2015-11-18_-_Final_2015_KMS_Characterization___Removal_Report_0001.pdf

Site Characterization and Limited Soil Removal Report Kolmakof Mine Site, Alaska

Brice Environmental Project Number: BE1501

November 2015

Prepared for:

Bureau of Land Management

SITE CHARACTERIZATION AND LIMITED SOIL REMOVAL

REPORT, KOLMAKOF MINE SITE, ALASKA

Prepared for:

Bureau of Land Management Alaska State Office 4700 BLM Road

Anchorage, AK 99507-2591

This document has been prepared by Brice Environmental Services Corporation. The material and data in this report were prepared under the supervision and direction of the undersigned.

Carl Benson Environmental Scientist

Craig Jones President

2015 Kolmakof Mine Site Characterization Report November 2015

CONTENTS

ACRONYMS ................................................................................................................................ iii

1 INTRODUCTION...............................................................................................................1-1

1.1 Site Description .....................................................................................................1-1

1.2 Site Background ....................................................................................................1-2

1.3 Project Objectives .................................................................................................1-3

2 REGULATORY CRITERIA ...............................................................................................2-1

2.1 Soil Regulatory Criteria .........................................................................................2-1

3 FIELD ACTIVITIES ...........................................................................................................3-1

3.1 Mobilization ...........................................................................................................3-1

3.2 Excavation and Characterization Activities ...........................................................3-1

3.2.1 Field Screening .......................................................................................3-2

3.2.2 Soil Confirmation Sampling ....................................................................3-3

3.2.3 Soil Containerization and Transport .......................................................3-3

3.2.4 Demobilization ........................................................................................3-4

3.3 Quality Assurance and Quality Control .................................................................3-4

3.4 Waste Management ..............................................................................................3-4

4 FIELD SCREENING AND ANALYTICAL RESULTS .......................................................4-1

4.1 Excavation Sampling Results ................................................................................4-1

4.1.1 Mill Area (IA-2)........................................................................................4-1

4.1.2 Retort Mound Area (IA-1) test Pits ..........................................................4-2

4.1.2.1 Analytical Data Quality ..........................................................4-3

5 CONCLUSIONS AND RECOMMENDATIONS ................................................................5-1

5.1 Conclusions...........................................................................................................5-1

5.1.1 Mill Area (IA-2)........................................................................................5-1

5.1.2 Retort Mound Area (IA-1) .......................................................................5-1

5.2 Recommendations ................................................................................................5-2

5.2.1 Mill Area (IA-2)........................................................................................5-2

5.2.2 Retort Mound Area (IA-1) .......................................................................5-2

6 REFERENCES..................................................................................................................6-1

FIGURES

Figure 1 Site Location Map

Site OverviewFigure 2 Figure 3 Top of Mill Area (IA-2) Excavation Diagram Figure 4 Retort Mound (IA-1) Test Pit Sampling Results Diagram i

CONTENTS CONTINUED

TABLES

Table 1 Soil Sample Analytical Results

APPENDICES

Appendix A

Field Log Book Appendix B Project Photographs Appendix C Laboratory Analytical Data Reports Appendix D ADEC Checklists and Quality Assurance Report Appendix E Records of Disposal Appendix F Sample Location Survey Data ii

ACRONYMS

°C degrees Celsius

AAC Alaska Administrative Code

ADEC Alaska Department of Environmental Conservation

AK Alaska Method

ATV all-terrain vehicle bgs below ground surface

BLM Bureau of Land Management

Calista Calista Corporation

COC constituent of concern

DRO diesel range organics

EE/CA engineering evaluation / cost analysis

E&E Ecology & Environment

J indicates an estimated quantity

KMS Kolmakof mine site

LOD limit of detection mg/kg milligrams per kilogram

MS matrix spike

MSD matrix spike duplicate

NAC Northern Air Cargo

PA/SI preliminary assessment/site investigation

PID photoionization detector

QAR quality assurance review

QA/QC quality assurance/quality control

RPD relative percent difference

RSD relative standard deviation

RSI removal site inspection

SGS SGS North America, Inc.

TKC The Kuskokwim Corporation

UCL upper confidence limit

USEPA U.S. Environmental Protection Agency

XRF X-ray fluorescence analyzer iii

1 INTRODUCTION

During the summer of 2015, Brice Environmental Services Corporation (Brice) conducted characterization, excavation and transport and disposal activities in association with the former Kolmakof Mine Site (KMS or Site) near Aniak, Alaska (Figure 1). These activities were performed under a work plan prepared in May, 2015 (Brice, 2015).

1.1 SITE DESCRIPTION

The KMS is an abandoned cinnabar mine on the north bank of the Kuskokwim River. The site is located approximately 19.5 miles east of Aniak and approximately 10 miles west of Napaimute, Alaska, (the nearest known inhabited area). The legal description for the KMS is:

North ½, Section 6, Township 17N, Range 53W, Seward Meridian, Alaska. A small, unnamed creek passes by portions of the site and flows into the Kuskokwim River near the Camp Area portion of the site (Figure 2). There are no roads to the site or aircraft landing strip nearby;

access is by boat only.

The mine has three developed areas: a “Camp Area” on the bank of the Kuskokwim River; an upland “Mill Area”; and an open-pit/surface stripping mining area on the bluff above the river where waste rock was dumped down the bluff onto the river bank. The Camp Area is approximately 1.75 miles from the Mill Area. (Figure 2). The two areas are connected by a dirt road which parallels an unnamed creek that drains directly into the Kuskokwim River. From the Mill Area, the road continues uphill to the Mine Pit. Since the mine closure, the KMS became overgrown with vegetation and the roads narrowed to foot paths. During the 2006 BLM site inspection, the Mill Area was found to contain a collapsing ball mill structure with water flowing under and through it. Two sheds were found nearby, one containing about a dozen metal bottles which appeared to be empty mercury flasks. USEPA correspondence to BLM had mentioned a retort operation at the “upper camp” so it was assumed that the flasks indicated that the shed may have housed a retort or that one was nearby. Photos taken during the 2000 BLM site visit showed the larger shed housed an electric generator that had been removed by persons unknown by the 2006 BLM site visit. Numerous empty drums and fuel cans were found scattered around both inside and outside the sheds. The unnamed creek formed a small pond a few feet from the mill, and the source of the creek was reported to be water coming to the ground surface above and around the mill building from the steep hillside/berm immediately adjacent. An old pickup truck was found abandoned a short distance away. The former dynamite shed was represented by a pile of ash and burned metal debris. No evidence of spills, stains, odors or distressed vegetation beyond the ash at the former dynamite shed was noted by BLM. It also appeared that waste rock and tailings were dumped over the bluff into the Kuskokwim River from the mill building and the mining pit areas uphill and behind the river bluff.

