2017-01-09_-__2016_Kolmakof_Mine_Site_Characterization_-_Final_0001.pdf

Site Characterization and Contamination Assessment Report Kolmakof Mine Site, Alaska

Brice Environmental Project Number: 210101

January 2017

Prepared for:

Bureau of Land Management

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2016 Kolmakof Mine Site Characterization Report iii

CONTENTS

ACRONYMS ................................................................................................................................. v

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

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

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

1.3 Project Objectives ................................................................................................. 1-4

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

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

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

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

3.2 Test Pit Installation and Sampling Activities .......................................................... 3-1

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

3.2.2 Test Pit Soil Sampling ............................................................................. 3-2

3.3 Demobilization ....................................................................................................... 3-3

3.4 Quality Assurance and Quality Control ................................................................. 3-3

3.5 Waste Management .............................................................................................. 3-3

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

4.1 Retort Mound Area (IA-1) Test Pit Sampling Results ............................................ 4-1

4.2 Waste Characterization Sampling for TCLP Metals .............................................. 4-2

4.3 Analytical Data Quality .......................................................................................... 4-2

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

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

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

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

FIGURES

Figure 1 State and Site Vicinity Figure 2 Site Overview Figure 3 Retort Mound (IA-1) Test Pit Sampling Results Diagram Figure 4 Retort Mound Cross-Section A – A’ Figure 5 Retort Mound Cross-Section B – B’

TABLES

Table 1 Test Pit Soil Sample Analytical Results Table 2 Waste Characterization Sample TCLP Analytical Results iv 2016 Kolmakof Mine Site Characterization Report

APPENDICES

Appendix A Field Log Book Appendix B Project Photographs Appendix C Laboratory Analytical Data Reports Appendix D ADEC Checklists and Data Quality Review Appendix E Sample Location Survey Data

2016 Kolmakof Mine Site Characterization Report v

ACRONYMS

°C degrees Celsius

AAC Alaska Administrative Code

ADEC Alaska Department of Environmental Conservation

AK Alaska Method bgs below ground surface

BLM Bureau of Land Management

Brice Brice Environmental Services Corporation

Calista Calista Corporation

CFR Code of Federal Regulations

COC constituent of concern

DRO diesel range organics

DQR data quality review

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

NAC Northern Air Cargo

PA/SI preliminary assessment/site investigation

QA/QC quality assurance/quality control

RCRA Resource Conservation and Recovery Act

RPD relative percent difference

RSI removal site inspection

SGS SGS North America, Inc.

TCLP Toxicity Characteristic Leaching Procedure

TKC The Kuskokwim Corporation

USEPA U.S. Environmental Protection Agency

XRF X-ray fluorescence analyzer vi 2016 Kolmakof Mine Site Characterization Report

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1 INTRODUCTION

During the fall of 2016, Brice Environmental Services Corporation (Brice) conducted characterization 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 August, 2016 (Brice, 2016).

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

2016 Kolmakof Mine Site Characterization Report 1-3 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).

In 2015, BLM contracted with Brice to conduct additional removal and characterization at IA-1 and IA-2 under an ADEC-approved work plan (Brice, 2015a). Confirmation samples collected from the excavation floor and sidewalls following the removal of 10 cubic yards of soil from IA-2 indicated residual COC metal concentrations meeting mill-area cleanup levels. Brice recommended closure of IA-2 based on analytical results. At IA-1, Brice installed fifteen characterization test pits and sampled fourteen of them for COC metals in an effort to fully characterize the distribution of COC metals in the vicinity of the retort mound. In addition, four cubic yards of soils were removed from the eastern sidewall of the 2013 excavation area and disposed of with soils from IA-2. The areal extent of mercury contamination yielded an estimated 3,800 square feet impacted to an average depth of 3 feet below ground surface (bgs) or approximately 422 cubic yards of in-situ soil exceeding the cleanup level for mercury. After deducting the 110 ex-situ, or 88 cubic yards of in-situ soil, removed in 2014 and 2015, the remaining soil in the vicinity of the retort mound was estimated to be approximately 334 cubic yards of in-situ, or 418 cubic yards of ex-situ soil. An additional 50 in-situ cubic yards were included to serve as contingency for areas of the characterization limit that were inferred due to mercury concentrations exceeding the camp area cleanup level in the outer-most test pits along the southwestern and northern areas of the estimated excavation perimeter (Brice, 2015b).

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1.3 PROJECT OBJECTIVES

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

Advancing test pits and sampling soils in the immediate vicinity of the Retort Mound to re-characterize the area for additional past retort activities; and, Advancing test pits to assess the distribution of arsenic, chromium, mercury, and nickel in soils within and beyond the limits documented following assessment activities conducted in 2015 in this area.

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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 November 6, 2016 (ADEC, 2016a).

