FINAL Record of Decision Amendment for the Eagle Mine ... · NCP National Oil and Hazardous...

The Eagle River

FINAL

Record of Decision Amendment for the

Eagle Mine Superfund Site Operable Unit 1

Eagle County, Colorado

September 2017

Colorado Department of Public Health & Environment

4300 Cherry Creek Drive South Denver, CO 80246-1530

U.S. Environmental Protection Agency Superfund Remedial Program

Office of Ecosystems Protection & Remediation U.S. EPA – Region 8 1595 Wynkoop Street

Denver, CO 80202-1129

OU1 ROD Amendment i September 2017

Table of Contents

Section Page ACRONYMS ............................................................................................................................................... iii

1.0 Introduction and Statement of Purpose ......................................................................................... 1

1.1 Site Name and Location ............................................................................................................... 1

1.2 Administrative Record .................................................................................................................. 2

1.3 Statement of Basis and Purpose of this Amendment .................................................................... 3

1.4 Authorizing Signatures and Support Agency Acceptance of Remedy ......................................... 4

2.0 Site History, Contamination, and the 1993 Selected Remedy ...................................................... 6

2.1 Site History Prior to 1993 Record of Decision ............................................................................. 6

2.2 Site Contamination ....................................................................................................................... 7

2.3 Summary of the 1993 Selected Remedy ....................................................................................... 8

2.4 Activities Since the Issuance of the 1993 Record of Decision ..................................................... 9

2.5 Contaminants of Concern ........................................................................................................... 10

2.6 Cleanup Levels ........................................................................................................................... 11

2.6.1 Surface Water Cleanup Levels ................................................................................................ 11

2.6.2 Arsenic Effluent Limit ............................................................................................................ 12

3.0 Rationale for Amended Remedy ................................................................................................. 13

3.1 Operable Units Definitions ......................................................................................................... 13

3.2 Cleanup Levels and Additional Water Capture and Treatment .................................................. 13

3.3 Institutional Controls .................................................................................................................. 13

4.0 Description of Amended Remedy ............................................................................................... 14

4.1 Definitions of Operable Units .................................................................................................... 14

4.2 Adoption of New Cleanup Levels and Expansion of Water Capture and Treatment System .... 14

4.3 Institutional Controls .................................................................................................................. 15

4.4 Remedial Action Objectives ....................................................................................................... 15

5.0 Evaluation of Amended Remedial Action .................................................................................. 17

5.1 Overall Protection of Human Health and the Environment ........................................................ 17

5.2 Compliance with Applicable or Relevant and Appropriate Requirements ................................. 18

5.3 Long-Term Effectiveness and Permanence ................................................................................ 18

5.4 Reduction of Toxicity, Mobility, or Volume through Treatment ............................................... 18

5.5 Short-Term Effectiveness ........................................................................................................... 18

5.6 Implementability ......................................................................................................................... 19

5.7 Cost ............................................................................................................................................. 19

5.8 Regulatory Acceptance ............................................................................................................... 19

5.9 Community Acceptance ............................................................................................................. 19

OU1 ROD Amendment ii September 2017

Table of Contents (Cont.)

Section Page

6.0 Support Agency Comments ...................................................................................................... 20

7.0 Statutory Determinations/Declarations .................................................................................... 21

8.0 Public Participation ................................................................................................................... 22

9.0 Responsiveness Summary ........................................................................................................... 23

10.0 References ................................................................................................................................... 29

Table Table 1 Comprehensive Site-Wide Chronology Table 2 Summary of Water Quality Standard Equations by Segment Table 3 Focused Feasibility Study Timeline

Figures Figure 1 Vicinity Map Figure 2 Site Features Figure 3 Eagle River Basin Segments Figure 4 Rock Creek and Belden Areas Figure 5 Collection Trench Location

Appendices A Technical Impracticability Evaluation Report B Applicable or Relevant and Appropriate Requirements – OU1 C Detailed Cost Estimate

OU1 ROD Amendment iii September 2017

ACRONYMS

µg/l Micrograms per liter Agencies CDPHE and the EPA ARAR Applicable or Relevant and Appropriate Requirements CBS CBS Operations, Inc. CDPHE Colorado Department of Public Health and Environment CDPS Colorado Discharge Permit System CD/RAP Consent Decree/Remedial Action Plan CERCLA Comprehensive Environmental Response, Compensation and Liability Act CFR Code of Federal Regulations COC Contaminant of concern CTP Consolidated Tailings Pile CSWQS Colorado Surface Water Quality Standard EC Environmental Covenant EPA U.S. Environmental Protection Agency ERWC Eagle River Watershed Council FFS Focused Feasibility Study IC Institutional control IRM Iron-rich material NCP National Oil and Hazardous Substances Pollution Contingency Plan OU Operable Unit OTP Old Tailings Pile PRP Potentially Responsible Party RAO Remedial Action Objective RN Restrictive Notice ROD Record of Decision Site Eagle Mine Superfund Site U.S.C. United States Code WRP Waste Rock Pile

OU1 ROD Amendment 1 September 2017

1.0 Introduction and Statement of Purpose

1.1 Site Name and Location

Site Name: Eagle Mine Superfund Site Site Location: Minturn, Colorado CERCLIS ID Number: COD081961518 Operable Unit/Site: 01 Original Record of Decision: EPA/ROD/R08-93/068, signed March 29, 1993

The Eagle Mine Superfund Site (Site) is a large abandoned mining and milling facility located along the banks of the Eagle River near Minturn, Colorado (Figure 1). The boundaries of the Site are defined by the areas of past mining activity between the towns of Red Cliff and Minturn. Impacts from Site contaminants historically extended downstream in the Eagle River. The 235-acre Site includes the Eagle Mine Workings, the abandoned town of Gilman, the mill tailings pond areas, Rex Flats, Rock Creek Canyon, waste rock, and roaster pile areas (Figure 2). The Site is bordered on the south and west by the White River National Forest which includes the Holy Cross Wilderness Area. Access to the wilderness area runs through the Site and next to the historic location of the Old Tailings Pile (OTP) (U.S. Environmental Protection Agency [EPA] 1993).

For larger and complex sites such as the Eagle Mine Site, the EPA traditionally divides sites into Operable Units (OU). The OUs may be defined by media, geographic areas, or any other features appropriate to the site. For the Eagle Mine Site, the EPA has designated three OUs: OU1 (historically soil and water media); OU2 (soils in the former town of Gilman); and OU3 (newly designated to encompass the soil portion of OU1).

As described below, one of the purposes of this Record of Decision (ROD) Amendment is to re-define the OUs for this Site; specifically OU1 and OU3.


1.2 Administrative Record

This ROD Amendment is a part of the Administrative Record for the Site. The complete Administrative Record is available on disk by request, or can be viewed at the following locations:

EPA Superfund Records Center, Region 8

1595 Wynkoop St. Denver, CO 80202

303-312-7273 or 800-227-8917 (toll free) Leave message to request a copy of the Administrative Record on disk.

Colorado Department of Public Health and Environment

HMWMD Records Center 4300 Cherry Creek Dr. S.

Denver, CO 80246 303-692-3331 or 888-569-1831 (toll free)

(fax) 303-759-5355 Appointment recommended.

Minturn Town Hall

302 Pine St. Minturn, CO 81645

970-827-4104

The following documents are available in the Administrative Record and their contents support the need for this Amendment and the conclusions presented herein:

• Superfund Record of Decision: Eagle Mine, CO, OU1, EPA, March 29, 1993;

• Focused Feasibility Study, Eagle Mine Site, NewFields prepared for CBS Operations, Inc. (CBS), July 26, 2013;

• Five-Year Review Report, Fourth Five-Year Review Report for Eagle Mine Superfund Site, EPA ID COD081961518, EPA, September 2013;

• Technical Impracticability Evaluation Report, Arsenic in Surface Water at the Eagle Mine Superfund Site, Operable Unit 1, Colorado Department of Public Health and Environment (CDPHE), March 2016;

• Eagle Mine Annual Report - 2016, NewFields prepared for CBS, April 14, 2017.

• Focused Feasibility Study Addendum, Eagle Mine Site, NewFields prepared for CBS, February 2017; and

• Eagle Mine Superfund Site Proposed Plan to Amend the Operable Unit 1 Record of Decision, EPA and CDPHE, June 2017.


1.3 Statement of Basis and Purpose of this Amendment

Under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) Section 117(c), of Title 42 of the United States Code (U.S.C.) § 9617(c), and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), Title 40 of the Code of Federal Regulations (CFR) § 300.435(c)(2)(ii), if the EPA proposes to fundamentally alter the basic features of the selected remedy with respect to scope, performance, or cost, then the EPA is required to publish the proposed amendment, receive comments, and provide an opportunity for comment. CDPHE and the EPA (jointly referred to as “the Agencies”) plan to fundamentally alter the basic features of the selected remedy for OU1.

This ROD Amendment addresses three topics for the Site: 1) definitions and scope of the OUs; 2) modification to cleanup levels in surface water for cadmium, copper, and zinc and adoption of the Site-specific arsenic remedial goal (i.e., end-of-pipe effluent standard) with the subsequent expansion of the current groundwater collection system to meet the new cleanup levels; and 3) incorporation of new institutional control (IC) instruments adopted by the state of Colorado since the 1993 ROD to protect remedial components. While the first and third topics are primarily administrative, the second topic requires additional remediation beyond the operation of the existing remedy as described in the 1993 ROD for OU1 (EPA 1993).


2.0 Site History, Contamination, and the 1993 Selected Remedy

Table 1 provides a comprehensive, Site-wide chronology for the Eagle Mine Site.

2.1 Site History Prior to 1993 Record of Decision

Mining began in the area in 1879. In 1905, the Pittsburg Gold and Zinc Company built a mill in Gilman to roast and separate ore. By 1916, the Empire Zinc Company of Colorado completed consolidation of the principal mines into what is known as the Eagle Mine. An underground mill was constructed and mill tailings were transported via pipeline down the valley and deposited first in the OTP, and later into the New Tailings Pile that is now called the Consolidated Tailings Pile (CTP). The primary metals mined included zinc, gold, silver, lead, and copper. The Eagle Mine closed in 1984 when electrical power to the mine was shut off and the mine workings flooded (CDPHE 2016).

In general, the Site’s contaminants encompass heavy metals as a result of metal mining. The Eagle River is the major surface water resource affected by the metals contamination from the Site. The headwaters of the Eagle River originate about 15 miles above Red Cliff. The Eagle River flows north-northwest through the Site to the town of Avon where it turns generally westward until it joins the Colorado River at Dotsero (Figure 1). The Eagle Mine workings were developed in the lower levels of Battle Mountain to the east of the Eagle River and just south of Rock Creek (Figure 2). Several wetland and former wetland areas border the Eagle River between Red Cliff and Minturn. Rex Flats, a low lying area which was once a wetland, is located on the east side of the Eagle River across from the OTP area about three miles north of the mine. The OTP area was a hay meadow prior to the advent of mining operations. Another tailings disposal unit, the New Tailings Pile is called the CTP in this ROD Amendment. The CTP is located about a mile north of the OTP just west of the Eagle River and south of Cross Creek (Figure 2). The Maloit Park Wetland along Cross Creek has been affected by surface water and groundwater flowing from this pile (EPA 1993).

The Eagle River is used as a water supply and for recreation (i.e., rafting and kayaking). Fishing also occurs on the Eagle River from the headwaters to the Colorado River. There are numerous diversions from the Eagle River for municipal supply, stock watering and irrigation downstream from the confluence with Gore Creek. The closest residence to the Site is 1,000 feet to the northeast along Highway 24. Minturn, the closest population center, with 1,500 people, has filter ponds and municipal wells located northwest of the CTP and along Cross Creek. Minturn draws its public water supply both from area wells and from Cross Creek (EPA 1993).

The EPA listed the Site on the National Priorities List in 1986. Cleanup at the Site began in 1988 under a Consent Decree/Remedial Action Plan (CD/RAP) between the state of Colorado and the Potentially Responsible Party (PRP). In 1990, the cleanup agreement was amended to include a water treatment plant to treat contaminated water from the mine workings and the CTP (CDPHE and EPA 2017).

Water-related remedial activities completed to date as required by the CD/RAP include the following (CDPHE and EPA 2017):

• A Mine Closure Program to seal known channels and pathways of flow from the mine workings and to grout fracture zones having identifiable discharge or seepage;

• A groundwater extraction system constructed near the northern and eastern toes of the CTP to collect and pump contaminated groundwater from beneath the CTP to the water handling system and later the water treatment plant;


• A groundwater diversion trench known as the upgradient diversion trench constructed to the northwest of the CTP to direct the flow of clean groundwater away from the CTP and toward Maloit Park;

• A “water handling system,” which included:

o A temporary run-off control system at the OTP, Rex Flats and the CTP; and

o A system to pump collected water into the Eagle Mine workings. The pump system included a surge pond at the CTP, a pump station, and a closed pipeline.

• A water treatment plant constructed in 1990, after the original treatment scheme proved ineffective to accommodate rising water levels in the mine. Soon after the PRP began to implement the "water handling system", the water level in the mine rose above approximately 8,520 feet above mean sea level. Contaminated water began to seep out through bedrock fractures, resulting in an increase in metals concentrations in the Eagle River. The CD/RAP was then amended in May 1990 to require the PRP to; 1) cease pumping water into the mine; 2) construct an additional surge pond at the CTP; 3) construct a collection system to collect seeps along Rock Creek; and 4) install and operate a water treatment plant.

• A stream gage installed at a location along the Eagle River north of Rex Flats (Figure 3) by the PRP, which met all applicable requirements of the U.S. Geological Survey for such gages. The cleanup agreement requires that the PRP “provide for operation and maintenance of the stream gage until such time as the water quality objectives for the Eagle River” are achieved;

• Permanent run-on and run-off control systems (diversion ditches) at the CTP and the waste rock piles (WRPs) were designed to handle the run-off from a precipitation event having an intensity equal to that of a 500-year return period event; and

• The connection of a nearby residence at the mouth of Cross Creek to the town of Minturn’s water system by the PRP.

In the early 1990s, the Colorado Division of Wildlife conducted studies in support of the project in response to a request by CDPHE. They found that heavy metal concentrations in the Eagle River from Belden to Minturn were above levels that are acutely and/or chronically toxic to some trout species. In addition, the fish and aquatic macroinvertebrate communities were severely reduced in this reach of the Eagle River (EPA 2013).

2.2 Site Contamination

Contaminated water in 1993 included: the mine pool water within the mine workings; the historic pond where water was stored at the CTP from various sources; the water flow occurring when areas containing mine waste become saturated (from rain, meltwater or other sources) and the excess water flows over the land (i.e., runoff); and the groundwater below the OTP, CTP, Rex Flats and Rock Creek. Groundwater in the Belden area was also contaminated, most likely from a multitude of waste sources including ballast material beneath the rail lines that may contain roaster wastes, mill tailings or waste rock. Groundwater has and continues to pose a threat to the environment in areas where groundwater discharge impacts surface water quality.

The most significant environmental impact from Site contaminated mine wastes and water was the degradation of Eagle River water quality due to high concentrations of dissolved metals. All known contamination in Rock Creek and Cross Creek originates from the Site. Segment 2 of the Eagle River (Figure 3) has been impacted by non-Site related mine wastes (EPA 2013).


2.3 Summary of the 1993 Selected Remedy

In 1993, the EPA had only designated two OUs for the Site. The 1993 ROD encompassed soil and water media within OU1, addressing the principal sources of mine waste pollution that impacted the Eagle River and certain groundwater resources. The purpose was to control the transport of toxic metals originating from various Site sources to the Eagle River and to Site groundwater. The sources identified in the 1993 ROD included the Eagle Mine, the Roaster Pile area, the WRPs, Rex Flats, the OTP, the CTP and the Maloit Park Wetland. (OU2 represents soils in the former town of Gilman.)

The environmental receptors of concern were (and still are) the fresh-water biota, particularly the Eagle River aquatic life. Human health concerns included potential impacts and possible re-entrained soils contamination from the CTP, especially employees and students of the Minturn Middle School (now the Vail Ski and Snowboard Academy) and full-time residents who live adjacent to the school from wind-blown particulate matter from the CTP. There were also human health concerns related to potential contamination of the Town of Minturn drinking water wells.

The remedial action objectives (RAOs) pertinent to water set forth in the 1993 ROD were as follows:

• Improve the quality of water in the Eagle River to support Class 1 aquatic life use; and

• Control or eliminate human ingestion of contaminated groundwater.

To meet the water-specific RAOs, major components of the selected remedy within the 1993 ROD include:

• Installation of a conveyance and collection system to collect additional mine seepage along Rock Creek;

• Diversion of Rock Creek upgradient of contaminated mine seepage;

• Revegetation in the area of Roaster Pile #1 and associated drainage and monitoring of seep water quality below the Roaster Pile #1 area;

• Rainfall run-off monitoring at the WRPs and leachability tests on the waste rock, with evaluation of the data for possible future action;

• Development of inspection and maintenance plan to ensure the long-term integrity of structures and facilities associated with the Eagle Mine Site;

• Implementation of use restrictions for groundwater at the Rex Flats and OTP;

• Accelerated re-vegetation at Rex Flats;

• Rapid completion of the cap on the CTP, draining and capping of the historic pond, extraction and treatment of leachate/groundwater from the CTP extraction trenches, enhancement of the CTP extraction trenches and construction of a new up-gradient groundwater diversion structure;

• Relocation of the town of Minturn drinking water wells;

• Continued treatment of contaminated mine seepage and leachate/groundwater from the CTP at the water treatment plant (until Site cleanup goals can be met without such treatment), dewatering of the treatment sludge, and disposal of the dewatered sludge in on-site lined cells on the CTP;

• Removal of the contaminated soils and sediments from the Maloit Park Wetland, seepage control from the CTP, and rapid addition of topsoil and vegetation; and


• Regular monitoring of surface water, groundwater, mine pool water within the mine workings and biota at key locations on the Site and downstream of the Site to determine progress toward cleanup goals.

The 1993 ROD also included an acknowledgement of ongoing research into alternate remedies and encouraged the PRP to continue this research.

2.4 Activities Since the Issuance of the 1993 Record of Decision

The 1993 ROD resulted in additional remediation beyond the 1988 CD/RAP, for which a cleanup agreement between the EPA, the state of Colorado and the PRP was signed in 1996. The 1996 cleanup agreement describes various remedial activities requiring regular reporting and analysis of collected data. Regular reporting includes quarterly data reports, annual site monitoring and activity reports, annual surface water loading reports, data evaluation reports and aquatic biological monitoring reports. The 1996 cleanup agreement also included (only water-related items are listed below):

• Storm event/snowmelt surface water monitoring;

• Roaster pile springs monitoring;

• Groundwater monitoring;

• CTP extraction trench monitoring;

• Rock Creek seep collection;

• Rock Creek culvert extension;

• Modification of CTP extraction trenches;

• Evaluation, modification and reconstruction of upgradient diversion trench;

• Operation of water treatment plant;

• Development of long-term inspection and maintenance plan for the conveyance and collection systems; and

• Development of a “Biological Criteria Approach” for determining new surface water standards for the Eagle River.

In 1992, the PRP reached agreement with the town of Minturn to install two new drinking water wells for the town, located upgradient of any possible influence from the CTP. This agreement was not formally part of the cleanup agreement, but was included in the 1993 ROD.

In 1999, the EPA issued an explanation of significant differences from the OU1 ROD. The explanation of significant differences formally incorporated the Liberty well as part of the selected remedy, which intersects a 980 foot-deep tunnel that allows water to enter the mine workings. The Liberty well reduces the flow to and the water level in the mine pool.

Reporting and monitoring requirements were modified as the Site progressed into the operation and maintenance phase. Only annual reports are now required.

Waste rock was not removed as part of the original OU1 remedy. Rather, the OU1 ROD required a detailed study of metals loading from 12 identified WRPs. During the actual study, four additional WRPs beyond the original 12 identified in the ROD were analyzed, for a total of 16. The Focused Feasibility Study (FFS) (CBS 2013) provides detailed analysis for the leaching potential of each pile. Samples were


collected for acid generation potential, grain size analysis, column leach tests and total metals content. Rainfall/run-off monitoring was also conducted. While metal concentrations were elevated in some of the piles, most possessed little to no potential for acid generation and classified as minor sources of leachable metals. The WRP study required by the OU1 ROD identified the piles with the greatest potential to generate acid mine drainage and as a result, two surface water collection systems were constructed to collect water from WRP-8 for treatment at the water treatment plant. Results of water quality analysis conducted to date do not link run-off from the existing WRPs to the increase in metals concentrations in the Eagle River that occurs annually in March and April, prior to spring run-off (CDPHE and EPA 2017, CBS 2013).

In addition to the completed remedial actions summarized above, some remedial activities at the Site are ongoing. Ongoing remedial activities include:

• 100 to 300 gallons per minute of mine pool water from within the mine workings, Belden, and groundwater collection trenches are treated daily at the water treatment plant. Water from WRP-8 is treated seasonally;

• 90 to 150 gallons per minute of clean water pumped through the Liberty well is diverted away from the mine pool;

• Inspections of the conveyance and collection systems are conducted five days per week with necessary repairs conducted as needed;

• The collection system at WRP-8 is inspected and repaired as necessary to maintain operation; and

• River sampling, reporting, and compliance monitoring for discharge permits at the water treatment plant and the Liberty well are performed as required.

Continued operation of ongoing remedial activities, including drawdown from the mine pool water within the mine workings and active water treatment, is required to maintain the water quality improvements that have occurred since remediation has begun; contaminant concentrations in surface water and groundwater have decreased and the aquatic ecosystem is recovering (CDPHE and EPA 2017).

2.5 Contaminants of Concern

In 1993, the ROD listed the main contaminants of concern (COCs) for human receptors as arsenic, cadmium, copper, lead, and zinc; however, no excess lifetime cancer risks to human health through exposure to groundwater or surface water were identified. The main concern at the Site is the potential for adverse effects to aquatic organisms in the Eagle River. Heavy metal concentrations (cadmium, copper, and zinc) in the Eagle River from Belden to Minturn were above levels that are acutely and/or chronically toxic to some trout species. In addition, the fish and aquatic macroinvertebrate communities were severely reduced in this reach of the Eagle River (EPA 1993).

Arsenic was not recognized as a COC for surface water in the 1993 Eagle Mine OU1 ROD because arsenic was not detected in the Eagle River using the laboratory methods in effect at the time. Therefore, no applicable or relevant and appropriate requirements (ARARs) for arsenic were identified in the ROD and arsenic was not included in the on-going surface water monitoring program at the Site. Recent sampling conducted by the PRP in 2012 and 2013 using updated analytical methodologies and achieving lower detection limits, however, confirmed that arsenic is present at the Site in concentrations that exceed the current Colorado Surface Water Quality Standard (CSWQS) of 0.02 micrograms per liter (µg/l). As a result, the EPA and the state of Colorado determined that arsenic is a COC for surface water and that the 0.02 µg/l CSWQS is a potential ARAR for the Site (CHPHE 2016, Appendix A).


For this ROD Amendment, the main COCs for surface water (including groundwater expressing as surface water) are arsenic, cadmium, copper and zinc.

2.6 Cleanup Levels

2.6.1 Surface Water Cleanup Levels

In the 1993 ROD, numerical cleanup levels (remediation goals) were identified in consideration of the Site characteristics, risk assessment results and legal standards and requirements. Those clean up levels (remediation goals) are either applicable or relevant and appropriate to the remediation. At that time, contaminant-specific ARARs included the Colorado Groundwater Standards and the Colorado Surface Water Quality Standards.

For this ROD Amendment, the identified cleanup levels (which are the same as the ARARs listed in Appendix B) for cadmium, copper and zinc are water quality standards for the Eagle River, as established by the Colorado Water Quality Control Commission in 2008.

Groundwater at the CTP was classified by EPA in the OU1 ROD as “Potentially Usable Quality;” and groundwater adjacent to the Eagle River was classified by EPA in the OU1 ROD as “Protection of Surface Water.” The cleanup levels for groundwater adjacent to the Eagle River (classified for protection of surface water) are equivalent to surface water standards.

The Eagle River is divided into segments, with each segment having a unique set of water quality standards (Figure 3).

Upstream of the Site:

• Segment 2 extends from the Eagle River’s source to the compressor house bridge at Belden. Segment 2 represents background water quality. Water quality standards for Segment 2 are statewide, hardness-dependent standards, protective of all species, referred to as “table value standards.”

Within the Site bounds:

• Segment 5a extends from the compressor house bridge at Belden downstream to a point immediately above the Highway 24 bridge near Tigiwon Road. Water quality standards for Segment 5a are hardness-based equations with rainbow trout as the most sensitive species.

• Segment 5b extends from a point immediately above the Highway 24 bridge near Tigiwon Road to a point immediately above the confluence with Martin Creek. Water quality standards for Segment 5b are seasonal. For the low flow (i.e. high metals) season, January 1 through April 30, the standards use rainbow trout as the most sensitive species. During the rest of the year, the applicable standards use sculpin as the most sensitive species. A small native fish, sculpin is sensitive to metals contamination.

• Segment 5c extends from a point immediately above the confluence with Martin Creek to the confluence with Gore Creek (located north of Minturn). Water quality standards for Segment 5c are more stringent than 5a or 5b and are based on sculpin as the most sensitive species, year-round.

These revised water quality standards took effect on January 1, 2009. Table 2 identifies the hardness-based equations for dissolved cadmium, copper and zinc for each of the applicable Eagle River segments.


2.6.2 Arsenic Effluent Limit

In March 2016, CDPHE released the Technical Impracticability Evaluation Report for Arsenic in Surface Water at the Eagle Mine Superfund Site Operable Unit 1 (CDPHE 2016), which can be found as Appendix A of this ROD Amendment. In an email dated April 26, 2016, the EPA confirmed the TI Evaluation Report for the Site met the requirements for a technical impracticability consultation. A statutory waiver under CERCLA § 121(d)(4) of the 0.02 µg/l arsenic standard for Segments 5a, 5b, 5c and 7b of the Eagle River (Figure 3) is necessary because it is technically impracticable to meet the 0.02 µg/l standard at the Site; background concentrations in the Eagle River exceed 0.02 µg/l; analytical methods cannot measure this low; and treatment technologies have not been developed to effectively remove arsenic consistently to meet levels below 0.02 µg/l.

