Final_AKARNG SAV RA Report.pdf

National Guard Federal Scout Armory

Remedial Action Report

Savoonga, Alaska Contract W911KB17D0020

ADEC File Number 670.38.002

ADEC Hazard ID 3099

June 2023

Prepared for:

U.S. Army Corps of Engineers

National Guard Federal Scout Armory

Remedial Action Report

Savoonga, Alaska Contract W911KB17D0020

ADEC File Number 670.38.002

ADEC Hazard ID 3099

June 2023

Prepared for:

U.S. Army Corps of Engineers

Prepared by:

Brice Engineering, LLC 3700 Centerpoint Drive, Suite 8223

Anchorage, Alaska 99503

907.275.2896 PH

www.BriceEng.com m http://www.briceeng.com/

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National Guard Federal Scout Armory Remedial Action Report i Savoonga, Alaska

TABLE OF CONTENTS

ACRONYMS AND ABBREVIATIONS ...................................................................................................... III EXECUTIVE SUMMARY ......................................................................................................................... V

1.0 INTRODUCTION

1.1 Project Objectives

1.2 Site Background

1.2.1 Climate

1.2.2 Geology

1.2.3 Hydrogeology

1.3 Site History

1.3.1 1996 Preliminary Assessment/Site Investigation

1.3.2 1998 Remedial Investigation

1.3.3 2004 Alternate Cleanup Level Demonstration Project

1.3.4 2009 Secondary Site Characterization

1.3.5 2011 Data Gap Investigation

1.3.6 2016 Site Characterization Investigation

1.3.7 2018 Transfer of Ownership

1.3.8 2020 Alternative Cleanup Levels Summary

2.0 REGULATORY CRITERIA

3.0 FIELD ACTIVITIES

3.1 Mobilization

3.2 Site Preparation

3.3 Field Screening

3.4 Soil Investigation

3.5 Supra-permafrost Porewater Investigation

3.5.1 Monitoring Well Construction

3.5.2 Monitoring Well Development

3.5.3 Supra-permafrost Porewater Sampling

3.6 Decontamination

3.7 Waste Management

3.8 Survey

3.9 Site Restoration

3.10 Work Plan Deviations

4.0 ANALYTICAL RESULTS

4.1 Soil Analytical Results

4.2 Supra-permafrost Porewater Analytical Results

5.0 QUALITY ASSURANCE

6.0 HUMAN HEALTH CONCEPTUAL SITE MODEL

6.1 Sources and Type of Chemicals

6.2 Affected Media

6.3 Chemical Release and Transport Mechanisms

6.4 Human Receptors

6.5 Exposure Pathways

TABLE OF CONTENTS (CONTINUED)

National Guard Federal Scout Armory Remedial Action Report ii Savoonga, Alaska

6.5.1 Soil

6.5.2 Groundwater

6.5.3 Sediment and Surface Water

6.5.4 Biota

7.0 CONCLUSIONS AND RECOMMENDATIONS

8.0 REFERENCES

TABLES

Table 1 ADEC-Approved Soil ACLs Table 2 Project Action Limits and Laboratory-Specific Limits by Analyte – Soil Table 3 Project Action Limits and Laboratory-Specific Limits by Analyte – Supra-permafrost Porewater Table 4 Summary of Soil Analytical Results Table 5 Summary of Supra-Permafrost Porewater Analytical Results

FIGURES

Figure 1 Location and Site Vicinity Figure 2 Site Features Figure 3 Savoonga Drinking Water Source Figure 4 Savoonga Conceptual Hydrology Model Figure 5 Previous Soil and Porewater Sample Locations and Exceedances Figure 6 2022 Remedial Action Analytical Results

APPENDICES

Appendix A Appendix B Appendix C Appendix D Appendix E Appendix F

Field Logbook Photograph Log Chemical Data Quality Review Survey Conceptual Site Model Regulatory Correspondence

National Guard Federal Scout Armory Remedial Action Report iii

ACRONYMS AND ABBREVIATIONS

°F degrees Fahrenheit % percent AAC Alaska Administrative Code ACL alternative cleanup level ADEC Alaska Department of Environmental Conservation ADNR Alaska Department of Natural Resources AKARANG Alaska Army National Guard AST aboveground storage tank bgs below ground surface Brice Brice Engineering, LLC BTEX benzene, toluene, ethylbenzene, and xylenes btoc below top of casing CDQR Chemical Data Quality Review COC contaminant of concern CSM conceptual site model cy cubic yard DGI data gap investigation DL detection limit DoD Department of Defense EPH extractable petroleum hydrocarbons foc fraction of organic carbon FD field duplicate FSA Federal Scout Armory GAC granular activated carbon GNSS Global Navigation Satellite System GRO gasoline range organics IDW investigative derived waste mg/kg milligrams per kilogram mg/L milligrams per liter MS matrix spike MSD matrix spike duplicate NGS National Geodetic Survey OPUS Online Positioning User System PAH polycyclic aromatic hydrocarbon PAL project action limit PID photoionization detector ppm parts per million PVC polyvinyl chloride QC quality control

ACRONYMS AND ABBREVIATIONS (CONTINUED)

National Guard Federal Scout Armory Remedial Action Report iv Savoonga, Alaska

RA Remedial Action RI Remedial Investigation RRO residual range organics RTK real-time kinematic SDG sample delivery group TPH total petroleum hydrocarbons UFP-QAPP Uniform Federal Policy Quality Assurance Project Plan USACE U.S. Army Corps of Engineers VOA volatile organic analysis VPH volatile petroleum hydrocarbons

National Guard Federal Scout Armory Remedial Action Report v

EXECUTIVE SUMMARY

This report was prepared to detail the Remedial Action (RA) performed at the Alaska Army National Guard Federal Scout Armory (FSA) in Savoonga, Alaska by Brice Engineering, LLC (Brice) between 12 July and 19 July 2022.

Thirty cubic yards of contaminated soil was excavated from the source area where contaminants of concern (COCs) were present in concentrations above Alaska Department of Environmental Conservation-approved alternative cleanup levels. The excavation was approximately 15 feet by 14 feet and was advanced to the depth of frozen soils at approximately 3 feet below ground surface (bgs). Seven primary samples and one field duplicate were collected from the excavation base and sidewalls. Concentrations of diesel range organics greater than the project action limit (PAL) of 3,000 milligrams per kilograms (mg/kg) were observed in the base of the excavation and the northern, eastern, and southern sidewalls.

