2021_4_27_Site_Characterization_Ltd_Removal_Act_Gwater_Monitoring.pdf

2020 Site Characterization, Limited Removal Action, and Groundwater Monitoring

Kotzebue Former IHS/BIA Hospital – School Pipeline Release (ADEC File. No. 410.38.025)

Kotzebue, Alaska

Prepared for:

ALASKA DEPARTMENT OF ENVIRONMENTAL CONSERVATION

555 CORDOVA STREET

ANCHORAGE, AK 99501

Prepared by:

TANANA COMMERCIAL COMPANY/ENVIRONMENTAL MANAGEMENT LLC JV

PO BOX 69

TANANA, ALASKA 99777

April 2021

2020 Site Characterization, Limited Removal Action, and Groundwater Monitoring Report Former IHS/BIA Hospital – School Pipeline Release Job # 17855, April 2021 i

TABLE OF CONTENTS

1.0 SITE DESCRIPTION AND BACKGROUND

1.1 Project Purpose and Objectives

1.2 Site Location

1.3 Background

2.0 FIELD ACTIVITIES

2.1 Work Plan Variances

2.2 Site Characterization Activities

2.3 Product Monitoring Activities

2.4 Soil Removal Activities

2.5 Landfarm Soil Treatment and Maintenance

2.6 Groundwater Monitoring Activities

2.6.1 Water Level Measurements and Flow Direction

2.6.2 Groundwater Sampling

3.0 SAMPLING RESULTS

3.1 Subsurface Conditions

3.2 Site Characterization Results

3.3 Product Monitoring Results

3.4 Soil Removal Results

3.4.1 Stockpile Sample Results

3.4.2 Excavation Confirmation Sample Results

3.5 Groundwater Monitoring Results

4.0 DISCUSSION

4.1 Site Characterization Discussion

4.2 Product Monitoring Discussion

4.3 Soil Removal Discussion

4.4 Groundwater Monitoring Discussion

4.5 Conceptual Site Model Discussion

5.0 QUALITY CONTROL REVIEW

5.1 SGS Report 1203816 Site Characterization Samples

5.2 SGS Report 1205533 Soil Removal Confirmation Samples

5.3 SGS Report 1205534 Groundwater Samples

6.0 INVESTIGATIVE DERIVED WASTE MANAGEMENT

7.0 CONCLUSIONS AND RECOMMENDATIONS

8.0 REFERENCES

Job # 17855, April 2021 ii

TABLES

Table 1 – Summary of July 2020 Site Characterization Analytical Results Table 2 – Summary of Stockpile Headspace Results Table 3 – Summary of Stockpile Analytical Results Table 4 – Summary of Excavation Headspace Results Table 5 – Summary of Detectable Excavation Analytical Results Table 6 – Groundwater Levels and Elevations Table 7 – Summary of Detectable Groundwater Analytical Results Table 8 – Historical Groundwater Sampling Results

FIGURES

Figure 1 – Vicinity Map Figure 2 – 2020 Boring Locations Figure 3 – Final Excavation Extent and Locations of Buried Debris Figure 4 – Excavation Field Screening Sample Locations Figure 5 – Excavation Analytical Sample Locations Figure 6 – Excavation Plan Figure 7 – Groundwater Monitoring Well Locations and Groundwater Elevation Contours Figure 8 – Lot 3 Soil Concentrations Above Migration to Groundwater Figure 9 – Lot 4 Soil Concentrations Above Migration to Groundwater and Human Health

APPENDICES

Appendix A – Field Notes Appendix B – Photo Pages Appendix C – ATC Laboratory Report Appendix D – SGS Laboratory Reports and Laboratory Data Review Checklist Appendix E – Boring Logs Appendix F – Human Health Conceptual Site Model Graphic Form and Human Health

Conceptual Site Model Scoping Form and Standardized Graphic

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ACRONYMS AND ABBREVIATIONS

ACM Asbestos-Containing Materials ADEC Alaska Department of Environmental Conservation ADOT&PF Alaska Department of Transportation and Public Facilities bgs Below Ground Surface BIA Bureau of Indian Affairs CSM Conceptual Site Model cy Cubic Yards Discovery Discovery Drilling DRO Diesel Range Organics DQO Data Quality Objectives GAC Granulated Activated Carbon GRO Gasoline Range Organics HH Human Health IDW Investigation Derived Waste IHS Indian Health Service KIC Kikiktagruk Inupiat Corporation KICC Kikiktagruk Inupiat Corporation Construction LCS Laboratory Control Sample LCSD Laboratory Control Sample Duplicate LNAPL Light Non-Aqueous Phase Liquids LOQ Limits Quantitation MAC Maximum Allowable Concentration mg/kg Milligrams per Kilogram MTG Migration to Groundwater PAH Polyaromatic hydrocarbon PCE Tetrachloroethene PPE Personal Protective Equipment ppmv Parts Per Million By Volume QC Quality Control QEP Qualified Environmental Professional RPD Relative Percent Difference RRO Residual Range Organics SGS SGS North America, Inc.

TC-EM JV Tanana Commercial-Environmental Management JV USS United States Survey UST Underground Storage Tank VOC Volatile Organic Compound

Job # 17855, April 2021 1

2020 Site Characterization, Limited Removal Action, and Groundwater Monitoring Report

Former IHS/BIA Hospital – School Pipeline Release ADEC File No. 410.38.025

Kotzebue, Alaska

This report outlines the 2020 site characterization, limited removal action, and groundwater monitoring activities at the former Indian Health Service/Bureau of Indian Affairs (IHS/BIA) Hospital – School Pipeline (subject property) Release in Kotzebue, Alaska. The site is identified as Alaska Department of Environmental Conservation (ADEC) Contaminated Sites File No.

410.38.025.

Work was conducted by Tanana Commercial-Environmental Management JV, LLC (TC-EM JV) in accordance with the July 10, 2020 Professional Services Contract Amendment No. 3 from Maniilaq Association.

1.0 SITE DESCRIPTION AND BACKGROUND

The subject property is an active ADEC Contaminated Site and encompasses several lots in Kotzebue, Alaska. The following outlines the purpose of the monitoring and regulatory background, site location, and previous field activities.

1.1 Project Purpose and Objectives

The purpose of the project is to progress toward Cleanup Complete with Institutional Controls for the site. The project objectives include the following:

• Tilling of soils landfarmed from the 2019 underground storage tank (UST) removal action;

• Conduct a site characterization to delineate the extent of contamination on the parcels currently or formerly owned by IHS (Lots 3, 4, and 5);

• Monitoring of product from Monitoring Well MW1 on Lot 5;

• Investigation and sampling from the footprint of the former IHS tank farm located on Lot

5;

• Removal and treatment of contaminated soils greater than Human Health (HH) and/or

Maximum Allowable Concentrations (MAC) from Lot 3 (see work plan variance in Section 2.1); and

• Groundwater monitoring of the site’s ten existing wells (Lots 3 through 5 and Tract 4A).

