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February 23, 2010

United States Environmental Protection Agency ATTN: Stan Christensen, WAM/COR US EPA Region 8 1595 Wynkoop Street Denver, Colorado 80202-1129

Subject: California Gulch Operable Unit 5 Arkansas Valley Smelter/Colorado Zinc Lead Mill Site Final Remedial Action Report, Revision 1 Work Assignment No. 009-RARA-0829 Contract No. EP-W-06-006

Dear Mr. Christensen:

Pacific Westem Technologies, Ltd (PWT) is pleased to provide Revision 1 ofthe Final Remedial Action (RA) Report for the Califomia Gulch Operable Unit 5, Arkansas Valley Smelter/Colorado Zinc Lead Mill Site. This RA Report is submitted in accordance with PWT's Work Plan, dated February 5, 2009. Revision 1 updated the coordinates on Figure 2 and Appendix C to Colorado State Plane coordinates, Central Zone.

Ifyou have any questions or comments regarding this RA Report, please call me at (303) 274-5400 x48.

Sincerely,

Levi Todd, P.E. Califomia Gulch 0U5 AV/CZL Site Project Manager Pacific Westem Technologies, Ltd.

Attachment

cc: James Bush, PWT Doug Jamison, CDPHE Thomas Roberts, PWT

File

www.pwt.com

FINAL REMEDIAL ACTION REPORT

Revision 1

REMEDIAL ACTION CALIFORNIA GULCH - OPERABLE UNIT 5

ARKANSAS VALLEY / COLARADO ZINC LEAD SITES LAKE COUNTY, COLORADO

Prepared for:

^v/ US Environmental Protection Agency, Region 8

1595 Wynkoop Street, Denver, CO 80202-1129

Prepared by:

^PACIFIC WESTERN TECHNOLOGIES, LTO,

Pacific Western Technologies, Ltd 11049 W. 44* Avenue, Suite 200

Wheat Ridge, CO 80033

U.S, EPA Contract No. Work Assignment No. Work Assignment Name:

Date:

EP-W-06-006 009-RARA-0829

California Gulch OUS (AV/CZL Sites)

February 23,2010

www.pwt.com

Table of Contents

1.0 INTRODUCTION / OPERABLE UNIT BACKGROUND 1 2.0 CONSTRUCTION ACTIVITIES 2

2.1 Historical Activities 2 2.2 2009 Activities 2

2.2.1 AVSite 2 2.2.2 CZL Site 3 2.2.3 AV Consolidation Area Cover 4 2.2.4 Revegetation 5

3.0 CHRONOLOGY OF EVENTS 5 4.0 PERFORMANCE STANDARDS AND CONTRUCTION QUALITY CONTROL 6 5.0 FINAL INSPECTION AND CERTIFICATIONS 7 6.0 OPERATION & MAINTENANCE ACTIVITES 7

6.1 Cover System Inspection and Maintenance 7 6.2 Institutional Controls 7 6.3 Groundwater and Surface Water Monitoring 8

7.0 SUMMARY OF PROJECT COSTS 8 8.0 FIVE-YEAR REVIEW 8 9.0 OBSERVATIONS AND LESSONS LEARNED 8 10.0 OPERABLE UNIT CONTACT INFORMATION 8 11.0 REFERENCES 9

Tables

Table 1

Figures

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

APDendices

Appendix A Appendix B Appendix C

Chronology of Events

Site Location Map Final As-Built Survey OU-5 AV Excavation Areas CZL Excavation Areas 2009 Revegetation/Soil Amendment Areas

Soil Analytical Results Final Remedial Action Inspection Form Stamped As-Built Survey

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LIST OF ACRONYMS AND ABBREVIATIONS

Asarco Asarco Incorporated ARAR Applicable or relevant and appropriate requirements AV Arkansas Valley bgs Below ground surface CDPHE Colorado Department of Public Health and Environment CERCLA Comprehensive Environmental Response, Compensation, and Liability Act COCs Contaminants of Concem CQAP Construction Quality Assurance Plan CZL Colorado Zinc-Lead EPA U.S. Environmental Protection Agency HASP Health and Safety Plan ICs Institutional controls MFG McCulley Frick &Gihnan mg/kg Milligrams per kilogram O&M Operation and maintenance OU Operable Unit Platinum Platinum Environmental, LLC PM Project manager PWT Pacific Westem Technologies, Ltd. RA Remedial Action RD Remedial Design RFE Resident field engineer ROD Record ofDecision RPM Remedial Project Manager SAL Soil Action Levels SAP Sampling and Analysis Plan SOW Statement of Work TSP Total Suspended Particulate TTMM Tetra Tech MM

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D

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U 1.0 INTRODUCTION / OPERABLE UNIT BACKGROUND

r-] Leadville, Colorado, is located in a mineral rich area ofthe Rocky Mountains where copper, gold, silver, i lead, and zinc have been mined intermittently since 1859, when placer gold was discovered in Califomia

Gulch. Due to past mining, milling, and smelting activities, waste rock, tailings, slag, and smelter waste have been dispersed throughout the community. Previous investigations by the EPA and others indicate that mining wastes have adversely affected groundwater, surface water, and soil. On September 8,1983, EPA placed the Califomia Gulch Superfund Site, comprised ofthe town of Leadville and the adjacent mining district, on the National Priorities List. Califomia Gulch Operable Unit 5 (0U5) is comprised of the Arkansas Valley Smelter (AV) and Colorado Zinc-Lead Mill (CZL) sites, as well as additional sites throughout the Leadville area. The area of OUS consisting ofthe AV and CZL sites is shown on Figure 1.