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. Since cleanup has been completed at the mill area, a summary of the action levels for COC metals at the Camp Area, or IA-1, are presented below:

Parameter Method Camp Area Soil Cleanup Level (mg/Kg)

Arsenic EPA Method SW6020 10.7

Chromium, (Total) EPA Method SW6020 29.2

Mercury EPA Method SW7471 1.4

Nickel EPA Method SW6020 86

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 flyover of the site was performed by the BLM project manager on July 14, 2016 to inspect the conditions of the landing ramp. Based on photographs of the observed site conditions, the BLM and Brice project managers agreed that no ramp repair work would be necessary prior to mobilization for the field effort in 2016.

On September 12, 2016, Brice mobilized to the Site to load the barge for starting work on September 13, 2016. Field activities continued until demobilization on September 20, 2016. All activities were performed under the ADEC-approved work plan prepared in August, 2016 (Brice, 2016). BLM Project Manager Larry Beck performed on-site Project Inspector duties from September 13, to September 19, 2016.

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 September 12, 2016, Brice Site Superintendent Carl Benson mobilized to Aniak to support equipment logistics for the work at the KMS. Equipment, fuel, and supplies were staged at the Aniak barge landing on the morning of September 13 for delivery to the site in the crew boat while the Kubota® BX25 tractor was loaded and transported to the site by a landing craft.

The Kubota® tractor, and the totes of supplies were mobilized from Anchorage and Fairbanks using Northern Air Cargo (NAC) prior to crew mobilization in September, 2016. All other equipment used on this project originated in Aniak. Brice mobilized one equipment operator to the site on September 13, and the barge was unloaded at the KMS barge ramp while the IA-1 test pit sampling locations were being established. No ramp improvements were required after landing.

3.2 TEST PIT INSTALLATION AND SAMPLING ACTIVITIES

Contamination assessment activities were conducted at the Retort Mound Area (IA-1) from September 13 through September 19, 2016. Contamination assessment activities at IA-1 commenced on September 13 with the excavation and sampling of five test pits located radially around the retort mound area. On September 14, the remaining eight test pits of the first full set of contamination assessment test pits, pits TP-16 through TP-28, surrounding the retort mound were installed and sampled. One primary soil sample was collected from each of these first thirteen test pits. Communications with the laboratory on September 14 determined that 24-hour turnaround analytical results would not be available due to equipment malfunction. Therefore, the first set of perimeter test pit results would not be available to plan the necessity or location of any subsequent contamination assessment test pits, and the soil samples for test pits TP-16 through TP-28 were submitted on a standard turnaround time basis. Test pit depths ranged from 1 foot bgs at Test Pits TP-16 and TP-28, to 5.5 feet bgs at TP-23 (Figure 3).

On September 15 and 16, nine characterization test pits were installed within the boundary of the retort mound for the purpose of characterizing past activities and determining the distribution of COC metal contamination. Test pits within the retort mound were sampled at two depths

3-2 2016 Kolmakof Mine Site Characterization Report each. Test pits within the retort mound area ranged in depth from 3.0 feet bgs at test pit M1, to

5.0 feet bgs at test pits M5, M6, and M7 (Figure 3).

A second set of contamination assessment step out test pits were installed and sampled on September 16 and 17. The second set of step out test pits comprised ten test pits, TP-29 through TP-38, arranged around the retort mound perimeter beyond test pits sampled in 2015 that did not meet the mercury cleanup level. These test pits ranged in depth from 1 foot bgs at TP-32 to 4 feet bgs at TP-35 (Figure 3). Two soil samples were collected from each of the ten second-step out test pits. Only one soil sample was collected from test pits TP-32 and TP-36 where excavations were not more than one foot bgs in total depth.

Bedrock or native silt soil was encountered at the total depth of all test pits. Figure 3 shows the location of test pits excavated during 2016 contamination and characterization work conducted at IA-1. Photographs of a typical installation and a test pit profile are 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 ex-situ in plastic bags at a frequency of one per foot, or upon noted changes in observed lithology. Samples were collected directly from the test pit sidewalls. 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, and visual observation for red staining indicative of 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. 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. Test pit characterization and contamination assessment soil samples for COC metals analyses were collected from the locations where XRF field screening results indicated both non-detect for mercury and the highest levels of arsenic and chromium.

3.2.2 TEST PIT SOIL SAMPLING

Soil sampling was conducted along the sidewall of each test pit following installation which included measurement of total depth, logging of soil lithology, and photographing the test pit sidewall. Test pit soil samples were collected from the locations along the sidewall yielding the highest field screening results for the COC metals. Soil sampling was performed using disposable sampling equipment and new sampling gloves. New disposable sampling scoops were used to expose material for sampling in the test pits at each location and depth. Up to two soil samples were collected from each test pit based on the depth of the highest screening result or visual changes in the soil lithology.