1.2 Site Location

The ADEC Contaminated Site covers land in the area of the former IHS Hospital and BIA school. The source area consists of Tracts 1 and 4 of United States Survey (USS) 2083. The site is located in the northeast ¼ of the northwest ¼ of Section 3, Township 17 North, Range 18

Job # 17855, April 2021 2

West, Kateel River Meridian, Alaska (Kotzebue D-2 USGS Quadrangle). The Vicinity Map showing the general location of the project area is included as Figure 1.

The former IHS hospital was located between Second Avenue and Third Avenue, southwest of the current elementary school. The tank farm serving the hospital was located to the north along Second Avenue, near the intersection of Ocean Avenue.

The complete extent of contamination has not yet been determined and likely extends beyond the original ten acres of land and following parcels. The lots included in this assessment and their former uses are the following (WHPacific, 2015):

• Lot 3 – Former BIA school and small structures once part of the hospital; current residential

• Lot 4 – former hospital grounds (1928-1962); current pedestrian/public use, FRF Building (also known as the Ferguson Building)

• Lot 5 – former hospital grounds (1961-1996); current pedestrian/public use, fenced light industrial

• Tract 4A – former BIA fuel pipeline corridor to the 1961 hospital; current Kotzebue school complex

For the 2020 field activities, the field activities primarily focused on the former IHS lots including Lots 3, 4, and 5. In addition, groundwater monitoring of the wells near the former IHS hospital (MW-1, MW-2, MW-7, MW-8, and MW-10) was carried out concurrently with groundwater monitoring of the wells located near the former BIA school (MW-3 through MW-6, MW-9).

The landfarm property where the contaminated soil was placed is owned by Kikiktagruk Inupiat Corporation (KIC) and is located off of Base Road in Kotzebue. The soils were placed into the landfarm that was constructed in 2019 for the treatment of the soils removed during the UST removal effort associated with this project. KIC will maintain and manage the landfarm while the contaminated soil is being treated. The location of the Base Road landfarm is shown on Figure 1.

1.3 Background

Oil was first discovered in the Kotzebue Elementary School basement and are believed to be a combination of fuel storage tank releases, damaged fuel distribution line, fuel storage tank overfills and other sources (ADEC, 2015). In 1980 the ADEC became aware of the product release when fuel oil was being discharged from an oil-water separator located in the elementary school’s basement. The ADEC estimated during the initial investigation that between 100,000 and 200,000 gallons of diesel fuel had been released. Between 1979 and 1980 an estimated 100,000 gallons of fuel was pumped from the basement, and an estimated 40,000 gallons of fuel was recovered by ADEC contractors and citizens from recovery wells during 1980 and 1984.

(WHPacific, 2015)

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In 1986 the ADEC’s contractor evaluated the extent of contamination and decommissioning of the pipeline. ADEC’s contractor installed 25 monitoring wells and nine recovery wells. Within a month, all of the wells had evidence of fuel present. The pipeline was also exposed to a depth of less than 3 feet below ground surface and approximately 200 to 300 gallons of diesel was drained from the pipeline. The pipeline was then abandoned in place. (WH Pacific, 2015)

In 1988 an oil sheen was observed on the beach of Kotzebue Sound off of Shore Avenue.

Shannon & Wilson installed and operated an oil-recovery system in 1989 which included a 435-foot long fabric barrier to prevent migration, additional recovery/monitoring wells, and a 74-foot long oil recovery trench in Second Avenue, north of the former hospital. As much as 2 feet of floating fuel was observed in several wells, but an estimated 5,000 to 7,000 gallons of fuel remained in the ground. The collection efforts ceased after 1990. (S&W, 2010)

In 2008, local residents notified the ADEC that a seasonal sheen was observed in Kotzebue Sound off of Shore Avenue. The ADEC contracted with Shannon & Wilson to collect pore water samples along the beach and install vapor probes near the elementary school. Pore-water samples indicate contamination is entering Kotzebue Sound. With the exception of a probe installed near the former hospital, soil vapor samples were below screening levels. Shannon & Wilson was also tasked with monitoring and recovery well and oil-recovery gallery decommissioning. Of the 64 wells installed in the late 1980s, only 15 were located and of those only three were in good working conditions. The 12 wells were decommissioned. The oil-recovery gallery was unable to be located but the sample collected from the vicinity exceeded diesel range organic (DRO) levels. (S&W, 2010)

In 2010 the Alaska Department of Transportation and Public Facilities (ADOT&PF) installed of a sheet pile wall along the Shore Avenue. The sheet piles were installed along the tideline to approximately 25 feet below mean sea level and extend approximately 6 feet above the ground surface. The impact of this wall and migration towards Kotzebue Sound is unknown. (S&W, 2010)

In 2014 and 2015 WH Pacific conducted site investigations at the site. This included installation of four test pits, 45 soil borings, and 10 monitoring wells in 2014 in the vicinity of the abandoned in-place pipeline and areas of known or former contamination; groundwater sampling in 2014 and 2015; and a shallow soil gas survey in 2015. The highest concentrations were generally along the former BIA pipeline corridor on Tract 4A, and in the right-of-way area northwest of Building 314 and the FRF Building. The shallow soil gas survey did not indicate detectable levels of contaminants of concern in the school’s playground area. (WH Pacific, 2015)

In 2019, TC-EM JV conducted pre-excavation sampling, UST removal, and groundwater sampling. The UST removal activities focused on the UST and concrete dispensing island along the north side of the FRF Building. While the presumed storage use of the tank was for vehicle fueling that was discontinued sometime prior to 1969, waste oil was encountered in the UST at the time of the field activities. Approximately 16 cubic yards (cy) of contaminated soil was

Job # 17855, April 2021 4 removed during the UST removal activities and transported to KIC’s lined landfarm cell on Base Road in Kotzebue. Concentrations greater than the ADEC cleanup levels remain in the UST excavation and based on field screening and analytical results and fact the tank and piping appeared in good condition, the contamination appeared more consistent with the historical fuel oil that has contaminated the project area and not from a release from the UST. Groundwater sampling activities were also conducted during the August 2019 field activities. Measurable product was encountered in Well MW1, which is consistent with the 2014 field activities.

Contamination was present in the groundwater in each of the site’s wells, with the highest concentrations encountered in the wells along the former pipeline corridor. (TC-EM JV, 2019)

2.0 FIELD ACTIVITIES

The field activities were conducted by TC-EM JV in two phases. The first phase was conducted in July 2020 and included the site characterization activities. The second phase was conducted in September and October 2020 and included the soil removal activities and groundwater monitoring. In addition, landfarm maintenance and soil tilling were conducted by KIC Construction (KICC) throughout the summer, beginning in May and ending in August 2020.

Additional details on the field activities are described below. Field notes of the field activities are provided in Appendix A. Photographs of the field activities are provided in Appendix B.