Field screening results from a series of test pits advanced outside of the excavation in the southeast quadrant of the property provided evidence that contamination may not be contained to the initial area of concern.

Five temporary monitoring wells were excavation-installed to a depth of approximately 5 feet bgs east and south of the source area. Supra-permafrost porewater samples were collected from two of the temporary monitoring wells; the remaining three wells were dry and could not be sampled. Two primary samples and one field duplicate were collected from WP-01 and WP-05. Diesel range organics, residual range organics, and benzene concentrations exceeded the PALs in WP-01, and residual range organics exceeded the PAL in WP-05. All other analytes were either less than the PAL or non-detect.

A Data Gap investigation is recommended to further delineate the contamination. Future soil sampling should be conducted using equipment capable of advancing through the frozen silt active layer, such as an excavator. It is recommended that an additional attempt be made to sample porewater to the east, which was not sampled during this investigation because wells were dry. Additional supra-permafrost porewater sampling will delineate the extent of porewater impacts at the site. Any future work will need to be coordinated with Kukulget, Inc. because ownership of the building transferred in 2018.

National Guard Federal Scout Armory Remedial Action Report vi

National Guard Federal Scout Armory Remedial Action Report 1

1.0 INTRODUCTION

This report presents the Remedial Action (RA) performed at the Alaska Army National Guard Federal Scout Armory (FSA) in Savoonga, Alaska by Brice Engineering, LLC (Brice) for the U.S. Army Corps of Engineers (USACE), under Contract W911KB-17-D-0020, Task Order W911KB-18-F-0155. Figure 1 presents the site location and vicinity.

The field activities documented in this report were conducted from 12 to 19 July 2022 in accordance with the Alaska Department of Environmental Conservation (ADEC)-approved Remedial Action, National Guard Federal Scout Armory Work Plan Uniform Federal Policy Quality Assurance Project Plan (Brice 2022), hereafter referred to as the Work Plan. This report is supported by six appendixes: Appendix A includes the field logbook, Appendix B contains a photograph log, Appendix C presents the Chemical Data Quality Review, Appendix D includes survey data, Appendix E contains the Conceptual Site Model, and Appendix F presents regulatory correspondence.

1.1 Project Objectives

The primary project objectives were to remove remaining soil containing concentrations of contaminants of concern (COC) above the project action limits (PAL) and install temporary monitoring wells to characterize the eastern lateral extent of supra-permafrost porewater impacted by historical petroleum releases.

To accomplish these objectives, the following was planned:

• Excavation and removal of up to 25 cubic yards (cy) of impacted soil

• Confirmation soil sampling from excavation boundaries to determine presence/absence of contaminated soil with chemical concentrations greater than the PALs

• Supra-permafrost porewater sampling from newly installed temporary monitoring wells located east of the source area to determine presence/absence of contamination in supra-permafrost porewater at concentrations greater than the ADEC Table C groundwater cleanup levels

1.2 Site Background

The village of Savoonga lies on the north-central tip of St. Lawrence Island in the Bering Sea, approximately 164 miles west of Nome, Alaska. The Savoonga FSA is an active contaminated site in the ADEC Contaminated Sites Program database with File Number 670.38.002, Hazard ID 3099, and site name “AKARNG Savoonga FSA”.

According to the 2010 Census, Savoonga, Alaska has a population of 671. The only other community on St. Lawrence Island is Gambell (population 681), located approximately 39 miles west of Savoonga.

Beyond local access, Savoonga is only accessible by air and boat.

Historically, residents have relied on a subsistence lifestyle consisting of fish, wildlife, and plants from the region. In addition, many migratory birds pass through the area on a seasonal basis.

There are four active contaminated sites in Savoonga, including the Savoonga FSA. The closest active contaminated site is immediately adjacent to and uphill from the Savoonga FSA property line and is listed in the ADEC Contaminated Sites Program database with File Number 670.38.008, ADEC Hazard ID 25444, and site name “ADOT&PF SREB – Savoonga Airport (New)”. Several residential buildings not associated

National Guard Federal Scout Armory Remedial Action Report 2 with the FSA are located within the property boundary. A former tank farm was located approximately 150 feet from the property boundary’s western edge. Figure 2 presents these site features.

1.2.1 Climate

Savoonga has a subarctic maritime climate with some continental influences during winter. Summer temperatures average 40 degrees Fahrenheit (°F) to 51°F. Winter temperatures average -7°F to 11°F.

Average annual precipitation is 10 inches, with 58 inches of snowfall (Western Regional Climate Center, 2019). St. Lawrence Island is subject to prevailing winds averaging 18 miles per hour. Typically, the Bering Sea freezes around St. Lawrence Island in mid-November, with breakup of sea ice occurring in late May.

(Alaska Department of Commerce, Community, and Economic Development, Division of Community and Regional Affairs 2022).

1.2.2 Geology

The dominant soil lithology is a clayey silt containing boulders of bedrock material with most areas featuring a 1-foot layer of peat and organic material above the soil (Ogden 1998). During a 1998 RI, soil was assessed for physical properties including grain size analysis. It was determined that the material in the active layer is a slightly clayey, silty, gravelly sand with a hydraulic conductivity of approximately 2x10-3 centimeters per second (ERM West, Hart Crowser 1999). The bedrock is Quaternary-age basalt resulting from a large shield volcano that extends over most of the central part of the island (Waller 1959; Patton et al. 2011). Well logs from 1966 and 1972 document igneous rock at depths of 11 feet below ground surface (bgs) and 17 feet bgs, respectively (Alaska Department of Natural Resources [ADNR] 1966, 1972).

Permafrost is continuous in the subsurface below Savoonga and lies anywhere between 0.5 feet bgs to 4 feet bgs (Ogden 1998; ERM West, Hart Crowser 1999; North Wind, Inc. 2009; Clarus 2006; CH2M HILL 2013; Eagle Eye 2017).

1.2.3 Hydrogeology

Permafrost is present at the site at depths of 2 to 4 feet bgs. An active, seasonally thawed groundwater layer is present above the permafrost layer but is not encountered at all times of the year (Ogden 1998).