The Camp Area structures were observed by the BLM to be deteriorating and contained a significant volume of discarded household debris. The remnant of a potential mercury retort, consisting of a metallic beer keg secured to rotting wood beams was found near the Camp Area. A firebrick pit was found located adjacent to the keg.

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1.2 SITE BACKGROUND

The KMS is an abandoned cinnabar (mercury ore) mine on the North Bank of the Kuskokwim river near the village of Napaimute, Alaska, and is scheduled to be conveyed to The Kuskokwim Corporation (TKC) (surface estate) and Calista Corporation (Calista) (subsurface estate) in accordance with the Alaska Native Claims Settlement Act. Until conveyance, the land is administered by the U.S. Bureau of Land Management (BLM). A preliminary assessment/site investigation (PA/SI) was initiated by the United States Environmental Protection Agency (USEPA) in 1999, and two site inspections and removal actions were conducted by the BLM in 2000 and 2006. A Removal Site Inspection (RSI) was subsequently performed by Ecology and Environment, Inc. (E&E) in 2007 to identify facility features, inventory abandoned mine-related equipment and debris, and identify contaminants requiring possible remediation and or removal prior to transfer of the land to TKC and Calista. The RSI identified mercury as the primary contaminant of concern and identified the need for further investigation to further characterize the site for metals, petroleum hydrocarbons, and explosives, as well as the need for characterization and removal of hazardous and non-hazardous site materials. The RSI identified four areas of concern (AOC) within the site: Camp Area, Mill Area, Mine Pit, and Waste Rock/Tailings Dump Areas.

MACTEC Engineering and Consulting Inc. (MACTEC) conducted initial investigative removal activities in 2008, including metal background concentration investigations, a geophysical survey for a potential mono-fill location, explosives residue sampling, mercury speciation analysis, and an asbestos and lead-based paint survey. Field activities included removal and disposal of various hazardous and non-hazardous materials from abandoned waste containers and equipment.

In 2011, AMEC Environment & Infrastructure (AMEC, formerly MACTEC) prepared an Engineering Evaluation/Cost Analysis (EE/CA) work plan to complete site characterization activities required to delineate the extent of remaining contamination in each of the areas of concern (AOC) (AMEC, 2011). Field work including investigation of metals, petroleum hydrocarbons, and other contaminants of concern as well as a biological survey was conducted between September 25th and October 1st, 2011.

The EE/CA, completed in 2012 and subsequent 2013 Removal Action Memorandum identified oil, hazardous substances, and non-hazardous solid waste removal actions that were warranted within the mill, mine pit, and camp areas. The EE/CA results showed that removals of constituent of concern (COC) metals-contaminated soils were warranted in Investigation Areas (IAs) IA-1, IA-2, IA-3, IA-4, IA-5, IA-6, IA-8, and IA-13. IA-8 also required DRO impacted soil removal. Hazardous substances to be removed included mercury, arsenic, and chromium in soil as the contaminants of concern in both the Camp Area and the Mill Area, and localized petroleum hydrocarbon contamination of soil in the Mill Area (IA-8 only). Non-hazardous solid waste located within the Mine Pit, Mill Area, and Camp Area required removal as well (AMEC, 2012).

In 2012 BLM contracted with Brice to conduct Limited Removal Actions at the KMS during the 2013 field season. During the 2013 field season, Brice removed all camp buildings, infrastructure, and waste materials. Limited excavation was performed during the 2013 field activities to remove metals and fuel-contaminated soil in the areas noted in the EE/CA. Soil sampling analytical results indicated closure was obtained at all areas except IA-1 and IA-2. A

1-2 total of 46 cubic yards of COC metals-contaminated soil (including cinnabar residue from decontamination) was removed from IA-2, IA-3, IA-5, IA-6, and IA-8 of the Mill Area. An additional 14 cubic yards were removed from IA-1 at the Camp Area. This material was loaded into supersacks and transported off site for proper disposal. A landspread area was constructed with 23 cubic yards of DRO-impacted soil from IA-8. Initial baseline DRO concentrations were documented for the landspread area. Initial sampling of the landspread area indicated DRO concentrations exceeding the cleanup level of 250 milligrams per kilogram (mg/kg) and continued sampling was warranted. A landspread area maintenance and sampling and analysis plan was developed to formalize continued operation of the landspread area (Brice, 2014a).

In 2014, BLM contracted with Brice to conduct additional removal at the KMS during the 2014 field season. Brice prepared an addendum to the work plan used for the Limited Removal Actions performed in 2013 to plan the 2014 field activities (Brice, 2014b). During the 2014 season, Brice removed 6 cubic yards of soil from the site at the Upper Mill Area (IA-2) and 94 cubic yards of soil from the Retort Mound (IA-1). Confirmation sampling conducted at IA-2 indicated exceedance of the Alaska Department of Environmental Conservation (ADEC) cleanup level for mercury along the northeast sidewall of the excavation, and exceedances of the cleanup levels for chromium and mercury along the southwest sidewall of the excavation.

Excavation confirmation soil sampling conducted at IA-1 indicated lateral exceedances of cleanup levels for mercury, arsenic, and chromium in soils surrounding the 2014 excavation area. Bedrock was encountered along the north and northeast walls of the excavation and further excavation in these directions should be limited to lateral removal to depths of placed material only. The presence of the firebrick platform, beads of elemental mercury, and buried burned ore suggest the retort facility described in the original PA/SI may be present in this area, but was buried by mine operations before the “beer keg retort” was placed there. Bedrock was encountered across the floor of the 2014 excavation limits at IA-1, and further removal of soil in this area is not warranted. Sampling results at the landspread area indicated DRO concentrations were reduced below the applicable cleanup level of 250 mg/kg and that final site closure had been met (Brice, 2014c).