2.1 Work Plan Variances

In general, the work followed the ADEC-approved work plan as written, with the following exceptions:

• The excavation extended to permafrost, which was approximately 2 feet below the soil-water interface. As a result, the base of the excavation was filled with water and soil samples could not be collected.

• Soil removal was to focus on removing contaminated soil exceeding ADEC HH/MAC cleanup levels within the footprint of Lot 3. However, results from the July 2020 site characterization activities indicated that concentrations did not exceed ADEC HH/MAC cleanup levels. As a result, the fall 2020 cleanup efforts focused on removing impacted soil from Lot 4.

• Additional borings were advanced to obtain additional information about the site conditions and several borings were shifted due to accessibility during the site characterization efforts. Additional details on the purpose and locations of these borings are described in further detail below in Section 2.2.

• Due to the time of year (late fall) and potential for soil sample results to not be received before freeze-up, the segregated “Potentially Clean” soil was placed back in the top 2 feet of the excavation prior to receipt of the confirmation soil sample results. ADEC approval of this variance was received on September 15, 2020.

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2.2 Site Characterization Activities

Between July 28 and 30, 2020, TC-EM JV conducted site characterization activities at the site.

The purpose of the sampling was to delineate the extent of contamination on the parcels currently or formerly owned by IHS (Lots 3, 4, and 5). Discovery Drilling (Discovery) provided the Geoprobe 54LT drill rig and operator to advance the soil borings (Photo 1). Hannah Deeney, EIT, was the Qualified Environmental Professional (QEP) conducted the sampling, and Dale Erickson coordinated the logistics for the field work.

A total of 16 borings were advanced as shown on Figure 2. These borings focused on the following areas and project objectives:

• Borings B5, B6, B7, B8, and B10. The residential structures on Lot 3 are planned to be demolished in the near future. To assist in planning, borings were advanced near the structures to determine if contamination may be present and to determine if soils generated during demolition will require special handling.

• Borings B1, B2, B3, B4, B15, and B16. Concentrations of petroleum contaminants greater than the ADEC Migration to Groundwater (MTG) cleanup levels but less than the ADEC HH/MAC cleanup levels have been detected in the soil along the northwest property boundary of Lot 3 during previous site investigations, noting the full suite of volatile organic compounds (VOC) and polyaromatic hydrocarbons (PAH) have not been analyzed in the samples collected from the lot. Additional characterization was conducted to delineate the extent of contamination and determine if other contaminants of concern are present.

• Borings B9 and B11. Soil borings were advanced in the unpaved areas of Lot 4 to assess whether there are discrete areas above ADEC HH/MAC cleanup levels that may be targets for fall 2020 remediation efforts.

• Boring B12. Soil samples were collected in the southern portion of Lot 5, which adjoins Lot 4, to determine the extent of contamination for future removal activities.

• Borings B13 and B14. The tanks associated with the former IHS tank farm are still present on the northwest portion of Lot 5. Soil samples will be collected adjacent to the tank farm to determine if a release occurred during the former use as a tank farm.

Each boring was advanced to groundwater. Field headspace readings were collected at 2-foot intervals. One analytical soil sample was submitted from each boring either from the soil-water interface or if there was indication of impact based on field screening results or field observations. Each boring was backfilled with soil cuttings after soil samples were collected.

2.3 Product Monitoring Activities

Product level measurements were collected during both field efforts for Monitoring Well MW1, due to the historical presence of free product in 2014 and 2019. An oil-water interface probe was

Job # 17855, April 2021 6 also used during the fall 2020 groundwater monitoring events to assess whether free product may also be present in the other site wells. Bailers were also placed into the well to confirm the presence of the product (Photo 2).

2.4 Soil Removal Activities

Soil removal activities were conducted between October 1 and 3, 2020 on the contaminated soil within the footprint of Lot 4. Temporary fencing and barriers were placed around the open excavation sections prior to trucks and equipment leaving the site each day.

Shayla Marshall served as the QEP and Dale Erickson provided logistical and field support. KIC Construction, LLC (KICC) provided the equipment and operators to conducted the soil removal.

Prior to advancing the excavation, KICC coordinated the utility locates and moved the connexes from the project site, and TC-EM JV demarcated the excavation area with spray paint (Photo 3).

The location of the October 2020 excavation is shown on Figure 3.

The soil was segregated during excavation activities into “Potentially Clean” and “Contaminated” soil based on the field screening methods outlined in in the work plan. The “Potentially Clean” material was temporarily stockpiled on a 10-mil liner on Lot 3, southeast of the FRF Building parking lot (Photo 4). Based on field headspace readings from the excavated soil, the top 2 feet of the excavation was deemed “Potentially Clean”. The top 2 feet of material was excavated from the demarcated footprint first prior to beginning the excavation of the “Contaminated” soil. A total of 56 cy of “Potentially Clean” material was generated.

Soil samples were collected from the “Potentially Clean” soil stockpile on October 3, 2020. This included collection of six field headspace samples from the stockpile at various locations and a minimum of 18 inches beneath the exposed surface (Photo 5).

During excavation various types of buried debris was encountered and free product entering the excavation was observed. The locations of the materials are shown on Figure 3. This debris included the following:

• Numerous drums were encountered on the south end of the excavation beginning at 8 inches below ground surface (bgs) and appeared to have been welded together to create an underground conveyance. The City of Kotzebue was notified and was unaware of the purpose of these drums. No petroleum-like odor or staining was observed in the soils surrounding the drums; field headspace readings collected from the soils directly beneath the drums ranged between 0.5 and 1.1 parts per million by volume (ppmv). A slight sewer odor was noted by the drums nearest to Lot 5. There were no residue or contents in the drums. Nine drums were removed from the excavation, crushed, and taken to the landfill for disposal. However, it appears the drums may extend beneath the FRF Building and into Lot 5. (Photos 6 and 7)

• An empty 20-foot, 4-inch steel pipe was observed on the north side of the excavation (Photo 8). The pipe was encountered between 6 and 8 inches bgs and was open on both

Job # 17855, April 2021 7 ends. No staining or petroleum odors were noted under the pipe or at the terminuses.

Field screening along the pipe ranged between 0.0 and 0.5 ppm. The City of Kotzebue was notified and was unaware of the purpose of this abandoned pipe, however, based on historical aerial photographs, the debris was encountered near former infrastructure from the former IHS hospital.

• Fiberglass, charred soil and wood, and firebrick were encountered along the northeast sidewall of the excavation beginning at approximately 4 feet bgs (Photos 9 through 11).

Due to the age of the former infrastructure and fibrous nature of the material, the excavation was stopped and a sample was collected to determine if they were asbestos-containing materials (ACM). The soil generated from that area was placed back into the excavation and the soils were wetted. ATC of Anchorage, Alaska determined that the samples did not contain ACM (see Appendix C). However, the results were not available until the excavation activities were complete, so the area was not excavated during the October 2020 field work.