Drinking water is currently obtained from a 195-foot-deep well located a half-mile southeast (upgradient) of the FSA on the northeast end of the air strip (Ogden 1998) (Figure 3). Water is pumped from the well to a 100,000-gallon storage tank (Clarus 2006). The well was installed in 1972 and advanced through a known thaw bulb associated with Sivuungaq River (Figure 4). The closest extent of the thaw bulb is approximately 1,500 feet from the FSA facility (ERM West, Hart Crowser 1999).

1.3 Site History

The Savoonga FSA lies adjacent to the main beach access road on the northwestern side of the city, approximately 200 feet south of the Bering Sea. The beach access road acts as the southeastern boundary of the property. The following infrastructure is situated on a gravel pad:

• A 20-foot by 60- foot, wood-framed building constructed in 1960 (the old FSA building)

• A 30-foot by 40-foot wood-framed building constructed in 1985 (the new FSA building)

• An elevated walkway connecting the old and new FSA buildings

• A 1,500-gallon aboveground storage tank (AST) near the new FSA

• Two 1,500-gallon ASTs near the old FSA

National Guard Federal Scout Armory Remedial Action Report 3

In 1985, 200 gallons of Jet A fuel leaked from drums stored near the AST. In 1992, a leak of an unknown quantity of heating oil from a fuel line. In 1993, two 1,500-gallon ASTs replaced one 3,000-gallon AST near the old FSA building. In 1994, the FSA was deactivated. In 2002, the 3,000-gallon AST near the new FSA was removed and was replaced by the 1,500-gallon AST near the new FSA (Eagle Eye 2017). All three 1,500-gallon ASTs are currently active. Multiple investigations have been completed at the site to determine the nature and extent of contamination (Figure 5). The following subsections present a summary of investigations.

1.3.1 1996 Preliminary Assessment/Site Investigation

In 1996, a Preliminary Assessment/Site Investigation included sampling in potentially contaminated areas (Ogden 1998). Seven locations were chosen for field screening around areas of suspected or potential contamination; soil was collected from 0.5 feet bgs and screened using an infrared spectrophotometry field screening tool for total petroleum hydrocarbons (TPH). Results of field screening guided selection of analytical sampling locations. Five locations were selected for analytical sampling just outside of areas where field screening indicated contamination. The locations are displayed on Figure 5 and are labeled as “SV” with three digits (e.g., SV021).

Analytical soil samples were collected from 0.5 feet bgs and analyzed for diesel range organics (DRO) and TPH. A DRO concentration of 160 milligrams per kilogram (mg/kg) was detected near the shed between the old and new FSA buildings at SV051 (Figure 5). The four remaining samples, collected from the perimeter around the site, showed a maximum concentration of DRO at 23 mg/kg and all results for TPH were non-detect. No Further Action was recommended for the site because contaminant concentrations were below the ADEC cleanup criteria applicable at the time.

1.3.2 1998 Remedial Investigation

In September 1998, to further characterize the site, a remedial investigation (RI) was conducted for the Alaska Army National Guard (AKARNG) (ERM West, Hart Crowser 1999). A total of 19 boreholes were hand-augered within the extent of the gravel pad and one location was advanced west of the gravel pad in the marshy area. An objective of the hand-auger boreholes was to determine the extent and depth of permafrost. Within the gravel pad, the advancement of boring holes was limited due to frozen soil and extended to a maximum depth of 2 to 2.5 feet. The borehole advanced west of the gravel pad encountered permafrost at 3.5 feet bgs.

From the 20 locations, 42 soil samples were analyzed for DRO and a select few were analyzed for gasoline range organics (GRO); residual range organics (RRO); benzene, toluene, ethylbenzene, and xylenes (BTEX);

and polycyclic aromatic hydrocarbons (PAHs). Soil samples were collected from the surface, below the organic layer, at a depth of approximately 0.5 feet bgs and at the bottom of the borehole. Additionally, the one active, seasonal water sample was to be collected near the northernmost 1,500-gallon AST;

however, refusal was met at 2.5 feet bgs and recovery was insufficient. Soil samples from the 1998 RI are presented on Figure 5 and are labeled as “B-” with two digits (e.g., B-01).

Analytical soil sample results indicated contamination was present at the south corner of the old FSA building near the ASTs and downgradient (north and west) of the 3,000-gallon AST by the new FSA building. Near the southern corner of the old FSA, DRO concentrations greater than 1,000 mg/kg were present in two borings with a concentration of 1,100 mg/kg in surface soil and 11,000 mg/kg in subsurface soil in borehole B-12; and a concentration of 17,000 mg/kg in surface soil and 8,900 mg/kg in subsurface soil in boreholeB-13. These samples were also submitted for PAH analysis; no PAH compounds were detected at concentrations greater than the Arctic Zone risk-based cleanup levels applicable at the time

National Guard Federal Scout Armory Remedial Action Report 4 of the investigation. These two locations were bounded by samples with concentrations of DRO less than 1,000 mg/kg (B-10, B-14, and B-17). Adjacent to the AST on the north side of the new FSA building, DRO concentrations of 1,300 mg/kg and 1,500 mg/kg were detected in the subsurface in boreholes B-05 and B-06, respectively. Downgradient along the edge of the gravel pad at borehole B-18, DRO concentrations were less than 30 mg/kg in subsurface soil.

The RI Report recommended that DRO be considered the primary contaminant of concern (COC) at this site (ERM West, Hart Crowser 1999). The highest concentration of RRO was 380 mg/kg, GRO was 27 mg/kg, total BTEX was 0.35 mg/kg, and benzene was non-detect.

Due to the presence of continuous permafrost, the contractor recommended that the site satisfied the Arctic Zone criteria, specifically citing the following:

• Via personal communication, the opinion of Mr. Pierre Costello of the U.S. Public Health Service, a design engineer responsible for the sewer and water upgrades completed in Savoonga around 1998 (ERM West, Hart Crowser 1999).

• A subsurface investigation conducted by Clarke Engineering in 1994 related to utility upgrades.

This investigation completed 11 borings across Savoonga, including two near the FSA indicating permafrost was between 1 and 3 feet bgs.

• A groundwater investigation by Terrasat in 1996.

• The RI background boring located approximately 15 feet south of the new armory building.

One soil sample collected during the RI exceeded the current Arctic Zone cleanup level for DRO of 12,500 mg/kg, and it was estimated that 10 to 20 cubic yards (cy) of soil contained DRO concentrations greater than 12,500 mg/kg.