If a new treatment plant were to apply for a permit to discharge into the Eagle River, a temporary modification for new discharges would apply and granted an effluent limit of 3 µg/l. While the Agencies understand that the water treatment plant is not a new discharge source, the fact that the Colorado Water Quality Control Commission has recognized this value as technologically achievable for arsenic was considered in the decision to select 3 µg/l as the alternate remedial goal (cleanup level). Based on a risk evaluation for the Site prepared by an EPA toxicologist assuming a risk scenario of consuming water and fish from the Eagle River without prior treatment, 3 µg/l equates to a 5 x10-5 excess lifetime cancer risk, which is within EPA’s acceptable risk range and is considered protective of human health (CDPHE and EPA 2017). The Agencies made a final determination the TI waiver applies for the 0.02 µg/l arsenic standard, and the 3 µg/l alternate remedial goal will be used to measure protectiveness of the remedy.


3.0 Rationale for Amended Remedy

This ROD Amendment addresses three topics for the Eagle Mine Site: 1) definitions and scope of the OUs; 2) adoption of the Site-specific arsenic remedial goal (end-of-pipe effluent limit) and modification to cleanup levels in surface water for cadmium, copper, and zinc with subsequent expansion of the current groundwater collection system to meet the new cleanup levels; and 3) ICs.

3.1 Operable Units Definitions

Since the 1993 ROD, OU1 has become primarily media-based, focusing on protecting surface water at the Site by reducing metals loading to the Eagle River. On-going remediation within OU1 includes active engineered remedial features designed to capture and treat mine waste in surface and groundwater. From a land use perspective, the original OU1 remedial activities achieved cleanup levels that were protective for trespasser and recreational use scenarios for the soil media. OU2 is geographically based to focus on evaluating potential human health risks in the historic town of Gilman. The newly-formed OU3 is media-based and focuses on protection of human health for residential use through reduction of exposures to surface soil. Geographically, OU1 and OU3 overlap except for the area of Belden, which is in OU1 only. The EPA will release a separate ROD for OU3.

Due to the recent formation of OU3, the OU definitions need revision. See Section 4.1 for further explanation of OU definition changes.

3.2 Cleanup Levels and Additional Water Capture and Treatment

Surface water criteria protective of the expected biological condition in the Eagle River were adopted by the Colorado Water Quality Control Commission in 2008 (Table 2). These criteria are identified as ARARs for the Site and replace the standards adopted in the 1993 ROD. This ROD Amendment is necessary to adopt the new criteria as ARARs and replace the existing standards for cadmium, copper and zinc identified in the 1993 ROD.

In 1993, when the ROD for OU1 was issued, arsenic was not detected in surface water samples, using laboratory techniques available at the time. As a result, the ROD for OU1 did not include an RAO for arsenic (CDPHE and EPA 2017). This ROD Amendment is necessary to adopt the alternate remedial goal (cleanup level) of 3 µg/l for the end-of-pipe effluent limit at the water treatment plant, which was established using standard Superfund risk-based methods as detailed in the Technical Impracticability Evaluation Report (CDPHE 2016) (Appendix A).

The addition of a French drain system or groundwater extraction wells to capture contaminated groundwater adjacent to the Eagle River in Belden and at the mouth of Rock Creek and subsequent treatment at the existing water treatment plant is necessary to attain the new surface water standards.

3.3 Institutional Controls

ICs involve the implementation of non-engineered controls to augment engineering measures for protection of human health and the environment and long-term management to ensure continued compliance with the requirements of this ROD and ARARs.

The 1993 ROD did not identify the need for protection of the remedial components for the long-term. Since 1993, the state of Colorado enacted the Environmental Covenants (EC) Statute providing an appropriate mechanism to implement ICs at this Site; therefore, this ROD Amendment is necessary to add the Environmental Covenants Statute as an ARAR for this ROD Amendment (Appendix B).


4.0 Description of Amended Remedy

The existing remedy as detailed and adopted in the 1993 ROD, including the water treatment plant, will continue operations to maintain a constant mine pool level and to treat water collected from the CTP groundwater extraction trenches. This ROD Amendment includes only an expansion of the existing remedies either completed or ongoing. Therefore, the description of the amended remedy will only include a discussion of the additions to and expansion of the current remedy.

4.1 Definitions of Operable Units

With this ROD Amendment, the Agencies are revising the OU definition of OU1 to avoid overlap with OU2 and OU3. OU1 is media based and focuses on protecting surface water at the Site by reducing metals loading to the Eagle River. OU1 includes active engineered remedial features designed to capture and treat mine waste in surface and groundwater. In Gilman, areas where remedial features have been constructed are part of OU1, while those areas that have no remedial features will still be part of OU2. OU3 will now encompass the soil media portion of the historical definition of OU1.

4.2 Adoption of New Cleanup Levels and Expansion of Water Capture and Treatment System

This ROD Amendment adopts: 1) the Colorado Discharge Permit System (CDPS) Regulations and the Colorado Effluent Limitations to establish the arsenic effluent standard for the water treatment plant (i.e., point source discharge); and 2) the Colorado Basic Standards and Methodologies for Surface Water and the Colorado Surface Water Quality Classifications and Numeric Standards for Upper Colorado River Basin, to establish the surface water quality standards of Table 2. Appendix B identifies the ARARs for this ROD Amendment.

Cleanup standards for arsenic, cadmium, copper, and zinc will be achieved through the collection of groundwater at Belden, at the base of Rock Creek, and from the Mill Level of the mine and conveyance of the water to the existing water treatment plant. The Rock Creek and Belden areas are illustrated on Figure 4 and the existing water treatment plant is presented on Figure 2. The collection methods may include a French drain system, extraction wells, or other methods developed and approved by the Agencies during Remedial Design. This collection system would be designed to capture contaminated groundwater that enters the Eagle River during spring.

For cost estimation purposes, a trench is assumed to be the system used for groundwater collection. The new collection trench would be constructed with 700 feet of perforated pipe set at the static (fall/winter) groundwater level, some 15 to 18 feet below ground surface , and designed to intercept the spring pulse of groundwater that occurs each year in Belden. The trench would be constructed parallel or beneath the railroad along a line extending from the base of the Tramway Drainage downstream the full length of the Loading Dock. As a part of trench construction, excavated track ballast, waste rock and gravel will be hauled to a solid waste facility, possibly the CTP. Excavated trash and debris (rails, ties, pipes, etc.) will be taken to the municipal landfill. Trench backfill above the high groundwater level will consist of crushed limestone and dolomite waste rock from WRP-11 in Rock Creek. The trench will be lined with a polyethylene liner on the river side to establish an impermeable barrier. A valve will be incorporated at the discharge end to allow shut-off in May, when dissolved metals concentrations in the Eagle River are typically below the water quality standards. The discharge would be conveyed via the existing gravity collection system pipeline to the water treatment plant for treatment (CBS 2013).


A non-perforated connecting pipeline would extend 1,100 feet downstream from the end of the perforated section to near Rock Creek where it would enter the existing pipeline and gravity drain to the water treatment plant for treatment. Water that collects in the existing Copper Tipple Trench would gravity drain to the new, lower trench via the historic tunnel (CBS 2013). A diagram of the collection trench location is presented in Figure 5.

Water that accumulates on the Mill Level of the mine would be pumped periodically to the new collection trench to minimize recharge from this source.

Existing well EDS-3 at the base of Rock Creek would be used to extract 10 gallons per minute of groundwater continuously during March and April.

The selected amended remedy system may be designed to operate off-the-grid. Power will be needed in Belden, either from hydroelectric, solar photovoltaics, or a conventional land-line brought in from an adjacent community, to pump existing wells or new wells (CBS 2013).

As mentioned previously, the actual design of the groundwater extraction system will be finalized during remedial design and may include extraction wells and/or the trench described above.

4.3 Institutional Controls

Appendix B identifies the ARARs for this ROD Amendment, including the Colorado EC Statute which provides for long-term protection of remedial features. The Agencies will obtain ECs or RNs restricting activities that may damage or interfere with the proper operation or maintenance of any engineered component of the new OU1 remedy on the Property including: the mine water transport pipeline, trestle, surge ponds, water treatment plant, access road, collection systems, vaults, manholes, monitor wells, sumps, and underground groundwater collection systems.

4.4 Remedial Action Objectives

RAOs provide a general description of what a cleanup will accomplish and include the COCs identified for the Site, exposure routes/receptors and acceptable levels of COCs for each identified exposure route.

The RAOs pertinent to water set forth in the 1993 ROD were as follows:

• Improve the quality of water in the Eagle River to support Class 1 aquatic life use; and

• Control or eliminate human ingestion of contaminated groundwater.

The 1993 RAOs as stated above have not changed; however, three additional RAOs are being added through this ROD Amendment.

For this ROD Amendment, the acceptable level for cadmium, copper, and zinc is the hardness-based water quality standard for Segment 5 of the Eagle River (described in Table 2). Segment 5 of the Eagle River encompasses those segments of the river within the Site and the segments currently not attaining standards due to releases from the Site. Therefore, a new RAO is:

• For Segment 5 of the Eagle River, prevent the exposure of biota (fish and aquatic organisms) in the Eagle River to cadmium, copper and zinc concentrations that exceed water quality standards.


For arsenic, the new RAO is:

• For Segment 5 of the Eagle River, prevent the exposure of humans to arsenic from the Eagle River in excess of the alternate remedial goal.

The new RAO for long-term protection of the remedy is:

• Ensure the long-term protectiveness of the remedy through proper management and preservation of the remedial components.


5.0 Evaluation of Amended Remedial Action

The NCP requires that remedial alternatives be evaluated against nine criteria. The amended remedy for water capture and treatment is compared to the nine criteria in the following sections. The administrative measures of OU definitions and ICs implementation (already evaluated in the 1993 ROD) are not required to undergo evaluation against the nine criteria for this ROD Amendment.

The nine criteria are divided into three categories: threshold, balancing, and modifying. Threshold criteria include: 1) overall protection and 2) compliance with ARARs. An alternative must meet these criteria to be eligible for selection as a remedial action. Balancing criteria are: 3) long-term effectiveness and permanence; 4) reduction of toxicity, mobility or volume through treatment; 5) short-term effectiveness; 6) implementability; and 7) cost. The five balancing criteria weigh the tradeoffs between alternatives, allowing low ratings on one balancing criterion to be compensated by a high rating on another. Modifying criteria are 8) EPA and state acceptance and 9) community acceptance. Community acceptance is considered following a public comment period. The EPA and CDPHE are required to review and provide responses to public comments before the ROD Amendment can be finalized. The Responsiveness Summary can be found in Section 9.0 of this ROD Amendment.

5.1 Overall Protection of Human Health and the Environment

The 1993 remedy is no longer protective of human health and the environment. Remediation at the Site has been ongoing since 1988; however, current water quality standards for the Eagle River have not yet been met. Surface water criteria protective of the expected biological condition in the Eagle River were adopted by the Colorado Water Quality Control Commission in 2008. These criteria are identified as ARARs for the Site and replace the standards adopted in the 1993 ROD. After completion of the remediation required by the OU1 ROD (EPA 1993), cadmium, copper and zinc concentrations in the Eagle River still exceeded levels deemed protective of aquatic life in the months of March and April. During annual snowmelt periods in March and April, higher dissolved metals concentrations have been and continue to be observed in the Eagle River. Subsequently, years with higher snowpack have increased metals contamination in the Eagle River. By May of each year, warm temperatures generate snowmelt in the upper Eagle River basin and a large increase in stream flow occurs, with peak flows typically occurring in late May or early June. Increased stream flow results in lower metals concentrations. For the remainder of the year, dissolved metals concentrations in the Eagle River are typically below the water quality standards (CDHPE and EPA 2017). Until the standards are attained year-round, there is an unacceptable risk to aquatic life.

This amended remedy provides protection to human health and the environment through the collection and treatment of a primary metals loading source (localized groundwater sources) and the implementation of ICs. Arsenic concentrations in the Eagle River should decline as a result of the actions described herein because the additional water sent to the water treatment plant is one of the main sources of arsenic affecting the river. More arsenic will be removed at the water treatment plant than under the current remedy and the plant will be required to meet the effluent limit set at the alternate remedial goal (cleanup level) for arsenic (3 µg/l). Currently, the water treatment plant does not have an effluent limit for arsenic. As discussed extensively in the FFS (CBS 2013), the selected amended remedy is expected to reduce loading of zinc, copper and cadmium to the Eagle River, depending on the winter snowpack. Most notably is the removal of an estimated 46 to 92 pounds of zinc per day. ICs, specifically EC/RNs, will ensure the long-term protection of remedial components and therefore protection of the remedy.


5.2 Compliance with Applicable or Relevant and Appropriate Requirements

The 1993 remedy does not meet current ARARs. CDPHE and the EPA have identified current ARARs for surface and groundwater at the Site, found in Appendix B. These ARARs will update those presented in the 1993 ROD. Unless identified in Appendix B of this ROD Amendment, the ARARs presented in the 1993 ROD are still in effect.

A statutory waiver under CERCLA § 121(d)(4) of the 0.02 µg/l arsenic standard for Segments 5a, 5b, 5c and 7b of the Eagle River (Figure 3) is necessary because it is technically impracticable to meet the 0.02 µg/l standard at the Eagle Mine Site; background concentrations in the Eagle River exceed 0.02 µg/l; analytical methods cannot measure this low; and treatment technologies have not been developed to effectively remove arsenic consistently to meet levels below 0.02 µg/l.

The amended remedy provides a high likelihood of attaining current water quality standards. Analysis in the FFS (CBS 2013) indicates that water quality standards will be met during most years; however, because this remedy cannot address added load from upstream (non Site-related) sources, there may be times when the upstream sources contribute to exceedances of the water quality standards. The addition of ECs to the ARARs will support the long-term protection of remedial components.

5.3 Long-Term Effectiveness and Permanence

The 1993 remedy is no longer effective for the long-term and does not provide permanence in meeting new water quality standards. The amended remedy provides a high degree of long-term effectiveness and permanence because groundwater collection and treatment is effective. Groundwater collection and treatment at the CTP has been effective in reducing metals loading to Segment 5b of the Eagle River. Long-term operations and maintenance will be needed for the groundwater collection system, which is the only new remedial component to be added to the existing remedy. All other remedial components (conveyance pipeline and water treatment plant) already require long-term operations and maintenance. This remedy also includes the use of ICs to provide long-term protection of the remedy. ICs (i.e., EC/RN) remain in place and enforceable even if the property ownership changes.

5.4 Reduction of Toxicity, Mobility, or Volume through Treatment

The 1993 remedy provides only partial reduction in toxicity, mobility and volume because not all sources of contamination to the Eagle River are captured for treatment. The amended remedy results in the maximum reduction of toxicity, mobility and volume of contaminants through treatment because the expanded groundwater collection system captures additional sources of contamination to the Eagle River and treats the water before discharge. In addition, the amended remedy identifies an effluent standard for arsenic, which was not included in the 1993 remedy.

5.5 Short-Term Effectiveness

The 1993 remedy may be considered effective in the short-term as the components are already in place. The amended remedy is easy to construct and implement and immediately upon completion, will decrease contaminant loading to the Eagle River. The amended remedy is highly effective short-term. The amended remedy does present potential risks to construction workers through possible inhalation of dust, ingestion of metals, rock falls, avalanches, and heavy equipment operation.

The original remedy did not meet RAOs set forth in the 1993 ROD and will not meet the RAOs added through this ROD Amendment. The amended remedy will meet the new RAOs upon construction completion (i.e., discharge of additional water through treatment plant) and implementation of the ICs.


Construction of the water collection system is estimated to take 3 to 5 months. ICs may be implemented within a few months.

5.6 Implementability

The 1993 remedy was easily implementable as the components have been constructed. The amended remedy is easy to implement because it relies on proven construction techniques already used at the Site and conventional water treatment technology at the existing water treatment plant.

5.7 Cost

Table F-2 of the FFS (CBS 2013) presented the detailed cost estimate and present worth analysis for all of the alternatives under consideration in the report. The costs were based on 2013 prices and the present worth analysis was for 30 years. The tables also included costs for the continuing remedial actions of the 1993 ROD.

The 2017 FFS Addendum (CBS 2017) also included detailed cost estimates and present worth analyses for the alternatives. The costs for the selected remedy (Alternative 2A) increased slightly from the 2013 estimate to account for inflation and minor refinement to the conceptual design of the remedial components.

The costs presented in the Proposed Plan (CDHPE and EPA 2017) reflect the 2017 capital cost adjustments from the FFS Amendment, present operations and maintenance costs for only the expanded portion of the remedial action separately and include a present worth analysis for 50 years1.

For this ROD Amendment, Appendix C includes the final cost estimate for the selected extended remedy. In summary, capital costs are estimated to be $389,789, total annual operations and maintenance costs of $14,460, resulting in a 50-year present worth (using a 7% discount rate) of $604,000.

5.8 Regulatory Acceptance

The EPA supports the amended remedy.

5.9 Community Acceptance

In general, the comments received during the public comment period on the Proposed Plan expressed support of the preferred alternative of Alternative 2A and several commenters requested timely implementation of the preferred alternative. However, several commenters expressed concern about the estimated load reduction necessary to attain standards, as reported in the FFS and suggested that a contingency remedy be adopted that would require the removal of waste rock in the event that the preferred alternative fails to achieve the cleanup goals. The Agencies will require re-evaluation of the enhanced remedy and implementation of additional actions if goals are not achieved, but it is premature at this time to suggest what additional actions may solve a future problem. In addition, the estimated load reduction will be revised during RD/RA and the groundwater extraction system design will be based on hydrogeology. The Responsiveness Summary for comments received during the public comment period can be found in Section 9.0 of this ROD Amendment.

1 The EPA traditionally applies a 50-year life-span to remedial actions that involve water treatment.


6.0 Support Agency Comments

Through coordinated efforts and continuous communication, CDPHE worked cooperatively with the EPA to resolve any issues or comments during the ROD Amendment process. CDPHE has satisfactorily resolved any EPA comment and the EPA fully supports this ROD Amendment.


7.0 Statutory Determinations/Declarations

The amended remedy presented in this ROD Amendment for OU1 satisfies CERCLA Section 121 requirements as it is protective of human health and the environment, complies with federal and state requirements that are applicable or relevant and appropriate to the remedial action, is cost effective and uses permanent solutions and alternative treatment technologies to the maximum extent possible. The amended remedy also satisfies the statutory preference for treatment as a principal element of the remedy (i.e., reduces the toxicity, mobility, or volume of hazardous substances, pollutants, or contaminants as a principal element through treatment). Because this amended remedy results in hazardous substances, pollutants, or contaminants remaining onsite above levels that allow for unlimited use and unrestricted exposure, a statutory review will be conducted within 5 years after initiation of remedial action to ensure that the remedy is, or will be, protective of human health and the environment.


8.0 Public Participation

Under CERCLA Section 117(c), 42 U.S.C. § 9617(c), and the NCP, 40 C.F.R. § 300.435(c)(2)(ii), the EPA must publish proposed changes to existing remedies that fundamentally alter the basic features of the selected remedy with respect to scope, performance, or cost and provide the public an opportunity for comment on the proposed changes. The proposed changes for this Site fundamentally alter the basic features of the existing remedy prompting the issuance of this ROD Amendment. The EPA and CDPHE complied with CERCLA by publishing the proposed plan on June 28, 2017, and accepting public comments from the publishing date until September 10, 2017. During the 75 day public comment period, the Agencies held a public meeting to discuss the proposed change in the remedy on July 25, 2017 at 5:30pm at the Colorado Mountain College, 150 Miller Ranch Road, Edwards, Colorado.

The following text includes public participation activities conducted by CDPHE and the EPA specifically for this ROD Amendment. A list of public participation activities prompted by the adoption of new water quality standards in 2008 leading up to this ROD Amendment can be found in Table 3.

CDPHE and the EPA issued a Proposed Plan on June 28, 2017, and invited public comment on possible changes to the remedy in the 1993 ROD.

The Agencies announced the proposed amendment to the 1993 ROD in the Vail Daily on June 28, 2017, indicating the availability of the Proposed Plan on the EPA website and at the Administrative Record repositories.

The proposed amendment to the ROD is available at the EPA, Region 8, Records Center, 1595 Wynkoop Street, Denver, Colorado 80202 and the CDPHE, Environment Records Center, 4300 Cherry Creek Drive South, Denver, Colorado 80246. It is also available and can be viewed at https://www.colorado.gov/pacific/cdphe/eagle-mine or https://www.epa.gov/superfund/eagle-mine.

The original public comment period was from June 28, 2017 to August 11, 2017 (45 days). The Eagle River Watershed Council (ERWC) requested a 30-day extension. As a result, the public comment period was extended through September 10, 2017. CDPHE and the EPA sent letter responses to ERWC announcing the extension (CDPHE for OU1 and EPA for OU3). A public notice of the extension(s) was published in the Vail Daily on July 20, 2017.

CDPHE and the EPA hosted a public meeting at the Colorado Mountain College, 150 Miller Ranch Road, Edwards, Colorado, on Tuesday, July 25, 2017 from 5:30 to 8:30 p.m.

A complete transcript of the public meeting, including all comments received during the public meeting, is available at the Administrative Record repositories.

The Agencies received comments from 24 separate entities/individuals on the proposed amendment during the public comment period. A Responsiveness Summary, which includes each comment, criticism and/or new relevant information submitted, followed by a response to each as prepared by the Agencies, is included as Section 9.0 of this ROD Amendment.

The Agencies will publish a notice of the availability of the amended ROD in the Vail Daily.

This ROD Amendment is a part of the Administrative Record for the Eagle Mine Site and is available at each information repository for public review prior to the commencement of the remedial action described herein.


9.0 Responsiveness Summary

In general, all comments submitted during the public comment period were in general support of Alternative 2A as the “minimum” selected remedy. Most commenters suggested additional actions that could be taken to further reduce the loading and ensure water quality standards are met in the Eagle River.

1. Support of the Selected Remedy as Proposed

CDPHE and the EPA received 3 comments supporting the Selected Remedy of expanded groundwater collection and treatment as presented in the Proposed Plan.

Agency Response:

No response necessary.

2. Compliance with Water Quality Standards/Inability t o Remove Adequate Metals

CDPHE and the EPA received 11 comments regarding the quality of the drinking water in Minturn and the quality of the surface water in the Eagle River during high run-off periods (April and May). Specifically, the concern is the perceived inability of the selected remedy (capture and treat groundwater) to remove adequate amounts of zinc and other metals to comply with surface water standards during those spring snow melt months.

Multiple commenters suggested the Proposed Plan calling for removing 58 lbs. per day will not meet compliance in peak run-off months, if at all, with the established zinc standard. A commenter suggested that Water District consultants have indicated that zinc loading at the Mine river segment calls for removal of 75-109 lbs. per day. Another commenter suggested the FFS and Proposed Plan significantly underestimate the loading reductions needed to meet the standard for dissolved zinc in segment 5a.

One commenter suggested the OU1 ROD Amendment should include contingencies for augmentation of the initial design and implementation of Alternative 2A through additional or modified diversion, collection and extraction structures. The commenter suggested that including this contingency in the “Record” for OU1 would provide the best, most cost-effective protection of the Eagle River without the need to re-open these proceedings to further amend the Record or Administrative Order on Consent.

While supporting the selected remedy for OU1, one commenter noted investigations completed at the Site over the past 25 years have identified sources of metal loading to the Eagle River. There are documented sources of metal loading upstream of Belden, which have been investigated in recent years. The area has been named the Eagle River Abandoned Mine Sites. There appears to be limited information to accurately estimate the loading from the upstream metals loading sources to the river. Table 4 of the Proposed Plan does not estimate the zinc load estimates to the Eagle River from the Eagle River Abandoned Mine Sites, which would be useful to determine if remedial actions upstream of Belden would also reduce loading to the river. The commenter also suggested the Spring Zinc Loading Distribution in the Eagle River graph presented in the Proposed Plan indicates that the zinc loading in Segment 5a has been trending down since the peak in 2006, even in the high runoff years and that an updated graph (through 2017) would more accurately represent the loading and decreases that have occurred in Segment 5a.

Another commenter offered it is not appropriate to: 1) assume that the upstream load is sufficient to hamper attainment of the relaxed water quality standards that have been applied to segments 5a, 5b and 5c as was suggested in the Proposed Plan; 2) draw conclusions about groundwater loading from one pump-testing event that was not representative of periods when groundwater conditions drive exceedances of surface water quality standards; or 3) further reduce the estimated groundwater loading at Belden based upon conditions observed at the east groundwater extraction trench at the


CTP, without providing any information or analysis indicating that geology and groundwater conditions at these two locations are similar.

Agency Response:

Drinking water in Minturn is not impacted by the Site. Minturn’s water system is located upstream from the Site. The drinking water system is regulated under the Safe Drinking Water Act, which requires routine monitoring for numerous health-based water quality parameters.

Based on data and analysis contained in the FFS (CBS 2013) the estimated average amount of zinc load reduction needed to meet the zinc water quality standard is 58 lbs/day. This estimate has several caveats including an explanation of the potential uncertainties inherent in such estimates. While the Agencies could have continued to study the loading for many years to better bracket the load reduction necessary to meet the water quality standards, the Agencies chose to move forward with the data available at the time. Most importantly, the 58 lbs/day figure is not a design criterion for the groundwater extraction system. Hydrogeologic information for the groundwater system will be used to design the extraction system, including both physical and chemical data from groundwater monitoring wells and data from conductivity surveys. Conductivity surveys indicate where contaminated groundwater enters the river (through groundwater discharge) and this information will be used to properly locate an extraction trench and/or extraction wells. In addition, during the Remedial Design phase, the load reduction calculations will be updated using more recent data, as suggested by the Eagle River Water Users in their comments. The design of the system will not be based solely on an estimate of necessary load reduction.

With regard to the comment that there appears to be limited information to accurately estimate the loading from the upstream metals loading sources to the river, the loading in segment 2A is presented in the FFS, Table 3 but this information was not repeated in the Proposed Plan. Zinc load in Segment 2A in March and April ranged from 3.1 lbs/day to 53.8 lbs/day.

Similarly, a commenter was concerned about the accuracy of the load removal estimates based on what is characterized by the commenter as a limited data set derived during a drought year. While there was only one aquifer pumping test conducted and it was conducted during one of the drier years, the sustainable pumping rate of the wells is more dependent upon the aquifer materials than on the climate conditions. Again, additional study may have provided a more robust data set, but this data is not critical to determine that groundwater is the primary source that must be captured to most effectively reduce metals concentrations in the Eagle River. The groundwater extraction system will remove the groundwater regardless of concentration. So if the concentrations have been underestimated (as indicated in the comments) the system may actually perform better than expected. If on the other hand, concentrations are lower than predicted, the system will still operate and extract the groundwater that enters the system.