• A 6-inch cement asbestos pipe was encountered on the interior corner of the excavation at approximately 2 feet bgs (Photo 12). The pipe was left in place. The uncovered area was open and did not appear to contain any contents, including petroleum product, or have any staining in the vicinity of the pipe. The pipe appears to extend towards and potentially beneath the FRF Building. The pipe, as well as much of the debris, was observed in the location of the former 1930s-1940s hospital that burned down. Cement asbestos piping was often used for conveying drinking water during that period of time and may have previously served the former hospital structure.

• During a 10-minute window around the low tide on October 2, 2020, a sheen was observed entering the excavation from the interior corner of the excavation. The sheen had mostly moved back towards the building and out of the standing water within the excavation once the tide changed (Photo 13).

The excavation extended until permafrost was reached (approximately 8 feet bgs) and a maximum of 170 cy of contaminated soil was excavated. The 170 cy was based on the remaining volume that can be placed in the KIC Landfarm cell that was constructed in 2019.

The soils generated in 2019 were moved to the west side of the cell and a silt fence was placed between the 2019 and 2020 soils (Photos 14 and 15). The “Contaminated” soil was direct-hauled to the KIC Landfarm and placed directly into the landfarm cell. The soil was spread on October 10, 2020 (Photos 16 and 17).

Upon completion of the excavation activities, soil samples were collected and a barrier curtain was placed around the excavation. The soil sampling frequency was based on the final excavation dimensions and the ADEC-approved work plan. Note, since water was present at the base of the excavation, soil samples could not be collected from the excavation base.

Job # 17855, April 2021 8

The barrier curtain was comprised of a 20-mil liner placed around the perimeter of the excavation. Due to the presence of the water table at 6 feet bgs, the liner was placed so that approximately 2 feet of material overlapped on the bottom of the excavation. Clean material was used to then secure the liner to the base of the excavation (Photo 18). The excavation was then backfilled with clean local borrow material from the Drake Gravel Pit in 1-foot lifts and graded and compacted with the excavation bucket until it reached approximately 2 feet above the groundwater interface zone (approximately 4 feet bgs) (Photo 19). At that depth, the liner was secured to the sidewalls of the excavation using rebar placed at 2 feet bgs and at 10-foot intervals to allow identification of excavation extents in the future using a metal detector or other geophysical equipment (Photo 20). The liner was cut right above the rebar. A ramp was also constructed to enable a wheel roller to enter the excavation for compaction at 1-foot lifts (Photo 21). The clean local borrow material from the Drake Gravel Pit was used to backfill the excavation to 2 feet bgs, and the segregated “Potentially Clean” soil stockpile was used to backfill from 2 feet bgs to the surface of the excavation. An excavation plan showing the placement of the barrier curtain is provided as Figure 6.

2.5 Landfarm Soil Treatment and Maintenance

KICC perform the landfarm treatment and maintenance throughout the summer of 2020. The soil was tilled on a bi-weekly basis or when weather allowed using a hand rake, due to the depth of soil and to prevent damage to the liner. KICC performed landfarm maintenance on the following dates:

• May 14, 2020

• June 24, 2020

• June 30, 2020

• July 18, 2020

• August 7, 2020

• August 16, 2020

During landfarm tilling events and after large rain events, KICC also removed excess water from the inside of the landfarm. The water was pumped using a sump pump into a fabric filter and then into an on-site granulated activated carbon (GAC) system (Photo 22). The treated water was then discharged to the vegetated area outside of the landfarm. Nutrients were added to the soil on June 24, 2020; due to the high moisture content in the soils, it was decided to place the fertilizer at this time instead of during the initial tilling event on May 14, 2020.

During the August 7, 2020 tilling event, the landfarm liner was damaged. While KICC personnel were moving the GAC filter, the fork lift sunk into the landfarm on the north side of the cell and tore the liner. A 12 feet by 14 feet patch using 20-mil liner and two-sided repair tape specifically designed for liners was used to repair the liner.

On October 10, 2020, the soils generated during the 2020 field effort were spread into the remaining landfarm cell (Photos 16 and 17). The soils were placed at an approximately 12-inch

Job # 17855, April 2021 9 depth. Due to the late season and freezing conditions, it was decided that the nutrients will be better placed in the spring/early summer 2021.

The landfarm was completed with snow fence and a sign denoting the soils generated from this project (Photo 14).

2.6 Groundwater Monitoring Activities

Groundwater sampling was conducted on the site’s ten monitoring wells on September 30, October 3, and October 4, 2020. The locations of the monitoring wells are shown on Figure 7.

2.6.1 Water Level Measurements and Flow Direction

Water level measurements were collected for the site’s wells on September 30, 2020. The measurements were collected near low tide, noting the tidal variance on September 30, 2020 was

0.02 feet at low tide and 0.55 feet at high tide according to the National Oceanic and Atmospheric Administration.

2.6.2 Groundwater Sampling

Groundwater sampling proceeded after water levels were collected from each of the wells.

Analytical samples were collected in eight of the ten wells. Due to the presence of product in Wells MW1 (0.01 foot) and MW6 (trace), analytical samples were not collected (Photos 2 and 23). Sheen was observed in the purgewater from Wells MW8 and MW9 (Photos 24 and 25).

Well MW8 was located beneath a vehicle that was being staged on Lot 5 to be later drained of fluids and shipped outside of Kotzebue for disposal (Photo 26). The remaining wells were accessible and in good condition.

3.0 SAMPLING RESULTS

The samples were submitted to SGS North America, Inc. (SGS) laboratory in Anchorage, Alaska for sample analysis. The soil and groundwater results are described in further detail below.

3.1 Subsurface Conditions

Soils at the site consisted of primarily a brown sand and gravel. All soils had relatively low organic content. Groundwater was encountered between 4.5 and 5.5 feet bgs during the field activities. Petroleum odors were encountered in Borings B1, B2, and B12 through B14. Black stained soils were encountered at the groundwater interface zone in Borings B5 and B10.

Globules of light non-aqueous phase liquids (LNAPL) were not encountered in the borings.

Permafrost was encountered between 7 and 8 feet bgs at the time of drilling. Boring logs describing the subsurface conditions are included in Appendix E.

3.2 Site Characterization Results

Soil samples were collected between July 28 and 30, 2020 from 16 borings placed across the project site. The purpose of the sampling was to determine if there are areas that exceed ADEC HH/MAC cleanup levels.

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Two field headspace readings were collected from each sampling sleeve. The field headspace results are shown on the boring lots included in Appendix E. The highest headspace readings were encountered in the borings along the School Utility Road (Borings B1, B2, B11, B13, and 14). The headspace samples with the highest headspace readings from each boring were submitted for analysis. Table 1 summarizes the analytical results and comparison to ADEC Method Two Cleanup Levels (Under 40-inch zone). The laboratory report is provided in Appendix D.