1.3.3 2004 Alternate Cleanup Level Demonstration Project

In August 2004, on behalf of AKARNG, an investigation was completed to demonstrate the validity of a proposed alternative cleanup level (ACL) (Clarus 2006). The investigation included soil and porewater sampling. Twelve hand-augered soil borings were advanced to refusal at a depth of 4.5 feet bgs, and two drive-point well points with 2-foot screens were installed to approximate depths of 4.5 feet bgs. The soil and porewater sample locations are displayed on Figure 5 and are labeled by “SAV-ACL-” followed by three digits (e.g., SAV-ACL-006).

Seven soil samples were collected from locations upgradient from the source area. All soil samples were analyzed for DRO, and five samples collected from locations closest to the source area were also analyzed for GRO, BTEX, and Synthetic Precipitation Leaching Procedure-DRO. Analytical soil sample results for DRO ranged from 33.4 mg/kg to 233 mg/kg, is below the current ADEC Method Two Arctic Migration to Groundwater soil cleanup level.

Two porewater samples were collected from well points near the former shed and near the old FSA ramp were analyzed for DRO and GRO. Porewater collected from the well point near the former shed (SAV-ACL-

016) exhibited a petroleum odor and a slight sheen. The porewater samples indicated elevated DRO concentrations in SAV-ACL-015 and -016 of with results of 30.2 milligrams per liter (mg/L) and 4.07 mg/L, respectively. Additionally, concentrations of GRO and BTEX were detected in sample SAV-ACL-015.

However, the porewater samples contained significant amounts of suspended solids, which may have biased the contaminant concentrations high. No free product was noted during collection of the samples.

National Guard Federal Scout Armory Remedial Action Report 5

As part of the ACL Demonstration Project, it was proposed that supra-permafrost porewater was not a reasonable source of drinking water due to the limited quantity and presence of continuous permafrost.

Additionally, it was recommended that porewater cleanup levels should be 10 times the ADEC Table C groundwater cleanup levels; however, based on this recommendation the DRO concentration in porewater at SAV-ACL-015 still exceeded the proposed ACL.

The following ACLs were recommended for soil:

• GRO based on the maximum concentration allowed in 18 Alaska Administrative Code (AAC) 75;

1,400 mg/kg

• DRO based on a Method Three calculated value based on the ingestion pathway: 10,000 mg/kg

• Total xylenes were based on Method Three calculations for inhalation: 844 mg/kg and

• Benzene, toluene, and ethylbenzene were based on Method Three calculations, Migration to Groundwater pathway, and the 10 times rule; 0.655 mg/kg, 361 mg/kg, and 490 mg/kg respectively.

1.3.4 2009 Secondary Site Characterization

In June 2009, a Site Characterization was conducted to both delineate the extent and determine the volume of DRO-contaminated soil above the ADEC Method Two Migration to Groundwater cleanup level (250 mg/kg; North Wind, Inc. 2009). A total of 48 borings were advanced using a gas-powered auger between two 5-foot grid patterns. Twenty-two borings in Grid 1 were advanced to 0.5 to 1.5 feet bgs to the west of the new FSA buildings, and 26 borings in Grid 2 were advanced to 0.7 to 2.0 feet bgs on the east and south ends of the old FSA. Frozen soil was encountered in every Grid 1 boring between 0.4 and

1.5 feet bgs. Frozen soil was encountered in Grid 2 borings in 10 of the 26 borings between 0.7 and 1.5 feet bgs. The remaining Grid 2 borings encountered refusal at 2.0 feet bgs.

During the field effort, 90 soil samples were field screened using a photoionization detector (PID) and 22 primary soil samples were collected based on the highest field screening results and submitted to the laboratory for DRO analysis. The analytical results showed DRO concentrations greater than 250 mg/kg in soil on the west side of the new FSA (Grid 1) and less than 250 mg/kg on the southern side of the old FSA (Grid 2). There was limited correlation between field screening and analytical results. The report conclusions included an estimated 11 cy of soil with DRO concentrations greater than 250 mg/kg were present at the site. The 2009 locations are presented on Figure 5 and are labeled “09SAV” followed by six digits (e.g., 09SAV-01-G100).

1.3.5 2011 Data Gap Investigation

In July 2011, a Data Gap Investigation (DGI) was conducted to delineate the extent of petroleum-contaminated soil and porewater and to support previous remediation recommendations. During the investigation, no new sources of contamination were identified, and no evidence of stained soil or recent spills was observed (CH2MHill 2013).

A total of 21 soil samples were collected from 12 locations at depths between 0 and 3 feet bgs. Initially, samples were to be collected at greater depths; however, permafrost or ground conditions prevented deeper advancement. Four porewater samples were collected from well points on the north and northwest side of the gravel pad. The 2011 locations are presented on Figure 5 and are labeled “11SAVSB” followed by three digits (e.g., 11SAVSB013) and for well points as “11SAVGW” with three digits (e.g., 11SAVGW001); 11SAVSB004 and 11SAVSB007 were soil and porewater sample points.

National Guard Federal Scout Armory Remedial Action Report 6

The soil samples were field screened using a PID prior to collection. Samples were collected from the locations with the highest field screening results and submitted to the laboratory for DRO analysis, with a subset analyzed for BTEX, PAHs, extractable petroleum hydrocarbons (EPH), and volatile petroleum hydrocarbons (VPH). Porewater samples were submitted for DRO analysis, and one sample was also analyzed for BTEX, PAHs, EPH, and VPH.

Analytical soil results confirmed petroleum-related contamination in the previously identified areas.

Several analytes exceeding the ADEC Method Two Migration to Groundwater cleanup levels were observed, with maximum concentrations detected at sample location 11SAVSB001. Contaminants that exceeded cleanup levels at this location were: DRO (17,000 mg/kg), benzene (3.1 mg/kg), toluene (160 mg/kg), ethylbenzene (48 mg/kg), total xylenes (250 mg/kg), naphthalene (180 mg/kg), 1-methylnaphthalene (230 mg/kg), and 2-methylnaphthalene (360 mg/kg).

The analytical porewater results showed an elevated DRO concentration of 18 mg/L at location 11SAVSB004. The three remaining porewater samples had detected DRO concentrations of 0.6 mg/L,

0.81 mg/L and 1.1 mg/L, which were below the current ADEC Table C groundwater cleanup level of

1.5 mg/L.

