Date Agency Project Scale Roll Frame Numbers 9-23-56 Forest Service DZZ 1:20,000 6 122-124 9-21-58 Forest Service DZZ 1:20,000 21 30-32 9-23-64 USGS GS-VAXS 1:31,500 1 156,157,161,162 8-31-75 Forest Service 08065 1:15,840 974 068,069,095,096 9-4-76 Forest Service 08065 1:15,840 1,275 187,188 8-27-90 Intrasearch Denver 90145 1:14,400 90,145 9-11, 22-24 The historic smelter location was visited by an MK geologist and field engineer on May 11, 1992. The slag pile was described for physical properties such as size, color, general particle size, texture, and signs of weathering. The pile was photographed and plotted on the base topographic map of the site. Proximity of the pile to residences or other structures, streams, ephemeral runoff channels, and other smelter- or mining-related wastes or structural debris was noted. Additionally, any evidence of slag impacting the surrounding environment, such as fines transported from the pile by wind or water, stressed vegetation, and iron staining was noted. The zinc slag pile structural features were observed for bedding and layering, including thickness and orientation. The presence of fractures or cracks was investigated, along with any conditions that might have indicated block movement either by rotation or normal faulting. Any talus at the base of slag pile was noted and angles of repose were determined to assess slope stability. Surveying The Western Zinc slag pile was surveyed by a professional survey team on May 11, 1992, after the December 1991 sampling effort, because snow cover prohibited accurate surveying at the time of sampling. The survey was performed to allow the addition of slag pile contours to the existing base map and calculation of the pile volume to within approximately 10 percent error. Elevational data for the slag pile perimeter, top and toe, and grade breaks were determined so that the pile height, side slopes and volume could be calculated. A data file of the coordinates for each point surveyed was used in conjunction with AutoCAD to develop contour maps of the pile and integrate them into the existing base map. Volumes were also calculated using the AutoCAD software, AutoCOGO.
MORRMON KNUDSEN CORPORATION BB\1883\ZINCRPT\F1n«l-R! 3-2 fFtoiO 01/13/93] 3.2.3 Sampling Zinc slag pile sampling was performed on December 4, 1991. The details of the sampling procedures are presented in the Sampling and Analysis Plan (SAP) (MK, 1991b). No variances from these procedures were required at the Western Zinc Pile. 3.2.3.1 Sample Locations The sample locations were randomly selected on a rectangular grid system overlain on maps of the slag pile. This procedure for selecting random sample locations is provided in Methods for Evaluating the Attainment of Cleanup Standards (EPA, 1989b) and the base map with the superimposed grid system is provided in the SAP (Section 3.0, MK 1991b). Four discrete sample locations were selected using a random number generator to identify cell numbers within the grid system (MK, 1991b). The cells were then located in the field by tape and/or pace compass traverses from recognized points on the base maps. Samples were collected from the center of a grid cell. Generally, cells that occurred entirely on a portion of the slag pile that had a slag thickness greater than three feet and were accessible, were sampled. One cell at the Western Zinc pile did not meet the thickness criteria, and an alternate cell was randomly selected. The sample locations are depicted on Figure 3-1. Photographs of each location were taken and the slag pile features were noted in the log book. 3.2.3.2 Surface Slag Sampling Procedures The four slag samples were obtained with a backhoe, over a 0- to 3-foot depth range. The initial sample size collected was 400 pounds. This sample size was based on recommendations from Standard Practice for Sampling Aggregates, ASTM Method D-75, (ASTM, 1992b). Each sample was placed on a high density polyethylene (HDPE) sheet and a sample homogenizing procedure was performed by successively lifting each corner of the HDPE and rolling the sample over itself. This was performed repeatedly until the sample was thoroughly mixed. The sample was then piled into the shape of a cone, flattened, and divided into quarters using plastic shovels. One quarter was randomly selected and, along with its opposite quarter, collected for laboratory testing and analysis. MORRISON KNUOSEN CORPORATION 88\1893\2INCRPT\Final-RI 3-3 [Rev 001/13/93) LEGEND SURFACE CONTOUR INTERVAL 2' BUILDING A HSS101 SAMPLE LOCATIONS AND IDENTIFICATION SMELTER RUBBLE AREA NOTE: TOPOGRAPHIC CONTOURS AND SURFACE FEATURES DIGITIZED BY INTRASEARCH FROM 1990 AERIAL PHOTOGRAPHY AND PROVIDED BY ROY F. WESTON, INC. SCALE FEET 50 100 150 200 1"=100' N 515,000 -
LAKE COUNTY HIGH SCHOOL
N 514,500 CALIFORNIA GULCH CERCLA SITE ZINC SLAG PILE INVESTIGATION LEADVILLE, COLORADO FIGURE 3-1 ZINC SLAG PILE SAMPLE LOCATIONS AND RECONNAISSANCE INFORMATION DENVER & RIO GRANDE WESTERN RAILROAD ______DENVER. COLORADO______(6& MORRISON-KNUDSEN CORPORATION FILE NAME (CAD) 1893N014 lD»TE:9/06/91 j ACCESS KOW,_____ j ______/ PROJECT SUFFIX TASK DRAWING NUMBER REV. 1893 630 06-900 FIGURE 3-1 A Each sample for testing and analysis was placed in two five-gallon buckets and one one- gallon bucket. The buckets were sealed and labeled with identification numbers. At the end of each day, all samples were transported to a locked shed for shipment to the sample preparation and splitting laboratory. 3.2.3.3 Decontamination Procedures Decontamination was performed to prevent cross-contamination of samples. Sampling tools such as shovels, trowels, and plastic buckets were initially cleaned by mechanically removing any loose materials. Next, the equipment was scrubbed with a non-phosphate detergent (Alconox) and water solution until no visible material remained, and then rinsed with tap water and deionized water. HDPE sheets and parts of heavy equipment in contact with slag were decontaminated with a high pressure, hot water sprayer, and then rinsed with deionized water. Decontamination was performed as close as practical to the associated sample location and spent water was discarded on the ground. One equipment rinsate sample was collected to verify that the decontamination procedures were adequate. Sampling equipment was stored in clean plastic bags after air drying. Clean tools and HDPE sheets were used for each sample location. Laboratory Activities Samples were transmitted to the laboratories under chain-of-custody protocol. Laboratory activities were performed as specified in the SAP (MK, 1991b). Chemical analyses included both compositional and leachability testing. Physical analyses were performed to determine the particle size distribution of the zinc slag material. Table 3-1 presents the analyses performed on the zinc slag samples. Table 3-2 summarizes the analytical methods and sample size requirements. Sample preparation and particle size determination were performed by Interpro of Golden, Colorado. Silver Valley Laboratories, Inc. (SVL) of Kellogg, Idaho performed compositional and Synthetic Precipitation Leaching Procedure (SPLP) testing. The column leach test was performed by Resource Technologies Group (RTG), Wheat Ridge, Colorado. Eluate from the column leach test was analyzed by SVL. Prepared zinc slag samples were also submitted to Resurrection Mining Corporation at their Leadville, Colorado field office for analyses under Final Work Plan - Metals Speciation and Source Characterization at California Gulch CERCLA Site Work Plan (Resurrection, 1992).
MORMSON KNUD8EN CORPORATION BB\1893\ZINCRPT\Flnal-W 3~4 [Rev 001/13/83] TABLE 3-1 ZINC SLAG SAMPLE ANALYSIS SUMMARY COMPOSITIONAL LEACH TESTS PHYSICAL SAMPLE NO. ANALYSES ANALYSES
mo.m vN *~ . Ztn CO 3 CO t—- o•> Table 3-2
Matrix Analysis Type Analytical Method Reference Sample Size Modifications Zinc Slag Total Metals Digestion CLP SOW 03/90 CLP SOW 100 grams Add Silicon, delete Mercury Bureau of Mbes D3683-78 ASTM More Rigorous Disgestion Zinc Slag Rainfall Shake Method 1312 SW-846 1000 grams No Particle Size Reduction Increase Sample Size Zinc Slag Sulfur forms 3Z4/3.2.6 EPA 600/2-78-054 500 grams Analysis Performed on Neutralization Potential 3.2.3 EPA600/5-78-054 Water-Soluble Fraction of Cation Exchange Capacity ERA 9080 SW-846 Material Zinc Slag AnionK CT, SO** NO» Method 300.0/310.1 EPA 600/4-78 500 grams None NO', following water soil extraction Zinc Slag Particle Size Analysis Seive Analysis ASTMD422 Varies Microtrac to augment Hydrometer ASTMD422 hydrometer Microtrac Sample Preparation and Laboratory Submittal The bulk samples of zinc slag, with the exception of the SPLP and the column leach sample, were delivered to Interpro of Golden, Colorado for sample preparation. The SPLP samples were forwarded immediately to SVL for analysis without particle size reduction or other preparation. At Interpro, sample preparation was preceded by particle size analysis of the samples. After the particle-size determinations were performed, the seived materials were recombined in the original sample container. The entire sample was crushed to minus 3 mesh (6.7mm) with a jaw crusher and a roll crusher. The minus 3 mesh material was blended and a 10- to 11- pound sample was split from the mixture. This sample split was further reduced in a plate pulverizer to minus 60 mesh (250 microns). The pulverized sample was then blended and split into 1-pound samples, each placed in a glass bottle, labeled, and sealed. The 1-pound, minus 250 micron prepared samples were submitted to SVL and interested parties for analysis. Interpro has archived pulverized samples (1-pound jars) and unprepared 5-gallon buckets of each sample. 3.3.1 Compositional Analyses Compositional analyses were performed to determine the bulk chemistry of the zinc slag. The compositional analyses included the following: Total Metals Anions Acid Forming Potential including all Sulfur Forms Neutralization Potential • Cation Exchange Capacity 3.3.1.1 Total Metals Total metals were determined for the zinc slag samples by inductively coupled plasma (ICP) and graphite furnace atomic absorption (GFAA). Analyses were performed according to methods described in the Contract Laboratory Program Statement of Work for Inorganics Analysis (SOW 4/90) (EPA, 1990a). As the method for total digestion in SOW 4/90 is not rigorous enough to completely digest the slag matrix, the U.S. Bureau of Mines digestion method was used for sample preparation as reported in A Simple Low-Cost Method for the Dissolution of Metal and Mineral Samples in Plastic Pressure Vessels (Bureau of Mines, 1980).
