Engineering Evaluation/Cost Analysis

Big Bug Watershed: Money Metals and Providence Mines Bradshaw Mountains Prescott National Forest, Arizona

Prepared for: USDA Forest Service 333 Broadway SE Albuquerque, NM 87102

Prepared by: Weston Solutions, Inc. 960 West Elliot Road, Suite 201 Tempe, Arizona 85284

Contract No. AG-8371-D-09-0191

December 2010

Final Engineering Evaluation/Cost Analysis Big Bug Watershed: Money Metals and Providence Mines Bradshaw Mountains, Prescott National Forest, Arizona December 2010

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...... E1 1.0 INTRODUCTION...... 1 1.1 SITE LOCATION AND DESCRIPTION ...... 1 1.2 AREA POPULATION ...... 2 1.3 PHYSICAL CHARACTERISTICS ...... 2 1.3.1 Geologic and Hydrologic Setting ...... 2 1.3.1.1 Hydrology ...... 3 1.3.2 Regional Climate ...... 4 1.4 SITE OPERATION HISTORY AND CURRENT SITE CONDITIONS ...... 4 1.4.1 Money Metals Mine ...... 4 1.4.2 Current Conditions ...... 5 1.4.3 Providence Mine ...... 5 1.4.3.1 Current Conditions ...... 6 2.0 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS ...... 7 2.1 DEFINITION OF ARARS ...... 7 2.1.1 Applicable Requirements ...... 8 2.1.2 Relevant and Appropriate Requirements ...... 8 2.1.3 Other Requirements To Be Considered ...... 9 2.1.4 Waiver of ARARs ...... 9 2.2 DEVELOPMENT OF ARARS ...... 9 2.3 SITE-SPECIFIC ARARS AND TBCS ...... 10 2.3.1 Surface Water ...... 11 2.3.1.1 Human Health Surface Water ARARs ...... 12 2.3.1.2 Human Health Surface Water TBCs ...... 12 2.3.1.3 Ecological Surface Water ARARs ...... 13 2.3.1.4 Ecological Surface Water TBCs ...... 13 2.3.2 Groundwater ...... 13 2.3.2.1 Human Health Groundwater ARARs ...... 13 2.3.2.2 Human Health Groundwater TBCs ...... 14 2.3.2.3 Ecological Groundwater ARARs and TBCs...... 14 2.3.3 Soil and Waste Rock ...... 14 2.3.3.1 Human Health Soil ARARs ...... 14 2.3.3.2 Human Health Soil TBCs ...... 14 2.3.3.3 Ecological Soil ARARs ...... 15 2.3.3.4 Ecological Soil TBCs ...... 15 2.3.4 Sediment ...... 16 2.3.4.1 Human Health Sediment ARARs ...... 16 2.3.4.2 Human Health Sediment TBCs ...... 16 2.3.4.3 Ecological Sediment ARARs...... 16 2.3.4.4 Ecological Sediment TBCs ...... 16 3.0 SOURCE, NATURE, AND EXTENT OF CONTAMINATION ...... 17 3.1 PREVIOUS INVESTIGATIONS ...... 17 3.1.1 Characterization of Big Bug Watershed ...... 17 3.1.1.1 Money Metals Mine ...... 17

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3.1.1.2 Providence Mine and Township ...... 18 3.1.2 Preliminary Assessment/Site Inspection ...... 19 3.2 CURRENT INVESTIGATION ...... 19 3.2.1 Deviations from the Sampling Plan ...... 22 3.3 EVALUATION OF DISTRIBUTION OF CONTAMINANTS ...... 22 3.3.1 Money Metals Site ...... 23 3.3.1.1 Sediment ...... 23 3.3.1.2 Waste Rock ...... 23 3.3.1.3 Surface Water ...... 23 3.3.2 Providence Mine ...... 24 3.3.2.1 Sediment ...... 24 3.3.2.2 Surface Water ...... 25 3.3.2.3 Soil ...... 26 3.3.2.4 Waste Rock ...... 26 3.3.2.5 Groundwater ...... 26 4.0 EVALUATION OF RISK ...... 27 4.1 DATA REVIEW ...... 27 4.1.1 Initial Chemical Data Screening ...... 27 4.2 STREAMLINED HUMAN HEALTH RISK ASSESSMENT ...... 29 4.2.1 Exposure Assessment ...... 30 4.2.1.1 Contaminant Sources ...... 30 4.2.1.2 Release Mechanisms ...... 30 4.2.1.3 Potential Receptors ...... 30 4.2.1.4 Exposure Media ...... 30 4.2.1.5 Exposure Route(s) ...... 31 4.2.2 Evaluation of Human Health Risk ...... 31 4.2.2.1 Money Metals Mine ...... 31 4.2.2.2 Providence Mine and Township ...... 34 4.3 STREAMLINED ECOLOGICAL RISK ASSESSMENT ...... 38 4.3.1 Ecological Setting ...... 38 4.3.2 Ecological Exposure Model ...... 39 4.3.3 Evaluation of Ecological Risk ...... 39 4.3.3.1 Money Metals Mine ...... 40 4.3.3.2 Providence Mine ...... 44 4.4 UNCERTAINTY EVALUATION ...... 49 5.0 IDENTIFICATION OF REMOVAL ACTION OBJECTIVES ...... 51 5.1 DETERMINATION OF REMOVAL ACTION SCOPE ...... 51 5.2 REMOVAL ACTION OBJECTIVES...... 51 5.3 IDENTIFICATION OF CLEAN UP ACTION LEVELS ...... 51 5.4 ESTIMATE OF VOLUME OF CONTAMINATED MATERIAL ...... 52 5.4.1 Money Metals Mine ...... 52 5.4.2 Providence Mine ...... 52 6.0 IDENTIFICATION AND ANALYSIS OF REMOVAL ACTION ALTERNATIVES ...... 55 6.1 ALTERNATIVES CONSIDERED BUT NOT EVALUATED ...... 55 6.2 EVALUATION CRITERIA ...... 56 6.2.1 Effectiveness ...... 56

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6.2.2 Implementability ...... 57 6.2.3 Cost ...... 57 6.3 COMMON ACTIVITIES ...... 58 6.4 EVALUATION OF REMOVAL ALTERNATIVES...... 58 6.4.1 Alternative 1: No Action ...... 58 6.4.1.1 Effectiveness ...... 58 6.4.1.2 Implementability ...... 58 6.4.1.3 Cost ...... 59 6.4.2 Alternative 2: Institutional Controls ...... 59 6.4.2.1 Effectiveness ...... 60 6.4.2.2 Implementability ...... 60 6.4.2.3 Cost ...... 61 6.4.3 Alternative 3: On-Site Consolidation and Capping ...... 61 6.4.3.1 Effectiveness ...... 64 6.4.3.2 Implementability ...... 64 6.4.3.3 Cost ...... 64 6.4.4 Alternative 4: Excavation and Off-Site Disposal (Providence Mine Only) ...... 65 6.4.4.1 Effectiveness ...... 66 6.4.4.2 Implementability ...... 66 6.4.4.3 Cost ...... 66 7.0 COMPARATIVE ANALYSIS OF REMOVAL ACTION ALTERNATIVES ...... 67 7.1 MONEY METALS ...... 67 7.1.1 Effectiveness ...... 67 7.1.2 Implementability ...... 68 7.1.3 Cost ...... 69 7.2 PROVIDENCE ...... 69 7.2.1 Effectiveness ...... 70 7.2.2 Implementability ...... 71 7.2.3 Cost ...... 72 8.0 RECOMMENDED REMOVAL ACTION ALTERNATIVE ...... 73 9.0 REFERENCES ...... 75

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LIST OF TABLES

Table 1 Summary of Human Health and Ecological ARARs and TBCs...... 11 Table 2 Mine Site Planned vs Actual Sample Quantity ...... 21 Table 3 Money Metals Mine – Sediment Ecological Risk Evaluation ...... 41 Table 4 Money Metals Mine – Soil Ecological Risk Evaluation ...... 42 Table 5 Money Metals Mine – Waste Material Ecological Risk Evaluation...... 43 Table 6 Providence Mine – Sediment Ecological Risk Evaluation ...... 45 Table 7 Providence Mine – Soil Ecological Risk Evaluation ...... 46 Table 8 Providence Mine – Waste Material Ecological Risk Evaluation ...... 47 Table 9 Cleanup Action Levels ...... 52 Table 10 Summary Comparison of Potential Alternatives ...... 67 Table 11 Effectiveness Comparison – Money Metals ...... 67 Table 12 Implementability Comparison – Money Metals ...... 69 Table 13 Cost Comparison – Money Metals Mine ...... 69 Table 14 Effectiveness Comparison – Providence ...... 71 Table 15 Implementability Comparison ...... 72 Table 16 Cost Comparison – Providence Mine ...... 72

LIST OF FIGURES

Figure 1 Site Vicinity Map Figure 2 Money Metals Mine – Previous Sample Locations Figure 3 Providence Mine – Previous Sample Locations Figure 4 Money Metals Mine – EE/CA Sampling Locations Figure 5 Money Meals Mine – EE/CA Surface Water Sample Locations Figure 6 Providence Mine – EE/CA Sampling Locations Figure 7 Money Metals Mine – Proposed Surface Water Monitoring Locations Figure 8 Money Metals Mine – Potential Repository Boundary Figure 9 Providence Mine – Institutional Controls (Approximate Fence Boundary)

APPENDICES

Appendix A Photographic Log Appendix B Potential ARARs and TBCs Appendix C Data Summary Tables Appendix D Field Notes and Sketches Appendix E Sample Location GPS Coordinates Appendix F Laboratory Analytical Reports Appendix G Initial Data Screening Tables Appendix H Site Conceptual Exposure Model Appendix I Waste Volume Calculations Appendix J Cost Tables

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LIST OF ACRONYMS

4WD four wheel drive A&We aquatic and wildlife ephemeral A&Ww aquatic and wildlife warm water A.A.C. Arizona Administrative Code ABA acid base accounting ADEQ Arizona Department of Environmental Quality ADWR Arizona Department of Water Resources AgI agricultural irrigation AgL agricultural livestock watering AMA active management area ARAR applicable or relevant and appropriate requirements ATV all-terrain vehicle AWQS Aquifer Water Quality Standards AZ WQS Arizona Water Quality Standards (surface water) AZGFD Arizona Game and Fish Department AZPDES Arizona Pollutant Discharge Elimination System bgs below ground surface BLM Bureau of Land Management CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations COPC contaminant of potential concern COPEC contaminant of potential ecological concern Columbia Columbia Analytical Services, Inc. CWA Clean Water Act cy cubic yards E & E Ecology and Environment EE/CA Engineering Evaluation/Cost Analysis Eco-SSL Ecological Soil Screening Level EPA US Environmental Protection Agency ERA Ecological Risk Assessment ESA Endangered Species Act FBC full-body contact FC fish consumption G&SRBM Gila and Salt River Base and Meridian GPS global positioning system HDPE high density polyethylene MCL Maximum Contaminant Level mg/kg milligram per kilogram mg/L milligrams per liter MSO Mexican spotted owl NAWQS National Ambient Water Quality Standards NCP National Contingency Plan NPDES National Pollutant Discharge Elimination System

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LIST OF ACRONYMS (CONTINUED)

NPL National Priority List nrSRL non-residential Soil Remediation Level OSHA Occupational Safety and Health Administration PAC Protected Activity Center PA/SI Preliminary Assessment/Site Inspection PBC Partial body contact PRSC post removal site control PUF polyurethane foam RA Risk Assessment RAO Removal Action Objective RCRA Resource Conservation Recovery Act RMC Risk Management Criteria RSL Regional Screening Level rSRL Residential Soil Remediation Level SAP Sampling and Analysis Plan SCEM Site Conceptual Exposure Model SM Standard Method SOW Statement of Work SPLP Synthetic Precipitation Leaching Procedure SRL Soil Remediation Level TAL target analyte list TBC To-be-considered TCLP Toxicity Characteristic Leaching Procedure TES Threatened and Endangered Species TOC total organic carbon TSS total suspended solids UCL95 95% upper confidence limit U.S.C. United States Code USDA United States Department of Agriculture USFWS United States Fish and Wildlife Service USFS United States Forest Service USGS United States Geologic Survey Weston Weston Solutions, Inc. WRCC Western Regional Climate Center

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EXECUTIVE SUMMARY

Weston Solutions, Inc. (Weston®) was contracted by the United States Department of Agriculture Forest Service (USFS), under contract AG-8371-D-09-0191, to conduct an Engineering Evaluation/Cost Analysis (EE/CA) and Streamlined Risk Assessment (RA) for two mine sites within the Big Bug Watershed: Money Metals Mine and the Providence Mine (Figure 1). The RA will focus on determining if concentrations of contaminants of potential concern (COPC) or contaminants of potential ecological concern (COPEC) present a risk to human health and the environment that require corrective action. The EE/CA will focus on determining alternatives to eliminate or reduce the potential for release of contaminants from the remains of mining activities within the Site.

The Big Bug Mining District is located in central Arizona in the Prescott National Forest, and consists of several mines located on public and private land. The district is within the Big Bug Watershed, which is part of the Agua Fria sub-watershed in the Middle Gila River Basin. The mining district is located south of Prescott, Arizona on the eastern side of the Bradshaw Mountains within Yavapai County (Figure 1).

Site Investigations

Previous investigations in the Big Bug Watershed include: Characterization of Big Bug Watershed conducted by the USFS in 2002 and a Preliminary Assessment/Site Inspection (PA/SI) for Big Bug Mines conducted by Ecology and Environment, Inc. (E & E) for the USFS in August 2004. Each of these investigations focused on determining which mines in the district have the highest priority for further evaluation and removal action consideration. The two mines concluded to have the highest priority, Money Metals and Providence mines, are the focus of this EE/CA.

Sampling and analyses was conducted as part of this EE/CA to supplement previously collected data. Waste rock/tailings, soil, sediment, and surface water samples were collected.

Primary Sources of Contamination

The primary potential sources of contamination are the waste rock and/or tailings piles that are present at each of the mine site areas.

Summary of Site Risk

Current and previously collected data were evaluated to estimate potential risk to human health and the environment. Data were compared to risk-based human health criteria and ecological criteria identified as applicable or relevant and appropriate requirements (ARARs) or to-be- considered (TBC) requirements to establish potential risk to human and ecological receptors.

The primary human receptors are occasional visitors such as hikers and curious passers-by. Currently, few people explore the mine sites although recent evidence indicates that visitation

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may currently be more frequent. Low numbers of dispersed campers have been reported for Providence Mine by USFS. Potential ecological receptors include local wildlife and vegetation. Grazing cattle and migratory birds using the onsite pond as a water source are additional ecological receptors for the Providence site.

Money Metals Mine

. Surface water – Contaminants were not detected in surface water that exceed any of the applicable human health criteria. Due to the ephemeral nature of surface water at the mine site and based on the current sample results, it is unlikely that metals are present in concentrations that will present a human health risk. Potential risks from cadmium, copper, and zinc to aquatic and wildlife receptors in the unnamed ephemeral drainage are moderate. The distribution of elevated concentrations of potential contaminants appears to be confined to the immediate area surrounding the waste rock pile. Downstream surface water sample results do not indicate that contaminants originating at Money Metals are causing a significant negative impact to overall water quality in the Big Bug Watershed. This evaluation is based on limited available data. Additional surface water data would help refine the evaluation of potential risk.

. Sediment – Elevated concentrations of arsenic above background are present in sediment from the unnamed drainage that flows adjacent to the waste rock pile. Arsenic in sediment collected downstream from the waste rock pile is not elevated indicating the extent of contamination is limited to the area immediately adjacent to the pile. Based on the current and future land use, human exposure to elevated arsenic in sediment at the site would be limited and therefore arsenic concentrations represent a relatively low risk to human receptors. Comparison of the maximum detected concentrations of metals to applicable ecological risk criteria suggests potential risk from lead in sediment is moderate; however, concentrations of lead detected in surface water indicate that lead present in sediment may not be mobile.

. Soil – Analytical results for soil samples collected at Money Metals do not indicate that any of the analyzed metals are present at concentrations that would present a human health or ecological risk.

. Waste rock – Concentrations of arsenic and lead exceed one or more human health ARARs or TBCs. The potential overall risk to the ecosystem from arsenic is likely low, but lead may represent a high to an extremely high risk to the ecosystem. Although concentrations of lead in the waste rock material are elevated, lead does not appear to be mobile based on the low concentrations detected in a surface water sample collected adjacent to the waste rock pile.

Providence Mine

. Surface Water – Only surface water from the pond was sampled. Concentrations of arsenic and thallium exceed primary drinking water standards (i.e., EPA MCLs). The pond is not a source of drinking water and the site is not frequently visited; therefore, it is

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unlikely that water would be consumed in sufficient quantity to result in a risk to human health. Detected concentrations of metals in pond samples do not indicate a potential risk for livestock watering uses. A moderate risk may be present to aquatic life and migratory birds from total selenium based on analytical results of one sample.

. Sediment – Visitation to the site for camping purposes is infrequent and anticipated future land use for the site does not include residential use. Comparison of risk-based action levels set for these intended land uses to concentrations of arsenic detected at the site do not indicate a risk to human health. No other contaminants were detected in sediment at concentrations exceeding potential risk-based human health action levels. Copper in sediment potentially poses a moderate risk to the ecosystem as a whole and a low risk to cattle.

. Soil – Concentrations of metals detected in site soils do not represent a human health or ecological risk.

. Waste Rock/Tailings Material – Several waste rock/tailings piles are scattered throughout the site. Only arsenic was detected at concentrations exceeding any of the applicable human health criteria. Because concentrations of arsenic above the human health criteria for camping are not widespread across the site, and because the site is only infrequently used for camping purposes, concentrations of arsenic detected at the site do not indicate a significant risk to human health. Copper was exceeded at concentrations that present a moderate risk to grazing cattle on the site.

. Groundwater – Copper was detected in the groundwater sample collected on-site; however, the detected concentration does not exceed the EPA MCL for drinking water. Detected concentrations of metals in groundwater do not indicate a potential risk if groundwater is used for livestock watering.

Removal Action Goal and Objectives

The overall goal of potential removal actions at the Money Metals and Providence mine sites is to reduce exposure of humans and ecological receptors to COPCs and COPECs waste rock/tailings areas to levels that do not result in unacceptable site-related risks. The COPCs for Money Metals are arsenic and lead. At Providence, the COPEC is copper. Potential Removal Alternatives

The following removal action alternatives were considered as a part of this EE/CA:

Money Metals Mine . Alternative 1: No Action . Alternative 2: Institutional Controls (with Surface Water Monitoring) . Alternative 3: On-Site Consolidation

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Providence Mine . Alternative 1: No Action . Alternative 2: Institutional Controls . Alternative 3: On-Site Consolidation . Alternative 4: Excavation and Off-Site Disposal

Each of the alternatives was evaluated against the criteria of effectiveness, implementability, and cost. The recommended alternative for both Money Metals and Providence is Alternative 2.

The Money Metals Mine currently does not see much public access traffic and what little there is could be further reduced with proposed institutional controls that would limit public access. The limited data currently available regarding water quality downstream of the waste rock pile does not definitively suggest that there is a water quality problem. Additional monitoring and sampling, identified in Alternative 2, to confirm whether or not there is a water quality issue would be justified before more expensive alternatives are pursued.

The Providence Mine analytical data indicates there is not a significant risk posed to human health from the waste rock piles. Concentrations of copper in some of the waste rock/tailings material are greater than recommended concentrations of copper in soil for grazing livestock. The area currently accommodates cattle grazing and will continue to be available as a resource for this activity. The Alternative 2 Institutional Controls provides the most cost effective means of eliminating the risk to grazing cattle by preventing exposure to affected material.

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1.0 INTRODUCTION

Weston Solutions, Inc. (Weston®) has been contracted by the United States Department of Agriculture (USDA) Forest Service (USFS), under contract AG-8371-D-09-0191, to conduct an Engineering Evaluation/Cost Analysis (EE/CA) and Streamlined Human Health and Ecological Risk Assessment (RA) for a portion of the Big Bug Watershed located in the Bradshaw Mountains of the Prescott National Forest, Yavapai County, Arizona (Figure 1). The USFS is evaluating abandoned mine sites within the Big Bug Watershed per their authority under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The focus of this EE/CA is on two of the mine sites within the overall CERCLA boundary of the site: Money Metals Mine and Providence Mine.

The RA will focus on determining if concentrations of contaminants of potential concern (COPC) present a risk to human health and the environment that require corrective action. The EE/CA will focus on identifying and evaluating alternatives to eliminate or reduce the potential for release of contaminants from the remains of mining activities within the Site.

This EE/CA was prepared following the USFS’s Statement of Work (SOW) (USFS, 2009), discussions with Prescott National Forest representatives, and according to the guidance outlined in the U.S. Environmental Protection Agency’s (EPA) document 540-R-93-057, Guidance on Conducting Non-Time-Critical Removal Actions under CERCLA (EPA, 1993).

1.1 SITE LOCATION AND DESCRIPTION

The Big Bug Mining District is located in central Arizona and consists of several mines located on public and private land. The district is within the Big Bug Watershed, which is part of the Agua Fria sub-watershed in the Middle Gila River Basin. The mining district is located south of Prescott, Arizona on the eastern side of the Bradshaw Mountains in central Arizona within Yavapai County (Figure 1). Previous investigations have focused on determining which mines in the district have the highest priority for further evaluation and removal action consideration. The two mines concluded to have the highest priority, Money Metals and Providence mines, are the focus of this EE/CA.

The Money Metals Mine site is located in Section 32, Township 12.5 N, Range 1 W, Gila and Salt River Base and Meridian (G&SRBM). It is approximately 18 miles south of Prescott and 1¼ miles west of the Poland Tunnel. The Providence Mine is located in Section 26, Township 12.5 N, and Range 1 W G&SRBM, approximately 5 miles west of Poland Junction.

Access to both mines is via Poland Road west at the junction with Highway 69, between Mayer and I-17. Poland Road from its start at Highway 69 to Breezy Pines (formerly Poland) is a well- maintained dirt road that follows the former alignment of the railroad to the Poland Mine. Providence Mine is located just off this road (Figure 1). Money Metals Mine is located off of Big Bug Mesa Road, and can be reached either by continuing along Poland Road, which eventually

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turns into Big Bug Mesa Road, or by taking Walker Road south from Highway 69 in Prescott, Arizona. Big Bug Mesa Road intersects Walker Road.

When traveling to Money Metals Mine west along Poland Road, the road conditions worsen west of Breezy Pines. A four wheel drive (4WD) vehicle is required from Breezy Pines to Five Points and the Big Bug Mesa Road. Money Metals Mine is located at the end of a two-track road that intersects Big Bug Mesa Road, to the south. The two-track road that leads from Big Bug Mesa Road to Money Metals Mine site is extremely rough and is best traveled on foot or possibly on all-terrain vehicle (ATV). It has a steep grade down to Money Metals Mine where the road ends.