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Characterization and contamination assessment soil samples were collected in amber jars and placed into coolers at the Site. One set of contamination assessment soil samples were transported to Anchorage via air cargo and submitted to SGS on September 15, 2016. The remaining samples were flown to Fairbanks during demobilization where they were submitted on September 22 and 28, 2016 as follows. The retort mound characterization samples were submitted to SGS in Fairbanks on September 22, 2016. Following receipt and evaluation of the analytical results from test pits TP-16 through TP-28, the final set of contamination assessment samples for test pits TP-29 through TP-38 were selected and submitted to SGS in Fairbanks on September 29, 2016. 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 samples collected. Sampling protocols, sample handling, custody, and transporting procedures followed those specified in the work plan.

3.3 DEMOBILIZATION

In preparation for site demobilization, a horizontal site survey of sampling locations was conducted following the completion of sampling activities on September 17, 2016. Staked test pit locations were field verified and an elevation survey was performed on September 19, 2016.

The field sampling equipment was demobilized from the Site on September 19, 2016 following the completion of the site survey. The Brice Site Superintendent left Aniak for Fairbanks on September 20, 2016. The Kubota® tractor was loaded on the landing craft by the Brice operator and transported back to Aniak on September 26, 2016. The Kubota® tractor was flown back to Anchorage on October 1, 2016 using NAC, and delivered to the BLM warehouse by Sourdough Express on October 3, 2016.

3.4 QUALITY ASSURANCE AND QUALITY CONTROL

Quality assurance/quality control (QA/QC) procedures were maintained throughout the sampling activities. The QC procedures included the analysis of field duplicates and preparation of a laboratory data quality report (DQR) by qualified Brice staff. The DQR included the completion of an ADEC Laboratory Data Review Checklist for each analytical report included in Appendix C. The QA procedures included adherence to appropriate sample collection methodology as described in Brice’s ADEC approved work plan (Brice, 2016). Any reported data discrepancies associated with the soil samples collected from the Site were identified in the DQR (Appendix D) and are summarized in Section 4.2.

3.5 WASTE MANAGEMENT

The laboratory disposed of all sample material submitted for analysis, and all used sampling and PPE materials from on-site activities were disposed of in the Aniak landfill.

In addition to submitting discrete analytical samples for analysis, aliquots of all soils sampled in 2016 were used to comprise four composite samples for waste characterization purposes. A north and a south composite of the contamination assessment test pit samples was prepared for Toxicity Characteristic Leaching Procedure (TCLP) analysis of COC metals. In addition, two

3-4 2016 Kolmakof Mine Site Characterization Report composite samples, north and south, were prepared from aliquots of the retort mound characterization samples. These samples were collected to characterize the general waste stream to be generated during future site excavation and disposal. In prior years, soils from the site were disposed of under facility-approved waste profiles developed for the soils from the same AOC in 2013 and renewed by the receiving facility in 2014. The purpose of the composite sample collection in 2016 was for renewal of the waste profile for 2017 using composite soil samples comprising soil spanning the estimated area of excavation.

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4 FIELD SCREENING AND ANALYTICAL RESULTS

This section describes the findings of sampling conducted in support of the 2016 characterization and contamination assessment performed at the KMS. The nomenclature for sample IDs and AOCs for this project are defined in the example below:

16KRM-16(1) = 2016 sample from Kolmakof Retort Mound (IA-1) collected at test pit TP-16 at a depth of 1-foot bgs.

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 2016.

4.1 RETORT MOUND AREA (IA-1) TEST PIT SAMPLING RESULTS

Three sets of test pits were installed and sampled around the retort mound at IA-1 in 2016. The first step-out test pits TP-16 through TP-28 were installed on September 13th and 14th. Test pits M-1 through M-9 were installed and sampled on September 15th and 16th to characterize conditions, including evidence of past retort activities or discarded equipment, in the retort mound. Test Pits TP-29 through TP-38, the second step-out test pits, were installed and sampled on September 16th and 17th. Analytical results for the first step-out test pits were not available until after demobilization and the second set of step-out test pits, TP-29 through TP- 38, were installed to support potential exceedances at all of the first step-out test pits .

Metal concentrations in soil 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 estimated horizontal limits of excavation at the retort mound and soil analytical data are presented on Figure 3. Cross-sections depicting local lithology, soil analytical data, and estimated vertical limits of excavation are presented on Figures 4 and 5. Test pit location data including soil sample depths, and horizontal and vertical locations are presented in the summary of survey data in Appendix E.

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

Arsenic concentrations ranged from 3.78 mg/kg in sample 16KRM-29(0.75) to 20.9 mg/kg in sample 16KRM-26(1.5).

Chromium concentrations ranged from 22.1 mg/kg in sample 16KRM-29(0.75) to 36.3 mg/kg in sample 16KRM-33(1).

Mercury concentrations ranged from an estimated concentration of 0.135 mg/kg in the duplicate sample collected from test Pit M-9 at 1.5 feet bgs, 16KRM-M9(10), to 28.1 mg/kg in sample

16KRM-M2(2.5).

Nickel concentrations ranged from 18.4 mg/kg in sample 16KRM-M2(2.5) to 49.3 mg/kg in sample 16KRM-16(1).