MORRISON KNUDSEN CORPORATION BB\1893\2INCRPT\Flnal-RI 3-5 [Rev 001/13/93] The U.S. Bureau of Mines digestion method uses more reactive reagents. This digestion method is included in Appendix H of the Slag Pile SAP (MK, 1991b). Each sample was prepared for Target Analyte List (TAL) metals analysis according to procedures required by SOW 4/90. The sample is initially crushed and mixed thoroughly. A representative one-gram subsample is then digested using the U.S. Bureau of Mines digestion method with hydrofluoric acid, nitric acid and hydrochloric acid. After the digestate is boiled and cooled, boric acid is added. The solutions are then rebelled, cooled and analyzed. Arsenic, lead, and selenium were measured by GFAA. The concentrations of the remaining analytes (aluminum, antimony, barium, beryllium, cadmium, calcium, chromium, cobalt, copper, iron, magnesium, manganese, nickel, potassium, silicon, silver, sodium, thallium, vanadium and zinc) were measured by ICP. Mercury concentrations were not determined, as specified in the SAP (MK, 1991b). 3.3.1.2 Anions Method 300.1/310.1 (EPA, 1982) following water/soil extraction was used to determine the following anions in the zinc slag material: Chloride Sulfate Nitrate/Nitrite Anions were analyzed to determine concentrations for input to geochemical modeling and as corroboration with metals speciation results. 3.3.1.3 Sulfur Forms Potential acidity of zinc slag was determined for each sample by measuring sulfur concentrations according to EPA Method 3.2.4 from Field and Laboratory Methods Applicable to Overburdens and Minesoils EPA-600/2-78-054 (EPA, 1978). A less than 60 mesh slag sample is heated as oxygen is passed through the sample. A starch solution, which collects the sulfur dioxide as it is released, is then titrated and the percent total sulfur calculated based on the starting mass and the titration measurement. If all of the sulfur occurs in pyritic forms, the calculation of maximum potential acidity from sulfur corresponds with actual potential acidity from sulfur. If part of the sulfur occurs in other insoluble forms, i.e., sulfate, the maximum as calculated will overestimate acid-forming MORRISON KNUDSEN CORPORATION BB\1S83\ZINCRFT\FinaJ-« 3-6 [Rev 001/13/93] potential. In order to determine the true acid forming potential, a second method for determining the sulfur content of the samples was utilized. This was EPA Method 3.2.6 (EPA, 1978). This method determines the hydrochloric acid extractable, nitric acid extractable, and non-extractable forms of sulfur, which are not considered to be acid formers. 3.3.1.4 Neutralization Potential Neutralization potential was determined by Method 3.2.3 (EPA, 1978). The amount of neutralizing base, including carbonates, present in overburden materials is determined by treating a sample with a known excess of standardized hydrochloric acid. The sample and the acid are heated to ensure that the reaction between the acid and the neutralizes goes to completion. A calcium carbonate equivalent of the sample is obtained by determining the amount of unconsumed acid by titration with standardized sodium hydroxide. 3.3.1.5 Cation Exchange Properties Cation Exchange Capacity (CEC) is a measure of how readily a material will sorb cations onto its surface or into its matrix. The CEC was measured using EPA method 9080 (EPA, 1986), in which results are expressed in milliequivalents (meq) per 100 grams of material. 3.3.2 Leachability Testing Each of the collected zinc slag samples was subjected to leaching tests following EPA Method 1312, the Synthetic Precipitation Leaching Procedure (SPLP). One sample was also subjected to column leach testing. Both tests are described below. Method 1312 - Synthetic Precipitation Leaching Procedure (SPLF) SPLP analyses were performed according to standard methodology, with two minor modifications. The method states that the sample passing a 9.5mm sieve (particles smaller than about 3/8 inch) will be utilized. For the zinc slag samples, neither size reduction nor screening was employed. Secondly, the method states that the minimum sample size is 100 grams. The sample size used for the slag was 1000 grams. A corresponding increase in the extraction fluid maintained the specified extraction fluid to sample ratio of 20:1. These method modifications were initiated to ensure that field conditions were represented as closely as possible. As specified by the method (for soils west of the Mississippi River), the extraction fluid was pH 5.0 ±0.2 units using a 60:40 ratio of sulfuric and nitric acid. This pH corresponds to that MORRtSON KNUDSEN CORPORATION BB\1883\2INCRPT\Fln«l-W 3'7 (R«vO 01/13/93] estimated for the area. As no data specific to Leadville exists, MK compiled data for rainfall from numerous weather stations in mountainous regions of Colorado. Based on this state-wide data, the average pH of the rainfall in the Leadville area is assumed to be approximately 5.0 (Table 3-3). The extraction fluid and samples are mechanically shaken for a 24-hour period. The eluate is then filtered through a 0.6 -O.Sum glass fiber filter and analyzed for metals and anions of interest. Column Leaching Tests The column leach test was run using a downflow unsaturated configuration. A column diameter of eight inches was selected to be several times the nominal diameter of the zinc slag particles to be tested. The testing laboratory prepared, packed, and consolidated the material into the three-foot-long column. The unsaturated downflow column required periodic presentation of the lixiviant followed by an equal period of draining and aeration. Each introduction of fluid was designed to simulate a one-inch rainfall event for the eight- inch diameter column, and each event was equal to approximately 0.8 liters of lixiviant. One hundred cycles or "rainfall events" were conducted with collection of the eluate at the conclusion of each event. Initially, the eluate from events 5, 25, 50, 75 and 100 were analyzed for anions and TAL metals (plus silicon minus mercury). After evaluation of the results from these events, additional event eluates were analyzed to fill data gaps (Section 4.5). Physical Testing Sieve, hydrometer, and Microtrac analyses were performed to determine the particle-size distribution of zinc slag. Sieve Analysis Sieve analysis was conducted following ASTM D 422-63 (ASTM, 1992a). This method provides for quantitative determination of particle size distribution in soil matrices. The distribution of particle sizes greater than 75 microns (retained on a number 200 sieve) is determined by mechanically shaking the material through a series of successively smaller sieves. The material retained on each sieve is weighed to determine the percent of each particle size. For this analysis, Standard Tyler sieve sizes were used.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\FinaJ-RI J-Q (Rev 001/13/93] Table 3-3
pH (Standard Units) Elevation StatfoB Name County (meters) 1984 1985 1986 1987 1988 1989 1990 Sugarloaf Boulder 2524 4.97 5.00 5.18 4.87 Niwot Saddle Boulder 3520 Four Mile Park Garfield 2502 5.05 5.50 5.29 Sunlight Peak Garfield 3206 Rocky Mtn Nat'1 Park - Beaver Meadows Larimer 2490 5.14 4.99 5.07 5.19 526 524 -Loch Vale Larimer 3159 Dry Lake Routt 2527 4.78 Buffalo Pass Routt 3234 Engineer Mtn Guard Station San Juan 2758 4.92 5.08 MolasPass San Juan 3286 Manitou Teller 2362 4.90 4.86 4.82 4.85 5.09 4.94 The geometric average of these values is 5.04. Blanks indicate no data was collected. - indicates the data did not meet the NADP completeness criteria. The stations in the same county are paired mountain/valley meteorological stations. Hydrometer Analysis Hydrometer analyses were conducted on materials passing the number 10 Tyler sieve, i.e., material sizes less than 1.7mm, following ASTM Method D422-63 (ASTM, 1992a). This technique involves placing the material in solution containing a dispersing agent and measuring the density of the solution as the material settles. Size fractions are determined from the time required for the material to settle out of solution. The specific gravity of the minus 10 mesh slag was determined for use in particle size calculations. Microtrac Analysis The Microtrac method was used to evaluate only the smaller particle size fractions in the sample portion that passed the 48 mesh sieve. The Microtrac method uses the general theories of low angle, forward light scattering, combined with microprocessor technology. A "cloud" of particles is passed through a helium-neon laser beam causing light to be scattered at angles related to particle size. Specially-designed optical equipment unscrambles the light information into distinct channel sizes over the range of 0.12 to 700 microns. This technique provides a continuum of particle size measurements over the range of interest. The data is reported as a percentage of material, by volume, within a certain size range. 3.4 Air Quality Investigation Air pathway analysis was used to determine potential ambient air concentrations of metals and particulates resulting from the wind erosion of the zinc slag pile. The first step in this approach is to characterize the emission potential of material from the zinc slag pile. In the absence of site-specific emission measurements, the emissions are estimated. It is also necessary to characterize the conditions under which emissions from the zinc slag pile occur. Once the emission information is obtained, the dispersion of this material downwind and resulting concentrations are determined as a function of atmospheric characteristics, i.e., wind speed, wind direction, and atmospheric stability. The dispersion model is the tool that performs the calculations necessary to determine the downwind concentrations from the emission rates and meteorological conditions.
MORRtSON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-« 3-9 [Rev 001/13/93] 3.4.1 Meteorological Data MK coordinated with ASARCO to obtain meteorological data collected under their Administrative Order on Consent for the Yak Tunnel. ASARCO's technical consultant had established two meteorological stations within the California Gulch site: one near the Yak Tunnel and one near the Colorado Mountain College. A year's worth of data had been collected at each of these stations. The Leadville airport also has a meteorological station within the site that has been established for several years. Data from the Colorado Mountain College (CMC) station (Res-ASARCO, 1991) was selected as the most representative data set available for assessing air quality impacts from the zinc slag pile. The Yak Tunnel station data is likely affected by local topography that results in wind flow patterns not representative of the zinc slag pile location. The airport observations are limited to periods when personnel are working, typically not through the night, and are therefore not appropriate to reliably serve as input to air emissions calculations or an quality dispersion model. The data from the CMC station consists of hourly averages of temperature, wind speed, wind direction, and sigma theta (the standard deviation of the horizontal wind direction used as an indication of atmospheric stability) measured at 10 meters above ground level. Missing data values were noted by MK but not filled. Sixty-five days were reported for which some or all hours had missing data. Most of these days occurred in May, September, October, and November resulting in an 82 percent data collection efficiency. Instead of filling in inappropriate data, MK deleted each day with missing data from the data set. The final meteorological data file covered the period from October 1990 to September 1991. 3.42 Emission Rate Estimates Potential fugitive dust emissions from the zinc slag pile were estimated using the procedure outlined in AP-42, section 11.2.7 (EPA, 1988a), as recommended by the EPA (EPA, 1992). The first step in this procedure is to determine the threshold friction velocity (i.e., the wind speed above which surface material becomes airborne) from the mode of the particle size distribution. The procedure to determine particle size by sieve analysis is described in AP- 42. Variations from this procedure included using a sample of material collected from the surface to a depth of three feet instead of collecting just the surface layer of loose particles, and sieving with several more sizes of sieves than the five mentioned in the method. Using the zero-to-three-foot sample data is considered representative of the surface material
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-RI 3" 10 [Rev 001/13/93] because the pile is relatively homogeneous with respect to depth. The data from the sieve analysis was re-grouped so that the sieve categories would match those specified in the method. The results of the size distribution are presented in Table 4-1. Of the four samples collected, only one sample, HSS102, had a bimodal distribution, with a high percentage of large material and fines. Most of the material for the other three samples did not pass through the Tyler number 5 sieve and the data was not bimodal. The wind speed that is necessary to erode the Western Zinc slag pile material and suspend it in the atmosphere is determined by relating the mode of the size distribution to the threshold friction velocity (that wind velocity at which particles begin to become entrained into the ambient air). The information in Table 11.2.7.1 in AP-42 relates modes of particle size distributions to threshold friction velocities. The data in the table, reproduced in Appendix F, was determined empirically through research efforts by the EPA. The table indicates that the threshold friction velocity for particles the size of the zinc slag is greater than 100 centimeters per second (cm/sec). The next step is to determine if the wind speeds in the area are great enough to entrain surface material into the ambient air. This is done by comparing the threshold friction velocity with the wind speed. However, using hourly-averaged wind speed data for the comparison is not appropriate because most erosion events typically last between one and four minutes (EPA, 1988a). It is the sustained wind gusts embedded in the hourly-averaged wind speeds that are more relevant. The "fastest mile" parameter is the most routinely measured meteorological variable that best reflects the magnitude of sustained wind gusts. The fastest mile is defined as the value that represents the wind speed corresponding to the whole mile of wind movement that has passed by the one mile contact anemometer in the least amount of time. Typically, fastest mile data is available from Local Climatological Data (LCD) summaries. Since it is not collected at the Leadville airport, a literature search was conducted to find a suitable empirical relationship for deriving fastest mile data from hourly averaged on-site wind speed data. A suitable equation is contained in E. Simiu and R. H. Scanlan's book Wind Effects on Structures: An Introduction to Wind Engineering, (Simiu and Scanlan, 1978):
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 3-11 [Rev 001/13/93] Ut(z) = U3600(z)[l + (0.98 c(t))/ln(z/z0)] where z = height at which wind speed is to be determined z = roughness height c(t0 ) = constant = 1.02 for an averaging period of 100 seconds Uaeoo = hourly averaged wind speed Ut(z) = averaged wind speed at time "t" (The section presenting this conversion has been duplicated and provided in Appendix F.) Since a typical erosion event lasts one to four minutes (EPA, 1988a) and is capable of completely depleting the erosion potential for a given source area, a wind speed averaging time of 100 seconds was selected as a value that would yield a wind speed similar to the fastest mile speeds in LCD summaries. Application of this equation results in a "100-second" wind speed about 1.13 times higher than the "3600 second" wind speed. Thus, it is appropriate to multiply the maximum observed hourly wind speed by 1.13 to obtain the fastest mile. For example, the maximum observed hourly average wind speed was 9.12 m/sec, or 20.4 miles per hour (mph). Multiplying this value by 1.13 equals a 10.3 m/sec (23.05 mph) fastest mile. The 100-second period was selected to represent the duration of the typical erosion event for two reasons. First, it was within the range of erosion events, which the EPA specifies in AP-42, Section 11.2.7, Industrial Wind Erosion (EPA, 1988a), as lasting between one and four minutes (60 to 240 seconds). Second, in order to determine the wind speed that corresponds to the fastest mile, Equation 2.3.30 of Simiu and Scanlan (1978) needs to be solved. In order to solve this equation, the value of the coefficient c(t) needs to be quantified. Table 2.3.2 in the referenced text book lists several coefficients for select time periods (a copy of this table has been included in the Simiu and Scanlan attachment to this Appendix F). Only two coefficients are given for time periods that are within the 60- to 240-second range: 100 and 200 seconds. Of these two values, the 100-second coefficient was chosen. The 100-second value is conservative because it results in a greater fastest mile value than the 200-second coefficient; therefore, increasing the calculated emission rate.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-Rl 3-12 [Rev 001/13/93) Two articles have been reviewed with the intent of providing supporting evidence to verify applicability of the relationship between the hourly averaged wind speed and the wind speed which corresponds to the fastest mile. The two articles reviewed are as follows: Glidden, D.E. "Winter Wind Studies in Rocky Mountain National Park." Rocky Mountain Nature Association, Estes Park, Colorado, 1982. Judson, A. "The Weather and Climate of a High Mountain Pass in the Colorado Rockies." Rocky Mountain Forest and Range Experiment Station. Fort Collins, Colorado, 1965. Although the articles did not contain information on the wind speed corresponding to the fastest mile, the articles did contain wind data summarized over several time periods different from those recorded in Leadville, such as the fastest gust, 5-minute summaries, hourly summaries, and daily summaries. These summaries included maximums, minimums, and averages for the time period. To compare the data presented in the articles to the method which is used to calculate wind blown emissions for the zinc slag pile, the equation was modified slightly to compare the ratio of the fastest 1-second wind speed (gust) to the hourly wind speed. This corresponds to using c(t)= 3.00 in the Simiu and Scanlan equation (1978). The following table summarizes the results of the ratio of the fastest gust to the 1-hour wind speed (1-hour gust ratio) for four locations mentioned in the above referenced articles. The Mines Peak station was located near Berthoud Pass at an elevation of 3808 meters. The other three stations were located within the boundaries of Rocky Mountain National Park. TR3 and TRIO were located along Trail Ridge Road at an elevation of 11,601 feet and 11,817 feet, respectively. The Longs Peak station was located at the summit of Longs Peak and an elevation of 14,255 feet.