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Table 1 – Summary of July 2020 Site Characterization Analytical Results

Analyte Analysis Unit

ADEC Cleanup Level Sample ID**

MTG* HH/MAC* B1 6-8 B1 8-10~ B2 6-8 B3 4-6 B4 6-8 B5 6-8 B6 4-6 B7 4-6 B8 4-6

Sample Depth - ft - - 6-8 6-8 6-8 4-6 6-8 6-8 4-6 4-6 4-6 Field Headspace Result MiniRae ppm - - 485.5 485.5 504.2 1 75.3 212.5 4.7 0.2 0.1 GRO AK101 mg/Kg 300 1400 29.8 23.4 14.2 1.36 U 2.33 U 2.78 3.44 U 2.04 U 2.39 U DRO AK102 mg/Kg 250 10250 6540 6760 4320 20.5 U 553 1940 141 28.6 45.4 Lead SW6020B mg/Kg 800 400 3.14 4.83 3.03 3.32 3.16 3.96 30.0 8.52 120 Polyaromatic Hydrocarbons

1-Methylnaphthalene 8270D SIM ug/Kg 410 68000 10100 - - - - - - - - 2-Methylnaphthalene 8270D SIM ug/Kg 1300 310000 7420 - - - - - - - - Fluorene 8270D SIM ug/Kg 36000 3100000 1490 - - - - - - - - Naphthalene 8270D SIM ug/Kg 38 29000 888 U - - - - - - - - Phenanthrene 8270D SIM ug/Kg 39000 2300000 1580 - - - - - - - - Pyrene 8270D SIM ug/Kg 87000 2300000 163 - - - - - - - - Other PAHs 8270D SIM ug/Kg varies varies ND - - - - - - - -

Volatile Organic Compounds 1,2,4-Trimethylbenzene SW8260D ug/Kg 610 43000 391 693 641 27.2 U 46.6 U 35.7 U 68.7 U 40.8 U 47.7 U 1,3,5-Trimethylbenzene SW8260D ug/Kg 660 37000 1200 1350 756 13.6 U 23.3 U 17.8 U 34.4 U 20.4 U 23.9 U 4-Isopropyltoluene SW8260D ug/Kg - - 112 77.7 U 232 54.4 U 93.3 U 71.4 U 137 U 81.5 U 95.4 U Benzene SW8260D ug/Kg 22 11000 9.69 U 9.71 U 10.1 U 6.81 U 11.7 U 8.92 U 17.2 U 10.2 U 11.9 U Ethylbenzene SW8260D ug/Kg 130 49000 19.4 U 19.4 U 20.2 U 13.6 U 23.3 U 17.8 U 34.4 U 20.4 U 23.9 U Isopropylbenzene SW8260D ug/Kg 5600 54000 19.4 U 19.4 U 23.6 13.6 U 23.3 U 17.8 U 34.4 U 20.4 U 23.9 U Naphthalene SW8260D ug/Kg 38 29000 424 542 287 13.6 U 23.3 U 40.3 34.4 U 20.4 U 23.9 U Trichlorofluoromethane SW8260D ug/Kg 41000 980000 50.4 47.4 40.5 U 27.2 U 46.6 U 35.7 U 68.7 U 40.8 U 47.7 U Xylenes (total) SW8260D ug/Kg 1500 57000 58.1 U 58.3 U 60.7 U 40.8 U 69.9 U 53.5 U 103 U 61.1 U 71.6 U n-Propylbenzene SW8260D ug/Kg 9100 52000 19.4 U 19.4 U 71.8 13.6 U 23.3 U 17.8 U 34.4 U 20.4 U 23.9 U sec-Butylbenzene SW8260D ug/Kg 42000 28000 65.8 96.8 294 13.6 U 23.3 U 17.8 U 34.4 U 20.4 U 23.9 U tert-Butylbenzene SW8260D ug/Kg 11000 35000 19.4 U 36.1 26.9 13.6 U 23.3 U 17.8 U 34.4 U 20.4 U 23.9 U Other VOCs SW8260D ug/Kg varies varies ND ND ND ND ND ND ND ND ND

Notes on the following page

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Table 1– Summary of July 2020 Site Characterization Analytical Results (continued)

Analyte Analysis

ADEC Cleanup Level* Sample ID**

Unit MTG HH/MAC B9 6-8 B9 8-10~ B10 6-8 B11 4-6 B12 2-4 B13 4-6 B14 4-6 B15 6-8 B16 6-8 Sample Depth - ft - - 6-8 6-8 6-8 4-6 2-4 4-6 4-6 6-8 6-8 Field Headspace Result MiniRae ppm - - 264.5 264.5 317.1 537.8 493 435.3 595.7 392.2 370.9 Gasoline Range Organics AK101 mg/Kg 300 1400 156 52.2 3.47 43.6 19.1 39.5 9.53 20.2 36.1 Diesel Range Organics AK102 mg/Kg 250 10250 2930 2290 2970 11900 63100 17000 15200 8270 5930 Lead SW6020B mg/Kg 800 400 4.12 2.35 4.06 3.68 15.8 4.77 5.24 2.25 2.55 Polyaromatic Hydrocarbons

1-Methylnaphthalene 8270D SIM ug/Kg 410 68000 - - - 33200 - - - - - 2-Methylnaphthalene 8270D SIM ug/Kg 1300 310000 - - - 34700 - - - - - Fluorene 8270D SIM ug/Kg 36000 3100000 - - - 3640 - - - - - Naphthalene 8270D SIM ug/Kg 38 29000 - - - 9560 - - - - - Phenanthrene 8270D SIM ug/Kg 39000 2300000 - - - 4240 - - - - - Pyrene 8270D SIM ug/Kg 87000 2300000 - - - 252 - - - - - Other PAHs 8270D SIM ug/Kg varies varies - - - ND - - - - -

Volatile Organic Compounds 1,2,4-Trimethylbenzene SW8260D ug/Kg 610 43000 1250 804 38.5 U 5260 2050 9360 11100 373 440 1,3,5-Trimethylbenzene SW8260D ug/Kg 660 37000 1970 1300 19.3 U 4870 2270 3090 4560 1370 1090 4-Isopropyltoluene SW8260D ug/Kg - - 763 476 77.1 U 842 U 245 U 1380 U 713 94.8 287 Benzene SW8260D ug/Kg 22 11000 26.4 U 11.2 U 9.64 U 105 U 30.6 U 173 U 109 10.3 U 11.1 U Ethylbenzene SW8260D ug/Kg 130 49000 52.8 U 22.5 U 19.3 U 211 U 61.2 U 1080 204 20.5 U 22.1 U Isopropylbenzene SW8260D ug/Kg 5600 54000 60.7 42.7 19.3 U 211 U 61.2 U 792 681 20.5 U 22.1 U Naphthalene SW8260D ug/Kg 38 29000 535 364 35.7 8490 5860 13700 10300 390 316 Trichlorofluoromethane SW8260D ug/Kg 41000 980000 106 U 44.9 U 38.5 U 421 U 122 U 692 U 229 U 41.1 U 44.2 U Xylenes (total) SW8260D ug/Kg 1500 57000 158 U 67.4 U 57.8 U 805 1170 3950 3860 61.6 U 66.4 U n-Propylbenzene SW8260D ug/Kg 9100 52000 52.8 U 41.2 19.3 U 211 U 61.2 U 973 1020 20.5 U 29.9 sec-Butylbenzene SW8260D ug/Kg 42000 28000 460 305 19.3 U 301 92.4 744 1160 70.3 306 tert-Butylbenzene SW8260D ug/Kg 11000 35000 88.2 58.9 19.3 U 211 U 61.2 U 346 U 117 38.0 42.6 Other VOCs SW8260D ug/Kg varies varies ND ND ND ND ND ND ND ND ND