Although this ROD Amendment does not contain specific contingencies to require the removal of waste rock should the new groundwater extraction system fail to attain water quality standards, it does require an evaluation every five years; including potential sources and causes for non-attainment of ARARs (see Section 7.0). Potential additional activities to address any residual sources could include enhancement of the groundwater extraction system (for example, extension of an extraction trench or installation of additional extraction wells) or additional waste removal. It is premature to suggest at this time that the new remedy will fail or to suggest what will be the best route to improve the remedy in the future.

Because CBS has not been held responsible for metals load that occurs in Segment 2, upstream of the Site, some consideration must be given to potential exceedances of the standards if the exceedance can be proven to be related to a release of contaminants from upstream. CBS will continue to monitor the quality of the water entering the Site from upstream and if the remediation systems are


functioning as designed and data indicate that non-attainment was caused by upstream sources, consideration may be given for such events.

3. Removal of Waste Rock Piles

CDPHE and the EPA received 14 comments regarding the need to remove the WRPs and tailings from the watershed. One commenter suggested the Proposed Plan is also “high maintenance” requiring regular inspection and servicing; requesting longer term solutions such as physical removal of WRPs and tailings as preferable to the on-going expense of maintenance of such a fragile system, vulnerable to periodic spills and the uncertainties of corporate ownership. Multiple commenters noted cleanup actions that focus on removing sources of contamination have been proven as effective long-term remedial strategies at other Superfund sites.

A commenter suggested the OU1 ROD Amendment should include a contingency that in the event of exceedances of applicable water quality standards for zinc, cadmium, copper, lead or silver, that occur more frequently than once every three years on average following implementation of Alternative 2A, the implementation of Alternative 3A would be triggered. The commenter suggested that including this contingency in the “Record” for OU1 would provide the best, most cost-effective protection of the Eagle River without the need to re-open these proceedings to further amend the Record or Administrative Order on Consent.

Another commenter cited a 2005 Hydrosphere study which reported contamination of groundwater and surface water from waste rock is the most likely primary source driving peak zinc concentrations that occur during early spring runoff.

Agency Response:

Several commenters suggested that if waste rock were removed in lieu of groundwater extraction, that high maintenance components of the remedy would no longer be necessary. Unfortunately, this is not the case. The primary focus of the existing remedy is to control water levels in the mine pool, which under the current remedy design, relies on the pipeline and collection features. Disposal of waste rock does not remove the need for the high maintenance remedy components at the Site.

It is important to note that some of the issues related to waste rock described in the 2005 Hydrosphere Report (Hydrosphere 2005) have been mitigated in the interim. For example, in 2004, the lower WRP-8 collection system was constructed. This initial system was prone to overflow, and the basin was reconstructed in 2009. Since the implementation of water collection structures at WRP-8, metals concentrations in Rock Creek have declined. With regard to the “Project No. 2” suggestions in the Hydrosphere memo, the EPA Removal Program constructed a concrete block wall in 2008. This effectively mitigated the concern expressed in the 2005 memo regarding waste rock in the Belden Mill Site area. In addition, WRP-14 was removed by CBS in 2006. Unfortunately, the removal of WRP-14 did not result in any noticeable reduction in zinc loading in the Belden reach of the Eagle River, even though this was identified as an acid-generating pile and had slope and aspect that made it ideal for groundwater infiltration. For these reasons and those already discussed in the FFS, the Agencies do not believe that waste rock removal will significantly impact metals loading in the Eagle River in March and April. As stated in Section 7.0, because this amended remedy results in hazardous substances, pollutants, or contaminants remaining on-Site above levels that allow for unlimited use and unrestricted exposure, a statutory review will be conducted within 5 years after initiation of remedial action to ensure that the remedy is, or will be, protective of human health and the environment. These Five-Year Reviews have been on-going at this Site and will continue until the Site is remediated to unlimited use and unrestricted exposure. If any of these evaluations indicate that expansion or enhancement of the new collection system is not attaining ARARs or is not protective of human health and the environment, then the removal of acid-generating waste rock may be reconsidered.


4. Long-Term Sustainability of the Inspection/Maintenance Protocols for Infrastructure, Capacity and Ability at the Current WTP

CDPHE and the EPA received 5 comments expressing concern about the long-term sustainability of the infrastructure inspection and maintenance, capacity at the current water treatment plant and ability of the current water treatment plant to handle this additional flow.

One commenter is concerned about the long-term sustainability of the collect and treat method relied upon in the plans, as it requires rigorous inspection and maintenance protocols for the infrastructure used to collect and transport the contaminated water for treatment. Such protocols, which would need to continue indefinitely, are especially critical in light of past spills and incidents at the Site, some of which have occurred as a result of deferred maintenance.

Another commenter questioned whether the existing conveyance system for influent to the existing water treatment plant is of the condition and capacity to accommodate the additional flows anticipated from the implementation of Alternative 2A. It is impossible with existing information to determine with any level of certainty the existing infrastructure is capable of receiving and conveying the anticipated flows from groundwater collected at Belden and Rock Creek.

Multiple commenters expressed concerns about the ability of CBS to continue the extensive ongoing operations, maintenance, and replacement of collection and treatment facilities indefinitely into the future. They went on to suggest that if the Proposed Plans are modified to include additional removal actions, it would help assure the sustainability of the cleanup and could eventually reduce ongoing operation and maintenance costs and if such removal actions are not included in the Proposed Plan, CDPHE and the EPA should consider bonding or other measures to assure long-term sustainability.

Agency Response:

During Remedial Design, CBS will be required to demonstrate that the existing infrastructure at the Site is adequate to deal with the new flows that will be generated by the new collection system. This requirement will apply to both the pipeline and the water treatment plant. If either remedy component has insufficient capacity, upgrades will be required.

CBS will need to ensure remedy components are monitored and maintained pursuant to a new Inspection and Maintenance Plan. CBS is also required to continue providing financial assurance, which terms will be updated to incorporate the costs associated with operating additional remedy components. The agencies and CBS will address these requirements while developing a long-term operation and maintenance agreement.

5. Gage Station Operation and Maintenance Costs

CDPHE and the EPA received a comment specifically requesting CBS assume sole financial responsibility of the escalating costs for operation and maintenance for the USGS stream gage at monitoring location E-12A.

Agency Response:

The Agencies are aware of the cost-sharing agreement between Eagle County, CBS and the U.S. Geological Survey to fund the stream gage at Tigiwon Road. Continued funding for the gage is a high priority for the Agencies and we will continue to require CBS to fund the gage.

6. Include Alternative 2C

One commenter recommended that if Alternative 2A falls short in meeting goals, Alternative 2C be kept on the table with relatively quick implementation.


Agency Response:

Alternatives 2C and 2A would be constructed in essentially the same location. If a trench/French drain system is recommended for the groundwater extraction during Remedial Design, then it may be possible to later convert the trench to an iron-rich material (IRM) treatment wall. However, if during Remedial Design, the final design is for extraction wells, then it would be more difficult to implement an IRM trench as a contingency. As stated in Section 7.0, because this amended remedy results in hazardous substances, pollutants, or contaminants remaining on-Site above levels that allow for unlimited use and unrestricted exposure, a statutory review will be conducted within 5 years after initiation of remedial action to ensure that the remedy is, or will be, protective of human health and the environment. These Five-Year Reviews have been on-going at this Site and will continue until the Site is remediated to unlimited use and unrestricted exposure. If any of these evaluations indicate that expansion or enhancement of the new collection system is not attaining ARARs or is not protective of human health and the environment, then the implementation of Alternative 2C may be reconsidered.

7. Recreational/Educational Use

One commenter observed that “Gilman is located on a Scenic Highway, between Minturn and Redcliff. It overlooks a scenic canyon, and has a large flat area. The pollution is located below in the 500 miles of tunnels.” The commenter suggested that the ghost town is “just plain cool,” but some buildings should be knocked down. The commenter further suggested that a visitor center/research center/learning center would be the center piece and that parking and camping are needed on that stretch of highway. Representative Polis is recommending camp Hale get some protection.

The commenter remarked that the Site could be an incredible teaching tool. People/children could learn the effects of mining. Walking Mountains could be a large contributor. Real-time video and censors could be placed around the mine. Parking and camping fees could contribute to the research/cleanup.

Agency Response:

This ROD Amendment does not address the Gilman area. Gilman is within OU2 and no further actions are being conducted in OU2 at this time. Because no cleanup has occurred in Gilman, a change in land use to support educational or active recreation uses would require a human health risk assessment prior to allowing such a change in land use. In addition, Gilman is private property, so land use decisions will be made by the local governments, not the Agencies. If the local government determines that the best use of the land in Gilman is for recreational or educational purposes and the land owner agrees, CDPHE and the EPA will work with the land owner to determine what additional cleanup would be needed to allow the new land use.

8. Applicable Comments from the Draft Discharge Permit

One commenter requested their comments on the Draft CDPS Discharge Permit # CO-0042480 for the Eagle Mine Water Treatment Plant as part of OU1 of the Eagle Mine Superfund Site provided to the Water Quality Control Division be considered as part of the OU1 Proposed Plan.

Agency Response:

CBS provided comments to the State on the draft CDPS permit suggesting that paired hardness be used to calculate effluent limits instead of the method that was used in the draft permit, based on average hardness calculated seasonally. Because hardness is collected for each water quality sample, it is more accurate to determine compliance using paired data. This comment is similar to the comment received from the Eagle River Water Users regarding the calculation methods for the amount of zinc loading necessary to meet the standards. The commenter presented an updated table demonstrating how to determine compliance with the chronic standards using paired data. The Agencies intend to use the hardness data to calculate the surface water standards for each sampling


event, for each parameter, at each location. Compliance with the standards will follow Water Quality Control Commission Regulation 31, requiring that the concentration associated with the 85th percentile of the data must be at or below the standard and that exceedances of the standard cannot occur more frequently than once every three years on the average.

9. Support of Institutional Controls

A commenter supported the inclusion of ICs to ensure the OU1 Proposed Plan will achieve ARARs and protect human health and the environment for the long-term, including enforcing long-term inspection and maintenance protocols which are necessary for successful remediation using the proposed collect and treat approach.

Agency Response:

ICs can and will be used to protect the existing remedy from future changes in land use, tampering or damage. However, ICs cannot ensure ARARs compliance or be used to enforce long-term inspection and maintenance protocols. The long-term enforcement and compliance activities will be governed by a Consent Decree, as the Consent Decree is a more powerful legal mechanism to require compliance with ARARs.


10.0 References

CBS Operations, Inc. (CBS). 2013. Focused Feasibility Study, Eagle Mine Site, Minturn, Colorado. Prepared by NewFields. July 26.

CBS. 2017. Focused Feasibility Study Addendum, Eagle Mine Site, prepared by NewFields. February.

Colorado Department of Public Health and Environment (CDPHE). 2016. Technical Impracticability Evaluation Report, Arsenic in Surface Water at the Eagle Mine Superfund Site, Operable Unit 1. March.

CDPHE and U.S. Environmental Protection Agency (EPA). 2017. Eagle Mine Superfund Site Proposed Plan to Amend the Operable Unit 1 Record of Decision. June.

Hydrosphere Resource Consultants, Inc. (Hydrosphere). 2005. Eagle River Metals Loading Sources and Potential Remediation Measures Report submitted to Steven J. Bushong, Porzak Browning & Bushong, LLP. November.

EPA. 1993. Superfund Record of Decision: Eagle Mine Site, Colorado. EPA/ROD/R08-93/068. March 29.

EPA. 2013. Fourth Five-Year Review Report for Eagle Mine Superfund Site, EPA ID COD081961518. September.

TABLES

OU1 ROD Amendment Page 1 of 14 September 2017

TABLE 1

COMPREHENSIVE SITE-WIDE CHRONOLOGY OU1 ROD AMENDMENT - Eagle Mine Superfund Site

Event Type Operable

Unit Action

Regulatory/ Oversight Authority

Date Event Description

General Milestone Site-Wide Site Inception N/A Late 1870s Mineral deposits including lead, zinc and precious metals discovered on Battle Mountain.

General Milestone Site-Wide Site Inception N/A 1879 Mining began in the area and the town of Gilman was founded.

General Milestone Site-Wide Site Establishment N/A 1880 Smelter completed in the town of Red Cliff.

General Milestone Site-Wide Site Establishment N/A 1905-1906 Mills constructed in Gilman and Belden. Extraction of zinc deposits began using roasting and magnetic separation to process ore.

General Milestone Site-Wide Site Establishment N/A 1912-1916 Individual mining claims consolidated into what is now known as the Eagle Mine.

General Milestone Site-Wide Site Establishment N/A 1914 USFS issued permits for tailings disposal from roaster/mill to an “8-acre area above Eagle River.” Permit reissued in 1917.

General Milestone Site-Wide Mining Operations N/A April 1919 Roaster units dismantled to construct underground mill in Eagle River valley at Belden.

General Milestone Site-Wide Site Construction N/A 1928 Pipeline constructed to transport mine water and tailings slurry.

General Milestone Site-Wide Mining Operations N/A 1929 Underground mill constructed using conventional froth-flotation techniques to generate lead-zinc concentrate.

General Milestone Site-Wide Mining Operations N/A April 1929-1946

Pipeline transported tailings to the OTP. Pipeline extended to a location near to Cross Creek using an elevated wooden trestle to cross Rex Flats and form New Tailings Pile (now called CTP). OTP abandoned and newly established CTP opened to alleviate almost full OTP in 1946.

General Milestone Site-Wide Sewage Treatment Plant Constructed

1950 Sewage Treatment Plant constructed to treat chlorinated effluent to tailings at CTP.

General Milestone Site-Wide Mining Operations N/A 1960s About 400,000 tons of tailings from OTP reprocessed for sulfur and used in the manufacturing of sulfuric acid.

General Milestone Site-Wide Mining Operations Ended

N/A 1977 Eagle Mine closed under operation of Gulf + Western, Inc. (buyer of New Jersey Zinc Company).

General Milestone Site-Wide Mining Operations N/A 1977-1981 Intermittent mining continued.


TABLE 1


Event Type Operable

Unit Action



General Milestone Site-Wide Mining Operations N/A 1981

Gulf + Western, Inc. personnel drained fluid containing PCBs out of three transformers located in an abandoned portion of mine to prevent contamination.

General Milestone Site-Wide Mining Operations N/A November 1981-September 1983

Mine inactive with the exception of the operation of WTP.

Contamination Release

Site-Wide Pond Collapse N/A October 1982 Riser pipe in tailings pond collapsed resulting in a discharge of a large volume of tailings material and water from CTP to Maloit Park and Cross Creek.

Enforcement Site-Wide NRD Claim State of Colorado 1983 State of Colorado filed NRD lawsuit against Gulf + Western, Inc. under Superfund statute.

General Milestone Site-Wide Property Transfer N/A September 1, 1983 Property purchased by Glenn Miller, who in turn sold 1,400 acres of the 6,500 acre parcel to Battle Mountain Corporation.

General Milestone Site-Wide Mining Operations Ended

N/A 1984 Mining operations abandoned at Eagle Mine in 1984.

Emergency Response

Site-Wide Emergency Removal N/A June 15, 1984

EPA conducted an emergency removal of transformers containing PCBs from within mine workings to prevent further PCB contamination, threatened by rising water levels in mine after dewatering pumps were turned off.

Investigation Site-Wide Remedial Investigation Feasibility Study

State of Colorado November 1, 1984- December 20, 1985

RI/FS performed for CDPHE by Engineering Science.

Response Action Site-Wide Remedial Action State of Colorado 1986-1990

Concrete adit bulkheads constructed to prevent discharge of mine water and submerge sulfide ore bodies to reduce amount of oxygen driving acid rock drainage reaction.

Enforcement Site-Wide MOA State of Colorado March 26, 1986 EPA and state of Colorado entered into a MOA designating the state as the lead agency for the Site’s clean up.

General Milestone Site-Wide Record of Decision State of Colorado April 4, 1986 State of Colorado issued ROD for Site based on investigations under 1985 RI and FS.

Enforcement Site-Wide Consent Decree State of Colorado April 23, 1986 State of Colorado settled with PRP; CD/RAP finalized.


TABLE 1


Event Type Operable

Unit Action



CERCLA Milestone Site-Wide NPL Listing EPA June 10, 1986 Eagle Mine Site placed on NPL under CERCLA (EPA Site Identification No. COD081961518).

Risk Assessment Site-Wide Endangerment Assessment

State of Colorado May 20, 1988

State of Colorado completed Endangerment Assessment, listing the following metals present in waste at the Site: antimony, arsenic, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, silver, thallium, uranium and zinc.

Enforcement Site-Wide CD/RAP State of Colorado May 20, 1988 State-led clean up began under CD/RAP (Civil Action No. 83-C-2387). Response Action completed by PRP from September 1, 1988 to September 30, 1999.

Response Action Site-Wide Remedial Action State of Colorado 1988-1991 (1996 Maloit)

Approximately 1 million cubic yards of roaster material and tailings from OTP, Rex Flats and Maloit Park relocated to CTP and contained beneath engineered cover in accordance with the CD/RAP.

Response Action Site-Wide Remedial Action State of Colorado 1988-1990 (modified in 1995-1996)

Two groundwater extraction trenches (French drains) constructed on the north and east side of the CTP in accordance with the CD/RAP. Uncontaminated water diversion (run-on) ditches constructed around waste rock piles in Gilman, including the diversion of Rock Creek by a 600-foot long culvert. Trenches became operational in 1989.

Response Action Site-Wide Remedial Action State of Colorado 1988-1996

CTP dewatered, re-contoured to 5:1 slopes, surface water controls constructed, covered with multi-layered low-permeability cap with drainage layers on the side slopes and vegetated. Temporary Cell constructed. Work completed in accordance with the CD/RAP.

Response Action Site-Wide Remedial Action State of Colorado 1988 Lower surge pond on CTP installed.

Investigation Site-Wide Monitoring Well Installation

State of Colorado 1989-1990 Monitoring wells installed in OTP and Rex Flats areas to assess groundwater quality.

Response Action Site-Wide Remedial Action State of Colorado 1989

UGDT constructed to reduce groundwater recharge west of CTP run-on diversion ditch and north of Maloit Park Road. Rock Creek diverted around waste rock to river.

Risk Assessment Site-Wide HHRA State of Colorado March 1, 1989 HHRA completed by CDH/DCEED.


TABLE 1


Event Type Operable

Unit Action



Risk Assessment Site-Wide HHRA State of Colorado August 7, 1989 Risk Assessment completed for metals exposure at Minturn Middle School.

Response Action Site-Wide Remedial Action State of Colorado September 1989-1990

As water levels in the mine rose, seepage began to reach Eagle River; PRP installed a package WTP to treat water from mine pool and seepage from mine. Existing tailings pipeline to transport mine water to WTP modified and a second surge pond constructed on CTP.

Risk Assessment Site-Wide HHRA State of Colorado March 1990

Assessment of Risk Associated with the Potential Exposure of Children to Metals in Airborne Mine Wastes at the Minturn Middle School and Maloit Park Area submitted by CDH/DCEED.

Enforcement Site-Wide CD/RAP Amendment

State of Colorado May 1990

State of Colorado and PRP amended CD/RAP under Civil Action No. 83-C-2387 by the addition of a package, chemical WTP, a second lined surge pond, a mine seepage collection system, expanded groundwater/surface water monitoring, an annual contaminant loading report, temporary sludge disposal at CTP, Rock Creek grouting and evaluation and OTP groundwater reduction.

Investigation Site-Wide FS Addendum EPA September 1990 EPA announced FS Addendum (released in 1992).

Response Action Site-Wide Remedial Action EPA, State of Colorado

November 1990

PRP installed three extraction wells in OTP in attempt to reduce the migration of groundwater from OTP to Eagle River. After conducting slug tests, it was concluded that production potential of the wells would be too low to be effective.

Response Action Site-Wide Remedial Action State of Colorado 1991

PRP upgraded to a customized “lime and settling” WTP. Solids were settled out of a clarifier and acid was added to reduce the alkalinity of the treated water to the acceptable discharge limits. Treated water discharged to Eagle River pursuant to the provisions of the discharge permit (CDPS Permit No. CO-0042480).

Response Action Site-Wide Remedial Action State of Colorado 1991 Contaminated material placed in the CTP capped.


TABLE 1


Event Type Operable

Unit Action



Enforcement Site-Wide Notice of Violation EPA April 4, 1991

EPA Water Management Division issued a Notice of Violation to the Colorado Department of Health for violations of the Uncontaminated Water Act Section 301.

Investigation OU2 PA/SI EPA, State of Colorado

October 8, 1991 EPA became aware that hazardous substances may have been abandoned in Gilman. EPA and CDH conducted a PA/SI of the entire property.

Enforcement OU2 CD/RAP Amendment

State of Colorado November 21, 1991

State of Colorado and PRP amended CD/RAP under Civil Action No. 83-C-2387 for a removal action of hazardous substances from town of Gilman. Removal action completed on September 1, 1992.

Risk Assessment OU1 Risk Evaluation State of Colorado 1992

CDH completed risk evaluation from potential consumption of fish in Eagle River. Study concluded no significant increase in cancer risk would be expected.

Response Action OU1 Public Water Supply Well Installation

State of Colorado 1992 PRP reached agreement with the Town of Minturn to install two drinking water wells for the town, located up-gradient of any possible influence from CTP.

Risk Assessment OU1 HHRA State of Colorado January 31, 1992 Risk Assessment for metals exposure of employees at Minturn Middle School and residents of Maloit Park Area completed.

Risk Assessment OU1 HHRA State of Colorado February 2, 1992

Assessment of Risk Associated with the Potential Exposure of Children to Metals in Airborne Mine Wastes at the Minturn Middle School and Maloit Park Area submitted by the Colorado Department of Health, Disease Control and Environmental Epidemiology Division.

Community Participation

OU1 FS Addendum EPA June 17, 1992 FS Addendum released to public for comment.


OU1 Proposed Plan EPA June 30, 1992 Proposed Plan released to the public for comment until July 30, 1992.


TABLE 1


Event Type Operable

Unit Action




OU1 FS Addendum and Proposed Plan

EPA July 2-July 8, 1992

Notice of Availability for both the FSA and Proposed Plan in the Administrative Record published in the Vail Daily and Eagle Valley Enterprise. Other notices appeared in the Vail Trail and the ABC Times.


OU1 Public Meeting EPA July 22, 1992 Public meeting held in Minturn, Colorado to comment on the Proposed Plan.


OU1 FS Addendum EPA July 30-September 14, 1992

Initial public comment period extended once to August 30, 1992. A second extension granted for public comment until September 14, 1992.

Response Action OU1 Remedial Action State of Colorado November 1992 Mine drawdown system began operation using a gravity drain through the Adit No. 5 bulkhead.

CERCLA Milestone OU1 ROD EPA March 29, 1993 EPA issued the OU1 ROD.

Risk Assessment OU1 HHRA TAG April 15, 1993 Final Report on the Health Risk Assessments for the Site submitted to the EPA by Dr. John S. Reif, consultant for the TAG.

Response Action OU1 Remedial Action State of Colorado June 1993 Siphon installed to collect groundwater from Rock Creek to be piped to WTP.

Enforcement OU1 UAO EPA July 7, 1994

EPA issued UAO for Remedial Design and Response Action (EPA Docket No. CERCLA-VIII-94-19). Interim measure put in place to allow the implementation of certain actions in the ROD.

Enforcement OU1 CD/RAP Amendment

State of Colorado July 23, 1993 State of Colorado and PRP amended CD/RAP under Civil Action No. 83-C-2387 to encompass construction activities for 1993.

Risk Assessment OU1 HHRA State of Colorado July 30, 1993 Human Health Risk Assessment for Maloit Park Wetlands and Screening-Level Assessment for Selected Study Areas of the Site submitted.

General Milestone Site-Wide Property Transfer N/A 1994 Viacom acquired Paramount and its holdings. Response Action OU1 Remedial Action State of Colorado 1994 Sludge press system installed for solids from WTP.

Response Action OU1 Remedial Action EPA, State of Colorado

1995 Rock Creek culvert diversion extended by 800-feet.

Investigation OU1 Monitoring Well Installation

EPA, State of Colorado

1995 Four monitoring wells installed in railroad ballast at the Belden railroad siding.


TABLE 1


Event Type Operable

Unit Action



Investigation OU1 Runoff Metal Loading Study


1995-1997

Study implemented to assess runoff metal loading from waste rock piles in Gilman and Belden areas to evaluate potential water quality impacts to Eagle River. As a result, three additional run-on control ditches were installed in 1997.

Enforcement OU1 UAO Amendment EPA May 30, 1995 Amendment No. 1 to the Remedial Design and Response Action UAO issued to encompass additional work outlined in ROD.

Enforcement OU1 CD/SOW EPA, State of Colorado

June 12, 1996 EPA, state of Colorado and PRP entered a Three-Party Partial CD/SOW under Civil Action No. 95-N-2360.

Response Action OU1 Remedial Action State of Colorado 1996 After all roaster material and tailings had been consolidated to CTP, materials capped with an engineered cover.


1996-1997 Lead-zinc concentrate removed from the drying house in Belden and 1 foot of soil in front of the building transported to Temporary Cell at CTP.

Risk Assessment OU2 HHRA EPA February 11, 1997

Risk Assessment Summary for Gilman Town-site based on Recreational Trespasser Soil Exposure Risks and Risk Analysis for the Potential Redevelopment of the Site completed.


OU2 Risk Assessment EPA April 17, 1997 Public Meeting announced in the Eagle Valley Enterprise and Vail Trail.


OU2 Public Meeting EPA April 28, 1997 Public Meeting held to discuss risk assessment.

Investigation OU2 Focused FS EPA June 9, 1997 Focused FS completed. CERCLA Milestone OU2 Proposed Plan EPA September 24, 1997 Proposed Plan issued.

Investigation OU1 Water Quality Monitoring


September 1997

PRP conducted test of UGDT to evaluate discharge flow rates and water quality. After evaluation of results, PRP obtained Minimal Discharge Industrial Wastewater Permit from the Water Quality Control Division and conducted a 90-day test from April to August 1998. Test extended, then terminated on November 9, 1998, due to the increased risk of freezing.