In a 2017 letter from ADEC, the ACLs that were proposed for DRO and benzene in the 2011 DGI Report (CH2M HILL 2013) were not approved, and it was recommended that the ADEC Method Three ACL calculator be used to calculate soil ACLs.

1.3.6 2016 Site Characterization Investigation

In 2016, a Site Characterization Investigation was conducted (Eagle Eye 2017) to fill data gaps and evaluate the nature and extent of groundwater contamination. During the investigation, five monitoring wells were installed around the perimeter of the facility (Figure 5, MW-01 through MW-05). The monitoring wells were installed to maximum depths of 6.5 feet bgs. Permafrost was encountered at 2 to 4 feet bgs and ice was found in each boring.

Two of five wells (MW-04 and MW-05) were installed on the north and northwest side of the facility, and porewater was encountered in these wells after installation between 2.5 and 6.1 feet bgs. In the three wells installed on the south and east side of the facility (MW-01, MW-02, and MW-03), porewater was observed between 3.1 and 3.6 feet bgs. Wells MW-02, MW-03, and MW-04 contained DRO, RRO, and toluene concentrations greater than the ADEC Table C groundwater cleanup levels; DRO exceeded in MW-02 and MW-03, RRO exceeded in MW-04, and toluene exceeded in MW-02 and MW-04. The maximum DRO concentration was 2.9 mg/L in MW-03. As a result of the investigation, it was suggested that the extent of porewater contamination was not defined upgradient and crossgradient, particularly on the southeast side of the old FSA building.

1.3.7 2018 Transfer of Ownership

The AKARNG lease for the FSA building from Kukulget, Inc. expired in 2018 and the site reverted to the corporation’s ownership. Official documentation is pending.

1.3.8 2020 Alternative Cleanup Levels Summary

In 2020, soil ACLs for petroleum hydrocarbons, including DRO, RRO, GRO, BTEX, and PAHs were calculated using the most current ADEC Method Three Calculator and petroleum cleanup levels calculator (Brice 2021). Site-specific input values for fraction of organic carbon (foc) and hydraulic conductivity were used to calculate the soil ACLs. All other inputs were the ADEC default values. The foc input value was derived

National Guard Federal Scout Armory Remedial Action Report 7 by calculating the 95 percent (%) lower confidence level of the mean of total organic carbon samples collected outside of contaminant source zones during the 1998 Remedial Investigation (ERM West, Hart Crowser 1999) and the 2004 ACL Demonstration Project investigation (Clarus 2006). When using the 10 previous foc values and excluding one outlier result, the calculated site-specific foc value is 0.01278 grams carbon per gram soil.

A site-specific hydraulic conductivity value was derived from the 1998 Remedial Investigation (ERM West, Hart Crowser 1999). Results for grain size analysis performed on a soil sample collected from boring location B-13 at a depth of 1.5 to 2 feet bgs were used in the Hazen equation to calculate a site-specific hydraulic conductivity value of 2x10-3 centimeters per second. This boring was chosen to be representative of the conditions in the active layer.

AKARNG submitted the ACL Summary and approval request to ADEC on 25 June 2020. ADEC approved the ACLs in a 30 July 2020 letter. Table 1 presents the soil ACLs.

Table 1 ADEC-Approved Soil ACLs

COC ADEC-APPROVED ACLS

(mg/kg)1

GRO 1,400

DRO 3,000

RRO 10,000

Benzene 0.13

Toluene 47

Ethylbenzene 1.2

Total Xylenes 13

Chrysene 1,200

Fluorene 460

Naphthalene 0.43

Pyrene 1,100

1-Methylnaphthalene 4.9

2-Methylnaphthalene 15 Notes:

For definitions, refer to the Acronyms and Abbreviations section.

1 Approved by ADEC on 30 July 2020

National Guard Federal Scout Armory Remedial Action Report 8

National Guard Federal Scout Armory Remedial Action Report 9

2.0 REGULATORY CRITERIA

The PALs for GRO, DRO, RRO, BTEX, chrysene, fluorene, naphthalene, pyrene, 1-methylnaphthalene, and 2-methylnaphthalene are defined by the ADEC-approved ACLs calculated in 2020 (Brice 2021). Analytes not included in the ACLs are defined by 18 AAC 75 Method Two, Table B1 Soil Cleanup Levels (ADEC 2021).

The PALs for supra-permafrost porewater are defined by the ADEC-approved ACLs calculated in 2020 (Brice 2021), which are equivalent to 18 AAC 75 Table C Groundwater Cleanup Levels (ADEC 2021). Table 2 presents the PALs and laboratory-specific limits for soil and Table 3 presents the PALs and laboratory-specific limits for supra-permafrost porewater.

Table 2 Project Action Limits and Laboratory-Specific Limits by Analyte – Soil

ANALYTE METHOD CAS

NUMBER

ADEC1

(mg/kg)

ACL2

(mg/kg)

PAL3

(mg/kg)

LABORATORY LIMITS4

(mg/kg)