1.3 PROJECT OBJECTIVES

The objectives of the work performed and discussed in this report include:

Removal of up to 14 cubic yards of soil in 2-cubic-yard increments from the Upper Mill Area to meet ADEC cleanup levels established for this site; and

Advancing test pits and sampling soils in the immediate vicinity of the Retort Mound to re-characterize the distribution of arsenic, chromium, mercury, and nickel in this area.

Remove the balance of 14 cubic yards of soil from the Retort Mound if cleanup levels are met at the Upper Mill Area.

2015 Kolmakof Mine Site Characterization Report November 2015

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2 REGULATORY CRITERIA

ADEC regulations applicable to this project are contained in Title 18 of the Alaska Administrative Code (AAC), Chapter 75, Oil and Other Hazardous Substances Pollution Control (18 AAC 75), as updated on June 17, 2015 (ADEC, 2015).

2.1 SOIL REGULATORY CRITERIA

At the KMS, arsenic, chromium (total), mercury, and nickel have been identified as COCs.

Background sampling of AOCs determined that naturally occurring metal concentrations at some of the AOCs is higher than the ADEC’s most stringent action level (Method 2 Migration to Groundwater). For purposes of defining cleanup levels as they pertain to background metal concentrations, the AOCs have been divided into the Camp Area and the Mill Area. A summary of the action levels for COC metals at both of the AOCs is presented below:

Parameter Method Camp Area Soil Cleanup Level

(mg/Kg)

Mill Area Soil Cleanup Level

(mg/Kg)

Arsenic EPA Method SW6020 10.7 12.7

Chromium, (Total) EPA Method SW6020 29.2 30

Mercury EPA Method SW7471 1.4 1.99

Nickel EPA Method SW6020 86 53.9

Analytical results for arsenic, chromium, mercury and nickel were screened and evaluated using the site-specific cleanup levels calculated during the background study (AMEC, 2011) and ADEC Method Two, Table B1, Migration to Groundwater, whichever was greater for each metal.

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3 FIELD ACTIVITIES

A site visit was conducted on 2-4 June, 2015 to coordinate local labor and equipment in Aniak, and to inspect the ramp at the site to determine whether ramp improvement work would be necessary prior to commencement of field work. Based on observed site conditions, no ramp repair work was deemed necessary.

On June 15, 2015, Brice mobilized to the Site to load the barge for starting work on June 16, 2015. Field activities continued until demobilization on June 27, 2015. All activities were performed under the ADEC-approved work plan prepared in May, 2015 (Brice, 2015). BLM Project Manager Larry Beck performed Project Inspector duties on-site 15-25 June, 2015.

Field activities were recorded in a bound field logbook. A photocopy of the field logbook is presented in Appendix A. Photographs of field activities are presented in Appendix B.

3.1 MOBILIZATION

On June 15, 2015, Brice Site Superintendent Dennis Olson mobilized to Aniak to support equipment logistics for the work at KMS. Equipment, fuel, and materials were staged at the Aniak barge landing on June 15 for loading. On June 16, the loaded barge was driven up to the KMS. On June 16, the barge arrived at the KMS with the following gear:

Kubota® BX25 tractor with loader bucket and backhoe attachments

3-seat Polaris® XP-900 four-wheel-drive all-terrain vehicle (ATV)

5-gallon capacity fuel cans for additional equipment fuel

5-gallon capacity plastic buckets with lids and empty sand bags

1-fish tote with tools and supplies

14 Supersacks and pallets.

The Polaris® ATV, Kubota® tractor, and the tote of supplies was mobilized from Anchorage using Northern Air Cargo (NAC) prior to crew mobilization in June, 2015. All other equipment used on this project originated in Aniak. Brice mobilized one laborer and one equipment operator to the site on June 16, and the barge was unloaded at the KMS barge ramp. Minor ramp improvements were performed after landing to improve access to the barge.

3.2 EXCAVATION AND CHARACTERIZATION ACTIVITIES

Mill Area:

Excavation activities were conducted at the Mill Area (IA-2) on June 17, June 19, and June 23, 2015. On June 17, 2.6 cubic yards were excavated from the east and west sides of the 2014 excavation area until the only remaining sidewall was on the south side of the excavation.

Excavated soils were transported to the barge and containerized in supersacks. The excavation

3-1 was advanced to original grade as established in 2014 and then scraped another 2-inches prior to screening using the X-Ray fluorescence analyzer (XRF). The floor of the southwest side of the excavation was determined to be clean in 2014. Additional soil was removed and stockpiled on site pending receipt of analytical results. On-site stockpiling was performed to expedite soil removal because of the three-day turnaround time for analytical results. Five confirmation samples, including one quality control (QC) duplicate were collected and submitted for analysis on the afternoon of June 17. Brice remobilized to the Mill Area on June 19 and excavated an additional 3.4 cubic yards from the southeast and southwest portion of the Mill Area excavation.

Confirmation soil sample results from this area indicated mercury exceedance in the sidewall on the southeast side of the excavation. The stockpiled material from June 19 was moved to supersacks on the barge on June 22 and June 23, 2015 and an additional 4 cubic yards were excavated from floor and wall of the southeast area. Two cubic yards were transported to the barge and 2 cubic yards were stockpiled pending analytical results for samples collected on June 23. Analytical results for samples collected on June 23 indicated soil cleanup levels had been met and the final two cubic yards of soil were transported to supersacks on the barge. In all, ten cubic yards of soil were removed from IA-2 in 2015. Figure 3 shows final 2015 excavation limits and final sampling locations at the Mill Area with respect to limits of excavation during work conducted in 2014. Photographs of the excavation work are presented in the photo log in Appendix B.

Retort Mound Area:

Soil characterization and removal activities were conducted at the Retort Mound Area (IA-1) from June 18 through June 25, 2015. Characterization activities at IA-1 commenced on June 18 with the excavation of four test pits, and one step-in test pit, located radially around the retort mound area. Three of these test pits, pits 1 through 3, were sampled on June 18. In addition,

1.5 cubic yards of soil within the area known to be contaminated were excavated and bagged on the barge. On June 19, the remaining four test pits, pits 5 through 8, were installed and sampled, with the exception of Test pit 4, around the retort mound area to comprise the first full set of characterization test pits surrounding the retort mound. Test pit 4, installed on June 18th, was sampled on June 23rd. An additional 1.5 cubic yards of soil were excavated from IA-1 and containerized on the barge. Analytical results from the first set of test pits were available on June 23 and a set of step out pits were installed and sampled on June 24th. Test pit depths ranged from 14” at Test Pit 7 to 48” at Test Pit 3 (Figure 4). One final cubic yard of soil was removed from IA-1 on June 25 to complete contracted soil removal quantities.