Notes on the following page

Job # 17855, April 2021 13

Notes:

* Tables B1 or B2, Migration to Groundwater (MTG) or Human Health (HH)/Maximum Allowable Concentration (MAC), Method Two Soil Cleanup Levels (18 AAC 75, October 27, 2018)

** Sample Number proceeded by TC-EM JV Job Number, 17855, on COC 535 Above ADEC MTG Cleanup Level

15200 Above ADEC HH/MAC Cleanup Level mg/kg Milligrams per kilogram ug/kg Micrograms per kilogram

19.3 U Concentration not detected Above the Limit of Quantitation (LOQ)

211 U Concentration not detected Above the LOQ, but LOQ is greater than the ADEC Cleanup Level

35.7 Detectable concentration reported in the project sample

- Not analyzed ND Not detected

3.3 Product Monitoring Results

Product monitoring of Well MW1 was conducted during the July and September-October 2020 field events. MW1 contained 0.5 feet of product on July 29, 2020 and 0.01 feet on September 30, 2020. The remaining wells were checked on September 30, 2020. Although the product interface probe did not indicate free product in the remaining nine wells, during the purging of Well MW6, free product was observed on the edges of the purge bucket.

3.4 Soil Removal Results

3.4.1 Stockpile Sample Results

Field screening samples were collected from the segregated “Potentially Clean” stockpile generated from the excavation on October 3, 2020 prior to use as excavation backfill. Table 3 summarizes the stockpile headspace results.

Table 2 – Summary of Stockpile Headspace Results

Field Sample

ID

Headspace Result (ppmv)

Depth above ground surface (ft)*

SP1 11.1 4

SP2 1.4 5

SP3 10.2 2

SP4 2.2 4

SP5 13.9 1

SP6 12.6 4

Notes:

* Collected from 18 inches below stockpile surface

308 Indicates reading used to select laboratory sample locations

Based on headspace results a total of three analytical soil samples, plus one duplicate, were collected on October 3, 2020 and analyzed. Analytical results are shown in Table 3. The laboratory report is provided in Appendix D.

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Table 3 – Summary of Stockpile Analytical Results

Analyte Analysis Unit

ADEC

Cleanup

MTG

ADEC

Cleanup

HH 17855-SP1 17855-SP21~ 17855-SP5 17855-SP6

Field Headspace MiniRae 3000 ppmv - - 11.1 11.1 13.9 12.6 Sample Depth - ft ags - - 4 4 1 4 GRO AK101 mg/kg 300 1400 2.56 U 2.42 U 2.52 U 2.32 U DRO AK102 mg/kg 250 10250 357 253 197 152 Lead SW6020B mg/kg 800 400 158 154 53.7 117 Volatile Organic Compounds

Toluene SW8260D ug/kg 6700 200000 25.6 U 24.2 U 25.2 U 34.6 Other VOCs SW8260D ug/kg varies varies ND ND ND ND

3.4.2 Excavation Confirmation Sample Results

Field screening samples were collected from the excavation sidewalls on October 2, 2020 prior to installation of the barrier curtain. Since the water table was encountered at approximately 6 feet bgs and the excavation extended to permafrost at approximately 8 feet bgs, no base samples were collected. Table 4 summarizes the excavation headspace results.

Table 4 – Summary of Excavation Headspace Results

South Sidewall Northwest Sidewall Northeast Sidewall Field

Sample

ID

Headspace Result (ppmv)

Depth (ft)

Field Sample

ID

Headspace Result (ppmv)

Depth (ft)

Field Sample

ID

Headspace Result (ppmv)

Depth (ft)

ExS1 188 4 ExNW1 16.0 4 ExNE1 132 4 ExS2 142 4 ExNW2 6.7 4 ExNE2 197 4 ExS3 265 4 ExNW3 108 4 ExNE3 283 4 ExS4 23.9 4 ExNW4 7.3 2 ExNE4 263 6 ExS5 255 4 ExNW5 161 4 ExNE5 283 4 ExS6 30.0 4 ExNW6 281 4 ExNE6 264 2 ExS7 73.3 4 ExNW7 11.7 2 ExNE7 191 4 ExS8 112 4 ExNW8 212 4 ExNE8 274 2 ExS9 167 4 ExNW9 18.2 2 ExNE9 28.7 4

ExS10 144 2 ExNW10 10.3 6 ExNE10 103 4 ExS11 225 2 ExNW11 48.2 6 ExNE11 254 2 ExS12 14.5 2 ExNW12 21.7 6 ExNE12 174 4

* Tables B1 or B2, Migration to Groundwater (MTG) or Human Health (HH) for Under 40 Inch Zone, Method Two Soil Cleanup Levels (18 AAC 75, October 27, 2018)

357 Above ADEC MTG Cleanup Level ~ Duplicate of proceeding sample ags Above ground surface mg/kg Milligrams per kilogram

2.56 U Concentration not detected Above the Limit of Quantitation (LOQ)

158 Detectable concentration reported in the project sample

- Not analyzed

ND Not detected

Job # 17855, April 2021 15

South Sidewall Northwest Sidewall Northeast Sidewall Field

Sample

ID

Headspace Result (ppmv)

Depth (ft)

Field Sample

ID

Headspace Result (ppmv)

Depth (ft)

Field Sample

ID

Headspace Result (ppmv)

Depth (ft)

ExS13 182 2 ExNW13 8.5 2 ExNE13 336 6 ExS14 35.8 2 ExNW14 8.8 6 ExNE14 241 2 ExS15 15.4 6 ExNW15 293 6 ExNE15 330 6 ExS16 29.9 6 ExNW16 5.6 2 ExNE16 282 2 ExS17 212 6 ExNW17 242 2 ExNE17 287 6 ExS18 208 6 ExNW18 375 2 ExNE18 242 2 ExS19 208 6 ExNW19 67.9 2 ExNE19 152 6 ExS20 263 6 ExNW20 143 4 ExNE20 221 6 ExS21 32.3 6 ExNW21 84.9 4 ExNE21 257 2 ExS22 14.5 6 ExNW22 17.3 6 ExNE22 272 4 ExS23 15.8 2 ExNW23 12.0 2 ExNE23 255 6 ExS24 8.1 4 ExNW24 14.7 4 ExNE24 201 2 ExS25 9.2 6 ExNW25 9.8 6 ExNE25 218 2 ExS26 11.0 2 ExNW26 8.2 4 ExNE26 294 2 ExS27 300 6 ExNW27 89.8 6 ExNE27 238 6 ExS28 70 4 ExNW28 8.1 6 ExNE28 239 4 ExS29 112 6 ExNW29 45.3 6 ExNE29 265 4 ExS30 92.1 2 ExNW30 289 4 ExNE30 359 6 ExS31 123 4 ExNW31 130 4 ExNE31 198 4 ExS32 100 4 ExNW32 188 2 ExNE32 204 6

