2019_Underground_Storage_Tank_Removal_and_Groundwater_Monitoring_Rpt_0001.pdf

2019 Underground Storage Tank Removal and

Groundwater Monitoring Report

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

December 2019

2019 UST Removal and Groundwater Monitoring Report Former IHS/BIA Hospital – School Pipeline Release Job # 17855, December 2019 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 Pre-Excavation Soil Characterization

2.3 Landfarm Construction

2.4 UST Removal and Sampling

2.4.1 Piping Removal

2.4.2 Tank Removal

2.4.3 Excavated Soil Characterization

2.4.4 UST Contents Waste Characterization

2.4.5 UST Analytical Suite

2.5 Groundwater Monitoring Well Sampling and Survey

2.5.1 Tidal Monitoring

2.5.2 Groundwater Sampling and Well Conditions

2.5.3 Groundwater Sampling Analytical Suite

2.5.4 Level Loop Survey

3.0 SAMPLING RESULTS

3.1 Subsurface Conditions

3.2 Pre-Excavation Soil Characterization Results

3.3 UST Excavation Soil Characterization Results

3.4 UST Waste Characterization Results

3.5 Groundwater Monitoring Results

4.0 DISCUSSION

4.1 UST Excavation and Waste Characterization Discussion

4.2 UST Waste Characterization Discussion

4.3 Groundwater Monitoring Discussion

5.0 QUALITY CONTROL REVIEW

5.1 SGS Report 1193069 Pre-Excavation Soil Characterization Samples

5.2 SGS Report 1194483 UST Waste Characterization Samples

5.3 SGS Report 1194509 Groundwater Samples

5.4 SGS Report 1194525 UST Excavation Soil Samples

6.0 INVESTIGATIVE DERIVED WASTE MANAGEMENT

7.0 CONCLUSIONS AND RECOMMENDATIONS

8.0 REFERENCES

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TABLES

Table 1 – Summary of Pre-Excavation Soil Characterization Analytical Results Table 2 – Summary of UST Removal Headspace Results Table 3 – Summary of UST Removal Detectable Analytical Results Table 4 – Summary of UST Waste Contents Analytical Results Table 5 – Groundwater Levels and Elevations Table 6 – Summary of Detectable Groundwater Analytical Results Table 7 – Historical Groundwater Sampling Results

FIGURES

Figure 1 – Vicinity Map Figure 2 – Sampling Locations Figure 3 – UST Excavation Site Plan Figure 4 – UST Excavation Figure 5 – Groundwater Elevation and Flow Direction

APPENDICES

Appendix A – Field Notes Appendix B – Photo Pages Appendix C – Completed ADEC UST Forms Appendix D – SGS Laboratory Reports and Laboratory Data Review Checklist Appendix E – SGS Laboratory Report Chromatogram and Fuels Library Appendix F – Waste Manifest

Job # 17855, December 2019 iii

ACRONYMS AND ABBREVIATIONS

AAC Alaska Administrative Code ADEC Alaska Department of Environmental Conservation ADOT&PF Alaska Department of Transportation and Public Facilities AK Alaska bgs Below Ground Surface BIA Bureau of Indian Affairs CFR Code of Federal Regulations DRO Diesel Range Organics DQO Data Quality Objectives EPA Environmental Protection Agency GAC Granulated Activated Carbon GRO Gasoline Range Organics HH Human Health IDW Investigation Derived Waste IHS Indian Health Service KIC Kikiktagruk Inupiat Corporation LEL Lower Explosive Limit MAC Maximum Allowable Concentration mg/kg Milligrams per Kilogram ug/L Micrograms per Liter mm Millimeters MTG Migration to Groundwater PAH Polyaromatic hydrocarbon PCB Polychlorinated Biphenyls PID Photoionization Detector PPE Personal Protective Equipment QC Quality Control QEP Qualified Environmental Professional RCRA Resource Conservation and Recovery Act RPD Relative Percent Difference RRO Residual Range Organics SGS SGS North America, Inc.

TAH Total Aromatic Hydrocarbons TAqH Total Aqueous Hydrocarbons TCLP Toxicity Characteristic Leaching Procedure TC-EM JV Tanana Commercial-Environmental Management JV USS United States Survey UST Underground Storage Tank VOC Volatile Organic Compound

Job # 17855, December 2019 1

2019 Underground Storage Tank Removal and Groundwater Monitoring Report

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

Kotzebue, Alaska

This report outlines the 2019 underground storage tank (UST) system removal 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 June 12, 2019 Task Order EC-05 under the Professional Services Contract 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:

• demolition and removal of a UST system used by IHS, including the concrete fuel dispensing island, UST, and associated piping, including sampling and backfill;

• placement of soils generated during UST removal of contaminated soils into an existing Kikiktagruk Inupiat Corporation (KIC) landfarm site on Base Road; and

• groundwater monitoring and elevation survey of existing wells.

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 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 north along Second Avenue, near the intersection of Ocean Avenue.