Confirmation soil sampling indicated the exceedances of ADEC cleanup levels for one or more of the target metals at all sample locations except 16KRM-25(0.75) at TP-25, 16KRM-27(1.5) at

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TP-27, 16KRM-33(2) at TP-33, 16KRM-M1(0.75) at M-1, and 16KRM-M9(10) the duplicate sample collected from 1.5 feet bgs at M-9.

4.2 WASTE CHARACTERIZATION SAMPLING FOR TCLP METALS

Two sets of composite samples were collected from within and surrounding the retort mound at IA-1 in 2016. Composite samples were prepared from aliquots of all analytical soil samples collected from the northern and southern halves of the retort mound, or “M” test pits. A second set of composite samples were comprised analytical soil sample aliquots from all northern and southern step-out, or “TP” test pits installed beyond the toe of the retort mound.

Results for TCLP analysis of composite waste characterization soil samples are presented in Table 2.

Arsenic was not detected above the method detection limit concentration of 0.0750 mg/L in TCLP leachate prepared from any of the waste characterization samples collected from within or surrounding the retort mound area.

Chromium was detected at estimated concentrations ranging from 0.0922 mg/L in the composite soil sample collected from the southern portion within the retort mound, to 0.129 mg/L in the composite sample of all contamination assessment samples collected south of the retort mound limits.

Mercury was not detected above the method detection limit concentration of 0.00310 mg/L in TCLP leachate prepared from any of the waste characterization samples collected from within or surrounding the retort mound area.

Nickel was detected in only one of the four waste characterization composite samples at an estimated concentration of 0.0328 mg/L in the composite of contamination assessment samples collected north of the retort mound area.

None of the composite samples analyzed for COC TCLP metals exceeded toxicity characteristic threshold concentrations, as defined in the Resource Conservation and Recovery Act (RCRA) under Title 40, Chapter I, Subchapter I, Part 261.24 of the Code of Federal Regulations (40 CFR 261.24), for arsenic, chromium, or mercury. There is no RCRA TCLP concentration defined for nickel.

4.3 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 1168620 that were not met by the analytical laboratory. These are described in detail in Brice’s DQR in Appendix D and discussed briefly here:

The RPD between primary samples and the field duplicates were in agreement in all cases except for mercury in work order 1168620. The RPD of 60% for mercury between parent sample 16KRM-M5(2) (0.724 mg/kg) and duplicate sample 16KRM-M5(10) (1.35

2016 Kolmakof Mine Site Characterization Report 4-3 mg/kg) was greater than 50%. The RPD of 63% for mercury between parent sample 16KRM-M9(1.5) (0.258 mg/kg) and duplicate sample 16KRM-M9(10) (0.135 mg/kg) was greater than 50%. Both sets of primary/duplicate results were considered estimates for mercury with an unknown bias due to sample heterogeneity.

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2016 Kolmakof Mine Site Characterization Report 5-1

5 CONCLUSIONS AND RECOMMENDATIONS

Conclusions and recommendations are presented below.

5.1 CONCLUSIONS

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 2016 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 2015 investigation report (Brice, 2015b).

Analytical results for arsenic and chromium in soil samples collected from test pits within and on the outer perimeter of the estimated excavation limits 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 and are not associated with the distribution of cinnabar ore at the Site.

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 3. Cross-sections of the retort mound area show the depth of soils impacted above the Camp Area cleanup level of 1.4 mg/kg. As shown in Figure 3, the total area bounded by the analytically-determined and inferred limits of theestimated excavation boundary, based on sample analytical results, is approximately 5,271 square feet.

Based on an east-to-west average soil thickness of approximately 3.5 feet to bedrock or undisturbed soil meeting cleanup levels (Figure 4), and a north-to-south average soil thickness of approximately 2.5 feet to bedrock or undisturbed soil meeting cleanup levels (Figure 5), Brice estimates an average site-wide depth of removal of 3.0 feet bgs. Removal of soil to this depth involve approximately 586 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 prior removal efforts deduct 88 cubic yards from the 586 in-situ cubic yards estimated above. The resulting in-situ volume of soil remaining above the Camp Area cleanup level for mercury is approximately 497 cubic yards. Assuming an excavated soil swell factor of 25 percent, the volume of soils requiring ex-situ management to attain cleanup levels is estimated at approximately 622 cubic yards. This estimate does not include additional excavation beyond the inferred limits of estimated excavation presented in Figure 3.

5-2 2016 Kolmakof Mine Site Characterization Report

5.2 RECOMMENDATIONS

Brice recommends the use of mercury data only as guide for cleanup at IA-1. The spatial occurrence of remaining COC metals do not correlate with mercury concentrations and, therefore, do not appear to indicate the presence of cinnabar ore.