TABLE 1


Event Type Operable

Unit Action




April 1998 O&M Plan for UGDT approved. Operation of UGDT resumed following approval.


June-July 1998 Additional remediation to support revegetation activities in OTP performed. In August, revegetation activities deemed in compliance with CD/SOW.


July 1998 Liberty No. 4 Well installed to collect uncontaminated, recharge water to Eagle Mine and divert to Turkey Creek.

CERCLA Milestone OU2 ROD EPA September 3, 1998 EPA signed ROD for OU2 (soil).

CERCLA Milestone OU1 ESD EPA August 31, 1999 EPA issued ESD to modify the remedy to include Liberty No. 4 Well, implemented voluntarily by PRP.

Investigation OU1 Monitoring Well Installation


September 1999 Three new deeper monitoring wells installed in Belden areas between railroad tracks and bank of Eagle River.

CERCLA Milestone Site-Wide Five-Year Review EPA September 21, 2000 EPA finalized first Five-Year Review.

Investigation OU1 Preliminary Site Closeout

EPA June 28, 2001 Preliminary Site Closeout Inspection conducted.


July 2001 Water collection basin constructed at the base WRP-8 and conveyance pipeline to the Fancy Shaft.

CERCLA Milestone OU1 Preliminary Site Closeout

EPA September 17, 2001 EPA issued Preliminary Site Closeout Report; OU1 declared Construction Complete.

Response Action OU1 Uncontaminated Cleanup Action

State of Colorado October 2002 WRP-8 slope soil and trash removed.


2003 CTP cap achieved compliance and monitoring discontinued.


October 2003

Liberty No. 4 Well deepened, cased and screened. Well drilled out again in September 2004 to improve operation. Release occurred from drilling site in August 2004.

Enforcement OU1 CD/SOW EPA March 10, 2004 EPA, State of Colorado and PRP amended CD/SOW (Civil Action No. 95-N-2360) to update payment information in the CD/SOW.

Response Action OU1 Remedial Action State of Colorado June-July 2004 Additional collection system constructed below WRP-8 with conveyance pipeline to WTP.


TABLE 1


Event Type Operable

Unit Action



General Milestone Site-Wide Property Transfer N/A December 2004 Portions of Site purchased by Ginn Battle North (Ginn) entities.


Site-Wide Five-Year Review EPA March-May 2005 Community interviews conducted for the second Five-Year Review.

Response Action OU1 Remedial Action State of Colorado April 2005 Over-seeding of native perennial forbs in Maloit Park conducted.

CERCLA Milestone Site-Wide Five-Year Review EPA April 2005 Second Five-Year Review Site Inspection conducted. CERCLA Milestone Site-Wide Five-Year Review EPA September 27, 2005 EPA finalized second Five-Year Review.

Investigation OU1, OU3 Remedial Investigation


July 6, 2005-September 15, 2006

RI conducted by ERM to address change in land use and Site cleanup standards in Bolts Lake Area and Areas within OU1.

Response Action OU1 Remedial Action State of Colorado 2006 Vegetation on CTP, Rex Flats and OTP approved.


June 2006

PRP installed three groundwater extraction wells in Belden with connection to the MWTP to WTP. Pumps operated in 2007 and 2008 on a daily basis before vandalized in 2008 and discontinued.


August-September 2006

PRP removed Belden roaster waste (WRP-14) in addition to roaster material surrounding the Copper Tipple Building and disposed of it in Temporary Cell at CTP.

Investigation OU1, OU3 Remedial Investigation


September 15, 2006 BFPP finalized RI for Bolts Lake Area and OU1 Areas.

Risk Assessment OU1, OU3 HHRA EPA, State of Colorado

February 2, 2007 BFPP completed HHRA for Bolts Lake Area and OU1 Areas.

Investigation OU3 Feasibility Study EPA, State of Colorado

February 16, 2007 BFPP began FS for OU3 (North Property redevelopment, OU1 area).


October 2007 PRP constructed groundwater extraction trench in Belden.

Response Action Off-Site Removal Action EPA 2008

EPA conducted removal action in the Belden area to construct concrete block wall to contain waste rock from abandoned mines held in place with deteriorating wooden crib walls.


TABLE 1


Event Type Operable

Unit Action



General Milestone OU1 Water Quality Standards

State of Colorado June 2008 Water Quality Control Commission of the CDPHE adopted new WQS for the Site. Revised WQS effective January 2009.

CERCLA Milestone Site-Wide Five-Year Review EPA September 30, 2008

EPA signed third Five-Year Review declaring the remedy “not protective” because it did not meet the new WQS. (Five-Year Review was strategically conducted at a 3-year interval in order to document the need for a more protective remedy.)

General Milestone OU1 Property Transfer N/A 2009 Battle North, LLC took over development of North Property from Ginn Battle North.

Investigation OU1 Focused FS EPA, State of Colorado

2009 CDPHE drafted Statement of Work to develop the FFS.


OU1 Focused FS EPA, State of Colorado

March 2009 EPA and CDPHE met with stakeholders asking for comments on the FFS “Study Plan.” No comments received.

Response Action OU1 Remedial Action State of Colorado June 2009 Concrete dam constructed to improve collection of runoff from WRP-8.



August 2009 EPA and CDPHE met with stakeholders to discuss monitoring results of FFS and PLA and requested comments on PLA.



November 2009 Stakeholder comments received on PLA and extension granted at request of stakeholders.

Contamination Release

OU1 Pond Failure State of Colorado December 22, 2009 Release occurred from lower surge pond directly to Eagle River from WTP.


January 2010 Bypass pipeline constructed through Rex Flats in response to freezing of pipe on elevated portion of trestle.

CERCLA Milestone OU1 Focused FS EPA, State of Colorado

February 2010 EPA and CDPHE approve PLA for FFS.

Investigation OU3 RI Addendum EPA, State of Colorado

May 2010 Survey of seeps and ponded water conducted in areas around Bolts Lake and CTP.

Investigation OU3 RI Addendum EPA, State of Colorado

May 17, 2011 RI Addendum to 2006 RI signed and finalized.


TABLE 1


Event Type Operable

Unit Action





September 24, 2011 EPA and CDPHE met with stakeholders to present draft FFS. (Review period September 24, 2011 through October 28, 2011).



October 6, 2011 Comments received from TAG on FFS.



October 11, 2011 EPA and CDPHE received additional data from Eagle River Water and Sanitation District to incorporate into FFS.



2012 Arsenic sample collection from Eagle River began.

Investigation OU1 Pilot Study EPA, State of Colorado

Spring 2012 EPA and CDPHE requested Pilot Study for spring 2012 to help address stakeholder comments.



June 18, 2012 EPA and CDPHE met with PRP to resume work on FFS and address agency and stakeholder comments, including pilot test results.


OU1 Stakeholder Meeting EPA, State of Colorado

April 2013 Update issued to stakeholders on FFS status and Proposed Plan.

Investigation OU1 Focused FS EPA, State of Colorado

July 26, 2013 FFS completed to evaluate alternatives designed to achieve WQS on Eagle River as it passes through Site.

CERCLA Milestone OU1 Proposed Plan EPA, State of Colorado

September 24, 2013 CDPHE prepared Draft Proposed Plan. Comments delivered in spring 2014 and included additional requests to discuss arsenic at the Site.

CERCLA Milestone Site-Wide Five-Year Review EPA September 27, 2013 EPA signed fourth Five-Year Review.

Investigation OU1, OU3 Feasibility Study EPA, State of Colorado

December 18, 2013 BFPP submitted FS for areas within OU1 of Site later designated as OU3.

Investigation OU1 Focused FS Addendum


May 2014

EPA and CDPHE reviewed arsenic data submitted in 2013 Annual Report from PRP. Determined an addendum to FFS necessary to complete Administrative Record for arsenic.



August 2014 EPA and CDPHE determined additional sampling for arsenic needed. Requested PRP conduct sampling in spring 2015.


TABLE 1


Event Type Operable

Unit Action





September 17, 2014

EPA and CDPHE met with stakeholders to discuss path forward for arsenic, including a TI Waiver, resulting in delay to Proposed Plan and ROD Amendment.

Risk Assessment OU1 HHRA EPA, State of Colorado

October 30, 2014 EPA Toxicologist prepared memo documenting risks posed by arsenic to human health.

CERCLA Milestone OU1 Remediation Goals EPA, State of Colorado

January 20, 2015 EPA calculated remediation goals for surface water.



March 13, 2015 PRP prepared SAP for arsenic source sampling; expanded to include groundwater and surface water locations beyond Eagle River.



June 3, 2015 PRP submitted arsenic data to EPA and CDPHE in Arsenic Results Report.



November 17, 2015 EPA and CDPHE met with stakeholders to discuss TI Waiver status and Emergency Response Plan.

Investigation OU1, OU3 Feasibility Study EPA, State of Colorado

January 2016 EPA and CDPHE finalized (with corresponding comments and responses) FS prepared by BFPP in 2013.

Investigation OU1 TI Evaluation EPA, State of Colorado

March 2016

HMWMD of CDPHE submitted TI Evaluation Report for Arsenic in Surface Water. Evaluated arsenic data for Site; presented information to demonstrate technical impracticability to attain Colorado Surface Water Quality Standard of 0.02 µg/l arsenic in Eagle River at Site. Report included alternative remedial strategies to reduce arsenic concentrations to maximum extent practicable.



April 12, 2016 PRP began work on Arsenic Addendum to the FFS.



April 15, 2016 EPA and CDPHE met with stakeholders, discussed TI Waiver status and agreed to release TI Evaluation in advance of Proposed Plan.

CERCLA Milestone OU1 TI Waiver EPA April 26, 2016 EPA Headquarters accepted TI Evaluation Report as compliant with requirements.


OU1 TI Waiver State of Colorado May 4, 2016 CDPHE posted TI Evaluation Report on website and announced availability via email.


TABLE 1


Event Type Operable

Unit Action





August 17, 2016 EPA and CDPHE met with stakeholders to discuss TI Waiver status.


OU1 TI Waiver EPA, State of Colorado

November 17, 2016 and January 12, 2017

Comments received from stakeholders on TI Evaluation Report.


January 9, 2017 CDPHE issued revised draft OU1 Proposed Plan for internal review.



January 27, 2017 PRP submitted revised draft of FFS Addendum.


OU1 Focused FS Addendum


February 13, 2017 FFS Addendum for arsenic completed and posted on CDPHE website for stakeholders review.

CERCLA Milestone OU1, OU3 Proposed Plan ROD


February 21, 2017 ROD Milestone Meeting; EPA peer-review of draft Proposed Plan.


March 27-May 31, 2017

EPA Headquarters consultation on OU1 Proposed Plan; revised to address Headquarters comments.


OU1,OU3 Proposed Plan EPA, State of Colorado

June 28, 2017 Proposed Plans released for public comment (June 28, 2017 to September 11, 2017).


OU1, OU3 Stakeholder Meeting EPA, State of Colorado

July 6, 2017 EPA and CDPHE met with community member to answer questions about Proposed Plans.


OU1, OU3 Public Notice EPA, State of Colorado

July 20, 2017 Public notice of public comment period extension published in Vail Daily.


OU1 Community Stakeholder Meeting


July 24, 2017 EPA and CDPHE met with Eagle River Watershed Council and Eagle River Water & Sanitation District to answer questions regarding Proposed Plan.


OU1, OU3 Public Hearing EPA, State of Colorado

July 25, 2017 EPA and CDPHE held formal Public Hearing regarding OU1 Amendment Proposed Plan and OU3 Proposed Plan.


OU1, OU3 Panel Discussion EPA, State of Colorado

August 1, 2017 EPA and CDPHE participated in Vail Symposium panel discussion; copies of Proposed Plans provided to attendees.


OU1, OU3 Site Tours EPA August 2, 2017 EPA and CDPHE conducted two public tours of Site; copies of Proposed Plans provided to attendees.

General Milestone OU1 ROD Amendment EPA, State of Colorado

September 2017 EPA and CDPHE issue ROD Amendment for OU1.


TABLE 1


Event Type Operable

Unit Action



General Milestone OU3 ROD EPA, State of Colorado

September 2017 EPA and CDPHE issue ROD for OU3.

Remedial Action OU1 Groundwater collection system


Pending

Installation of french drain, extraction wells, or trench designed to collect groundwater at Belden, from the Mill Level of the mine and at the mouth of Rock Creek to convey water to WTP.

Remedial Action OU3 Implementation of ICs

State of Colorado Pending ICs implemented for protection of remedial components on OU3.

Remedial Action OU3 Soil Remediation EPA, State of Colorado

Pending Complete soil remediation construction activities (excavation, demolition, soil exposure barrier, grading) pursuant to OU3 ROD.

Notes: BFPP Bona Fide Prospective Purchaser CD Consent Decree CDH Colorado Department of Health CDH/DCEED Colorado Department of Health/Disease Control and Environmental

Epidemiology Division CDPHE Colorado Department of Public Health & Environment CD/RAP Consent Decree and Remedial Action Plan CD/SOW Consent Decree and Statement of Work CERCLA Comprehensive Environmental Response, Compensation and Liability Act CTP Consolidated Tailings Pile EPA U.S. Environmental Protection Agency ERM Environmental Resources Management ESD Explanation of Significant Differences FFS Focused Feasibility Study FS Feasibility Study FSA Feasibility Study Addendum HHRA Human Health Risk Assessment HMWMD Hazardous Materials and Waste Management Division MOA Memorandum of Agreement N/A Not applicable NPL National Priorities List NRD Natural resource damages O&M Operations and Maintenance OTP Old Tailings Pile OU Operable Unit

PA/SI Preliminary assessment and site investigation PCB Polychlorinated biphenyl PLA Preliminary List of Alternatives PRP Potentially Responsible Party RI Remedial Investigation ROD Record of Decision SAP Sampling and Analysis Plan TAG Technical Advisory Group TI Technical Impracticability UAO Unilateral Administrative Order UGDT Upgradient Diversion Trench USFS U.S. Forest Service WRP Waste Rock Pile WQS Water Quality Standard WTP Water Treatment Plant

OU1 ROD Amendment September 2017

TABLE 2 SUMMARY OF WATER QUALITY STANDARD EQUATIONS BY SEGM ENT

OU1 ROD AMENDMENT - Eagle Mine Superfund Site

Equation

Segment 2 5a 5b 5c

Zin

c (D

isso

lved

)

Rainbow Equations A:0.978*e 0.8537[ln(hardness)]+2.1302 C:0.986*e 0.8537[ln(hardness)]+1.9593

All Year Jan 1 – Apr 30

Sculpin Equations A:0.978*e 0.8537[ln(hardness)]+1.4189 C:0.986*e 0.8537[ln(hardness)]+1.2481

May 1 – Dec 20

All Year

Table Value Standard (TVS) A:0.978*e 0.9094[ln(hardness)]+0.9095 C:0.986*e 0.9094[ln(hardness)]+0.6235 Sculpin:0.986*e 2.140[ln(hardness)]-5.084

[Sculpin equation where mottled sculpin are expected and hardness is less than 102 mg/l as CaCO3]

All Year

Cop

per

(Dis

solv

ed)

Tubifex equations A:0.96*e 0.9801[ln(hardness)] – 1.1073 C:0.96*e 0.5897[ln(hardness)] – 0.0053

All Year

Ephoron equations A:0.96*e 0.9801[ln(hardness)]-1.5865 C:0.96*e 0.5897[ln(hardness)]-0.4845

All Year All Year

Table Value Standard (TVS) A:0.96*e 0.9422[ln(hardness)]-1.7408 C:0.96*e 0.8545[ln(hardness)]-1.7428

All Year

Cad

miu

m

(Dis

solv

ed)

Site-specific A:TVS C:(1.101672-[(ln(hardness)*(0.041838)])* e(0.7998 [ln( hardness)]-3.1725)

All Year All Year All Year

Table Value Standard (TVS) A:(1.136672-[ln(hardness)*(0.041838)])*

e(0.9151[ln(hardness)]-3.1485) Trout:(1.136672-[ln(hardness)*(0.041838)])*

e(0.9151[ln(hardness)]-3.6236) C:(1.101672-[(ln(hardness)*(0.041838)])* e(0.7998 [ln( hardness)]-4.4451)

All Year

Notes: A Acute C Chronic µg/L Micrograms per liter


TABLE 3 FOCUSED FEASIBILITY STUDY TIMELINE

OU1 ROD AMENDMENT – Eagle Mine Superfund Site

Date Activity 6/2008 Colorado Water Quality Control Commission adopts new WQS.

10/2008 The EPA issues 5-year review declaring the remedy “not protective” because it does not meet the new WQS (the Five-Year Review was strategically conducted at a 3-year interval in order to document the need for a more protective remedy)

2/2009 CBS develops FFS “Study Plan” (this document is not part of the normal Superfund process but was developed in order to give the stakeholders the opportunity to review and comment on the data collection effort for the FFS).

3/2009 The EPA and CDPHE meet with stakeholders ask stakeholders for comments on the “Study Plan.” No comments were received.

Spring 2009 CBS implements study plan, collects data for use in FFS.

8/2009

EPA and CDPHE meet with stakeholders to discuss the monitoring results of the FFS Study completed in Spring 2009 and to discuss the PLA. Agencies request stakeholder comments on the PLA. (PLA is not part of normal Superfund process, but was developed in order to give the stakeholders the opportunity to review and comment on the alternatives to be included in the FFS.)

11/2009 Stakeholder comments received on PLA – extension granted at request of stakeholders. 2/2010 PLA approved by EPA and CDPHE. 4/2010 Agencies receive first draft of the FFS.

6/2010 Agencies send comments on draft, require revision, agencies also re-submit stakeholder comments to CBS that were received as part of the PLA review.

11/2010 Agencies receive second draft of the FFS. 3/2011 Agencies send comments on second draft, require revision. 7/5/2011 Agencies receive third draft of the FFS. 8/24/2011 EPA and CDPHE meet with stakeholders to present draft FFS. 8/24/2011- 10/28/2011

Stakeholder review period for draft FFS. Note that EPA process normally does not allow release of draft FFS for review/comment.

10/6/2011 Comments received from TAG.

10/11/2011 Agencies receive additional data from the Eagle River Water and Sanitation District to be incorporated into the FFS.

10/31/2011 Agencies extend the comment deadline, as requested by stakeholders. 11/5/2011 Comments received from the ERWU. 12/5/2011 CBS declines to address stakeholder comments until incorporated into agency comments.

1/6/2012 Agencies request Pilot Study for Spring of 2012, to help address some of the stakeholder comments, drought conditions interfere with study results.

6/18/2012 Results of Pilot Study received from CBS.

6/18/2012 EPA and CDPHE meet with CBS to resume work on the FFS to address agency and stakeholder comments, include pilot test results.

7/12/2012 & 7/13/2012

EPA sends combination of agency and stakeholder comments to CBS, request revision of the FFS document. EPA requested responses to the comments in 45 days.

7/23/2012 CBS requests an extension to 120 days for Response to Comments. 8/17/2012 Additional comments submitted to CBS from CDPHE.

9/27/2012 EPA agrees to extend Response to Comment deadline from 45 to 90 days, calculated from receipt of CDPHE comments.

11/15/2012 Responses to Comments received from CBS.

12/6/2012 Agencies meet with CBS to go over Response to Comments. CBS instructed to produce revised draft FFS.

1/24/2012 Revised Draft FFS received from CBS. 2/2012 to present

Revised Draft FFS under Agency review to determine if all previous comments have been addressed. Revisions will be necessary before a Final document is produced.

4/2013 Stakeholder Meeting: Update provided on FFS status, proposed plan process explained.




Date Activity

Mid-2013 Agencies Prepare Comment/Response Document for FFS while CBS revises documents to address comments.

9/2013 CDPHE prepares Draft Proposed Plan; sent to EPA for review on 9/24/13 . Winter 2013-2014

Administrative Record Preparation.

3/2014 ROD Milestone Meeting: EPA per-review of draft Proposed Plan.

4/2014 Comments received on Draft Proposed Plan. EPA requests revision to the Proposed Plan, requests additional discuss for arsenic.

5/2014 CDPHE and EPA review arsenic data submitted in 2013 Annual Report from CBS. Agencies determine that an addendum to the FFS must be prepared to complete Administrative Record for arsenic.

Summer 2014 Agencies inform CBS and Stakeholders about delay to address arsenic.

8/2014 Agencies determine that additional sampling for arsenic will be needed. Request that CBS conduct sampling in March/April 2015.

9/17/2014 CDPHE and EPA meet with Stakeholders, discuss path forward for arsenic, including TI Waiver, and resulting delay to Proposed Plan and ROD amendment.

10/30/14 EPA Toxicologist, Susan Griffin prepares a memo documenting the risks posed by arsenic to human health.

1/20/15 EPA Calculates remediation goals for surface water (Memo from Susan Griffin). 3/13/15 CBS Prepares Sampling and Analysis Plan for Arsenic source sampling. 3-4/2017 CBS collects arsenic source samples. 6/3/15 CBS submits arsenic data to the Agencies, Arsenic Results Report. 7/2/15 CDPHE submits 1st draft of TI Evaluation Report to EPA for transmittal to EPA Headquarters. 10/27/15 CDPHE submits 2nd draft of TI Evaluation Report to EPA for transmittal to EPA Headquarters. 11/17/15 CDPHE and EPA meet with Stakeholders, discuss TI Waiver status, Emergency Response Plan. 4/12/15 CBS begins work on Arsenic Addendum to the FFS.

4/15/16 CDPHE and EPA meet with Stakeholders to discuss TI Waiver status; agree to release the TI Evaluation in advance of Proposed Plan.

4/26/16 Approval from EPA Headquarters for TI Evaluation Report. 5/4/16 CDPHE posts TI Evaluation report on website and announces availability via email. 8/2016 CBS submits 1st draft of Arsenic Addendum. 8/17/16 CDPHE and EPA meet with Stakeholders, discuss TI Waiver status. 9/12/16 & 10/17/16

CDPHE and EPA submit comments on Addendum to CBS.

11/17/16 & 1/12/17

Comments received from stakeholders on TI Evaluation Report.

1/9/17 CDPHE issues revised draft of OU1 Proposed Plan for internal review. 1/27/17 CBS submits revised draft of Addendum.

2/14/17 FFS Addendum for Arsenic posted on CDPHE website/email to stakeholders announcing availability of document for review.

2/21/17 ROD Milestone Meeting: EPA per-review of draft Proposed Plan. 3/27/17-5/31/17 (various dates)

Consultation with EPA Headquarters regarding OU1 Proposed Plan. Plan revised to address Headquarter comments.

6/28/17 Proposed Plan released to the public for public comment.

7/6/17 CDPHE and EPA meet with Jeff Tucker (as a stakeholder) to answer questions about the Proposed Plans.

7/24/17 CDPHE meet with ERWC and Eagle River Water & Sanitation District to answer questions regarding Proposed Plan.




Date Activity 7/25/17 Formal Public Hearing regarding Proposed Plan.

8/1/2017 CDPHE/EPA participate in Vail Symposium panel discussion, Proposed Plans mentioned but not discussed in detail, copies of plan provided to attendees.

8/2/2017 Two public tours of the Eagle Mine site conducted, copies of plan provided to attendees.

Notes: CBS CBS Operations, Inc. CDPHE Colorado Department of Public Health & Environment CRS Colorado Revised Statutes CWA Clean Water Act ERWC Eagle River Watershed Council ERWU Eagle River Water Users EPA U.S. Environmental Protection Agency FFS Focused Feasibility Study PLA Preliminary List of Alternatives ROD Record of Decision TAG Technical Advisory Group TI Technical Impracticability WQS Water Quality Standard

FIGURES

FIGURE 1Vicinity Map

Eagle Mine Superfund SiteEagle County, Colorado

Projection: UTM Zone 13 NAD83Image:Bing Maps

Data: ESRI, University of Montana

General SiteLocationInterstate

Surface Water

Legend

US Highway

Project Location

Path: K:\GIS Library\Eagle_Mine\Maps\Figure_1_OU1ROD_A_Vicinity_09252017.mxd

µ_̂

0 2 4Miles

FIGURE 2Site Features

Eagle Mine Superfund SiteEagle County, Colorado

Projection:NAD 1983 State PlaneColorado Central Feet

Image:Bing MapsData: ESRI, University of Montana

µ

Site Features

Surface Water

Legend

Highway

Eagle MineWorkings

D & RGW Railroad

"

Vail Ski and SnowboardAcademy

Path: K:\GIS Library\Eagle_Mine\Maps\Figure_2_OU1ROD_A_Features_09222017.mxd

0 2,000 4,000Feet

FIGURE 3Eagle River Basin SegmentsEagle Mine Superfund Site

Eagle County, Colorado

NAD 1983 State Plane ColoradoCentral FeetData: ESRI

µ

Site Features

Surface Water

Legend

Highway

Segment 2Segment 5aSegment 5bSegment 5cSegment 7aSegment 7b

Path: K:\GIS Library\Eagle_Mine\Maps\Figure_3_OU1ROD_A_River_09232017.mxd

Stream Gage@?

0 0.5 1Miles

FIGURE 4 Rock Creek and Belden Areas Eagle Mine Superfund Site Eagle County, Colorado

Source: CBS Operations, Inc. 2017. Focused Feasibility Study Addendum, Eagle Mine Site, Figure 2, Prepared by NewFields. February. Original figure copied for use in the 2017 OU1 ROD Amendment.

!Legend

Proposed Trenches

Interceptor Trench

Pipeline Extension

Existing Pipe & Trenches

Mine Seep Pipeline

Copper Tipple Trench

0 70 140 210 28035

Feet

FIGURE 5 Collection Trench Location Eagle Mine Superfund Site Eagle County, Colorado

Source: CBS Operations, Inc. 2013. Focused Feasibility Study, Eagle Mine Site, Minturn, Colorado, Figure 20. Prepared by Newfields. July 26. Original figure copied for use in the 2017 OU1 ROD Amendment.