A total of four cubic yards of soil were excavated from IA-1, transported to the barge and bagged for transport to Aniak. Bedrock or native clay soil was encountered at the total depth of all test pits. Figure 4 shows the location of test pits excavated during 2015 characterization work conducted at IA-1. Photographs of a typical test pit is presented in the photo log in Appendix B.

3.2.1 FIELD SCREENING

Soil was screened using both visual observation and an XRF. Field screening samples were screened in-situ at the frequency and locations as described in Table 2B of the “Draft Field Sampling Guidance” (ADEC, 2010). A minimum of 10 screening samples were collected from the first 250 square feet and a minimum of one screening sample per each additional 100 square feet of excavated area was collected. Sidewall samples were collected at a minimum rate of one sample per 10 linear feet for excavations greater than three inches depth below

3-2 ground surface. Samples were collected directly from the excavation footprint. Test pits were screened at each depth indicating a visual change in soil type or suspected COC metals contamination as indicated by color.

Soil was screened for arsenic, chromium, mercury and nickel using a handheld XRF analyzer as well as visual observation of the red cinnabar-impacted soil. The Thermo Scientific Niton® Model XL3t 600 XRF was used according to SW-846 Method 6200 for in-situ field screening analysis (USEPA, 2007). This unit has limits of detection (LOD) below the action levels for arsenic, chromium and nickel; however, the lowest anticipated LOD for mercury with this instrument was approximately 5 parts per million (ppm) which is above the mercury cleanup level of 1.4 mg/Kg for the Camp Area and 1.99 mg/Kg for the Mill Area. None of the XRF instruments available on the market can attain sensitivity down to 1.4 ppm. Therefore, a non-detect reading for mercury did not confirm that mercury cleanup levels had been achieved.

Confirmation soil samples for COC metals analyses were collected from the locations where XRF field screening results indicate both non-detect for mercury and the highest levels of arsenic and chromium.

3.2.2 SOIL CONFIRMATION SAMPLING

Following soil removal, confirmation soil sampling was conducted within each excavation footprint. Soil confirmation samples were collected and screened per the frequency described in the work plan. For the excavation area at IA-2, a minimum of two confirmation samples plus one duplicate sample were collected from the first 250 square feet of excavation floor and one sample per each additional 250 square feet of excavation. Sidewall confirmation samples were collected within the excavation footprint at a minimum frequency of one sample per 20 linear feet. Confirmation samples were collected from the locations yielding the highest field screening results for the COCs within each excavation area. Test pit characterization samples only were collected at IA-1.

Confirmation and characterization soil samples were collected in amber jars and placed into coolers with frozen gel packs at the site. Four sets of confirmation soil samples were transported to Anchorage via air cargo and submitted to SGS on June 18, June 20, June 24, and June 26, 2015. Analytical results were compared to the cleanup levels established for the site as shown in Section 2.

Field duplicate samples were collected for field precision evaluation at a rate of one per 10 soil confirmation samples collected. Sampling protocols, sample handling, custody, and transporting procedures followed those specified in the work plan.

3.2.3 SOIL CONTAINERIZATION AND TRANSPORT

Following excavation, soils were either temporarily stockpiled to await sample results or directly loaded into sand bags or 5-gallon buckets for transport via ATV to the barge deck where they were transferred to palletized 1-cubic-yard supersacks. Initial sand bags and buckets were weighed so each supersack would not be filled over its 2,200-pound rated capacity. Following loading, the soils were shipped via barge transport under non-hazardous waste manifest to Aniak. Upon arrival in Aniak, the supersacks were loaded onto a flatbed trailer and transported to the Aniak Airport. The soils were weighed again at the airport and loaded onto aircraft

3-3 operated by Northern Air Cargo for transport to Anchorage. Transport continued from Anchorage to the Port of Seattle via barge, and then via rail to the Columbia Ridge landfill in Arlington, Oregon. The 14 sacks were shipped under non-hazardous waste manifests to the Columbia Ridge disposal facility. Photographs of the field process to containerize soils are presented in Appendix B.

3.2.4 DEMOBILIZATION

The load of 14 supersacks were barged downriver from the site to Aniak with all project equipment on June 26, 2015. Grading and reseeding of the mill and camp areas were also completed on June 26. The Brice Site Superintendent left Aniak for Fairbanks on June 27, 2015.

The Polaris® ATV and Kubota® tractor were flown back to Anchorage on June 29, and July 6, respectively.

3.3 QUALITY ASSURANCE AND QUALITY CONTROL

Quality assurance/quality control (QA/QC) procedures were maintained throughout the sampling activities. QA procedures included the analysis of field duplicates and preparation of a laboratory data QA review (QAR) by qualified Brice staff. The QAR included the completion of an ADEC Laboratory Data Review Checklist for each analytical report included in Appendix C.

QC procedures included adherence to appropriate sample collection methodology as described in Brice’s ADEC approved work plan (Brice, 2015). Any discrepancies associated with the soil confirmation samples collected from the Site were identified in the QAR (Appendix D) and are summarized in Section 4.1.2.1.

3.4 WASTE MANAGEMENT

Facility-signed non-hazardous waste manifests returned from the Columbia Ridge landfill are presented in Appendix E as documentation of proper disposal of all 14 sacks of soil removed from the KMS in 2015. All soils excavated in 2015 were transported and disposed of under facility-approved waste profiles developed for the soils from the same AOCs in 2013 and renewed by the receiving facility in 2014.

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4 FIELD SCREENING AND ANALYTICAL RESULTS

This section describes the findings of sampling conducted in support of the 2015 removal action and characterization performed at the KMS. The nomenclature for sample IDs and AOCs for this project are defined below:

15KTM = 2015 Sample from Kolmakof Top of Mill (IA-2)

15KRM = 2015 sample from Kolmakof Retort Mound (IA-1)

Field notes included in Appendix A provide a detailed account of the field screening and sampling activities conducted at the Site. The following sections detail the results for sampling conducted at each area at KMS in 2015.