MORRISON KNUOSEN CORPORATION BB\1893\ZINCRPT\Flnal-RI 3"13 [Rev 001/13/93] Observed and Calculated 1-Hour Wind Speeds: Maximum Gust Ratios for Four Mountain Locations SITE AVG MIN AVERAGE AVG MAX CALCULATED Mines Peak N/A 2.0 N/A 1.36 TR3 1.27 1.61 2.53 1.42 Longs Peak 1.30 2.0 3.20 1.42 TRIO 1.21 1.58 2.20 1.37 The values presented represent the ratio of the maximum gust observed each hour to the 1-hour averaged wind speed. For example, for location TR3, the maximum gust was 1.61 times greater than the average 1-hour wind speed. The column labelled AVG MIN represents the minimum of all ratios of the fastest gust represents the maximum of all ratios. The above values were calculated using parameters corresponding best to each individual site. The anemometer height for each station was obtained from the references. A surface roughness height of 0.35 cm was assumed for each site, which corresponds to that of snow. The methodology used to calculate the 1-hour gust ratio appears to be within the range observed at several mountain locations. It was not possible to compare the calculated and observed values for other time averaging periods due to the lack of data presented in the articles. The fastest mile of 10.3 m/sec needs to be adjusted from the height of measurement (10 meters) down to the height of the pile surface; the adjusted wind speed at the surface is referred to as the friction velocity (u'). This is done using the logarithmic wind profile relationship as specified in AP-42, section 11.2.7, Equation 4: u* = 0.053 U10 The friction velocity is then compared to the threshold friction velocity calculated for the zinc slag to determine if the friction velocity is greater, indicating potential for wind erosion. Results from this step (presented in Section 4.4.2) eliminated the need to proceed with dispersion modeling.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 3-14 [Rev 001/13/93] 3.5 Relationship With Other Investigation Programs This Zinc Slag Pile RI required coordination with other California Gulch Remedial Investigation programs implemented by others. The information shared to date between the various programs as it relates to the Slag Pile RI is discussed below. Mineralogy and metal speciation studies are being performed by Resurrection and ASARCO under the Final Work Plan - Metals Speciation and Source Characterization at California Gulch CERCLA Site (Resurrection, 1992). Analytical data will be developed that characterize the distribution, geochemistry, and morphology of different metal compounds at the site. These factors may be critical variables in the determination of the bioavailability of lead and assessing the potential human health risk. The zinc slag samples were prepared (pulverized to minus 250 microns) and delivered to the Camp Dresser & McKee field laboratory in Leadville. It is understood that these samples will undergo various tests, including XRF, XRD, microprobe, optical microscopy, and lead isotope analysis. It is anticipated that these results will be used to determine metals ratios of the Western Zinc slag, origin of the ore that was smelted to form the slag, and relative bioavailability of slag particles based on the species of metals in the slag. 3.5.1 ASARCO Meteorologic Monitoring Program As stated previously, meteorologic data (Res-ASARCO, 1991) developed by Res-ASARCO under the California Gulch Air Monitoring Work Plan (EPA, 1990b) has been provided to MK and was used for input to the Western Zinc slag pile air dispersion modeling.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Flnal-FH 3-15 tRev 001/13/93] 4.0 CHARACTERISTICS OF THE ZINC SLAG PILE The results of historical research relating to the development of the zinc smelter and slag pile, field reconnaissance of the smelter and slag pile, and the physical and stability characteristics of the slag pile are reported in this section. A summary is also provided of the results of compositional and teachability analyses along with quality assurance sample data and data validation procedures. 4.1 Smelter History and Slag Pile Development Summary The intent of this summary is to give an overview of Leadville area smelter history, as it relates to the Western Zinc slag pile development. 4.1.1 Brief Histoiy of Leadville Smelting Although placer gold was found in California Gulch in 1859, lead-silver mining did not begin until the summer of 1874. By 1875, the Malta Smelter was built to process the silver ore. The following 27 years were Leadville's most productive and active period for mining and smelting. By 1879, all of the major lead smelter areas in the Leadville Mining District were operating; however, by August 1880, half of them were closed largely due to the coke famine of the previous winter (Blair, 1980). The smelters often changed ownership, capacity and processes. Several burned to the ground. By 1892, the smelters were resmelting older slag deposits for recovery of residual metals. In 1893, there was a silver panic during which all of the smelters closed with only a few of them reopening. Zinc smelting began in the early 1900s in Leadville and continued for only about 12 years. Lead smelting continued in Leadville until 1961. 4.1.2 Western Zinc Smelter and Slag Pile History The Western Zinc Mining and Reducing Company built a zinc smelter west of Leadville in 1914. The company changed its name to the Western Zinc Oxide Company in 1915 and to Western Zinc Concentrating Company in 1918. This smelter used a Witherell furnace, which oxidized ores to produce zinc oxide. It has been reported that some of the slag produced at this zinc smelter was sent to other smelters, including the Arkansas Valley Smelter, in order that lead, silver, gold and copper could be recovered. The zinc smelter closed in 1926 after generating an estimated 51,000 to 70,000 tons of slag (EPA, 1991). The Western Zinc slag pile is currently owned by Lake County.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\FinaI-R! 4-1 [Rev 001/13/83] 42 Field Reconnaissance of the Zinc Slag Pile and Smelter Area The field investigation phase of the Zinc Slag Pile RI included a reconnaissance of the historic zinc smelter location and slag pile. Reconnaissance activities included describing the old zinc smelter location, the slag pile and property in the vicinity of the slag pile for any other smelting debris or by-products, and other major physiographic or cultural features. Figure 3-1 presents observations from the field reconnaissance. The cross-hatched lines on the figure represent areas of smelter foundations and rubble. 42.1 The Western Zinc Smelter The Western Zinc Smelter slag area covers several acres near the Lake County Fair Grounds west of Lake County High School. The smelter foundation is located just east of the slag. This zinc slag is substantially different from the dense lead slag of the Leadville area, as it was formed by a different process, recovering a different metal. The colors often range from red to brown and the material is more vesicular than lead slag. Particle sizes range from soil-sized material up to pieces several inches in diameter. Much of the slag pile appears to have been worked, although there is one large area consisting of mostly welded material. Some of the soils in the area of the pile appear to be disturbed (excavated). The thinner zinc slag areas and soils support trees, bushes and grasses. Railroad tracks run nearby, as do several roads. No streams or ponded water were observed in the area. Also, no evidence of fines were observed to have washed from the pile by precipitation runoff. A number of bag-shaped mounds of grey cementicious material were located near the foundation ruins. Based on the smelting method used at this site and the coarsely woven fabric still adhering to several of the mounds, this material appears to be solidified zinc oxide baghouse dust. There are two locations in Leadville where zinc slag was observed on dirt roadways: on the road off of McWethy Drive that leads towards the La Plata slag pile and on a section of the road that passes to the north of the Hecla tailings ponds. Other potential uses of this material that could account for volume loss have not been documented. 4.3 Physical Characteristics Particle size and pile volumes are the major physical characteristics of the Western Zinc slag pile that were determined during the RI.
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-« 4-2 [Rev 0 01/13/93) TABU* 4-1 PARTICLE SIZE TESTING RESULTS ZINC SLAG PILE (HSS101)
SEIVE ANALYSIS MICROTRAC ANALYSIS SEIVE NO. SEIVE OPENING, mm % PASSING EQUIVALENT % FINER DIAMETER (pm) 6' 152.4 100.0 704.0 12.30 4" 101.6 100.0 592.0 12.09 3" 76.2 100.0 497.8 11.82 2' 50.8 94.8 418.6 11.47 1" 26.5 83.4 352.0 11.04 1/2" 13.2 69.4 296.0 10.51 3M 6.70 53.4 248.9 9.89 4 4.75 49.1 209.3 9.20 6 3.35 . 41.9 176.0 8.47 8 2.36 35.5 148.0 7.75 10 1.70 30.4 124.5 7.06 14 1.18 25.4 104.7 6.40 20 0.850 21.6 88.0 5.77 28 0.600 17.8 74.0 5.15 35 0.425 14.6 62.2 4.55 48 0.300 12.3 52.3 3.99 65 0.212 10.3 44.0 3.49 37.0 3.04 HYDROMETER ANALYSIS 31.1 2.65 26.2 2.31 SEIVE NO. SEIVE OPENING, pm % PASSING 22.0 2.03 18.5 1.79 10 1700 30.4 15.6 1.58 35 425 16.4 13.1 1.39 48 300 13.9 11.0 1.23 65 212 12.2 9.25 1.09 100 150 10.6 7.78 0.97 150 106 9.2 6.54 0.87 200 75 7.8 5.50 0.77 4.62 0.68 EQUIVALENT % FINER 3.89 0.60 DIAMETER (fun) 3.27 0.52 29 4.2 2.75 0.44 19 3.4 2.31 0.37 HYDROMETER 11 2.5 1.94 0.31 RESULTS 8 2.3 1.64 0.24 6 1.9 1.38 0.18 3 1.5 1.16 0.12 1 1.3 0.97 0.07 0.82 0.03 0.69 0.00 SPECIFIC GRAVITY 3.3
BB\123\zinctblsUbt4-1 6/29/92 TABLE 4-1, coot'd PARTICLE SIZE TESTING RESULTS ZINC SLAG PILE (HSS102)
SEIVE ANALYSIS MICROTRAC ANALYSIS SEIVE NO. SEIVE OPENING, mm % PASSING EQUIVALENT % FINER DIAMETER (pm) 6" 152.4 100.0 704.0 40.40 4" 101.6 100.0 592.0 39.85 3" 76.2 100.0 497.8 39.14 2' 50.8 97.3 418.6 38.19 1" 26.5 89.2 352.0 36.93 172' 13.2 77.3 296.0 35.35 3M 6.70 63.8 248.9 33.39 4 4.75 61.2 209.3 31.10 6 3.35 . 56.3 176.0 28.60 8 2.36 52.3 148.0 25.99 10 1.70 49.4 124.5 23.35 14 1.18 46.6 104.7 20.72 20 0.850 44.7 88.0 18.09 28 0.600 42.9 74.0 15.50 35 0.425 41.4 62.2 13.04 48 0.300 40.4 52.3 10.80 65 0.212 39.5 44.0 8.83 37.0 7.17 HYDROMETER ANALYSIS 31.1 5.80 26.2 4.71 SEIVE NO. SEIVE OPENING, pm % PASSING 22.0 3.85 18.5 3.17 10 1700 49.4 15.6 2.63 35 425 19.9 13.1 2.20 48 300 15.6 11.0 1.84 65 212 12.5 9.25 1.54 100 150 10.2 7.78 1.28 150 106 8.2 6.54 1.06 200 75 6.6 5.50 0.86 4.62 0.68 EQUIVALENT % FINER 3.89 0.51 DIAMETER (jan) 3.27 0.36 30 6.2 2.75 0.22 19 5.1 2.31 0.13 HYDROMETER 11 3.4 1.94 0.04 RESULTS 8 2.7 1.64 0.00 6 2.4 3 1.7 1 1.7
[SPECIFIC GRAVITY 3.3
BBV123tfnctblsttbl4-1a 6/29/92 TABLE 4-1, coot'd PARTICLE SIZE TESTING RESULTS ZINC SLAG PILE (HSS1Q3)