APPENDIX A TECHNICAL IMPRACTICABILITY EVALUATION REPORT

Revised 5/16 to correct the Table of Contents

Technical Impracticability

Evaluation Report

Arsenic

in

Surface Water

At the Eagle Mine

Superfund Site

Operable Unit 1

March 2016

ii

Table of Contents

Acronym List .......................................................................................................................................................... iv

Section 1 Introduction......................................................................................................................................... 1

1.1 Problem Statement ................................................................................................................................... 1

1.2 Purpose ......................................................................................................................................................... 2

1.3 Scope .............................................................................................................................................................. 2

1.4 Report Organization ................................................................................................................................ 2

Section 2 Site Description .................................................................................................................................. 4

2.1 Site History and Location ...................................................................................................................... 4

2.2 Site Setting .................................................................................................................................................. 4

2.2.1 Geology ................................................................................................................................................ 4

2.2.2 Soils, Vegetation and Climate ...................................................................................................... 6

2.2.3 Surface Water Hydrology ............................................................................................................. 6

2.2.4 Groundwater ..................................................................................................................................... 9

2.3 Landownership and Use ........................................................................................................................ 9

Section 3 Applicable or Relevant and Appropriate Requirements ................................................. 10

3.1 Regulation of Arsenic Pursuant to the Safe Drinking Water Act ......................................... 10

3.2 Regulation of Arsenic Pursuant to the Clean Water Act (for Surface Water) ................. 10

3.2.1 Water Supply Standard ............................................................................................................... 10

3.2.2 Fish Ingestion Standard .............................................................................................................. 10

3.2.3 Water+Fish Standard ................................................................................................................. 11

3.3 ARARs for the Eagle Mine Site .......................................................................................................... 11

Section 4 Previous Decisions ......................................................................................................................... 15

Section 5 Remedial Actions Conducted ..................................................................................................... 16

Section 6 Existing Data and Analysis .......................................................................................................... 20

Section 7 Conceptual Site Model .................................................................................................................. 27

Section 8 Evaluation of Restoration Potential ........................................................................................ 28

8.1 Primary and Secondary Sources ...................................................................................................... 28

8.2 Treatment Technologies ..................................................................................................................... 28

8.3 Background Concentrations in the Eagle River ......................................................................... 29

8.4 Restoration Potential and Restoration Timeframe .................................................................. 30

iii

Section 9 Alternative Remedial Strategy .................................................................................................. 31

9.1 Alternate Remedial Goal for Arsenic .............................................................................................. 31

9.2 Remedial Alternatives Considered in the FFS ............................................................................ 31

9.3 Comparative Analysis of Alternatives ............................................................................................ 33

Section 10 Summary and Conclusions ....................................................................................................... 34

Section 11 TI Zone Boundaries ..................................................................................................................... 34

Section 12 References ...................................................................................................................................... 36

Tables

Table 1 - Excerpt from Regulation 33 ........................................................................................................ 13

Table 2 - WTP Influent/Effluent Concentrations ................................................................................... 17

Table 3 - Arsenic Concentration in the Eagle River .............................................................................. 20

Table 4 - Change in Arsenic Concentration in the Eagle River ......................................................... 22

Table 5 - Arsenic Load Estimates by River Reach ................................................................................. 24

Table 6 - Total Arsenic in Groundwater Samples .................................................................................. 25

Table 7 - Arsenic Source Load Estimates, Segment 5a ........................................................................ 26

Table 8 - Remedial Alternatives Evaluated in the FFS ......................................................................... 32

Figures

Figure 1 - Eagle Mine Site Location and Features .................................................................................... 5

Figure 2 - Stream Segments and Surface Water Sampling Locations ............................................... 7

Figure 3- Eagle River Hydrograph .................................................................................................................. 8

Figure 4 - Eagle Mine Seepage Collection and Conveyance Systems ............................................. 18

Figure 5 - Eagle Mine Water Treatment Plant Schematic .................................................................. 19

Figure 6 - Arsenic in the Eagle River and Tributaries .......................................................................... 21

Figure 7 - TI Zone Boundary .......................................................................................................................... 35

Appendix A – Focused Feasibility Study Addendum 2015 Arsenic

Results (Excerpt)

Appendix B - Memoranda from Susan Griffin, PhD, to Les Sims dated October 30, 2014 and January 20, 2015

iv

Acronym List

AM Adsorptive Media

ARAR Applicable or Relevant and Appropriate Requirements

CBS CBS Operations, Inc.

CD/RAP Consent Decree/Remedial Action Plan

CD/SOW Consent Decree/Statement of Work

CDPHE Colorado Department of Public Health and Environment

CDPS Colorado Discharge Permit System

CERCLA Comprehensive Environmental Response, Compensation and Liability Act

CFS Cubic Feet Per Second

COC Contaminant of Concern

CTP Consolidated Tailings Pile

FFS Focused Feasibility Study

FI Fish Ingestion

GPM Gallons Per Minute

IX Ion Exchange

MCLs Maximum Contaminant Levels

MDL Method Detection Limit

OTP Old Tailings Pile

OUs Operable Units

PQL Practical Quantification Limit

PRP Potentially Responsible Party

ROD Record of Decision

TREC Total Recoverable

W+F Water + Fish

WP-8 Waste Rock Pile 8

WQCC Colorado Water Quality Control Commission

WQCD Water Quality Control Division

WTP Water Treatment Plant

WS Water Supply

Section 1 Introduction

1


Arsenic is a naturally occurring element that is commonly found in geologic formations and is known to occur in surface water and groundwater in Colorado. Arsenic can be released or mobilized into water through natural processes and anthropogenic activities. Natural processes, such as groundwater movement in aquifers, surficial erosion of arsenic laden rocks and soil, and volcanic and geothermal influence, have the ability mobilize arsenic. Similarly, industrial activities, such as mining and smelting, can introduce soluble forms of arsenic into the environment. Arsenic has also been introduced into the environment as a pollutant from agricultural and residential pesticides, and industrial products, such as wood preservatives, paints, dyes, pesticides, herbicides, and soaps. The ubiquitous occurrence of arsenic in the environment greatly affects the restoration potential.

This report evaluates arsenic data for the Eagle Mine Superfund Site (Site) Operable Unit 1 and presents information to demonstrate that it is technically impracticable to attain the current Colorado Surface Water Quality Standard (CSWQS) of 0.02 µg/l arsenic in the Eagle River at the Site. This report includes alternative remedial strategies that will reduce arsenic concentrations to the maximum extent practicable.

This report provides a basis to determine whether remediation to reduce arsenic in surface water to attain the CSWQS is technically impracticable by providing the following information:

Arsenic data collected for surface water at the Site. Arsenic data collected from various contaminant sources at the Site. A conceptual site model (CSM) for arsenic contamination to surface water at the Site. The specific Applicable or Relevant and Appropriate Requirement (ARAR) for which

a TI waiver is sought. The areas where the TI waiver will apply. An analysis of the restoration potential of remedial alternatives intended to attain

ARARs at the Site within a reasonable timeframe. Information regarding analytical methods and water treatment technologies that

demonstrate that arsenic cannot be measured or treated to the level of the current CSWQS.

Evaluation of alternative remedial strategies that are protective of human health and the environment and meet other CERCLA Section 121 statutory requirements, are cost-effective and incorporate permanent solutions and treatment to the maximum extent practicable.

1.1 Problem Statement

Arsenic was not recognized as a Contaminant of Concern (COC) for surface water in the 1993 Eagle Mine OU1 Record of Decision (ROD) because arsenic was not detected in the Eagle River using the laboratory methods in effect at the time. Therefore, no ARAR for arsenic was selected in the ROD and arsenic was not included in the on-going surface water monitoring program at the Site. However, sampling conducted by the Potentially Responsible Party (PRP) in 2012 and 2013, using updated analytical methodologies achieving lower detection limits, confirmed that arsenic is present at the Site in


2

concentrations that exceed the current CSWQS of 0.02 µg/l. As a result, the EPA and the State of Colorado determined that arsenic is a COC for surface water and that the 0.02 µg/l CSWQS is a potential ARAR for the Site.

Although the agencies have identified the 0.02 µg/l CSWQS as a potential ARAR for the Site, it is technically impracticable to meet the 0.02 µg/l standard at the Eagle Mine Site. Background concentrations in the Eagle River exceed 0.02 µg/l, analytical methods cannot measure this low and treatment technologies have not been developed to effectively remove arsenic consistently to meet levels below 0.02 µg/l. These issues are discussed in detail in Section 3. For these reasons, a statutory waiver under CERCLA § 121(d)(4) of the 0.02 µg/l arsenic standard for Segments 5a, 5b, 5c and 7b of the Eagle River is necessary, based on technical impracticability. The amended ROD will reflect the waiver and will instead reference an alternate remedial goal of 3 µg/l, established using standard Superfund risk-based methods.

Additional remediation is being planned for the Site and a Focused Feasibility Study (FFS) is underway. It is anticipated that the selected remedy will remove additional arsenic, as well as other metals, but even so, will not be capable of meeting a standard that cannot be measured using conventional laboratory techniques. This document addresses the analysis of the TI for achieving arsenic reduction to levels that would meet the CSWQS.

1.2 Purpose

Based on the defined area encompassed by Eagle River Segments 5a, 5b, 5c and 7b which do not attain the applicable surface water standards, an evaluation was performed to assess the technical impracticability of remediating contaminant sources at the Site to achieve the CSWQS for arsenic. The results of this evaluation are presented in this report.

1.3 Scope

This document explores technical impracticability of achieving the goal of attaining the CSWQS for arsenic in the Eagle River Segments 5a, 5b, 5c and 7b which flow through the Eagle Mine Superfund Site. This TI evaluation is limited to evaluating the arsenic CSWQS in surface water. The extent of this TI evaluation is limited to surface water bodies originating within or flowing through the Eagle Mine Superfund Site.

1.4 Report Organization

The organization of this report is structured in accordance with the Guidance for Evaluating the Technical Impracticability of Ground Water Restoration (EPA 1993). Although the guidance was developed specifically for ground water, the framework for TI decision-making is essentially the same for surface water. This report is also modeled after the document titled "Technical Impracticability Evaluation, Achievement of Arsenic Human Health Standard in Spring-Fed Tributaries" for the Anaconda Regional Water, Waste, & Soils Operable Unit, Anaconda Smelter NPL Site, dated September 2011, prepared by CDM Federal Programs Corporation.

The report is organized into the following sections:


3

Section 1 provides the problem statement, purpose, and scope of this TI Evaluation Report.

Section 2 describes the Site including the physical features and ownership.

Section 3 provides a review of arsenic criteria for water and the derivation and history of the Applicable or Relevant and Appropriate Requirements for arsenic at the Site that are the subject of this technical impracticability evaluation.

Section 4 summarizes previous agency decision documents, OU designations and the history of decisions regarding arsenic in surface water.

Section 5 describes remedial actions conducted that have reduced contamination at the Site and metals concentrations in the Eagle River.

Section 6 summarizes and analyzes the arsenic data collected with an emphasis on determining the source or sources of arsenic entering the river.

Section 7 presents a conceptual site model for how arsenic contamination reaches surface water at the Site.

Section 8 identifies and evaluates strategies to achieve restoration of surface water that has arsenic concentrations greater than the arsenic CSWQS of 0.02 µg/L.

Section 9 evaluates alternative remedial strategies that are technically practicable, protective of human health and the environment, and satisfy the statutory and regulatory requirements of CERCLA.

Section 10 summarizes the results of this TI evaluation.

Section 11 provides a listing of water bodies where the surface water TI zone is proposed.

Section 12 lists the references cited in this report and includes the data summary reports containing the data that form the basis for the CSM and TI evaluation.

Section 2 Site Description

4


The Eagle Mine Superfund Site (Site) is a large, complex, abandoned, mining and milling facility located along the banks of the Eagle River near Minturn, Colorado (Figure 1). The Site comprises approximately 235 acres including the Eagle Mine workings, the former town of Gilman, Belden, former roaster pile areas, waste rock piles, Rex Flats, the Old Tailings Pile, the Consolidated Tailings Pile, Maloit Park, groundwater and seep collection systems, a mine‐water conveyance system and a water treatment plant.

EPA established three operable units (OUs) at the Site. OU1 was established to control the transport of metals from sources of mine waste that impact the Eagle River and groundwater resources. EPA issued the OU1 ROD in 1993. OU2 was established to evaluate potential human health risks at the Site. OU3 was established for a private residential development proposed for the OU1 area, which would require additional cleanup actions beyond those selected in the OU1 ROD.

2.1 Site History and Location

Mining began in the area in 1879. In 1905, a roaster and magnetic separator were constructed near Belden by the Pittsburg Gold and Zinc Company to roast and separate ore. By 1916, the Empire Zinc Company of Colorado, a subsidiary of the New Jersey Zinc Company, completed consolidation of the principal mines into what is known as the Eagle Mine. An underground mill was constructed and mill tailings were slurried down the valley and deposited first in the Old Tailings Pile (OTP), and later into what is now called the Consolidated Tailings Pile (CTP). The Eagle Mine closed in 1984 when electrical power to the mine was shut off and the mine workings flooded. The Eagle Mine workings were developed in the lower levels of Battle Mountain between the towns of Red Cliff and Minturn.

2.2 Site Setting

The Eagle Mine is located along the Eagle River in the Southern Rocky Mountain Province. The Site area ranges in elevation from 8,100 feet to 8,950 feet above sea level.

2.2.1 Geology

Pockets of oxidized silver-lead and oxidized gold-silver ore in the Leadville Dolomite and the Sawatch Quartzite first attracted miners to the area in 1879. After 1905 the primary target was zinc discovered in the Leadville Dolomite. The southern portion of the Site consists of a steep, narrow bedrock canyon, carved into the Sawatch Quartzite and Cross Creek Granite by the Eagle River. This area, known as Belden, served as the main entrances to the early mine workings. The Denver & Rio Grande Railroad narrow gauge reached Belden from Tennessee Pass in 1883 with tracks constructed on both sides of the river on Cross Creek Granite and fill materials composed of talus, mine waste rock, slag and other materials. It is unclear how thick the fill material may be or what the natural configuration of the river channel may have been prior to mining and railroad construction. At Belden there is at least 30 feet of rock talus and fill based on monitor well drilling logs.

The river has cut through the remainder of the geologic section; the Peerless Formation, Harding Sandstone, Chaffee Group, and the Leadville Dolomite, in the northern portion of the Site. The western portion of the OTP contains outcrops of Sawatch Quartzite and Peerless Formation. The


5

Leadville Dolomite and Chaffee Group outcrop along the western portion of the ridge between the CTP and the Bolts Lake Area. The east side, and especially the northeast of Rex Flats contains Chaffee Group and Leadville Dolomite outcrops. The Leadville Dolomite, Peerless Formation, and Sawatch Quartzite dip about 10 and 17 degrees to the northeast (USGS, 1977).

Figure 1 - Eagle Mine Site Location and Features


6

North of the canyon, glacial features are apparent. Glaciation resulted in low, broad complexes of moraines in the region surrounding the OTP and the CTP. A moraine borders the Eagle River along the east side of the CTP. In localized areas, near the existing east groundwater extraction trench of the CTP, the moraine was eroded by the river which reworked the glacial deposits and left behind sand and gravel with few fines. The glacial deposits include unsorted glacial till consisting of gravelly silt and sand with cobbles and occasional boulders, glacial outwash comprised of sand and gravel, and occasional beds of silt and clay of lacustrine origin. Alluvial deposits include glacial sand and gravel with few fines. A unit of black lacustrine silts is located in Maloit Park and near the north side of the CTP suggesting that the area was once the site of a glacial lake probably formed when Cross Creek was temporarily dammed by terminal moraines.

Unconsolidated stream alluvium was deposited along all the major streams and occurs as lenses and discontinuous layers of fine sandy silts, silty clays, sandy gravels with silt and boulders and other various mixtures.

2.2.2 Soils, Vegetation and Climate

Native soils are generally of the Cryoborolls, Leighcan and Scout types (USDA, 1992-1993). These soil types occur in areas of shallow soil and exposed bedrock and typically have high runoff. Manmade Land type soils underlie many areas of the Site and are the result of past mining, remediation, construction and railroad activities.

Vegetation at the Site consists of subalpine and upper montane forests on the mountain slopes, characterized by forested stands of spruce-fir, aspen, Douglas-fir and lodgepole pine. The Eagle River valley supports a variety of plant communities including aspen woodland, lodgepole pine woodland, shrublands and various wetlands. Mountain meadows are commonly found intermixed within the area and are characterized by the dominance of forbs. Riparian zones are also present along the stream, primarily outside of the Belden canyon area.

The average daily annual temperature ranges from 21 to 55 degrees Fahrenheit and the normal annual precipitation is between 11 and 31 inches per year most of which is in the form of snow.

2.2.3 Surface Water Hydrology

The main water bodies located within the Site are the Eagle River, Rock Creek and Cross Creek. The headwaters of the Eagle River originate about 15 miles above Red Cliff. The Eagle River enters the Site from the south, flows north-northwest through the Site and continues westward until it joins the Colorado River at Dotsero. Approximately 0.7 mile downstream of Belden, Rock Creek, a tributary to the Eagle River, flows past the Bleakhouse portion of the mine workings and into the Eagle River. The Eagle River from Belden, past Rock Creek and the OTP is designated as Segment 5a in the water quality regulations (See Figure 2). Rock Creek enters the Site from the east as runoff from Battle Mountain. As Rock Creek flows past Waste Rock Pile 8 (WP-8), a separate channel has been constructed to collect contaminated water from WP-8 as part of the on-going remedial activities at the Site. Rock Creek then enters into a culvert, constructed as part of the


7

Figure 2 - Stream Segments and Surface Water Sampling Locations

Note: Sample locations “E” are on the Eagle River. “T” are tributary locations.


8

maintain separation from waste rock. The culvert discharges into an energy dissipation structure at the edge of the Eagle River, prior to discharging into the river.

Past Rock Creek, the Eagle River continues to flow northward. Eagle River Segment 5b begins at Tigiwon Road at the north end of Rex Flats (see Figure 2). The next tributary to enter the river is Two Elk Creek, which joins the river from the east. Two Elk is unimpacted by mining activities.

At the northern end of the Site, Cross Creek flows northeast through Maloit Park and discharges into the Eagle River via a culvert under Highway 24. Cross Creek originates in the Holy Cross Wilderness area to the west of the Site. As Cross Creek flows through the Maloit Park area adjacent to the CTP, water quality has been impacted by historic mining activities. This section of Cross Creek is designated as Segment 7b in the water quality regulations (see Figure 2).

Below the confluence with Cross Creek, the Eagle River flows through the town of Minturn, eventually joining Gore Creek. The section from Martin Creek (a small tributary at the south end of Minturn) to Gore Creek is designated as Segment 5c in the water quality regulations (see Figure 2).

Snow and snowmelt control the hydrologic regime at the Site. Eighty percent of the annual runoff in the Eagle River occurs from late May through July. Snowmelt on site can begin in February in the Belden area, or as late as May in the Rock Creek area, depending on spring temperatures. Figure 3 below shows the hydrograph for the Eagle River at the Site, 2008-2015.

Figure 3- Eagle River Hydrograph


9

2.2.4 Groundwater

Within the Site, groundwater flows through stream sediments, glacial deposits, mine waste, fractured bedrock, and mine workings. In the Belden canyon area, there is a limited alluvial groundwater system adjacent to the river. Groundwater flows through the fill material beneath the railroad tracks and then through the alluvium into the river, especially during the spring snow melt period.

At the mouth of Rock Creek, a similar, limited alluvial groundwater system exists. During the spring snow melt period discharge from the groundwater system can be significant.

At the OTP and CTP, the groundwater systems are more extensive within the glacial deposits. At the CTP two groundwater extraction trenches are operated as part of the on-going remedial activities.

2.3 Landownership and Use

After ceasing mining operations, New Jersey Zinc sold the mine and all related properties to Glenn Miller. Miller conveyed 1,400 acres of the property to the Battle Mountain Corporation, including the surface area of the town of Gilman and surface and minerals in an area north of Rock Creek. Miller subsequently declared bankruptcy (Engineering Science, 1985). Gulf + Western became the successor in interest to New Jersey Zinc; Gulf + Western became Paramount, Paramount became Viacom and Viacom became CBS Operations Inc. CBS Operations Inc., as the successor-in-interest to New Jersey Zinc (past operator of the Site), currently operates the remedy at the Site.

The property originally conveyed to Glenn Miller is now owned by a real estate investment company, Ginn-LA Battle One Ltd. LLP. There is ongoing litigation regarding current ownership of portions of the Site property. Current land uses on site are solely for remediation. Although the Site property is mostly privately-owned, has signage indicating it is private property and access is limited by several locked gates; there are numerous trespassers who hike, bike, fish, hunt and camp on the property.

The town of Minturn, located immediately downstream of the Site, obtains drinking water from Cross Creek, upstream from the Site. Downstream from the Site, the closest water supply is at the northern end of Minturn, at the U.S. Forest Service Visitor’s Center, which uses an alluvial well to supply water to the office and visitor center. Based on this well’s hydrologic connection to the Eagle River, the river is classified for water supply use. This well is 3.6 miles from the Site. Approximately 10 miles downstream from the Site, the Upper Eagle Regional Water Authority operates a surface water intake which uses water from the Eagle River as water supply for the area1. The immediate downstream Public Water Supplies do not have current Source Water Protection Plans (previously referred to as Wellhead Protection Plans) in place.

1 CDPHE does not provide water supply intake or public water supply well locations in documents that will be released to the public without the permission from the public water system.

Section 3 Applicable or Relevant and Appropriate Requirements

10


When selecting a remedy under CERCLA, the State and EPA identify their specific requirements that are applicable or relevant and appropriate (ARAR) for a particular site (40 CFR 300.405). The following regulations were considered when determining ARARs for arsenic in surface water at the Eagle Mine Site.

3.1 Regulation of Arsenic Pursuant to the Safe Drinking Water Act

With the authority granted by the Safe Drinking Water Act, EPA sets threshold levels for drinking water contaminants to protect human-health. These are called Maximum Contaminant Levels (MCLs), and they are enforceable at the point of use, such as a residential home. In developing MCLs, SDWA administrators consider laboratory detection limits, technical and economic feasibility, as well as the human-health risk data. For arsenic, the SDWA MCL is 10 µg/l. The arsenic MCL includes consideration of the technical and economic feasibility of drinking water providers to consistently achieve the MCL in their drinking water system. The MCL is over two orders of magnitude greater than the 0.02 µg/l CSWQS.

3.2 Regulation of Arsenic Pursuant to the Clean Water Act (for Surface Water)

With authority granted by the Clean Water Act, EPA and states set threshold levels or water quality standards for ambient water in rivers, streams and lakes to protect human-health from drinking water, ingesting fish that may bioaccumulate the pollutant and from cases where individuals are exposed to the pollutant both from drinking the water and eating the fish (Water+Fish). In Colorado, the standard-setting body is the Colorado Water Quality Control Commission or WQCC. Standards set by the WQCC are approved by the EPA under Section 303 of the Clean Water Act.

In developing these standards, EPA and States only consider the human-health risk data. Colorado has developed an approach to deriving protective values that is memorialized in WQCC Policy 96-2. These water quality standards are the threshold values for determining if a waterbody is “impaired” and are used to establish enforceable discharge limits in discharge permits.

3.2.1 Water Supply Standard

For the Water Supply (WS) arsenic water quality standard, the WQCC adopted a hybrid of the MCL and the human-health based standard, which is 0.02 to 10 µg/l. The hybrid approach assures that the in-stream water quality goal will be as close to purely health-based numbers as feasible, while assuring that no Colorado Discharge Permit System (CDPS) permit holder will be required to meet an effluent limit for chronic arsenic that is more stringent than the MCL of 10 µg/l.

3.2.2 Fish Ingestion Standard

For the Fish Ingestion (FI) arsenic water quality standard, the WQCC adopted the human-health based standard of 7.6 µg/l.


11

3.2.3 Water+Fish Standard

In 1991, the WQCC adopted Water+Fish (W+F) criteria as part of the basic standards for organic chemicals at section 31.11, Basic Standards and Methodologies for Surface Waters. In 1994 the WQCC added W+F criteria to the Metals Table (at section 31.16) which includes arsenic. During this time, the numeric value for a criterion was based on Policy 96-2 (the risk based maximum contaminant level goal, MCLG). This calculated value was often more stringent than the MCLs promulgated under the Safe Drinking Water Act. In August of 2005, the WQCC adopted revisions to the Basic Standards and Methodologies for Surface Waters (Regulation #31) and made a modification of the W+F table value. The W+F arsenic standard was changed from 0.018 to 0.02 µg/l. The 0.02 µg/l is a human-health risk-based value and was calculated using the procedures in WQCC Policy 96-2 with the following factors.

bioconcentration factor of 1 L/kg, fish intake of 0.0175 kg/day, and that 30% of arsenic in fish tissue is inorganic cancer slope of 1.75 kg-day/mg, cancer risk of 10-6 (one in one million) body weight of 70 kg, and water consumption of 2 L/day.

Following their inclusion in WQCC Regulation 31.16 Table III in 2005, these criteria were added specifically to the individual river segments to which they apply in the basin hearings. In previous years, the values had resided only in Regulation 31 (Basic Standards for Surface Water).

3.3 ARARs for the Eagle Mine Site

State adopted water quality standards approved by EPA pursuant to the Clean Water Act § 303(c)(3) are ARARs under CERCLA § 121(d)(2)(A) and the NCP §300.430(e)(2)(i)(E). These standards are published in the State of Colorado’s Basic Standards and Methodologies for Surface Waters (Regulation 31) or the tables for each river basin. The Eagle River Basin standards are listed in Regulation 33.

The remedial action goals for surface water identified in the 1993 ROD were based on Regulation 31, specifically chemical-specific acute and chronic standards for zinc, cadmium, copper, lead and silver, calculated using Table Value Standard equations at a hardness of 100 mg/l. The 1996 Consent Decree between Gulf + Western, EPA and the State of Colorado set forth a process to modify the surface water standards using a biological approach. The biological approach resulted in modifications to the Colorado surface water standards that were promulgated by the WQCC in 2008 for copper, cadmium and zinc. (By 2008 water quality monitoring data had shown that lead and silver were not detected at the Site, so the standards were not changed for these parameters.) In 2008, arsenic had not been recognized as a COC in surface water because sampling had not yet been conducted using a lower detection limit. However, the 0.02 µg/l W+F standard for arsenic was added to Regulation 33 tables for all segments with Class I Aquatic Life Use classification and


12

Water Supply Use classification, including the Eagle River segments 5a, 5b, 5c and 7b, during same 2008 WQCC hearing.