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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 (1957 and 1958 only) 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 2019 field activities, the UST removal activities were conducted near the concrete dispenser island and UST location adjacent north of the FRF Building on Lot 5; and groundwater monitoring took place on each of the lots and Tract 4A.

The landfarm property where the contaminated soil was placed is owned by KIC. KIC will maintain and manage the landfarm while being treated. The location of the 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)

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

Job # 17855, December 2019 3 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. (Shannon & Wilson, 2010)

A UST of unknown volume and condition was identified along the north side of the FRF Building in 1989. The presumed storage use of the tank was for vehicle fueling and was discontinued sometime prior to 1969. When sampled in 1989, the tank contained approximately 2 ½ inches of what appeared to be waste lubricating oil, floating on water. (Shannon & Wilson, 1990) The concrete dispenser island associated with this UST was removed during the 2019 effort, and the dispenser was removed some time prior to 1979.

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 indicated contamination was 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 the decommissioning of the monitoring and recovery well and oil-recovery gallery. 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 non-functioning wells were decommissioned. The oil-recovery gallery was unable to be located but the sample collected from the vicinity exceeded diesel range organics (DRO) levels. (Shannon & Wilson, 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. (Shannon & Wilson, 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)

The FRF Building is a light commercial office building on a steel pile foundation. There is approximately 4 feet of clear air space below the building and no basement. The building’s population is approximately less than 70 adults; children are occasionally present. The hours of use are Monday through Friday from 8AM to 5PM.

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2.0 FIELD ACTIVITIES

The field activities were conducted in June and August 2019. Field activities included pre-excavation soil characterization sampling, landfarm construction, UST removal and sampling, waste characterization sampling, monitoring well elevation survey, and groundwater sampling.

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.

Field activities were conducted by TC-EM JV. Shayla Marshall served as the Qualified Environmental Professional (QEP) during the pre-excavation soil characterization and the August groundwater sampling activities; Larry Helgeson, PE served as the ADEC Certified UST Closure Worker; and Dale and Cynthia Erickson conducted the elevation survey of monitoring wells. KIC Construction, LLC constructed the landfarm and conducted the UST removal.

2.1 Work Plan Variances

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

• The flush wells were not marked with bright paint for easy identification in future events, per the work plan. Due to the proximity of many of the wells within areas of high foot traffic, it was agreed to not paint the wells to minimize attention and potential tampering of the wells. At the request of the ADEC, two of the wells on school property (Wells MW3 and MW9) were covered with fill so the well was flush with the ground surface to minimize tripping hazards.

• The soil generated during the UST removal activities were not segregated into separate stockpiles based on the photoionization detector (PID) readings or observations due to the shallow placement of the UST and limited volume of soil that was removed. All soils were placed directly into trucks to be placed in the landfarm.

2.2 Pre-Excavation Soil Characterization

On June 13, 2019, TC-EM JV conducted pre-excavation soil sampling in the area surrounding the UST dispenser island. The purpose of the sampling was to determine whether the soil concentrations exceeded Resource Conservation and Recovery Act (RCRA) maximum concentrations for the toxicity characteristic of total lead and are not able to be landfarmed.

Maniilaq Association provided a backhoe (Case 530D) and operator to advance the exploratory test pits. Based on the 2018 geophysical survey, the UST was presumed to be located on the north side of the dispenser island, between the island and the fence along KIC’s storage yard.

Since the intent of the field effort was not to remove the tank but sample the soil around the tank, one test pit was advanced on the south side of the concrete dispenser island and one test pit was advanced on the west side of the dispenser island (Photos 1 through 4).

Ambient field screening samples were collected during excavation of the test pits. Soil from both test pits contained a diesel odor with the strongest odors at the groundwater interface zone.

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Sheen was encountered in the groundwater at 5 feet below ground surface (bgs) in both test pits.

One analytical sample was collected from each test pit at the groundwater interface zone.

Each test pit was backfilled after soil samples were collected.

2.3 Landfarm Construction

Once sample results from the pre-excavation soil characterization indicated that the soils did not contain concentrations that exceeded RCRA maximum concentrations for the toxicity characteristic of total lead, the construction of the landfarm was authorized. KIC Construction began construction of the landfarm during the week of July 29, 2019.

The landfarm was constructed on an undeveloped area adjacent to KIC’s existing landfarm off of Base Road (Photo 5). Since the new cell was located on previously undeveloped land, baseline sampling was not required or conducted prior to construction.

The landfarm cell was constructed in accordance with the ADEC-approved work plan and was designed to accept up to 185 cubic yards of soil. A 20-mil bottom liner was placed on top of the ground surface; the liner was continuous with no seams. Approximately 6 inches of protective fill from the KIC Gravel Pit was placed on the top of the liner to serve as a protective layer and keep the liner in place (Photo 6). Lined berms were placed around the landfarm to contain leachate that might be generated during rainfall events. A sump was installed on the lowest corner of the landfarm cell to collect runoff, and a granulated activated carbon (GAC) filter was placed near the sump for leachate treatment (Photos 7 and 8).