Brice recommends the removal, transport, and disposal of up to 497 cubic yards of in-situ soil not meeting the mercury cleanup level of 1.4 mg/kg from the vicinity of the retort mound at IA-1 as referenced on Figures 3, 4, and 5. This volume corresponds to an approximate ex-situ volume of 622 cubic yards after imposition of a swell factor of 25 percent to determine the volume of soil requiring handling. Removal of this material should be limited by the occurrence of underlying bedrock or undisturbed soils documented to contain mercury concentrations below the Camp Area cleanup level of 1.4 mg/kg as depicted in Figures 3, 4, and 5.

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 3), 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.

2016 Kolmakof Mine Site Characterization Report 6-1

6 REFERENCES

Alaska Department of Environmental Conservation (ADEC), 2016a. Alaska Administrative Code (18 AAC 75), Oil and Other Hazardous Substances Pollution Control, as amended through November 6.

ADEC, 2016b, Field Sampling Guidance. March.

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

Brice, 2015b. Site Characterization and Limited Soil Removal Report, Kolmakof Mine Site, Alaska. November.

Brice, 2016. Site Characterization and Contamination Assessment Work Plan, Kolmakof Mine Site, Near Aniak, Alaska. August.

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).

6-2 2016 Kolmakof Mine Site Characterization Report

FIGURES

STATE AND SITE VICINITY

SITE CHARACTERIZATION AND CONTAMINATION ASSESSMENT REPORT

KOLMAKOF MINE SITE, ALASKA

DATE:

PROJECT No.:

DRAWN:

12/2/2016

D.H.

FIGURE:

Copyright:© 2013 National Geographic Society, i-cubed

PROJECT LOCATION

FAIRBANKS

BETHEL JUNEAU

ANCHORAGE

0 21

Miles p

SITE LOCATION

NAPAIMIUT

210101

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

MILL AREA

PIT AREA

TAILINGS AREA

CAMP AREA

IA-1

0 400200

Feet p

SITE OVERVIEW

SITE CHARACTERIZATION AND CONTAMINATION ASSESSMENT REPORT

KOLMAKOF MINE SITE, ALASKA

DATE:

PROJECT NO:.

DRAWN:

08/09/2016

D.H.

FIGURE:

LEGEND

!. INVESTIGATION AREA

DIRT ROAD

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.

D o cu m e n t P a th

Q

B

E S

A n ch o ra g e \G

E O

S P

A T

IA

L

P

R O

J E

C T

S \B

E S

\B L

M \K o lm a k o f_

M in e

IA

I_

\G

IS

\M

X D

\R e p o rt \F

Ig u re

S it e

O ve rv ie w .m x d

210101

TP-16

TP-17

TP-18

TP-19

TP-20

TP-21

TP-22

TP-23

TP-24

TP-25

TP-26

TP-27

TP-28

TP-29

TP-30

TP-31

TP-32

TP-33

TP-34

TP-35

TP-36

TP-37

TP-38

M1

M2

M3

M4

M5

M6

M7

M8

M9

TP-7

TP-14

TP-6

TP-13

TP-12

TP-5

TP-11

TP-4

TP-3

TP-9

TP-2

TP-15

TP-1

TP-8

Hg 0.168

16KRM-27(1.5)

Hg 2.76

16KRM-26(1.5)

Hg 0.213

16KRM-25(0.75)

Hg 5.83

16KRM-24(1.25)

Hg 2.81

16KRM-23(2)

Hg 2.87

16KRM-22(2)

Hg 0.161

16KRM-21(3)

Hg 4.19

16KRM-20(2)

Hg 4.05

16KRM-19(2)

Hg 14.30

16KRM-18(3)

Hg 1.96

16KRM-17(2)

Hg 0.17

16KRM-16(1)

Hg 2.38

16KRM-28(1)

Hg 3.66

16KRM-29(0.75)

Hg 9.05

16KRM-30(2)

Hg 3.39

16KRM-31(1)

Hg -

16KRM-32(0.75)

Hg 1.47

16KRM-33(1)

Hg 2.89

16KRM-34(1)

Hg 0.754

16KRM-35(1)

Hg 1.55

16KRM-36(1)

Hg 3.14

16KRM-37(1.5)

Hg 3.09

16KRM-38(1)

Hg 1.34

16KRM-M1(0.75)

Hg 28.1

16KRM-M2(2.5)

Hg 1.28

16KRM-M3(1)

Hg 10.6

16KRM-M4(1)

Hg 16.6

16KRM-M5(4)

Hg 0.236

16KRM-M6(3)

Hg 17.9

16KRM-M7(0.5)

Hg 4.91

16KRM-M8(0.75)

Hg 9.34

16KRM-M9(0.5)

Hg 137

Hg 217

15KRM-10/11A (3)

Hg 1.13

Hg 0.772

15KRM-8/9A (2.3)

Hg 10.7

15KRM-15 (4)

Hg 3.42

15KRM-02 (1.6)

Hg 0.722

15KRM-03 (3)

Hg 1.63

15KRM-04 (1)

Hg 0.412

15KRM-13 (2)

Hg 9.08

15KRM-14 (1)

Hg 0.394

15KRM-06 (3.33)