n

D U The Record ofDecision (ROD) for the Califomia Gulch OU 5 AV/CZL Sites was signed in September

2000. The selected remedy for the OUS AV/CZL sites is excavation of contaminated soils and tailings, n consolidation in an on-site repository and placement ofa soil cover over the consolidated material, and [J ancillary remedial activities, such as demolition of selected stractures. Constraction activities associated

with the selected remedy consist of excavation and consolidation of flue dust into an on-site, [-1 geomembrane-lined, fully encapsulated repository; demolition to grade of all smelter stractures within the I remediated areas except the easternmost oftwo ore bins, the base oftwo smokestacks, and a concrete arch

(the Dewey Arch); consolidation of tailings, non-residential area soils, and non-salvageable materials at

Othe AV and CZL sites; and placement ofan 18-inch thick vegetated soil cover over both the flue dust repository and the consolidated tailing/non-residential soils. The main contaminants ofconcem (COCs) at the site are lead and arsenic in soil and tailings, and, at much higher concentrations, in flue dust. The Remedial Design (RD) {Final Remedial Design Report, Arkansas Valley Smelter and Colorado Zinc Lead

] Mill Site Operable Unit 5, Califomia Gulch Superfund Site) was completed by McCulley, Frick, and U Gilman, Inc. (MFG) (now Tetra Tech MM (TTMM)) in April 2005 for Asarco, Incorporated (which

became Asarco, LLC, hereafter collectively denoted simply as Asarco).

U MFG, under contract to Asarco, conducted remedial activities at the site during the 2004, 2005,2006, and 2007 constraction seasons. At the AV site, MFG excavated and consolidated approximately SO percent of

n the soil and tailings contaminated with lead and arsenic above commercial/industrial standards (non-{_ residential standards), constmcted a flue dust repository, excavated and placed all identified flue dust

within the repository, and capped the repository. At the CZL site, MFG excavated and consolidated r-| approximately 2,000 cubic yards of non-residential contaminated tailings. In addition, in 2007, borrow

soil for the cover to be placed over the consolidated contaminated soil and tailing was stockpiled on the site.

I The description ofthe work completed prior to the involvement of Pacific Westem Technologies, Ltd., L^ (PWT) is included in MFC's Construction Status Report, Operable Unit 5, Arkansas Valley Smelter and

Colorado Zinc-Lead Mill Site, Califomia Gulch Superfund Site, Leadville, Colorado, December 2006; r and in a technical memorandum from TTMM to Asarco, LLC, dated January 8, 2008. The January 2008 U memo also includes a description ofthe work needed to complete the Remedial Action (RA). MFG

previously completed approximately 50 percent ofthe RA.

J In 2009, EPA directed PWT to complete the RA at the Site under PWT's RAC2 Contract EP-W-06-006, and Work Assignment 009-RARA-0829. PWT's Statement of Work (SOW) included updating the RD to

ri reflect the work conducted to date and remaining work to be completed, procurement ofthe I subcontractor, implementation ofthe RA, and close out ofthe RA. PWT retained TTMM's services to

support the design efforts because of their familiarity and experience with the Site. On May 6, 2009, r-, PWT issued a Request for Proposal to prospective bidders to complete the remaining RA at the Site. On

U RA report 009-RARA-0829 Final rev 1 1 February 23, 2010

1

U RA Report, Rev. 1

D June 17, 2009, PWT selected and awarded the remediation subcontract for implementing the RA to the low bidder. Platinum Environmental, LLC (Platinum).

2.0 CONSTRUCTION ACTIVITIES

2.1 Historical Activities Asarco, through their contractor MFG, conducted remedial actions at the site during the 2004 through 2007 constraction seasons. In 2004, demolition activities, primarily associated with the westem ore bin •-and the Blast Fumace/Ore House buildings, were conducted. In 2005, the flue dust repository was constmcted, flue dust was excavated and placed within the repository, as was some ofthe non-residential T soils in the consolidation area, and flue-dust repositoiy monitoring wells were installed. In 2006, the L contaminated tailings from the CZL site were excavated and consolidated in the AV consolidation area. During the 2007 constraction season, approximately 67,000 loose cubic yards of borrow soil from the R Lake County Airport borrow area were hauled and stockpiled near the center ofthe AV consolidation area [J on top of previously consolidated soil and tailings. The Lake County Airport borrow soil had been identified as a suitable source for the consolidation area cover soil. A description ofthe work completed n prior to PWT's involvement is included in MFC's Construction Status Report, Operable Unit 5, Arkansas J Valley Smelter and Colorado Zinc-Lead Mill Site, Califomia Gulch Superfund Site, Leadville, Colorado, December 2006 (MFG 2006); and ui a technical memorandum from TTMM to Asarco dated January 8, r-, 2008 (TTMM 2008).