KIC placed a silt fence around the cell including between soils generated from another project, and a construction fence around the KIC landspread/landfarm area (Photo 9). Because less soil was generated during the UST removal and the soils did not cover the entirety of the landfarm cell, silt fence was also placed around the perimeter of the contaminated soils to demarcate the contaminated soils from the clean protective material (Photo 10). A sign noting where the soil in each cell originated from and the date the soil was delivered to the cell was placed to demarcate the soil generated/treated from this project from other projects that will use the area for treatment (Photo 11).

After placement of the soils generated during UST removal activities, nutrients were added and tilled into the soils (Photo 12).

2.4 UST Removal and Sampling

The UST removal activities were conducted on August 5, 2019. The UST, concrete dispenser island, and associated piping were removed by KIC Construction with oversight by an ADEC-certified UST worker and ADEC QEP, Larry Helgeson, PE.

The ADEC forms that apply to UST closures were provided to the ADEC prior to and after field activities. The following forms were provided to the ADEC with copies of the forms and ADEC letters in response to the forms are provided in Appendix C:

Job # 17855, December 2019 6

• UST registration and certification form (Form 18-0500) was provided to the ADEC on July 29, 2019,

• Intent to Close (Form 18-504) was provided to the ADEC on July 29, 2019,

• Notice of Post Closure (Form 18-0505) was provided to the ADEC on September 3, 2019, and

• Site Assessment and Release Investigation (Form 18-0508) was provided to the ADEC on September 10, 2019.

2.4.1 Piping Removal

The concrete island was demolished exposing the abandoned piping connecting to the tank (Photo 13). The dispenser had been removed some time prior to 1979. The excavator was used to expose the subsurface soils on the east side of the island to try to find the tank. When removing the first lift the excavator encountered the vent pipe less than 6 inches below the surface (Photo 14). Using hand tools the top of the tank was exposed about one foot below the surface. The piping from the island to the tank was less than three feet in length (Photo 15). A field screening sample was collected from each end of the pipe; one below the dispenser and one at the tank. One analytical sample was collected of soils below the dispenser and beneath pipe fittings. The field screening of the vent pipe indicated there was no contamination in that area.

The location of the UST is shown on Figure 3, and screening and analytical sample locations are shown on Figure 4.

2.4.2 Tank Removal

After the top of the tank was exposed and the vent pipe removed, a stick was placed into the tank to determine how much fluid there was in the tank. The bottom foot of the stick came back coated with a thick black oil. This was unexpected since according to local knowledge and the tank registration the tank had been used to store gasoline. The excavation continued around two sides of the tank until it was free enough to be raised a few inches at one end so all the fluids inside would flow to the other side to be pumped out (Photo 16). The fluid was pumped out into three drums with the first two drums containing mainly water. The last drum had about 10 inches of mainly oil.

The atmosphere in the tank was periodically checked with a QRae II four gas meter for explosive vapors. It was consistently below 5% of the lower explosive limit (LEL). Just prior to removal the LEL was 0%.

The size of the tank was measured to be a 500-gallon tank (45 inches in diameter by 69 inches in length). It was easily lifted up with the excavator and placed in the bucket of the loader to be transported to the lined cell on the same lot for storage pending results of the testing of the tank contents (Photos 17 and 18, and 22).

The UST was later cut open and cleaned with Simple Green (Photo 23). Residual oil, sludge, and rinsate were placed in an open-top drum. The tank and piping were consolidated for transportation to the landfill (Photo 24).

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The ground-level surface area of the UST excavation was approximately 100 square feet.

2.4.3 Excavated Soil Characterization

Samples were collected from the UST excavation. After removal of the tank, groundwater (Photo 19) was observed at about 4.5 feet bgs, just above the base of the tank. Therefore, the screening and analytical samples representing the bottom were collected from the soil-groundwater interface as close to the tank centerline as possible (Photo 20).

No samples were taken from the one truck of spoils from the excavation. Due to the small size of the excavation and small quantity of soils (approximately 16 cubic yards) removed, the samples from the limits of the excavation were considered representative of the soil in the truck.

Since the presumed UST was within an area that is likely to be impacted from a larger area of diesel contamination from the former pipeline, the soil removal activities were limited to the material that was in direct contact with the UST and/or was generated from the removal of the

UST.

After completion of the UST removal and sampling activities, the concrete and piping were removed and the excavation was backfilled and compacted with clean material from the KIC Gravel Pit (Photo 26).

2.4.4 UST Contents Waste Characterization

Since what appeared to be waste oil was encountered in the UST, water and waste oil grab samples were collected for the purposes of waste characterization and to determine disposal options. The contents were containerized in overpacks (Photo 25) and a drum thief was used to collect analytical samples from the containerized waste.

2.4.5 UST Analytical Suite

The analytical samples were submitted to SGS North America, Inc. (SGS) of Anchorage, Alaska.