Hg 1.81

15KRM-07 (1.17)

Hg 4.89

15KRM-12 (2)

Hg 3.84

15KRM-05 (2)

Hg 3.03

15KRM-01 (2.16)

Hg 217

15KRM-11(3)

TP-7

1.2' BGS

TP-14

1.8' BGS

TP-6

3.3' BGS

TP-13

2.0' BGS

TP-12

3.0' BGS

TP-5

2.0' BGS

TP-11

4.0' BGS

TP-4

2.9' BGS

TP-3

4.0' BGS

TP-9

3.5'

BGS TP-2

3.0' BGS

TP-15

3.0' BGS

TP-1

2.2' BGS

TP-8

2.3' BGS

TP-16

1.0' BGS

TP-17

2.5' BGS

TP-18

4.0' BGS

TP-19

3.5' BGS

TP-20

3.5' BGS

TP-21

4.3' BGS

TP-22

4.5' BGS

TP-23

5.5' BGS

TP-24

4.0' BGS

TP-25

4.0' BGS

TP-26

4.5' BGS

TP-27

5.0' BGS

TP-28

1.0' BGS

TP-29

2.0' BGS

TP-30

2.0' BGS

TP-31

2.0' BGS

TP-32

1.0' BGS

TP-33

5.0' BGS

TP-34

3.0' BGS

TP-35

4.0' BGS

TP-36

1.0' BGS

TP-37

3.8' BGS

TP-38

2.8' BGS

M1

3.0' BGS

M2 3.5'

BGS

M3 4.0'

BGS

M4 4.0'

BGS

M5 5.0'

BGS

M6 5.0'

BGS

M7 5.0'

BGS

M8 3.5'

BGS

M9 3.3'

BGS

D.H.C.B.

210101 12/2/2016

FIGURE:

Hg 9.08

D o c u m e n t

P a th

Q

B E

S A n c h o ra g e

\G E

O S

P A

T

IA

L

P R

O J E

C T

S \B

E S

\B L

M \K o lm a k o f_ M in e

IA

I_

\G

IS

\M X

D \R e p o rt

\F Ig u re

M e rc u ry

R e s u lt s a t_

R e to rt

M o u n d

.m x d

1 INCH

p

Fairbanks Office 301 Cushman Street, Street 100 Fairbanks, AK 99701

907.456.1955 (office)

907.452.5018 (fax)

Anchorage Office 3800 Centerpoint Drive, Suite 400 Anchorage, AK 99503

907.275.2896 (Office and Fax)

RETORT MOUND (IA-1) TEST PIT SAMPLING RESULTS DIAGRAM

SITE CHARACTERIZATION AND CONTAMINATION ASSESSMENT REPORT

KOLMAKOF MINE SITE, ALASKA

12 0 12 246

SCALE IN FEET

0 500 1,000250 Feet

SITE LOCATION

DRAWN:

PROJECT No.: DATE:

P.M.:

TP-13

1.8' BGS

M7

5' BGS

Legend

2015 Test Pit Location

2016 Test Pit Location

SITE VICINITY

A'

Cross Section

Excavation

Limits

Excavation

Limits

B l u f f

2016 Test Pit Location in Exceedance (>1.4 mg/kg)

Hg 0.220

15KRM-16 (2)

A

B'

B

Estimated Excavation Limit - Dashed Where Inferred

2014 Excavation Limits

2013 Excavation Limits

Retort Mound Toe of Slope

M7

5' BGS

A A'

Mercury Concentration in mg/kg (Bold where exceeding cleanup level of 1.4 mg/kg)

Toe of Bluff Slope

1 INCH

TP-23

TP-38

TP-22

M-1

M-5

M-2

TP-8

BLUFF

M-9

(Projected)

WEST

A

EAST

A'

0.328

3.09

9.34

0.258

28.1

11.5

0.832

1.34

16.6

2.81

2.87

1.35 J

1.13

(DEPTH IN FEET)

RETORT MOUND CROSS SECTION A - A'

SITE CHARACTERIZATION AND CONTAMINATION ASSESSMENT REPORT

KOLMAKOF MINE SITE, ALASKA

DATE:

PROJECT No.:

DRAWN:

210101

11.21.16

D.H.

FIGURE:

3800 Centerpoint Dr. Ste. 520

Anchorage, AK 99503

0 10

SCALE IN FEET

VERTICAL EXAGGERATION 2:1

LEGEND:

- ESTIMATED DEPTH OF EXCAVATION

(DASHED WHERE INFERRED)

- FILL PLACED BEFORE 2013 (GP-GM)

-FILL PLACED IN 2013 (GP-GM)

- BEDROCK

- COBBLE AND COARSE GRAVEL (GP)

- NATIVE SILT (ML)

-MERCURY CONC. IN SOIL, mg/Kg

(Bold where exceeding cleanup level of 1.4 mg/kg)

1.55

TP-32

M-7 M-4

M-2

M-3

TP-27

TP-9

TP-18

TP-34

TP-36

(Projected)

SOUTH

B

0.168

17.9

0.317

11.5

28.1

0.473

10.6

0.492

1.28

14.3

NORTH

B'

2.13

2.89

1.55

(DEPTH IN FEET)

RETORT MOUND CROSS-SECTION B - B'

SITE CHARACTERIZATION AND CONTAMINATION ASSESSMENT REPORT

KOLMAKOF MINE SITE, ALASKA

DATE:

PROJECT No.:

DRAWN:

210101

11.21.16

D.H.