1.2 AREA POPULATION

The nearest and most populated towns or cities to the mine sites are Prescott, the county seat of Yavapai county, and Prescott Valley. Prescott and Prescott Valley are approximately 12 miles north to northwest of Money Metals. The nearest communities to the mine sites are Walker, Poland Junction, and Mayer. The small community of Walker is within two miles of the Money Metals Mine site and within five miles of the Providence Mine site. Poland Junction is also a small community and is within five miles east of the Providence Mine site and within six miles of the Money Metals Mine site.

Although the mines are in a rural area there are several homes in the vicinity of each of the mines. During the site visit in September 2009, several homes were observed along Big Bug Mesa Road, which winds through the community of Walker and leads to Money Metals Mine. The community of Breezy Pines is along Poland Road between Money Metals and Providence and consists of mostly summer homes. Houses were also observed from the Providence Mine site. Based on the 2000 census, the estimated populations of these surrounding areas (American Fact Finder, www.factfinder.census.gov) are:

. Prescott – population 33,938 . Prescott Valley – population 36,366

1.3 PHYSICAL CHARACTERISTICS

1.3.1 Geologic and Hydrologic Setting

The Big Bug Mining District is situated in the transition zone between the Basin and Range province to the southwest and the Colorado Plateau to the northeast (Neubert, 1995). The most common rock types in the district include complexly-deformed Precambrian metasediments and volcanic rocks. Originally these rocks were classified as the Yavapai Schist Series but have since been reclassified as the Big Bug Group, which is subdivided into three separate units (Green Gulch Volcanics, Spud Mountain Volcanics, and Iron King Volcanics).

Within the eastern half of the mining district, the dominant rock types are the andesitic breccias and tuffaceous rocks of the lower Spud Mountain Volcanics. The Upper Spud Mountain Volcanics (andesitic and basaltic flows and andesitic tuffs) and Precambrian age gabbros and granodiorites outcrop to the west. Isolated deposits of Tertiary to Quaternary age gravels and

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terrace deposits are present in the main channel of Big Bug Creek. More extensive deposits of younger Quaternary gravels are mapped in Eugene Gulch and in Big Bug Creek at the eastern limit of the mining district (Anderson and Blacet, 1972a, 1972b).

The dominant geomorphic features in the mining district include Mount Elliot to the northeast, Mount Davis at the western divide of the Big Bug Creek Watershed, and the Big Bug Mesa, which forms much of the southern boundary of the watershed. Most of the Big Bug Mesa is capped with thick sequences of Tertiary area basalts (Hickey Formation), which probably inhibits mining operations (Neubert, 1995).

The mineralization of the area likely occurred twice during Precambrian times and again during the Cretaceous-Tertiary period (Neubert, 1995; Anderson and Blacet, 1972a). The geology of the Precambrian ore deposits in the study area is complex, and ore composition can be variable, even within a single deposit. Generally, Precambrian ores primarily consist of massive ore vein sulfide deposits of copper, silver, and gold. Some mines near the study area have also successfully recovered lead and zinc from Precambrian sulfides.

Late Cretaceous to early Tertiary deposits consist mainly of sharply defined gold and silver veins grouped around contemporaneous granodiorites. Quartz tends to be the dominant gangue mineral while sulfide minerals are generally not present in large volumes. However, veinlets of pyrite and chalcopyrite have been identified in the late Cretaceous to early Tertiary granodiorites in Eugene Gulch (Anderson and Blacet, 1972a).

1.3.1.1 Hydrology

The Big Bug Mining District is within the Big Bug Watershed, which is part of the Agua Fria sub-watershed in the Middle Gila River Basin. Two reaches of Big Bug Creek are tributaries to the Agua Fria. The Agua Fria watershed is located in central Arizona to the north and west of Phoenix. The northern reach of the Agua Fria originates within the Prescott Active Management Area (AMA). The Agua Fria River drains an area of approximately 2,700 square miles in Yavapai and Maricopa counties. The watershed boundaries are the Black Hills to the north and northeast, the Humboldt and Maverick Butte Mountains to the east, and the Bradshaw, Hieroglyphic, and White Tank Mountains to the west. The Agua Fria River is perennial at four places above Lake Pleasant with a combined distance of approximately 21 miles.

Big Bug Creek is ephemeral as it flows east through the mining district. An unnamed ephemeral wash provides drainage to the Money Metals Mine which then flows into Big Bug Creek south and east of the mine site.

The Providence site is located north of the confluence of Eugene Gulch and Big Bug Creek. Eugene Gulch is also an ephemeral stream. Three predominant surface flow pathways (ephemeral washes) are present at the Providence Site (Figure 3). The western wash flows through tailings material located east of the pond, eventually draining into Eugene Gulch; the central wash is located east of the access road, eventually draining into Eugene Gulch; and the eastern wash flows through the former placer mining area, also draining into Eugene Gulch.

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1.3.2 Regional Climate

Climate at the Site can be described as moderate. There is a meteorological data station (#026796) at Prescott, Arizona, and monthly climate data is available for the period May 1, 1898 to December 31, 2008. Winter temperatures range from 21˚F to 60˚F, averaging 54˚F during the day. Summer temperatures average 86˚F, ranging between 49˚F to 89˚F. Monthly precipitation generally varies between less than 1.5 inches to over 3 inches, with an annual average of 18.91 inches (WRCC, 2009).

1.4 SITE OPERATION HISTORY AND CURRENT SITE CONDITIONS

The Big Bug Mining District became active in 1863 with the first discovery of gold in the Bradshaw Mountains. The District is considered one of the oldest mining districts in the region and was known for its deposits of gold, silver, copper, lead, and zinc. Gold was present in the form of placer deposits and mercury was used to amalgamate the gold. When the placer deposits became depleted, low-grade sulfide ores were mined and smelting was used to extract the metals. Historical records indicate that the most useful smelter to the Big Bug area would have been the Val Verde Smelting Company in what is now Humboldt (Stein and Skinner, 1997), approximately 4 miles north of Poland Junction. In addition to amalgamation, flotation and heap and vat leaching were used in the watershed to recover metals. Because these processes are not very efficient, high metal residuals can remain in sulfide-rich tailings.

Increased production of copper occurred in the district around 1910, a result of the advent of electricity and the war efforts of World War I. However, except for a brief gold boom in the 1930s most mines were dormant by 1920. Commercial mining in the District ceased in 1969 with the closure of the Iron King Mine.

1.4.1 Money Metals Mine

The unpatented Money Metals Mine, originally called the Bordeaux, was located by Fred Reif in May of 1895. Two adjacent mines were worked alongside Money Metals, the Kaiser and Wilhelm mines. Production from Money Metals included gold, silver, copper, and lead ore.

By 1931, newspaper articles and engineer reports indicate that the Money Metals property consisted of seven unpatented claims covering 3,000 feet along the strike of the vein and a millsite. As of 1920, development at the mine consisted of an incline two-compartment shaft sunk to a depth of 300 feet in the vein and drifting at the 100-, 200-, and 300-foot levels.

In 1929 the Money Metals Exploration Company dewatered the old workings, cleaned out, repaired, and retimbered the shaft and most of the drifts and raises down to and including the 300-foot level. Production in 1929 from the Money Metals property included crude ore, fine gold, fine silver, copper, and lead. A 1934 article in the Skillings’ Mining Review stated that a pilot plant was under construction at the Money Metals property. This statement was supported in a letter from the Bureau of Mines dated August 13, 1943. The letter states that a 10-ton pilot plant was constructed on the property and produced gold bullion, which was sent to the San

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Francisco Mint. A lack of records indicates that the mine was not active after 1939; however, a Prescott partnership reportedly drilled an exploratory hole in 1958 but with negative results (E & E, 2003). In 1999, the site was determined to be eligible for the National Register of Historic Places based on its potential to yield information on the history of mining in Central Arizona (USFS, 2010a).

Money Metals Mine is referred to as Snowdrift Mine on the Poland Junction United States Geologic Survey (USGS) 7.5′ topographic map. Ecology & Environment (E & E) references a Mineral Resource file that mentions Snow Drift Mine as an alternate name for Money Metals (E & E, 2003).

1.4.2 Current Conditions

Currently at Money Metals Mine there are old, metal scraps and remnants of mining equipment including one mid-20th century vehicle (Figure 2). During the September 2009 site visit a second mid-20th century car was observed but during field work in November 2009 the car had been removed (Photograph No. 17, Appendix A). An additional debris pile is located downstream and north of the drainage, near a large-diameter corrugated metal pipe that is in the drainage. On the south side of the site are remnants of a building foundation (reportedly a former bath house) and a large hoist (Photograph Nos. 10, 11, and 12).

In 2000, the USFS closed the inclined shaft, which was located north of the building and hoist area, with a poly-urethane plug and clean cover. During a return visit to the mine site in March 2010, a newly-formed opening (approximately 10 feet in diameter and 6 feet wide) was observed in the location of the previously closed shaft. It is speculated that natural settling of the cover material has occurred forming the opening, and that there has not been a failure in the plug material.

A collapsed vent shaft is located within the mountainside south of the concrete block building (i.e., bath house) remnants (Photograph No. 10). Additional mining prospect pits located 100 feet downstream and on the south side of the wash were reported (E & E, 2004).

1.4.3 Providence Mine

Providence Township developed along Big Bug Creek and was referred to as Big Bug in its earlier days ultimately inheriting the name Providence in 1899 from the Providence Gold Mining Company (E & E, 2003). The Providence Gold Mining Company operated a mine nearby and businesses developed in the area to support the mining operations. Additional producing mines surrounding and supporting Providence included the Oriental, Anne, Red Rock, Belcher, Mammoth, and Fortuna. Little information on the operation of the Providence claim is available other than it was primarily a placer recovery operation that reached peak operations around 1900 (Canty and Greeley, 1987).

By January 1898, Providence supported two general merchandise stores, two barbershops, and four saloons. Between 1899 and 1902 all of the local mines were being worked to full capacity

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and area businesses prospered. At its peak, the township was home to approximately 300 people and had two telephone systems, daily stage service, a railroad, and a post office.

In 1902 after the Poland Branch of the Bradshaw Mountain Railway was complete, residents and business owners began to concentrate their efforts on the nearby town of Poland, Arizona and Providence Township declined (Sayre, 1954; E & E, 2003). The railroad at Providence was used intermittently by small mining companies to ship ore to the mill and smelter in Humboldt (E & E, 2003). The Providence Township decline is well-illustrated by comparing the number of voters during general elections held in Providence in 1902 and 1904. In 1902 there were 100 voters in the general election and in 1904 there were only four (Sayre, 1954).

1.4.3.1 Current Conditions

Today, no evidence of the Providence Township is present. The study area is bounded on the south by Eugene Gulch, which flows into Big Bug Creek approximately 1,800 feet downstream from a small pond present on the south side of the study area (Figure 3). The pond may have once been a production pit although that has not been confirmed (USFS, 2009). A waste rock pile is located upstream from the pond on the south bank of Eugene Gulch. The USFS boundary marker is present at the top of the eastern end of the pile, indicating the pile is partially on private land and partially on USFS-administered land (Photograph Nos. 51 through 55).

Several additional areas of disturbed soil and/or mine tailings material are scattered throughout the site. Two areas of suspected tailings are littered with a significant amount of pyrite scatter. Overhead power lines follow the path of one of these pyrite-enriched disturbed areas (Photograph No. 69, Appendix A).

Black poly-pipe is present east of an unnamed drainage, which flows north to south and eventually into Big Bug Creek (Photograph No. 89, Appendix A). Placer operations reportedly occurred in this wide, flat area as well as upstream from the black poly-pipe location (USFS, 2002). A tin-roofed canopy is present west of the placer mining area and a groundwater well is located near the canopy (Figure 3). A second groundwater well is located northeast of the canopy within the trees.

Arizona Department of Water Resources (ADWR) records indicate the wells were drilled in 1985 for use in mining operations (Photograph No. 79 and 80, Appendix A). The ADWR 55-numbers for these wells are 55-511407 and 55-11409, respectively. Records also indicate the total depth of each well is 300 feet and 405 feet, respectively. Both wells are reportedly equipped with ½-horsepower, centrifugal electrical pumps. The static groundwater level is reported to be 100 feet below ground surface (bgs).

During the November 2009 field work, an open adit was observed on the eastern side of the site, above the drainage that connects the placer mining areas (Photograph Nos. 84, 85, and 86, Appendix A). No other adits or shafts were observed.

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2.0 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS

This EE/CA and risk assessment were developed following the basic methodology outlined in 40 Code of Federal Regulations (CFR) §300.430 and further discussed in the EE/CA Guidance (EPA, 1993). Section 121(d) of the CERCLA requires that removal actions comply with state and federal applicable or relevant and appropriate requirements (ARARs) unless a waiver is justified. ARARs are used to assist in determining the appropriate extent of site cleanup, to scope and formulate removal action alternatives, and to govern the implementation of a selected response action (EPA, 1988 and 1989). The following sections provide a definition of ARARs and describe the ARARs that are site-specific to the Money Metals and Providence Mine sites.

2.1 DEFINITION OF ARARS

ARARs, as defined in CERCLA Section 121(d), are:

. Any standard, requirement, criterion, or limitation promulgated under federal environmental law.

. Any promulgated standard, requirement, criterion, or limitation under a state environmental or facility siting law that is more stringent than the associated federal standard, requirement, criterion, or limitation.

If a state is authorized to implement a program in lieu of a federal agency, state laws arising out of that program constitute the ARARs instead of the federal authorizing legislation. A stringency comparison is unnecessary because state regulations under federally authorized programs are considered federal requirements.

“On-site” with regard to CERCLA removal response actions means the areal extent of contamination and all suitable areas in very close proximity to the contamination necessary for implementation of the response action. On-site actions must comply with ARARs, but must only comply with the substantive requirements of a regulation and not the administrative requirements (CERCLA Section 121(e)(1)). Substantive requirements are those requirements that pertain directly to actions or conditions in the environment. Examples include health-based or risk-based standards for hazardous substances (e.g., maximum contaminant levels [MCLs] in drinking water) and technology-based standards (e.g., Resource Conservation and Recovery Act [RCRA] standards for landfills). Administrative requirements include permit applications, reporting, record keeping, and consultation with administrative bodies, and are not necessary for on-site CERCLA cleanup (Section 121(e)(1)). Although consultation with the state and federal offices responsible for issuing the permits is not required, it is recommended for compliance with the substantive requirements.

Off-site actions must comply only with requirements legally applicable. Off-site actions must comply with both the substantive and administrative parts of those requirements.

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Compliance with employee protection requirements of the Occupational Safety and Health Act (OSHA) is specifically required by 40 CFR §300.150. OSHA standards are not considered ARARs because they directly apply to all CERCLA response actions. In addition, OSHA requirements are more properly viewed as employee protection, rather than environmental requirements, and thus the process outlined in CERCLA Section 121(d) for the attainment or waiver of ARARs does not apply to OSHA standards.

2.1.1 Applicable Requirements

Applicable requirements are those cleanup standards, control standards, and other substantive environmental protection requirements, criteria, or limitations promulgated under federal or state law that specifically address a hazardous substance, pollutant, contaminant, removal action, location, or other circumstance at a National Priority List (NPL) site. “Applicability” implies that the removal action or the circumstances at the site satisfy all of the jurisdictional prerequisites of a requirement, including the part subject to the law, the circumstances or activities that fall under the authority of the law, the time period during which the law is in effect, and the types of activities the statute or regulations require, limit, or prohibit.

2.1.2 Relevant and Appropriate Requirements

Relevant and appropriate requirements are those cleanup standards, control standards, and other substantive environmental protection requirements, criteria, or limitations promulgated under federal or state law that, while not “applicable” to a hazardous substance, pollutant, contaminant, removal action, location, or other circumstance at an NPL site, address problems or situations sufficiently similar (relevant) to those encountered, and are well-suited (appropriate) to circumstances at the particular site. Requirements must be both relevant and appropriate to be ARARs. During the EE/CA process, relevant and appropriate requirements have the same weight and consideration as applicable requirements.

The term “relevant” was included so that a requirement initially screened as nonapplicable because of jurisdictional restrictions could be reconsidered and, if appropriate, included as an ARAR for a given site. For example, MCLs would be not applicable, but would be relevant and appropriate, for a site with groundwater contamination in a potential (as opposed to an actual) drinking water source.

The relevance and appropriateness of a requirement can be judged by comparing a number of factors, including the characteristics of the removal action, the hazardous substances in question, or the physical circumstances of the site, with those addressed in the requirement. The objective and origin of the requirement are also considered. A requirement that is judged to be relevant and appropriate must be complied with to the same degree as if it were applicable. However, it is possible for only part of a requirement to be considered relevant and appropriate, the rest being dismissed if not judged to be both relevant and appropriate in a given case.

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2.1.3 Other Requirements To Be Considered

To-be-considered requirements, or TBCs, are non-promulgated criteria, advisories, guidance, and proposed standards issued by federal or state governments. TBCs are not potential ARARs because they are neither promulgated nor enforceable, however, in many circumstances TBCs are considered along with ARARs as part of the site risk assessment and may be used in determining the necessary level of cleanup for protection of health or the environment (EPA, 1988). Compliance with TBCs is not mandatory, as it is for ARARs.

2.1.4 Waiver of ARARs

According to CERCLA Section 121(d)(4), an ARAR may be waived by EPA, provided protection of human health and the environment is still achieved, under the following six specific conditions:

. The selected removal action is only part of a total removal action that will attain ARARs when completed.

. Compliance with such requirements will result in greater risk to human health and the environment than alternative options.

. Compliance with such requirements is technically impracticable from an engineering perspective.

. The selected removal action will provide a standard of performance equivalent to other approaches required under applicable regulations.

. The requirement is a state requirement that has been inconsistently applied in similar circumstances at other removal actions within the state.

. Attainment of the ARAR would entail extremely high costs relative to the added degree of reduction of risk afforded by the standard such that removal action at other sites would be jeopardized (i.e., fund balancing).

2.2 DEVELOPMENT OF ARARS

Under the description of ARARs set forth in the National Contingency Plan (NCP) and CERCLA, many federal and state environmental requirements must be considered. ARARs and TBCs fall into three broad categories, based on the manner in which they are applied at a site:

. Chemical-specific requirements are health- or risk-based concentration limits or ranges in various environmental media for specific hazardous substances, pollutants, or contaminants.

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. Location-specific requirements are restrictions on activities that are based on the characteristics of a site or its immediate environment. An example would be restrictions on work performed in wetlands or wetland buffers. In this example, the location-specific requirements necessitate restoration of wetlands impacted by removal activities.

. Action-specific requirements are controls or restrictions on particular types of activities, such as hazardous waste management or wastewater treatment. Examples of action- specific requirements would be state and federal air emissions standards as applied to an in situ soil vapor extraction treatment unit.

Chemical-specific, location-specific, and action-specific ARARs and TBCs are all considered in the development and evaluation of removal alternatives. Chemical- and location-specific ARARs typically are identified during scoping of the EE/CA and during the site characterization phase of the EE/CA. Action-specific ARARs are identified during the development of the removal alternatives in the EE/CA.

When an alternative is selected, it must be able to fulfill the requirements of all ARARs (or a waiver must be justified). ARARs pertaining both to contaminant levels and to performance or design standards should be attained at all points of potential exposure, or at the point specified by the ARAR itself. Where the ARAR does not specify the point of compliance, there is discretion to determine where the requirement shall be attained to be protective.

2.3 SITE-SPECIFIC ARARS AND TBCS

The potential chemical-specific ARARs and chemical-specific TBCs for the Site are summarized in Table B1 and Table B2, respectively (Appendix B). Location-specific ARARs are summarized in Table B3. Action-specific ARARs, which are dependent on the remedy selected, are provided in Section 6 for each evaluated alternative and are also presented in Appendix B as Table B4.

Site analytical data was compared to potential chemical-specific ARARs and to applicable risk- based criteria (i.e., TBCs) based on potential human and ecological receptors specific to the Money Metals and Providence Mine sites. The following sections describe the chemical-specific ARARs and provide a rationale for the selection of chemical-specific TBCs for the two mine sites evaluated. A summary of the applicable ARARs and TBCs can be found in Table 1.

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Table 1 Summary of Human Health and Ecological ARARs and TBCs Receptor Media Application Human Health Ecological ADEQ – FBC (Providence) ADEQ A&We (Money Metals) ADEQ – FC (Providence) ADEQ A&Ww (Providence) ARARs Surface ADEQ – AgI (Providence) ADEQ AgL (both Sites) Water ADEQ – PBC (Money Metals) BLM RMC – Camper TBCs None EPA MCLs ARARs ADEQ AWQS None Groundwater EPA MCLs ADEQ AgL (if groundwater were to TBCs BLM RMC – Camper be used for livestock watering) ARARs ADEQ SRL – Non-residential None BLM RMC – Camper BLM RMC – Cattle BLM RMC – Mule Deer Soil, Waste BLM RMC – Robin Rock, and BLM RMC – Median Value Tailings TBCs Eco-SSL – Plants Eco-SSL – Soil Invertebrates Eco-SSL – Avian Wildlife Eco-SSL – Mammalian Wildlife ARARs ADEQ SRL – Non-residential None BLM RMC – Camper (sediment) BLM RMC – Cattle (soil) BLM RMC – Mule Deer (soil) BLM RMC – Robin (soil) Sediment BLM RMC – Median Value (soil) TBCs Eco-SSL – Plants Eco-SSL – Soil Invertebrates Eco-SSL – Avian Wildlife Eco-SSL – Mammalian Wildlife ARAR = Applicable or Relevant and Appropriate Requirements TBC = To Be Considered ADEQ = Arizona Department of Environmental Quality FBC = Full Body Contact FC = Fish Consumption AgI = Agricultural irrigation A&We = Aquatic and wildlife (ephemeral) A&Ww = Aquatic and wildlife (warm water) AgL = Agricultural livestock watering AWQS = Aquifer Water Quality Standard Eco-SSL = EPA Ecological Soil Screening Level MCL = Maximum Contaminant Level EPA = Environmental Protection Agency RSL = Regional Screening Level BLM RMC = Bureau of Land Management Risk Management Criteria PBC = Partial Body Contact

2.3.1 Surface Water

Under section 303 (33 U.S.C. 1313) of the Clean Water Act (CWA), states are required to develop water quality standards for waters of the United States located within their boundaries. Section 303(c) provides that a water quality standard shall include a designated use or uses to be made of the water and criteria necessary to protect those uses. In Arizona, the Arizona Department of Environmental Quality (ADEQ) is the regulatory lead for compliance with the

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CWA. Water quality standards for Arizona are documented in Arizona Administrative Code [A.A.C.] Title 18, Chapter 11, Article 1 (revised and effective January 31, 2009).

ADEQ has set designated uses for Big Bug Creek in each of two separate reaches: 1) from the headwaters to the confluence with Eugene Gulch, which is applicable to Money Metals mine; and 2) below the confluence of Eugene Gulch to the confluence with Agua Fria River, which is applicable to Providence.

The Money Metals site is drained by an unlisted ephemeral tributary to Big Bug Creek. According to A.A.C. R18-11-105(1), “The aquatic and wildlife (ephemeral) (A&We) and partial body contact (PBC) standards apply to an unlisted tributary that is an ephemeral water.” Therefore, the A&We and PBC water quality standards are applicable for Money Metals. Designated uses of Big Bug Creek applicable to Providence are aquatic & wildlife (warmwater) (A&Ww), FBC, FC, AgI, and AgL.