The sample suite was for an “used oil, or unknown” as listed in Table F of the Field Sampling Guide. All samples were analyzed for:

• gasoline range organics (GRO) by Alaska (AK) Method 101,

• DRO by AK102

• residual range organics (RRO) by AK103

• volatile organic compounds (VOCs) by Environmental Protection Agency (EPA) Method

8260C

• polychlorinated biphenyls (PCBs) by EPA 8082, and

• metals (arsenic, cadmium, chromium, mercury, and lead) by EPA 6020.

In addition, three of the samples (>20%) were analyzed for:

• polynuclear aromatic hydrocarbons (PAH) by EPA 8270D SIMS

Job # 17855, December 2019 8

2.5 Groundwater Monitoring Well Sampling and Survey

Groundwater sampling and elevation survey was conducted on the site’s ten monitoring wells between August 6 and 8, 2019. The locations of the monitoring wells are shown on Figure 5 and photographs of the site wells and groundwater sampling activities are included as Photos 27 through 36 in Appendix B.

2.5.1 Tidal Monitoring

Due to the proximity of the site from Kotzebue Sound, tidal monitoring was also conducted on August 6, 2019 with water levels measured at both high and low tides. The tidal variance on August 6, 2019 was minimal with 0.31 feet at low tide and 0.55 feet at high tide. The water levels in the wells were the similar between the high and low tide.

2.5.2 Groundwater Sampling and Well Conditions

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

Analytical samples were collected in nine of the ten wells. Due to the presence of product (approximately 0.5 inch), an analytical sample was not collected from Monitoring Well MW1 (Photo 28). A black, oily residue was observed in the tubing inside Monitoring Well MW5 (Photo 31), however product was not measured in the well. Instead, sheen was noted in the purgewater from Well MW5. A petroleum odor was noted in the purgewater from Wells MW3 through MW6.

Two four-inch PVC casings were observed in the vicinity of the site wells. One PVC stickup was observed next to Monitoring Well MW1, and the second PVC stickup was observed next to Monitoring Well MW6. Both appeared to have soil inside the annulus and did not have a protective monument (Photos 32 and 36).

A blockage was present in Monitoring Well MW6. The total well depth measured at 5.54 feet BTOC and neither a pump nor water level meter were able to extend beyond. Well logs indicated that the well was screened between 3 feet 10 inches and 13 feet. Since the water appeared to be located within the screened interval, the well was sampled.

2.5.3 Groundwater Sampling Analytical Suite

The groundwater analytical samples were submitted to SGS of Anchorage, Alaska. All samples were analyzed for:

• GRO by AK 101

• DRO by AK102

• RRO by AK103

• VOCs by EPA 8260C

• total aromatic hydrocarbons (TAH) by EPA 624

• total aqueous hydrocarbons (TAqH) by EPA 625M.

In addition, one of the samples (10 percent) was analyzed for:

• PAH by EPA 8270D SIMS

• PCBs by EPA 8082

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2.5.4 Level Loop Survey

A level loop survey was also conducted of the site’s wells to determine elevations for groundwater flow direction and gradient development. After completion of the survey, the flush-mounted wells were secured.

3.0 SAMPLING RESULTS

The samples were submitted to SGS laboratory in Anchorage, Alaska for sample analysis. The soil, waste contents, and groundwater results are described in further detail below.

3.1 Subsurface Conditions

Soils at the site consisted of primarily brown sandy to silty gravel. All soils had relatively low organic content. Groundwater was encountered between 4.5 and 5 feet below ground surface (bgs) during the field activities. Petroleum odors and sheen were encountered in the soils and groundwater from the exploratory test pit and UST excavation.

3.2 Pre-Excavation Soil Characterization Results

Soil samples were collected on June 13, 2019 from two test pits advanced in the vicinity of the UST. The purpose of the sampling was to determine if the soils exceed hazardous waste characteristics. Table 1 summarizes the analytical results and comparison to applicable regulatory standards. The laboratory report is provided in Appendix E.

Table 1 – Summary of Pre-Excavation Soil Characterization Analytical Results

Parameter Analysis Regulatory

Level* Sample ID

TP1 TP2

Sample Depth – ft - - 5 5 Field Headspace Result – ppmv PID 3000 - 356 91.1 Total Lead – mg/Kg SW6020A 400 22.5 9.91

TCLP Lead – mg/L SW6020A TCLP 5.0 0.100 U 0.100 U

TCLP BTEX

TCLP Benzene – mg/L SW8260C TCLP 0.5 0.0200 U 0.0200 U TCLP Toluene – mg/L SW8260C TCLP - 0.0500 U 0.0500 U TCLP Ethylbenzene – mg/L SW8260C TCLP - 0.0500 U 0.0500 U TCLP Xylenes (total) – mg/L SW8260C TCLP - 0.150 U 0.150 U

Notes:

22.5 Bold denotes detectable concentration reported in the project sample

U Analyte not detected above detection limit mg/Kg Milligrams per Kilogram mg/L Milligrams per Liter

* Table B1 or B2 Method Two Migration to Groundwater (MTG) (18 AAC 75) (October 27, 2018) or Table 1 Maximum Concentration of Contaminants for the Toxicity Characteristic (40

CFR 261.24)

- Not sampled or not applicable

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3.3 UST Excavation Soil Characterization Results

Thirteen locations were screened during the UST removal activities on August 5, 2019 using headspace methods with the results presented in Table 2.