The currently applicable surface water standards for the Eagle River segments at the Site are shown in the Regulation 33 Table 1 below. The chronic arsenic standard highlighted in Table 1, is the W+F value of 0.02 µg/l total recoverable (Trec) discussed in Section 3.3 above. The Temporary Modification is a temporary reprieve from the standard, set to expire in December 31, 2021 and it was applied to the Eagle River Segment 5b (see Segment 5b in Table 1 below) because the Eagle Mine Water Treatment Plant discharges to this segment under a discharge permit (see Section 8.2 for further discussion of the Temporary Modification.). The temporary standard relaxes the arsenic criteria to “current condition,” meaning that the arsenic standard under the Temporary Modification is the ambient condition or current concentration in the stream. For the remaining segments at the Eagle Mine Site (5a, 5c and 7b) the 0.02 µg/l standard is still in effect and has not been modified by the WQCC. Temporary Modifications may not be protective of all uses, especially when set at ambient concentrations.


13

Table 1 - Excerpt from Regulation 33 (Segments 5a, 5b, 5c and 7b are within the Site)

STREAM CLASSIFICATIONS and WATER QUALITY STANDARDS REGION:12 BASIN: Eagle River

Desig Classifications

NUMERIC STANDARDS TEMPORARY MODIFICATIONS

AND QUALIFIERS

Stream Segment Description

PHYSICAL and

BIOLOGICAL

INORGANIC mg/l

METALS ug/l

1. All tributaries and wetlands to the Eagle River system within the Gore Range - Eagles Nest and Holy Cross Wilderness Area.

OW1

Aq Life Cold 1 Recreation E Water Supply Agriculture

T=TVS(CS-I)oC D.O.=6.0 mg/l D.O.(sp)=7.0 mg/l pH=6.5-9.0 E.Coli=126/100ml Chla=150 mg/m2

NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot)

As(ac)=340 As(ch)=0.02(Trec) Cd(ac)=TVS(tr) Cd(ch)=TVS CrIII(ac)=50(Trec) CrIII(ch)=TVS CrVI(ac/ch)=TVS Cu(ac/ch)=TVS

Fe(ch)=WS(dis) Fe(ch)=1000(Trec) Pb(ac/ch)=TVS Mn(ch)=WS(dis) Mn(ac/ch)=TVS Hg(ch)=0.01(tot) Mo(ch)=160(Trec)

Ni(ac/ch)=TVS Se(ac/ch)=TVS Ag(ac)=TVS Ag(ch)=TVS(tr) Zn(ac/ch)=TVS Zn(ch)=TVS(sc)

Temporary modification: As(ch)=hybrid Expiration date of 12/31/21.

1 Consistent with the provisions of section 25-8-104 C.R.S. the OW designation shall not apply with respect to the Homestake Water Project of the Cities of Aurora and Colorado Springs.

2. Mainstem of the Eagle River from the source to the compressor house bridge at Belden.


T=TVS(CS-I)oC D.O.=6.0 mg/l D.O.(sp)=7.0 mg/l Ph=6.5-9.0 E.Coli=126/100ml Chla=150 mg/m2 C

NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot) C




3. All tributaries to the Eagle River, including wetlands, from the source to the compressor house bridge at Belden, except for the specific listing in Segment 4 and those waters included in Segment 1.



NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot)





4. Mainstem of Homestake Creek from the confluence of the East Fork to the confluence with the Eagle River.



NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot)





5a Mainstem of the Eagle River from the compressor house bridge at Belden to a point immediately above the Highway 24 Bridge near Tigiwon Road.

9/30/00 Baseline does not apply


T=TVS(CS-I)oC D.O.=6.0 mg/l D.O.(sp)=7.0 mg/l pH=6.5-9.0 E.Coli=126/100ml

NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

As(ac)=340 As(ch)=0.02(Trec) Cd(ac)=TVS(tr) Cd(ch)=(1.101672-[ln(hardness)*(0.041838)])* e(0.7998 [ln

(hardness)]-3.1725)

CrIII(ac)=50(Trec) CrIII(ch)=TVS CrVI(ac/ch)=TVS Cu(ac)=0.96*e 0.9801[ln(hardness)] –

1.1073 Cu(ch)=0.96*e 0.5897[ln(hardness)] –

0.0053


Ni(ac/ch)=TVS Se(ac/ch)=TVS Ag(ac)=TVS Ag(ch)=TVS(tr) Zn(ac) = 0.978*e 0.8537[ln(hardness)]+2.1302 Zn(ch) = 0.986*e 0.8537[ln(hardness)]+1.9593


14

Table 1 – (continued) REGION:12 BASIN: Eagle River Desig Classifications

NUMERIC STANDARDS TEMPORARY MODIFICATIONS

AND QUALIFIERS

Stream Segment Description

PHYSICAL and

BIOLOGICAL

INORGANIC mg/l

METALS ug/l

5b. Mainstem of the Eagle River from a point immediately above the Highway 24 Bridge near Tigiwon Road to a point immediately above the confluence with Martin Creek.




NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS


(hardness)]-3.1725)

CrIII(ac)=50(Trec) CrIII(ch)=TVS CrVI(ac/ch)=TVS Cu(ac) = 0.96*e 0.9801[ln(hardness)]-1.5865

Cu(ch) = 0.96*e 0.5897[ln(hardness)]-0.4845


Ni(ac/ch)=TVS Se(ac/ch)=TVS Ag(ac)=TVS Ag(ch)=TVS(tr) January 1 through April 30 Zn(ac) = 0.978*e 0.8537[ln(hardness)]+2.1302

Zn(ch) = 0.986*e 0.8537[ln(hardness)]+1.9593

May 1 through December 31 Zn(ac) = 0.978*e

0.8537[ln(hardness)]+1.4189 Zn(ch) = 0.986*e 0.8537[ln(hardness)]+1.2481


5c. Mainstem of the Eagle River from a point immediately above Martin Creek to a point immediately above the confluence with Gore Creek.




NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS


(hardness)]-3.1725) CrIII(ac)=50(Trec) CrIII(ch)=TVS CrVI(ac/ch)=TVS Cu(ac) = 0.96*e 0.9801[ln(hardness)]-1.5865



Ni(ac/ch)=TVS Se(ac/ch)=TVS Ag(ac)=TVS Ag(ch)=TVS(tr) Zn(ac) = 0.978*e


6. All tributaries to the Eagle River, including all wetlands, from the compressor house bridge at Belden to a point immediately below the confluence with Lake Creek, except for the specific listings in Segments 1, 7a, 7b, and 8.



NH 3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot)





7a. Mainstem of Cross Creek from the source to a point immediately below the Minturn Middle School, except for those waters included in Segment 1.



NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot)



Ni(ac/ch)=TVS Se(ac/ch)=TVS Ag(ch)=TVS Ag(ch)=TVS(tr) Zn(ac/ch)=TVS Zn(ch)=TVS(sc)

7b. Mainstem of Cross Creek from a point immediately below the Minturn Middle School to the confluence with the Eagle River, except for those waters included in Segment 1.




NH3(ac/ch)=TVS

Cl2(ac)=0.019

Cl2

(ch)=0.011

CN=0.005

S=0.002 B=0.75 NO2=0.05

NO3=10

Cl=250 SO4=WS

P=110 ug/l (tot)


(hardness)]-3.1725) CrIII(ac)=50(Trec) CrIII(ch)=TVS CrVI(ac/ch)=TVS Cu(ac) = 0.96*e 0.9801[ln(hardness)]-1.5865



Ni(ac/ch)=TVS Se(ac/ch)=TVS Ag(ac)=TVS Ag(ch)=TVS(tr) January 1 through April 30 Zn(ac) = 0.978*e 0.8537[ln(hardness)]+2.1302

Zn(ch) = 0.986*e 0.8537[ln(hardness)]+1.9593

May 1 through December 31 Zn(ac) = 0.978*e


Section 4 Previous Decisions

15

Section 4 Previous Decisions

EPA listed the Site on the National Priorities List in 1986. Cleanup at the Site began in 1988 under a Consent Decree/Remedial Action Plan (CD/RAP) between the State of Colorado and the responsible party. EPA established three operable units (OUs) at the Site. OU1 was established to control the transport of metals from sources of mine waste that impact the Eagle River and groundwater resources. EPA issued the OU1 ROD in 1993. The OU1 ROD resulted in additional remediation, above and beyond the state-mandated cleanup, under a three-party Consent Decree/Statement of Work (CD/SOW). OU2 was established to evaluate potential human health risks at the Site. OU3 was established for a private residential development proposed for the OU1 area, which would require additional cleanup actions beyond those selected in the OU1 ROD. The OU2 ROD was issued in 1998. The OU3 ROD has not yet been issued.

The 1993 OU1 ROD did not include an ARAR for arsenic because arsenic was not detected in the Eagle River, using the laboratory methods in effect at the time. Therefore, arsenic was not included in the routine surface water monitoring program at the Site. Sampling conducted by the PRP at the Site in 2012 and 2013 confirmed that arsenic is present at the Site in concentrations that exceed the current CSWQS of 0.02 µg/l. EPA and the State of Colorado then recognized arsenic as a COC for surface water and the 0.02 µg/l CSWQS as a potential ARAR for the Site.

Section 5 Remedial Actions Conducted

16


Cleanup at the Site began in 1988 under the CD/RAP. Additional cleanup under the CD/SOW occurred in 1996. EPA declared construction of the OU1 remedy complete in 2001. Operation and maintenance of remediation systems, including water treatment, for OU1 continues today, and is the responsibility of the PRP at the Site, CBS Operations, Inc. (CBS).

Remediation activities for OU1 included removal of roaster wastes; removal of mill tailings from the OTP, Rex Flats and Maloit Park; construction of a water treatment plant (WTP) and a lined sludge pond; capture and treatment of groundwater; capping the CTP; CTP erosion and settlement monitoring; ground and surface water monitoring; and revegetation of disturbed areas.

The CTP contains contaminated materials that were removed from other areas within the Site during remediation, including Roaster Wastes, and tailings from the OTP, Rex Flats and Maloit Park. The CTP was reshaped such that side slopes were 5H:1V. The entire pile was covered with a multi-layer cap, consisting of either a lower permeability zone (tailings slimes) or a Geo-composite clay liner; an erosion layer (24 inches); and a 12- to 24-inch growth layer (CDPHE, 2005).

The WTP was constructed in 1991. Two lined surge ponds were constructed on top of the CTP adjacent to the WTP to hold water prior to treatment. Both ponds are lined with a flexible membrane liner. Two groundwater extraction trenches were constructed on the north and east sides of the CTP. Water collected from these trenches (approximately 130 gallons per minute or gpm) is pumped to the surge ponds (NewFields, 2015a).

Waste rock capping or removal was not specifically required as part of the original cleanup agreements. The CD/SOW required a detailed study of loading from waste rock piles. Each waste rock pile was given an identifying number (e.g. WP-8) and samples were collected for measurement of total metals content and acid generation potential. The study identified the waste rock piles with the greatest potential to generate acid mine drainage. Surface water controls were constructed to route runoff away from several waste rock piles. WP-8 was identified as the most problematic of the waste rock piles. Runoff from WP-8 contained high metals concentrations. As a result, two separate systems were constructed to collect contaminated water from WP‐8 and route that water to the WTP. The WP-8 collection systems operate primarily during the snowmelt/runoff season, but also operate during rainfall events. In addition, under the CD/RAP, Rock Creek was routed through a 660-foot long culvert to prevent further erosion of the toe of WP-11. In 1995, the culvert was extended another 800 feet.

The mine pool is the single largest source of dissolved metals at the Site. Water from the mine pool is treated at the WTP on a year‐round basis in order to control the water level in the mine pool. If the pool elevation exceeds 8,520 feet (above sea level), seeps will develop in the Rock Creek canyon that could contribute additional metals to the Eagle River. Mine pool seepage at pool levels less than 8,520 feet has little effect on the river. The mine pool has been maintained at elevations less than 8,510 feet since 2010 and since October of 2012 has been below 8,470 feet.


17

In-flow into the mine pool occurs on the 19 Level of the mine via the 19-5-E-3 exploratory drift. It was estimated that 200 gpm or more of clean groundwater inflows into the mine continuously in this drift that connects the Eagle Mine workings to the Turkey Creek and Willow Creek watershed near Red Cliff. To intercept flow in the 19-5-E-3 drift, a 960-foot well (Liberty #5) was installed in the drift in July 1998. In September 1999, EPA issued an ESD describing EPA’s decision regarding the mine pool component of the remedy for the Site. The ESD required the PRP to install and maintain a pumping system at the Liberty Well. The Liberty Well remains a critical component of the on-going remediation system at the Site. Currently the Liberty Well pumps at a rate of 150 gpm, diverting clean groundwater from entering the mine workings and preventing this water from becoming contaminated.

On-going remediation includes collection and treatment of mining-impacted water at the WTP. Figure 4 shows a diagram of the collection and conveyance systems at the Site. On average around 220 gpm of water from the Bleakhouse Mine workings and another 30 gpm from the Tip Top/Ben Butler mine workings in Belden are conveyed via pipeline to the surge ponds at the WTP. The WTP operates in the range of 200 to 300 gpm averaging a 250 gpm annual treatment rate. Figure 5 is a schematic of the water treatment process used at the Site. The WTP uses lime to raise the water pH of the influent, and a polymer is added to flocculate and settle out the solids. The solids are collected and processed using a sludge press system. Acid is added to the effluent to neutralize the pH prior to discharging to the Eagle River. The treated water is discharged under the provisions of a CDPS permit. The sludge is disposed in the lined sludge cell located on the CTP. Table 2 below shows a comparison between the influent and effluent water quality at the WTP.

Table 2 - WTP Influent/Effluent Concentrations

Average Influent Concentration

(µg/l)

Average Effluent Concentration

(µg/l)

Arsenic 31.63 1.04

Cadmium 76.25 0.654

Copper 167.56 4.0

Zinc 33,080 48.58

Note: Arsenic data reported from Environ, 2010 through 8/2014. All other contaminants based on 2014 data only. PQL for Arsenic is 1 µg/l and detection limit for copper is 4 µg/l.


18

Figure 4 - Eagle Mine Seepage Collection and Conveyance Systems


19

Figure 5 - Eagle Mine Water Treatment Plant Schematic

Section 6 Existing Data and Analysis

20


As a result of completed and ongoing remediation at the Site, water quality in the Eagle River has improved and now meets water quality standards during most of the year. However, in March and April, as the snow melts at the Site, copper, cadmium, and zinc concentrations are higher, and often exceed water quality standards. Arsenic exceeds standards in all sampling periods, including March and April, due to the fact that the standard is so low (0.02 µg/l).

At EPA’s request, CBS prepared a Focused Feasibility Study (FFS) (NewFields 2013) that presented and evaluated several remedial alternatives that could be implemented to attain the water quality standards for cadmium, copper and zinc during March and April. More recently, EPA requested that CBS prepare a FFS addendum evaluating arsenic in surface water. Additional data was collected to support the analysis necessary for the FFS addendum (NewFields 2015b). Table 3 below shows the arsenic concentration in the Eagle River, Rock Creek and Cross Creek. (See Figure 2 on Page 7 for sampling locations.)

Table 3 - Arsenic Concentration in the Eagle River (in µg/l)

Sample Location

Date E- 3 E-10 E-12A E-15 E-22

T-10 Rock

Creek

T-18 Cross Creek

10/18/12 0.36 0.26 0.36 0.23 0.43 2.3 ND

3/12/13 NS 0.58 0.72 0.35 0.5 1.8 ND

3/22/13 0.2 0.86 0.65 0.46 0.43 1.5 0.2

4/5/13 0.25 0.41 0.45 0.49 0.56 3.1 0.27

4/19/13 ND 0.34 0.52 0.49 0.44 2 ND

5/3/13 0.34 0.59 0.64 0.44 0.43 2 ND

9/30/13 ND ND 0.2 ND ND 2.6 ND

3/20/14 ND 0.4 0.29 0.31 0.31 1.9 0.51

4/3/14 ND 0.28 0.29 0.2 0.26 1.7 ND

4/17/14 0.35 0.46 0.92 0.47 0.45 1.4 0.25

9/24/14 0.22 ND 0.23 ND ND 2.5 ND

3/13/15 0.2 0.25 0.31 0.25 0.31 1.4 0.14

3/27/15 0.16 0.21 0.23 0.25 0.26 1.4 0.14

4/13/15 0.31 0.26 0.31 0.32 0.29 1 0.16

4/27/15 0.21 0.2 0.32 0.21 0.3 1.1 0.2

Notes: ND = Not detected at a detection limit of 0.2 µg/l. NS = Not sampled Values in Bold Italics are detections between the MDL and the PQL.

Figure 6 below displays the arsenic data graphically in reference to the CSWQS. Note that all samples exceed the CSWQS, including the upstream, or background samples, collected


21

at monitoring location E-3. Note also that the majority of the data points are below the Practical Quantification Limit (PQL) of 1 µg/l specified by the WQCD.

Figure 6 - Arsenic in the Eagle River and Tributaries

The highest concentrations of arsenic are detected in Rock Creek; however, the flows in Rock Creek are relatively low in comparison to the mainstem of the Eagle River. Table 4, below, shows the increases in arsenic concentration that occurred between monitoring locations. The first reach, E-3 to E-10, receives runoff and groundwater from the mine and mine waste in Belden. When compared to the other reaches, this reach had the highest increase overall, shown in yellow highlight of 0.66 µg/l and also the highest overall increase based on the averages.

The second reach, from E-10 to E-12A, includes the Rock Creek inflow. The largest increase occurred during the sampling event on 4/17/14, when the concentration in the Eagle River increased by 0.46 µg/l. Even though the Rock Creek concentrations appear dramatically higher in the graph (Figure 6) the actual impact on the river is less than the

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

E- 3 E-10 E-12A E-15 E-22 T-10 T-18

Ars

en

ic (

ug/

l)

Sample Location

10/18/12

3/12/13

3/22/13

4/5/13

4/19/13

5/3/13

9/30/13

3/20/14

4/3/14

4/17/14

9/24/14

3/13/15

3/27/15

4/13/15

4/27/15

CSWQS

PQL

Upstream Downstream

Tributaries


22

impact from Belden in the E-3 to E-10 reach, where the average increase is almost twice as high (0.12 µg/l) as the increase in the reach that includes the Rock Creek inflow (0.07 µg/l).

Table 4 - Change in Arsenic Concentration in the Eagle River

Between Sampling Locations (in µg/l)

Change in Concentration Between Locations

Date E-3 to E-10 E-10 to E-12A E-12A to E-15 E-15 to E-22

Reach Description Belden

Rock Creek to Old Tailings Pile

Old Tailings Pile to Cross Creek

Cross Creek to Below Minturn

10/18/12 -0.10 0.10 -0.13 0.20

3/12/13 0.14 -0.37 0.15

3/22/13 0.66 -0.21 -0.19 -0.03

4/5/13 0.16 0.04 0.04 0.07

4/19/13 0.18 -0.03 -0.05

5/3/13 0.25 0.05 -0.20 -0.01

9/30/13

3/20/14 -0.11 0.02 0.00

4/3/14 0.01 -0.09 0.06

4/17/14 0.11 0.46 -0.45 -0.02

9/24/14

3/13/15 0.05 0.06 -0.06 0.06

3/27/15 0.05 0.02 0.02 0.01

4/13/15 -0.05 0.05 0.01 -0.03

4/27/15 -0.01 0.12 -0.11 0.09

Average 0.12 0.07 -0.12 0.04

Note: Highest value for each reach highlighted in Yellow.

The third reach, from E-12A to E-15 encompasses Segment 5b and the CTP. The majority of the changes in arsenic concentration in this reach are negative, meaning that the concentrations decreased. The clean tributary, Two Elk Creek enters the Eagle River in the reach. Also, there are no known sources of arsenic that are impacting this reach. The historic sources impacting this reach have been remediated and the groundwater beneath the CTP is captured and treated at the WTP. The fourth reach, from E-15 to E-22 is downstream from the Eagle Mine Site and includes the town of Minturn. There are measured increases in arsenic in this reach during some of the sampling events, which most likely are not attributable to the Site. This reach includes the lower portion of Segment 5b and Segment 5c. The term “metals loading” is commonly used to identify and quantify the input from mining‐related sources to surface water. Metals loading is expressed in units of pounds of metals per day (lbs/day). Metal loads are calculated using the following formulas


23

depending on the units of the measured flow.

Load (lbs/day) = flow (cfs) x metal concentration (µg/L) x 0.0054 (units conversion factor) Load (lbs/day) = flow (gpm) x metal concentration (µg/L) x 0.0000116 (units conversion factor)

Load calculations are not exact and should be regarded as estimates. Load estimates are dependent upon a number of assumptions and involve uncertainty. Inherent in each computation of load is the calculated error associated with the measurement of metal concentration and stream flow (up to ±25 percent analytical error and ±10 percent flow error). In the analysis of loading by stream segment, it is assumed the computed load incorporates these errors and, as such, retains a compounded error of at least ±20 percent. Table 5 below looks at the same data from Table 4, but now takes the next step to incorporate flow and estimate the arsenic load entering the river in each reach of the river, between sampling locations.


24

Table 5 - Arsenic Load Estimates by River Reach

Arsenic Loading (lbs/day)

Date E-3 E-3 to E-10 E-10 to E-12A E-12A to E-15 E-15 to E-22 T-10

Reach Description Background Belden

Rock Creek to Old Tailings

Pile

Old Tailings Pile to Cross

Creek

Cross Creek to Below Minturn Rock Creek

10/18/12 0.046 -0.006 0.012 -0.008 0.039 0.002

3/12/13 0.037 0.002 -0.027 0.005 0.001

3/22/13 0.011 0.052 -0.021 -0.018 -0.002 0.001

4/5/13 0.045 0.042 0.005 0.053 0.021 0.003

4/19/13 0.064 0.029 0.030 -0.012 0.005

5/3/13 0.211 0.208 0.031 0.060 -0.012 0.005

9/30/13 0.006

3/20/14 0.071 -0.022 0.023 0.000 0.002

4/3/14 0.060 0.000 0.000 0.018 0.013

4/17/14 0.239 0.120 0.352 -0.109 -0.026 0.008

9/24/14 0.070 0.006

3/13/15 0.038 0.018 0.011 0.012 0.019 0.004

3/27/15 0.053 0.027 0.005 0.060 0.004 0.007

4/13/15 0.191 -0.008 0.117 0.252 0.145 0.004

4/27/15 0.125 0.011 0.075 0.010 0.092 0.004

Average 0.103 0.053 0.046 0.026 0.022 0.005

Note: Highest value for each reach highlighted in Yellow.

In Table 5 the arsenic loads for each reach are calculated. The average and maximum load (shown highlighted in yellow) are presented. Segment 2, the upstream segment, represented by E-3, has the highest average load of 0.103 lbs/day. In a pattern that is similar to the concentration data presented in Table 4, the Segment 5a loads from E-3 to E-12A are higher than the loads in Segments 5b or 5c. Segments 5b and 5c have similar average loads to one another, of around 0.02 lbs/day. Note that the load from Rock Creek (the last column in Table 5) is low, on average less than 0.005 lbs/day. The FFS presents a detailed analysis of metals loading based on a large set of concentration and stream flow data. As mentioned previously, the FFS was developed to address copper, cadmium and zinc. However, many of the conclusions of the FFS appear to be relevant to arsenic as well. Significant conclusions of the FFS include:

There is a relationship between snowpack and water quality. In years with higher snowpack, loading increases. The data set for arsenic is limited, but the same trend most likely applies to arsenic.

Upstream sources in Segment 2 of the Eagle River contribute to the overall load in the Eagle River. This background load is important to consider because the contribution from upstream is one of the main factors making it technically impracticable to attain the arsenic standard.


25

For those areas where load increases were identified, the FFS used information

from the many studies completed over the past 25 years to identify potential mine‐related sources causing the increase. The primary sources investigated were waste rock piles and groundwater. Metals load contribution from the groundwater sources can be estimated directly through sampling of the groundwater. Estimating the load from waste rock is more complicated, as direct runoff from waste rock has not been observed as a primary loading source.

Groundwater sources were sampled for arsenic to see if they are contributing arsenic to the Eagle River. Data are presented below in Table 6. Note the high “first flush” concentration of arsenic in sample BTS-1 of 183 µg/l. Appendix A contains additional, more detailed, information regarding the sampling of the arsenic sources at the Site.

Table 6 - Total Arsenic in Groundwater Samples (concentration in µg/l)

BTS-1 (Belden

Groundwater)

BW-9R (Belden

Groundwater)

EDS-3 (Rock Creek

Groundwater)

Mill Level (Belden

Groundwater) 1/15/2015 No Sample No Sample No Sample 1.2 3/7/2015 183 2.6 3.2 No Sample

3/26/2015 No Sample No Sample No Sample 1.6 3/19/2015 32.6 2.2 1.5 No Sample 4/7/2015 18.3 2.7 1.3 No Sample

Note: Highest value highlighted in Yellow.

The data from Table 6 were then used to estimate the actual load that these sources may contribute to the Eagle River. The results of this analysis are presented as an estimated load for each source in Table 7. From this analysis, Belden groundwater is determined to be the primary loading source, at 0.033 lbs/day of arsenic. Rock Creek waste rock piles are the largest secondary source. Details of the calculation method can be found in the FFS (NewFields, 2013) as the same methodologies were used for zinc loading estimates in the FFS.


26

Table 7 - Arsenic Source Load Estimates, Segment 5a

Sources Sample Sites and Method Estimated

Load (lbs/day)

Method Notes and FFS Report

Reference

Belden groundwater

Sum of Load from Belden Wells BW-10, BW-9R, and BTS-1. Average of sampled events. (BW-10 was sampled in Spring of 2014)

0.033

Section 4.2.1, used a weighted average arsenic concentration from 3 wells producing a total of 21 gpm

Rock Creek groundwater

EDS‐3 Well, Average of 3 sampled events

0.00023 Section 4.4, used 10 gpm

Rock Creek waste rock piles

Rock Creek load at T‐10 less background load at T-10A, range of 4 sampled events

0.004-0.017 Section 4.3.2.2 and 4.4

OTP/Rex Flats OTP South Ditch Seep, 2 sampled Events

No Flow available to calculate load

Section 4.5, Periodic, only when flowing.

Mill Level Average of 2 sampled events from underground Mill Level, Belden

0.00016 Section 4.1.3, Used 10 gpm; Periodic, only when pumping

Note: Highest value highlighted in Yellow.

The load estimates demonstrate that the groundwater in Belden is the primary source of arsenic, especially during the first flush of the snowmelt period (see the 3/7/2015 sample from BTS-1). It is important to note that the FFS concluded that groundwater in Belden is also the primary source contributing copper, cadmium and zinc to the Eagle River.