4.1 EXCAVATION SAMPLING RESULTS

The following sections discuss findings of excavation and test pit sampling activities from the Mill Area (IA-2) and the Retort Mound Area (IA-1).

4.1.1 MILL AREA (IA-2)

Soil sampling at the IA-2 excavation limits was conducted on June 17, after 2.6 cubic yards of soil were removed. During this sampling effort, four confirmation samples, and one QC field duplicate, were collected. Sample results are presented in Table 1 and the field samples for this effort were 15KTM-01 through 15KTM-05. All samples were submitted to SGS for rush analysis of arsenic, total chromium, mercury, and nickel using USEPA Method 6020A. The field duplicate pair collected on June 17, 2015 included primary sample 15KTM-01 and duplicate 15KTM-02.

Complete laboratory analytical reports are provided in Appendix C. Completed ADEC laboratory data checklists and a quality assurance review of the laboratory data are included as Appendix D.

Detectable concentrations of all target metal analytes were found in all samples collected on June 17. The site-specific cleanup level for mercury was exceeded in samples 15KTM-01, 15KTM-02, 15KTM-04, and 15KTM-05. Sample 15KTM-03 from the southwest wall of the excavation did not exceed cleanup levels and excavation in that area was complete. Analytical results for soil samples collected from the floor of the southwest excavation area in 2014 did not exceed cleanup levels for target metals.

Prior to receipt of these soil analytical results, Brice continued excavation activities at IA-2 in the southeast and southwest areas and collected soil samples at new limits of the excavation on June 19, 2015 after the removal of an additional 3.4 cubic yards of soil from the southeast portion of the excavation and 1 cubic yard of soil from the southwest portion of the excavation.

Samples 15KTM-06 through 15KTM-08 were collected and submitted for analysis. Upon receipt of analytical results from sampling conducted on June 17, Brice instructed the laboratory not to analyze samples 15KTM-07 and 15 KTM-08 because analytical results for sample 15KTM-03 from the southwest sidewall indicated target metal concentrations below cleanup levels at the sidewall of the June 17 limit of excavation. Arsenic, chromium, mercury, and nickel results for sample 15KTM-03 were 8.82 mg/kg, 26.3 mg/kg, 1.84 mg/kg, and 26.1 mg/kg, respectively. The

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3.4 cubic yards noted above from the southeast excavation sidewall represented by sample 15KTM-06, which exceeded cleanup levels, were transported to the barge and containerized on June 22 and 23. The 1 cubic yard excavated from the southwest portion of the excavation was used to construct a ramp.

Excavation work continued at the southeast portion of the excavation on June 23. Two rounds of excavation were performed with confirmation sampling performed after each round. Sample 15KTM-09 represented the excavation floor after the first two cubic yards, and samples 15KTM 10, and 15KTM-11 represented the wall and floor of the final limits of excavation, respectively.

The first two cubic yards of soil were transported and containerized on June 23. On June 25, Brice was informed by SGS that samples 15KTM-10 and 15KTM-11 were below the cleanup levels for all target analytes and associated soil was transported the barge that day. Arsenic, chromium, mercury, and nickel results for sample 15KTM-10 were 9.82 mg/kg, 28.1 mg/kg,

0.983 mg/kg, and 24.6 mg/kg, respectively. Arsenic, chromium, mercury, and nickel results for sample 15KTM-11 were 5.68 mg/kg, 21.4 mg/kg, 0.825 mg/kg, and 17.9 mg/kg, respectively.

4.1.2 RETORT MOUND AREA (IA-1) TEST PITS

Two sets of test pits were installed around the retort mound at IA-1 in 2015. Test pits TP-1 through TP-4 were installed on June 18th. Test pits TP-1 through TP-3 were sampled on June 18th, and TP-4 was sampled on June 23rd. Test pits TP5 through TP-8 were installed and sampled on June 19. Analytical results for the first set of test pits, with the exception of TP-4, were available on June 23rd. A set of step-out test pits were installed and sampled, with the exception of test pit TP-10 which was not sampled, based on the analytical results of the first set of test pits on June 24th.

Metal concentrations in soil confirmation samples collected from test pits in the vicinity of the Retort Mound are presented in Table 1. Complete laboratory analytical reports are provided in Appendix C. Completed ADEC laboratory data checklists and a quality assurance review of the laboratory data are included as Appendix D. The limits of excavation at the Retort Mound and soil analytical data are presented on Figure 4. Confirmation soil sample survey data are presented in Appendix F.

Detectable concentrations of all target metal analytes were found in all samples.

Arsenic concentrations ranged from 6.99 mg/kg in sample 15KRM16 to 12.2 mg/kg in sample 15KRM-05. Arsenic was detected above the ADEC cleanup level in confirmation samples 15KRM-04, 15KRM-05, 15KRM-06, 15KRM-10, and 15KRM-13.

Chromium concentrations ranged from 27.6 mg/kg in sample 15KRM-03 to 50.1 mg/kg in sample 15KRM-11. Chromium was detected above the ADEC cleanup level in all soil samples except 15KRM-03, 15KRM-12, and 15KRM-16.

Mercury concentrations ranged from 0.220 mg/kg in sample 15KRM-16 to 217 mg/kg in sample 15KRM-11. Mercury was detected above the ADEC cleanup level in soil samples 15KRM-01, 15KRM-02, 15KRM-04, 15KRM-05, 15KRM-07, 15KRM-10, 15KRM-11, 15KRM-12, 15KRM-14, and 15KRM-15.

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Nickel concentrations ranged from 19.4 mg/kg in sample 15KRM-16 to 69.3 mg/kg in sample 15KRM-11. Nickel was not detected above the ADEC cleanup level in any of the test pit soil samples collected from the vicinity of the retort mound at IA-1 in 2015.

Confirmation soil sampling indicated the exceedances of ADEC cleanup levels for one or more of the target metals at all sample locations except 15KRM-13 at TP-3, and 15KRM-16 at TP-11.

4.1.2.1 Analytical Data Quality

The laboratory reports for all samples are presented in Appendix C. Although the data were deemed acceptable for use, there were precision goals for mercury in work order 1152938 that were not met by the analytical laboratory. These are described in detail in Brice’s QAR in Appendix D and discussed briefly here:

The relative percent difference (RPD) for MS/MSD analyses in work order 1152938 met control limits except for mercury. The matrix is non-homogeneous for mercury and mercury data in work order 1152938 are qualified as estimated “J” values. Affected samples are 15KTM-01, 15KTM-02, and 15KTM-04.