DL LOD LOQ

DRO AK102 NS 250 3000 3000 9.0 10 20

Benzene SW8260D 71-43-2 0.022 0.13 0.13 0.0039 0.00625 0.0125

Ethylbenzene SW8260D 100-41-4 0.13 1.2 1.2 0.0078 0.0125 0.025

Xylenes (total) SW8260D 1330-20-7 1.5 13 13 0.0228 0.0375 0.075

Toluene SW8260D 108-88-3 6.7 47 47 0.0078 0.0125 0.025

1-Methylnaphthalene SW8270D SIM 90-12-0 0.41 4.9 4.9 0.00625 0.0125 0.025

2-Methylnaphthalene SW8270D SIM 91-57-6 1.3 15 15 0.00625 0.0125 0.025

Acenaphthene SW8270D SIM 83-32-9 37 NS 37 0.00625 0.0125 0.025

Acenaphthylene SW8270D SIM 208-96-8 18 NS 18 0.00625 0.0125 0.025

Anthracene SW8270D SIM 120-12-7 390 NS 390 0.00625 0.0125 0.025

Benzo(a]anthracene SW8270D SIM 56-55-3 0.7 NS 0.7 0.00625 0.0125 0.025

Benzo(a]pyrene SW8270D SIM 50-32-8 1.9 NS 1.9 0.00625 0.0125 0.025

Benzo(b)fluoranthene SW8270D SIM 205-99-2 20 NS 20 0.00625 0.0125 0.025

Benzo(g,h,i)perylene SW8270D SIM 191-24-2 15000 NS 15000 0.00625 0.0125 0.025

Benzo(k)fluoranthene SW8270D SIM 207-08-9 190 NS 190 0.00625 0.0125 0.025

Chrysene SW8270D SIM 218-01-9 600 NS 600 0.00625 0.0125 0.025

Dibenzo(a,h)anthracene SW8270D SIM 53-70-3 6.3 NS 6.3 0.00625 0.0125 0.025

Fluoranthene SW8270D SIM 206-44-0 590 NS 590 0.00625 0.0125 0.025

Fluorene SW8270D SIM 86-73-7 36 NS 36 0.00625 0.0125 0.025

Indeno(1,2,3-cd) pyrene SW8270D SIM 193-39-5 65 NS 65 0.00625 0.0125 0.025

Naphthalene SW8270D SIM 91-20-3 0.038 0.43 0.43 0.005 0.01 0.02

Phenanthrene SW8270D SIM 85-01-8 39 NS 39 0.00625 0.0125 0.025

Pyrene SW8270D SIM 129-00-0 87 NS 87 0.00625 0.0125 0.025 Notes:

For definitions, refer to the Acronyms and Abbreviations section.

1 The most stringent of 18 AAC 75 Method Two Table B1 and B2, Under 40 Inch Human Health and Migration to Groundwater cleanup levels (ADEC 2021).

2 ACLs are defined by the Soil Contaminants of Concern and Cleanup Goals, as approved by ADEC on 30 July 2020.

3 PALs are defined by the ACLs or ADEC 18 AAC 75 Method Two Migration to Groundwater cleanup levels when there is no ACL in place.

4 Laboratory limits for all methods from SGS - Anchorage, AK

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Table 3 Project Action Limits and Laboratory-Specific Limits by Analyte – Supra-permafrost Porewater

ANALYTE METHOD CASRN PAL1

(µg/L)

LABORATORY-SPECIFIC RLS2

(µg/L)

DL LOD LOQ

DRO AK102 LV NS 1500 200 300 600

RRO AK103 LV NS 1100 200 250 500

Benzene SW8260D 71-43-2 4.6 0.12 0.2 0.4

Ethylbenzene SW8260D 100-41-4 15 0.31 0.5 1.0

Toluene SW8260D 108-88-3 1100 0.31 0.5 1.0

Xylenes (total) SW8260D 1330-20-7 190 1.0 1.5 3.0

1-Methylnaphthalene SW8270D SIM LV 90-12-0 11 0.015 0.025 0.05

2-Methylnaphthalene SW8270D SIM LV 91-57-6 36 0.015 0.025 0.05

Acenaphthene SW8270D SIM LV 83-32-9 530 0.015 0.025 0.05

Acenaphthylene SW8270D SIM LV 208-96-8 260 0.015 0.025 0.05

Anthracene SW8270D SIM LV 120-12-7 43 0.015 0.025 0.05

Benzo(a)anthracene SW8270D SIM LV 56-55-3 0.3 0.015 0.025 0.05

Benzo(a)pyrene SW8270D SIM LV 50-32-8 0.25 0.0062 0.01 0.02

Benzo(b)fluoranthene SW8270D SIM LV 205-99-2 2.5 0.015 0.025 0.05

Benzo(g,h,i)perylene SW8270D SIM LV 191-24-2 0.26 0.015 0.025 0.05

Benzo(k)fluoranthene SW8270D SIM LV 207-08-9 0.8 0.015 0.025 0.05

Chrysene SW8270D SIM LV 218-01-9 2 0.015 0.025 0.05

Dibenzo(a,h)anthracene SW8270D SIM LV 53-70-3 0.25 0.0062 0.01 0.02

Fluoranthene SW8270D SIM LV 206-44-0 260 0.015 0.025 0.05

Fluorene SW8270D SIM LV 86-73-7 290 0.015 0.025 0.05

Indeno(1,2,3-cd)pyrene SW8270D SIM LV 193-39-5 0.19 0.015 0.025 0.05

Naphthalene SW8270D SIM LV 91-20-3 1.7 0.031 0.05 0.1

Phenanthrene SW8270D SIM LV 85-01-8 170 0.015 0.025 0.05

Pyrene SW8270D SIM LV 129-00-0 120 0.015 0.025 0.05 Notes:

For definitions, refer to the Acronyms and Abbreviations section.

1 PALs are defined by 18 AAC 75 Table C Groundwater cleanup levels (ADEC 2021).

2 Laboratory limits for all methods from SGS - Anchorage, AK

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3.0 FIELD ACTIVITIES

This section presents the 2022 RA fieldwork. Appendix A includes the field logbook and Appendix B includes a photograph log of field activities.

3.1 Mobilization

Fieldwork was conducted between 12 and 19 July 2022. Two environmental scientists, one operator, and the AKARNG archaeologist mobilized from Anchorage to Nome via commercial air, and then to Savoonga via charter flight.

3.2 Site Preparation

General utility locates were performed by calling the Alaska Digline at 811 prior to drilling tasks and contacting the village council office to request utility maps and onsite consultation. In addition to the general area utility locating process, screening for buried utilities onsite was completed using a Schondstedt magnetometer. Site drawings and owner knowledge were also used in line locating activities.

During buried utility locating, a visual reconnaissance was conducted to identify any surface features that may have impeded the main project objectives or impact contaminant evaluation.

Two disconnected 1,500-gallon ASTs were present in the proposed excavation footprint. Prior to excavation activities, the ASTs were relocated using a mini excavator.

3.3 Field Screening

Field screening was conducted using a PID and headspace screening procedures. PID field screening was conducted to identify potential petroleum contamination and to guide the excavation and collection of analytical samples. Field screening samples were placed in a resealable plastic bag for a period of at least 10 minutes, but no more than 1 hour, at an approximate temperature of 40°F to 60°F, allowing hydrocarbons to volatilize and accumulate in the headspace of the bag. The bag was agitated for 15 seconds to further promote volatilization. The PID probe was inserted into the bag to measure the organic or combustible vapor concentration in parts per million (ppm). The PID was calibrated daily in accordance with manufacturer instructions and included a fresh air calibration to determine the zero point of the sensor calibration curve followed by a span calibration using a standard reference gas (100 ppm Isobutylene) to determine a second point of the sensor calibration.