2.2 2009 Activities Platinum, PWT's RA constraction subcontractor, conducted and completed constraction activities during the period from July 6, 2009, through October 23,2009. The RA constraction in 2009 was completed U using the commercial/industrial use standards for Soil Action Levels (SALs) for the COCs lead and arsenic that had been identified in MFC's 2005 RD (MFG 2005). These SALs are 6,500 milligrams per f kilogram (mg/kg) for lead, and 650 mg/kg for arsenic. The SALs identified in the ROD for L commercial/industrial use were 6,100 to 7,700 mg/kg for lead and 610 to 690 mg/kg for arsenic, and for recreational use the ROD SALs were 16,000 mg/kg for lead, and 1,400 to 3,200 mg/kg arsenic (EPA T 2000). All concentrations of COCs that were less than the SALs used for the 2009 constraction activities |_ were also below the lower limit ofthe range of commercial/industrial use SALs identified in the ROD.

2.2.1 AV Site After Asarco's remedial activities in 2004 through 2007, MFG identified six areas (Areas 1, 2, 3, 4, 5 and 6) at the AV site as remaining or potentially remaining to be excavated. Soil in Areas 1,5, and 6 had p previously been excavated, but additional confumatory sampling needed to be conducted (MFG 2006). Therefore, PWT sampled and analyzed the soil from these areas in accordance with the California Gulch Operable Unit 5, Arkansas Valley Smelter cmd Colorado Zinc Lead Site, Remedial Action, Construction |—, Quality Assurance Plan, (PWT 2009b) to determine if remediation would be required. Each area was subdivided into approximately one-half acre decision areas as necessary, and four random subsamples of soil, collected from zero to six inches in depth, were composited from each decision area. The samples were analyzed for lead and arsenic by ICP analysis, using EPA method 601 OB. Concentrations of lead and arsenic in Areas 1,5, and 6 were below SALs, so no additional remediation activities were conducted ^ in these areas (see Appendix A for results).

Based on previous sampling results conducted by MFG (MFG 2006), and as reflected on the 2009 U constraction drawings (PWT 2009a), Area 2 required excavation ofa minimum 1.5-feet of soil. Area 3 required excavation of a minimum 1 -foot of soil, and Area 4 required excavation of a minimum of 2-feet H of soil. All contaminated AV soil was excavated to the design extent and nominal depth, and placed in jJ the AV consolidation area and graded to provide positive drainage. Post-excavation surveys indicated that the design excavation depths were not achieved in limited or isolated areas. However, it was decided p

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to conduct confirmatory sampling on the excavated surface rather than conduct "surgical" excavation. If any sampled area showed concentrations above SALs, then further excavation would be considered.

After the initial excavation activities ofthe AV site were completed. Area 2 was split into subareas of approximately 0.5-acres each for confirmatory sampling purposes (Figure 3). Confirmatory sampling and analyses was conducted in these subareas in accordance with the Constraction Quality Assurance Plan (CQAP). One composite sample, comprised of 4 subsamples collected from the upper six inches, was collected from each subarea and analyzed for lead and arsenic (PWT 2009b). Composite soil samples for each of these areas demonstrated that COCs concentrations in the remaining soil within all of Area 2 were below SALs.

Area 3 was also split into subareas of approximately 0.5-acres each for confirmatory sampling purposes (Figure 3). Concentrations of arsenic in subareas 3 A, 3B, and 3E were above SALs. Subareas 3 A, 3B, and 3E were excavated by an additional 1.5 feet. After completion ofthe additional excavation, subareas 3A, 3B and 3E were resampled and analyzed for the COCs. The concentrations of arsenic were still higher than the SAL prescribed in the ROD for all three subareas. Based on site knowledge and the supposition that it was likely that the contamination extended deeper than another one foot, the U.S. Environmental Protection Agency (EPA) Remedial Project Manager (RPM) directed that subareas 3A, 3B, and 3E not be excavated fiirther, but rather backfilled with borrow soil to a minimum depth of six inches. This approach was implemented with the understanding that these subareas do not themselves constitute an exposure unit, and that average lead and arsenic concentrations at the site are less than the SALs. Placement of backfill is an additional measure that breaks any immediate and localized exposure pathway. Subarea 3E received a nominal six inches of soil cover, whereas subareas 3 A and 3B received a nominal thickness of 12 inches of soil cover. This backfill was also placed to ensure positive drainage off subareas 3B and 3E.

After initial excavation, sampling results indicated that concentrations of arsenic in Area 4 were above SALs. The soil in Area 4 was excavated by an additional two feet and resampled. Area 4 resampling results indicated that the concentration of arsenic was still above the SAL. Upon direction from the EPA RPM, this area was also backfilled with borrow soil that was a minimum two-feet thick).

2.2.2 CZL Site Three different areas ofthe CZL site were addressed as part ofthe RA (Figure 4): (1) slope area, (2) fluvial tailings area, and (3) the designed CZL consolidation area. Both the ROD and MFC's design indicated that additional sampling should be conducted in the slope area to more clearly define the extent of contamination (EPA 2000, MFG 2006). As an initial sampling screening effort, seven discreet samples were collected from the surface ofthe slope area and analyzed for lead and arsenic. Only one discreet sample had concentrations of either lead or arsenic that exceeded SALs; however results from several other samples were close to the SALs. Based on those results, the CZL slope area was divided into nominal 0.5-acre subareas, consistent with the size ofthe sample subareas previously established and used at the site in 2005 - 2007, and adjusted to include similar vegetation or disturbance conditions within a subarea (see Figure 4). For example, the odd shape for CZL-E3 was partially driven by the fact that this shape comprised an area that was vegetated at the time of sampling. In accordance with the CQAP (PWT 2009b), composite samples were collected from these subareas, each composite comprising generally four subsamples (project records provide detailed sampling information) collected from the top six inches of the surface, and analyzed for lead and arsenic by ICP analysis, EPA method 601 OB. The sampling results indicated that concentrations of lead exceeded SALs in subareas CZL-W2, CZL-W5, CZL-E2, and CZL-E6. Contaminated CZL soil in these four subareas was excavated to the extent shown on Figure 4, and to a nominal depth of one foot. Upon direction from the EPA RPM, the excavated soil was placed in the AV consolidation area.