2.3.1.1 Human Health Surface Water ARARs

The Arizona Water Quality Standards (AZ WQS) for the protection of human health at Money Metals are the PBC standards. Based on the Big Bug Creek designated uses near Providence, the FBC and FC standards provide the AZ WQS for that site. Numerical standards for PBC, FBC, and FC designated uses are expressed as total recoverable metals. The regulatory definition of PBC, FBC, and FC are:

. PBC: “…the recreational use of a surface water that may cause the human body to come into direct contact with the water, but normally not to the point of complete submergence (for example, wading or boating). The use is such that ingestion of the water is not likely and sensitive body organs, such as the eyes, ears, or nose will not normally be exposed to direct contact with the water.”

. FBC: “…the use of a surface water for swimming or other recreational activity that causes the human body to come into direct contact with the water to the point of complete submergence. The use is such that ingestion of the water is likely and sensitive body organs, such as the eyes, ears, or nose, may be exposed to direct contact with the water.”

. FC: “…the use of a surface water by humans for harvesting aquatic organisms for consumption. Harvestable aquatic organisms include, but are not limited to, fish, clams, turtles, crayfish, and frogs.”

2.3.1.2 Human Health Surface Water TBCs

TBC requirements for the protection of human health for surface water include the Bureau of Land Management (BLM) Risk Management Criteria (RMC), which were developed for metals typically found at abandoned mine sites as they relate to recreational use and wildlife habitat on BLM lands (Ford, 2004). These criteria are not regulatory or enforceable standards but are

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appropriate for use at the Site. BLM RMC have been developed for select metals in surface water that are protective of human health for potential recreational receptors such as the camper, ATV driver, worker, surveyor, boater, and swimmer. The surface water BLM RMC developed for the camping exposure scenario is applicable to both Money Metals and Providence. Although surface water is not being used for drinking water purposes, the EPA drinking water MCLs will also be considered to provide a conservative estimate of risk.

2.3.1.3 Ecological Surface Water ARARs

The AZ WQS set for A&We, AgI, and AgL are the ARARs for surface water for ecological receptors at Money Metals. The AZ WQS for Providence are A&Ww, A&We, AgI, and AgL. The regulatory definition of each of these uses is as follows:

. A&We: “the use of an ephemeral water by animals, plants, or other organisms, excluding fish, for habitation, growth, or propagation.”

. A&Ww: “the use of a surface water by animals, plants, or other warm-water organisms, generally occurring at elevations less than 5,000 feet, for habitation, growth, or propagation.”

. AgI: “the use of a surface water for crop irrigation.”

. AgL: “the use of a surface water as a water supply for consumption by livestock.”

2.3.1.4 Ecological Surface Water TBCs

TBC requirements include the EPA National Ambient Water Quality Standards (NAWQC). The BLM RMC for surface water for ecological receptors are equal to the NAWQC. The NAWQC are not regulatory criteria but are recommended water quality criteria. Under the CWA, EPA has given states the authority to establish water quality criteria for waters within the state. Because Arizona has set water quality criteria that are law, the NAWQC or the BLM RMC do not provide TBCs that are more appropriate for the Money Metals or Providence site and therefore have not been evaluated.

2.3.2 Groundwater

2.3.2.1 Human Health Groundwater ARARs

The State of Arizona has promulgated aquifer water quality standards (AWQS) for the protection of a drinking water source in A.A.C. R18-11-406. The AWQS constitute the ARARs for groundwater.

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2.3.2.2 Human Health Groundwater TBCs

Although groundwater is not currently used for drinking water purposes, TBC requirements for the protection of human health for groundwater include the groundwater BLM RMC developed for campers. The EPA drinking water MCLs are also TBCs for the Site. Consideration of these criteria will provide a conservative estimate of potential risk if groundwater were to be used for drinking water purposes in the future.

2.3.2.3 Ecological Groundwater ARARs and TBCs

There are no ecological ARARs for groundwater. The Arizona WQS AgL will be applied as a TBC to evaluate potential livestock watering uses for groundwater.

2.3.3 Soil and Waste Rock

2.3.3.1 Human Health Soil ARARs

In general, for soils and waste rock material, the Arizona non-residential soil remediation level (nrSRL) (A.A.C. Title 18, Chapter 7, Article 2) is the ARAR. The SRLs are enforceable standards and are a risk-derived set of values intended to protect human receptors. The Arizona SRL is accepted as the action level for human receptors unless there is compelling evidence to accept one of the TBCs described below.

2.3.3.2 Human Health Soil TBCs

There may be one or more TBC requirements for soil and waste rock material: the EPA Region 9 Regional Screening Levels (RSL) and the BLM RMCs. In the case of the Region 9 RSLs, these risk-derived values are not law and are not considered more protective of human receptors than the Arizona SRLs. They are not more appropriate or relevant to the Site so they are not accepted as action levels for any constituents and have not been evaluated.

The BLM RMC provide numeric criteria for the protection of human and ecological receptors for exposure to certain metals that are frequently detected at abandoned mine sites. Since the BLM RMC are risk-derived values specific to metals at mining sites for recreational exposure scenarios, they are more appropriate and relevant to the Money Metals and Providence sites than the nrSRLs, so they are accepted as action levels for human receptors. The BLM RMC for soil correspond to a generally recognized acceptable level of health risk, specifically an excess cancer risk of 1 x 10-5 or a noncancer hazard index of 1.0. In the case of metals posing both cancer and noncancer threats to health, the lower (more protective) BLM RMC concentration was selected. These risk and hazard levels are consistent with EPA guidance (Ford, 2004). The camper BLM RMC is applicable to both Money Metals and Providence.

th The 95 percentile upper confidence limit (UCL95) of the mean background soil and waste rock concentrations was also calculated for comparison purposes. A.A.C. R18-7-204 allows

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background remediation standards to be developed based on the UCL95 and as such, mean background concentrations are considered TBCs.

2.3.3.3 Ecological Soil ARARs

Since the Arizona SRLs are only for human receptors, they are not applicable for the protection of ecological receptors. There are no state or federal regulatory criteria for soil for the protection of ecological receptors.

2.3.3.4 Ecological Soil TBCs

TBCs for ecological receptors include the BLM Wildlife RMC for metals (available for arsenic, cadmium, copper, lead, mercury, and zinc only) and the EPA Ecological Soil Screening Levels (Eco-SSLs). The BLM Wildlife RMC are consistent with no-effect metal concentrations found for plants, for aquatic life associated with stream sediment, and for soil organisms responsible for fertility and nutrient cycling (Ford, 2004). For wildlife, this model indicates that the majority of the intake for copper, cadmium, mercury, and zinc derives from ingestion of plants; the majority of intake of arsenic and lead derives from soil ingestion. Ecotoxicological effects data for the metals of concern at mining sites, soil-plant uptake factors, representative wildlife receptors, body weights, and soil and plant ingestion rates were used in the calculation of the ecological RMC. Wildlife receptors were selected to represent a range of the types, sizes, and habitats of birds and mammals representative of temperate BLM lands. The selected wildlife receptors evaluated by the BLM are the deer mouse, mountain cottontail, bighorn sheep, white-tailed deer, mule deer, cattle, elk, mallard, Canada goose, trumpeter swan, and the robin.

The BLM Wildlife RMC for the mule deer and the robin represent the lowest (most protective) values for the listed mammal and bird species for which the BLM RMC have been developed. Therefore, the mule deer and robin, along with the BLM RMC cattle, are the chosen criteria for specific species applicable to the Site. BLM RMC for cattle are applicable to the Providence site where approved grazing has been identified as a land use.

In selecting a criterion suitable for protecting groups of species, communities, or ecosystems, the BLM recommends using the median RMC as a point of comparison to Site data. Given the size of the Big Bug watershed, it is appropriate to evaluate the overall risk to the ecosystem as opposed to individual species alone; therefore, site data will also be compared to the BLM RMC median values for the contaminants of potential ecological concern (COPEC) as well as the identified individual species.

The EPA Eco-SSLs are concentrations of contaminants in soil that are protective of ecological receptors that commonly come into contact with soil or ingest biota that live in or on soil. These values can be used to identify those contaminants of potential concern in soils requiring further evaluation in a baseline ecological risk assessment. The Eco-SSLs are not designed to be used as cleanup levels and EPA emphasizes that it is inappropriate to adopt or modify these Eco-SSLs as cleanup standards.

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2.3.4 Sediment

2.3.4.1 Human Health Sediment ARARs

There are no specific state or federal regulatory cleanup standards for contaminated sediments; therefore, the Arizona nrSRLs are applied as the ARARs for sediments.

2.3.4.2 Human Health Sediment TBCs

The BLM RMC for the camper (sediment) and for the worker (sediment) are applied as a TBC.

2.3.4.3 Ecological Sediment ARARs

There are no specific state or federal regulatory cleanup standards for contaminated sediments in regards to ecological receptors; therefore, only TBCs are applicable to this evaluation.

2.3.4.4 Ecological Sediment TBCs

Because the creeks and drainages present within the mining district are intermittent or ephemeral, they do not fully support aquatic life. Therefore, sediment within those drainages will not be evaluated for risk to aquatic organisms. Risk to mammal and avian species will be evaluated by comparing Site concentrations to the BLM RMC for mule deer (soil), robin (soil), cattle (soil), and the wildlife median (soil) as well as the Eco-SSLs for plants (soil), soil invertebrates (soil), avian wildlife (soil), and mammalian wildlife (soil).

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3.0 SOURCE, NATURE, AND EXTENT OF CONTAMINATION

As a result of historic mining activities at the Money Metals and Providence Mines sites, waste rock and tailings piles are present at both sites and debris, such as old vehicles and mining equipment, are present at Money Metals Mine. As a result, potential human and ecological exposure to elevated levels of metals may exist at the mine sites. The source, nature, and extent of contamination at the Site as determined from mine operation history and from previous and current investigations performed at the Site are described in the following sections.

3.1 PREVIOUS INVESTIGATIONS

Previous investigations in the Big Bug Watershed include: Characterization of Big Bug Watershed conducted by the USFS in 2002 and a Preliminary Assessment/Site Inspection (PA/SI) for Big Bug Mines conducted by Ecology and Environment, Inc. (E & E) for the USFS in August 2004. A summary of previously collected data results is presented in Appendix C.

3.1.1 Characterization of Big Bug Watershed

A joint group of USFS specialists including engineers, hazardous material specialists, and geologists developed a plan to characterize the abandoned mines in the Big Bug Watershed that were part of the Big Bug Mining District. The objective was to determine which, if any, of the mines might be contributing to a release of hazardous materials into the soil, water, or air in the area and whether action under CERCLA is warranted. Both the Money Metals and Providence mines were included in the characterization. Based on observations and sampling activities, the report concluded that elevated metals levels and acid producing potential exist at Money Metals and Providence Mines.

3.1.1.1 Money Metals Mine

During the USFS characterization investigation, sampling at Money Metals Mine consisted of one waste rock sample, an environmental sediment sample collected from the unnamed drainage that flows through the site, and one background sediment sample collected from the headwaters of the unnamed drainage (Figure 2). Descriptions of the samples are as follows:

. MM-SL-01: Waste rock sample taken at the edge of the pile.

. MM-SD-1: Sediment sample collected approximately 300 feet from based of the waste rock pile.

. MM-SD-2: Background sediment sample collected above Big Bug Mesa Road in the unnamed drainage.

In the investigation summary report, the sample results were compared to the Arizona residential SRLs (rSRL) and nrSRLs, as well as the mean and maximum background values for metals in Arizona published by ADEQ in 1990. Sample analyses indicate that concentrations of arsenic,

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lead, and selenium in the waste rock sample exceed the mean and maximum Arizona background metals levels as published by ADEQ (1990):

. Arsenic was detected in waste rock (MM-SL-01) at a concentration of 500 milligrams per kilogram (mg/kg) compared to the published mean background concentration of 9.8 mg/kg and the Arizona rSRL and nrSRL of 10 mg/kg (each).

. Lead was detected in waste rock (MM-SL-01) at a concentration of 39,800 mg/kg compared to the average background concentration of 23.4 mg/kg and the Arizona rSRL and nrSRLs of 400 mg/kg and 2,000 mg/kg, respectively.

. Selenium was detected in waste rock (MM-SL-01) at a concentration of 900 mg/kg compared to the average background concentration of 0.3 mg/kg and the Arizona residential rSRL (380 mg/kg).

The concentration of arsenic in the environmental sediment sample (15.4 mg/kg) exceeds the mean Arizona background concentration of 9.8 mg/kg (ADEQ, 1990) in addition to both the rSRL and nrSRL (10 mg/kg each). The waste source sample was also analyzed using synthetic precipitation leaching procedure (SPLP) and for the acid-base accounting (ABA) parameters. The results of the SPLP analysis were consistent with other mines in the district with low SPLP values. The ABA results indicated acid producing potential at the mine site.

3.1.1.2 Providence Mine and Township

Sampling at Providence included two tailings samples, three environmental sediment samples, and one background sediment sample (Figure 3). Descriptions of the sample locations are as follows:

. PVD-SL-1: Tailings sample collected from a large flat area northeast of the pond (Figure 3). Material was multicolored with yellow and brown; strong smell of sulfur present.

. PVD-SL-s: Tailings sample collected from grey material with significant amount of visible pyrite.

. PVD-SD-1: Sediment collected from the east edge of the pond.

. PVD-SD-3: Sediment collected from area that locally drains water from the two tailings sample locations. Sample was collected before this local drainage pathway enters Eugene Gulch.

. PVD-SD-4: Sediment sample collected behind the small dike on the un-named eastern drainage where placer mining was reported to have occurred.

. PVD-SD-5: Background sediment sample collected upstream from PVD-SD-4.

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Sample analyses indicated that concentrations of arsenic are elevated above Arizona statewide mean arsenic concentrations (9.8 mg/kg [ADEQ, 1990]) in both the tailings and environmental sediment samples. In the sediment samples, arsenic was detected at 11.1 mg/kg, 10.4 mg/kg, and 10.1 mg/kg. Mercury was also found at slightly elevated levels in one sample (0.93 mg/kg) where it exceeds both the mean (0.10 mg/kg) and maximum (0.57 mg/kg) statewide Arizona background levels identified by ADEQ (1990).

In the tailings samples, arsenic was detected at 17.9 mg/kg and 20 mg/kg. These concentrations exceed the Arizona mean background level of 9.8 mg/kg (ADEQ, 1990) as well as the non- residential and residential Arizona SRLs (10 mg/kg for each).

3.1.2 Preliminary Assessment/Site Inspection

The USFS tasked E & E to conduct a PA/SI to evaluate five mines in the Big Bug Watershed: Eugene, Money Metals, Providence, Red Rock/Belcher, and Poland mines. The PA/SI concluded that past activities at the mining sites evaluated in the study “have impacted, and continue to impact, the environment”. Their conclusion is based on the following findings:

. Contaminated waste is present at the mining sites, sometimes within 20 feet of the creek.

. There is a suspected release of metals to the waterways at all five sites.

The waste source and surface water pathways at both Money Metals and Providence mines were evaluated as part of the PA/SI. Sampling conducted at Money Metals and Providence mines included waste source, background soil, environmental sediment, background sediment, and environmental surface water (Providence Mine only). Waste source and background soil samples were collected to evaluate the waste source pathway. Environmental sediment, background sediment, and surface water were collected to evaluate the surface water pathway.

Waste source and soil samples were analyzed for the Target Analyte List (TAL) of metals and compared to average background levels, three times the average background levels, and to applicable action levels. Several waste source samples within the district were also analyzed for SPLP and ABA parameters. Surface water and sediment samples were analyzed for TAL metals. Sampled media and corresponding data evaluation criteria can be found in Table 2. The results of the sampling activities at Money Metals and Providence mines are described in greater detail in Section 3.3.

3.2 CURRENT INVESTIGATION

Weston collected additional field data at the Money Metals and Providence Mine sites as part of this EE/CA from November 16 – 20, 2009. The data collected during the current investigation is meant to supplement previously collected data and to aid in the evaluation of risk posed by the two mine sites. Appendix A presents a photographic log of activities and site features observed during the site visits on September 24 and October 22, 2009 and the field sampling effort in November 2009. The total number of samples collected from each mine site is presented in Table

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2 and the analytical parameters for each media are described as listed below. Samples were sent to Columbia Analytical (Columbia) in Phoenix, Arizona for the analyses listed.

. Surface Water Sampling - Total and dissolved metals (arsenic, cadmium, chromium, copper, lead, mercury, selenium, and zinc) (EPA Method 200.7/200.8/245.1) - Hardness (Standard Method [SM] 2340) - Bicarbonate, carbonate, hydroxide, alkalinity (SM 2320B) - Non-filterable total suspended solids (TSS) (SM 2540D) . Groundwater sampling - Total metals (arsenic, cadmium, chromium, copper, lead, mercury, selenium, and zinc) (EPA 200.7/245.1)

. Surface soil and sediment sampling - Total metals (arsenic, cadmium, chromium, copper, lead, mercury, selenium, and zinc) (EPA 6010B/EPA 7471A) - Hexavalent chromium (analyzed only when total chromium exceeds the Arizona rSRL for hexavalent chromium) (EPA Method 3060/7096)

. Waste rock sampling - Total metals (arsenic, cadmium, chromium, copper, lead, mercury, selenium, and zinc) (EPA 6010B/EPA 7471A) - Hexavalent chromium (analyzed only when total chromium exceeds the Arizona rSRL for hexavalent chromium) (EPA Method 3060/7096) - Toxicity characteristic leaching procedure (TCLP) and SPLP (same metals as total metals list) (EPA 1311/6010B) - Paste pH (USDA Ch. 6 Method 21a) - ABA parameters (neutralization potential; organic sulfur, pyritic sulfur, sulfate, total sulfur) (EPA 600/2-78-054-1.31; 2-78-054-3.2.3; and 2-78-054-3.2.4)

Appendix C presents data summary tables of current and previously collected sample analytical results. Analytical results are discussed in Section 4.0. Appendix D presents field sketches of each mine site and field notes detailing all field events. Appendix E presents global positioning system (GPS) coordinates for the sample locations.1 A copy of the analytical laboratory report for the current investigation is presented in Appendix F.

1 GPS data was collected with a handheld Lowrance iFinder H2O GPS unit. The accuracy of this unit is 5 meters or less, depending on satellite coverage and the presence of obstructions (i.e., trees, canyons, etc.) that block the satellite reception. Appendix E presents recorded GPS data; however, some sample locations have been adjusted when plotted on site figures to correct the placement on the map relative to other site features.

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Table 2 Mine Site Planned vs Actual Sample Quantity

Number of Samples Mine Site Sample Status Waste Surface Ground Soil Sediment Rock/Tailings Water Water Planned Locations 6 4 4 4 0 Money Metals Actual Sampled 6 4 4 3 0 Mine Locations Field Duplicates 1 0 0 1 0 Total Money Metals Mine Samples 7 4 4 4 0 Planned Locations 14 5 11 6 1 Actual Sampled 14 3 13 1 0 Providence Mine Locations Field Duplicates 1 0 1 1 1 Total Providence Mine Samples 15 3 14 2 2

Total EE/CA Samples 22 7 18 6 2

Data was collected per the Sampling and Analysis Plan (SAP) prepared for field activities (Weston, 2009). Soil, sediment, and surface water sample locations were biased to provide the highest potential for impact (i.e., adjacent to and downgradient of primary mine features such as waste rock and/or tailings piles).

Waste rock and tailings material samples at each mine site were collected as composite samples based on USGS recommended procedures for characterizing mine waste piles (USGS, 2003). This statistically-based sampling strategy is recommended by the USGS for sampling mine waste to reduce the effects of heterogeneity in the waste material. The procedure includes collection of a 30-increment composite sample from each waste rock pile consisting of dividing the pile into 30 approximately equal sized sections and collecting one scoop of material from each section. This step is followed by sieving to retrieve the <2 millimeter (mm) fraction, and homogenization. There is a tendency for neutralization potential depletion and metal accumulation in the <2 mm fraction when compared with whole-sample data in strongly weathered samples. Hence, collection of the <2 mm fraction provides a worst-case scenario for characterization procedures to determine potential environmental effects. One 30-increment composite sample collected using this sampling strategy contains as much information, relative to the average value, as 30 individual grab samples at 1/30 of the analytical cost.

Due to the large volume of material at Money Metals, waste material was sampled by collecting one 30-increment composite sample from each of six delineated areas in the contiguous pile (MM-WS-1 through MM-WS-6. This sampling design resulted in a total of three composite samples from the top of the waste rock pile and three composite samples from the sides of the waste rock pile, which provided information to determine if the analytical characteristics are

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consistent throughout the pile. At Providence, only one 30-increment composite sample was collected from each pile.

3.2.1 Deviations from the Sampling Plan

The following deviations from the SAP were made during field sampling activities:

. Two soil sample locations at Providence that were planned to be field determined were collected from sediment instead of soil. PM-Sed-12 was collected from the unnamed drainage north and east of the PM-WS-8 and PM-WS-9. PM-Sed-13 was collected south of PM-Sed-4 and just south of Poland Road in the unnamed wash.

. During the November 16 – 18, 2009 sampling event, the observations of the sediment collected from the bottom of the Providence pond indicated a black, organic, “sludgy” material with a slight sulfurous odor. Total organic carbon (TOC) was added to the analyte list for this sample only, based on observations made of the sample material. The laboratory analyzed the sample for TOC but was unable to meet the required hold time so the result is an estimated value.

. During the November 16 – 18, 2009 sampling event, the ephemeral drainages running through Money Metals and Providence were dry; therefore, surface water samples planned in these locations were not collected. Only surface water from the Providence pond was collected.

. The field team remobilized to the Money Metals site on April 6, 2010 when water was flowing in the unnamed ephemeral drainage that flows through that site. Sample locations were adjusted from planned locations presented in the SAP to better identify on-site and downstream conditions. MM-SW-1 (background) was collected in its planned location; however, MM-SW-2 (and its field duplicate) was collected farther downstream but still adjacent to the waste rock pile in order to obtain potential worst-case conditions. MM-SW-3 was located farther downstream, immediately before the confluence with Big Bug Creek to evaluate potential impact to Big Bug Creek attributable to the Money Metals site. As a result of these location changes, surface water and sediment samples were not co-located.

. Money Metals surface water samples collected on April 6, 2010 were analyzed for total and dissolved arsenic, cadmium, copper, lead, and zinc; hardness; and TSS. The list of metals analyzed was adjusted based on those metals with elevated concentrations detected in waste rock samples collected in November 2009.

3.3 EVALUATION OF DISTRIBUTION OF CONTAMINANTS

The distribution of COPCs at the Money Metals and Providence Mine sites is based on evaluation of previously collected data and data collected as part of this EE/CA. Evaluation of

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the potential human health and/or ecological impacts from the COPCs is described in Section 4.0.

