DRAFT

TABLE OF CONTENTS

EXECUTIVE SUMMARY........................................................................................................... vi

1.0 INTRODUCTION.............................................................................................................. 1

2.0 SITE HISTORY AND SITE DESCRIPTION................................................................... 2

2.1 Site Description and Background................................................................................. 2

2.1.1 Site Location....................................................................................................... 2

2.1.2 Geology and Groundwater................................................................................. 4

2.1.3 Surrounding Land Use and Populations............................................................. 6

2.1.4 Sensitive Ecosystems.......................................................................................... 7

2.1.5 Meteorology........................................................................................................ 7

2.2 Site Waste Characteristics............................................................................................ 7

2.3 Previous Investigations................................................................................................. 8

3.0 SITE CHARACTERIZATION OBJECTIVES AND PROCEDURES........................ 10

3.1 Data Quality Objectives

3.2 Chemical Analyses of Tailings and Soils.................................................................... 11

3.3 Geophysical Survey.................................................................................................... 12

3.4 Wetland Assessment................................................................................................... 12

3.5 Macroinvertebrate Characterization............................................................................ 13

3.6 Surface Water Characterization.................................................................................. 14

3.7 Site Mapping............................................................................................................... 14

3.8 Quality Assurance/Quality Control............................................................................ 14

4.0 ANALYTICAL RESULTS.............................................................................................. 15

4.1 Chemical Analyses of Tailings and Soils.................................................................... 15

4.1.1 Surficial Soil, Tailings and Sediment XRF Results.......................................... 15

4.1.2 Laboratory Results............................................................................................ 16

4.2 Geophysics and Tailings Volume Estimates............................................................... 18

4.2.1 Exposed Tailings Volumes................................................................................ 18

4.2.2 Buried Tailing Volumes.................................................................................... 18

4.3 Summary of Wetland Assessment.............................................................................. 20

4.3.1 Findings............................................................................................................ 20

4.3.2 Plant and Animal Communities........................................................................ 21

4.3.3 Conclusions and Recommendations................................................................. 23

4.4 Macroinvertebrate Characterization............................................................................ 24

4.3.1 Methods............................................................................................................ 24

4.3.2 Results............................................................................................................... 24

4.5 Mercury Investigations............................................................................................... 25

4.6 Summary of USGS Quantification of Metal Loading to Silver Creek...................... 26

4.7 Summary of Waste Sources........................................................................................ 28

5.0 STREAMLINED RISK ASSESSMENT......................................................................... 30

5.1 Human Health Risk Assessment............................................................................... 31

4.2 Screening Level Problem Formulation and Ecological Risk Assessment................. 31

5.3 Uncertainty Analysis................................................................................................. 33

5.4 Risk Assessment Results - Human Health................................................................ 34

5.5 Risk Assessment Results - Ecological Receptors...................................................... 35

5.6 Removal Action Considerations............................................................................... 40

5.6.1 Upstream Sources............................................................................................. 40

5.6.2 TMDL Loads................................................................................................... 40

5.7 Removal Site Inspection Summary........................................................................... 41

5.7.1 Source and Nature of the Release.................................................................... 41

5.7.2 Threat to Public Health and Environment........................................................ 41

5.7.3 Factors Relating to Need for Removal Action............................................... 42

5.8 Recommendation....................................................................................................... 43

6.0 APPLICABLE, RELEVANT AND APPROPRIATE REQUIREMENTS.................... 44

7.0 IDENTIFICATION OF REMOVAL ACTION OBJECTIVES..................................... 45

8.0 REFERENCES................................................................................................................. 46

LIST OF TABLES

Table 1 Dissolved Zinc Concentrations Upstream and Downstream of SMC, mg/L

Table 2 Analytical Results, Silver Maple Claims Surface Grid, mg/kg

Table 3 Silver Maple Claims XRF Analytical Results, Miscellaneous Samples, mg/kg

Table 4 Total and Synthetic Precipitation Leaching Procedure (SPLP) Metal Concentrations and Acid-Base Accounting Results in Tailings and Sediment, Silver Maple Claims, Park City, UT

Table 5 Cation Exchange Capacity and Total Organic Carbon, Wetland Sediments,

Silver Maple Claims, Park City, UT

Table 6 Biological Sample Results, mg/kg dry weight

Table 7 BLM Mercury Analytical Results, Silver Creek

Table 8 Taxonomic list and abundances of aquatic invertebrates collected 25 July 2002 at a beaver pond on Silver Creek.