Table 2 – Summary of UST Removal Headspace Results

Field Sample ID Date

PID

Headspace

Result (ppmv)

Depth

(ft) Location

Lab Sample ID and Notes

Disp -01 8/5/2019 2.2 1 Dispenser UST DIS-01 & (-02) FL-02 8/5/2019 2.0 1 Fuel Line

Vent-03 8/5/2019 3.2 1 Vent Line SW-04 8/5/2019 224 3 Sidewall - North SW-05 8/5/2019 265 3 Sidewall - Northwest SW-06 8/5/2019 214 3 Sidewall -West at end of tank SW-07 8/5/2019 311 3 Sidewall -Southwest UST SW-05 SW-08 8/5/2019 254 3 Sidewall - Northeast SW-09 8/5/2019 66 3 Sidewall -South SW-10 8/5/2019 285 3 Sidewall - East at end of tank Bot-11 8/5/2019 485 3 Bottom of Tank - East UST BOT-04 Bot-12 8/5/2019 440 3 Bottom of Tank - Center UST BOT-03 Bot-13 8/5/2019 443 3 Bottom of Tank - West

Notes:

311 Indicates reading used to select laboratory sample locations

Based on headspace results and per the March 2017 Underground Storage Tank Procedures Manual and UST Regulations (18 AAC 78, July 2017) a total of four analytical soil samples, plus one duplicate, were collected on August 5, 2019 and analyzed. Locations of screening and analytical samples are shown on Figure 4. Analytical results are shown in Table 3. The laboratory report is provided in Appendix D.

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Table 3 – Summary of UST Removal Detectable Analytical Results

Sample ID and Location of Sample

Analyte Analysis Unit

ADEC Cleanup Level* Dispenser Bottom of Excavation Sidewall Trip

Blank

MTG HH/MAC UST DIS-

UST DIS-

02~ UST BOT-03 UST BOT-04 UST SW-

05 UST TB

Sample Depth - ft - - 1 1 4.5 4.5 3 -

Field Headspace MiniRae PID ppmv - - 2.2 2.2 440 485 311 -

Gasoline Range Organics AK101 mg/Kg 300 1,400 2.61 3.31 327 109 46.0 2.52 U Diesel Range Organics AK102/103 mg/Kg 250 12,500 26.8 26.5 22500 16200 8470 - Residual Range Organics AK102/103 mg/Kg 11,000 22,000 56.9 55.0 379 283 193 - Polyaromatic Hydrocarbons (PAH)

1-Methylnaphthalene 8270D SIM ug/Kg 410 68,000 26.0 U 25.8 U - 46100 - - 2-Methylnaphthalene 8270D SIM ug/Kg 1,300 310,000 26.0 U 25.8 U - 14900 - - Acenaphthene 8270D SIM ug/Kg 37,000 4,600,000 26.0 U 25.8 U - 1080 - - Fluorene 8270D SIM ug/Kg 36,000 3,100,000 26.0 U 25.8 U - 5430 - - Phenanthrene 8270D SIM ug/Kg 39,000 2,300,000 26.0 U 25.8 U - 6690 - - Pyrene 8270D SIM ug/Kg 87,000 2,300,000 26.0 U 25.8 U - 576 - - Other PAHs 8270D SIM ug/Kg varies varies ND ND ND ND ND ND

Total UST Metals Arsenic SW6020A mg/Kg 0.2 8.8 4.48 3.96 4.78 6.27 4.83 - Cadmium SW6020A mg/Kg 9.1 92 0.195 U 0.192 U 0.206 U 0.209 U 0.212 U - Chromium SW6020A mg/Kg - - 17.4 7.59 7.52 15.7 14.9 - Lead SW6020A mg/Kg - 400 30.6 25.6 37.4 20.9 59.1 - Mercury SW6020A mg/Kg 0.36 3.1 0.0781 U 0.0769 U 0.0822 U 0.0837 U 0.0847 U -

Polychlorinated Biphenyls (PCB) SW8082A ug/Kg 1 - ND ND ND ND ND - Volatile Organic Compounds (VOC)

1,2-Dibromoethane SW8260C ug/Kg 0.24 420 2.54 0.769 U 10.3 U 7.10 U 0.864 U 1.01 U 1,2-Dichloroethane SW8260C ug/Kg 5.5 5,500 1.45 U 1.54 U 20.6 U 14.2 U 2.30 2.02 U 1,3,5-Trimethylbenzene SW8260C ug/Kg 660 37,000 18.1 U 19.2 U 8340 5320 44.9 25.2 U Naphthalene SW8260C ug/Kg 38 29,000 18.1 U 19.2 U 4770 3270 65.6 25.2 U Toluene SW8260C ug/Kg 6,700 200,000 25.3 25.1 257 U 177 U 42.8 25.2 U Other VOCs SW8260C ug/Kg varies varies ND ND ND ND ND ND

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3.4 UST Waste Characterization Results

Samples were collected from the UST waste contents on August 5, 2019 for disposal characterization purposes. Drum A comprised of 50 gallons of water with sheen. Drum C contained 8 inches of oil and 1.5 inches of water. Analytical results are shown in Table 4. The laboratory report is provided in Appendix D.