3.3.1 Money Metals Site

3.3.1.1 Sediment

Samples were collected upstream (background) and along an approximate 300-foot stretch of the drainage adjacent to and downstream of the waste rock pile. Concentrations of analyzed metals appear to be elevated in sampled sediment adjacent to the waste rock pile when compared to background sediment samples collected upstream (and on the other side of Big Bug Mesa Road); however, concentrations of metals in the farthest downstream sample (MM-S-4) are not significantly different than background.

3.3.1.2 Waste Rock

One waste rock sample collected during the USFS investigation appears to have anomalously high analytical results for several of the analyzed metals (i.e., arsenic, cadmium, copper, lead, mercury, selenium, and zinc). With the exception of this sample, the concentrations of analyzed metals are fairly consistent given the heterogeneity of the material.

Waste rock samples were also analyzed for SPLP and TCLP metals, and for ABA parameters to identify the acid producing and leaching potential of the material to the unnamed drainage and the hazardous waste characteristics for potential off-site disposal. ABA results indicate the waste rock material is potentially acid producing. SPLP results indicate cadmium, copper, and lead may have the potential to leach from the material (Table C3, Appendix C). Both SPLP and TCLP results were highest for lead with TCLP results in two samples exceeding the RCRA TCLP limits for lead of 5 milligrams per liter (mg/L).

3.3.1.3 Surface Water

Surface water samples were collected at Money Metals at three locations within the unnamed drainage (upstream [MM-SW-1], adjacent to the waste rock pile [MM-SW-2 and MM-SW-2d], and downstream [MM-SW-3]) as part of the EE/CA investigation (Figure 4). Surface water was not collected as part of the previous investigations because the ephemeral drainage was dry during each of the earlier investigations.

Alkalinity results of each of the three samples collected, including the background sample, were less than 20 mg/L CaCO3 indicating that surface water in the Money Metals unnamed drainage has very little buffering capacity. Field pH measurements collected during sampling were consistent in the upstream background sample and the downstream samples and ranged between 5.24 and 5.33 standard units. TSS results were low (<3 mg/L at MM-SW-1 and MM-SW-2/2D; and 3 mg/L at MM-SW-3)

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Based on a review of previously collected and newly collected waste rock data, elevated concentrations of arsenic, cadmium, copper, lead, and zinc are present in the waste rock pile at the site. Analytical results of these same metals from sediment collected adjacent to the waste rock pile also appear to be elevated when compared to background concentrations. SPLP and TCLP data indicates that there is a potential for this material to leach; however, surface water results indicate that leaching may not be occurring to a significant degree.

Elevated concentrations of dissolved cadmium (0.0148 mg/L), copper (0.116 mg/L), lead (0.0023 mg/L), and zinc (1.7 mg/L) are present in surface water collected adjacent to the waste rock pile (MM-SW-2 and MM-SW-2D) when compared to background concentrations detected in the upstream sample (MM-SW-1). Although still elevated when compared to background, concentrations of each of these three metals appreciably decrease in the downstream sample (MM-SW-3) collected immediately upstream of the unnamed drainage’s confluence with Big Bug Creek.

The distribution of elevated concentrations of potential contaminants appears to be confined to the immediate area surrounding the waste rock pile. Downstream surface water sample results do not indicate that contaminants originating at Money Metals are causing a significant negative impact to overall water quality in the Big Bug Watershed.

3.3.2 Providence Mine

3.3.2.1 Sediment

Sediment samples were collected from the pond, Eugene Gulch, and three unnamed washes that flow through the site (Figure 3 and Figure 6). The COPCs in sediment are arsenic, copper, and lead (discussed further in Section 4.0). The relative distribution of COPCs in sediment is described below.

. Providence Pond – Previously collected sediment data (PVD-SD-1 and SE/A/1) from the shore indicated arsenic concentrations of 1.66 mg/kg and 4 mg/kg (duplicate result of 4.7 mg/kg). Current data (PM-Sed-2) collected from the center of the pond was less than the detection limit (<5 mg/kg). Copper concentrations ranged from 100 mg/L to 144 mg/L and lead ranged from 5.72 mg/L to 7.6 mg/L. TOC was measured in PM-Sed-2 at 4% and sulfide was measured at 910 mg/kg.

. Unnamed wash (west) – Two sediment samples were collected from the small western drainage (Figure 6). Arsenic was detected in PM-Sed-12 at13 mg/kg. The downstream sample (PV-SD-3 [USFS 2002]) has an arsenic concentration of 11.1 mg/kg. Copper is detected at a concentration of 49 mg/kg and 107 mg/kg, respectively and lead is detected at 7.6 mg/kg and 11 mg/kg, respectively. Lead and copper are not detected above the calculated background UCL95 for those metals.

. Unnamed wash (central) – Two samples were collected from the central unnamed wash (not including background sample PM-Sed-4). PM-Sed-13, collected just south of Poland

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Road, although within the site boundary, is upstream from influences of site activities. The maximum detected concentration of arsenic in sediment at Providence was detected in PM-Sed-13 indicating that off-site influences to arsenic concentrations are most likely present. The concentration of arsenic detected in PM-Sed-13 is 14 mg/kg; copper is 83 mg/kg; and lead is 8.77 mg/kg. The second sediment sample in the central unnamed wash, PM-Sed-5, was collected downstream and north of the confluence between the wash and Eugene Gulch. Concentrations of arsenic, copper, and lead at this location are not appreciably different than the upstream sample: arsenic was detected at 12 mg/kg; copper at 41 mg/kg; and lead at 11 mg/kg. Only arsenic is detected above background levels in the central unnamed wash.

. Eugene Gulch – Four sediment samples (not including background) were collected (Figure 3 and Figure 6). Concentrations of arsenic in sediment within Eugene Gulch ranges from 4.23 mg/kg to 9.6 mg/kg; copper ranges from 63.2 mg/kg to 166 mg/kg; lead ranges from 6.87 to 13.1 mg/kg. Concentrations of these metals appear to increase in downstream samples compared to upstream samples; however, detected concentrations of copper and lead in Eugene Gulch are less than the calculated UCL95 background concentrations for these metals. Concentrations of arsenic in the two farthest downstream samples (SEA2 and PM-Sed-6) are greater than background. These samples were collected after the confluence with the western unnamed wash and the central unnamed wash, respectively. A comparison of arsenic detected in PM-Sed-6 to the upstream concentrations in the western unnamed wash and the central unnamed wash indicates former site activities have most likely not resulted in elevated concentrations of arsenic above background migrating off-site and into the watershed.

. Unnamed wash (former placer mining area) – Six samples (not including background sample PVD-SD-5) were collected in the unnamed wash located on the east side of the site and associated with former placer mining operations. Two of these samples (PM-Sed-9 and PVD-SD-4) as well as the background sample (PVD-SD-5) represent the only sediment samples in which mercury was detected (0.5 mg/kg, 0.93 mg/kg and 0.09 mg/kg, respectively). Concentrations of arsenic in this unnamed wash range from <5 mg/kg to 10.4 mg/kg. The maximum concentration was detected in PVD-SD-4 (USFS, 2002). Copper ranges in concentration from 44 mg/kg to 360 mg/kg and lead ranges from 7.2 mg/kg to 41 mg/kg.

3.3.2.2 Surface Water

With the exception of the pond, surface water on-site is ephemeral. Only water from the pond was available to sample during both the previous investigations and the current investigation. The COPCs for surface water in the pond are arsenic, selenium, and thallium. Field pH measurement of the water was 7.48 standard units.

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3.3.2.3 Soil

Limited non-background soil samples were collected at Providence Mine during all three investigations. Three soil samples identified as background during the PA/SI (SO/B/1, SO/B/2, and SO/B/3). These locations may not be completely out of the influence of historic site activities; therefore, they will be evaluated as site soil samples. No clear distribution of contaminants is evident based on soil sample results. An elevated concentration of lead was detected in sample SO/B/1, which may indicate a localized area of elevated lead.

3.3.2.4 Waste Rock

Several waste rock/tailings areas are scattered throughout the site (Figure 3 and Figure 6). Concentrations of metals above background are detected in material located west of the western drainage (PM-WS-1, PM-WS-2, PM-WS-4, PM-WS-6, and PM-WS-8/9) and in PM-WS-10. Waste rock material noted and sampled near the former placer mining areas does not appear to contain metals in concentrations above background.

ABA results from waste rock/tailings samples collected at Providence indicate the material is potentially acid producing. As indicated previously, the pH of surface water in the pond was measured at 7.48 standard units, indicating that the adjacent waste rock/tailings piles are not negatively influencing that surface water.

SPLP results indicate the highest leaching potential from the waste rock/tailings piles are from copper, chromium, and to a lesser degree lead. Only copper was detected in TCLP leachate. None of these metals were detected in the pond sample at a concentration greater than Arizona water quality standards again indicating that the waste rock/tailings piles adjacent to the pond are not adversely affecting water quality.

3.3.2.5 Groundwater

Groundwater was sampled in one of the two on-site wells and analyzed for arsenic, cadmium, chromium, copper, lead, mercury, selenium, and zinc. These metals were selected for analysis based on their presence in waste source (tailings or waste rock) samples. Only copper was reported above the laboratory method detection limit (0.028 mg/L and 0.025 in the field duplicate).ADEQ has not established an AWQS for drinking water protected use. The EPA MCL for copper, which is a treatment standard as opposed to a health standard, is 1.3 mg/L.

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4.0 EVALUATION OF RISK

A streamlined risk evaluation process was used to assess the threats to human health and the environment associated with exposure to contaminated surface water, groundwater, soil, waste rock, tailings and sediment at the Site. The Streamlined RA was completed by identifying COPCs and contaminants of COPECs and comparing their concentrations to potential ARARs and/or risk-based chemical concentrations.

4.1 DATA REVIEW

Analytical data from the RPA, USFS sampling effort, and current sampling efforts have been tabulated and compared to potential action levels (ARARs and TBCs) and available background concentrations to identify the COPCs for the Site. The selection of ARARs and TBCs was presented in Section 2.0. Tabulated analytical data collected during previous investigations and the current investigation, accompanied by the appropriate ARARs and TBCs, are summarized in Appendix C as follows:

. Table C1 – Money Metals Mine Sediment, Soil, and Waste Rock Analytical Results . Table C2 – Money Metals Mine Surface Water Analytical Results . Table C3 – Money Metals Mine SPLP and TCLP Analytical Results . Table C4 – Providence Mine Initial Sediment, Soil, Waste Rock Analytical Results . Table C5 – Providence Mine Surface Water and Groundwater Analytical Results . Table C6 – Providence Mine SPLP and TCLP Analytical Results . Table C7 – Money Metals Mine and Providence Mine ABA Analytical Results

4.1.1 Initial Chemical Data Screening

The Site metals data were initially screened using the following criteria to eliminate metals that contribute de minimus risk to humans and ecological receptors.

Essential nutrients: Calcium, magnesium, potassium, and sodium were removed from further assessment in soil, sediment, waste rock, and surface water because they are considered essential nutrients.

Frequency of Detection: Contaminants detected in fewer than 5% of the samples for a given media at each mine site were eliminated from further screening. Results for waste rock and tailings were combined and treated as a single medium.

Background: COPCs for which the maximum measured concentrations in Site samples occurred th at concentrations less than the 95 percentile upper confidence limit (UCL95) for surface water, soil/waste rock/tailings, and sediment were eliminated from further evaluation.

The data set used to calculate the background soil UCL95 for Money Metals consisted of background data at Poland Mine and Money Metals collected during the PA/SI and additional

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background sample data from Money Metals Mine collected as part of the EE/CA sampling. The two mines are located in geologically similar areas such that it is appropriate to combine data to determine background metal concentrations. The sediment background UCL95 was calculated using data collected during the USFS 2002 investigation, the PA/SI, and the current EE/CA investigation.

The background soil UCL95 for Providence was calculated using soil data collected during the PA/SI at Eugene Mine, Red Rock Mine, and Providence Mine as well as data collected from Providence during the current EE/CA investigation. Background sediment data includes results from samples collected from Providence, Eugene, and Red Rock Mines during the USFS 2002 investigation, the PA/SI, and additional sediment data from Providence collected during the current EE/CA investigation. Each of these three mines was determined to be geologically similar such that it is appropriate to combine data to determine background metal concentrations. Combining background data for similar mines provides a larger sample size to provide for a more meaningful UCL95 calculation.

Initial ARAR/TBC Review: Metals not screened out for one of the above reasons were compared to the list of human health and ecological ARARs and TBCs. If the maximum detected concentration of a metal was less than the most stringent ARAR or TBC, the metal was eliminated from further review. The list of human health ARARs and TBCs included in the initial review is shown below. Although not an ARAR or TBC for either site, data will be compared against the Arizona rSRLs to establish a lower bound

. Arizona nrSRL (sediment, soil, waste rock, tailings) . Arizona rSRL (sediment, soil, waste rock, tailings) . BLM RMC Camper – Sediment (sediment, soil, waste rock, tailings) . BLM RMC Camper – Soil (sediment, soil, waste rock, tailings) . Arizona WQS PBC (surface water – Money Metals only) . Arizona WQS FBC (surface water – Providence Mine only) . Arizona WQS AgI (surface water – Providence Mine only) . Arizona WQS FC (surface water – Providence Mine only) . BLM RMC Camper (surface water) . Arizona WQS Groundwater – Drinking Water Protected Use (groundwater) . EPA National Primary Drinking Water Standards MCL (groundwater) . BLM RMC Groundwater – Resident (groundwater) . BLM RMC Groundwater – Camper (groundwater)

Initial ecological ARARs and TBCs evaluated include:

. BLM RMC Mule deer (sediment, soil, waste rock, tailings) . BLM RMC Cattle (sediment, soil, waste rock, tailings) . BLM RMC Robin (sediment, soil, waste rock, tailings) . RLM RMC Wildlife Mean Value (sediment, soil, waste rock, tailings) . Arizona WQS A&We acute (surface water, Money Metals only) . Arizona WQS AgL (surface water, Providence Mine only) . Arizona WQS A&Ww acute and chronic (surface water, Providence Mine only)

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. EPA Eco-Soil Screening Levels (SSL) Plants (sediment, soil, waste rock, tailings) . EPA Eco-SSL Soil Invertebrates (sediment, soil, waste rock, tailings) . EPA Eco-SSL Wildlife Avian (sediment, soil, waste rock, tailings) . EPA Eco-SSL Wildlife Mammalian (sediment, soil, waste rock, tailings)

In the natural environment, chromium occurs in two oxidation states, trivalent chromium and hexavalent chromium. Of the two forms, hexavalent chromium is the more toxic to human health and thus has more conservative (i.e., stringent) action levels than trivalent chromium. To provide the most conservative screening value, the hexavalent chromium SRLs are used in the initial ARAR/TBC review. The more conservative chromium Eco-SSLs are those for trivalent chromium; therefore, these values were used in the initial ecological ARAR/TBC review. During analysis of samples collected as part of the EE/CA investigation, any samples with total chromium concentrations greater than the hexavalent chromium SRL, were subsequently analyzed for hexavalent chromium to determine if an exceedance of the SRL occurred.

Results of the initial data screening for metals are presented in Appendix G. Table G1 presents screening results based on frequency of detection and background concentrations for Money Metals Mine. Table G2 presents the initial Money Metals ARAR/TBC review for human health and Table G3 presents the screening review for the initial Money Metals ARAR/TBC review for ecological receptors. Initial data screening tables for Providence Mine are presented in Tables G4 through G6.

4.2 STREAMLINED HUMAN HEALTH RISK ASSESSMENT

The streamlined human health risk assessment was prepared to assess the potential hazards and risks to human receptors from exposure to mine waste and potentially contaminated media at Money Metals and Providence Mine sites. This evaluation compares analytical data from the 2002 USFS sampling effort, the 2003 E&E PA/SI sampling effort, and current sampling efforts to potential chemical-specific ARARs and applicable risk-based values for human receptors based on the current and anticipated future land use. Initial review of Site data compared to ARARs and TBCs was completed as described in Section 4.1.1. The COPCs for human health risks remaining after initial data screening are listed below.

At Money Metals Mine the COPCs for human health risks for each media remaining after initial data screening are:

. Surface water – none . Sediment – arsenic . Soil – none . Waste rock and tailings – arsenic, iron, lead, selenium, and thallium

At Providence Mine the COPCs for human health risks for each media remaining after initial data screening are:

. Surface water – arsenic, thallium . Sediment – arsenic

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. Soil – lead . Waste rock and tailings – arsenic and chromium . Groundwater – copper

4.2.1 Exposure Assessment

A Site Conceptual Exposure Model (SCEM), described below, was developed for the Site and is included in Appendix H.

4.2.1.1 Contaminant Sources

The primary sources of potential contamination at Money Metals and Providence Mines are the waste rock and/or tailings piles associated with each of the individual mine site areas.

4.2.1.2 Release Mechanisms

The primary release mechanisms for potential contaminants include:

. Physical erosion . Leaching . Overland runoff . Wind erosion . Uptake

4.2.1.3 Potential Receptors

Potential receptors for the Site are based on the current and future land use of the Site. The primary human receptors are occasional visitors such as hikers and curious passers-by. Currently, few people explore the mine sites although recent evidence indicates that visitation may be more frequent lately. Low numbers of dispersed campers have been reported for Providence Mine by USFS. During the 2009 sampling effort Weston personnel noted that the mid-century vehicle previously located at Money Metals Mine during the September 2009 site visit had been removed.

The envisioned future use of both mine sites is restoration to the natural environment including the closure of both access roads that lead to the mine sites. Due to the access road closures, visitation to the sites in the future should be minimal and sensitive receptors such as young children, the elderly, and pregnant women are not likely visitors but are possible. Should removal actions take place at the Site or mining-related activities resume, the workers involved in those activities will also be potential receptors.

4.2.1.4 Exposure Media

The environmental exposure media include:

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. Sediment . Waste rock, tailings, and soil . Surface water . Groundwater

The stock pond at Providence Mine is used for agricultural water only and there are no surface water intakes for drinking water at either mine site. The groundwater wells at Providence mine are not in use at this time and therefore, represent an incomplete exposure pathway.

4.2.1.5 Exposure Route(s)

The primary exposure route for human receptors is incidental ingestion and inhalation of dust. Dermal contact of the contaminants is not considered a significant exposure route for the primary receptors.

4.2.2 Evaluation of Human Health Risk

The discussion of potential human health risks presented in this document has been organized by individual mine site and environmental media in the subsections below. As discussed in Section 4.1.1, the maximum detected concentration of each analyzed contaminant was compared to the calculated background UCL95 and identified ARARs and TBCs for each contaminant to eliminate contaminants that were not detected above any of the human health criteria. The following sections discuss the individual mine sites and the corresponding human health COPC for each media sampled following the initial data screening.

4.2.2.1 Money Metals Mine

Previous field work at Money Metals Mine consists of sediment, soil, and waste material sample collection during the USFS 2002 sampling event and the E&E 2003 sampling event. The current sampling effort consisted of surface water, sediment, soil, and waste material samples. The COPC for each media at Money Metals Mine are discussed in the following sections.

4.2.2.1.1 Surface Water

Surface water at Money Metals Mine is ephemeral and was not present during previous sampling efforts and therefore surface water was not sampled. During the current investigation, three surface water samples were collected from the unnamed drainage that flows through the mine area: one upstream background sample, one sample adjacent to the waste rock pile, and one sample downstream from the site near the confluence of the unnamed drainage and Big Bug Creek. Surface water samples were analyzed for total and dissolved arsenic, cadmium, copper, lead, and zinc; hardness; alkalinity; and TSS.

Analytical results of each of the three samples and the field duplicate do not indicate an exceedance of any applicable water quality standard for the protection of human health for any of the metals analyzed. Arsenic was not detected above the laboratory reporting limit (<0.003

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mg/L) in any sample; total cadmium ranged from <0.0020 to 0.0145 mg/L compared to the PBC of 0.7 mg/L; total copper ranged from 0.0119 to 0.144 mg/L compared to the PBC of 1.3 mg/L; total lead ranged from 0.0028 to 0.0081 mg/L compared to the PBC of 0.015 mg/L; and total zinc ranged from 0.15 to 1.7 mg/L compared to the PBC of 280 mg/L.

4.2.2.1.2 Sediment

A total of seven sediment samples from the mine site, plus three background sediment samples, were collected as part of the 2002 USFS sampling effort, 2003 E&E PA/SI sampling effort, and the current sampling effort. Following the initial data screening and ARAR/TBC review, the COPC for sediment at Money Metals Mine was determined to be arsenic.

Sediment samples collected from the unnamed drainage adjacent to the waste rock pile during the current and previous investigations range from 11.4 mg/kg to 16 mg/kg. Arsenic was detected in sediment collected downstream from the waste rock pile (MM-Sed-4) at 6.7 mg/kg. The Arizona rSRL and nrSRLs are both 10 mg/kg, the BLM RMC for sediment for the camping exposure scenario is 46 mg/kg, and the BLM RMC for soil for the camping exposure scenario is 20 mg/kg. The mean arsenic background concentration in sediment is 6.0 mg/kg. A UCL95 was not calculated for sediment background samples because only three background samples were collected.

4.2.2.1.3 Soil

Three soil samples were collected from Money Metals Mine as part of the current sampling effort. Six soil samples collected as part of the previous investigations and one sample collected during the current investigation are representative of background conditions.

No COPCs for soil are indicated following the initial data screening and ARAR/TBC review. Analytical results for the three site soil samples collected during the current investigation for each of the metals analyzed are below human health criteria or the calculated UCL95 for background concentrations.

4.2.2.1.4 Waste Material

A total of nine waste rock samples and one field duplicate were collected at Money Metals as part of the 2002 USFS sampling effort, 2003 E&E PA/SI sampling effort, and the current sampling effort. Following the initial data screening and ARAR/TBC review, the COPC for waste material at Money Metals Mine were determined to be arsenic, iron, lead, selenium, and thallium. Analytical results for waste rock samples are compared to the UCL95 for background soil, the rSRLs and nrSRLs, and the BLM RMC for the camper.

Detected concentrations of arsenic in waste rock ranged from 57 mg/kg to 500 mg/kg. Each of the samples collected during the previous investigation and the current investigation exceed the calculated background UCL95 for arsenic in soil (9.6 mg/kg); the Arizona rSRL and nrSRL (both 10 mg/kg); and the BLM RMC for the camper (20 mg/kg). The waste rock sample collected during the USFS 2002 sampling effort (MM-SL-01) showed a significantly higher arsenic

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concentration (500 mg/kg) than samples collected during the PA/SI (maximum 196 mg/kg) and the current investigation (maximum 81 mg/kg) and may be anomalously high.

Detected concentrations of lead in waste rock samples ranged from 230 mg/kg to 39,800 mg/kg. Concentrations of lead detected in each of the seven collected waste rock samples exceed the lead background UCL95 (43 mg/kg). Lead concentrations in six of the seven collected samples exceed the Arizona rSRL (400 mg/kg), the Arizona nrSRL SRL (800 mg/kg), and the BLM RMC for the camper (1,000 mg/kg).