3.4 Soil Investigation

A Komatsu PC40 mini excavator, with an arm reach of 18 feet, was used to remove approximately 30 cy of contaminated soil from the source area. Excavated soil was placed into 1 cy supersacks for transport and disposal. The excavation was advanced to the depth of frozen soil at approximately 3 feet bgs. During the soil removal supra-permafrost water with a sheen and POL odor was observed inside the excavation.

Soil samples were collected from the base and sidewalls of the excavation using disposable or clean, decontaminated stainless steel tools, and submitted for the analysis of DRO, BTEX, and PAHs. Soil samples were collected at locations in the excavation that appeared to be the most contaminated based on field screening results, field observations including olfactory and visual indications of contamination, and previous analytical sample results. Samples were collected in laboratory-provided sample containers. To minimize volatilization during soil sampling for volatiles (BTEX), approximately 25 grams of soil was placed

National Guard Federal Scout Armory Remedial Action Report 12 in a pre-weighed 4-oz sample jar with Teflon-lined lid and septum as soon as possible. Immediately after collection, approximately 25 mL of methanol was added so the sample was submerged. Samples for DRO and PAHs were collected in a 4-oz, unpreserved sample jar. One field duplicate sample was collected for every 10 primary grab samples collected for each analytical method. The final dimensions of the excavation were 3 feet by 15 feet by 14 feet and extended under a corner of the Old Savoonga FSA building (Figure 6).

During installation of temporary monitoring wells, a series of 10 test pits were advanced to depths of frozen soil at approximately 3 feet bgs outside of the excavation in the southeast quadrant of the property to delineate contamination (Figure 6). Field screening samples were collected from soil in the center of the excavator bucket. PID readings were elevated from these areas. Additional evidence of contamination, in the form of hydrocarbon odor and/or sheening, was observed in test pits and low-lying areas to the south and west of the Savoonga FSA buildings.

3.5 Supra-permafrost Porewater Investigation

Monitoring wells were installed, developed, and sampled to evaluate the nature and extent of contamination in supra-permafrost porewater.

3.5.1 Monitoring Well Construction

Five temporary monitoring wells were excavation-installed to the east and south of the source area in accordance with the Work Plan. Wells were installed to approximately 3 feet bgs and were screened to capture the supra-permafrost porewater layer, found at 1 and 2.4 feet below top of casing (btoc). Water was observed sporadically as a perched layer above frozen soil. The temporary monitoring wells were installed on 16 July. Water levels were measured on 17 July. Water was present in WP-01 and WP-05; WP- 02, WP-03, and WP-04 were dry.

3.5.2 Monitoring Well Development

The temporary monitoring wells were developed approximately 24 hours after installation using a peristaltic pump. Dedicated tubing was used for each well to minimize the potential for cross-contamination. The two temporary monitoring wells with water (WP-01 and WP-05) were developed by purging the well until the water became less turbid. Upon completion of well development, the well was allowed to return to within approximately 80% of the initial measured water level, prior to sampling.

3.5.3 Supra-permafrost Porewater Sampling

After installation and development, samples were collected using a pneumatic bladder pump with a dedicated bladder and tubing; however, due to technical difficulties, sampling for non-volatiles was conducted using the peristaltic pump with dedicated tubing, and volatiles were collected with disposable bailers. A YSI meter with flow-through cell was used to collect measurements of dissolved oxygen (DO), specific conductance, temperature, pH, and oxidation-reduction potential (ORP). A turbidimeter was used to monitor turbidity. Purging continued until three (or four if temperature was used as an indicator) of the parameters were stable. Samples were collected in laboratory-provided sample containers in order of volatility and analyzed for DRO, RRO, BTEX, and PAHs.

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3.6 Decontamination

Equipment was decontaminated between sample locations using a water and Alconox mixture.

Decontamination water was treated through granular activated carbon (GAC) filter and was discharged onsite a minimum of 100 feet away from any drinking water wells and/or surface waters.

3.7 Waste Management

Purge and decontamination water was treated with an onsite GAC filter, visually inspected for sheen, and discharged onsite a minimum of 100 feet away from any drinking water wells and/or surface waters. Spent GAC material was transported with the soil cuttings for offsite disposal.

Solid wastes generated during the field effort were stored in plastic trash bags and transported to the Savoonga landfill for disposal as non-regulated waste. Waste characterization samples were collected and analyzed for Toxicity Characteristic Leaching Procedure Resource Conservation and Recovery Act metals.

Analytical results were below the U.S. Environmental Protection Agency allowable limits. Contaminated soil was transported offsite for disposal at the Columbia Ridge Landfill in Arlington, Oregon.

3.8 Survey

On 19 July 2022 survey fieldwork occurred at the Alaska National Guard Federal Scout Armory in Savoonga, Alaska. The following features were measured during the survey: seven confirmation samples, five temporary well points, ten test pits, Armory building corners, six aerial ground control targets, an excavation boundary extent, and a supersack stockpile extent. Elevation and position were measured using real-time kinematic (RTK) Global Navigation Satellite System (GNSS) relative geopositioning techniques. Elevations of the PVC riser of temporary well points were intended to be measured using third-order differential leveling techniques; however, well points were removed prior to the surveyor arriving on-site. Instead, only the ground elevation and position of the remaining holes were measured, with the PVC riser elevation later computed by adding the measured stick-up elevation. Survey equipment consisted of a Trimble R10-2 GNSS base receiver, R12i GNSS rover receiver, and TSC5 data collector.

Horizontal and vertical control values from a 2011 OPUS shared solution of monument “RPK A” (NGS PID BBCN80) were held fixed for this survey. To verify the monument’s suitability for use a static occupation of “RPK A” more than four hours in duration was measured during this survey. The raw GNSS data was submitted to the National Geodetic Survey (NGS) Online Positioning User System (OPUS). The resulting solution was compared to the shared solution, and it was determined the 2011 values were suitable. The horizontal datum is NAD83 ([2011] Epoch 2010.0000) and the coordinate system is Alaska State Plane System Zone 9. The vertical datum is NAVD88, with orthometric elevations derived from a separation offset applied from Geoid 12B to the measured ellipsoid height. The unit of measurement is U.S. Survey Foot.