Table 4 – Summary of UST Waste Contents Analytical Results

Parameter Analysis Regulatory

Level* Sample ID

Drum A Drum C Ignitability Seta Flash – °F SW1020B 100 °F min - GT200

Total Metals Arsenic – mg/kg SW6020A 5 - 0.989 U Cadmium – mg/kg SW6020A 2 - 0.578 Chromium – mg/kg SW6020A 10 - 4.84 Lead – mg/kg SW6020A 100 - 2,290

Total Lead – ug/L SW6020A - 11,800 - Polychlorinated Biphenyls (PCBs) SW6020A TCLP 50 - ND Total Halogens – mg/kg SW9056A 4,000 - 396 U Volatile Organic Compounds (VOCs)

1,2,4-Trimethylbenzene – mg/kg SW8260C - - 3,610 1,3,5-Trimethylbenzene – mg/kg SW8260C - - 991 4-Isopropyltoluene – mg/kg SW8260C - - 154 Ethylbenzene – mg/kg SW8260C - - 841 Isopropylbenzene (Cumene) – mg/kg SW8260C - - 110 Naphthalene – mg/kg SW8260C - - 798 Toluene – mg/kg SW8260C - - 220 Xylenes – mg/kg SW8260C - - 4,770 n-Propylbenzene – mg/kg SW8260C - - 378 Sec-Butylbenzene – mg/kg SW8260C - - 58.9 Other VOCs SW8260C - - ND

* 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)

327 Above ADEC MTG Cleanup Level 22500 Above ADEC HH/MAC Cleanup Level

~ Duplicate of proceeding sample bgs Below ground surface mg/kg Milligrams per kilogram

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

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

30.6 Detectable concentration reported in the project sample

- Not analyzed

ND Not detected

Job # 17855, December 2019 13

Notes:

2,290 Bold denotes detectable concentration reported in the project sample

0.989 U Analyte not detected above detection limit

mg/Kg Milligrams per Kilogram ug/L Micrograms per Liter

* Table 1 Used Oil Not Exceeding Any Allowable Level Shown Below is Not Subject to this Part When Burned for Energy Recovery (40 CFR 279.11)

- Not sampled or not applicable

3.5 Groundwater Monitoring Results

Water level measurements were collected from the site wells on August 6, 2019 during high and low tides. In addition, a level loop survey was conducted between August 7 and 9, 2019 to determine water level elevation. A summary of the water level elevations, results from the tidal monitoring depths to water, and notable observations from the August 2019 groundwater monitoring event is provided in Table 5.

Table 5 – Groundwater Levels and Elevations

TOC

Elevation

(ft)

Total Well Depth (ft

BTOC)

Depth to Water (ft BTOC) Water Level Elevation

(ft)

Well Date Low Tide

High Tide Difference Notes

MW1 8/6/2019 8.62 7.48 2.42 2.42 0.00 6.20 0.5-inch of product

MW2 8/6/2019 10.05 7.90 3.51 3.52 0.01 6.54

MW3 8/6/2019 9.54 9.47 3.36 3.36 0.00 6.18 Strong POL odor MW4 8/6/2019 9.17 12.42 3.15 3.15 0.00 6.02 Slight POL odor MW5 8/6/2019 9.27 8.00 3.95 3.95 0.00 5.32 Sheen and strong

POL odor MW6 8/6/2019 9.33 5.54 * * NA NA Blockage; strong POL odor

MW7 8/6/2019 10.50 12.95 4.32 4.32 0.00 6.18

MW8 8/6/2019 10.06 14.20 3.81 3.81 0.00 6.25

MW9 8/6/2019 8.42 12.35 2.50 2.5 0.00 5.92

MW10 8/6/2019 9.28 12.70 3.31 3.31 0.00 5.97

Notes:

* Well not located during depth to water measurements. Depth to water during sampling was at 5.54 feet BTOC ft feet

BTOC Below Top of Casing POL Petroleum Oil and Lubricants

As shown on Figure 5, the groundwater direction appears to be to the north-northwest.