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During implementation ofthe RA in the summer of 2009, the CZL consolidation area was eliminated from the design and the RA by the EPA RPM. This was possible and appropriate because:

• The sampling results indicated that soils from only part ofthe CZL slope were contaminated, which greatly reduced the volume of CZL soils that required consolidation

• Excavation of contaminated AV soils and placement in the AV consolidation area had progressed to the point where it was recognized that placement of CZL soils in the AV consolidation area could be accommodated there without materially affecting the design or implementation

• Subsurface tailings still present in the CZL consolidation area could be excavated and consolidated at the AV site, thereby eliminating or reducing a potential source of metal loading to Califomia Gulch

• Elimination ofthe CZL consolidation area eliminated contaminated soils from being consolidated adjacent to, and within the historical flood plain of Califomia Gulch.

D

After completion ofthe 2009 excavation activities, confirmatory sampling was conducted in accordance with the CQAP (PWT 2009b). Results are presented in Appendix A. Confirmatory sampling results indicated that concentrations of lead in the "bench" area (comprised ofthe upper parts of CZL-E2, CZL-E6, CZL-WS and CZL-W6, as shown on Figure 4) were above SALs. Upon direction from the EPA RPM, this area was also backfilled with borrow soil to a minimum thickness of one foot. This approach was implemented with the understanding that the bench area does not itself constitute an exposure unit, and that average lead and arsenic concentrations at the site are less than the SALs. Placement of backfill is an additional measure that breaks any immediate and localized exposure pathway. All areas disturbed in the CZL slope during the 2009 constraction activities were surveyed after excavation.

As provided by the design, and at the direction ofthe EPA RPM, soils from the fluvial tailings area (Figure 4) were also excavated and placed in the AV consolidation area. Tailings and other residual evidence of tailings were present in the fluvial tailings area, including visual impacts, such as lack of vegetation. This excavation was conducted in order to remove visually impacted soil that was suspected of being a source of metal loading to Califomia Gulch. Therefore, confirmatory sampling ofthis area was not conducted.

Visually-evident tailings from the CZL "consolidation area" were excavated upon direction from the EPA RPM. These tailings were present at a depth of approximately 2 to 3 feet below ground surface (bgs) and extended to a depth of approximately 3 to 6 feet bgs, with the depth being greater to the west and shallower to the east. A six-inch thick clay zone was observed beneath some ofthe tailings, which might have been evidence that the historical tailings area had been lined. The excavated soil was placed in the J AV consolidation area. The CZL consolidation area was backfilled with borrow soil and graded to provide positive drainage into the Califomia Gulch channel.

— 2.2 J AV Consolidation Area Cover After completion ofthe excavation activities, the AV consolidation area was covered with a minimum of 18 inches of screened cover soil. The cover soil was from one oftwo sources, either Lake County L unscreened borrow soil that was stockpiled on the cover during Asarco activities, or borrow pit soil (see Figure 2). Both types of borrow soil were screened such that no particle size greater than 3 inches in n diameter was allowed for the cover soil. The cover soil was placed using excavators, dozers, and |J scrapers. The eastem half of the southem boundary ofthe AV consolidation cover was graded with a 3:1 (horizontal to vertical) slope with a diversion berm at the top ofthe slope. This berm is intended to direct r

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u

n stormwater sheet flow from the upper east side ofthe cover into a control swale that drains the south eastem quadrant ofthe cover (Figure 2). The site was graded in accordance to the design to ensure adequate drainage and prevent soil erosion (2% minimum slope, 3:1 maximum slope).

To prevent stormwater from entering the AV consolidation area and to collect stormwater running off the cover, a perimeter stormwater ranon/ranoff ditch was installed. All areas disturbed in the 2004 through 2009 constraction activities were graded to ensure positive drainage.

2.2.4 Revegetation Upon completion of grading activities, the AV and CZL sites were ripped and tilled for revegetation. Approximately twenty samples were collected at various locations for agronomic characteristics to provide data used in the evaluation of whether compost addition or pH mitigation of soils was necessary as part of revegetation activities. Soil was analyzed for the following:

pH electrical conductivity sodium absorption ratio cation exchange capacity Lime estimate (qualitative) or (calcium carbonate equivalency) organic matter nitrate-nitrogen phosphoras potassium magnesium zinc iron manganese copper boron sulfate-sulfur texture estimates fertilizer suggestions for agricultural, horticultural or reclamation applications.

The concentrations of organic carbon were typically one percent or greater, which are sufficient to support revegetation without addition of compost. The values of pH were typically less than 5, except for the borrow soil (neutral pH), or in areas where borrow soil had already been placed. Numerous soil areas exhibited low pH values unsuitable for revegetation. It was determined that significant cost savings could be realized by utilizing excess borrow soil rather than lime for amending the low pH-value soils. Therefore, screened borrow soil was placed in areas containing low pH soils to the extent that borrow soil was available. A minimum of 6 inches of screened borrow soil was placed in the areas shown in Figure 5. Area 2 at the AV site was the only area where lime was added. Pelletized lime was added and tilled into the soil in Area 2 at a rate of 30 tons per acre The site was fertilized with 24:4:12 (nifrogen:phosphate:potash) slow release fertilizer at a rate of 100 pounds per acre. The cover and excavated areas were revegetated in accordance with the RD.