Laboratory duplicates did not meet <20% RPD for mercury in samples 15KTM-01, 15KTM-02, and 15KTM-04 in Work Order 1152938, and mercury data in these samples were qualified “J” to indicate estimated quantities.

The RPD between primary samples and the field duplicates were in agreement in all cases except for mercury in work order 1152938. The RPD of 57% for mercury between parent sample 15KTM-01 (2.67 mg/kg) and duplicate sample 15KTM-02 (4.8 mg/kg) was greater than 50%. Both results were considered estimates with an unknown bias due to sample heterogeneity. Mercury results in work order 1152938 are considered to be estimated “J” values. Affected samples are 15KTM-01, 15KTM-02, 15KTM-03, 15KTM 04, and 15KTM-05.

2015 Kolmakof Mine Site Characterization Report November 2015

4-3

5 CONCLUSIONS AND RECOMMENDATIONS

Conclusions and recommendations are presented below.

5.1 CONCLUSIONS

5.1.1 MILL AREA (IA-2)

The limits of the excavation conducted at IA-2 in 2015 extended to soils meeting cleanup levels established for the site. Excavation sidewall sampling in the southwest portion of the excavation conducted on June 17, 2015 indicated COC metal concentrations below ADEC cleanup levels.

Excavation sidewall and floor sampling in the southeast portion of the excavation conducted on June 23, 2015 indicated COC metal concentrations below ADEC cleanup levels.

5.1.2 RETORT MOUND AREA (IA-1)

Test pit confirmation soil sampling conducted in the vicinity of the retort mound at IA-1 indicate that further contaminated media removal is required. The test pits installed at IA-1 in 2015 did not extend to soils meeting cleanup levels generally to the north or southwest despite extending significantly beyond the limits of excavation identified in the EE/CA (Figure 4).

Analytical results for arsenic and chromium in soil samples collected from test pits on the outer perimeter of, or within an inferred area of, excavation were within or near the upper range of values observed from soil samples collected from the Camp Area during the background study conducted by AMEC in 2008 (AMEC, 2011). Concentrations of arsenic and chromium that are elevated relative to the cleanup levels established for the Camp Area do not correlate with exceedances for the mercury cleanup level established for that area. Therefore, elevated arsenic and chromium concentrations are likely associated with background variation in the occurrence of these COC metals.

The inferred area of soil at IA-1 with mercury concentrations exceeding the Camp Area cleanup level of 1.4 mg/kg is presented in Figure 4. The total area bounded by the actual and inferred boundary, based on sample analytical results, is approximately 3,800 square feet. Based on an average soil thickness of approximately 3 feet to bedrock or undisturbed soil, Brice estimates there are approximately 402 in-situ cubic yards of soil exceeding the Camp Area cleanup level.

During soil removal actions in 2013 and 2014, 110 cubic yards of ex-situ soils were removed from within this area. Based on a 25 percent swell factor of excavated soils, the removal efforts deduct 70 cubic yards from the 402 in-situ cubic yard estimate above. The resulting in-situ volume of soil remaining above the Camp Area cleanup level for mercury is, therefore, approximately 332 cubic yards. Assuming an excavated soil swell factor of 25 percent, the volume of soils requiring ex-situ management to attain cleanup levels is approximately 415 cubic yards. This estimate does not include additional excavation beyond the inferred excavation limits presented in Figure 4.

5-1

5.2 RECOMMENDATIONS

5.2.1 MILL AREA (IA-2)

Brice recommends no further investigation or remediation activities take place at IA-2 based on sampling analytical results obtained from the southwest excavation wall on June 17, and from the southeast excavation area wall and floor on June 23, 2015. Brice recommends closure of

IA-2.

5.2.2 RETORT MOUND AREA (IA-1)

Brice recommends the use of mercury data only as guide for cleanup at IA-1. Brice recommends the removal, transport, and disposal of up to 415 cubic yards of soil not meeting the mercury cleanup level of 1.4 mg/kg from the vicinity of the retort mound at IA-1. Removal of this material should be limited by the occurrence of underlying bedrock or undisturbed soils.

Given the linear extent of excavation perimeter characterized as “inferred” due to analytical results in outer test pits exceeding the 1.4 mg/kg cleanup level (Figure 4), Brice recommends an additional 50 cubic yard in-situ contingency factor for planning purposes. This volume corresponds to an additional 65 cubic yards of ex-situ soil requiring management as a contingency toward attainment of the mercury cleanup level.

5-2

6 REFERENCES

ADEC, 2010, Draft Field Sampling Guidance. May.

ADEC, 2015. Alaska Administrative Code (18 AAC 75), Oil and Other Hazardous Substances Pollution Control, as amended through June 17.

AMEC Environmental & Infrastructure, Inc. (AMEC), 2011. Engineering Evaluation/Cost Analysis Work Plan, Kolmakof Mine Site, Napaimute, Alaska. August.

AMEC, 2012. Engineering Evaluation/Cost Analysis, Kolmakof Mine Site, Napaimute, Alaska.

May.

Brice Environmental Services Corporation (Brice), 2013. BLM, Kolmakof Mine Site Interim Removal Action Work and Management Plan, Final. May.

Brice, 2014a. Kolmakof Mine Site Interim Removal Action. April.

Brice, 2014b. Proposed Addendum to Kolmakof Mine Site – 2013 Interim Removal Action, BLM Contract No. L12PC00215, Work and Management Plan. July.

Brice, 2014c. 2014 Kolmakof Mine Site Interim Removal Action Report, Kolmakof Mine Site, Alaska. December.

Brice, 2015. Site Characterization and Limited Soil Removal, Kolmakof Mine Site, Near Aniak, Alaska, Work and Management Plan. May.

United States Environmental Protection Agency, 2007. Method 6200, Field Portable X-Ray Fluorescence Spectrometry for the Determination of Elemental Concentrations in Soil and Sediment, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, EPA Publication SW-846, (3rd edition, final update IV).