Selenium was detected in one out of seven waste rock samples at a concentration of 900 mg/kg. Although this value exceeds the Arizona rSRL (390 mg/kg) and the BLM RMC for the camper (700 mg/kg), the detection appears to be anomalous. Only one other collected waste rock sample yielded a detectable concentration of selenium (1.37 mg/kg) and analytical results for the remaining five collected waste rock samples were below the selenium detection limit.

Thallium was detected at a concentration of 8.05 mg/kg in one sample, which exceeds the rSRL for thallium of 5.2 mg/kg. Only one other waste rock sample was analyzed for thallium. The analytical result for that sample was below detection.

4.2.2.1.5 Money Metals Human Health Risk Conclusions

The future envisioned use for Money Metals Mine is a return to the natural environment. Current access to the site is not restricted and evidence of human visitation has been observed. No direct evidence of camping at the mine site has been observed; however, camping is not specifically forbidden at the site and could be possible. The following provides a summary of risk to humans from contaminants at the site.

. Surface water – Contaminants were not detected in surface water that exceed any of the applicable human health criteria. Due to the ephemeral nature of surface water at the mine site and based on the current sample results, it is unlikely that metals are present in concentrations that will present a human health risk.

. Sediment – Elevated concentrations of arsenic above background are present in sediment from the unnamed drainage that flows adjacent to the waste rock pile. Arsenic in sediment collected downstream from the waste rock pile is not elevated indicating the extent of contamination is limited to the area immediately adjacent to the pile. Although arsenic sediment concentrations near the pile exceed the Arizona rSRL and nrSRL of 10 mg/kg, the concentrations do not exceed the BLM RMC for sediment or soil for the camper exposure scenario (20 and 46 mg/kg, respectively). Based on the current and future land use, human exposure to elevated arsenic in sediment at the site would be limited and therefore arsenic concentrations represent a relatively low risk to human receptors.

. Soil – Analytical results for soil samples collected at Money Metals do not indicate that any of the analyzed metals are present at concentrations that would present a human health risk.

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. Waste rock – Concentrations of arsenic, lead, selenium, and thallium in waste rock samples collected at Money Metals mine exceed one or more human health ARARs or TBCs.

— Based on the entire data set of analytical results for selenium, the elevated concentration of selenium detected in one sample appears to be anomalous. It is unlikely that concentrations of selenium in waste rock at the site present a human health risk.

— An elevated concentration of thallium was detected in one sample above the rSRL for thallium of 5.2 mg/kg but does not exceed the nrSRL of 67 mg/kg. Current and future land uses for the site do not include residential land uses. Because the site is not currently used for residential purposes and residential use is not included in the foreseeable future, thallium does not appear to present a human health risk.

— Analytical results of waste rock samples collected at the site indicate that concentrations of arsenic and lead pose a potential human health risk.

The final COPC for Money Metals Mine based on the above human health risk evaluation are arsenic and lead in waste rock.

4.2.2.2 Providence Mine and Township

Previous field work at Providence Mine during the USFS 2002 sampling event and the E&E 2003 sampling event consists of the collection of sediment, soil, waste material, and surface water samples from the pond. Previous sample locations are shown on Figure 3. Current sampling efforts at the mine consisted of sediment, soil, waste material, surface water (pond), and groundwater sample collection. Current sample locations are shown on Figure 6. Eugene Gulch and the unnamed streams flowing through the site are ephemeral; water was not present during the EE/CA sampling activities preventing the collection of surface water other than at the pond.

4.2.2.2.1 Surface Water

Two surface water samples and two field duplicates were collected from the pond at Providence Mine during the 2003 E&E PA/SI sampling event and during current sampling efforts. Following the initial data screening and ARAR/TBC review, arsenic and thallium are considered COPC for surface water at Providence Mine. Due to the ephemeral nature of surface water in the area, no background surface water data is available for Providence Mine.

Arsenic is considered a COPC because its concentration in sample SW/A/1 (0.223 mg/L) collected during the PA/SI is greater than the drinking water EPA MCL for arsenic of 0.01 mg/L and the BLM RMC for the camping scenario of 0.001 mg/L. Analytical results of the sample collected during the current investigation were less than the detection limit of 0.01 mg/L. Thallium was not analyzed in surface water during the current investigation; however, thallium was detected in SW/A/1 collected during the PA/SI at 0.0538 mg/L. This exceeds the Arizona

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WQS for FC (0.001 mg/L), the Arizona AWQS of 0.002 mg/L, and the EPA drinking water MCL of 0.002 mg/L.

The pond is not currently used as a drinking water source and no evidence exists to indicate the pond is being used as a fishery. Vehicular access to the site is through a gated road and therefore somewhat restricted. Foot access is available if one wished to hike through Eugene Gulch. Low numbers of dispersed campers are thought to visit the site. Due to the low usage of the site, it is unlikely that water from the pond would be ingested in sufficient quantity to result in a human health risk.

4.2.2.2.2 Sediment

A total of 17 sediment samples, plus two field duplicates, and six background sediment samples were collected from Providence Mine as part of the 2002 USFS sampling effort, the 2003 E&E sampling effort, and the current sampling effort. Sediment was collected from the on-site pond, Eugene Gulch, and the two unnamed ephemeral washes that flow through the site (placer mining operations have reportedly occurred in the unnamed wash located at the eastern site boundary)Previous pond sediment samples were collected near the shore. The pond sediment sample collected as part of the current investigation was collected from the center of the pond.

Following initial data screening and ARAR/TBC review, the COPC for sediment at Providence is arsenic. Arsenic in sediment ranges in concentration throughout site from 1.66 mg/kg to 14 mg/kg. The sediment background UCL95 relative to the Providence site for arsenic is 8.5 mg/kg. The Arizona rSRL and nrSRLs are both 10 mg/kg, the BLM RMC for sediment for the camping exposure scenario is 46 mg/kg, and the BLM RMC for soil for the camping exposure scenario is 20 mg/kg. Concentrations of arsenic in only five sediment samples (PVD-SD-3, PVD-SD-4, PM- Sed-5, PM-Sed-12, PM-Sed-13) exceed the Arizona SRLs; arsenic concentrations in none of the sediment samples exceed the BLM RMC.

4.2.2.2.3 Soil

Four soil samples were collected at Providence Mine during previous and current sampling events that represent non-background conditions. During the PA/SI, samples SOB1, SOB2, and SOB3 were collected west of the placer mining area (Figure 3). These samples were designated as background samples at the time; however, based on their location relative to site features, this designation seems to be inappropriate and therefore will be evaluated as site samples. All other designated background soil samples during previous investigations and the current sampling effort are representative of background conditions.

Lead is the only indicated COPC for soil following the initial data screening and ARAR/TBC review. Analytical results of lead for sample SO/B/1 are 582 mg/kg. This sample was the only sample where the lead concentration exceeds the Arizona rSRL of 400 mg/kg; the Arizona nrSRL of 800 mg/kg and the BLM RMC for the camper of 1,000 mg/kg are not exceeded.

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4.2.2.2.4 Waste Material

A total of 19 waste source samples, plus one field duplicate, were collected from Providence site. Following the initial data screening and ARAR/TBC review the COPC for waste material at Providence Mine are arsenic and chromium. Analytical results for waste rock samples are compared to the UCL95 for background soil, the rSRLs and nrSRLs, and the BLM RMC for the camper exposure scenario.

Detected concentrations of arsenic in waste source material range from <5 mg/kg to 25 mg/kg. Arsenic exceeds the UCL95 background concentration of arsenic (13.6 mg/kg) and the Arizona rSRL and nrSRL (both 10 mg/kg) in six out of the 19 collected samples. Analytical results of two samples exceed the BLM RMC for the camper (20 mg/kg). Results relative to specific waste piles, as identified by the current investigation sample effort, exceeding one or more human health criteria or the background UCL95 for arsenic are discussed below. Waste piles not included in the list below did contain arsenic concentrations greater than the UCL95 and/or greater than any of the human health criteria.

. PM-WS-1 (located in Eugene Gulch west-northwest of the pond) – one sample (WSA3) was collected during the PA/SI and one sample (PM-WS-1) was collected during the current investigation. Arsenic results were 11.1 mg/kg and 25 mg/kg, respectively.

. PM-WS-6 (located east-northeast of the pond) – one previously collected sample (PVD- SL-2) and one current sample (PM-WS-6) were collected. Concentrations of arsenic detected in these samples are 20 mg/kg and 7.3 mg/kg, respectively.

. PM-WS-8 and PM-WS-9 (located north of the pond) – two samples collected during the current sampling efforts contained arsenic at concentrations of 13 mg/kg and 14 mg/kg.

. PM-WS-12 (located northeast of the pond) – three samples were collected in this area; one during each of the previous investigations and one during the current investigation. Arsenic concentrations range from 14.5 mg/kg to 17.9 mg/kg. These samples were collected in an area of scattered tailings material that covers the ground surface.

Total chromium was analyzed in each collected sample. If total chromium results exceeded the Arizona rSRL for hexavalent chromium (30 mg/kg) in any given sample, that sample was further analyzed to determine the hexavalent chromium concentration. Twelve waste source samples had concentrations of total chromium that exceeded the rSRL for hexavalent chromium. Subsequent analysis of these samples indicated concentrations of hexavalent chromium ranged from <0.49 mg/kg to 2.0 mg/kg, which is well below the applicable human health criteria.

4.2.2.2.5 Groundwater

One groundwater samples, plus one field duplicate, were collected during the current sampling efforts from ADWR number 55-511407, the southern-most well onsite. No background groundwater data is available for the Providence Mine area. Therefore, groundwater analytical

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results were compared to the applicable ARARs and TBCs only. After initial ARARs and TBC screening, the COPC for groundwater at Providence Mine is copper.

Copper was detected at a concentration of 0.028 mg/L. Arizona does not regulate the concentration of copper in groundwater and the detected concentration is significantly less than the federally enforceable drinking water EPA MCL of 1.3 mg/L. Copper is considered a COPC for groundwater based on the exceedance of the groundwater BLM RMC for a resident (0.018 mg/L). The BLM RMC (camper scenario) is 0.137 mg/kg. Currently, there are no residences on- site and groundwater is not being used for drinking water.

4.2.2.2.6 Providence Mine and Township Human Health Risk Conclusions

Although not an officially designating camping area, current land use includes low usage camping and cattle-grazing. The future envisioned use for Providence Mine is a return to the natural environment with increased restrictions on access and continued cattle-grazing. The following provides a summary of risk to humans from contaminants at the site.

. Surface Water – Only surface water from the pond was sampled. Concentrations of arsenic and thallium exceed primary drinking water standards (i.e., EPA MCLs). The pond is not a source of drinking water and the site is not frequently visited; therefore, it is unlikely that water would be consumed in sufficient quantity to result in a risk to human health.

. Sediment – Arsenic was detected in five samples (out of 16 collected) at a concentration exceeding the Arizona rSRL (10 mg/kg). None of those samples exceeding the rSRL exceed the BLM RMC for the camper in sediment (46 mg/kg) or the BLM RMC for the camper in soil (20 mg/kg). Visitation to the site for camping purposes is infrequent and anticipated future land use for the site does not include residential use. Comparison of risk-based action levels set for these intended land uses to concentrations of arsenic detected at the site do not indicate a risk to human health. No other contaminants were detected in sediment at concentrations exceeding potential risk-based human health action levels.

. Soil – Lead was detected in one soil sample (SO/B/1), out of six collected soil samples, at a concentration (582 mg/kg) that exceeds the Arizona rSRL of 400 mg/kg; however, this concentration does not exceed the Arizona nrSRL (800 mg/kg) or the BLM RMC for the camper (1,000 mg/kg). Because land use of the site is not currently residential, nor is residential land use planned in the future, comparison of site concentrations to the rSRL is ultra-conservative. Based on the intended future land uses, concentrations of lead in soil do not present a significant human health risk.

. Waste Rock/Tailings Material – Several waste rock/tailings piles are scattered throughout the site. Only arsenic was detected at concentrations exceeding applicable human health criteria. Arsenic was detected in nine samples out of 19 collected at concentrations exceeding the Arizona rSRL (10 mg/kg). Only two of those nine samples equal or exceed the BLM RMC for the camper (20 mg/kg): PM-WS-6 located east of the

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pond area and PM-WS-1 located within Eugene Gulch that straddles private and USFS- administered land (Figure 6). Visitation to the site for camping purposes is infrequent and anticipated future land use for the site does not include residential use. Because concentrations of arsenic above the human health criteria for camping are not widespread across the site, and because the site is only infrequently used for camping purposes, concentrations of arsenic detected at the site do not indicate a significant risk to human health.

. Groundwater – Copper was detected in the groundwater sample collected on-site; however, the detected concentration does not exceed the EPA MCL for drinking water.

4.3 STREAMLINED ECOLOGICAL RISK ASSESSMENT

A streamlined ecological risk assessment (ERA) was completed to assess potential risks to ecological receptors at the Site from exposure to mine waste and contaminated media at the Site. The streamlined ERA consists of:

. Identification of the Site ecological setting, sensitive environments, and threatened, endangered or sensitive (TES) species

. Development of an ecological SCEM

. Comparison of Site analytical data to available ecological risk criteria

4.3.1 Ecological Setting

Potential ecological receptors include local wildlife and vegetation. Grazing cattle and migratory birds using the pond as a water source are additional ecological receptors for the Providence site. Money Metals and Providence Mines are located within the Arizona Game and Fish Department (AZGFD) Game Management Unit 20A. Game species identified in that area include mule deer, javelina, mountain lion, Gambel’s quail, and tree squirrel; all of which have been observed in the project area. Other wildlife specifically identified near Money Metals includes black bear, fox, raccoon, ringtail cat, coyote, wild turkeys, and woodpecker (http://walkerfire.org/WildLife.html). Dominant trees in the Big Bug Watershed are ponderosa pine at the higher elevations, and scrub oak, pinyon-juniper at lower elevations.

The relevant U.S. Fish and Wildlife Service (USFWS) listed threatened and endangered species (TES) protected under the Endangered Species Act (ESA) and designated USFS sensitive species are presented below. The preliminary TES and USFS sensitive species list (and the potential for occurrence at either site per the USFS wildlife biologist [USFS, 2010b]) includes:

. Northern Goshawk (Accipiter gentilis): USFS sensitive – may occur within the project areas

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. Mexican Spotted Owl (Strix occidentalis lucida): ESA threatened, USFS sensitive – Money Metals lies within identified critical habitat

. Eastwood Alum Root (Huechera eastwoodiae): USFS sensitive – could potentially occur at the Money Metals site

. Broadleaf Lupine (Lupinus latifolius ssp. leucanthus): USFS sensitive – could potentially occur at the Money Metals site

. Pale Townsend’s Big Eared Bat (Corynorhinus townsendii pallescens): USFS sensitive – may occur in abandoned adits

A search using the AZGFD On-line Environmental Review Tool found that the study area may be part of designated critical habitat for the Mexican spotted owl (MSO) and also listed the study area as part of the Granite Mountain – Black Hills wildlife corridor. The USFS confirmed that an MSO Protected Activity Center (PAC) is located between Money Metals and Providence.

While the habitat types at Money Metals and Providence Mine differ, they should be considered sufficiently similar such that the species listed above could occur at either site. The Northern Goshawk prefers “deep, conifer dominated, mixed woodlands” and the Mexican Spotted Owl prefers “thickly wooded canyons” (National Geographic, 2002). The Money Metals site more closely fits these descriptions but the Providence Mine site is situated near this type of habitat and also has conifer trees and therefore should also be considered potential habitat for these bird species. The Eastwood Alum Root is found in ponderosa pine communities and the Broadleaf Lupine is found in oak-cottonwood, mixed shrub, ponderosa pine forest, and chaparral- ponderosa pine forest communities (AZGFD, 2009). These descriptions fit both the Money Metals and Providence Mine sites and therefore both should be considered potential habitat for these plant species.

4.3.2 Ecological Exposure Model

As is the case for human receptors, the primary sources of contamination to ecological receptors are waste rock piles, surface soils, and sediment in the drainage areas. For metals, the primary exposure route for ecological receptors for arsenic and lead is ingestion of soil. The primary exposure route for copper, cadmium, and zinc is from ingestion of plants.

An additional exposure route specific to the Providence site is direct contact and ingestion of water present in the pond.

4.3.3 Evaluation of Ecological Risk

Several criteria have been reviewed as part of the evaluation of ecological risk at Money Metals and Providence Mines. Maximum detected concentrations in sediment, soil, and waste material are compared with EPA Eco-SSLs, as available; however, EPA cautions that the Eco-SSLs should not be used as cleanup levels. Eco-SSLs are derived to be protective of the conservative

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end of the exposure and effects species distribution, and are intended to be applied at the screening stage of an ecological risk assessment to help identify COPEC. Eco-SSLs may be available for plants, soil vertebrates, avian species, and/or mammalian species. Eco-SSLs are not available for all species categories for all metals.

Following screening against the Eco-SSLs, analytical results are then compared to BLM RMC for ecological receptors, specifically the robin, the mule deer, and cattle, which represent predominant terrestrial species at the mine sites. Cattle criteria are applicable to the Providence site only as cattle-grazing does not occur at Money Metals. In selecting a criterion suitable for protecting groups of species, communities, or ecosystems, the BLM recommends using the statistical median of the RMC developed for each species (Ford, 2004). To evaluate risk, the BLM suggests interpreting exceedances of the RMC as follows:

. Less than the criteria: low risk . 1-10 times the criteria: moderate risk . 10-100 times the criteria: high risk . Greater than 100 times the criteria: extremely high risk

Site data (i.e., the maximum detected concentration of sediment, waste material, and soil) compared to the BLM RMC are evaluated based on the above recommended scale to assign a degree of risk to the representative receptors and to the published median RMC to assign an overall potential risk level to the ecological community or ecosystem.

4.3.3.1 Money Metals Mine

Previous field work at Money Metals Mine consists of sediment, soil, and waste material samples collected during the USFS 2002 sampling event and the E&E 2003 sampling event. The current sampling effort consisted of collecting sediment, soil, waste material, and surface water samples. The initial ARAR/TBC evaluation for ecological receptors is presented in Table G3 (Appendix G). The COPECs for Money Metals Mine are listed below and discussed further in the subsections that follow.

. Sediment – antimony, arsenic, cadmium, copper, lead, thallium, and zinc

. Soil –copper, lead, and zinc

. Waste material – antimony, arsenic, cadmium, copper, lead, manganese, mercury, selenium, silver, and zinc

. Surface water – cadmium, copper, zinc

4.3.3.1.1 Sediment

A total of seven sediment samples from the mine site, plus three background sediment samples, were collected as part of the 2002 USFS sampling effort, 2003 E&E PA/SI sampling effort, and the current sampling effort. Following the initial data screening and ARAR/TBC review, the

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COPEC for sediment at Money Metals Mine are antimony, arsenic, cadmium, copper, lead, thallium, and zinc. BLM RMC have not been established for antimony and thallium. These metals are compared to EPA Eco-SSLs to evaluate potential risk (Table G3, Appendix G).

Antimony was detected in one sediment sample at a concentration of 0.5 mg/kg, which slightly exceeds the sediment background mean concentration of 0.39 mg/kg and the most conservative mammalian Eco-SSL of 0.27 mg/kg. The mammalian Eco-SSL range is based on three mammalian species: a mammalian ground insectivore (vole) (0.27 mg/kg); an herbivore (vole) (10 mg/kg); and a carnivore (weasel) (4.9 mg/kg) (EPA, 2005). Because the mean antimony background concentration also exceeds the most conservative Eco-SSL the overall risk to mammalian species presented by antimony in sediment is most likely low.

The maximum detected concentration of thallium in sediment is 1.47 mg/kg compared to the mean value of 0.59 mg/kg. EPA has not developed Eco-SSLs for thallium. Additional research on the eco-toxicity of thallium indicates that there is low confidence in the current data available for mammalian species and there appear to be no useful studies of thallium on birds, reptiles or amphibians (USACHHPM, 2007). Although the maximum detected concentration of thallium exceeds the mean sediment background concentration, it does not exceed the UCL95 concentration for soil (3.06 mg/kg). It is unlikely that thallium present in the ephemeral drainage represents a significant risk to terrestrial wildlife above overall background concentrations (soil and sediment combined).

The maximum detected concentrations of the remaining COPECs for sediment are shown in Table 3 with the applicable risk-based criteria. An estimate of risk from each of the COPECs, based on the scale suggested by BLM is also presented. The mean background concentration for arsenic, cadmium, copper, lead, and zinc exceeds the BLM RMC for the robin.

Table 3 Money Metals Mine – Sediment Ecological Risk Evaluation

Concentration (mg/kg) BLM Back- BLM BLM COPEC Max. RMC Level of Level of Overall Level ground RMC RMC Conc. Mule Risk1 Risk1 of Risk1 Mean Robin Median Deer Arsenic 6.0 16 200 Low 4 Moderate 275 Low Cadmium 1.19 2.84 3 Low 0.3 High 3 Low Copper 20 106 102 Low 7 High 136 Low Lead 47.77 220 106 Moderate 6 High 125 Moderate Zinc 96.77 441 222 Moderate 43 Moderate 307 Low 1 Level of risk based on comparison of the maximum detected concentration in sediment at Money Metals Mine to the BLM RMC. NE – None established NA – Not applicable

4.3.3.1.2 Soil

Three soil samples, not including background samples, were collected during the current investigation. Each of the previously collected soil samples are representative of background locations. Following the initial data screening and ARAR/TBC review, the COPEC for soil at

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Money Metals Mine are copper, lead, and zinc. Table 4 presents the maximum detected concentrations for each of the COPECs compared to background and the BLM RMC. Background concentrations for each of the COPECs exceed the BLM RMC for the robin. The maximum detected concentrations of copper, lead, and zinc are less than the BLM RMC for the mule deer and the median wildlife BLM RMC, which represents a low overall risk to the ecosystem.

Table 4 Money Metals Mine – Soil Ecological Risk Evaluation

Concentration (mg/kg) BLM BLM BLM Overall COPEC Background Max. Level of Level of RMC RMC RMC Level of UCL Conc. Risk1 Risk1 95 Mule Deer Robin Median Risk1 Copper 20 36 102 Low 7 Moderate 136 Low Lead 43 71 106 Low 6 Moderate 125 Low Zinc 64.4 110 222 Low 43 Moderate 307 Low 1 Level of risk based on comparison of the maximum detected concentration in soil at Money Metals Mine to the BLM RMC.

4.3.3.1.3 Waste Material

Nine waste source samples were collected from Money Metals. Following the initial data screening and ARAR/TBC review the COPEC for waste material are antimony, arsenic, cadmium, copper, lead, manganese, mercury, selenium, silver, and zinc. BLM RMC have not been established for antimony, manganese, selenium, or silver. These metals are compared to EPA Eco-SSLs to evaluate potential risk (Table G3, Appendix G).

The maximum detected concentration of antimony in waste rock is 3.21 mg/kg compared to a background UCL95 of 1.32 mg/kg and to the most conservative EPA Eco-SSL of 0.27 mg/kg. As discussed previously for sediment, mammalian Eco-SSLs are based on three mammalian species: a mammalian ground insectivore (vole) (0.27 mg/kg); an herbivore (vole) (10 mg/kg); and a carnivore (weasel) (4.9 mg/kg) (EPA, 2005). Because the background UCL95 concentration also exceeds the most conservative Eco-SSL but not the SSLs derived for the other two mammalian species, the overall risk presented by antimony in waste rock is most likely low.