3.0 CHRONOLOGY OF EVENTS

Table 1 presents the chronology of events at the OU-5 site.

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Table 1 - Chronology of Events

Date

September 2000

2004

April 2005

2004-2007

June 19,2009

July 2009 October 23,2009 January 2010

Event Record ofDecision signed for Operable Unit 5 AV/CZL Sites, Califomia Gulch Superfimd Site Asarco conducted demolition activities at the site MFG remedial design approved - Final Remedial Design Report, Arkansas Valley Smelter and Colorado Zinc-Lead Mill Site Operable Unit 5, Califomia Gulch Superfund Site Asarco conducted remedial actions at the site (see narrative) 2009 PWT design approved- Califomia Gulch Operable Unit 5, Arkansas Valley Smelter and Colorado Zinc Lead Site, Remedial Action, Constmction Package (PWT 2009a) 2009 remedial action constmction mobilization Final Inspection, site remedial action field work completed Final Remedial Action Report

D

4.0 PERFORMANCE STANDARDS AND CONTRUCTION QUALITY CONTROL

Approximately 41 acres of land was remediated at the AV site and approximately four acres of land was remediated at the CZL area. All excavated contaminated soil was placed in the 14-acre AV consolidation area (Figure 2). The overall goal ofthe project was to cleanup OUS AV/CZL sites to at or below the SALs prescribed in the ROD. Upon completion ofthe prescribed remedy in the constraction documents, confirmatory soil sampling for the COCs was conducted. The soil in the excavated areas met SALs after initial and additional excavation, if necessaiy, with minor exceptions. Concentrations of arsenic in soil in four areas remained above action levels. All four areas are located in the AV site: Area 3A, Area 3B, Area 3E, and Area 4 (Figure 3). Subareas 3A & 3B were backfilled with a minimum of 12 inches of borrow soil, subarea 3E was backfilled with a minimum of 6 inches of borrow soil, and Area 4 was backfilled with a minimum of 2 feet of borrow soil, as directed by the EPA RPM. Average concentrations ofthe COCs for the entire AV site are below the SALs for the COCs.

Environmental sampling and analysis was conducted in accordance with EPA guidelines and the CQAP (PWT 2009b). Soil sample results for both the AV and CZL areas are included in Appendix A. Real­time air monitoring for total suspended particulates (TSP) was conducted daily using a MiniRAM® during constraction activities. Air monitoring results never exceeded action levels. All sampling methods and data were verified and 20 percent were validated.

Excavation on site was performance based. AV and CZL areas had to be excavated to different depths per the constraction drawings. The resident field engineer (RFE) field-verified excavation depths. In addition, pre- and post-excavation surveys were conducted on the individual areas. Survey data were independently reviewed by PWT's project engineer to verify soil depths. The AV consolidated area was field-verified by the RFE, and survey data was verified by PWT's project engineer to ensure that final grading provided positive drainage.

The final cover ofthe AV consolation area required positive drainage and an 18-inch thick cover of screened borrow soil. Cover soil particle size was field-verified throughout the screening process by the RFE. Soil depth thickness on the cover was confirmed on site by the RFE and confirmed by PWT's

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project engineer based on pre- and post constraction surveys preformed by the subcontractor. Density testing (ASTM D-2922 and ASTM D-698) was performed on the placed cover soil at a frequency of every 1.5 acres by the Remediation Subcontractor, and wimessed by the RFE. All density tests results were above the required density requirements. The control swale, ditches, and drainage stractures were constructed per the constraction documents. All water diversion feature materials and grading was verified by RFE.

5.0 FINAL EVSPECTION AND CERTIFICATIONS

Informal prefinal inspections were conducted on all areas as excavation and other constraction activities were completed in individual subareas. Punch-list items identified as part of these prefinal inspections were addressed as constraction progressed.

A final site inspection was completed on October 23, 2009. The EPA RPM, PWT's project manager (PM), RFE, and the remediation subcontractor were present for the final inspection. At the time ofthe final inspection no items were found that required resolution. EPA accepted the work as complete. The Remedial Action Inspection form is presented in Appendix B.

Health and safety was a major concem for the project. PWT, the remediation subcontractor, all other subconfractors, and all other personnel were required to follow the provisions in their respective HASPs (on file at PWT). During the 2009 constraction activities no health and safety incidents, lost time accidents, or near-misses were recorded.

6.0 OPERATION & MAINTENANCE ACTIVITES

This section presents a brief outline of recommendations for long-term operation and maintenance (O&M) ofthe remedy, including cover-system inspection and maintenance, non-cover remediation area inspection and maintenance, surface-drainage confrols inspection and maintenance, and groundwater monitoring and institutional controls (ICs).

Recommendations for O&M for the consolidation area are summarized in Section 6.1 below. However, the non-cover areas that were remediated as a part ofthe remedial action for OUS project should also be inspected. The run-on and run-off control features associated with the AV and CZL sites should be inspected periodically. Visual inspection should be conducted of all drainage ditches, berms, chutes, swales, channels, and culverts to verify operation, capacity, and the effectiveness of erosion control measures.