Table 9 Summary of results for an aquatic invertebrate sample collected 25 July 2002 at a beaver pond on Silver Creek

Table 10 Computation of RMC for Leaching, Silver Maple Claims

Table 11 Silver Maple Claims Comparison of Analytical Results and Risk Management

Criteria

LIST OF FIGURES

Figure 1 Site Location Silver Maple Claims

Figure 1B Groundwater Conceptual Model

Figure 2 Site Features, Sampling and Geophysical Locations

Figure 3 Silver Maple Claims Site Photographs

Figure 4 1962 Image Showing Tailing Areas, Silver Maple Wetland

Figure 5 Biogeochemical Site Conceptual Model

Figure 6 Mine Waste Site Conceptual Model for Human Ecological Receptors

Figure 7 Plant Communities of Silver Maple Wetland, Park City, Utah

LIST OF ATTACHMENTS

Attachment 1 Quantification of metal loading to Silver Creek through the Silver Maple

Claims area, Park City, USGS, May 2002

Attachment 2 Quality Assurance/Quality Control XRF Results

Attachment 3 Wetland Functional Assessment, Silver Maple Claims

Attachment 4 Geological Characterization of Silver Maple Claims Park City, Utah Attachment 5 Preliminary Treatment Information

LIST OF ACRONYMS

ABA Acid Base Accounting

ARARs Applicable or Relevant and Appropriate Requirements

ARD Acid Rock Drainage

ASTM American Society for Testing Materials

AWQC Ambient Water Quality Criteria

BLM Bureau of Land Management

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

cy cubic yard

DAF dilution attenuation factor

DQO Data Quality Objective

GPS Global Positioning System

HGM Hydrogeomorphic Method

ICP Inductively Coupled Plasma

kg kilogram

msl Mean Sea Level

NCP National Contingency Plan

NIST National Institute of Standards and Technology

NRCS Natural Resources Conservation Service

NMWMP Nevada Meteoric Water Mobility Procedure

NOAEL No Observed Adverse Effect Level

NSTC National Science and Technology Center

PD Prospector Drain

PEC Probable Effect Concentration

QA/QC Quality Assurance/Quality Control

RSI Removal Site Inspection

RMC Risk Management Criteria

SCT Silver Creek Tailings (Prospector Square Tailings)

SMC Silver Maple Claims

SPLP Synthetic Precipitation Leaching Procedure

SRB Sulfate reducing bacteria

TMDL Total Maximum Daily Load

TOC Total Organic Carbon

TRV Toxicity Reference Value

UDEQ Utah Department of Environmental Quality

USACE U.S. Army Corps of Engineers

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

UWQS Utah Water Quality Standards

XRF X-ray Fluorescence Spectroscopy

EXECUTIVE SUMMARY

The Bureau of Land Management (BLM) prepared this Removal Site Inspection for the Silver Maple Claims (SMC) site under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), and National Contingency Plan (NCP) sections applicable to removal actions (40 CFR §300.415 (b)(4)(1)), and EPA guidance on conducting non-time critical removal actions under CERCLA. The SMC is located immediately east of Park City, Utah. Park City has a rich mining history since the discovery of lead-silver ore in the 1870's. Mine and mill tailings were dumped for many years at the SMC site. The SMC site consists of tailings from inactive, historic high grade silver milling and reprocessing operations since the 1880s. Tailings were processed at the Ontario Mill and Pacific Bridge mills in Park City and stored in tailings impoundments at the location of the current Prospector Square. The area is popular for hiking, biking, jogging, and wildlife viewing along the adjacent “Rail Trail,” a site developed as the Historic Railroad Grade.

Topography surrounding the site of the Silver Creek watershed is mountainous and the elevation of the site is 6,700 feet. Diverse flora occupies the wetland where tailings are not exposed, including sedges, rushes, willows, cattails and cottonwoods and several active beaver ponds. The site covers approximately 13 acres situated on two inactive, unpatented placer mining claims and the tailings lie mostly submerged beneath a biologically functional 7.5 acre wetland. Silver Creek has a drainage area of 17.4 square miles, principally occupied by Park City and ski area land uses. Silver Creek is listed in the State’s 303(d) list of water quality-impaired waterbodies for which a Total Maximum Daily Load (TMDL) is high priority. Zinc and cadmium are the water quality-limiting parameters. Tailings occur throughout the site and are mostly submerged by the wetland. Small tailings piles are exposed above the mean water level. The buried tailings are up to 11 feet in thickness and most are buried beneath more recent sediments and ponded water. Sample results from various investigations indicate concentrations of lead and zinc in the 5,000-15,000 ppm range in tailings and 2090-7500 ppm in surface tailings and sediment. Arsenic, copper and mercury are also chemicals of concern at the site.