Manganese is an essential nutrient to both plants and animals but can be toxic at high concentrations. The maximum detected concentration of manganese is 1,740 mg/kg compared to the background UCL95 of 536 mg/kg. The maximum detected concentration and the background UCL95 concentration exceed the EPA Eco-SSL for plants (200 mg/kg) and for soil invertebrates (450 mg/kg) but does not exceed the Eco-SSL for avian (4,300 to 6,500 mg/kg) or mammalian species (4,000 to 6,200 mg/kg) (EPA, 2007). Concentrations of manganese in waste rock at the Money Metals mine site may represent a moderate risk to plants and soil invertebrates and a low risk to avian and mammalian species.

Selenium was detected in one waste rock sample at a concentration of 900 mg/kg. This concentration likely represents an anomalous value as the maximum detected concentration in eight other waste rock samples is 1.37 mg/kg. It is unlikely that selenium is present in concentrations that represent a risk to ecological receptors.

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The maximum detected concentration of silver is 148 mg/kg, which exceeds EPA Eco-SSLs for insectivorous avian and mammalian species (4.2 mg/kg and 14 mg/kg, respectively), and herbivorous avian species (69 mg/kg); the background UCL95 is 0.61. The Eco SSLs for herbivorous mammalian and carnivorous avian and mammalian species are not exceeded. Based on these comparisons, silver likely presents a low to moderate risk to ecological receptors.

The remaining COPEC and their estimated risk to ecological receptors are presented in Table 5. For each of the remaining COPEC, except mercury, the background UCL95 exceeds the most conservative BLM RMC (robin). The maximum concentrations of arsenic, copper, and lead are detected in the same sample as the anomalous selenium result. It is possible that the concentrations of arsenic, copper, and lead in this sample are also anomalously high. Considering all waste rock sample results, the potential risk to ecological receptors from arsenic is low to moderate; from copper it is high; and from lead is extremely high. Although mercury is detected at concentrations exceeding background, detected concentrations represent a low risk to ecological receptors.

Table 5 Money Metals Mine – Waste Material Ecological Risk Evaluation

Concentration (mg/kg) BLM BLM BLM Overall COPEC Background Max. RMC Level of Level of RMC RMC Level of UCL Conc. Mule Risk1 Risk1 95 Robin Median Risk1 Deer 500 Extremely Low to Arsenic 9.6 200 Moderate 4 275 (190) High Moderate Cadmium 0.54 20 3 Moderate 0.3 High 3 Moderate 2,280 Extremely Copper 20 102 High 7 136 High (1,560) High 39,800 Extremely Extremely Extremely Lead 43 106 6 125 (30,000) High High High Mercury 0.032 1.03 9 Low 1 Low 8 Low Zinc 64.4 2,320 222 High 43 High 307 Moderate 1 Level of risk based on comparison of the maximum detected concentration in waste material at Money Metals Mine to the BLM RMC. 2 Values in parentheses indicate the second highest detected concentration.

4.3.3.1.4 Surface Water

Concentrations of dissolved cadmium, copper, and zinc were detected in MM-SW-2 (adjacent to the waste rock pile) that exceed Arizona A&We surface water quality standards. Only copper continues to exceed the standard in the downstream sample (MM-SW-3). Impacts of dissolved cadmium and zinc in surface water appear to be confined to the immediate mine area, and do not appear to be impacting Big Bug Creek. Based on the limited available data, risk to aquatic and wildlife receptors from surface water is likely to be low for cadmium and zinc and potentially moderate for copper.

4.3.3.1.5 Money Metals Ecological Risk Conclusions

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The future envisioned use of Money Metals Mine is a return to the natural environment. No other designated uses, such as cattle grazing, are foreseen. Based on comparison of site data to available ecological risk criteria, including EPA Eco-SSLs and BLM RMC, the estimated risks to ecological receptors from COPEC at Money Metals Mine are summarized below.

. Sediment – Maximum detected concentrations of COPECs in sediment indicate the potential risk to the overall ecosystem is low for arsenic, cadmium, copper, and zinc. Comparison of the maximum detected concentration to applicable ecological risk criteria suggests potential risk from lead in sediment is moderate; however, concentrations of lead detected in surface water indicate that lead present in sediment may not be mobile.

. Soil – Potential risk to the ecosystem from exposure of copper, lead, and zinc in soil is low.

. Waste Rock – The potential risk to the ecosystem from mercury in the waste rock material is low. Site data suggests that the maximum detected concentration of arsenic is anomalously high and that the overall risk to the ecosystem from arsenic is likely low. Cadmium and zinc may represent a moderate risk; copper may represent a moderate to high risk, and lead may represent a high to an extremely high risk. Although concentrations of lead in the waste rock material are elevated, lead does not appear to be mobile based on the low concentrations detected in a surface water sample collected adjacent to the waste rock pile.

. Surface Water – Potential risks from cadmium, copper, and zinc to aquatic and wildlife receptors in the unnamed ephemeral drainage are moderate. Potential risks to Big Bug Creek from cadmium and zinc are low. Copper may potentially represent a moderate risk to Big Bug Creek. This evaluation is based on limited available data. Additional surface water data would help refine the evaluation of potential risk.

4.3.3.2 Providence Mine

Previous field work at Providence Mine consists of collection of sediment, soil, and waste material, and surface water samples during the USFS 2002 sampling event and the E&E 2003 sampling event. Current sampling efforts at the mine consisted of collecting sediment, soil, waste material, surface water, and groundwater samples. The initial ARAR/TBC evaluation for ecological receptors is presented in Table G6 (Appendix G). The COPECs for Providence Mine are as follows:

. Sediment – arsenic, cadmium, copper, lead, and zinc

. Soil – lead

. Waste material – arsenic, cadmium, chromium, copper, lead, nickel, selenium, silver, and zinc

. Surface water – selenium

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. Groundwater – none

4.3.3.2.1 Sediment

A total of 17 sediment samples, plus two field duplicates, and six background sediment samples were collected from Providence Mine as part of the 2002 USFS sampling effort, the 2003 E&E sampling effort, and the current sampling effort. Sediment was collected from the on-site pond, Eugene Gulch and the two unnamed ephemeral washes that flow through the site. Previous pond sediment samples were collected near the shore. The pond sediment sample collected as part of the current investigation was collected from the center of the pond. Following the initial data screening and ARAR/TBC review, the COPEC for sediment at Providence Mine are aluminum, arsenic, cadmium, copper, lead, and zinc.

There are no BLM RMC or Eco-SSLs developed for aluminum. Aluminum was detected in one sediment sample (20,300 mg/kg) out of six collected samples at a concentration greater than the UCL95. Aluminum is the most commonly occurring metallic element in the earth’s crust with naturally occurring concentrations variable over several orders of magnitude. Typical natural concentrations can range from 10,000 to 300,000 mg/kg. Chemical and toxicological information suggests that aluminum must be in a soluble form in order to be toxic to biota. It is, however, difficult to measure accurately or with precision the concentration of soluble aluminum in pore water or in soil extracts (EPA, 2003). Forms of soluble aluminum may be toxic to plants and invertebrates but its toxicity is not well understood. Aluminum was detected in only one sediment sample at a concentration greater than site-specific background; however, the detected concentration is well within the naturally occurring range of aluminum and therefore unlikely to present a risk to ecological receptors.

Table 6 presents the maximum detected concentration of arsenic, cadmium, copper, lead, and zinc in sediment samples, the background UCL95, and applicable risk-based criteria comparison.

Table 6 Providence Mine – Sediment Ecological Risk Evaluation

Concentration (mg/kg) Back- Mule Overall COPEC Max. Level of Cattle Level of Robin Level of Median ground Deer 1 1 1 Level of Conc. Risk RMC Risk RMC Risk RMC 1 UCL95 RMC Risk Arsenic 8.5 14 200 Low 419 Low 4 Moderate 275 Low Cadmium 0.5 0.7 3 Low 15 Low 0.3 Moderate 3 Low Copper 266 360 102 Moderate 413 Low 7 High 136 Moderate Lead 14 41 106 Low 244 Low 6 Moderate 125 Low Zinc 42 79 222 Low 1,082 Low 43 Moderate 307 Low 1 Level of risk based on comparison of the maximum detected concentration in sediment at Providence Mine to the BLM RMC.

The background UCL95 for each of these metals exceeds the BLM RMC for the robin. Based on the maximum detected concentration of each COPEC, the potential risk to ecological receptors posed is low for arsenic, cadmium, lead, and zinc. Copper presents a low risk to cattle and a moderate risk to the overall ecosystem.

4.3.3.2.2 Soil

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After initial data review, the COPECs for soil are lead and total chromium. The soil background UCL95 for lead (17.4 mg/kg) exceeds the BLM RMC for the robin. Lead was detected in one sample at a concentration that significantly exceeds the UCL95. The concentration of lead in SO/B/1, collected during the PA/SI, was 582 mg/kg. This result is an order of magnitude greater than all other soil, sediment, or waste rock/tailings samples collected at Providence indicating the sample result may be anomalous or representative of a small area of impact. Although comparison of this result to the BLM RMC indicates a moderate risk to ecological receptors, including cattle, this estimate is likely overly conservative. Due to the overall low lead concentrations throughout the site, it is unlikely that lead presents a significant risk to ecological receptors or the ecosystem.

Table 7 Providence Mine – Soil Ecological Risk Evaluation

Concentration (mg/kg) Back- Mule Overall COPEC Max. Level of Cattle Level of Robin Level of Median ground Deer 1 1 1 Level of Conc. Risk RMC Risk RMC Risk RMC 1 UCL95 RMC Risk 582 Low to Low to Low to Lead 17.3 106 244 6 High 125 (63) Moderate Moderate Moderate 1 Level of risk based on comparison of the maximum detected concentration in soil samples at Providence Mine to the BLM RMC. 2 Value in parentheses indicate the second highest detected concentration.

4.3.3.2.3 Waste Material

A total of 20 waste rock/tailings samples, including one field duplicate, were collected from Providence Mine. Following the initial data screening and ARAR/TBC review the COPEC for waste material at Providence Mine are aluminum, arsenic, cadmium, chromium, copper, lead, nickel, selenium, silver and zinc.

Of the COPEC in waste source material at Providence, BLM RMC have been established for arsenic, cadmium, copper, lead, and zinc. Table 8 provides background UCL95, maximum detected concentration, and comparison to the BLM RMC for those metals. As shown in the table, background concentrations for each of these metals exceed the BLM RMC for the robin. The maximum detected concentration of arsenic, cadmium, and zinc indicate these metals present an overall low risk to the ecosystem. The maximum detected concentration of lead was 247 mg/kg; however, this concentration was detected in only one out of 19 samples. The next highest detected concentration was 66 mg/kg. The distribution of lead across the site indicates that the risk to ecological receptors, including cattle is low.

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Table 8 Providence Mine – Waste Material Ecological Risk Evaluation

Concentration (mg/kg) Back- Mule Overall COPEC Max. Level of Cattle Level of Robin Level of Median ground Deer 1 1 1 Level of Conc. Risk RMC Risk RMC Risk RMC 1 UCL95 RMC Risk Arsenic 13.6 25 200 Low 419 Low 4 Moderate 275 Low Cadmium 0.5 1.2 3 Low 15 Low 0.3 Moderate 3 Low Extremely Copper 382 1,000 102 Moderate 413 Moderate 7 136 Moderate High 247 Low to Low to Low to Lead 17.3 106 244 6 High 125 (66) Moderate Moderate Moderate Zinc 47.6 54 222 Low 1,082 Low 43 Moderate 307 Low 1 Level of risk based on comparison of the maximum detected concentration in waste material at Providence Mine to the BLM RMC.

Copper presents a potentially moderate risk to grazing cattle. Copper is considered an essential nutrient for cattle and is sometimes given to cattle as a dietary supplement. Ingestion of excess copper relative to other minerals can result in toxicity as more copper is absorbed rather than being excreted by the animal. It is unknown whether cattle currently grazing on the site are given copper supplements. Once copper is ingested, it is absorbed through the intestines and travels in the blood to the liver. Copper bioavailability for cattle is inhibited by excess molybdenum, iron, and/or sulfate.

The remaining COPEC (i.e., aluminum, chromium, nickel, selenium, and silver) are compared to EPA Eco-SSLs as shown in Table G6 (Appendix G). As discussed in Section 4.3.3.2.1, there is not a developed Eco-SSL for aluminum. Aluminum was detected in only one waste rock sample (25,900 mg/kg) at a concentration exceeding the soil UCL95 (22,510 mg/kg). The maximum detected aluminum concentration in waste rock is within typical naturally occurring concentrations and therefore does not present a risk to ecological receptors.

Total chromium concentrations were compared to the Eco-SSLs for trivalent chromium because site data indicates that the majority of total chromium in samples collected from the site is in the form of trivalent chromium. The maximum detected concentration of total chromium in waste source samples is 441 mg/kg, which exceeds the Eco-SSLs for insectivorous and herbivorous avian species as well as all three mammalian species types. The majority of chromium results, however, are less than all but the SSL for insectivorous avian species. The overall potential risk from chromium to the ecosystem is likely to be low due to general distribution of chromium in waste source samples. Likewise, the distribution of nickel, selenium, and silver indicate that these metals are unlikely to present a significant risk to ecological receptors.

4.3.3.2.4 Surface Water

A total of four surface water samples, including two field duplicates, were collected from the pond at Providence Mine during the 2003 E&E PA/SI sampling effort and the current sampling effort. No background surface water data is available for Providence Mine; analytical data was compared to the applicable ARARs and TBCs only. None of the analytical results of collected pond samples exceed surface water criteria for livestock watering.

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The total selenium concentration detected in the pond sample collected during the PA/SI (0.0172 mg/L) exceeds the A&Ww chronic standard of 0.002 mg/L, which indicates a potential risk to aquatic life and wildlife. The laboratory reporting limit (0.025 mg/L) was greater than the A&Ww standard during the current investigation. The detected concentration of selenium from the pond is less than the Arizona AgL (0.05 mg/L) indicating the pond does not pose a risk if used for livestock watering purposes.

Waterborne selenium is not particularly toxic to fish and wildlife when water is the only exposure route. Toxic thresholds for selenium are generally greater than 1 mg/L for adult fish (USDOI, 1989). But, uptake of selenium by biota can occur from water or diet. Uptake of water- soluble selenium by fish and wildlife can be either by gills, epidermis or gut; however, dietary exposure of animals to selenium is usually the dominant pathway of uptake due to selenium’s propensity to bioaccumulate and because animals are typically at higher trophic levels in the aquatic and terrestrial food chain (Hamilton, 2004).

The speciation of waterborne selenium can substantially affect the potential for bioaccumulation in fish and wildlife tissues, particularly at higher concentrations (USDOI, 1989). Waterborne selenite (typically found in coal fly-ash effluent and oil refinery wastewater) is more readily bioaccumulated than waterborne selenate (typically found in irrigation wastewater). Toxic effects have been observed in the 0.001 to 0.003 mg/L range for both selenate- and selenite- dominated waters. Possibly, at these lower concentrations, selenate is reduced to the more rapidly metabolized selenite, but higher concentrations of selenate may overwhelm the reduction pathways (USDOI, 1989). In lentic environments (i.e., standing water), selenate is less prevalent, selenite is more common, and both forms are biologically and chemically reduced to elemental and organo-selenium forms. These reduced forms are prevalent in lentic sediments and form the basis for uptake by benthic invertebrates and subsequent food chain bioaccumulation.

Studies suggest that some fish and avian species may be more susceptible to selenium toxicity than other species (Hamilton, 2004). For example, in avian species, studies have shown that black-necked stilt embryos seem to be more sensitive than the American avocet embryos and killdeer embryos are more sensitive than snowy plover. Freshwater ducks appear to be among the most sensitive bird species to selenium (Hamilton, 2004).

In the absence of site-specific data but based on available reported research data, it is likely that selenium in the pond presents a risk to ecological receptors. Additional site-specific data would be needed to provide a clearer estimation of risk to ecological receptors including migratory bird populations. These additional data needs could include, but not be limited to: 1) identification of predominant avian, fish, and amphibian species that may be exposed to pond surface water; 2) estimation of frequency of pond use by migratory populations (i.e., bird counts); 3) additional surface water samples collected at different times of the year to test for temporal changes; 4) identification of the predominant chemical species of selenium present in the pond.

4.3.3.2.5 Groundwater

Two groundwater samples, including one field duplicate, were collected during the current sampling efforts from ADWR number 55-511407, the southern-most well onsite. There are no

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ARARs for ecological receptors; however, the Arizona AgL can be used as a TBC to estimate potential risk if groundwater were to be used for livestock watering. None of the analyzed metals exceed the AgL.

4.3.3.2.6 Summary of Ecological Risk: Providence Mine

The future envisioned use of the Site is a return to the natural environment with a likely continuation of the use of a grazing allotment already established at the site. Based on comparison of site data to available ecological risk criteria, including EPA Eco-SSLs and BLM RMC, the estimated risks to ecological receptors from COPEC at Providence Mine are summarized below.

. Sediment – Arsenic, cadmium, lead, and zinc in sediment present a low risk to the overall ecosystem. Copper in sediment potentially poses a moderate risk to the ecosystem as a whole and a low risk to cattle.

. Soil – Lead in soil likely presents a low overall risk to cattle and the ecosystem in general.

. Waste rock/tailings – Arsenic, cadmium, chromium, lead, nickel, selenium, silver and zinc in waste source samples present a low risk to the ecosystem including grazing cattle. Copper presents a moderate risk.

. Surface Water – Detected concentrations of metals in pond samples do not indicate a potential risk for livestock watering uses. A moderate risk may be present to aquatic life and migratory birds from total selenium based on analytical results of one sample.

. Groundwater – Detected concentrations of metals in groundwater do not indicate a potential risk if groundwater is used for livestock watering.

4.4 UNCERTAINTY EVALUATION

This evaluation of human-health and ecological risk is subject to a certain degree of uncertainty from a variety of sources, including site data, exposure assessment, and risk characterization. The size of the data set, sample locations, and sample analyses can all contribute uncertainty to the risk assessment. In general, smaller data sets lend more statistical variability to estimates of contaminant concentrations and may over or under estimate the true mean or maximum concentration. Additional sources of uncertainty include:

. Use of maximum detected concentrations as opposed to mean values for risk evaluation is likely to result in an over-estimation of human health and ecological risk.

. The degree of uncertainty is related to the size of the data set from which conclusions are being drawn. The available data set for both Money Metals and Providence is relatively small, adding to the level of uncertainty.

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. A common uncertainty at abandoned hard rock mining sites stems from the variation of concentrations of metals throughout the mining site, specifically in waste rock and tailings samples. There are often localized areas of naturally occurring high mineral deposits, and it is possible that the chosen background locations either missed or over represented these areas. This could result in screening out potential contaminants that should be included and/or retaining contaminants that should be eliminated due to natural background conditions.

. Background concentrations and associated UCL95 calculations were based partly on previous investigations performed by others. For the purposes of this evaluation, it is assumed that sample locations identified as background at the time of collection are representative of appropriate background areas unless described otherwise. The background mean was calculated for each environmental media using available data from other mine sites in the mining district that had similar geology. The calculated mean may over or under estimate the true background concentrations for any given mine site area. Use of the background concentrations to screen out COPC and COPEC may result in screening out potential contaminants that could be above true background levels or retaining COPC and COPEC that are below true background levels.

. The human exposure assessment was based on limited recreational use of the mine sites and with a future envisioned return of the site to the natural environment and minimal human visitation. If future land uses changes, the exposure assessment for human receptors may not be adequately protective.

. Ecological receptor criteria were based on the scientific literature often developed for different species, the same species from a different region, or under conditions that differ from site conditions, which could over-estimate or under-estimate risk. The BLM ecological RMC were selected from available criteria developed for test species that were phylogenetically similar to likely receptors (Ford, 2004). The highest potential for uncertainty in the wildlife calculations is associated with the protection against a greater toxic response to any metal by wildlife, as compared to the toxic response to the same metal by laboratory animals.

. Individual ecological receptors are not likely to spend all of their time in one single area and would most likely roam through the entire watershed, or possibly, locations outside of the boundaries for either of the mine sites investigated. For this ecological risk evaluation, evaluating each mine separately and using comparisons to the maximum detected concentration from waste rock/tailings, soil, or sediment at each mine is likely to over-estimate actual ecological risk.

. Evaluation of risk assumes that 100% of the detected concentrations of the COPECs are bioavailable, which is likely to over-estimate potential risk. . Background data for surface water and groundwater is unavailable for Providence Mine preventing a comparison to natural background conditions. Conclusions regarding the impact of historical mining activities on surface water and groundwater at the site cannot be made.

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5.0 IDENTIFICATION OF REMOVAL ACTION OBJECTIVES

5.1 DETERMINATION OF REMOVAL ACTION SCOPE

The overall goal of potential removal actions at the Money Metals and Providence Mines is to minimize the risk that COPCs and COPECs pose to human health and/or the environment. The removal action scope in this EE/CA considers a cleanup, and/or containment level protective of human health and the environment based on each site’s current and anticipated future land use.

Both sites currently experience low visitation; however, evidence of an increase in visitation has been observed recently (USFS, 2010a). The Money Metals site is potentially eligible for listing on the National Historic Register. Evaluation of potential removal actions and development of their conceptual design must consider preservation of historic site features (i.e., the hoist and structure remnants). Currently, the Providence site is approved for cattle-grazing as part of the Big Bug Allotment. That use is expected to continue. Future development of either site is not planned or anticipated.

5.2 REMOVAL ACTION OBJECTIVES

EPA guidance (Guidance on Conducting Non-Time-Critical Removal Actions under CERCLA) provides for the development of removal action objectives to form the basis for evaluating alternatives. According to the guidance, “removal action objectives generally consist of medium- specific goals for protecting human health and the environment. The objectives should be as specific as possible but not so specific that the range of alternatives that can be developed is unduly limited. Removal action objectives should identify, for example, the contaminants of concern and exposure route(s) and receptor(s).”

Data collected during previous investigations and during the current investigation were evaluated in the Streamlined RA by comparing detected concentrations of the COPCs with chemical- specific ARARs and TBCs. Results of the Streamlined RA concluded the primary human exposure risk to contaminants at the Money Metals site is from arsenic and lead; the primary potential ecological exposure risk is from copper and lead. For Providence, the primary ecological exposure risk (to cattle) is from copper; none of the COPCs were considered to present a risk to human receptors based on anticipated future site uses. Removal action objectives (RAOs) for each site are listed below.

. Reduce exposure of humans and ecological receptors to COPCs and COPECs waste rock/tailings areas to levels that do not result in unacceptable site-related risks.

5.3 IDENTIFICATION OF CLEAN UP ACTION LEVELS

Cleanup action levels have been developed for the Site based on ARARs and TBCs for Site exposures in consideration of current and anticipated future site uses. At Money Metals, current

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site use is infrequent recreational visitation, which also constitutes anticipated future use. At Providence, the current site uses are infrequent recreational use and livestock grazing. These uses are expected to continue in the foreseeable future.

