! I *••-.. f"' YAK TUNNEL / CALIFORNIA GULCH REMEDIAL INVESTIGATION DMINISTR RECOR PREPARED FOR STATE OF COLORADO DEPARTMENT OF LAW FEBRUARY 28,1936 PREPARED BY ENGINEERING-SCIENCE, INC, 1100^TOUDENV^t, TCOLORAD STREETO 8020, SUIT4 E 1100 IN COOPERATION Wl THE U.S. ENVIRONMENTAL PROTECTION AGENCY TABLE OF CONTENTS EXECUTIVE SUMMARY Goals of the Remedial Investigation i Site Description and Background Information i Major Findings ii CHAPTER 1 - INTRODUCTION 1-1 CHAPTER 2 - SITE DESCRIPTION AND BACKGROUND INFORMATION Sources, Pathways, and Receptors of Contamination 2-4 Sources 2-4 Pathways and Receptors 2-7 Hazard Evaluation of Selected Hazardous Substances 2-8 Human Health 2-8 Wildlife 2-9 Vegetation 2-9 Aquatic life 2-10 Demographics 2-10 Land Use 2-12 _jP.laiife 2-13 —- Climatology 2-13 CHAPTER 3 - SITE HISTORY AND GEOLOGY History 3-1 Historical Water Quality of Yak Tunnel Drainage 3-9 Historical Water Quality of the Leadville Mine Drainage Tunnel 3-9 Tailings and Mill History 3-12 Mining Activities 3-15 Underground Mining 3-15 Milling Processes 3-17 Smelter Residues and Emissions 3-18 Site Geology 3-19 Surficial Materials 3-19 Bedrock Geology 3-20 Ore Deposits 3-22 Geochemistry Metal Dispersion from Mineralization 3-24 Sulfide Oxidation Processes 3-26 Metal Dispersion in Surface and Ground Waters . 3-27 Metals in Soils 3-31 CHAPTER 4 - MINING WASTE INVESTIGATION Tailings Ponds-.-. 4-rl Waste Piles 4-8 California Gulch 4-8 Stray Horse Gulch 4-11 Contaminated Soils and Sediment 4-12 CHAPTER 5 - GROUND WATER INVESTIGATION Resources and Uses 5-2 Occurrence 5-2 Uses 5-5 Nature and Extent of Contamination 5-10 California Gulch 5-12 Arkansas River Alluvium 5-32 Environmental and Public Health Effects 5-33 CHAPTER 6 - SURFACE WATER INVESTIGATION Resources and Uses 6-1 Description 6-1 Potential for Flood Damage 6-5 Water Use and Supply 6-6 Nature and Extent of Contamination 6-9 Past Studies 6-9 CERCLA Investigations 6-15 EPA CERCLA Investigations 6-15 Engineering-Science CERCLA Investigations 6-42 Enviromental and Public Health Effects 6-81 CHAPTER 7 - AQUATIC BIOTA INVESTIGATION Resources and Use 7-2 Macrohabitat 7-2 Aquatic Biota 7-4 Nature and Extent of Contamination 7-5 Sampling Stations 7-5 Sampling Methods 7-6 Sampling Results " 7-7 Discussion of Contaminants 7-21 Contaminants of Concern and Their Extent in the Arkansas River 7-22 Impacts to the Aquatic Biota Resource 7-41 CHAPTER 8 - SOILS INVESTIGATION Resources and Use 8-1 Nature and Extent of Contamination 8-3 Soil Physical/Chemical Characteristics of Concern 8-3 Toxic Substances of Concern 8-6 Cumulative Geographic Extent of Contamination 8-17 Statistical Analysis of Data 8-26 Metals Concentrations 8-28 Environmental and Public Health Effects 8-36 CHAPTER 9 - VEGETATION INVESTIGATION Resources and Sse 9-1 Nature and Extent of Contamination 9-2 Contaminants of Concern 9-2 Geographic Extent of Contamination in Vegetation 9-9 Results 9-13 Tennessee Creek Valley and Arkansas River Valley Pastures 9-13 Tennessee Creek Valley and Arkansas River Valley Wetlands 9-23 California Gulch and Stray Horse Gulch 9-24 Environmental and Public Health Effects 9-24 CHAPTER 10 - AIR QUALITY INVESTIGATION Site