SEIVE ANALYSIS MICROTRAC ANALYSIS SEIVE NO. SEIVE OPENING, mm % PASSING EQUIVALENT % FINER DIAMETER 0*m) 6' 152.4 100.0 704.0 8.10 4' 101.6 100.0 592.0 8.03 3' 76.2 100.0 497.8 7.92 2" 50.8 93.8 418.6 7.73 r 26.5 75.5 352.0 7.45 1/2" 13.2 61.2 296.0 7.11 3M 6.70 44.0 248.9 6.72 4 4.75 41.3 209.3 6.30 6 3.35 34.3 176.0 5.85 8 2.36 27.9 148.0 5.39 10 1.70 23.0 124.5 4.95 14 1.18 18.2 104.7 4.53 20 0.850 15.2 88.0 4.12 28 0.600 12.3 74.0 3.73 35 0.425 9.9 62.2 3.35 48 0.300 8.1 52.3 2.98 65 0.212 6.7 44.0 2.64 37.0 2.30 HYDROMETER ANALYSIS 31.1 1.98 26.2 1.68 SEIVE NO. SEIVE OPENING, pm % PASSING 22.0 1.41 18.5 1.19 10 1700 23.0 15.6 1.01 35 425 13.0 13.1 0.86 48 300 11.5 11.0 0.74 65 212 10.3 9.25 0.63 100 150 9.3 7.78 0.54 150 106 8.4 6.54 0.46 200 75 7.5 5.50 0.40 4.62 0.34 EQUIVALENT % FINER 3.89 0.29 DIAMETER dim) 3.27 0.24 26 5.2 2.75 0.20 17 4.4 2.31 0.16 HYDROMETER 10 3.3 1.94 0.13 RESULTS 7 2.7 1.64 0.09 5 2.3 1.38 0.06 3 1.6 1.16 0.03 1 1.4 0.97 0.01 0.82 0.00 [SPECIFIC GRAVITY
BB\123WnctbNW4-1b 6/29/92 TABLE 4-1, cooTd PARTICLE SIZE TESTINO RESULTS ZINC SLAG PILE (HSS104)
SEIVE ANALYSIS MICROTRAC ANALYSIS SEIVE NO. SEIVE OPENING, mm % PASSING EQUIVALENT % FINER DIAMETER (pm) 6" 152.4 100.0 704.0 2.40 4" 101.6 100.0 592.0 2.37 3" 76.2 97.0 497.8 2.33 2" 50.8 92.2 418.6 2.26 1" 26.5 81.1 352.0 2.17 1/2' 13.2 72.5 296.0 2.04 3M 6.70 60.6 248.9 1.88 4 4.75 59.4 209.3 1.71 6 3.35 . 32.5 176.0 1.53 8 2.36 9.9 148.0 1.35 10 1.70 8.1 124.5 1.18 14 1.18 6.3 104.7 1.02 20 0.850 5.1 88.0 0.87 28 0.600 4.0 74.0 0.73 35 0.425 3.1 62.2 0.61 48 0.300 2.4 52.3 0.50 65 0.212 1.9 44.0 0.41 37.0 0.33 HYDROMETER ANALYSIS 31.1 0.26 26.2 0.21 SEIVE NO. SEIVE OPENING, pm % PASSING 22.0 0.17 18.5 0.14 10 1700 8.1 15.6 0.11 35 425 4.3 13.1 0.09 48 300 3.5 11.0 0.08 65 212 2.9 9.25 0.06 100 150 2.4 7.78 0.05 150 106 2.0 6.54 0.04 200 75 1.6 5.50 0.03 4.62 0.02 EQUIVALENT % FINER 3.89 0.01 DIAMETER Cim) 3.27 0.01 32 0.5 2.75 0.00 21 0.4 HYDROMETER 12 0.4 RESULTS 9 0.3 6 0.2 3 0.2 1 0.1 [SPECIFIC GRAvrnr 3.0
BB\123tfnctblsttbl4-1c 6/29/92 4.3.1 Particle Size Particle size distributions of the zinc slag samples were determined by sieve, hydrometer, and Microtrac analyses. The specific gravity of the less than No. 10 mesh, or 1.7 mm, portion of the sample was also evaluated. The results of the particle-size analyses for the zinc slag samples are presented in Table 4-1. The results indicate 90 percent or more of three samples which consisted of material between screen sizes 0.212 mm and 3 inches. Only 60 percent of the other zinc slag sample (HSS102) was material between 0.212 mm and 3 inches. This finer sample was obtained from the north side of the higher, welded area (Figure 3-1). The results of all three particle size determination techniques - Microtrac, sieve and hydrometer ~ compare well. The particle size data was analyzed in order to determine the potentially inspirable (inhalable) and respirable (capable of being deposited in the alveoli) weight fraction of the zinc slag sample. According to Threshold Limit Values given by the American Conference of Governmental Industrial Hygienists (ACGIH, 1990), inspirable particulate mass is calculated based on aerodynamic diameters up to 100 jum and respirable particulate mass is based on aerodynamic diameters of 3.5 jum. The EPA document, Risk Assessment Guidance for Superfund Volume I, Human Health Evaluation Manual (Part A), Interim Final (p. 6-43) (EPA, 1989a) considers respirable particles to be those with diameters of 10 /xm or less. The industrial hygiene reference, The Industrial Environment - Its Evaluation and Control, (NIOSH, 1973) predicts the inhalable particle size based on the known behavior of particles in air suspension and the anatomical arrangement of the connecting tubes in the lung. The reference predicts that particles larger than 10 /nm would be removed from the airstream when passing through the nose and upper airways and that particles between 5 jum and 10 jim in diameter would be deposited mainly in the upper airways on the mucociliary escalator. Only particles in the range of 1 /zm to 2 jum would penetrate to the deeper portions of the lung where deposition in the alveoli may occur. Based on these references, it will be conservatively assumed that particles less than 100 Mm in diameter are potentially inspirable, and those less than 10 /um are potentially respirable. Total suspendable particulates (TSP) are those particles less than 30 The particle size data was analyzed so that the weight percent of material equal to or finer than 100/im, 30/im, and lO/itm in diameter could be calculated. For the hydrometer data, the weight percent of material finer than 30jum and finer than lO^m was linearly interpolated. For the sieve data, the percent of material finer than lOO/xm was linearly
MORRISON KNUOSEN CORPORATION
BB\1893\ZINCRPT\Final-RI 4-3 [Rev 001/13/93) TABLE 4-2
% < 100 jan % < 30 inn % < 10 ion mean mean max mean max Western Zinc D422 6.7 8.9 0.48 4.1 033 Zl Microtrac 0.99 025 5.6 0.070 OJS9 L7
BB\1V9\ZINCRR\W-TMH£4-12 REV 0 interpolated. The Microtrac data provided percent of sample finer than 100 /im, 30 urn, and 10 nm. The minimum, average, and maximum values for the zinc slag samples are presented in Table 4-2. The data show that approximately 7 percent of the material is less than 100 /Ltm, 3 percent is less than 30 pm, and only 1 percent is less than The specific gravity was determined for the less than No. 10 mesh, or 1.7 mm, portion of each of the samples, as required for calculations in the hydrometer test. The specific gravity of this fraction of the zinc slag samples averages 3.25. 4.3.2 Historic and Current Zinc Slag Pile Surface Areas and Volumes The historic volume of the zinc slag pile was estimated based on its size in late 1956. This volume was calculated in order to estimate the amount of slag generated by the smelter. The historic volume was then compared to the current slag pile volume calculated from the survey performed for this RI. (The current topographic surface of the zinc slag pile is shown in Figure 4-1. The historic topographic surface of the pile is shown in Figure 4-2.) The volume decrease between 1956 and 1992 is attributed to the material being removed from the site. The 1956 aerial photographs from which the historical slag pile topography was digitized, are described in Section 3.2.1. Surface topography was digitized in two-foot contour intervals by IntraSearch, Inc. of Englewood, Colorado. AutoCAD software generated the surface of the slag pile. The topography around the perimeter of the slag pile was used to estimate the ground surface before slag deposition. Elevation differences between the two surfaces were used to develop an isopach map, from which the slag pile volume was calculated. The result of this calculation shows that the Western Zinc slag pile volume in 1956 was 35,100 cubic yards. In the spring of 1992, a professional survey team examined the zinc slag pile, according to procedures reported in Section 3.2.2. From this survey information, a topographic map of the pile surface, with five-foot contours, was developed. The current volume of the zinc slag pile was determined using procedures as described for estimating the historic volume in the preceding paragraph. The current volume of the Western Zinc slag pile is 22,600 cubic yards. The pile surface area from a map view perspective, is 201,000 square feet.
MORRISON KNUDSEN CORPORATION
BB\1893\ZINCRPT\Flnal-« 4-4 [Rev 001/13/93] s U 5S nl LEGEND LJ - 2' SURFACE CONTOUR INTERVAL £ ADD 9000' TO CONTOUR INTERVA Ld MONITOR WELL • BOUNDARY OF VOLUME CALCULATION N 515,500 ANGLE OF REPOSE CALCULATION SECTION
SMELTER RUBBLE AREA
N 515,250 VOLUMES BY FLATIRONS SURVEYING, INC. GRID METHOD 21,900Cu. Yds. AVERAGE END AREA METHOD 23,130 Cu. Yds. TIN SUBTRACTION METHOD 22,960 Cu. Yds. SURFACE AREA 201,290 Sq. Ft.
N 515,000
DATUM: DATUM = DATUM 10795.0, 10785.0, 10800.0
N 514,750 6 co ll 50°1 SCALE AVERAGE ANGLE OF REPok = 34.1* FEET SUPERIMPOSEOUTLINE OF D HISTORION CURRENC (1956T ) SURFACPILE E FOR READER COMPARISION CALIFORNIA GULCH CERCLA SITE N 514,500 ZINC SLAG PILE INVESTIGATION LEADVILLE. COLORADO FIGURE 4-1 ZINC SLAG PILE CURRENT SURFACE AREA, VOLUME AND ANGLES OF REPOSE DENVER & DENVERRIO GRAND, COLORADE WESTERON RAILROAD IMORRISON-KNUDSEN CORPORATION FILE NAME (CM)) 1893N048 |DATE:6/02/92 PROJECT SUFTIX TASK DRAWING NUMBER REV.
N 515,500 VOLUME CALCULATION I Method of Calculation:.... QuickSurf Grid Size:...... 10' X 10'
35,100 Cubic Yards
N 519,250
N 515,000
N 514,750
SCALFEETE 0 50 100 150 2QO
TOPOGRAPHY DIGITIZED FROM 1956 AERIAL N 314,300 PHOTOGRAPHY BY INTRASEARCH. INC. CALIFORNIA GULCH CERCLA SITE ZINC SLAG PILE INVESTIGATION LEADVILLE. COLORADO______ZINFIGURC SLAG PILE 4-E2 HISTORIC VOLUME DENVER & DENVERRIO GRANO, COLORADE WESTERON RAILROAD IMORRISON-KNUDSEN CORPORATION rill N«Mt JC«D) 1893NQ20 IDMI3/17/9? PROJECT SUFTIX DRAWING NUMBER RCV.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Flnal-RI 4-6 [Rev 001/13/93] testing has been done on zinc slag or slag-like material. Material considered in the literature search included slag, igneous rocks, natural glasses and vitrified waste. The disintegration of rock due to pressure exerted by water freezing in cracks and pores is called congelifraction. When water freezes under atmospheric conditions, its molecules organize into a rigid hexagonal crystalline network, and it increases nine percent in specific volume. As ice expands, the pressure of the remaining water increases, and the temperature must be lowered further in order to continue this increase in pressure. Ice is not strong enough to seal water into a fracture and produce the maximum possible pressure, as the plastic deformation of ice is so rapid that water is quickly extruded (Bloom, 1978). Water in very thin cracks will not freeze, even at very low temperatures, because of the strong capillary adhesion of the water to rock. Most of the rock fractures attributed to freezing are probably due to capillary or monomolecular films of unfrozen water that spread along pre-existing cracks in rocks. Thin films of water form a semicrystalline "ordered" molecular structure on mineral surfaces that can pry apart microfractures and propagate cracks. Shallow freezing may aid in forcing capillary films of water deeper along tight joints and pre-existing microfractures, thereby hydrofracturing rocks well below the depth of actual freezing (Bloom, 1978). Based on the literature review, freeze/thaw cycling may have some effect on zinc slag. Small surface vugs of the zinc slag may fill with water that subsequently freezes. Recurrent freeze-and-thaw action in the slag surface layer could loosen zinc slag fragments, causing eventual breakdown of the material to finer particles. 4.5 Chemical Characteristics of Zinc Slag Material The chemical characteristics of the zinc slag material, as determined by the analytical program outlined in the SAP and discussed in earlier sections, are presented in this section. Chemical analyses included total compositional analysis, Synthetic Precipitation Leaching Procedure (SPLP) analysis, and column leaching tests with analysis of the effluent. Compositional analyses included the analyses of the TAL metals (minus mercury plus silicon), water soluble anions, neutralization potential, sulfur forms and cation exchange capacity. SPLP and column leach eluate were analyzed for anions and TAL metals (minus mercury plus silicon).