While regulatory standards and risk-based concentrations must be considered in the development of cleanup levels, EPA guidance and policy do not recommend that cleanup levels be established at levels below background, even if the background level exceeds an ARAR or risk-based concentration. Where a regulatory standard or risk-based concentration is greater than the background level, the standard or risk-based concentration is used as the cleanup level. Identified clean-up action levels for the site are listed in Table 9.

Table 9 Cleanup Action Levels

Site COPC/COPEC Cleanup Level Driver of Risk Basis of Cleanup Level Money Arsenic 20 mg/kg Human health BLM RMC – camper Metals Lead 1,000 mg/kg Human health BLM RMC – camper Providence Copper 413 mg/kg Ecological (cattle) BLM RMC – cattle (Providence only)

5.4 ESTIMATE OF VOLUME OF CONTAMINATED MATERIAL

Based on field measurements of waste rock and tailings piles, the estimated volume of waste material at Money Metals Mine and Providence Mine was calculated for each of the piles present at both sites. Volume calculations were made for each pile regardless of whether analytical results and the subsequent risk assessment indicated a need for corrective action. Appendix I presents volume calculations for each pile at both sites. The following subsections identify the specific piles considered for corrective action based on the risk assessment and RAOs.

5.4.1 Money Metals Mine

One contiguous waste rock pile is present at Money Metals Mine. Based on the dimensions of the surface and on approximate depth measurements, the volume of waste rock material at Money Metals is 5,400 cubic yards (cy).

5.4.2 Providence Mine

Waste source material at the Providence Mine site consists of multiple waste piles scattered throughout the site as opposed to one contiguous pile. Each waste pile was evaluated and is identified by its sample identification used for laboratory analysis. For example, the waste source sample PM-WS-4, was evaluated as one waste pile named PM-WS-4. Where multiple samples were taken from a single waste pile, that pile is named using both sample identifications (e.g., waste source samples PM-WS-8 and PM-WS-9 are from the same contiguous pile; volume was evaluated as one waste pile named PM-WS-8/9. Calculated volume estimates for each waste

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source pile at Providence are presented in Appendix I. Based on results of the risk assessment, concentrations of COPECs (copper) in five of the Providence waste rock piles exceed the ecological (cattle) risk-based criterion. Those five piles and their corresponding volume are listed below.

. PM-WS-2/3: 600 cy . PM-WS-4: 500 cy . PM-WS-6: 850 cy . PM-WS-8/9: 600 cy . PM-WS-10: 40 cy

As discussed in Section 4.2.2.2, one waste pile (PM-WS-1) exhibited an arsenic concentration greater than the camper BLM RMC. Based on the low frequency of exceedances, the low frequency of camper visitation, and the improbability that a camper would select the waste pile for a campsite based on its location in the center of Eugene Gulch, PM-WS-1 was determined to present a low risk to human health and therefore is not included in the above list of waste piles requiring corrective action. PM-WS-1 is partially on private land and partially on USFS- administered land. If future activities require this pile to be moved for whatever reason, legal matters related to the dual land ownership would need to be addressed before any work could proceed on the shared waste pile.

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6.0 IDENTIFICATION AND ANALYSIS OF REMOVAL ACTION ALTERNATIVES

Removal action alternatives can generally be grouped into the following categories: no action, institutional controls, treatment technologies, containment technologies, and removal technologies. Different sets of removal action alternatives have been developed for Money Metals Mine and the Providence Site. The following list presents the alternatives being considered to meet the site removal action objectives for each mine site. Excavation and off-site disposal is considered a removal technology, while on-site consolidation and capping is considered a containment technology.

Money Metals Mine . Alternative 1: No Action . Alternative 2: Institutional Controls (with Surface Water Monitoring) . Alternative 3: On-Site Consolidation

Providence Mine . Alternative 1: No Action . Alternative 2: Institutional Controls . Alternative 3: On-Site Consolidation . Alternative 4: Excavation and Off-Site Disposal

6.1 ALTERNATIVES CONSIDERED BUT NOT EVALUATED

Excavation and Off-Site Disposal was considered for Money Metals Mine but was not further evaluated for the following reasons

. TCLP analytical results (9.4 and 35 mg/L) of the Money Metals Mine waste rock exceeded the RCRA TCLP limit for lead of 5 mg/L, indicating that lead may leach out of the waste rock.

. The Bevill Exemption to RCRA for mining and mineral processing wastes allows mine waste to be disposed of in a non-hazardous landfill; however, preliminary conversations with operators of Subtitle D non-hazardous waste landfills suggest that the TCLP lead results are of concern and may affect the landfill’s acceptance of the Money Metals waste rock.

. Off-site disposal would require approximately 5,400 cy of waste rock to be excavated and disposed of. Disposal fees alone for this volume of material would range from $525,000 to $910,000 depending on whether the material can be disposed of in a RCRA Subtitle D non-hazardous landfill or in a hazardous waste RCRA Subtitle C landfill. With excavation, hauling, engineering, and construction management costs added to the disposal fee cost, the off-site disposal alternative would cost far more than an on-site alternative and thus be cost prohibitive.

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6.2 EVALUATION CRITERIA

Each of the potential removal action alternatives is evaluated against a prescribed set of criteria based on EPA guidance. The potential removal action alternatives will be evaluated based on:

. Effectiveness - Protectiveness of human health and the environment, including workers during implementation, and the compliance with ARARs - Short and long-term effectiveness - Reduction of toxicity, mobility, or volume (through treatment) of contaminants - Ability to achieve the removal objectives

. Implementability - Technical feasibility - Availability of required services, materials, and equipment - Administrative feasibility - Maintenance and monitoring requirements - Construction feasibility

. Cost (budget costs for comparative analysis) - Capital cost (direct and indirect capital costs) - Post-removal site control or operation costs - Present value cost, if needed

6.2.1 Effectiveness

This criterion addresses the ability of an alternative to maintain protection of human health and the environment and the magnitude of residual risk remaining at the site after the removal objectives have been met (long-term effectiveness). The criterion addresses the EPA preference for selection of remedies that permanently and significantly reduce the toxicity, mobility, and/or volume of impacted materials through treatment.

The criterion also addresses the ability of an alternative to comply with all ARARs and its short- term effectiveness. The short-term effectiveness criterion addresses the effects of the alternative during implementation before removal objectives have been met. Alternatives should also be evaluated with respect to their effects on human health and the environment following implementation. The following factors will be addressed as appropriate for each alternative:

. Protection of the Community – addresses any risk to the affected community that results from implementation of the proposed action, whether from air quality impacts, fugitive dusts, transportation of hazardous materials, or other sources. . Protection of Workers – assesses any threats to site workers and the effectiveness and reliability of protective measures that would be taken.

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. Environmental Impacts – evaluates the potential adverse environmental impacts from the implementation of each alternative. The factor also assesses the reliability of mitigation measures in preventing or reducing the potential impacts.

6.2.2 Implementability

This criterion evaluates the technical and administrative feasibility (i.e., the ease or difficulty) of implementation of each alternative. It also considers the availability of services and materials required for implementation and State and community acceptance of the alternative. The following factors will be addressed when evaluating the ability of alternatives to satisfy this criterion:

. Technical difficulties, site constraints, and any uncertainties associated with the implementation of an alternative. . The reliability of each alternative and the likelihood that technical problems associated with implementation of the alternative would lead to schedule delays. . The ease of undertaking additional actions to replace or augment the original alternative and the ability to monitor the effectiveness of the remedy. . Activities needed to coordinate with regulatory agencies to implement an alternative. The ability and time required to obtain necessary approvals and permits from other agencies for any off-site actions, as required. . Availability of services and materials, necessary equipment, and qualified professionals.

6.2.3 Cost

This criterion evaluates the estimated cost of each alternative. These costs include direct capital costs (i.e., costs to perform the alternative), indirect capital costs such as design expenses, permit fees (if appropriate), and annual post removal site control (PRSC) costs including monitoring and operation and maintenance (O&M) costs. The long term monitoring and operating costs include 30-year present value costs (i.e., the dollar amount needed to be set aside at the initial point in time [base year] to assure that funds will be available in the future to pay for PRSC and O&M costs).

The costs presented are based on certain assumptions applicable to each removal action alternative and are only for comparative analysis so if all things are equal, a decision can be based on the cost factor alone. The removal action alternatives presented in the EE/CA are at a conceptual design stage only and do not provide specific design details to allow development of a “true” cost estimate. The costs presented here are budget costs (consisting of labor and materials) and may be somewhat higher or lower than actual costs to account for some uncertainties such as future cost fluctuations and final design details.

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6.3 COMMON ACTIVITIES

Some degree of engineering design will be required for all options in order to prepare documents suitable for bidding purposes that will define the scope of work for prospective bidders. Development of a Site-specific Health and Safety Plan (HASP), Quality Assurance Plan (QAP), and Stormwater Pollution and Prevention Plan (SWPPP) will also be required for all options as will mobilization and demobilization of equipment. If Site work is completed in stages, additional mobilization/demobilization costs would need to be added to the affected phases of work.

Costs for common activities have been calculated separately for each alternative. The costs of common activities for each alternative vary due to the size and complexity of the Site. Appendix J contains costing tables with their respective costs for common activities.

6.4 EVALUATION OF REMOVAL ALTERNATIVES

The potential removal action alternatives for the Money Metals and Providence mines were evaluated using all three of the evaluation criteria described in Section 6.2. A general description of each alternative and discussion of the pros and cons are presented in the following subsections.

6.4.1 Alternative 1: No Action

The No Action alternative would involve leaving the mine sites at their current state. There would be no removal, containment, or institutional control actions implemented at any of the mine sites. The No Action alternative provides a baseline against which other alternatives can be compared. A consideration of risk is taken into account if no action is taken as opposed to implementing a removal action.

There are no action-specific ARARs associated with this alternative.

6.4.1.1 Effectiveness

The No Action alternative would not reduce human exposure to COPCs (arsenic and lead) or at Providence, the risk to grazing livestock. No Action does not reduce the toxicity, mobility, or volume of COPCs at the mine sites and therefore would not be considered to guarantee the desired protectiveness of human health and the environment. The No Action alternative would not achieve the removal objectives set for the mine areas in the short- or long-term.

6.4.1.2 Implementability

Although implementation is possible, the No Action alternative would be technically ineffective.

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6.4.1.3 Cost

There are no direct costs associated with the No Action alternative.

6.4.2 Alternative 2: Institutional Controls

Money Metals Mine

Alternative 2 will combine the implementation of institutional controls to prevent human access to the site as well as periodic surface water monitoring at locations shown on Figure 7. Collected samples will be used to confirm whether or not the Money Metals waste rock is impacting downstream water quality. Six samples plus one field duplicate will be collected during each bi- annual sampling event over a 2-year period. The bi-annual sampling will occur during the winter and summer monsoon seasons. Sampling will include analysis of total and dissolved arsenic, copper, lead, and zinc; hardness; alkalinity; and total suspended solids.

An existing shaft that was previously closed by the USFS with a polyurethane foam plug (PUF) plug and soil backfill has settled leaving a depression that is approximately 6 feet deep and 10 feet in diameter. Information received from the USFS suggests that the PUF plug may be close to 20 feet deep. The USFS believes that the unconsolidated backfill that was placed over the PUF plug has settled and that the PUF plug has not failed. Further investigation should be conducted to confirm and verify the details of the actual shaft closure; however, for purposes of this EE/CA, it will be assumed that an additional 3-foot thick PUF plug will be installed and then backfilled with clean native material to an approximate 90% maximum dry density.

A locked gate will be installed at the access road entrance as an institutional control. At the end of the sampling period, sampling results will be evaluated and a decision will be made as to whether or not additional actions will be taken. If no further actions are required, the access road will be ripped, pocked with 18-inch deep pocks, and seeded with a native seed mix for a distance of 150 feet from the intersection with Big Bug Mesa Road to discourage pedestrian traffic and ATV or other vehicle traffic.

Providence Mine

Institutional controls at the Providence site include enclosing (i.e., fencing) the waste rock piles with concentrations of copper exceeding the BLM RMC cattle criterion. Fencing would consist of 4-strand barbed wire (approximately 2,000 linear feet) as shown in Figure 9. Additional site work included in this alternative includes:

. Abandoning two existing groundwater wells per ADWR requirements.

. Performing a biological bat study and subsequent closure of the adit located near the eastern drainage. Depending on the results of the bat study, the adit will be closed with either a bat gate or PUF plug.

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Action Specific ARARs

The following action-specific ARARs would be applicable to this alternative for both mine sites:

. Arizona Pollutant Discharge Elimination System (AZPDES) (18 A.A.C., Chapter 9, Articles 9 and 10; Arizona Revised Statutes [A.R.S.] Title 49, Chapter 2, Article 3.1; and the Clean Water Act as amended) – would need to meet the substantive requirements regarding control of pollutants, specifically erosion and sediment controls during road closure activities. . Arizona Air Pollution Control Act (18 A.A.C., Chapter 2), Non-point Source Emission Standards – dust suppression may be required to keep air-borne particulates to a minimum. . Well Construction and Licensing of Well Drillers (A.A.C. Title 12, Chapter 15, Article 8; A.R.S Title 45, Chapter 2, Article 10) – well abandonments are specifically described in A.A.C. R12-15-816. . Arizona Native Plant Regulations (3 A.A.C., Chapter 3, Article 11 and Appendix A) – would need to comply with the substantive requirements of the protection of native plants listed in Appendix A.

6.4.2.1 Effectiveness

At the Money Metals Mine, institutional controls will be effective in protecting human health because the controls will limit public access to the mine site. Additional surface water sampling will be effective in determining whether or not the watershed is being impacted downstream of the Money Metals waste rock pile. If it is determined that the water quality is impacted, effective long-term protective measures will be evaluated.

Closure of the of the mine adit at Providence will limit public access adit and therefore will be protective of human health at the Providence Mine. Barbed wire fencing surrounding waste rock piles with copper concentrations exceeding the BLM RMC for cattle will effectively limit cattle exposure to copper. Barbed wire fencing will not restrict exposure of other ecological receptors to the waste rock piles.

6.4.2.2 Implementability

The institutional controls can be easily implemented with local subcontractors. Periodic inspection and maintenance will be required to ensure that the controls remain effective over time.

At Money Metals, because the stream is ephemeral, sample collection will be dependent on when water is flowing. During the summer monsoon season when storms may be intense but of short duration, it may be difficult to time a site visit with actual water flow.

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6.4.2.3 Cost

Costs to implement Alternative 2 for each mine site area are as follows:

. Money Metals Mine – $93,851 (capital costs), $50,631 (PRSC) (Table J1, Appendix J) . Providence Mine – $36,254 (capital costs), $50,631 (PRSC) (Table J2, Appendix J)

6.4.3 Alternative 3: On-Site Consolidation and Capping

Alternative 3 includes excavating, consolidating and regrading the waste rock into a smaller footprint. A clean soil cover would be installed over the consolidated waste rock to prevent human and ecological exposures.

Money Metals Mine

The Money Metals Mine is a single waste rock pile with existing side slopes of approximately 1.5H:1V that terminate immediately adjacent to an unnamed ephemeral stream. Historical archeological features exist on the west end of the site that the USFS wishes to protect and preserve. The USFS prefers not to have any additional waste rock material added to a buffer area that is within 50 feet of the archeological features as shown on Figure 8. This buffer area eliminates the western third of the existing waste rock pile as a potential area for consolidation.

Conceptual consolidation calculations in Appendix I show that pulling the existing waste rock pile toe back away from the stream approximately 10 feet and regrading the existing slope to a more stable 2H:1V slope would generate approximately 2,855 cy of waste rock that would need to be relocated on the eastern two thirds of the existing waste rock top slope. This amount of material would raise the existing top slope elevation approximately 18 feet. The estimated available top slope width of 40 feet does not allow for this amount of material to be placed on the top slope and still maintain a 2H:1V side slope. Leaving the existing waste rock toe where it currently is and regrading the existing waste rock slope to a 2H:1V slope generates an estimated 1,110 cy of waste rock that would need to be relocated, which will raise the top slope approximately 7 feet and would allow a top slope bench approximately 13 feet wide to be maintained.

Based on the consolidation calculations, the existing waste rock side slopes would be regraded at a 2H:1V slope from the existing stream bed to the final top slope elevation. Material removed from the side slopes would be relocated to the eastern two thirds of the existing waste rock pile and placed so that a minimum 5-foot wide top slope still remains. The top slope would be graded so that run on drainage from off-site upslope areas and from the top slope will drain laterally to the east discharging at the east end of the waste rock pile. This will minimize the amount of drainage that will flow over the waste rock cover side slopes and will mitigate erosion of the side slopes. The graded, consolidated waste rock would then be capped with a 12-inch thick soil cover, a 6-inch thick topsoil cover, seeded with a native seed mix, and covered with a

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biodegradable erosion control fabric. Rip rap will be added to the drainage channel on the top slope to control erosion.

TCLP results indicate an impermeable barrier cap may be required in addition to the vegetative soil cover to prevent percolation into underlying layers and subsequent leaching into the ephemeral drainage; however, results of surface water samples indicate the TCLP findings may over-estimate the potential impact to the watershed. Prior to implementing this alternative, additional surface water monitoring will be required to determine if an impermeable cap is required to inhibit leaching of metals from the waste materials.

If an impermeable cap is needed, the consolidated waste rock top and side slopes would be first capped with a 60-mil high density polyethylene (HDPE) geomembrane liner, followed by a geocomposite drainage layer comprised of a geonet or uniaxial geogrid drainage media sandwiched between two layers of geotextile. The drainage layer would have a much higher rate of lateral transmissivity than the soil and would allow any moisture that drains through the cover soil to be carried away and drained to daylight eliminating the risk of hydrostatic pressure buildup between the geomembrane liner and the overlying soil cover. This material would then be covered with the 12-inch soil cover, 6-inch topsoil cover, native seed mix, erosion control fabric, and drainage features described previously.

The existing shaft described in Alternative 2 would also be closed as part of Alternative 3. As previously described, further investigation should be conducted to confirm and verify the details of the actual shaft closure; however, for purposes of this EE/CA, it will be assumed that an additional 3-foot thick PUF plug will be installed and then backfilled with clean native material to an approximate 90% maximum dry density.

Upon completion of corrective action, The Money Metals access road will be ripped, pocked with 18-inch deep pocks, and seeded with a native seed mix for a distance of 150 feet from the intersection with Big Bug Mesa Road to discourage pedestrian traffic and ATV or other vehicle traffic.

Providence Mine

There are four waste rock piles at the Providence mine site that will be consolidated into one single pile (WS-2/3; WS-4; WS-6; WS-8/9; WS-10). The consolidation location can be variable but it is suggested that it be located so that it can incorporate an existing waste rock pile to minimize the amount of material that will need to be relocated. For the purposes of this EE/CA it is assumed that the consolidation location will incorporate WS-2 and the eastern half of WS-8/9. Approximately 1,690 cy of waste rock would be relocated from WS-3, WS-4, WS-6, the western half of WS-8/9, and WS-10. The waste rock would be consolidated into a ½-acre footprint with a depth of 4 feet, a top slope grade of 3%, and side slopes built to a 3H:1V grade. The graded, consolidated waste rock would then be capped with a 12-inch thick soil cover, a 6-inch thick topsoil cover, seeded with a native seed mix, and covered with a biodegradable erosion control fabric. Areas adjacent to the consolidation pile will be regraded to allow preferential drainage flow paths in the area to be directed around the consolidation pile.

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Additional site work included in this alternative includes:

. Abandoning two existing groundwater wells per ADWR requirements.

. Performing a biological bat study and subsequent closure of the adit located near the eastern drainage. Depending on the results of the bat study, the adit will be closed with either a bat gate or PUF plug.

Action Specific ARARs

The following action-specific ARARs would be applicable to this alternative for both mine sites:

. Solid Waste Disposal Act (40 CFR Parts 257 and 258) – regulates the generation and disposal of solid waste. . RCRA Subtitle C (40 CFR Part 264 [TSDF]) – regulates the generation, treatment, storage, and disposal of hazardous waste. Would need to meet the substantive disposal requirements if mine waste is determined to be hazardous. . EPA National Pollutant Discharge Elimination System (NPDES) (CWA Section 402; 40 CFR Parts 122, 125 and 130.6) – would need to meet the substantive requirements regarding control of pollutants, specifically erosion and sediment controls during excavation activities. . Arizona Pollutant Discharge Elimination System (AZPDES) (18 A.A.C., Chapter 9, Articles 9 and 10; Arizona Revised Statutes [A.R.S.] Title 49, Chapter 2, Article 3.1; and the Clean Water Act as amended) – would need to meet the substantive requirements regarding control of pollutants, specifically erosion and sediment controls. . Arizona Air Pollution Control Act (18 A.A.C., Chapter 2), Non-point Source Emission Standards – dust suppression would be required to keep air-borne particulates to a minimum. . Arizona Native Plant Regulations (3 A.A.C., Chapter 3, Article 11 and Appendix A) – would need to comply with the substantive requirements of the protection of native plants listed in Appendix A. . Arizona Mined Land Reclamation Act (11 A.A.C., Chapter 2 and Arizona Revised Statutes, Chapter 5) – would need to comply with substantive requirements regarding erosion control and revegetation of the Site. . Well Construction and Licensing of Well Drillers (A.A.C. Title 12, Chapter 15, Article 8; A.R.S Title 45, Chapter 2, Article 10) – well abandonments are specifically described in A.A.C. R12-15-816.

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6.4.3.1 Effectiveness

Excavating/consolidating the waste rock and capping it at existing waste rock piles would have long-term effectiveness. Capping the consolidated waste rock piles with clean material provides the necessary barrier for receptors and eliminates the possibility of physical contact so that exploring hikers and wildlife that come upon the sites will not be exposed to direct contact with the waste rock.

When evaluating removal alternatives that include regrading, the optimal side slopes to reduce erosion potential are 3H:1V. Because of the limited space available regrading to the optimal angle of repose at Money Metals is not possible; however, regrading the Money Metals existing side slopes to 2H:1V slopes will help mitigate long-term erosion of the soil cover. Addition of the impermeable cap would increase the effectiveness of this alternative by impeding percolation of water through the waste materials thus decreasing leaching potential of heavy metals from the material. Grading the top slope so that it drains laterally to the east instead of over the top slope crest and down the side slope will further mitigate erosion of the cover side slopes. Burrowing animals do have the potential to compromise the cover by bringing capped waste rock back to the surface with their burrowing activities. Burrowing activities can be mitigated by incorporating a bio-barrier into the cap design. Costs within this report have assumed that a bio- barrier is not part of the cap design.

6.4.3.2 Implementability

Excavation/consolidation of the waste rock areas can be implemented with standard earth moving equipment and local contractors once equipment is mobilized to the mine areas. At Money Metals, placing cover materials over geosynthetic materials on 2H:1V slopes will be difficult and will require a slope stability analysis to be performed to determine the design requirements that will ensure the slope is stable during construction and after construction is complete. The Money Metals access road is rough and narrow with several hairpin switchbacks and will need to be improved to allow single lane equipment access.