FIGURE:

3800 Centerpoint Dr. Ste. 520

Anchorage, AK 99503

LEGEND:

- ESTIMATED DEPTH OF EXCAVATION

(DASHED WHERE INFERRED)

- FILL PLACED BEFORE 2013 (GP-GM)

-FILL PLACED IN 2013 (GP-GM)

- BEDROCK

- COBBLE WITH SILT (GP-GM)

- NATIVE SILT (ML)

-MERCURY CONC. IN SOIL, mg/Kg

(Bold where exceeding cleanup level of 1.4 mg/kg)

1.55

0 10

SCALE IN FEET

VERTICAL EXAGGERATION 2:1

TABLES

Table 1 Test Pit Soil Sample Analytical Results

2016 Kolmakof Mine Site Retort Mound Characterization

10.7 29.2 1.4 86 First Step-Out Test Pit Samples

16KRM-16(1) Test Pit 16 @ 1'bgs 9/13/2016 11.2 30.6 0.171 53.5

16KRM-17(2) Test Pit 17 @ 2'bgs 9/13/2016 11.5 29.6 1.96 36.7

16KRM-18(3) Test Pit 18 @ 3'bgs 9/13/2016 9.96 30.1 14.3 40.2

16KRM-19(2) Test Pit 19 @ 2'bgs 9/13/2016 11.5 29.5 4.05 34.6

16KRM-20(2) Test Pit 20 @ 2'bgs 9/14/2016 10.3 29.7 4.19 35.8

16KRM-20(10)* Dup of Test Pit 20 @ 2'bgs 9/14/2016 9.72 29.4 3.36 36.1

16KRM-21(3) Test Pit 21 @ 3'bgs 9/13/2016 8.02 26.9 0.161 18.8

16KRM-22(2) Test Pit 22 @ 2'bgs 9/14/2016 10.3 30.9 2.87 36.3

16KRM-23(2) Test Pit 23 @ 2'bgs 9/14/2016 9.57 28.5 2.81 34.1

16KRM-23(4) Test Pit 23 @ 4'bgs 9/14/2016 -- -- -- --

16KRM-24(1.25) Test Pit 24 @ 1.25'bgs 9/14/2016 9.94 29.6 5.83 35.5

16KRM-24(4) Test Pit 24 @ 4'bgs 9/14/2016 -- -- -- --

16KRM-25(0.75) Test Pit 25 @ 0.75'bgs 9/14/2016 9.39 26.8 0.213 22.6

16KRM-25(2.5) Test Pit 25 @ 2.5'bgs 9/14/2016 -- -- -- --

16KRM-26(1.5) Test Pit 26 @ 1.5'bgs 9/14/2016 20.9 28.7 2.76 36.8

16KRM-27(1.5) Test Pit 27 @ 1.5'bgs 9/14/2016 6.39 23.1 0.168 19.3

16KRM-28(1) Test Pit 28 @ 1'bgs 9/14/2016 8.99 29.6 2.38 39.1

16KRM-28(10)* Dup of Test Pit 28 @ 1' bgs 9/14/2016 9.72 30.7 1.62 41.6

Second Step-Out Test Pit Samples

16KRM-29(0.75) Test Pit 29 @ 0.75" bgs 9/16/2016 3.78 22.1 3.66 20.3

16KRM-29(1.5) Test Pit 29 @ 1.5'bgs 9/16/2016 9.73 34.1 2.49 41.4

16KRM-30(1) Test Pit 30 @ 1'bgs 9/16/2016 3.99 22.9 1.73 20.0

16KRM-30(2) Test Pit 30 @ 2'bgs 9/16/2016 9.48 33.4 9.05 46.3

16KRM-31(1) Test Pit 31 @ 1'bgs 9/16/2016 9.52 31.5 3.39 41.3

16KRM-31(2) Test Pit 31 @ 2'bgs 9/16/2016 10.5 35.5 1.46 41.9

16KRM-32(0.75) Test Pit 32 @ 0.75'bgs 9/16/2016 -- -- -- --

16KRM-33(1) Test Pit 33 @ 1'bgs 9/16/2016 10.5 36.3 1.47 49.3

16KRM-33(2) Test Pit 33 @ 2'bgs 9/16/2016 9.77 27.9 0.239 22.9

16KRM-34(1) Test Pit 34 @ 1'bgs 9/17/2016 9.3 34.1 2.89 42.2

16KRM-34(10)* Dup of Test Pit 34 @ 1'bgs 9/17/2016 9.19 34.7 2.82 43.5

16KRM-34(2.5) Test Pit 34 @ 2.5'bgs 9/17/2016 8.63 31.8 2.13 34.4

16KRM-35(1) Test Pit 35 @ 1'bgs 9/17/2016 8.14 32.7 0.754 45

16KRM-35(2) Test Pit 35 @ 2'bgs 9/17/2016 9.78 32.5 0.425 33.3

ADEC Cleanup Levels Sample Location

USEPA Method 6020A

Field Sample

ID

Date Sampled

Arsenic (mg/kg)