Samples were collected from the nine of the ten groundwater monitoring wells on August 6 and 7, 2019. An analytical sample was not collected from Monitoring Well MW1 due to the presence of measurable product in the well. Groundwater analytical results are shown in Table

6. The laboratory report is provided in Appendix D.

Job # 17855, December 2019 14

Table 6 – Summary of Detectable Groundwater Analytical Results

Analyte Analysis Unit

ADEC

Cleanup Level* Sample ID**

MW2 MW3 MW4 MW5 MW6 MW7 MW8 MW9 MW29~ MW10

GRO AK101 mg/L 2.2 0.100 U 0.100 U 0.100 U 0.125 0.322 0.100 U 0.100 U 0.256 0.263 0.100 U DRO AK102 mg/L 1.5 0.588 U 0.630 U 3.27 3.89 J- 6.06 1.41 0.610 U 12.8 9.63 24.1 RRO AK103 mg/L 1.1 0.490 U 0.525 U 0.872 0.663 J- 0.557 1.20 0.508 U 1.36 0.834 3.59 TAH EPA 602/624 ug/L 10 ND ND ND 15.3 37.4 ND 1.12 30.57 30.5 15.94 TAqH EPA 625M ug/L 15 ND ND ND 17.7 56.8 ND ND 2.22 3.37 2.60 PCBs SW8082A ug/L 0.44 - - - - - - - - - ND VOCs 1,2,4-Trimethylbenzene SW8260C ug/L 56 1.00 U 1.00 U 1.00 U 39.4 63.1 1.00 U 1.00 U 58.4 56.5 8.54 1,3,5-Trimethylbenzene SW8260C ug/L 30 1.00 U 1.00 U 4.60 19.7 43.4 1.00 U 1.00 U 45.2 44.9 3.68 2-Butanone (MEK) SW8260C ug/L 5600 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 16.4 14.4 10.0 U 4-Isopropyltoluene SW8260C ug/L - 1.00 U 1.00 U 1.00 U 10.7 24.8 1.00 U 1.00 U 21.2 21.8 3.22 Benzene SW8260C ug/L 4.6 0.400 U 0.400 U 0.400 U 0.560 0.400 U 0.400 U 1.12 12.0 12.0 0.830 Chloroform SW8260C ug/L 2.2 15.7 1.00 U 1.00 U 1.00 U 1.00 U 1.00 U 4.84 1.00 U 1.00 U 1.00 U Dichlorodifluoromethane SW8260C ug/L 200 7.16 14.6 1.19 34.4 5.84 4.35 6.41 4.68 4.60 1.00 U Ethylbenzene SW8260C ug/L 15 1.00 U 1.00 U 1.00 U 3.94 12.1 1.00 U 1.00 U 7.87 7.83 7.44 Cumene SW8260C ug/L 450 1.00 U 1.00 U 1.00 U 3.04 10.9 1.00 U 1.00 U 7.37 7.64 1.84 Methyl-t-butyl ether SW8260C ug/L 140 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U 10.0 U Methylene chloride SW8260C ug/L 110 5.00 U 5.00 U 5.00 U 5.00 U 5.00 U 5.00 U 5.00 U 5.00 U 5.00 U 5.00 U Naphthalene SW8260C ug/L 1.7 1.00 U 9.71 2.58 57.0 157 1.00 U 1.00 U 102 105 26.6 Trichlorofluoromethane SW8260C ug/L 5200 57.0 54.5 3.70 61.2 6.92 1.00 U 12.0 7.47 6.99 1.00 U Xylenes (total) SW8260C ug/L 190 3.00 U 3.00 U 3.00 U 10.8 25.3 3.00 U 3.00 U 10.7 10.7 7.67 n-Butylbenzene SW8260C ug/L 1000 1.00 U 1.00 U 1.00 U 1.60 4.24 1.00 U 1.00 U 10.2 5.29 1.00 U n-Propylbenzene SW8260C ug/L 660 1.00 U 1.00 U 1.00 U 3.19 13.4 1.00 U 1.00 U 9.66 9.78 1.88 sec-Butylbenzene SW8260C ug/L 2000 1.00 U 1.00 U 1.00 U 3.02 7.66 1.00 U 1.00 U 6.82 7.08 1.10 tert-Butylbenzene SW8260C ug/L 690 1.00 U 1.00 U 1.00 U 1.00 U 1.00 U 1.00 U 1.00 U 1.17 1.17 1.00 U Other VOCs SW8260C ug/L varies ND ND ND ND ND ND ND ND ND ND

PAHs 8270D SIM ug/L Acenaphthene 8270D SIM ug/L 530 - - - - - - - - - 1.95 Naphthalene 8270D SIM ug/L 1.7 - - - - - - - - - 1.85 Other PAHs 8270D SIM ug/L 1.7 - - - - - - - - - ND

Job # 17855, December 2019 15

4.0 DISCUSSION

A discussion of the results from the June 2019 pre-excavation sampling efforts, August 5, 2019 UST removal and waste characterization activities, and August 6 and 7, 2019 groundwater sampling efforts are described in detail below.