ExNW33 308 6 ExNW34 21.39 4 ExNW35 251 6 ExNW36 270 6 ExNW37 355 4 ExNW38 194 6 ExNW39 278 2

308 Indicates reading used to select laboratory sample locations

Based on headspace results and per the ADEC-approved work plan, a total of nine analytical soil samples, plus one duplicate, were collected on October 2, 2020 and analyzed. Locations of screening and analytical samples are shown on Figures 4 and 5, respectively. Analytical results are shown in Table 5. The laboratory report is provided in Appendix D.

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Table 5 – Summary of Detectable Excavation Analytical Results

Analyte Analysis Unit ADEC Cleanup

Level Sample ID**

MTG HH/MAC EXS27 EXS3 EXS20 EXNW18 EXNW218~ EXNW33 EXNW37 EXNE13 EXNE30 EXNE15

Field Headspace MiniRae ppmv - - 300 265 263 375 375 308 355 336 359 330

Sample Depth - ft - - 6 4 6 2 2 6 4 6 6 6

GRO AK101 mg/kg 300 1400 101 14.1 230 36.4 72.4 21.0 83.7 53.6 75.0 5.99

DRO AK102 mg/kg 250 10250 9280 6770 5970 14800 9970 5360 9460 3790 5450 372

Lead SW6020B mg/kg 800 400 2.97 4.21 54.6 50.2 66.0 3.17 3.45 30.7 8.86 149

Volatile Organic Compounds 1,2,4- Trimethylbenzene SW8260D ug/kg 610 43000 148 U 37.7 U 275 U 107 310 40.7 U 196 U 1040 5830 92.7

1,3,5- Trimethylbenzene SW8260D ug/kg 660 37000 3430 51.3 4000 1020 1370 457 806 666 4100 84.9

Naphthalene SW8260D ug/kg 38 29000 1470 240 1880 309 412 88.9 918 1610 7940 204

Toluene SW8260D ug/kg 6700 200000 74.2 U 18.8 U 137 U 22.5 U 24.9 U 20.4 U 19.6 U 18.6 U 216 U 33.5 U

Xylenes (total) SW8260D ug/kg 1500 57000 222 U 56.5 U 412 U 67.5 U 123 61.1 U 58.8 U 206 1030 100 U n-Propylbenzene SW8260D ug/kg 9100 52000 74.2 U 18.8 U 137 U 22.5 U 24.9 U 20.4 U 98.0 U 25.8 216 U 33.5 U sec-Butylbenzene SW8260D ug/kg 42000 28000 74.2 U 18.8 U 137 U 22.5 U 24.9 U 20.4 U 98.0 U 76.2 489 33.5 U tert-Butylbenzene SW8260D ug/kg 11000 35000 74.2 U 18.8 U 137 U 35.4 47.0 20.4 U 98.0 U 20.0 216 U 33.5 U

Other VOCs SW8260D ug/kg varies varies ND ND ND ND ND ND ND ND ND ND

Polyaromatic Hydrocarbons

1-Methylnaphthalene 8270D SIM ug/kg 410 68000 - - - 34800 - - - - 8780 -

2-Methylnaphthalene 8270D SIM ug/kg 1300 310000 - - - 14100 - - - - 8800 -

Acenaphthene 8270D SIM ug/kg 37000 4600000 - - - 1370 - - - - 1040 U -

Fluorene 8270D SIM ug/kg 36000 3100000 - - - 3390 - - - - 1040 U -

Naphthalene 8270D SIM ug/kg 38 29000 - - - 839 U - - - - 3660 -

Phenanthrene 8270D SIM ug/kg 39000 2300000 - - - 4100 - - - - 1160 -

Pyrene 8270D SIM ug/kg 87000 2300000 - - - 462 - - - - 167 -

Other PAHs 8270D SIM ug/kg varies varies - - - ND - - - - ND -

Job # 17855, April 2021 17

* Tables B1 or B2, Migration to Groundwater (MTG) or Human Health (HH)/Maximum Allowable Concentration (MAC), Method Two Soil Cleanup Levels (18 AAC 75, October 27, 2018)

** Sample Number proceeded by TC-EM JV Job Number, 17855, on COC 3660 Above ADEC MTG Cleanup Level

14800 Above ADEC HH/MAC Cleanup Level mg/kg Milligrams per kilogram ug/kg Micrograms per kilogram

18.8 U Concentration not detected Above the Limit of Quantitation (LOQ) 839 U Concentration not detected Above the LOQ, but LOQ is greater than the ADEC Cleanup Level 101 Detectable concentration reported in the project sample

- Not analyzed ND Not detected bgs Below ground surface ~ Duplicate Sample of Proceeding Sample

3.5 Groundwater Monitoring Results

Water level measurements were collected from the site wells on September 30, 2020. A summary of the water level elevations and notable observations from the September-October 2020 groundwater monitoring event is provided in Table 6.

Table 6 – Groundwater Levels and Elevations

TOC

Elevation

(ft)

Total Well Depth

(ft BTOC)

Depth to Water

(ft BTOC)

Water Level Elevation

(ft)

Well Date Notes MW1 9/30/2020 8.62 7.48 - 6.20 0.10 feet of product

MW2 9/30/2020 10.05 7.90 4.97 5.08

MW3 9/30/2020 9.54 9.47 4.80 4.74

MW4 9/30/2020 9.17 12.42 4.43 4.74

MW5 9/30/2020 9.27 8.00 5.34 3.99

MW6 9/30/2020 9.33 - 5.04 NA Blockage at 6.00 feet BTOC; trace product

MW7 9/30/2020 10.50 12.95 5.73 4.77

MW8 9/30/2020 10.06 14.20 5.32 4.74

MW9 9/30/2020 8.42 12.35 3.83 4.59 Sheen and POL odor MW10 9/30/2020 9.28 12.70 4.70 4.58 Sheen and POL odor

Notes:

ft feet

BTOC Below Top of Casing POL Petroleum Oil and Lubricants

As shown on Figure 7, the groundwater direction appears to be to the north-northwest.

Samples were collected from the eight of the ten groundwater monitoring wells on October 3 and 4, 2020. Analytical sample was not collected from Monitoring Wells MW1 and MW6 due to the presence of product in the wells. Groundwater analytical results are shown in Table 7. The laboratory report is provided in Appendix D.