Chromium (mg/kg)

Mercury (mg/kg)

Nickel (mg/kg)

Table 1 Test Pit Soil Sample Analytical Results

2016 Kolmakof Mine Site Retort Mound Characterization

Sample Location

USEPA Method 6020A

Field Sample

ID

Date Sampled

Arsenic (mg/kg)

Chromium (mg/kg)

Mercury (mg/kg)

Nickel (mg/kg)

16KRM-36(1) Test Pit 36 @ 1'bgs 9/17/2016 9.02 33.8 1.55 47.5

10.7 29.2 1.4 86

Second Step-Out Test Pit Samples (continued)

16KRM-37(1.5) Test Pit 37 @ 1.5' bgs 9/17/2016 9.31 33 3.14 45.6

16KRM-37(2.5) Test Pit 37@ 2.5' bgs 9/17/2016 7.57 31.6 1.77 21.6

16KRM-38(1) Test Pit 38@ 1' bgs 9/17/2016 10.4 33.2 3.09 39.9

16KRM-38(2.5) Test Pit 38@ 2.5' bgs 9/17/2016 13.1 35.1 0.328 37.1

Retort Mound Samples

16KRM-M1(0.75) Test Pit M1@ 0.75' bgs 9/15/2016 9.32 28.4 1.34 23.3

16KRM-M1(2) Test Pit M1@ 2.0' bgs 9/15/2016 9.34 30.5 0.832 31.9

16KRM-M2(1) Test Pit M2@ 1' bgs 9/15/2016 8.82 26.7 11.5 30

16KRM-M2(2.5) Test Pit M2@ 2.5' bgs 9/15/2016 7.77 28.1 28.1 18.4

16KRM-M3(1) Test Pit M3@ 1' bgs 9/15/2016 9.76 31.1 1.28 31.5

16KRM-M3(4) Test Pit M3@ 4' bgs 9/15/2016 11.9 29.7 0.492 32.1

16KRM-M4(1) Test Pit M4@ 1' bgs 9/15/2016 7.25 27.5 10.6 25

16KRM-M4(2) Test Pit M4@ 2' bgs 9/15/2016 10.9 29.5 0.473 31.2

16KRM-M5(2) Test Pit M5@ 2' bgs 9/15/2016 11.7 30.9 0.724 J 35.9

16KRM-M5(10)* Dup of Test Pit M5@ 2' bgs 9/15/2016 10.2 30.6 1.35 J 32

16KRM-M5(4) Test Pit M5@ 4' bgs 9/15/2016 8.75 30.2 16.6 33.4

16KRM-M6(1) Test Pit M6@ 1' bgs 9/15/2016 12.3 34.2 0.179 35.9

16KRM-M6(3) Test Pit M6@ 3' bgs 9/15/2016 10.5 33.3 0.236 30.9

16KRM-M7(0.5) Test Pit M7@ 0.5' bgs 9/15/2016 10.5 30.5 17.9 32.9

16KRM-M7(2) Test Pit M7@ 2' bgs 9/15/2016 8.36 31.4 0.317 22.9

16KRM-M8(0.75) Test Pit M8@ 0.75' bgs 9/16/2016 9.06 30.6 4.91 36.7

16KRM-M8(1.5) Test Pit M8@ 1.5' bgs 9/16/2016 9.3 31.6 0.394 24.1

16KRM-M9(0.5) Test Pit M9@ 0.5' bgs 9/16/2016 10.9 30.9 9.34 37.9

16KRM-M9(1.5) Test Pit M9@ 1.5' bgs 9/16/2016 7.7 29.9 0.258 J 21.2

16KRM-M9(10)* Dup of Test Pit M9@ 1.5' bgs 9/16/2016 7.89 28.6 0.135 J 20

Notes: Abbreviations:

* Duplicate of preceeding sample -- - not analyzed Results in bold exceed ADEC cleanup levels ADEC - Alaska Department of Environmental Conservation bgs - below ground surface

J - estimated value mg/kg - milligrams per kilogram

USEPA - United States Environmental Protection Agency

ADEC Cleanup Levels

Table 2 Waste Characterization Sample TCLP Analytical Results 2016 Kolmakof Mine Site Retort Mound Characterization

5.0 5.0 0.2 N/A

Site Characterization Composite Samples

TCLP Comp North

Northern half composite of characterization samples 9/19/2016

TCLP Comp South

Southern half…