Description 10-1 Nature and Extent of Contamination 10-2 Sources 10-3 Receptors 10-3 Transport Mechanism 10-5 Source/Receptor Relationship 10-5 Long-term Impact 10-9 Environmental and Public Health Effects 10-11 CHAPTER 11 - GENERAL RESPONSE ACTIONS AND TECHNOLOGIES Introduction 11-1 Summary of Site Problems 11-2 General Response Actions 11-2 Formation of Remedial Technologies 11-3 References Cited R-l LIST OF TABLES Number Title Page 2.1 Populations of Lake County and Leadville 1900-1983 with Forecasts through 2010 2-11 2.2 Annual and 10-Year Average Precipitation (inches) • 2-15 3.1 Yearly Concentrations of Hazardous Metals in the Yak Tunnel Drainage 3-10 3.2 Yearly Concentrations of Hazardous Metals (Zinc) in the Leadville Drainage Tunnel Discharge 3-11 3.3 Mobility of Some Elements in Surficial Environments 3-32 4.1 Chemical Analysis of Tailings Pond 3 4-4 4.2 Analysis of Tailings Samples from Leadville, Colorado (EPA Data) 4-6 4.3 Soils/Tailing EP-Toxicity Data (EPA Data) 4-7 4.4 Summary of Waste Rock Pile Geochemistry and Other Parameters, California Gulch and Stray Horse Gulch (ES Data) 4-10 4.5 Summary of Geochemistry and other Parameters for Soils and Sediments in California and Stray Horse Gulch (ES Data) 4-14 4.6 Analysis of Soils Samples from Leadville, Colorado (EPA Data) 4-16 5.1 Summary of PEA Monitoring Well Construction Data 5-7 5.2 Summary of Existing Well Construction Data 5-9 5.3 Private Wells Currently in Use 5-11 5.4 Yak Tunnel/California Gulch Summary of Ground Water Sampling Results (mg/1) 5-19 5.5 Federal and State Water Quality Standards 5-24 5.6 Summary of Private Well Sampled by EPA 5-28 5.7 Summary of results from Private Wells Sampled by ES 5-31 6.1 Arkansas River Basin Affected by Metal Mine Drainage 6-10 6.2 Water Quality Data from STORET on the Arkansas River from Leadville to Near Canon City 6-12 6.3 EPA and Es Sampling Location Descriptions for California Gulch and its Tributaries 6-16 6.4 EPA Surface Water Data Summary 6-19 6.5 Federal and State Water Quality Standards 6-28 6.6 EPA Surface Water Data Summary 6-34 6.7 Total Cadmium Loading Values from EPA Data 6-36 6.8 Total Copper Loading Values from EPA Data 6-37 6.9 Total Lead Loading Values from EPA Data 6-38 6.10 Total Zinc Loading Values from EPA Data 6-39 6.11 Total Metals in the Upper Arkansas River 6-70 7.1 Concentrations of Metals (mg/kg) from Invertebrates taken from the Arkansas River and Tributaries during May and October, 1985 7-8 7.2 Concentrations of Metals (mg/kg) from Sediment taken from the Arkansas River and Tributaries during October, 1985 7-9 7.3 Number of Aquatic Macroinvertebrates per Square Meter Collected from the Arkansas River and Associated Tributaries in 1985 (ES Data) 7-12 7.4 Habitat Description of Fish Sampling Stations 7-14 7.5 Fish Collected from the Arkansas River and Tributaries during September, 1985 7-16 7.6 Fish Collected from the Arkansas River and Tributaries during October, 1985 7-17 7.7 Maximum Allowable Concentrations (mg/1) for Specific Metals based on Toxicity Data 7-24 7.8 Acutely and Chronically Toxic Concentrations of Lead to Trout 7-26 7.9 Acutely and Chronically Toxic Concentrations of Copper to Trout 7-28 