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 4-7 [Rev 001/13/83] TABLE 4-3
FREQUENCY OF OCCURRENCE OF TAL METALS — ZINC SLAG Number of Number of RANGE OF DETECTED CONCENTRATIONS Chemical Name Detections Analyses Minimum Value (mg/kg) Maximum Value (mg/kg) Aluminum, total 4 4 21100.00 HSS102MOO 22900 HSS101MOO Antimony, total 3 4 5.30 HSS102MOO 52.2 HSS101MOO Arsenic, total 4 4 112.00 HSS104MOO 414 HSS101MOO Barium, total 4 4 782.00 HSS104MOO 1420 HSS101MOO Beryllium, total 4 4 1.40 HSS104MOO 2 HSS101MOO Cadmium, total 4 4 2.50 HSS103MOO 29.5 HSS101MOO Calcium, total 4 4 12500.00 HSS101MOO 42200 HSS103MOO Chromium, total 4 4 35.90 HSS101MOO 700 HSS102MOO Cobalt, total 4 • 4 9.90 HSS104MOO 19.8 HSS102MOO Copper, total 4 4 125.00 HSS103MOO 3310 HSS102MOO Iron III, total 4 4 108000.00 HSS104MOO 198000 HSS102MOO Lead, total 4 4 192.00 HSS103MOO 925 HSS102MOO Magnesium, total 4 4 6570.00 HSS101MOO 18800 HSS103MOO Manganese, total 4 4 51600.00 HSS101MOO 76500 HSS104MOO Nickel, total 4 4 41.90 HSS104MOO 392 HSS102MOO Potassium, total 4 4 5510.00 HSS102MOO 7690 HSS103MOO Selenium, total 0 4 N/A N/A Silicon, Total 4 4 134000.00 HSS102MOO 154000 MSS103MOO Sodium, total 4 4 604.00 HSS104MOO 1010 HSS103MOO Vanadium, total 4 4 44.50 MSS104MOO 58 HSS101MOO Zinc, total 4 4 63200.00 HSS101MOO 70000 HSS103MOO TOTALS 79 84
* . _ *i. i.. t »i-. i 4.5.1 Compositional Analyses All four slag samples from the Western Zinc Smelter area were submitted to the compositional analysis program. 4.5.1.1 TAL Metals Target Analyte List (TAL) metals were analyzed following digestion by a U.S. Bureau of Mines method as the preparatory technique (Bureau of Mines, 1980). After digestion, most metals analyses were conducted by Inductively Coupled Plasma (ICP) techniques, although some of the metals were analyzed by graphite furnace atomic absorption (GFAA) methods. The elements analyzed by GFAA include arsenic, cadmium, lead and selenium. The use of GFAA was necessitated by matrix interference problems caused by the particular digestion fluid used. Table 4-3 presents the frequency of occurrence of the elements, along with the minimum and maximum values of each of the elements. Iron and silicon comprise the majority of the slag matrix. Iron ranges from 10.8 to 19.8 percent of the zinc slag material, while silicon ranges from 13.4 to 15.4 percent. Manganese values ranged from 5.2 to 7.7 percent. The concentration range and geometric mean of each of four primary elements of concern in zinc slag at the California Gulch site are as follows: - Arsenic-112 to 414 mg/kg, mean 211 mg/kg - Cadmium-2.5 to 29.5 mg/kg, mean 14.1 mg/kg - Lead-192 to 925 mg/kg, mean 568 mg/kg - Zinc-63,200 to 70,000 mg/kg, mean 66,000 mg/kg 4.5.1.2 Anions Water-soluble anions chloride, sulfate, and nitrate/nitrite were analyzed in the zinc slag samples. Although carbonate was not directly measured in the water-soluble extracts, its concentration was calculated from the neutralization potential results, which are reported as total calcium carbonate. The anions are reported in solid units, mg/kg, by back- calculation from the analyses conducted in the water-soluble extract. The most prevalent anion in the zinc slag is the carbonate anion with a mean of 79,200 mg/kg as CaCO or about 8 percent of the total mass of the material. The range of concentrations of3 carbonate is from 58,800 to 100,200 mg/kg. The second most prevalent water-soluble anion is sulfate. Ranges and means for the anions are listed below:
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRFT\Final-RI 4-8 [Rev 001/13/93) TABLE 4-4
Acid Generation Net Acid Neutralization Potential due to Forming Sample ID Potential Pyritic Sulfur Potential HSS101MOO Zinc Slag 125 0.30 -124.70 HSS102MOO Zinc Slag 149 1.30 -147.70 HSS103MOO Zinc Slag 98 0.30 -97.70 HSS104MOO Zinc Slag 167 0.60 -166.40
zinctb!s\tbW-4 6/29/92 - Sulfate - 1,463 to 13,040 mg/kg, mean 4,099 mg/kg - Chloride - 2.3 to 20.8 mg/kg, detected 2 times out of 4 - Nitrate - 5.8 to 45.4 mg/kg, mean 20.5 mg/kg - Nitrite - < 1.0 to 2.1 mg/kg, detected 1 time out of 4 4.5.1.3 Sulfur Forms Sulfur forms were determined by EPA Method 3.2.4 and 3.2.6 (EPA, 1978) for input to calculations of acid-base accounting. Total sulfur is comprised of pyritic sulfur, sulfate, and other non-extractable sulfur forms. The mean concentration for total sulfur is 0.41 percent, with sulfate sulfur the largest fraction by weight of total sulfur. The following provides a breakdown of the sulfur form concentration ranges: - Total sulfur--0.34 to 0.55%, mean 0.41% - Sulfate sulfur-0.01 to 0.54%, mean 0.13% - Pyritic sulfur-0.01 to 0.04%, mean 0.012% - Non-extractable sulfur~0.03 to 0.22%, mean 0.10% Evaluation of the results for pyritic sulfur versus total sulfur indicate that pyritic sulfur averages 9.9 percent of total sulfur for all of the slag samples collected. The geometric mean for pyritic sulfur was calculated using non-detect values as one half of the quantitation limit. For use in acid-base accounting, the percent of pyritic sulfur is converted to units of tons of CaCO3 equivalents per 1000 tons of material (t/kt) by multiplying by 31.25, yielding potential acidity. The potential acidity due to pyritic sulfur is presented in Table 4-4. The geometric mean potential acidity due to pyritic sulfur for the zinc slag samples is 0.5 t/kt. These values indicate that the zinc slag has a low potential for acid generation due to the low levels of pyritic sulfur. 4.5.1.4 Neutralization Potential and Acid-Base Accounting Neutralization Potential (NP) was measured by EPA Method 3.2.3 (EPA, 1978) and reported in units of tons of CaCO3 per 1000 tons of material (t/kt). These values are presented in Table 4-4. The NP for the zinc slag material showed that it has a mean neutralization potential of 132 t/kt, ranging from 98 to 167 t/kt. Acid-base accounting is a technique developed for identifying potentially toxic acidity levels of pyritic materials in surface mining overburden. The weathering of pyritic overburden materials can produce acid over time, thereby lowering the pH and creating an environment conducive to leaching metals. The net acid-base account of a mine overburden is defined MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-Rt 4-9 [Rev 0 01/13/93] as its maximum potential acidity minus its neutralization potential, with both expressed in units of tons calcium carbonate (CaCO3) equivalents per 1000 tons of material. Potential acidity is equivalent to the amount of acidity that can be generated from sulfur compounds (generally sulfide) and is calculated using the measured pyritic sulfur values. Neutralization potential is the buffering capacity of the material. The difference between potential acidity and neutralization potential is net acid generation potential. Each of these values for the slag samples are presented in Table 4-4. According to Mine Spoil Potential for Soil and Water Quality (EPA, 1974), page 128, "From the acid-base account, potentially toxic material is defined as a rock or earth material having a net potential deficiency of 5.0 tons of calcium carbonate equivalent or more per 1,000 tons of material." A net acid-forming potential less than 5.0 t/kt indicates excess neutralization potential in relation to the potential acid generation. All zinc samples showed a net acid-forming potential less than 5.0; the geometric mean was -132 t/kt. Thus, the slag sampled is not potentially acid toxic due to acid generation potential. 4.5.1.5 Cation Exchange Properties Cation Exchange Capacity (CEC) is a measure of how readily a material will sorb cations onto its surface or into its matrix. The CEC was measured using EPA method 9080 (EPA, 1986), in which results are expressed in milliequivalents (meq) per 100 grams of material. The material tested has a low CEC, with values of 2.0, 4.9, 5.9 and 15.2 meq/lOOg. The CEC results for the four zinc slag samples show a geometric mean of 5.4 mg/lOOg. 4.5.2 Leaching Analyses Two types of leaching tests were performed on zinc slag. One method, the Synthetic Precipitation Leach Procedure (SPLP) is a liquid shake extraction test developed to simulate leaching of mine waste impacted by acidic precipitation. The other test is a laboratory column leach test designed to simulate percolation of precipitation through the material. 4.5.2.1 Synthetic Precipitation Leaching Procedure The SPLP (EPA Method 1312) was conducted on each of the zinc slag samples collected. The sample size was increased to 1 kilogram rather than the 100 gram sample specified by the method to avoid particle size reduction. Particle size reduction to less than 9.5mm, as called for in the method, was not conducted on these samples so as to mimic in-situ conditions of the piles as closely as possible. MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 4-10 [Rev 001/13/93] The SPLP method calls for comparisons of eluate concentrations to applicable regulatory thresholds, but does not state what these thresholds are. Because the test most closely resembles the TCLP or EP toxicity tests, regulatory thresholds associated with these tests were utilized. The results for all elements for all zinc slag samples were below the toxicity characteristic criteria listed in 40 CFR 261.24. The maximum value for each of the eight metals for which toxicity characteristic criteria exist was generally more than two orders of magnitude lower than the criterion. The exception to this is manganese, which was more than one order of magnitude lower. The following summary compares the mean and maximum values of the leachate to the toxicity criteria or 100 times the secondary drinking water standards: Element Toxicity Criteria Mean Value Maxinum Value Arsenic 5.0 mg/1 0.030 mg/1 0.051 mg/1 Barium 100 mg/1 0.084 mg/1 0.141 mg/1 Cadmium 1.0 mg/1 0.002 mg/1 0.006 mg/1 Zinc 500 mg/1* 0.063 mg/1 1.04 mg/1 Manganese 5.0 mg/1* 0.016 mg/1 0.141 mg/1 Iron 30 mg/1* 0.010 mg/1 0.022 mg/1 100 times secondary drinking-water standards. Chromium, copper, lead, selenium and silver values were below detection limits for all four samples. The geometric means for arsenic, cadmium and iron were calculated using non- detect values (2 of 4 for iron and 1 of 4 for arsenic and cadmium) as one half the quantitation limit. 4.5.2.2 Column Leach Studies Column leach testing was conducted on one zinc slag sample. The material in the column was subjected to one-hour leaching cycles, each representing a one-inch rainfall event. The column criteria were as follows: Test Mode Column Volume of Material Diameter (in.) one-inch of rainfall) Zinc Slag Downflow 8 823 The lixiviant used for the column leach testing was the simulated precipitation for areas west of the Mississippi, as specified in Method 1312 of SW-846. The precipitation fluid is made by adding a 60/40 weight percent mixture of sulfuric and nitric acids to deionized water until the pH is 5.00 ±0.05 units. The fluid was prepared in a 55-gallon polyethylene drum by adding approximately 2 ml of the acid mixture to 50 gallons of deionized water and mixing. Due to the lack of buffering capacity in the water, the pH dropped to about 4.5 and
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 4-11 [Rev 001/13/93] was readjusted to pH 5.00 ±0.05 by the dropwise addition of 10 percent sodium hydroxide (NaOH). The simulated precipitation was introduced to the column over a one-hour interval, followed by a one-hour desaturation/aeration period during which the lixiviant was allowed to drain from the test material. The tests took place over a period of two hundred hours, corresponding to one hundred rainfall events. Considering that Leadville receives about twelve and one half inches of rainfall per year the column leach test cycles corresponded to eight years of rainfall. The following table presents loading data for the zinc-slag column: Test Weight Packed Total Pore Material Materialfg) Lengthfiiri Volfmn VcKmft Zinc Slag 8,813 19 15,642 3,800 Effluent was collected from each of the precipitation events. Upon collection, pH, Eh, and conductance measurements were made using calibrated probes connected to pH/mv and conductance meters. After these measurements were completed, the sample was filtered through Whatman #40 (S^m) filter paper. The samples was split into two separate containers; one for anions analysis and the other for metals analysis. The samples for metals analysis were preserved with nitric acid to a pH less than 2.0. At the completion of one hundred cycles, the pore volume of the column was determined. This measurement was made by pumping water to the top of the test material and then measuring the volume of water collected as the water level was lowered to the bottom of the test material. Table 4-5 summarizes the analytical results for selected metals and anions from the column leach test. Figures 4-3 and 4-4 depict in graphical form the concentrations of selected metals and anions as a function of effluent number (precipitation event). The complete results of the column leach testing are presented in Appendix Bl.
4.6 Analytical Data Validation Data validation was performed on 100 percent of the analytical data reported by the laboratory. CLP methods were evaluated using accepted criteria and control limits defined
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 4-12 [Rev 0 01/13/93] TABLE 4-5
Leaching Lead Cadmium Arsenic Zinc Bicarbonate SuKate Event # ug/l ug/l ug/l ug/l mg/l mg/l 5 31 u 141 49u 31500 29.2 1742 25 31 u 126 49u 26200 13.1 1479 50 41.9 76.5 49u 13900 14.1 1079 75 31 u 42.2 49u 7200 100 44 20.1 53.6 3680 14.7 428.7 u - non-detect — - not analyzed
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MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-RI 4-13 [Rev 001/13/93] 4.6.1 CLP Data Validation The following data quality issues were addressed in the data validation and review process for CLP analyses. Field and Transportation OA/OC Documentation was reviewed to verify that uninterrupted chain-of-custody protocol was followed and reported in a manner consistent with the SOW criteria. Holding Times As stated previously, a listing of sampling date, laboratory receipt date, and analysis date was prepared and summarized for each sample in the SDG and reported in Appendix El. The time elapsed between the sampling and analysis dates was compared with holding time criteria required by the SOW. A general summary of holding time compliance is provided in the text of the report. Initial and Continuing Calibration Verification Start-up calibration records generated by the laboratory were reviewed and validated to demonstrate that the instruments were capable of producing acceptable quantitative data. Continuing Calibration and Preparation Blanks Blank data was assessed to determine the existence and magnitude of any contamination that may have been introduced during the calibration or sample preparation process. Interference Check Sample Interference check sample results were reviewed to verify that instrument inter-element and background correction factors were correct. Spiked Sample Recoveries Spiked sample results were reviewed to evaluate the accuracy of sample results and to evaluate the effect each sample matrix had on the digestion and measurement methodology. Data qualifiers applied by the laboratory were reviewed to ensure they were correctly applied and reported. Graphite Furnace-Atomic Absorption Spectroscopy (GFAA) Duplicates Duplicate injections consisting of sample and spiked-sample are required for GFAA analysis. Duplicate analysis is performed by the laboratory to establish the precision and accuracy of
MORRISON KNUDSEN CORPORATION B8\1883\2INCRPT\Final-R 4-14 [Rev 001/13/93) individual analytical determinations. Duplicate recoveries presented by the laboratory were recalculated by the reviewer and duplicate values were verified from GFAA raw data to ensure that qualifiers were correctly applied. Duplicate Recoveries Analyses of lab-choice duplicate samples were evaluated to determine the laboratory precision based on the sample matrix. Duplicate recoveries were recalculated and data qualifiers verified. Laboratory Control Sample (LCS) The LCS sample results were verified and evaluated to ensure that overall analytical and preparation performance in the laboratory were adequate. Method of Standard Additions (MSA^ Results MSA is required for quantification of analytes determined by GFAA that do not meet spike recovery criteria. Spike recovery data were reviewed to determine if MSA was correctly applied, as needed. Statistical variance of the MSA results was evaluated to determine if the data were useable without qualification. Inductively Coupled Plasma (IPC) Spectrophotometry Serial Dilution Serial dilution is required to determine whether significant physical or chemical interferences existed due to sample matrix. Results for high concentration analytes were reviewed to ensure serial dilution results were correctly calculated and qualified, as required. 4.6.2 Non-CLP Data Validation The following data quality issues were addressed in the data validation and review process for non-CLP analyses. Holding Times A listing of sampling date, laboratory receipt date, and analysis date was prepared for each sample in the SDG (Appendix El). The time elapsed between the sampling and analysis dates was compared with holding time criteria required by 40 CFR 136, if applicable. A general summary of holding time compliance by the laboratory for each analytical method is presented in the SDG report.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-« 4-15 [Rev 001/13/93] Standard OA/OC for Individual Analytes or Methods The applicability of QA/QC analysis provided by the laboratory was compared to method specific or industry accepted standards as required. Control limits specified for CLP analysis of standards, duplicates and spikes were generally applied to non-CLP methods.