Section 7 Conceptual Site Model

27

Section 7 Conceptual Site Model

Water from melting snow infiltrates into mine waste along the railroad grade in Belden and Rock Creek. As the water table rises, groundwater flows into the Eagle River. This groundwater is highly concentrated with metals leached from the mine waste through which the groundwater flows. This highly concentrated groundwater reaches the Eagle River while the river is still in a low-flow status, prior to snow melt in the high county that occurs during spring runoff. As a result, with little available flow in the river for dilution, the concentration of metals in the river goes up and the water quality standards are exceeded. Once the flow in the river increases due to spring runoff, groundwater impacts are overwhelmed by the high flows and concentrations of metals decrease. As snowmelt at the Site dissipates, water levels in the groundwater systems in Belden and Rock Creek decline and very little groundwater discharge and very little metals loading to the river occurs during the remainder of the year.

Due to the very low regulatory limit set for arsenic, and the ubiquitous occurrence of arsenic in the area, the CSWQS is exceeded year-round, regardless of the flow conditions. In fact, upstream concentrations of arsenic entering the Site exceed the CSWQS year-round. In addition, a pulse of arsenic-laden water enters the river in Belden from groundwater during the snow-melt period.

Section 8 Evaluation of Restoration Potential

28


Arsenic is ubiquitous in the environment and especially in mineralized areas in Colorado. The combination of a very low regulatory limit and the site-specific conditions presented in the CSM significantly limit the restoration potential for arsenic in surface water at the Site. In addition, technical considerations, including the lack of effective treatment technologies, also impact restoration potential.

8.1 Primary and Secondary Sources

The primary on-site source of arsenic is groundwater in the Belden area. All other on-site sources have estimated loads that are at least an order of magnitude lower than groundwater in Belden and all on-site sources have lower estimated loads than the upstream, background load in the Eagle River, which averages 0.1 lbs/day. Groundwater in Belden and Rock Creek are currently being evaluated for additional remediation under the FFS.

8.2 Treatment Technologies

As the Water+Fish criteria were added to individual stream segments by the WQCC, it became apparent that existing water treatment plants could not remove arsenic to levels that would result in attainment of the 0.02 µg/l standard. As a result, in April of 2013, the WQCC held a special hearing to adopt state-wide Temporary Modifications to the W+F arsenic standards. The Temporary Modifications were based on the following factors:

1) Natural Contributions: Many of Colorado’s waters have naturally occurring arsenic near or above the W+F standard. There is little or no dilution available to moderate the effect of such a low water quality standard.

2) Technical Infeasibility: CDPS permit holders and the WQCD agreed that in many cases, it is technically infeasible to attain effluent quality of 0.02 µg/l. The wide range of pollutant mixtures (from contaminated groundwater, uncontaminated but arsenic-rich groundwater, to typical domestic wastewater) also complicates the conclusions about technical feasibility. Most of the feasibility work has been done on drinking water systems that start with relatively clean water.

3) Laboratory Detection: The WQCD’s Practical Quantification Limit (PQL) for arsenic has been set at 1.0 µg/l, which is two orders of magnitude higher than the standard. A PQL is the minimum concentration of an analyte that can be measured with a high degree of confidence that the analyte is present at or above that concentration. The PQL is used by the WQCD as the compliance threshold for CDPS permit holders when regulating arsenic. Unless CDPS permit holders are using very sensitive methods that differ from the WQCD’s PQL, they will not know whether the levels of arsenic in their effluent approach the standard.

4) Perceived Unfairness: There has been considerable debate about whether water quality standards for parameters with MCLs should be based on the MCLs or purely health-based numbers. The arguments for MCLs focused on whether it is reasonable to require in-stream standards (and potentially wastewater treatment) to a level cleaner than allowed for drinking water. The arguments for health-based standards focused on maximizing human health protection, putting the clean-up burden on pollution sources, and the fact


29

that wherever dilution is available end-of-pipe effluent limits would be less restrictive than the standard.

At the April 2013 hearing, the WQCC adopted “hybrid” temporary modifications intended to satisfy two different scenarios: new discharges (commencing after 6/1/2012) and existing discharges (existing before 6/1/2013). For new discharges, the temporary modification for chronic arsenic is set at 3.0 µg/l. For existing discharges the temporary modification is set at “current condition”.

The WQCC intended that, when implementing the temporary modification of “current condition” in a CDPS permit, the WQCD will assess the current effluent quality, recognizing that it changes over time due to variability in treatment facility removal efficiency and influent loading from natural or anthropogenic sources. Maintaining the current condition will include maintaining total arsenic loading to a treatment facility from arsenic contributors at the levels existing on the effective date of the temporary modification.

When the WQCD was considering the Temporary Modifications for the W+F use segments, information regarding current treatment technology for arsenic was compiled and provided as evidence for the April 2013 hearing. The WQCD concluded that there is no known treatment technology that can treat wastewater to an arsenic level of 0.02 µg/l at a reasonable economic level (WQCD, 2013). The WQCD contended that all CDPS permitted facilities that discharge to W+F use segments would have chronic arsenic water quality-based effluent limit compliance problems with the current chronic arsenic W+F use standard of 0.02 µg/l. In attempting to determine a level that current-day treatment technology can reasonably and feasibly achieve, the WQCD reviewed national studies, EPA guidance documents, and Colorado-specific domestic wastewater treatment plant influent and effluent arsenic data. The WQCD found that Adsorptive Media (AM) and Ion Exchange (IX) treatment technologies can provide a consistent level of arsenic treatment and are considered the best reasonable alternatives for providing arsenic removals to technologically feasible arsenic treatment levels. The WQCD found that a technology-based limit of 2 µg/L would be readily achievable utilizing AM and IX technology.

At the Eagle Mine, the WTP has been required to monitor for arsenic in the effluent at a PQL of 1 µg/l since 2008. The WTP uses a conventional pH adjustment and settling water treatment technology. Arsenic concentrations in the influent to the WTP range from 5.6 µg/l to 97.5 µg/l. Effluent monitoring data indicate that the WTP is effective at arsenic removal, often with concentrations reported at or below the PQL of 1 µg/l (See Table 2, Page 17).

8.3 Background Concentrations in the Eagle River

Background concentrations in the Eagle River have been measured by CBS (see data for sampling location E-3 on Table 3, Page 20). The reported data range is from 0.20 µg/l to 0.36 µg/l with the 85th percentile at 0.35 µg/l. (The 85th percentile is the standard statistic used by the WQCD to calculate an ambient concentration to compare to a chronic water quality standard.) All of the reported values, and correspondingly the 85th percentile, exceed the CSWQS of 0.02µg/l. Also note that all of the data points are below the PQL of 1 µg /l. Therefore, it could be argued a more “reliable” estimate of background is equivalent to the PQL and is 1 µg/l.


30

8.4 Restoration Potential and Restoration Timeframe

Because no analytical methods exist that can reliably measure concentrations of arsenic in surface water at a concentration of 0.02 µg/l, background concentrations are greater than the 0.02 µg/l standard and no water treatment technology currently exists that can meet an effluent concentration of 0.02 µg/l, it is necessary to waive the 0.02 µg/l ARAR. In addition, for these same reasons, it is also impossible to predict a timeframe for cleanup to attain the 0.02 µg/l standard.

Section 9 Alternative Remedial Strategy

31


This TI Evaluation Report has presented evidence that it is impossible to measure arsenic to levels as low as the current CSWQS and that the background water quality exceeds the standard. However, additional remediation is still planned at the Site that will further reduce metals loading to the river and also will further reduce arsenic concentrations. The alternative remedial strategy has 2 components, first the alternate remedial goal and secondly the additional remedial alternatives that are being considered under the FFS.

9.1 Alternate Remedial Goal for Arsenic

The general Remedial Action Objective set forth in the 1993 ROD of “Improve the quality of water in the Eagle River to support Class 1 aquatic life use” has not changed. However, the 1993 ROD did not include an ARAR for arsenic because arsenic had not been detected in surface water using the analytical methods employed at the time. A potential ARAR for arsenic has been identified by the agencies, however, it is technically impracticable to meet that standard. As part of the Alternative Remedial Strategy, EPA and CDPHE are proposing an Alternate Remedial Goal for arsenic of 3 µg /l based on two findings of fact. First, 3 µg /l is the value selected by the WQCC for the Temporary Modification for new discharges (refer to Section 8.2). If a new water treatment plant were to apply for a permit to discharge into the Eagle River, the WQCC’s Temporary Modification for new discharges would apply and that discharge would be granted an effluent limit of 3 µg /l.

Second, based on a risk evaluation for the Site, prepared by EPA Toxicologist Dr. Susan Griffin (see Appendix B), assuming a risk scenario of consuming water and fish from the Eagle River without prior treatment, 3 µg /l equates to 5 x10-5 lifetime cancer risk. This goal is protective of human health and the environment, is within the acceptable risk range, is attainable using available technologies and is measurable using the available laboratory technologies. It is also lower than the current EPA MCL for drinking water for arsenic of 10 µg/l.

This value of 3 ug/l has been vetted and promulgated by the WQCC and therefore is a supportable Alternate Remedial Goal for use at the Site.

9.2 Remedial Alternatives Considered in the FFS

Water quality standards for the Eagle River have not yet been met. As a result, CBS prepared a FFS in 2013 to compare alternatives for additional remediation at the Site. Due to the fact that arsenic appears to co-exist with the other metals of interest - cadmium, copper and zinc - the selected remedy for additional remediation to reduce metals loading to the Eagle River is expected to also reduce arsenic loading to the Eagle River. The Preferred Alternative has not yet been selected because the Proposed Plan has not been finalized. The following alternatives (Table 8) were evaluated in the FFS:


32

Table 8 - Remedial Alternatives Evaluated in the FFS

ALTERNATIVE 1: No additional action

ALTERNATIVE 2A: Groundwater Collection and Treatment, Belden and Rock Creek

This alternative involves collection of groundwater in Belden and Rock Creek through either a French drain system or extraction wells, with treatment of collected water at the water treatment plant. This system would be designed to capture contaminated groundwater that enters the Eagle River during spring.

ALTERNATIVE 2B: In‐Mine Precipitation in Bleakhouse Mine Pool. This alternative involves treating mine water with lime or sodium hydroxide to raise the pH and cause metals to precipitate as insoluble chemicals within the mine itself. The goal of this alternative is to reduce the metals concentrations in the mine pool until seepage at Rock Creek no longer causes poor water. The water treatment plant would function as a backup, treating water from Adit 5 to ensure the mine pool is maintained below a critical elevation.

ALTERNATIVE 2C: Iron‐Rich Material Reaction Wall in Belden. This alternative involves treatment of groundwater through passive treatment in a trench in Belden, containing iron‐rich material. As groundwater flows through the iron‐rich material, chemical reactions will reduce the concentration of metals in the groundwater before the groundwater reaches the Eagle River. Groundwater within the Rock Creek canyon would be collected and treated at the water treatment plant (as in Alternative 2A).

ALTERNATIVE 3A: Excavate, Transport and Dispose Accessible and Acid‐Generating Waste Rock On‐Site This alternative involves excavation and transportation by off‐road trucks of acid‐generating mine waste piles 8,9, 10 and the remnants of 14 to

an on‐site repository at the consolidated tailings pile. The truck haul route would utilize the rail easement along the river from Belden to the consolidated tailings pile, to minimize impacts to local traffic.

ALTERNATIVE 3B: Excavate, Transport and Dispose All Waste Rock On‐Site

This alternative involves excavation and transportation of all waste rock piles by off‐road trucks to an on‐site repository at the consolidated tailings pile. The truck haul route would utilize the rail right-of-way along the river from Belden to the consolidated tailings pile.

ALTERNATIVE 3C: Excavate, Transport and Dispose All Waste Rock Off‐Site This alternative involves excavation and transportation of all waste rock piles to an off‐site repository for disposal. Note that off‐site disposal would need to comply with hazardous waste regulations and EPA’s off‐ site disposal policies.

ALTERNATIVE 4A: Groundwater Collection and Treatment, Old Tailings Pile/Rex Flats

This alternative involves constructing interceptor trenches to collect groundwater seepage from the old tailings pile and Rex Flats areas. Groundwater collection would occur along the west bank of the Eagle River at the old tailings pile, and along the south bank of the river at Rex Flats. The collected water would be pumped to a new water treatment facility.

ALTERNATIVE 4B: Iron‐Rich Material Reaction Wall at Old Tailings Pile/Rex Flats

This alternative involves constructing trenches containing iron‐rich material at the old tailings pile and at Rex Flats. Groundwater moving to the river from the old tailings pile and Rex Flats would be treated as it passes through the iron‐rich material.


33

9.3 Comparative Analysis of Alternatives

In accordance with the National Contingency Plan, the relative performance of each alternative is evaluated using the nine criteria (40 CFR § 300.430 (e)(9)(iii)) of the NCP as a basis for comparison. The purpose of the evaluation process is to determine which alternative: (a) meets the threshold criteria of overall protection of human health and the environment and attainment of ARARs, (b) provides the “best balance” with respect to the five balancing criteria of 40 CFR § 300.430 (e)(9)(iii)(C)0(g), and (c) takes into consideration the acceptance of the state and the community. The FFS provides a detailed evaluation of the alternatives in relation to the nine criteria. However, none of the alternatives are capable of meeting of the 0.02 µg/l arsenic CSWQS ARAR, which is the primary reason why this TI waiver is being pursued prior to publication of the Proposed Plan. Once the TI Waiver is granted, then the Proposed Plan will be published comparing the alternatives to the alternative remedial goal for arsenic (3 µg/l) and the other ARARs for metals.

Any of the proposed alternatives (except No Action) that will reduce the metals load to the Eagle River are expected to also reduce arsenic concentrations in the Eagle River to the extent practicable. Alternatives 2A and 2C focus on groundwater in Belden. These alternatives will most likely have the greatest impact on reducing arsenic loading in Segment 5a, which was demonstrated to have the greatest arsenic loading. These two alternatives are protective of human health and the environment and meet other CERCLA Section 121 statutory requirements, are cost-effective and incorporate permanent solutions and treatment to the maximum extent practicable.

The remaining alternatives, as stand-alone alternatives are not expected to be effective at further reducing arsenic concentrations in the Eagle River because they do not address the primary source of arsenic contamination – groundwater in Belden. Combinations of alternatives may be considered to enhance the overall effectiveness of the final chosen remedy. For a complete description of the alternatives and comparison to the nine CERCLA Criteria, the reader is referred to the FFS.

However, as explained previously, the ARAR is set at such a low concentration that it cannot be measured accurately by a laboratory at this level. In addition, even if the selected alternative is effective at removing all of the arsenic entering the Eagle River from on-site sources, the background concentration of arsenic in the Eagle River will still exceed the ARAR. The agencies have selected an alternate remedial goal of 3 µg/l for the Site to use in lieu of the CSWQS; the proposed remedial alternatives (except No Action) or combinations of alternatives will meet this new remedial goal for the Site, which is protective of human health and the environment (See Appendix B).

Sections 10 & 11 Summary and Conclusions

TI Zone Boundaries

34

Section 10 Summary and Conclusions

The CSM (Section 7) showed that a pulse of metals-laden water enters the Eagle River during the snow-melt period in March and April each year. Arsenic occurs in the river year-round, but is expected to be worse during the snow melt period, based on high concentrations of arsenic detected in samples of groundwater collected from Belden. Arsenic also enters the Site from upstream in concentrations that exceed the ARAR, making it impossible to meet the ARAR, even if all of the on-site arsenic were to be removed.

This evaluation concludes that it is technically impracticable to reduce arsenic concentrations to levels that would meet the 0.02 µg/l water + fish CSWQS. The upstream (background) concentration is 0.35 µg/l; therefore, it is technically infeasible to remove arsenic to levels below 0.35 µg/l on-site and arsenic cannot currently be measured using available laboratory techniques at the concentration mandated by the standard. The alternative remedial strategies being contemplated for the Site in the FFS are protective of human health and the environment and will meet the alternate remedial goal of 3 µg/l should the arsenic standard be waived.

Section 11 TI Zone Boundaries Figure 7 delineates the extent of the Eagle River segments that are included in this TI Waiver evaluation, including Segments 5a, 5b, 5c and 7b.

Sections 10 & 11 Summary and Conclusions

TI Zone Boundaries

35

Figure 7 - TI Zone Boundary

Section 12 References

36

Section 12 References Colorado Department of Public Health and Environment, September 2005. Eagle Mine Superfund Site, Second Five-Year Review Report. Colorado Department of Public Health and Environment, 2013. Water Quality Control Division, Hearing Documents for Arsenic Temporary Modification Hearing. Engineering Science, June 15, 1985. Eagle Mine Complex, Preliminary Consultant’s Report. NewFields, July 2013. Eagle Mine Site, Focused Feasibility Study. NewFields, 2015a. Eagle Mine Annual Report – 2014, Eagle Mine Site, Minturn, Colorado. NewFields, 2015b.. Focused Feasibility Study Addendum 2015 Arsenic Results, Eagle Mine Site, June 2015. U.S. Department of Agriculture, 1992-1993. White River National Forest Hydric Soil Digital Ortho Quadrangle. U.S. Environmental Protection Agency, 1993. Guidance for Evaluating the Technical Impracticability of Ground Water Restoration. U.S. Geological Survey, 1977. Geology of the Minturn 15-Minute Quad, Eagle and Summit Counties, Colorado. USGS Professional Paper 956.

APPENDIX A

Focused Feasibility Study Addendum 2015 Arsenic Results (Excerpt)

October 30, 2014

MEMORANDUM SUBJECT: Arsenic in Surface Water at the Eagle Mine NPL Site OU 1 FROM: Susan Griffin, PhD, DABT Senior Toxicologist TO: Les Sims Remedial Project Manager The purpose of this memorandum is to provide some perspective on the arsenic concentrations in surface water at the Eagle Mine NPL Site OU 1 and the CDPHE surface water quality standard for arsenic of 0.02 ug/l. Health risks were estimated for recreational and/or residential users consuming the surface water and ingesting fish from the Eagle River at OU 1. Ingestion of Surface Water In the human health risk assessment for OU 3 (ERM 2007), it was assumed that recreational users such as anglers, hikers, and rafters could potentially be exposed to surface water in the Eagle River. These recreational scenarios were applied to surface water data collected in 2012-2013 for OU 1 and provided by CDPHE. Site-specific exposure assumptions from the OU 3 risk assessment were used in conjunction with EPA’s updated exposure factors for general exposure assumptions (USEPA, 2014a). Cancer and non-cancer toxicity values for arsenic were taken from EPA’s IRIS database (USEPA 2014b) and are the same as those used in the OU 3 risk assessment. Both cancer and non-cancer risk were calculated for four different sampling locations along the Eagle River and two tributaries coming into the Eagle River. E3, above Beldon, is considered to be a background location. The angler is expected to receive the highest exposures to surface water of all the recreational receptors, therefore, the results for the angler are shown in Table 1. All non-cancer risks are below a hazard index of 1.0 and all cancer risks are below EPA’s acceptable risk range of 1E-06 – 1E-04. The risks to recreational users from the incidental ingestion of surface water are negligible. The risks from incidental ingestion of surface water from the downstream segments is not that dissimilar from the risks associated with the background locations. Risks were also calculated for residential use of the surface water as a drinking source. The risk calculations assume that an individual will consume 2.5 liters of the surface water per day, for 350 days per year, for 30 or 70 years. Cancer and non-cancer toxicity values for arsenic were taken from

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8

1595 Wynkoop Street

DENVER, CO 80202-1129 Phone 800-227-8917

http://www.epa.gov/region08

EPA’s IRIS database (USEPA 2014b) and are the same as those used in the OU 3 risk assessment. Since Minturn is the nearest residential location, the surface water data from Minturn was used. It should be noted that Minturn receives its drinking water from Cross Creek, a clean tributary, and not from the Eagle River. A calculation was also included for Cross Creek (T18) for comparison. The non-cancer risk was 0.04 and the cancer risk was 7.4E-06 for Minturn. For Cross Creek the non-cancer and cancer risks were 0.02 and 4.1E-06, respectively. All risks from using the surface water as a residential drinking water source are within EPA’s acceptable risk range. The surface water concentrations in Eagle River ranged from 0.278 to 2.17 ug/L, which are well below EPA’s federal drinking water standard of 10 ug/L. Ingestion of Fish CDPHE provided fish tissue data from fish sampled in 2007. Similar to the OU 3 risk assessment it was assumed that the freshwater angler would ingest all fish from the Eagle River. Site- specific exposure assumptions from the OU 3 risk assessment were used in conjunction with EPA’s updated exposure factors for general exposure assumptions (USEPA, 2014a). Ten percent of the arsenic was assumed to be inorganic arsenic (USEPA 2003). Both cancer and non-cancer risk were calculated for four different sampling locations along the Eagle River. Site 1, Redcliff, is considered to be a background location. The results are shown in Table 2. All non-cancer risks are below a hazard index of 1.0 and all cancer risks are below EPA’s acceptable risk range of 1E-06 – 1E-04. With respect to the potential for cancer risks from arsenic in fish it is worth noting that the concentrations of arsenic measured in fish from the site (an average of 0.045 to 0.685 mg/kg) are similar to levels expected in fish purchased at the store, usually about 2-7 mg/kg in seafood and about 0.05 – 0.5 mg/kg in freshwater fish (USEPA 2005, Yost et al 1998, and Schoof et al 1999, Schoof and Yager 2007). It should also be noted that the concentrations in fish tissue at the background location in Redcliff are higher than two of the site sampling locations. Conclusion Based on the results of the risk calculations above, the arsenic concentrations in surface water and fish tissue are within EPA’s acceptable risk ranges for recreational and/or residential receptors.

References ERM (Environmental Resources Management (2007). Human Health Risk Assessment for the Bolts Lake Area and Areas Within OU-1 of the Eagle Mine Site (http://www2.epa.gov/sites/production/files/documents/HumanHealthRiskAssessment02Feb07.pdf).

USEPA (2003). Technical summary of information available on the bioaccumulation of arsenic in aquatic organisms. Washington, DC: U.S. Environmental Protection Agency. EPA822R03032. http://www.epa.gov/waterscience/criteria/arsenic/tech-sum-bioacc.pdf. August 27, 2007.

USEPA (2005). Toxicity and Exposure Concerns Related to Arsenic in Seafood: An Arsenic Literature Review for Risk Assessments. Part 1: Exposure Concerns. Draft report prepared for USEPA, Office of Superfund Remediation and Technical Innovation, by Syracuse Research Corp. SRC-TR-04-048. May 2005 USEPA (2014a). Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors. OSWER Directive 9200.1-120 (http://www.epa.gov/oswer/riskassessment/pdf/superfund-hh-exposure/OSWER-Directive-9200-1-

120-ExposureFactors.pdf). USEPA (2014b). Integrated Risk Information System. 2014 (http://www.epa.gov/iris/). Yost LJ, Schoof RA and Aucoin R. (1998). Intake of Inorganic Arsenic in the North American Diet. Human and Ecological Risk Assessment 4:137:152. Schoof RA, Yost LJ, Eickhoff J, Crecelius EA, Cragin DW, Meacher DM, and Menzel DB. (1999). A market basket survey of Inorganic Arsenic in Food. Food Chem. Toxicol. 37:839:846. Schoof RA and Yager JW (2007). Variation of Total and Speciated Arsenic in Commonly Consumed Fish and Seafood. Human and Ecological Risk Assessment. 13: 946-965.

Table 1: Risks for Recreational Anglers from Surface Water Ingestion

Sampling Location

Surface Water Conc (ug/L)

Non-cancer Hazard Index

Cancer Risk

E3 Above Beldon

(Background)

0.278 0.0001 2.6E-08

E10 – Between Belden and Rock

Creek

0.497 0.0002 4.7E-08

E12A – Below Rex Flats

0.596 0.0003 5.7E-08

E22 – Below Minturn

0.427 0.0002 4.1E-08

T10 – Rock Creek

2.17 0.001 9.2E-08

T18 – Cross Creek

0.245 0.0001 2.3E-08

Table 2: Risk for Residential Receptors from Surface Water Ingestion

Sampling Location Surface Water Conc (ug/L)

Non-Cancer Hazard Index

Cancer Risk

E22 – Below Minturn

0.427 0.04 7.4E-06

T18 – Cross Creek 0.245 0.02 4.1E-06

Table 3: Risk for Recreational Angler from Fish Ingestion

Sampling Location Fish Tissue Conc (mg/kg)

Non-Cancer Hazard Index

Cancer Risk

Site 1 - Redcliff 0.085 0.01 2.0E-06 Site 3 – Two Elk 0.045 0.01 1.0E-06 Site 4 - Boneyard 0.685 0.08 1.6E-05

Site 5 – Below Minturn

0.057 0.01 1.3E-06

APPENDIX B

Memoranda from Susan Griffin, PhD, to Les Sims dated October 30, 2014 and January 20, 2015

January 20, 2015

MEMORANDUM SUBJECT: Preliminary Remediation Goals for Arsenic in Surface Water at the Eagle Mine NPL

Site OU 1 FROM: Susan Griffin, PhD, DABT Senior Toxicologist TO: Les Sims Remedial Project Manager The memorandum is an addendum to the memorandum entitled Arsenic in Surface Water at the Eagle Mine NPL Site OU 1 dated October 30, 2014. The purpose of this memorandum to provide risk-based preliminary remediation goals (PRGs) for arsenic in surface water at the Eagle Mine NPL Site OU 1 which are protective of recreational and residential users consuming the surface water and ingesting fish from the Eagle River at OU 1. Ingestion of Surface Water The PRGs for the recreational user (the angler) and the resident were based on the exposure and toxicity assumptions outlined in the October 30, 2014 memo. Those assumptions are shown in Table 1 for completeness. The PRGs are presented as concentrations in surface water ranging from a 1E-06 to 1E-04 cancer risk and as a non-cancer hazard index of 1.0. For the recreational user the surface water concentrations at a 1E-06 to 1E-04 cancer risk are 11 to 1100 ug/L, and 2000 ug/L at a non-cancer hazard index of 1.0. For the resident the surface water concentrations at a 1E-06 to 1E-04 cancer risk are 0.06 to 6 ug/L, and 12 ug/L at a non-cancer hazard index of 1.0. Ingestion of Fish Calculating a PRG for surface to be protective of fish ingestion is more problematic. In the calculation of the CDPHE surface water quality standard for arsenic, a bioconcentration factor (BCF) of 1L/kg was used to estimate the amount of arsenic in fish tissue from the arsenic concentration in surface water. A BCF reflects contaminant accumulation by fish only through the water column, as opposed to the bioaccumulation factor (BAF) which measures accumulation from all the potential

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8

1595 Wynkoop Street

DENVER, CO 80202-1129 Phone 800-227-8917

http://www.epa.gov/region08

exposure routes (e.g., food, sediment, and water). There is a great deal of uncertainty associated with these values. In EPA’s Technical Summary of Information Available on the Bioaccumulation of Arsenic in Aquatic Organisms (USEPA 2003), the laboratory measured values for BCFs for total arsenic in freshwater fish ranged from 0.048 L/kg to 14 L/kg. Dr. Jim Keating in EPA’s Office of Water has presented evidence that the bioaccumulation factor for total arsenic may have an inverse relationship with ambient water levels, suggesting that setting a water quality criterion for arsenic is not straightforward or even plausible. How these BCFs apply to inorganic arsenic is also a question mark. Borak and Hosgood (2007) state that very little inorganic arsenic is taken up by aquatic organisms from the water. Most aquatic organisms accumulate arsenic primarily from their food. The field measured bioaccumulation factors in USEPA 2003 for freshwater fish would support this statement. Those values range from 19 to 96 L/kg. The only reliable method for determining inorganic arsenic levels in fish tissue is to analyze the exposed fish according to Dr. Dan Wall, the ecotoxicologist in USEPA Region 8. For the sake of argument, though, if a bioconcentration factor of 1 L/kg were to be used, we would assume that 0.085 mg/kg arsenic in fish tissue (such as that measured at Redcliff) would correspond to 0.085 mg/l in surface water. The exposure and toxicity assumption used for the angler are outlined in the October 30, 2014 memo and shown in Table 2 for completeness. For the recreational angler, the surface water concentrations at a 1E-06 to 1E-04 cancer risk are 44 to 4400 ug/L, and 8000 ug/L at a non-cancer hazard index of 1.0. Conclusion PRGs were developed for both the recreational and residential user for surface water ingestion and fish consumption. The values are presented in Table 3 both individually and combined because of the uncertainty associated with the land use and the use of a bioconcentration factor to estimate fish tissue concentration from water concentrations. If one were to assume that a resident were to ingest 2.5 liters of surface water/day for 70 years from the Eagle River OU 1 and consume all of their fish from OU 1, then the PRGs from the drinking water pathway would be protective of both exposure routes.