7.10 Acutely and Chronically Toxic Concentrations of Zinc to Trout 7-32 7.11 Acutely and Chronically Toxic Concentrations of Cadmium to Trout 7-36 7.12 Means and Ranges of Concentrations (mg/1) of Selected Metals in Water of the Arkansas River with Concentrations above EPA Criteria Levels Noted 7-38 8.1 Ranges of Total Metal Concentrations in Reference Locations, Contaminated Sites, "Normal" Levels, Regulatory Limits, and Known Toxic Levels 8-7 8.2 Arkansas River Valley Total Soil Metals and pH 8-17 8.3 Arkansas River Valley Plant-Available Metals 8-20 8.4 Vertical Distribution of Mean Total and Plant-Available Metal Concentrations in the Soil Profile-Arkansas River Valley 8-33 9.1 Summary of Metals Concentrations in Plant Tissues 9-4 9.2 Summary of Plant Cover Data for Irrigated Pastures 9-14 9.3 Plant Production and Percent Utilization 9-16 9.4 Summary of Plant Tissue, Cover and Production Data 9-17 10.1 Selected Toxic Composition of Tailings Pond and Dust Samples 10-4 10.2 Particle Size Analysis of Mine Tailings in California Gulch 10-6 10.3 Comparison of Dust Constituents (Percent of Metals Analyzed) 10-8 11.1 Mining Wastes 11-4 11.2 Ground Water 11-7 11.3 Surface-Water 11-8 11.4 Aquatic Biota, Soils and Vegetation, and Air Quality 11-11 LIST OF FIGURES Number Title 2.1 Location Map 2.2 Geographical Features and Outline of Productive Area, Leadville District, Colorado 2-3 2.3 Mine Wastes and Slag Piles in and Near the California Gulch Drainage Area 2-5 2.4 Precipitation 2-16 3.1 View of Leadville from Carbonate Hill 3-3 3.2 Carbonate Hill 3-4 3.3 Smelters with Mines Near Leadville Looking West 3-5 3.4 Plan View of Yak Tunnel 3-7 3.5 Location of Tailings Ponds 3-13 3.6 Mining/Process Schematic 3-16 3.7 Principal Faults and Areas of Principal Ore Bodies 3-21 3.8 Bedrock Geology Map 3-22 4.1 Waste Pile and Soil/Sediment Sample Locations- Stray Horse and California Gulches 4-2 5.1 Elevation of Potentiometrie Surface, 1944 5-4 5.2 Monitoring Well Location Map 5-6 5.3 private Wells Location Map 5-8 5.4 Surface Flow and Ground Water Level 5-14 5.5 Dissolved Cadmium Concentration 5-15 5.6 Sulfate Concentration 5-16 6.1 Location Map 6-3 6.2 Fryingpan-Arkansas Project Map 6-7 6.3 EPA Surface Water Sampling Map 6-18 6.4 Dissolved Zinc in California Gulch 6-30 6.5 Dissolved Zinc in California Gulch 6-31 6.6 Total Cadmium in California Gulch 6-32 6.7 Dissolved Cadmium in California Gulch 6-33 6.8 Cadmium Mass Loadings in California Gulch 6-40 6.9 Zinc Mass Loadings in California Gulch 6-41 6.10 Surface Water Sampling Locations along California Gulch 6-43 6.11 Surface Water Sampling Locations along the Arkansas River 6-44 6.12 California Gulch Reaches 6-47 6.13 Arkansas River Reaches 6-48 6.14 Cadmium in California Gulch (May, 1985) 6-49 6.15 Cadmium in California Gulch (June, 1985) 6-50 6.16 Cadmium in California Gulch (August, 1985) 6-51 6.17 Copper in California Gulch (May, 1985) 6-52 6.18 Copper in California Gulch (June, 1985) 6-53 6.19 Copper in California Gulch (August, 1985) 6-54 6.20 Lead in California Gulch (May, 1985) 6-55 6.21 Lead in California Gulch (June, 1985) 6-56 6.22 Lead in California Gulch (August, 1985) 6-57 6.23 Zinc in California