MORRISON KNUDSEN CORPORATION B8\1893\ZINCRPT\Rn«l-RI 4-16 [Rev 0 01/13/93) 5.0 INTERPRETATION OF RESULTS The following section of this RI report presents the interpretation of results developed from zinc slag sample collection and analyses activities. The release mechanisms of primary concern investigated during the Zinc Slag Pile RI were leaching, wind erosion, runoff of slag particles, and transport by human activities. (Direct contact has been discounted as a release mechanism for slag piles in EPA's Preliminary Baseline Human Health Risk Assessment [EPA. 1991a]). The environmental media potentially impacted by these release mechanisms are water, soil, and air. As data are obtained from the speciation and other site-related programs additional data analyses of potential release mechanisms and impacts as they relate to zinc slag may be performed. If this additional data affects interpretations, an addendum to the RI report will be prepared. 5.1 Statistics Statistical analyses were used to determine relationships between elemental metal concentrations in zinc slag samples and those concentrations in the population of all slag samples. The statistical procedures were performed on total compositional results of the four primary elements of concern (lead, arsenic, cadmium and zinc), as well as key elements of the slag matrix (e.g., aluminum, calcium, copper, iron, manganese and silicon). The zinc slag data set consisted of the four samples collected from the Western Zinc slag pile. The types of statistical methods are described in Section 5.1.1, and the results are presented in Section 5.1.2. 5.1.1 Methodology The types of statistical procedures included the following: - Summary Statistics - Cumulative Distribution Functions - Histograms - Analysis of Variance - Cumulative Probability Plots - Correlation Analysis
MORBISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-RI 5-1 [Rev 0 01/13/93) Statistical analyses were performed on the discrete zinc slag data set as well as on the lead slag data sets, for comparative purposes. Summary statistics compiled for each of the data sets include the range, average, geometric mean, minimum and maximum. The following table lists the data sets utilized and the number of samples in each of the data sets: Arkansas Valley (AV) Water-Quenched Fines 4 AV Sorted Fines 4 AV Air-Cooled 6* AV Ballast-Sized 4 AV Old Slag 2 Harrison Surface 4 Harrison Old Slag 2 La Plata Surface 5** La Plata Old Slag 3** Evans Gulch/Georgia Gulch 4 Western Zinc Slag 4 Subslag Material 1 9 'includes two duplicate samples **includes an additional sample collected for column leaching tests 5.12 Statistical Results The results of the statistical analyses confirm that the constituents within the slag samples are log-normally distributed; therefore, geometric means have been used to report results. Lognormality was determined from the data set containing all slag samples (42 samples), not from individual data subsets. The individual subsets were assumed to be lognormal based on the observation that the entire data set is lognormal. The following discussion is based on summary statistics, analyses of variance, and cumulative distribution functions. Arsenic Arsenic was detected in each of the slag samples analyzed. The range of concentrations varies from 9.9 to 2,160 mg/kg. The geometric mean of all slag samples analyzed is 217 mg/kg. The zinc data set has a geometric mean of 211 mg/kg, which is not significantly different than the data set as a whole.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 5-2 [Rev 0 01/13/93) Cadmium Cadmium was detected in 33 of the 42 slag samples analyzed, which is about 79 percent of the samples. The range of detected values varies from a low of 2.5 mg/kg to a high of 37 mg/kg. The mean of all concentrations is 4.93 mg/kg. Because of the narrow range of values for cadmium, no discernable difference in populations can be seen from the data, although the zinc samples are among the highest concentrations with a mean of 14.1 mg/kg. Lead Total lead was detected in each of the 42 slag samples analyzed. The concentrations of total lead ranged from a low of 192 mg/kg to a high of 30,200 mg/kg, or 3 percent lead. The geometric mean of the samples was 6,660 mg/kg. The Western Zinc pile showed the lowest mean concentrations for total lead at 568 mg/kg, ranging from 192 to 925 mg/kg. Zinc Zinc was detected in all 42 of the slag samples analyzed, ranging from 9,800 to 77,300 mg/kg. The mean of the values is 38,600 mg/kg. The zinc slag pile data set showed the highest mean concentration of 66,000 mg/kg. Calcium Calcium was detected in all of the 42 slag samples analyzed, with a range of concentration from 12,500 to 145,000 mg/kg. The mean of all slag samples is 83,000 mg/kg. The mean concentration of the zinc pile is distinctly lower than other piles, at 19,100 mg/kg. Copper Copper was detected in each of the 42 slag samples submitted for analysis, with a range of 125 to 3,310 mg/kg. The geometric mean of the copper values is 1,390 mg/kg. The mean value of the zinc slag is 570 mg/kg. Iron Total iron, detected in each of the samples, ranges from 10.8 to 33.2 percent of the slag matrix. The mean value is 23.8 percent, indicating that iron is a major constituent of the slag. The Western Zinc slag with a mean of 15.7 percent, is lower in iron than other data sets.
MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Flnal-RI 5~3 (Rev 001/13/93] Manganese Manganese, also detected in each of the 42 slag samples analyzed, ranges from a low of 4,850 to a maximum of 76,500 mg/kg. The mean of all values is 19,000 mg/kg. The mean concentration of the Western Zinc samples, 58,400 mg/kg, is elevated with respect to the other slag samples. Iicon Silicon was detected in each of the 42 slag samples collected, with total concentration values ranging from 101,000 to 154,000 mg/kg or 10 to 15 percent. The geometric mean of all samples is 130,000 mg/kg. The data is relatively uniform with means for all of the data sets between 108,000 and 141,750 mg/kg. The geometric mean for the Western Zinc samples is 14.2%. 5.1.3 Cumulative Probability Plots Cumulative probability plotting is a method used to display the data in a way that will identify the various populations within a data set. A normal cumulative probability plot consists of an arithmetic horizontal axis and a cumulative probability vertical axis scaled so that the distribution function will plot as a straight line. A change in slope between linear segments of a distribution of values represents different populations. Plots of the concentrations of each element analyzed in the slag and subslag samples are provided in Appendix C, as are rank correlation analysis backup data. From these plots, the ranges of concentrations representing various populations were identified. The ranges of concentrations assigned to these populations are summarized in Table 5-1; the population to which each concentration value belongs is indicated in Tables 5-2, 5-3 and 5-4. As the data plotted were not transformed prior to generating cumulative probability plots, breaks in the slope of the lines but do not have significance other than they appear to represent different populations. Relationships between different elements were not evident from the collected data. That is, if a certain set of samples were grouped in a given population for one element, a second element for that set of samples would also be expected to fall into a like population grouping. Upon examination of the data, these correlations were not evident and this analysis was not carried further. Therefore, the populations are designed only to provide groupings of data in four distinct sets for each element. Certain elements, based upon the cumulative probability plots, did not appear to
MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Flnal-RI 5-4 (Rev 0 01/13/93] TABLES-1. Concentration Ranges of Populations for Analyses of Slag Determined from Cumulative Probability Plots in Appendix E. Population 1 Population 2 Population 3 Population 4 Element min max min max min max min max Aluminum, mg/kg 13,100 20,700 21,100 25,300 30,900 63,400 - - Calcium, mg/kg 1,970 18,900 42,200 83,800 92,800 117,000 121,000 145,000 Chloride, mg/kg <1 4 8 20.8 39 39 - - Iron, mg/kg 14,000 33,000 108,000 220,000 226,000 251,000 260,000 332,000 Magnesium, mg/kg 1,900 4,900 5,700 7,900 8,500 19,000 24,000 32,000 Manganese, mg/kg 650 1,900 2,500 10,000 11,000 26,000 30,000 76,500 Nitrate, mg/kg <1 9 20 20 22.7 45.4 - - Nitrite, mg/kg <1 4 ------Potassium, mg/kg 3,000 3,700 4,400 9,100 18,000 22,000 24,000 28,000 Silicon, mg/kg 100,000 113,000 121,000 139,000 142,000 154,000 169,000 211,000 Sodium, mg/kg 170 1010 1,050 2,100 5,100 8,900 13,800 13,800 Sulfete, mg/kg 29 82 132 480 508 880 1,000 13,040
Antimony, mg/kg. <5 31 46 99 108 197 243 842 Arsenic, mg/kg <4 55 112 414 427 549 842 2,160 Barium, mg/kg 346 782 917 1,880 2,070 2,870 3,480 4,950 Beryllium, mg/kg 0.3 0.97 1.0 1.3 1.4 2.0 3.4 3.4 Cadmium, mg/kg <0.4 <0.4 2 13 14 18 18.9 37 Chromium, mg/kg 6 44.3 45 81 132 684 943 1,210 Cobalt, mg/kg <0.8 4.9 7.2 41.1 62.6 75.4 - - Copper, mg/kg 21 137 261 602 768 1,730 1,940 3,310 Table 5-1, Page 2 of 2 Population 1 Population 2 Population 3 Population 4 Element min max min max min max min max Lead, mg/kg 85 925 1,590 2,650 7,580 12,000 12,700 30,200 Nickel, mg/kg <3 3.3 3.7 8.5 10.2 55.6 190 587 Selenium, mg/kg <2 11.2 44 94 - - - - Vanadium, mg/kg 8 40 44.5 103 117 290 461 461 Zinc, mg/kg 188 1,290 9,800 33,900 37,200 55,400 63,200 77,300
Acid Gen.1 <0.3 <0.3 0.6 3 4.7 10 13 19 Cat. Ex.2 0.4 1.4 1.8 5.9 6.1 15.2 24.1 24.1 Neutral.' <1 84 98 300 330 350 400 450 S/Pyrite, % <0.01 0.01 0.02 0.09 0.15 0.32 0.42 0.60 S/Sulfate, % <0.01 0.02 0.19 0.8 0.8 1.4 1.6 1.7 S/Non-Ext., % <0.01 0.30 0.50 0.75 0.78 1.2 1.6 2.0 S/Total, % <0.01 0.04 0.34 2.0 2.1 2.7 3.9 3.9
1 Acid Generation Potential in units of tons CaCO, equivalents per 1000 tons of material 2 Cation Exchange Capacity in units of milliequivalents per 100 grams 1 Neutralization Potential in units of tons CaCO3 equivalents per 1000 tons of material TABLE 5-2. Major Constituents (ing/kg), in Slag and Subsoils with Values Assigned to Concentration Range Populations- as indicated by Boxes and Shading { Population 2
SAMPLE Al Ca O FcIII Mg MB (as NO3) (as NOZ) SI Na AVO101MOO 18,000 5.20 AV0102MOO 3.00 AVS101MOO 120 AVS102MOO 230 AVS103MOO 120 AVS109MOO 100 AVS104MOO 100 AVS105MOO 1.90 AVS106MOO 1.90 AVS10BMOO 1.80 AVS110MOO 110 AVS112MOO 1.80 AVS113MOO 100 AVS116MOO 1.90 AVS107MOO 110 AVS111MOO 1.90 AVS111MOOD 1.80 AVS1HMOO 170 AVS115MOO 3.10 AVS11SMOOD 180 Table 5-2, Page 2 of 3
SAMPLE Al (as N03) (as NO2) K SI Na SO4 HRO1Q5MOO 1.80 <1.00 ! 4,790 ! 123,000 \ 538 } 384.00 HR0106MOO 140 <1.00 S} 5,095,0900 SS 121,00121,0000 SS 888844 {{ 293.00 HRSIOIMOO 120 IM i 4,744,7400 !! 131,00131,0000 \! 878777 Ji -»" 1______"I————————5 ,,_____ * .._._.« - —-----_IM[*. HRSIOIMOO 160 <1.00 i 4mn ! iran108,00m0 .+————-I : : : : ; : : : : : : ; ; ; : : : ; : : : : : : HRS103MOO 100 <1.00 i 4,4604,460 ! 123,000 | : : : : : : : : : : : : : : : : W::!::::S:ttv:v:A:::::::::::::::::::*x::5:::::: HRS104MOO <1.00 ! 5^30 ) 109,000 577 l;;||||w|i^|ll
LPCOLUMNl <1.00 3,610 \ 137,000 S 232 LmmmmmmmmmmJ LFCOLUMN2 <1.00 3,040 i 132,000 j i" LPOIOSMOO <1.00 ! 5,620 { LPO106MOO <1.00 LPS101MOO LPS102MOO LPS103MOO LPS104MOO
OOS101MOO LES101MOO i 21,900 ! 78,100 i MBS101MOO UES101MOO 1^ 22^00 ! 68,900 j Table 5-2, Page 3 of 3 (as NO3) (as NO2) AVB101T14 AVB102T17 AVB103T145 AVB104T19 HRB101T10 HRB102T10 HRB103T23 LPB101T34 LFB1021305 LPB1Q31377 HSSIOIMOO HSS102MOO HSS103MOO HSS104MOO TABLE 5-3. Trace Metals (mg/kg), in Slag and Subsoils with Values Assigned to Concentration Range Populations, as Indicated by Boxes and Shading Population 1 { Population 2
AVO101MOO J r 440 ! AVO102MOO • r ™ ™™ ™™~~ -1——————, 1Z.CHW , AVS101MOO I A AA I AVS102MOO AVS103MOO AV5109MOO AVS104MOO AVS105MOO AVS106MOO AVS10SMOO AVS110MOO AVS112MOO AVS113MOO AVS116MOO I 1,530 I AVS107MOO AVS111MOO AVS111MOOD AVS114MOO AVS11SMOO AVS115MOOD Table 5-3, Page 2 of 3 SAMPLE Sb Aa Co Co Pb Nl Se Zn
HR0105MOO . 5770 HR0106MOO | »w~r~MJOO~T~i«"~ HRS101MOO 7i90 ! 220.00 969*" HRS102MOO HRS103MOO HRS104MOO
t LPOOLUMN1 I 52^0""] 4.20 45.10 ' "————"T LPGOLUMN2 | """"""" 6.70 S 35.60 LPO105MOO i
LP0106MOO j ww j LFS101MOO
LPS102MOO »mo i «*«w | o.rv | LFS103MOO 7.40 i 61.90 ! 1.30 L j^ ,.lr_t_mj «*™1MOO | 272.00 272.00 1 SSiiSiiiiSiliiii------LES101MOO j ^10 j! 2350,235.00, I 1,410 MBSIOIMOO a*) | uEsioiMoo r"sir"teH moo
H\UM\LBADI»T\IU.TAILB54 RBVO Table 5-3, Page 3 of 3
AVB101T14 AVB102T17 AVBKOTMS AVB1MT19 HRB101T10 HRB102T10 HRB103TI73 LPB101T34
LPB10CT377 HSS101MOO ! HSS102MOO HSS103MOO HSS104MOO
ra\UM\UADIVr\IU-TABLB54 RHV 0 TABLE 5-4. Miscellaneous Measurements in Slag and Subsoils with Values Assigned to Populations, MMHWMWWVas indicate— — —v...... ,...... d by Boxe^s and Shading Population 1 { PopuHUonZ