6-1

FIGURES

STATE AND SITE VICINITY

SITE CHARACTERIZATION AND LIMITED SOIL REMOVAL

KOLMAKOF MINE SITE, NAPAIMUTE, ALASKA

DATE:

PROJECT No.:

DRAWN:

10/8/2015

D.H.

FIGURE:

Copyright:© 2013 National Geographic Society, i-cubed

PROJECT LOCATION

FAIRBANKS

JUNEAU

ANCHORAGE

0 21

Miles p

SITE LOCATION

NAPAIMIUT

K

PIT AREA

TAILINGS AREA

IA-2

LEGEND

!. INVESTIGATION AREA

DIRT ROAD

!.U S K O K W I M R I V E R

MILL AREA

NOTE::

1. ALL LOCATIONS ARE APPROXIMATE.

2. LOCATIONS ESTIMATED FROM FIGURE 2, SITE OVERVIEW,

AMEC ENGINEERING EVALUATION/COST ANALYSIS.

3. SATELLITE IMAGERY ACQUIRED BY WORLDVIEW 2 ON 10.21.2014.

CAMP AREA

IA-1

0 400 200

Feet p

SITE OVERVIEW

SITE CHARACTERIZATION AND LIMITED SOIL REMOVAL

KOLMAKOF MINE SITE, NAPAIMUTE, ALASKA

DATE:

PROJECT No.:

DRAWN:

D.H.

10/30/2015

. 2

FIGURE:

ARROW

TOP OF FORMER

MILL

As 8.82 Cr 26.3 Hg 1.84 Ni 26.1

15KRM-03 (24"bgs)

As 9.82 Cr 28.1 Hg 0.983 Ni 24.6

15KRM-10 (24"bgs)

As 5.68 Cr 21.4 Hg 0.825 Ni 17.9

15KRM-11 (36"bgs)

LEGEND

!(. 2015 CONFIRMATION SOIL SAMPLE

2014 EXCAVATION LIMITS

2015 EXCAVATION LIMITS

bgs ALL RESULTS IN mg/kg

BELOW GROUND SURFACE

2013 EXCAVATION LIMITS

NOTE:

EAST AND WEST EXCAVATION SIDEWALLS

REMOVED TO GRADE OF EXCAVATION FLOOR.

SOUTH SIDEWALL WAS APPROXIMATELY 3 FEET.

(SIDEWALL)

(SIDEWALL)

(FLOOR)

Feet p

3800 Centerpoint Dr. Ste.

520 Anchorage, AK 99503

TOP OF MILL (IA-2) EXCAVATION DIAGRAM

SITE CHARACTERIZATION AND LIMITED SOIL REMOVAL

KOLMAKOF MINE SITE, NAPAIMUTE, ALASKA

DATE:

PROJECT No.:

DRAWN:

D.H.

11/6/2015

BE 3

FIGURE:

(48" BGS)

TP15 (48" BGS) TP1 (26" BGS)

TP2 (36" BGS)

TP9 (42" BGS)

TP3 (48" BGS)

TP11

TP4 (35" BGS)

TP10 (24" BGS)

TP12 (36" BGS)

TP5 (24" BGS)

TP13 (24" BGS)

TP6 (40" BGS)

TP14 (22" BGS) TP7 (14" BGS)

TP8 (28" BGS)

0 10 5

Feet p

AREA EXCAVATED

UP TO 30"

DURING 2013 IRA

RETORT MOUND

AREA EXCAVATED

IN 2014 REMOVAL

Hg 3.84

15KRM-05 (24" bgs)

Hg 0.394

15KRM-06 (40" bgs)

Hg 1.81

15KRM-07 (14" bgs)

Hg 4.89

15KRM-12 (24" bgs)

Hg 3.03

15KRM-01 (26" bgs) bgs BELOW GROUND SURFACE

Notes:

A Duplicate of preceeding sample Results in bold exceed ADEC cleanup levels

Hg 0.220

15KRM-16 (24" bgs)

Hg 137 Hg 217

15KRM-10/11A (36" bgs)

Hg 1.13 Hg 0.772

15KRM-8/9A (28" bgs)

LEGEND

AREA OF CONTAMINATION

INITIAL EXCAVATION AREA

PROPOSED EXCAVATION AREA - DASHED WHERE INFERRED

Hg 10.7 15KRM-15 (48" bgs)

Hg 3.42 15KRM-02 (18" bgs)

Hg 0.722 15KRM-03 (36"bgs)

Hg 1.63 15KRM-04 (12" bgs)

Hg 0.412 15KRM-13 (24" bgs)

Hg 9.08 15KRM-14 (12" bgs)

NOT SAMPLED

!(. TEST PIT LOCATION (TOTAL DEPTH bgs)

HILLSIDE

TOE OF SLOPE

SITE CHARACTERIZATION AND LIMITED SOIL REMOVAL

DATE:

10/21/2015

FIGURE:

KOLMAKOF MINE SITE, ALASKA

PROJECT No.:

BE 4

CAMP AREA SOIL SAMPLING RESULTS AND PROPOSED EXCAVATION AREA DRAWN:

D.H.

TABLES

Table 1

Analytical Methods and Soil Cleanup Levels

2015 Kolmakof Mine Site Characterization and Limited Removal

Field Sample ID Sample Location

Date Sampled

USEPA Method 6020A

Arsenic (mg/kg)

Chromium (mg/kg)

Mercury (mg/kg) Nickel (mg/kg)