Horizontal precisions from the GNSS RTK survey ranged from 0.01 feet to 0.10 feet and vertical precisions ranged from 0.02 feet to 0.09 feet. These precision ranges can be considered a measure of accuracy, relative to control monument “RPK A”. These estimates can be expressed at the 95% statistical confidence level by scaling by a factor of approximately 2. Well elevations could not be measured to the required level of vertical accuracy due to vandalization. Measurements on all other features meet survey data quality requirements outlined in Table 4-3 of the USACE Alaska District Manual for Electronic Deliverables (USACE 2017). Appendix D presents the survey data in tabular format.

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3.9 Site Restoration

The excavation was backfilled with clean material from a local borrow source and compacted to match the existing grade and surrounding material. The local borrow source is located outside of Savoonga and is commonly used by the City of Savoonga for construction projects. The AKARNG archaeologist was onsite during backfill collection to ensure no artifacts were dug up and confirmed there was no prehistoric or modern site use at the borrow source. Visual and olfactory indicators presented no signs of contamination in the backfill soil. The backfill was mounded slightly to allow for settling and then contoured in a way to prevent water accumulation and promote drainage. Temporary monitoring wells were removed from the ground after sampling and survey were complete, and soil was returned to the excavated well hole of origin as backfill. The ASTs were returned to their approximate original location, immediately outside the perimeter of the backfilled area. Temporary monitoring wells were decommissioned, and lathe was placed at boreholes for the surveyor. The lathe was removed by residents prior to the survey; however, locations were still able to be surveyed because locations also had been spray painted.

3.10 Work Plan Deviations

The following Work Plan deviations occurred:

• Due to technical difficulties encountered with the bladder pump, a peristaltic pump with dedicated tubing was used for porewater sampling; samples for volatile analysis were collected using disposable hand bailers.

• Well stick-up heights recorded in the field logbook were added to the survey measurement of the ground elevation at each well location instead of surveying the top of each well casing.

• Temporary monitoring wells WP-02, WP-03, and WP-04 were unable to be sampled because they were dry.

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4.0 ANALYTICAL RESULTS

All samples collected during this project were submitted to SGS of Anchorage, Alaska for analysis. SGS Anchorage holds current ADEC laboratory approval and Department of Defense (DoD) Environmental Laboratory Accreditation Program certifications for all requested analyses. Chemical analyses for all parameters were performed in accordance with the DoD Quality Systems Manual for Environmental Laboratories, Version 5.3 (DoD 2019).

Soil and water samples collected during this project were analyzed using some or all of the following methods:

• DRO – AK102

• RRO – AK103

• BTEX – SW8260D

• PAHs – SW8270D SIM

The following section presents analytical results for soil and supra-permafrost porewater samples. Soil analytical result exceedances are summarized in Table 4. Supra-permafrost porewater sample results are summarized in Table 5. Appendix C presents all analytical data.

4.1 Soil Analytical Results

Seven primary soil samples and one field duplicate were collected from the excavation base and sidewalls.

Concentrations of DRO above the PAL ranged from 4,030 mg/kg to 20,900 mg/kg; benzene exceedances ranged from 0.138 mg/kg to 2.08 mg/kg; ethylbenzene ranged from 1.79 mg/kg to 13.7 mg/kg; and a total xylenes exceedance was observed with a result of 63.3 mg/kg. The following PAHs were observed above PALs: 1-methylnaphthalene exceedances ranged from 5.02 mg/kg to 51.2 mg/kg; 2-methylnaphthalene exceedances were 51.9 mg/kg and 73.9 mg/kg; and naphthalene exceedances ranged from 4.77 mg/kg to

47.1 mg/kg. All other analytes were non-detect or below PALs. The analytical result for benzene in sample 22SAV-SW01-1.5, was non-detect; however, the limit of detection exceeded the PAL.

4.2 Supra-permafrost Porewater Analytical Results

Two primary supra-permafrost porewater samples and one field duplicate were collected from WP-01 and WP-05. DRO, RRO, and benzene concentrations exceeded the PALs in WP-01 with concentrations of

5.89 mg/L, 1.63 mg/L, and 0.016 mg/L, respectively. RRO exceeded the PAL in WP-05 with a concentration of 1.27 mg/L. All other analytes were non-detect or below PALs.

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Table 4 Summary of Soil Analytical Results

SAMPLE ID

22SAV-B01-3 22SAV-B02-3 22SAV-B03-3 22SAV-SW01-

1.5

22SAV-SW02-

2.5 22SAV-SW03-2 22SAV-SW04-2

ANALYTE ADEC1 ACL2 PAL3 UNITS

DRO 250 3,000 3,000 mg/kg 20,900 1,860 1,120 12,500 4,030 191 404

Benzene 0.022 0.13 0.13 mg/kg 2.08 0.138 0.0550 ND [0.199] U 0.0513 ND [0.0112] ND [0.0106]

Ethylbenzene 0.13 1.2 1.2 mg/kg 13.7 2.22 1.83 1.79 0.384 ND [0.0225] ND [0.0211]

Xylenes (total) 1.5 13 13 mg/kg 63.3 9.73 8.49 11.3 2.24 ND [0.0675] ND [0.0635]

1-Methylnaphthalene 0.41 4.9 4.9 mg/kg 51.2 5.02 8.48 38.7 9.72 0.0463 0.473

2-Methylnaphthalene 1.3 15 15 mg/kg 73.9 7.09 12.3 51.9 11.5 0.0570 0.461

Naphthalene 0.038 0.43 0.43 mg/kg 47.1 4.77 9.54 30.9 5.19 0.0237 J 0.120

PID Result -- -- -- ppm >15,000 >15,000 >15,000 >15,000 9,900 222.2 226.1

Notes:

For definitions, refer to the Acronyms and Abbreviations section.

1 The most stringent of 18 AAC 75 Method Two Table B1 and B2, Under 40 Inch Human Health and Migration to Groundwater Cleanup levels (ADEC 2021).

2 ACLs are defined by the Soil Contaminates of Concern and cleanup Goals, as approved by ADEC on 30 July 2020.

3 PALs are defined by the ACL or ADEC 18 AAC 75 Method Two Migration to…