6.1 Cover System Inspection and Maintenance

The primary exposure-pathway barrier for the AV consolidation site is an 18-inch soil cover. In addition, flue dust materials are contained within a fully encapsulated geomembrane liner, covered by between 4 and 8 feet of nonresidential area soils, and the final 18-inch clean soil cover. The boundary ofthe repository is represented by the flue dust monuments as shown on Figure 2. The soil cover should be inspected for indications of excessive differential settlement, erosion, cracking, sloughing, ponding, or other potential problems that may affect the integrity or performance ofthe cover system. The success of vegetation efforts should also be assessed.

6.2 Institutional Controls

The ROD requires implementation of ICs as a component ofthe remedy to provide notification that a barrier is in place, and to restrict land use to protect the integrity ofthe remedy in the cover areas (EPA 2000). It is understood that the EPA, Colorado Department of Public Health and Environment (CDPHE) and Lake County Commissioners are working to develop ICs for the Califomia Gulch OUS AV/CZL sites.

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D

6.3 Groundwater and Surface Water Monitoring

An element ofthe ROD remedy is to establish a long-term monitoring program to assess the quality of surface water and groundwater following implementation ofthe remedy (EPA 2000). Three groundwater wells (one upgradient and two downgradient ofthe repository) were installed by MFG and extended by PWT (Figure 2). Groundwater and surface water for the overall Califomia Gulch Superfund sites were included within a separate operable unit, 0U12. Any groundwater and surface water monitoring requirements for OUS should be integrated with monitoring requirements for OUl2.

7.0 SUMMARY OF PROJECT COSTS

The ROD identified the estimated remedy capital cost of approximately $2.85 million. Work performed in 2009 under the PWT contract was approximately $1.5 million. The cost for RA work performed in previous years by Asarco is not public information.

8.0 FIVE-YEAR REVIEW

Because the contaminated tailings, flue dust, and non-residential area soils will remain on site, the Selected Remedy requires a five-year review under Section 121 of CERCLA, and Section 300.430(f)(4)(ii) ofthe National Contingency Plan. The five-year review includes a review ofthe groundwater and surface water monitoring data and an evaluation as to how well the Selected Remedy is '-' achieving the RA objectives and applicable or relevant and appropriate requirements (ARARs) that it was designed to meet.

9.0 OBSERVATIONS AND LESSONS LEARNED

The presence of previously stockpiled borrow soil on top of previously consolidated contaminated soil and within the consolidation area created placement issues for the additional contaminated soil that needed to be placed within the consolidation area, survey issues to properly document the top ofthe consolidated soil surface and thickness of soil cover; and logistical issues with respect to sequencing of consolidation, cover placement, and surveying. When work is conducted at a project over multiple years, it is important to consider how current actions, which may need to be taken immediately because of schedule constraints, affect the overall plan for execution ofthe work though completion ofthe project.

10.0 OPERABLE UNIT CONTACT INFORMATION

• Stan Christensen, EPA RPM. US EPA Region EPR-SR 1595 Wynkoop Street Denver CO 80202-1129 Christensen.Stanley@epa.gov (303) 312-6694 phone (303)312-7151 fax

• Levi Todd, P.E., Project Manager Pacific Westem Technologies, Ltd. 11049 West 44* Avenue Suite 200 Wheat Ridge CO 80033 LTodd@pwt.com (303) 274-5400 x48 phone

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(303) 274-6160 fax

• Rick Anacleto, Remediation Subconfractor Platinum Environmental, LLC 401 West County Road 16 Loveland CO, 80537 (970)-669-2277 phone (970)-669-2382 fax

11.0 REFERENCES

MFG, Inc. 2005. Final Remedial Design Report, Arkansas Valley Smelter and Colorado, Zinc-Lead Mill Site, California Gulch Superfund Site. April.

MFG, Inc. 2006. Construction Status Report, Operable Unit 5, Arkansas Valley Smelter and Colorado Zinc-Lead Mill Site Califomia Gulch Superfund Site, Leadville, Colorado. December.

Pacific Westem Technologies, Ltd. (PWT). 2009a. California Gulch Operable Unit 5, Arkansas Valley Smelter and Colorado Zinc-Lead Mill Site, Remedial Action, Construction Package. June.

Pacific Westem Technologies, Ltd. (PWT). 2009b. Califomia Gulch Operable Unit 5, Arkansas Valley Smelter and Colorado Zinc-Lead Mill Site, Remedial Action, Construction Quality Assurance Plan. July.

Tetra Tech. (TT), January 8,2008. Technical Memorandum to Asarco, LLC. California Gulch Superfund Site, OUS - A V Smelter Site and CZL Mill 2008 Construction Activities.

U.S. Environmental Protection Agency (EPA). 2000. Record of Decision - Operable Unit 5, A V/CZL Sites, California Gulch Superfund Site, Leadville, Colorado. September.