The U.S. Geological Survey performed a tracer injection study with synoptic sampling to identify the sources of metal loadings to Silver Creek. The Prospector Drain (PD) enters the site underwater near the west property boundary and has high concentrations of cadmium and zinc. PD drains shallow groundwater in the eastern portion of the Prospector Square tailings. The following are the major sources and the percent of cumulative zinc loading to Silver Creek (from Park City to Wanship):

· Upstream sources supplies about 14 % of the loading to the reach and 6.9 kg/day to SMC,

· Prospector Drain supplies about 18% of the loading to the reach and 8.9 kg to SMC

· SMC supplies about 17% of the loading to the reach and 8.5 kg/day (and captures 7.5 kg/day).

Water quality standards for cadmium and zinc are exceeded upstream of SMC. Groundwater modeling shows that up to 70% of the contaminated groundwater from Prospector Square is not captured by PD and flows into SMC. Approximately 3800 cubic yards of on-site, exposed, oxidized tailings are believed to contribute most of the on-site SMC metals loading via acid rock drainage. Wetland processes remove the cadmium and zinc loads within the site boundary. An estimated 142,000-177,000 cubic yards of less reactive, reduced, buried tailings exist on-site.

Human health risk to users of the Rail Trail may occur from exposure to tailings. BLM conducted an interim removal action in 2003, but the RSI finds further removal action is warranted to reduce risk and meet TMDL requirements. High concentrations of metals in exposed tailings are a threat to human and ecological receptors, and contribute to metals loadings in Silver Creek. Water quality exceeds zinc standards for the protection of aquatic life upstream and downstream of SMC by an average of 2-fold. The wetland biological and hydrological functioning was found to be high. Ecological risk from contaminated sediments is moderate and may affect sensitive receptors such as avian species; further studies should be conducted prior to selecting a remedy involving removal of sediment or buried tailings. Monitoring wells should be installed to verify and fine-tune the groundwater modeling effort.

1.0 INTRODUCTION

The U.S. Department of Interior, Bureau of Land Management (BLM) prepared this Removal Site Inspection (RSI) for the Silver Maple Claims (SMC) site. This report has been prepared in accordance with the criteria established under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), sections of the National Contingency Plan (NCP) applicable to removal actions (40 CFR § 300.415 (b) (4) (1)). The report is also consistent with the U.S. Environmental Protection Agency (USEPA) guidance document, Guidance on Conducting Non-Time Critical Removal Actions Under CERCLA.

The goal of the RSI is to determine whether a removal action is warranted per the NCP. The objectives of the site characterization were to: (1) characterize the nature and extent of hazardous substances at the site; (2) determine the chemical characteristics of the tailings; (3) conceptually assess wetland removal processes (4) determine the biological and hydrological functioning of the wetlands, and (5) assimilate other site characterization results, (6) perform a streamlined risk assessment.

The preparation of this RSI involved the following activities:

· A review of existing historical and regulatory information pertaining to the site, including:

(1) historic aerial photos, 1962 and 1967

(2) groundwater quality data from USGS (USGS, 1989),

(3) surface water quality data from EPA (2001a) and USGS (2000)

(4) environmental data from the Site Inspection (Roy F. Weston, 1989)

(5) USGS 2002 tracer study of the site

(6) reVison Inc. and Argonne National Laboratories groundwater models.

· Initial site reconnaissance (6/5/02).

· Site characterization work in 2002 and 2003.

2.0 SITE HISTORY AND SITE DESCRIPTION

2.1 Site Description and Background

Park City, Utah has a rich historic mining history since the discovery of lead-silver ore in the 1870's. Mine and mill tailings were dumped for many years at the SMC site, although there was little mining at the site itself. The SMC site consists of tailings from inactive, historic high grade silver milling and reprocessing operations since the 1880s. Tailings were processed at the Ontario Mill and Pacific Bridge mills in Park City and stored in tailings impoundments at the location of the Silver Creek Tailings (SCT) site (the current Prospector Square) and downstream at Richardson Flats. Prospector Square is located upstream of the site where milling of the ore had also taken place. These tailings were covered and developed for homes and commercial development in the 1970s. Historical aerial photography for 1962 and 1967 indicates tailings/fill materials were transported downstream via Silver Creek onto the BLM-administered parcel, the SMC, by sluicing, flooding and by dumping of low grade ore by truck (Weston, 1989). Unprocessed ore was also reported to be stockpiled along Silver Creek (Weston, 1989).

From 1906 through 1926 E. J. Beggs filed claim notices on the Beggs placer mining claims that included SMC. In 1915, the Beggs Milling Company constructed a mill thought to be on the present SMC near the main beaver pond area to reprocess tailings. Prior to 1916, tailings from all the mills were sluiced into Silver Creek and carried downstream as far as seven miles. Because of farmer’s complaints the Ontario Mining Company was forced to construct tailings dams (SAIC, 1992).

During the late 1970s and 1980s, a residential subdivision and commercial development was built directly on the SCT Site (Weston, 1989). Work performed by USGS and others indicates that Prospector Square Tailings are