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Table 7 – Summary of Detectable Groundwater Analytical Results

Analyte Analysis Unit

ADEC

Cleanup

Level

Sample ID**

MW2 MW3 MW4 MW5 MW7 MW27~ MW8 MW9 MW10 MW20~

GRO AK101 mg/L 2.2 0.100 U 0.100 U 0.100 U 0.100 U 0.100 U 0.100 U 0.100 U 0.373 0.261 0.261 DRO AK102/103 mg/L 1.5 0.922 0.647 5.60 6.00 1.56 1.56 1.10 13.7 17.9 17.8 RRO AK102/103 mg/L 1.1 0.875 0.500 U 0.995 1.10 0.889 0.933 0.862 1.87 2.41 2.74 Polyaromatic Hydrocarbons

1-Methylnaphthalene 8270D SIM ug/L 11 - - - - - - - - 18.9 - 2-Methylnaphthalene 8270D SIM ug/L 36 - - - - - - - - 3.26 - Fluorene 8270D SIM ug/L 290 - - - - - - - - 1.05 - Naphthalene 8270D SIM ug/L 1.7 - - - - - - - - 32.0 - Phenanthrene 8270D SIM ug/L 170 - - - - - - - - 0.330 - Other PAHs 8270D SIM ug/L varies - - - - - - - - ND -

Volatile Organic Compounds 1,2,4-Trimethylbenzene SW8260D ug/L 56 1.00 UJ- 1.00 UJ- 1.46 J- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 40.0 J- 23.5 J- 26.9 J- 1,3,5-Trimethylbenzene SW8260D ug/L 30 1.00 UJ- 1.00 UJ- 10.7 J- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 39.0 J- 9.63 J- 10.6 J- 4-Isopropyltoluene SW8260D ug/L - 1.00 UJ- 1.00 UJ- 2.08 J- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 4.50 J- 3.81 J- 4.09 J- Benzene SW8260D ug/L 4.6 0.400 UJ- 0.400 UJ- 0.400 UJ- - 0.400 UJ- 0.400 UJ- 0.620 J- 64.7 J- 14.7 J- 17.2 J- Chloroform SW8260D ug/L 2.2 32.5 J- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 6.52 J- 1.00 UJ- 1.00 UJ- 1.00 UJ- Dichlorodifluoromethane SW8260D ug/L 200 3.58 J- 3.68 J- 1.00 UJ- - 1.00 UJ- 1.07 J- 1.38 J- 1.52 J- 1.00 UJ- 1.00 UJ- Ethylbenzene SW8260D ug/L 15 1.00 UJ- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 7.53 J- 23.0 J- 24.5 J- Isopropylbenzene SW8260D ug/L 450 1.00 UJ- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 7.26 J- 7.54 J 8.25 J Naphthalene SW8260D ug/L 1.7 1.00 UJ- 1.00 UJ- 3.21 J- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 84.1 J- 77.5 J- 81.6 J- Tetrachloroethene SW8260D ug/L 41 10.7 J- 107 J- 46.4 J- - 58.4 J- 52.0 J- 27.1 J- 38.1 J- 97.5 J- 69.9 J- Trichlorofluoromethane SW8260D ug/L 5200 30.2 J- 30.1 J- 3.61 J- - 1.00 UJ- 1.00 UJ- 6.91 J- 6.75 J- 1.00 UJ- 1.00 UJ- Xylenes (total) SW8260D ug/L 190 3.00 UJ- 3.00 UJ- 3.00 UJ- - 3.00 UJ- 3.00 UJ- 3.00 UJ- 9.19 J- 25.7 J- 28.7 J-n-Butylbenzene SW8260D ug/L 1000 1.00 UJ- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 1.00 UJ- 2.20 J- 2.39 J-n-Propylbenzene SW8260D ug/L 660 1.00 UJ- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 8.52 J- 8.81 J- 9.78 J-sec-Butylbenzene SW8260D ug/L 2000 1.00 UJ- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 6.02 J- 4.70 J- 5.14 J-tert-Butylbenzene SW8260D ug/L 690 1.00 UJ- 1.00 UJ- 1.00 UJ- - 1.00 UJ- 1.00 UJ- 1.00 UJ- 1.06 J- 1.00 UJ- 1.00 UJ- Other VOCs SW8260D ug/L varies ND ND ND - ND ND ND ND ND ND

* Table C Groundwater Cleanup Levels (18 AAC 75, October 27, 2018) 0.400 U Concentration not detected Above the Limit of Quantitation (LOQ)

** Sample Number proceeded by TC-EM JV Job Number, 17855, on COC 1.00 U Concentration not detected Above the LOQ, but LOQ is greater than the ADEC Cleanup Level

5.60 Above ADEC Cleanup Level J- Sample analyzed past hold time; concentration may be biased low mg/L Milligrams per kilogram 0.922 Detectable concentration reported in the project sample ug/L Micrograms per kilogram - Not analyzed

~ Duplicate of proceeding sample

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4.0 DISCUSSION

A discussion of the results from the July 2020 site characterization activities, product monitoring, September-October 2020 limited removal activities and groundwater monitoring, and landfarming efforts are described in further detail below.

4.1 Site Characterization Discussion

A total of 16 borings were advanced in July 2020. Borings B5 through B8 and B10 were advanced near the residential structures on Lot 3 to determine if contamination may be present and to determine if soils generated during demolition will require special handling. DRO concentrations greater than the ADEC MTG cleanup level were encountered in Borings B5 and B10, and naphthalene was slightly above the ADEC MTG cleanup level in Boring B5. Note all the samples from these borings were collected from the groundwater-interface zone and field screening samples collected above the groundwater-interface zone ranged between 0.0 and 4.7 ppm.

Borings B1 through B4, B15, and B16 were advanced along the northwest property boundary of Lot 3 to delineate the extent of contamination and determine if other contaminants of concern are present. With the exception of Boring B3, concentrations greater than the ADEC MTG but less than HH/MAC cleanup levels were encountered in each of the borings.

Borings B9 and B11 were advanced in the unpaved areas of Lot 4 to assess whether there are discrete areas above ADEC HH/MAC cleanup levels that may be targets for the fall 2020 remediation efforts. The sample from Boring B11 contained DRO at a concentration greater than the ADEC MAC cleanup level. Boring B11 was placed on the west (ocean) side of the FRF Building, approximately 70 feet from Monitoring Well MW1 where product has been consistently encountered.

Boring B12 was advanced on Lot 5 and was placed to determine the extent of contamination for future removal efforts. The DRO concentration of 63,100 mg/kg was well over the ADEC MAC cleanup level of 10,250 milligrams per kilogram (mg/kg) and was the highest concentration reported in the soil samples collected during the July 2020 site characterization activities. The groundwater interface zone, encountered between 2 and 4 feet bgs, in this boring was also shallower than the other borings.

Borings B13 and B14 were advanced in the vicinity of the former IHS tank farm that is still present on Lot 5.