RA report 009-RARA-0829 Final rev 1 9 February 23, 2010

RA Report, Rev. 1

r

Figures

n

u

U r

RA report 009-RARA-0829 Final rev 1 February 23, 2010

RA Report, Rev. 1

h APPROXIMATE ALIFORNIA GULCH

r OUS. AV/CZL v BOUNDARY / '

]

2000 ft

] /TACIRCWESTERNTECHNOLOGES.LTD. 11049 West 44th Avenue, Suite 200

Wheat Ridge, CO 80033 303-274-5400 WWW.PWT.COM

SITE LOCATION MAP CALIFORNIA GULCH OPERABLE UNIT 5

AV/CZL SITES LEADVILLE, CO

FIGURE 1

NO. I BY IDATEibtefct^lPTIOTT PROJECT:

California Gulch OUS 0 ^ B^TGNED BY:

I-12-2Q1

APPR6VED BY:

201C

n L

LEGEND:

2009 DESIGN EXCAVATION AREAS

2009 DESIGN AREA NOTATION

CONFIRMATORY SAMPLING DESIGNATION

ASARCO EXCAVATION AREAS PRIOR TO 2009 CONSTRUCTION ACTIVITIES NOT REQUIRING ADDITIONAL EXCAVATION

5

® * CONCENTRATIONS OF ARSENIC IN THESE DESIGNATED AREAS EXCEEDED THE SOIL ACTION LEVELS AT THE FINAL EXCAVATION DEPTH. THESE AREAS WERE BACKFILLED WITH BORROW SOIL TO A DEPTH OF 6 TO 24 INCHES.

/PACIFIC WESTERN TECHNOLOGIES, LTO.

11049 West 44th Avenue, Suite 200 Wtieat Ridge, CO 80033

303-274-5400 WWW.PWT.COM

AV EXCAVATION AREAS

CALIFORNIA GULCH OPERABLE UNIT 5

AV/CZL SITES LEADVILLE, CO

NO. BY I DATE I DESCRIPTION PROJECT:

California Gulch OUS DATE: DESIGNED BY:

1-12-2010

APPROVED BY: JMB j j m

200 ft

FIGURE 3

APPROXIMATE CALIFORNIA

GULCH OUS, AV/CZL

BOUNDARY

/ y

/

LEGEHD:

EXCAVATED FLUVIAL TAILING AREA

EXCAVATED TAILINGS AREA

EXCAVATED SLOPE AREA

SAMPLING AREA BOUNDARY

SAMPLING AREA DES/GNATION

EXCAVATION CRITERIA:

SAL

VISUAL TAILINGS

VISUAL TAILINGS

CZL-E1

N

NOTE: SOIL IN SAMPLING AREAS CZL-W2, CZL-W5, CZL-E2 AND CZL-E6 CONTAINED CONCENTRATIONS OF COCs ABOVE SALs. EXCAVATION IN THESE AREAS WERE FIELD FIT AROUND EXISTING MILL STRUCTURES. EXCAVATION IN CZL-E3 OCCURRED AS A RESULT OF PUSHING CONTAMINATED SOIL FROM CZL-E6 DOWNSLOPE.

11049 WMt 44tti AMiHit. Sulta 200 WhMtRMo*. CO 80033

303-274-6400 WWW.PVIT.COM

CZL EXCAVATION AREAS 2009

CALIFORNIA GULCH OPERABLE UNIT 5 AV/CZL SITES LEADVILLE, CO

NO. I BY I DATE I DESCRIPTTON PROJECT:

California Gulch OUS DATE: DESIGNED BY:

1-12-2010

APPROVED BY: TWR JM

100 ft

FIGURE 4

BORROW AREAS

LEGEND:

NO REVEGETATION

AREA WITH A MINIMUM 6" SOIL BACKFILL & STANDARD SEED MIX

AREA WITH NO SOIL AMENDMENT & STANDARD SEED MIX

AREA WITH LIME SOIL TREATMENT & STANDARD SEED MIX

AREA WITH A MINUMUM 6" SOIL BACKFILL & DITCH SEED MIX

AREA WITH SOIL BACKFILL & DITCH SEED MIX

AREA WITH A MINIMUM 6" SOIL BACKFILL & WETLAND MIX

OVERSIZED ROCK AREA

^ii'^.)i:-y.ii

11040 WMt 44lh AvMwa. Suttt 200 WhMtRMga. CO 80033

303-2744400 WWW.PWr.COM

REVEGETATION/SOIL AMENDMENT AREAS CALIFORNIA GULCH OPERABLE UNIT 5

AV/CZL SITES LEADVILLE. CO

NO.I BY IDATE IDESCRIPTRUR

PROJECT: California Gulch OUS

PATE; DESIGNED BY:

1-12-2010 APPROVED BY:

J3/ffi Am

300 ft

FIGURE 5

Appendix A

Soil Analytical Results

RA report 009-RARA-0829 Final rev 1 February 23, 2010

RA Report, Rev. 1

Arkansas Valley Site - Soil Analytical Results

Pre-Excavation AV Area Sample ID AVI AV 1-02 AV5E AV5W AV6

Date Sampled 7/9/2009 7/9/2009

7/10/2009 7/10/2009 7/10/2009

Arsenic 448 341 204 45.9 36.8

Lead 5,830 5,020 2,510 128 205

Post-Excavation AV Area Sample ID AV4 AV4 AV2A AV 2A-02 AV2B AV 2B-02 AV2C AV2D AV2E AV2F AV2G AV2H AV2I AV2J AV2K AV3A AV3A AV3B AV3B AV3C AV3D AV3E AV 3 E-02 AV3E BORROW 1 BORROW 2

Date Sampled 8/17/2009 9/15/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/18/2009 8/27/2009 9/3/2009 8/27/2009 9/15/2009 8/27/2009 8/27/2009 8/27/2009 8/27/2009 9/15/2009 8/27/2009 8/27/2009

Arsenic 1,300 770 4.86 3.55 12.8 15.2 4.01 6.94 26.8 116 9.54 112

33.3 100 30

2,010 1,460 1,570 1,1 70

491 257

2,020 2,100 428 182 113

Lead ND 249 81.7 58 150 221 32.8 • 52.5 279 330 284 1,330 104

1,030 152

1,090 183 767 137 131 72.9 310 386 99.2 1,180 621

Notes: 1. See Figure 3 from sampling areas 2. Each sample generally was a composite of four subsamples form the sampling area.