SAMPLE AGP1 CaEX* NP1 NEx/S4 Py/S* S LPCOLUMN1 LPCOLUMN2 LP010SMOO LPO106MOO LFS101MOO LPS102MOO LPS103MOO LPS104MOO OOS101MOO LES101MOO iiiiiriiriiii'iiiriiia'ffiifc '^jiiiiiiii't'i' iii'i'i' iri'i^iM.'iikiai'iii» MES101MOO I 0.65 5 ]I 1.00 |j ^ J UES101MOO <0.01 ImMmMMMma 0.6M 0 1.19 .__ (._____—_.. M\im\UMIHVIMU-TABLB54. RBV « Table 5-4, Page 3 of 3 AVB101T14 AVB102T17 AVBKOTUS AVBUMT19 HRB101T10 HRD102T10 HRB107T23 LPB101T34 LPB1Q2TM5 LPBUBTI377 HSS101MOO HSS102MOO HSS103MOO HSS104MOO 1 1 Acid Generation Potential (tons of CaCO, equivalents per 1000 tons material) 3 •yiiaCatioi nrin» •Exchang «r»^>nin e Capacity (milliequtvalents per 100 grams) 4 NeutralizatioNeutralizationn roienuaPotentiali ^10(ton1s of CaCO, equivalents per 1000 tons material) 5 Non-Extractablc Sulfur (%) Pyritic Sulfur (%) *7 Sulfatc(%) Total Sulfur •B\im\LEADIVniU-TABLa5-4. REV 0 contain four populations. In these cases, populations were assigned based upon the number of discernable groups of data. Comparison of the major elements shows differences between the zinc slag and the other slag sample data sets (Table 5-2). The differences between slag from the different piles is illustrated by the aluminum, calcium, iron, sulfate, and manganese concentrations. The zinc data set is generally higher in manganese and sulfate and lower in iron, aluminum and calcium when compared to the data sets as a whole. The concentrations of trace metals are generally variable throughout the slag piles (Table 5-3). The Western Zinc data set is low in lead and high in zinc and cadmium when contrasted with the other slag samples. In summary, the Western Zinc samples are higher in manganese, sulfate, zinc and cadmium, and lower in lead, aluminum, iron and calcium when compared to all slag data. 5.1.4 Statistical Summary Information from which the above discussions and conclusions were derived are presented in Appendix C of this report. The log normality of the data is verified through the examination of histograms. The statistical results show that the Western Zinc slag pile differs in certain elements from the slag data set as a whole. 5.2 Potential for Water Quality Impacts Test results showed that the tendency for zinc slag to leach metals to aqueous solutions is minimal, as all eluate concentrations were well below toxic characteristic criteria for the primary metals of concern. However, as with all metals-containing environmental media, some leaching does occur. Calculations were performed to determine the potential metals load from the zinc slag pile, based on the results of the SPLP and column leach tests. Data from the other PRP RI efforts may be used to refine assumptions used in these loading calculations and to evaluate whether the potential loadings represent a significant environmental impact. Calculations were performed for three of the primary elements of concern -- lead, cadmium and zinc. Loading calculations for arsenic, the fourth primary element of concern, were not performed because of the significant number of non-detect results in the analytical data. In the subsection 5.2.3, the SPLP and column leach loading estimates have been combined to develop a best estimate based on the results of both tests and site-specific information. The assumptions and calculation methods used, a tabulation of results, and a discussion MORRISON KNUOSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 5~5 [Rev 001/13/93] concerning the potential for water quality impacts are presented below. Appendix D2 contains the calculation sheets and supporting documentation. Summaries of the leaching test methodologies, as well as the results of the actual tests, were presented earlier in this report. 52.1 Metals Loading Based on SPLP Results The SPLP test (Method 1312) was designed to determine the mobility of metals by simulating the effect of high country precipitation percolating through a mine waste pile. Results of the procedure simulate the buffered, oxygen-depleted conditions in the ulterior of the piles. Annual metals loading from the zinc slag pile (mass per year) was estimated by multiplying the SPLP eluate concentration (in ug/1) by the number of liters of precipitation contacting the zinc slag pile in one year. The following assumptions have been used to estimate annual loading: • The annual precipitation for Leadville is 12.67 inches per year (Res-ASARCO, 1991) • All precipitation infiltrates the pile; runon and runoff were considered to balance out and evaporation/sublimation was not considered No ground water flows into the piles to interact with percolating water Precipitation percolates through the pile, achieving a metals concentration represented by the eluate chemical concentrations, and exits the pile to the California Gulch hydrologic system • The metals concentrations are geometric means of the SPLP data Pile surface area is assumed to be the 'footprint* of the pile, calculated from the plan view (Figure 4-1) as 201,000 square feet, and is used for precipitation volume calculations The results of the zinc slag pile loading calculations from SPLP concentrations for lead, cadmium, and zinc are estimated at 0.1, 0.01, and 0.4 kilograms per year, respectively. The SPLP tests are considered to overestimate the actual mass leached under oxygen- deficient conditions for the reasons given below: MORfflSON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 5"6 [Rev 001/13/93] The lixiviant contains none of the carbonate buffer in natural rainfall. The absence of carbonate buffering capacity may intensify leaching, especially in cases where the dominant mineral species are carbonate or sulfide based. The samples are tumbled during the test, allowing the sample material to constantly impact and grind together, potentially generating fresh surfaces for the lixiviant to contact. This does not occur under the relatively static conditions of a slag pile. 522 Metals Loading Based on Column Leach Results A column leach test was performed on a zinc slag sample in order to simulate high country precipitation percolating through the slag pile under unsaturated conditions. Results of this test represent the situation at the surface of the pile. Annual metals loading from the zinc slag pile (mass per year) was estimated by scaling the total mass of leached metal of concern from column leach testing (in ug) to the total mass of the slag pile and the number of years of precipitation represented by the test. The following assumptions, in addition to those stated in the SPLP section above, have been used to estimate annual metals loading: Mass of metal leached from column leach tests • mass leached equaled integration by trapezoidal rule of the eluate concentrations from event 0 to event 100 (i.e., the area under the curve) • event 0 leached 0.0 ug/1 • for values reported as below detection limit, one-half of the detection limit was used Mass of slag pile • mass was calculated based on measured pile volumes, specific gravity and estimated porosity • volume of the slag pile was taken from Figure 4-1 as 35,000 cubic yards • specific gravity of the slag (3.25) was equal to that of the < 10 mesh fraction • slag pile porosity was conservatively estimated at 25% MORRISON KNUOSEN CORPORATION BB\1883\ZlNCRFT\Flnal-Rl 5-7 [Rev 001/13/93) The results of the zinc slag pile loading calculations based on column leach test eluate concentrations for lead, cadmium and zinc are estimated at 0.6, 2, and 380 kilograms per year, respectively. The column leach tests are more aggressive than actual site conditions for several reasons: The IMviant contains none of the carbonate buffer in natural rainfall. The absence of carbonate buffering capacity will likely intensify leaching, especially where the dominant mineral species is carbonate or sulfide based. The sulfuric acid/nitric acid based lixiviant is more aggressive than a carbonic acid-based lixiviant that would be more similar to natural rainfall. The effect of wet and dry cycling during testing simulates the reaeration period that likely occurs near the surface of the slag pile between precipitation events when snow cover is not present. If these results were extrapolated to the slag pile at depth, loading calculations would be overly aggressive because reaeration of the material in the interior of the pile would not likely occur under site conditions. Additionally, in the natural setting, a much longer drying or aeration period is expected rather than equivalent periods of wet and dry. These longer dry cycles are expected to facilitate reformation of oxidation rinds on the particles. The column leach testing performed can also be considered aggressive since results indicated that the slag piles have not reached steady-state leaching conditions in Leadville, as would be assumed from the number of years exposure to atmospheric conditions. The depletion of bicarbonate and sulfate and increasing trends in leached metals concentrations during testing indicated that steady-state conditions, as they likely exist in Leadville, were not completely simulated. If column conditions were similar to expected in situ conditions, the anions would not show a depletion effect or the metals an increasing trend. 5.2.3 Metals Loading Based on Combination of SPLP and Column Leach Results Based on the above discussion, the use of a combination of SPLP and column leach results would provide the best estimate of the annual metals load leached from the zinc slag pile. The column leach results were used to estimate the leaching that occurs in the area of the MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-RI 5"8 [Rev 001/13/93] slag pile where reoxygenation of the slag is likely to occur either by exposure to atmospheric oxygen or oxygenated water. Four feet, a distance that is slightly greater than two times the length of the columns used, has been assumed to represent this zone. The use of this distance is further justified by the observation that the column leach eluate pH approached the SPLP final pH after percolation through the columns. The SPLP results have been used to estimate the quantity of metals that could be leached from any part of a slag pile at depths greater than four feet where the environment is oxygen-deficient. The amount of a given pile greater than or less than four feet thick was estimated from the average thickness, determined by dividing the pile volume by the plan view surface area. Using the combination of SPLP and column leach results, the resulting estimated metals load from the zinc slag pile for lead, cadmium and zinc is 0.5,1.6 and 330 kilograms per year, respectively. These loading estimated may be refined as additional information becomes available. 5.3 Potential for Soil Impacts The results of the reconnaissance of the zinc slag pile showed no significant impact to surface soils in the vicinity of the pile. No evidence of particulate movement off the piles was noted in the field. In addition, air pathway analysis did not indicate the potential for windblown fines to impact soils. Subslag material was not sampled at the zinc slag pile. 5.4 Slag Pile Stability The structural (geotechnical) stability of the zinc slag pile was evaluated during the field reconnaissance task. The pile is generally low, with only a small area of significant height (approximately 15 feet), and exhibits no signs of significant fracturing. Therefore, the pile presents no stability concern. Because of the vesicular nature of the zinc slag, freeze/thaw cycling may have some impact on zinc slag. Some disintegration of the slag may be occurring due to pressure exerted by freezing water in the slag vugs. However, as there does not appear to be significant runoff from the pile or wind erosion, any disintegration does not appear to have an impact on the environment. 5.5 Potential for Air Quality Impacts Analysis of emissions calculations using the 1991 meteorological data from the Colorado Mountain College (Res-ASARCO, 199 la) and the mode of the aggregate size distribution have demonstrated that wind erosion does not occur from the Western Zinc slag pile. This conclusion was reached by following industry-standard procedures and guidance from the MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-R1 5-9 [Rev 001/13/83] EPA regional office in Denver, Colorado (EPA, 1992). The procedures, described in Section 3.4.2, were used to determine the friction velocity (wind speed at the pile surface) and the threshold friction velocity (minimum wind speed at which particles will become airborne). The friction velocity of 0.55 m/sec was then compared to the threshold friction velocity for the zinc slag (1.0 m/sec). A friction velocity lower than the threshold, shows that Leadville wind speeds are not fast enough to cause wind erosion from the pile. The results can be further explained by examining the factors involved in emissions potential. The small silt and clay size fractions, defined as the amount of material that passes through a 200-mesh sieve, have the greatest potential for erosion. In the Western Zinc pile, this fraction is less than 6 percent. This, along with the moderate maximum hourly average wind speed in Leadville, limits the fines' ability to become airborne. An additional factor that was not included in the calculations, but would further limit credibility is the extended periods of snow cover in Leadville. Periods of high moisture and winter snow cover would suppress any potential for fugitive dust emissions. Climatological observations from the Leadville airport indicate that there is a persistent snow cover from November through April. In addition, July and August are typically months of high precipitation (Res-ASARCO, 199 la). The emissions calculations do not take into account any conditions other than those ideal for wind erosion of material. 