Mill Area Cleanup Levels 12.7 30 1.99 86

15KTM-01 SW Wall 6/17/2015 9.22 28.9 2.67 J 33.2

15KTM-02A SW Wall 6/17/2015 9.79 27.4 4.8 J 31.1

15KTM-03 SW Wall 6/17/2015 8.82 26.3 1.84 J 26.1

15KTM-04 SE Floor 6/17/2015 8.51 26.8 2.71 J 23.8

15KTM-05 SE Wall 6/17/2015 8.16 25.9 2.57 J 22.8

15KTM-06 SE Wall 6/19/2015 7.93 27.9 30.7 25.0

15KTM-09 SE Floor 6/23/2015 6.32 21.9 2.81 20.0

15KTM-10 SE Wall 6/23/2015 9.82 28.1 0.983 24.6

15KTM-11 SE Floor 6/23/2015 5.68 21.4 0.825 17.9

Camp Area Cleanup Levels 10.7 29.2 1.4 86

15KRM-01 Test Pit 1 @ 26" bgs 6/18/2015 9.00 29.9 3.03 40.4

15KRM-02 Test Pit 2 @ 18" bgs 6/18/2015 9.44 31.0 3.42 39.3

15KRM-03 Test Pit 3 @ 36" bgs 6/18/2015 8.95 27.6 0.722 33.4

15KRM-04 Test Pit 4 @ 12" bgs 6/23/2015 10.9 29.8 1.63 32.6

15KRM-05 Test Pit 5 @ 24" bgs 6/19/2015 12.2 30.5 3.84 26.4

15KRM-06 Test Pit 6 @ 40" bgs 6/19/2015 12.1 29.3 0.394 27.2

15KRM-07 Test Pit 7 @ 14" bgs 6/19/2015 8.14 29.9 1.81 40.4

15KRM-08 Test Pit 8 @ 28" bgs 6/19/2015 10.5 31.1 1.13 45.7

15KRM-09A Test Pit 8 @ 28" bgs 6/19/2015 8.91 31.1 0.772 46.7

15KRM-10 Test Pit 9 @ 36" bgs 6/24/2015 10.9 35.3 137 52.3

15KRM-11A Test Pit 9 @ 36" bgs 6/24/2015 8.83 50.1 217 69.3

15KRM-12 Test Pit 12 @ 24" bgs 6/24/2015 9.48 28.8 4.89 31.8

15KRM-13 Test Pit 13 @ 24" bgs 6/24/2015 11.0 29.7 0.412 35.3

15KRM-14 Test Pit 14 @ 12" bgs 6/24/2015 10.6 30.2 9.08 41.3

15KRM-15 Test Pit 15 @ 48" bgs 6/24/2015 8.78 30.1 10.7 39.0

15KRM-16 Test Pit 11 @ 24" bgs 6/24/2015 6.99 28.8 0.220 19.4

Notes: Abbreviations:

A Duplicate of preceeding sample -- - not analyzed Results in bold exceed ADEC cleanup levels ADEC - Alaska Department of Environmental Conservation

AK - Alaska Method bgs - below ground surface J - estimated value mg/kg - milligrams per kilogram

ND - not detected at or above the [Limit of Detection]

APPENDIX A

FIELD LOG BOOK

Site Characterization and Limited Soil Removal Report Kolmakof Mine Site, Alaska

Bureau of Land Management Alaska State Office

4700 BLM Road

Anchorage, AK 99507-2591

November 2015

APPENDIX B

PROJECT PHOTOGRAPHS

Site Characterization and Limited Soil Removal Report Kolmakof Mine Site, Alaska

Bureau of Land Management Alaska State Office

4700 BLM Road

KMS 2015 Photo-Log, June 15 through June 26, 2015.

Excavating Soil on Southwest Sidewall at IA-2

Filling sandbag at IA-2 excavation during removal of west sidewall. View to north.

Soils from IA-2 Excavation Prepared for Transport to Barge Landing

Sampling Soil on Southeast Sidewall at IA-2 Excavation

Barge Loading at Ramp

Test Pit near Retort Mound

Demobilizing Gear and Supersacks of Excavated Soil

APPENDIX C

LABORATORY ANALYTICAL DATA REPORTS

Site Characterization and Limited Soil Removal Report Kolmakof Mine Site, Alaska

Bureau of Land Management Alaska State Office

4700 BLM Road

Report Number: 1152938

Client Project: Kolmakof

Laboratory Report of Analysis

Dear Don Maloney, Enclosed are the results of the analytical services performed under the referenced project for the received samples and associated QC as applicable. The samples are certified to meet the requirements of the National

Environmental Laboratory Accreditation Conference Standards. Copies of this report and supporting data will be retained in our files for a period of ten years in the event they are required for future reference. All results are intended to be used in their entirety and SGS is not responsible for use of less than the complete report. Any samples submitted to our laboratory will be retained for a maximum of fourteen (14) days from the date of this report unless other archiving requirements were included in the quote.

If there are any questions about the report or services performed during this project, please call Forest at (907)

562-2343. We will be happy to answer any questions or concerns which you may have.

Thank you for using SGS North America Inc. for your analytical services. We look forward to working with you again on any additional analytical needs.

Sincerely, SGS North America Inc.

Forest Taylor Date

Project Manager Forest.Taylor@sgs.com

To: Environmental Comp. Consultants (ECC)

1500 Post Road

Anchorage, AK 99501

(907)644-0428

Print Date: 06/22/2015 3:54:08PM

Member of SGS Group

SGS North America Inc. 200 West Potter Drive, Anchorage, AK 99518 t 907.562.2343 f 907.561.5301 www.us.sgs.com mailto:Forest.Taylor@sgs.com http://www.us.sgs.com

Case Narrative

SGS Client: Environmental Comp. Consultants (ECC)

SGS Project: 1152938

Project Name/Site: Kolmakof

Project Contact: Don Maloney

Refer to sample receipt form for information on sample condition.

1152938001(1272003DUP) (1272007) DUP

6020A - Metals - MS/MSD and PS/DUP RPD for mercury was outside of acceptance limits. Sample is non-homogeneous for mercury.

1152938001(1272003MS) (1272004) MS

6020A - Metals - MS recoveries for barium(150%) and chromium(123%) were outside of acceptance criteria. Post digestion spike was successful.

1152938003-A(1272227MS) (1272230) MS

6020A - Metals - MS recovery for mercury(159%) was outside of acceptance criteria. Post digestion spike was successful.

1152938001(1272003MSD) (1272005) MSD

6020A - Metals - MS recoveries for barium(174%), mercury(663%) and chromium(124%) were outside of acceptance criteria. Post digestion spike was successful.

6020A - Metals - MS/MSD and PS/DUP RPD for mercury was outside of acceptance limits. Sample is non-homogeneous for mercury.

1152938003-A(1272227MSD) (1272231) MSD

6020A - Metals - MSD recoveries for mercury(170%) and chromium(124%) were outside of acceptance criteria. Post digestion spike was successful.

*QC comments may be associated with the field samples found in this report. When applicable, comments will be applied to associated field samples.

Print Date: 06/22/2015 3:54:12PM

Member of SGS Group

SGS North America Inc.

200 West Potter Drive, Anchorage, AK 99518 t…