Specific subsample locations are in the project files. 3. All samples are expressed in mg/kg 4. All items identified in red are above Soil Action Levels

Page 1 of 1

Colorado Zinc Lead Site - Soil Analytical Results

Pre-Excavation CZL Area - Discreet Screening Samples Sample ID CZLl CZL 2 CZL 3 CZL 4 CZL 5 CZL 6 CZL 7

Date Sampled 7/9/2009 7/9/2009 7/9/2009 7/9/2009 7/9/2009 7/9/2009 7/9/2009

Arsenic 30.2 621 22.3 86 160 274 86.6

Lead 1,730 9,670 624

1,180 5,600 6,180 1,190

Pre-Excavation CZL Area - Com Sample ID CZL E-1 CZL E-2 CZL E-3 CZL E-4 CZL E-5 CZL E-6 CZL W-1 CZL W-1-02 CZL W-2 CZL W-3 CZL W-4 CZL W-5 CZL W-6

Date Sampled 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009 8/3/2009

posite Samples Arsenic

80.3 152 64.1 53

30.8 135 129 160 145 257 125 23.5 85.2

Lead 3,750 10,900 1,340 1,550 4,590 7.550 4,630 5,720 8.220 5,460 2,780 14,400 4,230

Post-Excavation CZL Area Sample ID CZL S-B CZL Slope-E CZL Slope-W

Date Sampled 9/1/2009 9/8/2009 9/8/2009

Arsenic 93.3 33.8 26.4

Lead H.\W 1,120 1,240

Notes: 1. See Figure 4 from sampling areas 2. Each sample generally was a composite of four subsamples form the sampling area.

Specific subsample locations are in the project files. 3. All samples are expressed in mg/kg 4. All items identified in red are above Soil Action Levels. 5. CZL S-B is a sample collected from the bench ofthe CZL slope.

Page 1 of 1

Appendix B

Final Remedial Action Inspection Form

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RA report 009-RARA-0829 Final rev 1 February 23, 2010

RA Report, Rev. 1

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CtaUfomia Guich OV5 Arkansas Vallcy/Colonido,2%i6 Lead Sitss

Lain Covniy* Colondo

Final RaniMilai Aciion Inspection bGtDlier.23,20a9

AiElMly

ftiinpllniawl analywsitf Atfaniw^vaMwiiibawM 15,6 Excavation of AVsubaraas odntaMniKGoiioenftratipm of faad brarranic

•nwlar tJwn sctftw teweb

RamadM Action J Canmhiad?

Yes Yes

Cpnllnnatory wmpHngand aiialwesirf AVsufaeas t Si and4 Ad»BtlonalwgawattirfcfiWsiifcWBM.9iind>r

ConsoHdattenofeMBwaiBdAVaoBliiconwiMatlonaiea Stwenftitt ofMocfcplled cewaoll

Hacamentaf ttrliich aoii^

Yes ves Yes Yes

ConnnictionofteimandiHwIeoncow Gonstructton of AV iMnminterninoq/ifundf control inteii, Including

InttallalioniBftwfDadMefts SaiamllBt antf-anahieesaf'Ca.ilope

Yes Yes ves

Yes Buavatlon of GEL subaraas containing eoheentfttlons of (aad or

anenlfriTBalierthin action tewh ConflrnBaterywmpHng end analwes of WBawatrtiCa. areas

AtfWonal^vaBonofCaa.wdiaieBS'

-

Ekcawatlon of catamnss area based on visual obserwattons

Yes

Yes

Yes BackBII of ca.talBnis awe to ftcilltala dralnega

AironbmlcsainpllBgefAVandClLeieas Mitigation of low pH aoAs by Ome amendnieht or placemiint of 6-Inch

lift of bonow soil .,

Yes Ves

L

Rev^talion of AV and OL areas iHsturiiad during 2009 and previous vears

Biuipnient demobilliBd and sltia cleaned up

Yes

Yes

Yes 1.

2.

SoU oontalnhv imric •bow ictloin tavais Wis taft th plice III M M 4and porttom of Aiea 9 at a depth tf or mom bataw itaitfni |iaA. Thate araas wail biGlMted with C I n ^ or mam of irarfew MIltmialaaitflmiatlonareaplhofaallcBMrwasMaHlMrnaairanlplHestaeai^ rMfMibili Iwfna andiftw p!|pm«^ aiid sehedi*fer oampMbig tfniafvrriMunNiy. Soli eoiitalplng laad afaoimelM tavali was laft In place In tha 'upper barnih area" or GZl. Onafbbt ef bomw

llnthlsi

PWT

Platlnuni

Appendix C

Stamped As-Built Survey

RA report 009-RARA-0829 Final rev 1 February 23, 2010

n h RA Report, Rev. 1

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