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.