General fill and topsoil is not readily available at either site and would therefore need to be trucked to the site from a local vendor site (Dewey, AZ). The soil covers at both the Money Metals and the Providence mines will require an inspection and maintenance plan to be developed and to remain in place to ensure that the integrity of the new covers is maintained over time.

6.4.3.3 Cost

Costs to implement Alternative 3 for each mine site area are as follows:

. Money Metals Mine without impermeable cap – $451,615 (capital costs), $56,355 (PRSC); with impermeable cap – $514,492 (capital costs), $56,355 (PRSC) (Table J3, Appendix J)

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. Providence Mine – $413,132 (capital costs), $56,355 (PRSC) (Table J4, Appendix J)

6.4.4 Alternative 4: Excavation and Off-Site Disposal (Providence Mine Only)

Alternative 4 includes the excavation and off-site disposal of waste rock piles WS-2/3, WS-4, WS-6, WS-8/9, and WS-10 at the Providence Mine site to remove soil impacted with concentrations of copper above their respective clean-up levels. The waste material would be hauled offsite to a Subtitle D Landfill with tandem axle dump trucks. The excavated areas would be smooth graded with slopes less than or equal to 3H:1V. The excavated areas would then be capped with a 6-inch thick topsoil cover, seeded with a native seed mix, and covered with a biodegradable erosion control fabric.

Additional site work included in this alternative includes:

. Abandoning two existing groundwater wells per ADWR requirements.

. Performing a biological bat study and subsequent closure of the adit located near the eastern drainage. Depending on the results of the bat study, the adit will be closed with either a bat gate or PUF plug.

The following action-specific ARARs would be applicable to this alternative:

. Solid Waste Disposal Act (40 CFR Parts 257 and 258) – regulates the generation and disposal of solid waste. Excavated materials would need to be legally disposed of in a Subtitle D landfill. . EPA National Pollutant Discharge Elimination System (NPDES) (CWA Section 402; 40 CFR Parts 122, 125 and 130.6) – would need to meet the substantive requirements regarding control of pollutants, specifically erosion and sediment controls during excavation activities. . Arizona Pollutant Discharge Elimination System (AZPDES) (18 A.A.C., Chapter 9, Articles 9 and 10; Arizona Revised Statutes [A.R.S.] Title 49, Chapter 2, Article 3.1; and the Clean Water Act as amended) – would need to meet the substantive requirements regarding control of pollutants, specifically erosion and sediment controls. . Arizona Air Pollution Control Act (18 A.A.C., Chapter 2), Non-point Source Emission Standards – dust suppression would be required to keep air-borne particulates to a minimum. . Arizona Native Plant Regulations (3 A.A.C., Chapter 3, Article 11 and Appendix A) – would need to comply with the substantive requirements of the protection of native plants listed in Appendix A. . Arizona Mined Land Reclamation Act (11 A.A.C., Chapter 2 and Arizona Revised Statutes, Chapter 5) – would need to comply with substantive requirements regarding erosion control and revegetation of the Site.

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. Well Construction and Licensing of Well Drillers (A.A.C. Title 12, Chapter 15, Article 8; A.R.S Title 45, Chapter 2, Article 10) – well abandonments are specifically described in A.A.C. R12-15-816.

6.4.4.1 Effectiveness

This action will remove impacted waste rock and soil from the site and provides the most effective means of eliminating environmental risks associated with site impacts. This alternative would be protective of human health and the environment in the short- and long-term and would comply with all ARARs. Waste rock and soil with concentrations of copper above the cleanup levels would be removed from the site, thereby eliminating mobility, toxicity, and volume of the contaminated soil at the site and meeting all of the Removal Action Objectives.

6.4.4.2 Implementability

Excavation of the waste rock areas can be implemented with standard earth moving equipment. The waste rock would be excavated and hauled with tandem axle dump trucks to the Gray Wolf Landfill (owned and operated by Waste Management, Inc.) located in Dewey, Arizona.

6.4.4.3 Cost

Costs to implement Alternative 4 are as follows:

Providence Mine – $746,075 (capital costs), $0 (PRSC) (Table J5, Appendix J).

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7.0 COMPARATIVE ANALYSIS OF REMOVAL ACTION ALTERNATIVES

A comparative analysis was conducted for each alternative presented in Section 6.0. Comparisons are based on the three evaluation criteria discussed earlier and are summarized in the following sections by mine area.

Table 10 Summary Comparison of Potential Alternatives

Money Metals Providence Alternative Effectiveness Implementability Cost Effectiveness Implementability Cost Alternative 1: - + NA +/- + NA No Action Alternative 2: +/- + $144,482 + + $86,885 Institutional Controls Alternative 3: $507,970 On-Site (w/out liner) Consolidation and +/- + +/- + $469,487 Capping $570,846 (w/ liner) Alternative 4: Excavation and Off- N/A N/A N/A + + $746,075 Site Disposal (+) Effectively meets criterion (-) Does not effectively meet criterion (+/-) Does not meet all criteria

7.1 MONEY METALS

7.1.1 Effectiveness

A summary of the effectiveness comparison of the each of the alternatives is presented in Table 11. The No Action alternative will not reduce the potential for exposure of site visitors to COPCs or provide a reduction in the toxicity, mobility, or volume of contaminants as site conditions will remain as they are now. Estimated risk from COPCs/COPECs in the waste rock material to potential receptors will not be decreased in the long-term.

The main risk to human receptors at Money Metals is from the chemical toxicity of arsenic and lead. Alternative 2 (Institutional Controls) does not provide a reduction in the toxicity, mobility, or volume of arsenic or lead but it does provide barriers that will limit human health exposures. Surface water monitoring will determine if ARARs (i.e., Arizona WQS) are being met and if the waste material is impacting the watershed. Long-term effectiveness of Alternative 2 will depend on inspection and maintenance practices that will be needed to ensure the institutional controls remain effective.

Alternative 3 (On-Site Consolidation and Capping) does not provide a reduction in the toxicity, mobility, or volume of COPCs/COPECs but does provide a barrier (vegetative cap) so that risk

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of exposure is reduced. If leaching of contaminants from the pile is indicated based on surface water sampling, addition of an impermeable liner to the cap will reduce mobility of the contaminants by preventing percolation of water through the material thus reducing the leaching potential; however, a slope stability analysis will be required to determine the design requirements that will ensure the slope is stable during and after construction is complete, which would hinder effectiveness. Engineering controls (i.e., dust control) will be required to ensure protectiveness of short-term exposure of workers during implementation. Short-term impacts to the environment may occur from vegetation clearing, earth moving, and development of staging areas. With proper Best Management Practices (BMPs) such as erosion control, impacts will be short-lived and correctable during revegetation. Long-term effectiveness of Alternative 3 will depend on environmental conditions and maintenance practices that protect the vegetative cover of the re-shaped piles.

Table 11 Effectiveness Comparison – Money Metals

Protectiveness

Alternative the the

term Solution term Impacts - and ARARs /TBCs ARARs Environmental Community Compliance with Ability Achieve to Environment Long Human Health Removal Objectives Implementation Overall Effectiveness Workers DuringWorkers

Alternative 1: - - + - - - + +/- No Action Alternative 2: +/- - + - +/- +/- + +/- Institutional Controls Alternative 3: + + + + + +/- + +/- On-Site Consolidation and Capping (+) Effectively meets criterion (-) Does not effectively meet criterion (+/-) Does not meet all criteria for effectiveness

7.1.2 Implementability

Alternative 2 is technically feasible and will require limited heavy equipment and personnel for implementation. Alternatives 3 will require readily available heavy equipment and personnel for implementation. General fill and topsoil for the soil cover will most likely not be available from nearby sources and will have to be trucked in to the site. Technical feasibility will be impacted if surface water monitoring indicates an impermeable liner is necessary. Placing cover materials over geosynthetic materials on 2H:1V slopes will be difficult. A slope stability analysis will be required to determine the design requirements that will ensure the slope is stable during construction and after construction is complete.

Alternatives 2 and 3 will require the development and implementation of a long-term maintenance program to ensure institutional controls remain effective and to protect the integrity of the vegetative cap.

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Community acceptance of either alternative is unknown; however, the site is not a frequently used site. Both alternatives preserve the historical aspect of the site, which may be of community importance. Neither alternative is expected to create community controversy.

Table 12 Implementability Comparison – Money Metals

Feasibility Availability

Alternative Control Property struction/ struction/ Acceptance Community site Disposalsite Capacity - Personnel Equipment Implementability Operational Post Site Removal Con Considerations Administrative Impact onImpact Adjoining Off

Alternative 1: No Action + + + + NA + + + + Alternative 2: Institutional Controls/Surface Water + +/- + + NA - + + +/- Monitoring Alternative 3: On-Site Consolidation and Capping +/- +/- + + NA - - + +/- (+) Effectively meets criterion (-) Does not effectively meet criterion (+/-) Does not meet all criteria for implementability

7.1.3 Cost

Capital costs for Alternative 3 are approximately four times higher than the proposed institutional controls proposed in Alternative 2. Both alternatives include costs for surface water monitoring, repairing the closed shaft, and for obliterating the access road into the site. Comparative costs are shown in Table 13.

Table 13 Cost Comparison – Money Metals Mine

(1) Post Removal Site Control Cost Total Cost

(Capital cost Alternative Capital Costs O&M Periodic Present Value + Cost Cost Present Value Cost) Alternative 1: No Action NA NA NA NA Alternative 2: Institutional Controls/Surface $93,851 $2,484 $50,631 $144,482 Water Monitoring Alternative 3: $51,615 $507,970 On-Site Consolidation and (with liner) (w/out liner) Capping $2,765 $56,355 $514,492 $570,846 (without liner) (w/ liner) (1) Post removal site control costs consist of calculation of a present value cost based on initial periodic O&M costs. The periodic O&M costs are shown in the table for reference only. Total alternative costs consist of the calculated present value cost and the capital cost.

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7.2 PROVIDENCE

7.2.1 Effectiveness

At Providence, human health risk from the COPCs is low based on anticipated future land uses. The No Action alternative would be protective of human health. The potential exposure of cattle to concentrations of copper exceeding the ecological risk-based cleanup level at Providence would be unaffected by the No Action alternative.

Alternative 2 (Institutional Controls) does not provide a reduction in the toxicity, mobility, or volume of copper but it does provide barriers that will limit cattle exposures. The proposed fencing material will not eliminate exposure of other wildlife species. Long-term effectiveness of Alternative 2 will depend on inspection and maintenance practices that will be needed to ensure the institutional controls remain effective.

Alternative 3 (On-Site Consolidation and Capping) does not provide a reduction in the toxicity, mobility, or volume of COPCs/COPECs but does provide a barrier (vegetative cap) so that risk of exposure is reduced. Engineering controls (i.e., dust control) will be required to ensure protectiveness of short-term exposure of workers during implementation. Short-term impacts to the environment may occur from vegetation clearing, earth moving, and development of staging areas. With proper Best Management Practices (BMPs) such as erosion control, impacts will be short-lived and correctable during revegetation. Long-term effectiveness of Alternative 3 will depend on environmental conditions and maintenance practices that protect the vegetative cover of the re-shaped piles.

Alternative 4 (excavation and off-site disposal) is highly effective in the long-term in reducing exposure levels to COPCs. Engineering controls (i.e., dust control) will be required to ensure protectiveness of short-term exposure of workers during implementation. Similar short-term impacts to the environment may occur during Alternative 4 as described for Alternative 3. Impacts are short-term and correctable with BMPs. Waste materials will be removed from the Providence site and confirmation sampling will confirm that COPCs above the action level have been removed upon completion of the removal action.

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Table 14 Effectiveness Comparison – Providence

Protectiveness

Alternative term Solution term Impacts - RARs /TBCs RARs and the A Environmental Community Compliance with Ability Achieve to Environment Long Human Health Removal Objectives Implementation Overall Effectiveness Workers DuringWorkers Alternative 1: + - + +/- - - + +/- No Action Alternative 2: + +/- + + +/- +/- + +/- Institutional Controls Alternative 3: + + + + + + + + On-Site Consolidation and Capping Alternative 4: + + + + + + + + Excavation and Off-Site Disposal (+) Effectively meets criterion (-) Does not effectively meet criterion (+/-) Does not meet all criteria for effectiveness

7.2.2 Implementability

Alternative 2 is technically feasible and will require limited heavy equipment and personnel for implementation. Alternatives 3 and 4 will require readily available heavy equipment and personnel for implementation and are technically feasible; however, general fill and topsoil will most likely not be available from nearby sources and will have to be trucked in to the site.

Alternatives 2 and 3 will require the development and implementation of a long-term maintenance program to ensure institutional controls remain effective and to protect the integrity of the vegetative cap. Because waste material will be permanently removed from the site in Alternative 4, long-term maintenance is not required for that alternative.

Community acceptance for any of the alternatives is unknown; however, the site is not a frequently used site. The nearby communities may object to off-site disposal and transportation of waste materials due to increased vehicle traffic and potential dust generation. Overall, none of the alternatives are expected to create community controversy.

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Table 15 Implementability Comparison

Feasibility Availability

Alternative site site roperty - Control P Acceptance Community Off Disposal Capacity Personnel Equipment Implementability Operational Post Site Removal Construction/ Considerations Administrative Impact onImpact Adjoining

Alternative 1: + + + + NA + + + + No Action Alternative 2: + +/- + + NA - + + +/- Institutional Controls Alternative 3: On-Site Consolidation and Capping + +/- + + NA - - + +/- Alternative 4: + + + + + + - +/- +/- Excavation and Off-Site Disposal (+) Effectively meets criterion (-) Does not effectively meet criterion (+/-) Does not meet all criteria for implementability

7.2.3 Cost

Total cost for Alternative 2 is less than the total cost of either Alternative 3 or Alternative 4 at the Providence Mine. Alternative 2 costs include PRSC costs associated with long-term monitoring and maintenance of the institutional controls to ensure they remain effective over time. Alternative 3 includes PRSC costs associated with long term monitoring and maintenance of the waste rock cover. All of the alternatives include costs for closing the adit, for closing the two existing groundwater wells, and for obliterating the access road into the site. Comparative costs for the Providence Mine alternatives are shown in Table 14.

Table 16 Cost Comparison – Providence Mine

Post Removal Site Control Cost(1) Total Cost (Capital cost Alternative Capital Costs O&M Periodic Present Value + Cost Cost Present Value Cost) Alternative 1: No Action NA NA NA NA Alternative 2: Institutional Controls $36,254 $2,484 $50,631 $86,885 Alternative 3: On-Site Consolidation and $413,132 $2,765 $56,355 $469,487 Capping Alternative 4: Excavation and Off-Site $746,075 NA NA $746,075 Disposal (1) Post removal site control costs consist of calculation of a present value cost based on initial periodic O&M costs. The periodic O&M costs are shown in the table for reference only. Total alternative costs consist of the calculated present value cost and the capital cost.

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8.0 RECOMMENDED REMOVAL ACTION ALTERNATIVE

The alternatives evaluated for potential removal actions at the Money Metals and Providence mines are:

Money Metals Mine . Alternative 1: No Action . Alternative 2: Institutional Controls (with surface water monitoring) . Alternative 3: On-Site Consolidation and Capping (with surface water monitoring)

The Money Metals Mine currently does not see much public access traffic and what little there is could be further reduced with the proposed institutional controls that would limit public access. The limited data currently available regarding water quality downstream of the waste rock pile does not definitively suggest that there is a water quality problem. Additional monitoring and sampling, identified in Alternative 2, to confirm whether or not there is a water quality issue would be justified before more expensive alternatives are pursued.

Providence Mine . Alternative 1: No Action . Alternative 2: Institutional Controls (fencing) . Alternative 3: On-Site Consolidation and Capping . Alternative 4: Excavation and Off-Site Disposal

The Providence Mine analytical data indicates there is not a significant risk posed to human health from the waste rock piles. Concentrations of copper in some of the waste rock/tailings material are greater than recommended concentrations of copper in soil for grazing livestock. The area currently accommodates cattle grazing and will continue to be available as a resource for this activity. The Alternative 2 Institutional Controls provides the most cost effective means of eliminating the risk to grazing cattle by preventing exposure to affected material. Therefore, Alternative 2 is recommended as the preferred alternative for the Providence Mine.

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9.0 REFERENCES

Anderson, C.A. and Blacet, P.M., 1972a, Precambrian Geology of the Northern Bradshaw Mountains, Yavapai County, Arizona: USGS Bulletin 1336, p. 82.

_____, 1972b, Geologic Map of the Mount Union Quadrangle Yavapai County, Arizona: USGS Map GQ-997, 1:62,500.

Arizona Department of Environmental Quality (ADEQ), 1990. Evaluation of Background Metals Concentrations in Arizona Soils and Development of a Statewide Database. Prepared by Scott Ball, The Earth Technology Corporation for ADEQ. Dated November 29, 1990.

Arizona Fish and Game Department (AZFGD), 2009. Heritage Data Management System. Eastwood Alum Root and Broadleaf Lupine species accounts. http://www.azgfd.gov/w_c/edits/hdms_abstracts_plants.shtml. Accessed November 10, 2009.

Canty, J. Michael and Greeley, Michael N., 1987, History of Mining in Arizona, Mining Club of the Southwest Foundation, Tucson, Arizona.

Ecology and Environment, Inc. 2003. Potentially Responsible Party Search Findings Report, Big Bug Watershed Mines, Prescott Nation Forest, Yavapai County, Arizona. Prepared for the USDA Forest Service. Dated May 2003.

_____, 2004. Preliminary Assessment/Site Inspection, Big Bug Mines, Prescott National Forest, Yavapai Count, Arizona. Prepared for the USDA Forest Service. Dated August 2004.

Ford, Karl L., Bureau of Land Management (BLM), 2004. Risk Management Criteria for Metals at BLM Mining Sites, Technical Note 390 (revised), BLM/RS/ST-97/001+1703. Dated October 2004.

Hamilton, Steven J., 2004. Review of selenium toxicity in the aquatic food chain. Science of the Total Environment 326 (2004) 1-31.

National Geographic, 2002. Field Guide to the Birds of North America. Northern Goshawk and Spotted Owl species accounts. National Geographic Society. Washington, D.C.

Neubert, J.T., 1995. Mineral Appraisal of Priority Areas in the Western Part of the Prescott National Forest, Arizona: U.S. Bureau of Mines Open File Report MLA 15-95, p. 119.

Sayre, John, 1954. Ghost railroads and ghost towns of central Arizona. Library of Congress.

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Stein, Pat H. and Skinner, Elizabeth J., 1997, Mining the Big Bug: Archaeological Investigations at Twelve Historic Sites between Mayer and Dewey, Yavapai County, Arizona, SWCA Inc., Flagstaff

United States Army Center for Health Promotion and Preventative Medicine (USACHPPM), 2007. Wildlife Toxicity Assessment for Thallium. Prepared by Health Effects Research Program, Environmental Health Risk Assessment Program. USACHPPM Document No. 37-EJ1138-01O. Dated December 20007.

U.S. Department of Agriculture Forest Service (USFS), 2002. Characterization of Big Bug Watershed, Abandoned Mine Survey and Initial Sampling for Possible CERCLA Action. Anne P. Fischer and Michael A. Smith.

_____, 2009. Statement of Work, Big Bug Watershed: Money Metals and Providence Mines Site, Engineering Evaluation/Cost Analysis, R3-09-44. Dated August 10, 2009.

_____, 2010a. Personal communication with Anne Fischer, Arizona Statewide On-Scene Coordinator. January 8, 2010.

_____, 2010b. Bradshaw Ranger District, Prescott National Forest, Big Bug & Money Metals EE/CA Project; Wildlife Specialist Report & Biological Assessment & Evaluation; Threatened, endangered, proposed, sensitive, management indicator species, and migratory birds. Dated 15 October 2010.

U.S. Department of the Interior (USDOI), 1989. National Irrigation Water quality Program Information Report No. 3. Guidelines for Interpretation of Biological Effects of Selected Constituents in Biota, Water, and Sediment. Selenium. Participating agencies: Bureau of Reclamation, U.S. Fish and Wildlife Service, U.S. Geological Survey, Bureau of Indian Affairs. Dated November 1998.

U.S. Environmental Protection Agency (EPA), 1988. CERCLA Compliance with Other Laws Manual: Interim Final. EPA/540/G-89/006 (August).

_____, 1989. CERCLA Compliance with Other Laws Manual: Part II. Clean Air Act and Other Environmental and State Requirements. EPA/540/G-89/009 (August).

_____, 1993. Guidance on Conducting Non-Time-Critical Removal Actions Under CERCLA. EPA/540-R-93-057 (August).

_____, 2001. A Guide to Developing and Documenting Cost Estimates During the Feasibility Study. EPA 540-R-00-002. July 2000.

_____, 2000b. EPA Abandoned Mine Site Characterization and Cleanup Handbook. EPA/910- B-00-001. Washington, DC: U.S. EPA. August 2000.

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_____, 2003. Ecological Soil Screening Levels for Aluminum, Interim Final. OSWER Directive 9285.7-60. Dated November 2003.

_____, 2005. Ecological Soil Screening Levels for Antimony, Interim Final. OSWER Directive 9285.7-61. Dated February 2005.

_____, 2006. Ecological Soil Screening Levels for Silver, Interim Final. OSWER Directive 9285.7-77. Dated September 2006.

_____, 2007a. Ecological Soil Screening Levels for Manganese, Interim Final. OSWER Directive 9285.7-71. Dated April 2007.

_____, 2007b. Ecological Soil Screening Levels for Nickel, Interim Final. OSWER Directive 9285.7-76. Dated March 2007.

_____, 2007c. Ecological Soil Screening Levels for Selenium, Interim Final. OSWER Directive 9285.7-72. Dated July 2007.

_____, 2008. Ecological Soil Screening Levels for Chromium, Interim Final. OSWER Directive 9285.7-66. Revised April 2008.

U.S. Geological Survey (USGS), 2003. Waste Pile and Water Sampling presented by Kathleen S. Smith, USGS at the Billings Symposium / ASMR Annual Meeting, Assessing the Toxicity Potential of Mine-Waste Piles Workshop. June 1, 2003.

Western Regional Climate Center (WRCC), 2009. Temperature and Precipitation Data for Prescott, Arizona. http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?az3713. Accessed September 18, 2009.

Weston Solutions, Inc. (Weston), 2009. Final Sampling and Analysis Plan, Engineering Evaluation / Cost Analysis, Big Bug Watershed: Money Metals and Providence Mines, Bradshaw Mountains, Prescott National Forest, AZ. Dated November 2009.

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FIGURES

APPENDIX A

Photographic Log

APPENDIX B

Potential ARARs and TBCs

APPENDIX C

Data Summary Tables

APPENDIX D

Field Notes and Field Sketches

APPENDIX E

Sample Location GPS Coordinates

APPENDIX F

Laboratory Analytical Reports

APPENDIX G

Initial Data Screening Tables

APPENDIX H

Site Conceptual Exposure Model

APPENDIX I

Waste Source Volume Calculations

APPENDIX J

Cost Tables