References Borak J. and Hosgood H.D. (2007). Seafood Arsenic: Implications for Human Risk Assessment. Reg. Tox. Pharm. 47: 204-212.

USEPA (2003). Technical summary of information available on the bioaccumulation of arsenic in aquatic organisms. Washington, DC: U.S. Environmental Protection Agency. EPA822R03032. http://www.epa.gov/waterscience/criteria/arsenic/tech-sum-bioacc.pdf. August 27, 2007.

Table 1: Exposure Assumptions for Recreational Anglers and Residents from Surface Water Ingestion

Exposure Parameter Recreational

Receptor Residential Receptor

Ingestion rate water (L/day)

0.5 2.5

Exposure frequency (days/yr)

100 350

Exposure duration (yrs) 26 26 Body weight (kg) 80 80 Reference Dose (mg/kg/day)

0.0003 0.0003

Cancer Slope Factor(mg/kg-day)-1

1.5 1.5

Table 2: Exposure Assumptions for Recreational Angler from Fish Ingestion

Exposure Parameter Recreational Receptor

Ingestion rate fish (mg/day) 54000 Exposure frequency (days/yr) 225

Exposure duration (yr) 26 Body weight 80

% inorganic arsenic 10 Reference Dose (mg/kg/day) 0.0003

Cancer Slope Factor(mg/kg-day)-1 1.5

Table 3: PRGs for Recreational Angler and Resident for Arsenic in Surface Water

Receptor/ Exposure Pathway

1E-06 Cancer Risk 1E-04 Cancer Risk Hazard Index = 1.0

Angler – surface water (ug/L)

11 1100 2000

Angler – fish ingestion (ug/L)

44 4400 8000

Resident – surface water (ug/L)

0.06 6 12

Resident – surface water plus fish

ingestion (ug/L)

0.06 6 12

APPENDIX B APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS - OU1

OU1 ROD Amendment B-1 September 2017

APPENDIX B APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS


Standard, Requirement,

Criteria or Limitation

Citation Status Description Action to be Taken

to Attain Requirement Type

SURFACE WATER Colorado Discharge Permit System Regulations

5 CCR 1002-61, Regulation No. 61, pursuant to CRS § 25-8-501 et. seq.

Applicable Establishes program for permitting discharges of contaminants into waters of the United States within Colorado, including discharges of storm water during construction activities. Disturbing 5 acres trigger storm water controls, which are subject to best management practices, and additional controls to maintain WQS.

Discharge from the WTP will comply with this regulation.

A/C

Colorado Effluent Limitations

5 CCR 1002-62, Regulation #62, pursuant to CRS § 25-8-205

Applicable Sets effluent limitations for point source discharges.

Discharge from the WTP will comply with this regulation.

A/C

Rules and Regulations for Water Well Construction, Pump Installation, Cistern Installation, and Monitoring and Observation Well/Hole Construction

2 CCR 402-2 Applicable Identifies the proper location, construction, repair, and abandonment of wells, the proper installation and repair of pumping equipment, and the licensing and regulation of persons engaging in the business of contracting either for the construction of wells or for the installation of pumping equipment. Wells within a CERCLA site do not require a permit.

New wells will be constructed in accordance with regulations if installed pursuant to remedial design.

A

Colorado Basic Standards and Methodologies for Surface Water

5 CCR 1002-31, pursuant to CRS § 25-8-101 et. seq.

Applicable Establishes Statewide water quality standards, specific surface water quality standards and an antidegradation rule.

Remedial activities should result in attainment of the basic standards for the COCs identified for surface water.

A/C






Colorado Surface Water Quality Classifications and Numeric Standards for Upper Colorado River Basin

5 CCR 1002-33, pursuant to CRS §§ 25-8-203 and 204

Applicable Assigns water quality standards and classifications for State surface waters in the Upper Colorado River Basin including the Eagle River. Water Quality Control Commission issued a Final Rule effective January 1, 2009 for Segments 5 and 7 of the Eagle River Basin.

Remedial activities should result in attainment of the numeric standards for the COCs identified for surface water except for Arsenic. A technical impracticability waiver applies to the Arsenic standard, and remedial activities should result in attainment of the alternate remedial goal.

C

WETLANDS AND FLOODPLAINS CWA Section 404 33 U.S.C. § 1344, 40

CFR Parts 230 and 231, 33 CFR Part 323

Applicable Prohibits discharge of dredged or fill material into wetlands or navigable waters of the U.S. without permission.

Remedial activities might impact waters of the U.S. Section 404 applies to jurisdictional wetlands at the Site that are contaminated or likely contaminated.

A/L

Executive Order on Protection of Wetlands

Exec. Order No. 11990; §§ 1(a) and 2(a); 44 CFR §§ 9.11(b)(2), (b)(4), and (c)(3)

TBC

Relevant and Appropriate

Requires Federal agencies to avoid, to the extent possible, the adverse impacts associated with the destruction or loss of wetlands. The Executive Order is “to be considered” because it is not a promulgated regulation. Nonetheless, EPA is required to comply with the Executive Order.

Remedial activities shall take action to minimize the destruction, loss or degradation of wetlands and to preserve and enhance beneficial values of wetlands by avoiding undertaking construction located in wetlands unless: 1) there is no practicable alternative to such construction, and 2) the proposed action includes all practicable measures to minimize harm to wetlands which may result from such use.

A/L

Executive Order on Floodplain Management

Exec. Order No. 11988; §§ 1 and 2(a)(2); Exec. Order No. 13690 § 2(c); 40 CFR § 6.302(b) and Statement of Procedures on Floodplain Management and Wetlands Protection; 44 CFR §§ 9.11(b)(2), (b)(4), and (c)(3)

TBC


Limits activities in floodplains, defined as “the lowland and relatively flat areas adjoining inland and coastal waters ... including at a minimum, that area subject to a one percent or greater chance of flooding in any given year.” Federal agencies must evaluate the potential effects of actions taken in a floodplain and avoid adverse impacts from remedial activities.

Remedial activities will take action to reduce the risk of flood loss, to minimize the impact of floods on human safety, health and welfare, and to restore and preserve the natural and beneficial values served by floodplains.

A/L






AIR Colorado Fugitive Dust Control Plan/Opacity, Regulation No. 1

5 CCR 1001-3, pursuant to Colorado Air Pollution Prevention and Control Act, CRS § 25-7-101 et. seq.

Applicable Establishes regulations concerning fugitive emissions from construction activities, storage and stockpiling activities, haul trucks, and tailings ponds.

Applicable to remedial activities including removal, storage, transport and stockpiling of excavated materials. Remedial activities will require development of an acceptable fugitive emissions control plan. Dust suppression will be used as needed during construction and maintenance of the remedy.

A

Colorado Primary and Secondary Ambient Air

5 CCR 1001-14, pursuant to CRS § 25-7-108


Sets ambient air quality standards for “criteria pollutants” including particulate matter and lead.

Monitoring for compliance with ambient air quality standards may be necessary during excavation activities.

C

Colorado Emission Standards for Hazardous Air Pollutants

5 CCR 1001-10, pursuant to CRS § 25-7-108


Sets emission standards for designated hazardous pollutants, including inorganic arsenic emitted by specified industrial operations.

Monitoring for Hazardous Air Pollutants may be necessary during excavation activities.

C

SOLID AND HAZARDOUS WASTE MANAGEMENT Colorado Regulations Pertaining to Solid Waste Sites and Facilities

6 CCR 1007-2, Part 1 §§ 1, 2, and 12, pursuant to CRS § 30-20-100.5 et. seq.

Applicable Establishes requirements and procedures for land disposal of solid wastes.

Waste generated during the remedial action, including disposal of excavation or demolition materials and other solid wastes will be managed and disposed in accordance with this regulation.

A/L

Colorado Hazardous Waste Management Regulations

6 CCR 1007-3, Parts 260, 261, 264, 265, and 268 pursuant to CRS § 25-15-101, et. seq.


Establishes requirements regulating the use, handling and disposal of hazardous waste. These requirements are applicable for materials not subject to the RCRA Bevill Amendment, and, notwithstanding the Bevill Amendment, relevant and appropriate for wastes sufficiently similar to RCRA hazardous wastes (e.g., low volume and high toxicity). See 55 Fed. Reg. 8763.

Materials removed during excavation or construction of the remedy (soil, tailings, ore, roaster waste and debris) will be characterized and, if hazardous, disposed of in accordance with these regulations.

A

EPA Regional Screening Levels

http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/Generic_Tables/index.htm

TBC Provides calculated direct exposure levels for residential and industrial exposure scenarios deemed protective of human health.

If additional cleanup values are needed, as determined during RD/RA, EPA RSLs will be used as the starting point for risk-based cleanup levels.

C






MINING RECLAMATION Colorado Mined Land Reclamation Act

2 CRS 407-1, § 3, pursuant to CRS 34-32-101-127


Regulates all aspects of mining, including location of operations, reclamation, and other environmental and socioeconomic impacts.

Applies to areas where mine wastes are removed and vegetation is required.

A/L

Colorado Noxious Weed Act; Eagle County Noxious Weed regulations

CRS § 35-5.5-101 to 119; 8 CCR 1206-2

Applicable

TBC

Colorado and Eagle County Regulations addressing management of noxious weeds.

Remedial activities must minimize the introduction or spread of noxious weeds and comply with the applicable management objectives of eradication, suppression and/or containment as set forth by Eagle County and/or the Colorado Department of Agriculture. Eagle County regulations are TBC.

L

ENVIRONMENTAL COVENANTS Colorado Environmental Covenants

CRS §§ 25-15-317, et. seq.

Applicable Requires environmental covenants (ECs) or notices of environmental use restrictions (RNs) whenever residual contamination not safe for all uses is left in place or an engineered feature or structure that requires monitoring, maintenance, or operation is included in the remedy.

The substantive provisions of the EC statute are ARARs. Creation of an EC is dependent on compliance with procedural or administrative provisions and the discretion of CDPHE. CDPHE will seek an EC restricting future reuse activities that may disturb areas where engineered features exist on the Site. CDPHE states through concurring on this ROD that if the EC presented to CDPHE includes the Land Use Restrictions set forth in this ROD, is signed or approved by the landowner, and follows the provisions of the Colorado EC Statute, CDPHE will accept the EC. Further, CDPHE states through concurrence on this ROD that ECs will only be modified or terminated to reflect changes made to the Superfund remedy.

A/L






FISH AND WILDLIFE Endangered Species Act

16 U.S.C. §§ 1531 to 1544, 50 CFR Parts 17, 402, 40 CFR § 6.302(h)

Applicable Requires that Federal agencies ensure that any action authorized, funded, or carried out by the agency is not likely to jeopardize the continued existence of any threatened or endangered species or destroy or adversely modify critical habitat.

Regulations will be complied with if endangered or threatened plants, fish or wildlife or critical habitat is identified during RD/RA.

L

Bald and Golden Eagles Protection Act

16 U.S.C. § 668 et. seq. Applicable Prohibits the taking, possession, sale, purchase, barter, transport, export/import at any time or in any manner, any bald (American) or any golden eagle, alive or dead, or any part, nest, or egg; establishes civil and criminal penalties (where “take” has been construed to affect habitat as well as physical possession of the eagles).

Remedial activities must avoid actions that affect Bald or Golden Eagles in a manner prohibited by the Act, including actions that constitute “taking,” “possession” or “use.”

A/L

Migratory Bird Treaty Act

16 U.S.C. §§ 703 and 707

Applicable Establishes federal responsibility for the protection of international migratory bird resources from pursuit, hunt, take, capture or kill by hunters and poachers.

Remedial activities must avoid actions that affect migratory birds in a manner prohibited by the Act, including actions that constitute “taking,” “possession” or “use.”

A

Colorado Wildlife Enforcement and Penalties Act

CRS § 33-6-101 et. seq. Applicable Prohibits actions detrimental to wildlife, and establishes provisions governing the taking, possession, hunting and use of wildlife and migratory birds.

Remedial activities must avoid actions that affect specified wildlife in a manner prohibited by the Act including actions that constitute “taking,” “possession” or “use.” The Colorado Division of Wildlife will be consulted regarding potential impacts to these species.

A/L

Colorado Non-game, Endangered, or Threatened Species Act

CRS § 33-2-101 et. seq. Applicable Protects endangered and threatened species and preserves their habitats. Requires coordination with the Division of Wildlife if remedial activities impact nongame wildlife deemed to be in need of management.

Remedial activities must avoid actions that affect these species in a manner prohibited by the Act, including actions that constitute “taking,” “possession” or “use.” The Colorado Division of Wildlife will be consulted regarding potential impacts to these species.

L






Colorado Wildlife Commission Regulations

2 CCR 406, pursuant to CRS § 33-2-101 et. seq.

Applicable Establishes specific requirements for protection of wildlife.

Remedial activities will comply with State regulations for wildlife protection. The Colorado Division of Wildlife will be consulted regarding compliance with these regulations.

A/L

Colorado Species of Special Concern and Species of Undetermined Status

Colo. Administrative Directive E-1, 1985, modified

TBC Protects animals listed on the Colorado Division of Wildlife- generated list. Coordination with the Division is strongly urged if animal species are to be impacted.

This Directive governs the Colorado Division of Wildlife procedures for establishing an endangered, threatened and/or species of special concern list. Protection of these species is covered under other ARARs; however, CBS will coordinate with the Division regarding any impacts to listed species.

L

HISTORIC PROPERTIES, LANDMARKS, AND NATURAL AREAS National Historic Preservation Act

16 U.S.C. § 470, 40 CFR § 6.301(b), 36 CFR Parts 63, 65, 800

Applicable Requires preservation of historic properties included in or eligible for the National Register of Historic Places, and requires minimization of harm to National Historic Land marks.

Will apply if eligible structures/objects will be impacted by remedial activities

L

NOISE CONTROL Colorado Noise Abatement Statute

CRS § 25-12-101 et. seq.

Applicable Establishes maximum permissible noise levels for particular time periods and land use zones.

Standards will be met during remedial activities on the Site.

A

Notes: § Section A Action-specific C Chemical-specific L Location-specific CCR Colorado Code of Regulations CDPHE Colorado Department of Public Health & Environment CERCLA Comprehensive Environmental Response, Compensation and Liability Act CFR Code of Federal Regulations COC Contaminant of concern CRS Colorado Revised Statutes

CWA Clean Water Act EC Environmental covenants EPA U.S. Environmental Protection Agency RCRA Resource Conservation and Recovery Act RD/RA Remedial Design/Remedial Action ROD Record of Decision TBC To be considered U.S.C. United States Code WQS Water Quality Standard WTP Water Treatment Plant

APPENDIX C DETAILED COST ESTIMATE

Item Notes Quantity Unit Unit Cost Total Cost

CAPITAL COSTS

Direct Construction

4" perforated HDPE pipe (installed) a,b 700 lf $ 8.00 $ 5,600.00

Cleanout (installed) a,c 4 each $ 100.00 $ 400.00

Trench excavation a,d 1,800 lf $ 65.00 $ 117,000.00

Trench membrane liner 1,166 sy $ 5.00 $ 5,830.00

Place excess excavated soil in trench 11,000 cy $ 3.50 $ 38,500.00

Geotextile filter around drainage rock a 700 lf $ 2.50 $ 1,750.00

Load Backfill a 1,000 cy $ 9.50 $ 9,500.00

Haul Backfill a,e 1,000 cy $ 4.50 $ 4,500.00

Place Backfill a,f 1,000 cy $ 3.50 $ 3,500.00

4" connecting surface pipe to existing pipeline at Rock Creek a,g 1,100 lf $ 3.50 $ 3,850.00

Remove and dispose of existing tracks i 1,000 lf $ 15.00 $ 15,000.00

Replace railroad tracks i 1,000 lf $ 75.00 $ 75,000.00

Dewatering j 3 weeks $ 500.00 $ 1,500.00

Excavate temporary sediment retention pond a,k 1,000 cy $ 2.50 $ 2,500.00

Line sediment retention pond a 750 sy $ 3.00 $ 2,250.00

Hookup to existing Pipeline at Rock Creek manhole l 1 lump $ 1,000.00 $ 1,000.00

Remove temporary sediment retention pond l 1 lump $ 2,000.00 $ 2,000.00

Mill Level dams with surface drain pipes to main pipeline l 1 lump $ 4,500.00 $ 4,500.00

Direct Construction Subtotal $ 294,180.00

Indirect Construction

Mobilization/Demobilization l 6% $ 17,651.00

Engineering Design m 10% $ 31,183.00

Project/Construction Management m 15% $ 46,775.00

Indirect Construction Subtotal $ 95,609.00

TOTAL CAPITAL COSTS $ 389,789.00

OPERATING AND MAINTENANCE (O&M) COSTS

Alternative Required O&M

Operation and Maintenance l 1 year $ 1,500.00 $ 1,500.00

Additional Water Treatment Costs, WTP h 1 year $ 12,960.00 $ 12,960.00

Alternative Required O&M Subtotal $ 14,460.00

TOTAL ANNUAL O&M COSTS $ 14,460.00

TOTAL 50-YEAR COSTS (non-discounted, see following table) $ 1,127,249.00

Present Worth Value (see following table at 7% discount) $ 604,000.00

Notes

Unless identified separately burden and profits are included in unit costs.

a Cost from Means, 2005

b Standard HDPE pipe similar in cost to perforated PVC, used perforated PVC installation cost.

c Assume cleanout consists of t-joint with HDPE riser and end cap.

d Cost assumes 3 foot bottom width of trench w/ vertical sides, 15 ft depth at Belden shallowing in downstream direction.

Length includes Tramway extension of 50 ft.

e Assumes 1.5 mile round trip and 12 cy end dump; RT Rock Creek

f Price for bedding and backfill gravel is not included, uses WP-11 gravel from Rock Creek

g Assumes 4" HDPE non-perforated pipe. Pipe will transmit at least 60 gpm on a slope of .0136

h Cost estimate $0.006 per gallon at 25 gpm for 60 days = $12,960

i Costs based on Illinois Department of Transportation FY 1998 Proposed Rail Improvement Program Supplement

j Assumes use of 6" trash pump

k Size is adequate to store 2+ days dewatering @ 60gpm

l Estimate

m Based off direct construction costs and mob/demob costs

APPENDIX C

DETAILED COST ESTIMATE

Selected Extended Remedy: Groundwater Collection and Treatment, Belden and Rock Creek


Capital Ongoing Total Annual Rate of Return = 3% Rate of Return = 7% Rate of Return = 10%

Year Costs Costs Expenditure Discount Present Discount Present Discount Present

Factor Worth Factor Worth Factor Worth

0 $389,789 $14,460 $404,249 1.0000 $404,249 1.0000 $404,249 1.0000 $404,249

1 $14,460 $14,460 0.9709 $14,039 0.9346 $13,514 0.9091 $13,145

2 $14,460 $14,460 0.9426 $13,630 0.8734 $12,630 0.8264 $11,950

3 $14,460 $14,460 0.9151 $13,233 0.8163 $11,804 0.7513 $10,864

4 $14,460 $14,460 0.8885 $12,848 0.7629 $11,031 0.6830 $9,876

5 $14,460 $14,460 0.8626 $12,473 0.7130 $10,310 0.6209 $8,979

6 $14,460 $14,460 0.8375 $12,110 0.6663 $9,635 0.5645 $8,162

7 $14,460 $14,460 0.8131 $11,757 0.6227 $9,005 0.5132 $7,420

8 $14,460 $14,460 0.7894 $11,415 0.5820 $8,416 0.4665 $6,746

9 $14,460 $14,460 0.7664 $11,082 0.5439 $7,865 0.4241 $6,132

10 $14,460 $14,460 0.7441 $10,760 0.5083 $7,351 0.3855 $5,575

11 $14,460 $14,460 0.7224 $10,446 0.4751 $6,870 0.3505 $5,068

12 $14,460 $14,460 0.7014 $10,142 0.4440 $6,420 0.3186 $4,607

13 $14,460 $14,460 0.6810 $9,847 0.4150 $6,000 0.2897 $4,189

14 $14,460 $14,460 0.6611 $9,560 0.3878 $5,608 0.2633 $3,808

15 $14,460 $14,460 0.6419 $9,281 0.3624 $5,241 0.2394 $3,462

16 $14,460 $14,460 0.6232 $9,011 0.3387 $4,898 0.2176 $3,147

17 $14,460 $14,460 0.6050 $8,749 0.3166 $4,578 0.1978 $2,861

18 $14,460 $14,460 0.5874 $8,494 0.2959 $4,278 0.1799 $2,601

19 $14,460 $14,460 0.5703 $8,246 0.2765 $3,998 0.1635 $2,364

20 $14,460 $14,460 0.5537 $8,006 0.2584 $3,737 0.1486 $2,149

21 $14,460 $14,460 0.5375 $7,773 0.2415 $3,492 0.1351 $1,954

22 $14,460 $14,460 0.5219 $7,547 0.2257 $3,264 0.1228 $1,776

23 $14,460 $14,460 0.5067 $7,327 0.2109 $3,050 0.1117 $1,615

24 $14,460 $14,460 0.4919 $7,113 0.1971 $2,851 0.1015 $1,468

25 $14,460 $14,460 0.4776 $6,906 0.1842 $2,664 0.0923 $1,335

26 $14,460 $14,460 0.4637 $6,705 0.1722 $2,490 0.0839 $1,213

27 $14,460 $14,460 0.4502 $6,510 0.1609 $2,327 0.0763 $1,103

28 $14,460 $14,460 0.4371 $6,320 0.1504 $2,175 0.0693 $1,003

29 $14,460 $14,460 0.4243 $6,136 0.1406 $2,033 0.0630 $912

30 $14,460 $14,460 0.4120 $5,957 0.1314 $1,900 0.0573 $829

31 $14,460 $14,460 0.4000 $5,784 0.1228 $1,775 0.0521 $753

32 $14,460 $14,460 0.3883 $5,615 0.1147 $1,659 0.0474 $685

33 $14,460 $14,460 0.3770 $5,452 0.1072 $1,551 0.0431 $623

34 $14,460 $14,460 0.3660 $5,293 0.1002 $1,449 0.0391 $566

35 $14,460 $14,460 0.3554 $5,139 0.0937 $1,354 0.0356 $515

36 $14,460 $14,460 0.3450 $4,989 0.0875 $1,266 0.0323 $468

37 $14,460 $14,460 0.3350 $4,844 0.0818 $1,183 0.0294 $425

38 $14,460 $14,460 0.3252 $4,703 0.0765 $1,106 0.0267 $387

39 $14,460 $14,460 0.3158 $4,566 0.0715 $1,033 0.0243 $351

40 $14,460 $14,460 0.3066 $4,433 0.0668 $966 0.0221 $319

41 $14,460 $14,460 0.2976 $4,304 0.0624 $902 0.0201 $290

42 $14,460 $14,460 0.2890 $4,178 0.0583 $843 0.0183 $264

43 $14,460 $14,460 0.2805 $4,057 0.0545 $788 0.0166 $240

44 $14,460 $14,460 0.2724 $3,938 0.0509 $737 0.0151 $218

45 $14,460 $14,460 0.2644 $3,824 0.0476 $688 0.0137 $198

46 $14,460 $14,460 0.2567 $3,712 0.0445 $643 0.0125 $180

47 $14,460 $14,460 0.2493 $3,604 0.0416 $601 0.0113 $164

48 $14,460 $14,460 0.2420 $3,499 0.0389 $562 0.0103 $149

49 $14,460 $14,460 0.2350 $3,397 0.0363 $525 0.0094 $135

50 $14,460 $14,460 0.2281 $3,298 0.0339 $491 0.0085 $123

$1,127,249

@ 3% @ 7% @ 10%

TOTAL PRESENT WORTH $776,000 $604,000 $548,000

Ongoing Costs include annual O&M costs and periodic costs

Non-discounted cost:

PRESENT WORTH ANALYSIS

APPENDIX C


Selected Extended Remedy: Groundwater Collection and Treatment, Belden and Rock Creek

FINAL Record of Decision Amendment for the Eagle Mine ... · NCP National Oil and Hazardous...

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