5.6 Anthropogenic Distribution Distribution of the zinc slag has not been documented; however, a significant volume decrease has occurred over the last several decades. Site reconnaissance showed what appears to be material from the Western Zinc pile on roadways and road shoulders within the site. Zinc slag has not been used by railroads in the Leadville area. MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Final-« 5-10 [Rev 001/13/93) 6.0 SUMMARY AND CONCLUSIONS This section summarizes the findings of the Zinc Slag Pile Remedial Investigation based on the data collected and evaluated to date. Each of these results have been described in greater detail earlier in the RI. 6.1 Summary of Zinc Slag Characteristics The results of the field reconnaissance, physical testing, and analytical testing, as well as impacts to water, soil, and air are summarized below. Physical Characteristics Zinc slag is a highly vesicular material consisting of mostly coarse particle sizes. The fraction of zinc slag passing the 200-mesh sieve is less than 6 percent. For the fine fraction, approximately 7 percent of the material is < 100 /xm and one percent is < 10/xm. The zinc slag pile is generally low, with only a small area of significant height (approximately 15 feet). The zinc slag pile does not present a stability concern. Because of the vesicular nature of the zinc slag, freeze/thaw cycling may have some impact on zinc slag. However, as there does not appear to be significant runoff from the pile or wind erosion, any disintegration does not appear to have an impact on the environment. Chemical Characteristics Iron and silicon compose the majority of the zinc slag material ranging up to 20% and 15% respectively. The geometric mean concentrations of the primary metals of concern are as follows: • Lead-568 mg/kg •Cadmium— 14.1 mgkg •Arsenic-211 mg/kg •Zinc-66,000 mg/kg The mineral species with which these metals are bound (e.g., oxide, sulfide, sulfate) will be determined by other investigators and reported in forthcoming metals speciation reports. MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Flnal-« 6-1 [Rev 001/13/93] The dominant form of sulfur is sulfate sulfur. Acid generation potential due to pyritic sulfur, when detected, is more than compensated by neutralization potential due to carbonate species. This results in a negative acid forming potential. The Synthetic Precipitation Leaching Procedure (SPLP) results for all elements for all samples were below the toxicity characteristic criteria listed in 40 CFR 261.24 of 100 times primary drinking water standards. Mean values were generally more than two orders of magnitude lower than toxicity criteria. Additionally, results for those analytes that were compared to criteria of 100 times the secondary drinking water quality standards were lower than those criteria. Statistical Analyses The results of the statistical analyses indicate that the constituents within the zinc slag samples are log-normally distributed. Comparisons of the zinc slag data with lead slag data sets show that the zinc slag pile is lower in lead and iron and higher in zinc and manganese than the lead slag. Water Quality Impacts Based on the metals concentrations in the eluants of the two types of leaching tests performed on zinc slag samples (SPLP and column leach), potential annual metals loading from the zinc slag pile has been estimated. Calculations were performed for three of the primary elements of concern — lead, cadmium and zinc. Arsenic metal loading was not calculated because of non-detectable arsenic concentrations for the majority of the leachate samples. Using the combination of SPLP and the zinc column leach results, the metals load for the zinc slag pile for lead, cadmium and zinc is conservatively estimated at 0.5, 1.6 and 330 kilograms per year, respectively. These loading estimates may be refined as additional information becomes available. Soil Quality Impacts Results of the reconnaissance of the zinc slag pile showed no obvious impacts to surface soils in the vicinity of the pile. No evidence of particulate movement off the pile was noted. MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Final-RI 6"2 [Rev 001/13/93] Air Quality Impacts Emissions calculations demonstrate that wind erosion does not occur from the zinc slag pile and it can be concluded that there are no significant impacts from the zinc slag pile during undisturbed conditions. 62 Conclusions Regarding the Site Conceptual Model The site conceptual model for the Slag Pile RI (Figure 1-2) was developed by EPA and the Risk Assessment Technical Assistance Committee and presented in the work plan for the Slag Pile RI (MK, 1991a). The conceptual model presents five potential release mechanisms for the slag piles. These are: - wind - leaching - mixing by human activities - runoff (of particulate slag) - direct contact If certain release mechanisms can be shown not to occur, then secondary sources, exposure routes and potential receptors do not form a complete pathway. The following discussion applies the conclusions of the RI activities to each of the primary release mechanisms in order to show whether the conceptual model is valid for that particular mechanism. Each release mechanism is addressed in the order presented above. Release Mechanism 1 - Wind Wind erosion, or deflation of the zinc slag pile by wind, is addressed in Sections 4.4.2 and 5.5 of this report. Hourly average wind speed data multiplied by the appropriate factor to determine the maximum sustained wind gust does not meet or exceed the frictional velocity necessary to lift particles off the stationary pile. Therefore, the air pathway analysis results show that wind erosion is not a viable release mechanism for the zinc slag pile. Release Mechanism 2 - Leaching Leaching of elements of concern were tested by two different leaching procedures (SPLP and column leach), yielding the quantities of metals leached from a given mass or volume of the zinc slag pile. Quantity of metals leached were calculated by portioning the pile by whether it could most likely be represented by column leach or SPLP testing results. The zinc slag pile has the potential to contribute a small metals load of three of the elements MORRISON KNUDSEN CORPORATION B8\1883\ZINCRPT\Rnal-RI 6~3 [Rev 001/13/83] of concern. However, the concentration of zinc, lead, and cadmium are all below leaching criteria established by EPA of 100 times drinking water standards. Additional data collection activities are currently being undertaken under other PRP work plans to better define the hydrologic system in the vicinity of the major slag piles and along California Gulch. Key additional data to be evaluated include the portions of the Gulch that are gaining and losing streams, water quality data from piezometers, monitor wells and surface water sampling, and flow rates during the course of the year. Another consideration is the calculation of the residual sediment load and the contribution from other sources (i.e. tailings and soils) to the stream channel. At this time, the evaluations of impacts from leaching have been conservatively calculated. Additional considerations such as soil sorption, evaporation, dilution by ground and surface water, and sheet runoff of precipitation will need to be further evaluated before estimates of contribution to the hydrologic system can be completed. At this time, leaching as a release mechanism is retained. Release Mechanism 3 - Mixing by Human Activities Distribution of zinc slag by human activity has not been documented; however, volume decreases and evidence of the material on Leadville roadways indicate use. Release Mechanism 4-Runoff of Slag No evidence of transport of slag fines by surface runoff was observed at the zinc pile. Slag does not appear to run off piles onto adjacent soils in rivulets or channels. This primary release mechanism for slag should be eliminated as a concern at the site. Release Mechanism 5-Direct Contact Direct contact with the slag piles was considered insignificant in EPA's Preliminary Baseline Human Health Risk Assessment (EPA, 1991a). Therefore, it can be eliminated as a release mechanism. Summary of Verification of the Conceptual Model Of the five primary release mechanisms identified in the site conceptual model, only one can be considered viable based on findings provided in this Zinc Slag Pile Remedial Investigation. The one retained release mechanism is leaching. Before determining the actual contribution of leached constituents from the zinc slag pile, and their potential environmental significance, collation and summarization of data collected as part of other MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Flnal-RI 6-4 [Rev 0 01/13/93] work programs will need to be evaluated. All other primary mechanisms have been eliminated as a result of this remedial investigation. MORRISON KNUDSEN CORPORATION BB\1883\ZINCRFT\Final-RI 6-5 [Rev 0 01/13/93] 7.0 REFERENCES ACGIH, 1990. 1990-1991 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices, Appendix D, Particle Size-Selective Sampling Criteria for Airborne Paniculate Matter, American Conference of Governmental Industrial Hygienists. ASTM, 1992a. Standard Method for Particle Size Analysis of Soils, Designation D-422-63 (Reapproved 1990), Annual Book of ASTM Standards, 1992. ASTM, 1992b. Standard Practice for Sampling Aggregates, Designation: D-75-87, Annual Book of ASTM Standards, 1992. Blair, 1980. Leadville: Colorado's Magic City by Edward Blair, Pruett Publishing Company, Boulder, Colorado, 1980. Bloom, 1978. Geomorphology -A Systematic Analysis of Late Cenozoic Landforms, by Arthur L. Bloom, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1978. Bureau of Mines, 1980. A Simple Low-Cost Method for the Dissolution of Metal and Mineral Samples in Plastic Pressure Vessels, by R.F. Farrell, S.A. Matthes and AJ. Mackie, Bureau of Mines Report of Investigations, 1980. CDL, 1986. Yak Tunnel/California Gulch Remedial Investigation, State of Colorado Department of Law, Prepared by Engineering Science, 1986. EPA, 1992. Personal communications with Kevin Golden, Regional Meteorologist and Dale Wells, Environmental Engineer, Denver, Colorado, May 1992. EPA, 1991. Historical Mineral Processing Operations of the Leadville Mining District - California Gulch Superfund Site, Leadville, Colorado, U.S. EPA, Prepared by Jacobs Engineering Group, Inc., May 1991. EPA, 1991a. Preliminary Human Health Baseline Risk Assessment for the California Gulch NPL Site, Leadville, Colorado, Prepared by Roy F. Weston, Inc. for U.S. Environmental Protection Agency, December, 1991. MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Fln«l-RI 7-/-I1 [Rev 001/13/93] EPA, 1990a. Contract Laboratory Program Statement of Work for Inorganics Analysis, SOW- 4/90. EPA, 1990b. Exhibit 1, Work Plan, Residential Soils Sampling and Air Monitoring, prepared by Roy F. Weston for U.S. Environmental Protection Agency, August 1990. EPA, 1989a. Risk Assessment Guidance for Superfimd Volume I Human Health Evaluation Manual (Part A), Interim Final, EPA/540/1-89/002, Januarf y 1989. EPA, 1989b. Methods for Evaluating the Attainment of Cleanup Standards, Volume I, Soils and Solid Media, February 1989. EPA, 1989c. Draft Phase II Remedial Investigation Technical Memorandum, 1986-1987, California Gulch Site, Leadville, Colorado, U.S. EPA, Prepared by CH2M Hill, May 1989. EPA, 1988a. Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point and Area Sources, Fourth Edition. AP-42. U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711. Update of Fugitive Dust Emission Factors in AP-42 Section 11.2 - Wind Erosion. MRI No. 8985-K, Midwest Research Institute, Kansas City, MO., 1988. EPA, 1988b. Laboratory Data Validation Functional Guidelines for Evaluating Inorganics Analyses (draft), U.S. EPA Hazardous Site Evaluation Division, July 1, 1988. EPA, 1986. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, SW-846 U.S. EPA, Office of Solid Waste and Emergency Response, 1986. EPA, 1982. Test Methods, Technical Additions to Methods for Chemical Analysis of Water and Wastes, U.S. EPA, Environmental Monitoring and Support Laboratory, Cincinnati, Ohio, December 1982. EPA, 1978. Field and Laboratory Methods Applicable to Overburdens and Minesoils, EPA- 600/2-78-054, U.S. Environmental Protection Agency, March 1978. EPA, 1974. Mine Spoil Potentials for Soil and Water Quality, EPA 670/2-74-070, 1974. MORRISON KNUDSEN CORPORATION BB\1893\ZINCRPT\Flnal-RI 7~2 [Rev 001/13/93] MK, 1992. Interim Draft Report Lead Slag Pile Remedial Investigation at the California Gulch Site, Leadville, Colorado, prepared by Morrison Knudsen Corporation for Denver & Rio Grande Western Railroad Company, July 6, 1992. MK, 199 la. Work Plan for Slag Pile Remedial Investigation at California Gulch Site • Leadville, Colorado, Prepared by Morrison-Knudsen Corporation for Denver & Rio Grande Western Railroad Company, October 1991. MK, 199 Ib. Sampling and Analysis Plan for Slag Pile Remedial Investigation at California Gulch Site, Leadville, Colorado, Prepared by Morrison Knudsen Corporation Environmental Services Division for Denver & Rio Grande Western Railroad Company, November, 1991. NADP, 1990. National Atmospheric Deposition Program (lR-7)/National Trends Network, NADP/NTN Coordination Office, National Resource Ecology Laboratory Colorado State University, Fort Collins Colorado, January 1990. NIOSH, 1973. The Industrial Environment - Its Evaluation and Control, Chapter 33, The Influence of Industrial Contaminants on the Respiratory System, NIOSH, 1973. Res-ASARCO, 1991. Air Quality Monitoring Report, California Gulch Site. Leadville, Colorado, prepared by Woodward-Clyde Consultants for Res-ASARCO Incorporated, December 1991. Resurrection, 1992. Final Work Plan - Metals Speciation and Source Characterization at California Gulch CERCLA Site, Leadville, Colorado, Prepared by Camp Dresser and McKee, Inc. for Resurrection Mining Corporation, January 20, 1992. Simiu and Scanlan, 1978. Wind Effects on Structures: An Introduction to Wind Engineering, John Wiley & Sons, NY pp. 62-63. MORRISON KNUDSEN CORPORATION BB\1883\ZINCRPT\Rnal-RI 7~3 [Rev 001/13/93]