4.1 UST Excavation and Waste Characterization Discussion

Prior to UST excavation activities, exploratory test pits were advanced to determine if concentrations are less than hazardous waste characteristics and are able to be locally landfarmed. Because the UST was presumed to have contained gasoline, the soil was tested for total and toxicity characteristic leaching procedure (TCLP) lead, and TCLP BTEX. With the exception of total lead, the analytical sample results were non-detect. In addition, the total lead concentrations were well below the ADEC cleanup level. Based on the results from the June 13, 2019 exploratory test pit soil sampling, the soils were deemed suitable for landfarming.

On August 5, 2019, the 500-gallon UST was removed. Thirteen locations were screened using headspace methods, and a total of four analytical soil samples, plus one duplicate, were collected and analyzed from the project site.

Based on previous investigation west of the dispenser island, low level of contamination was expected to be encountered beginning around 1 foot bgs. Because of this, it was not worth trying to segregate clean from contaminated soils. All excavated soils were assumed to be contaminated and loaded directly into a truck to be taken to the land farm for treatment. The readings with the PID of ambient soil vapors started to noticeably increase as the excavation got below 1 foot with the highest readings just above the groundwater which was encountered a little over 4.5 feet bgs. A slight sheen was visible on the water. It is worthy to note that Kotzebue had received heavy rains in the days just before we arrived on site. In some places in town, water still flooded over roads.

DRO was the main type of contaminant found in the soils at the site with levels of 22,500 and 16,200 milligrams per kilogram (mg/kg) near the bottom of the tank which is above the maximum allowable concentration listed in Table 2B of 18 Alaska Administrative Code (AAC)

75. These samples also had PAHs, VOCs, and arsenic elevated above the migration to

* Table C Groundwater Human Health Cleanup Level (18 AAC 75, October 27, 2018) or Water Quality Standards Table, applicable to TAH and TAqH only (18 AAC 70, April 6, 2018)

** Sample Number proceeded by TC-EM JV Job Number, 17855, on COC

3.27 Above ADEC Cleanup Level or Water Quality Standard

~ Duplicate of proceeding sample mg/L Milligrams per liter ug/L Micrograms per liter

1.00 U Concentration not detected Above the LOQ

7.16 Detectable concentration reported in the project sample

- Not analyzed

J- Concentration biased low due to analysis past hold time

Job # 17855, December 2019 16 groundwater (MTG) standard listed in Table B1. While the PAH and VOC contamination is likely from the historical petroleum spill, the arsenic level 6.27 mg/kg is likely typical of background levels in the area.

The sidewall sample (UST SW-05) just 1.5 feet higher had DRO concentration of 8,470 mg/kg, or about half of the level at the bottom of the tank. Based on the consistent field screening results from the sidewall samples this level of contamination should be expected on all sides of the excavation just 3 feet bgs.

Based on field screening and analytical sample results, there was no evidence of gasoline or used oil contamination found in the soils around the tank. The contamination found is more consistent with the historical fuel oil that has contaminated the general area. In addition, the chromatograms of the soil samples collected from the UST excavation are consistent with DRO contamination. Copies of the chromatograms and SGS fuels library are included in Appendix E.

4.2 UST Waste Characterization Discussion

The contents of the tank met all the 40 Code of Federal Regulations (CFR) 279.11 used oil specifications, except for elevated lead. Therefore, the contents were classified as off spec used oil and shipped to NRC Alaska for treatment and disposal.

4.3 Groundwater Monitoring Discussion

Tidal monitoring was conducted on August 6, 2019 and analytical samples were collected from nine of the ten site wells between August 6 and 7, 2019. A sample was not collected from Monitoring Well MW1 due to the presence of measurable product.

While tidal monitoring did not indicate a difference between high and low tides on August 6, 2019, there was not a large tidal change on that date. Due to the proximity of the site to Kotzebue Sound and the absence of TAH and TAqH analyses from previous sampling efforts, the wells were tested for surface water analytes TAH and TAqH. Concentrations exceeding the TAH water quality standard of 15 micrograms per liter (ug/L) were reported in the samples from Monitoring Wells MW5, MW6, MW9, and MW10. These wells are all located along the pipeline corridor. Concentrations exceeding the TAqH water quality standard of 10 ug/L were reported in the samples from Monitoring Wells MW5 and MW6. Monitoring Wells MW5 and MW6 are located adjacent to the school on Tract 4A and near the former pipeline.

Groundwater samples were also analyzed for GRO, DRO, RRO, and VOCs with select samples also analyzed for PAH and PCBs. Concentrations of DRO remain above ADEC Table C cleanup levels in five of the ten wells, noting Well MW1 previously contained concentrations of DRO greater than cleanup level but was not sampled during this event. The highest concentration was reported in the sample from Monitoring Well MW10. RRO remains above the cleanup level in Wells MW9 and MW10, and now contains RRO greater than the cleanup level in for the first time in Well MW7. Benzene still exceeds the cleanup level in Monitoring Well MW9, and previously elevated levels in Monitoring Well MW10 no longer exceed the cleanup level. A summary of the historical groundwater sample results is provided in Table 7.

Job # 17855, December 2019 17

Concentrations of other VOCs were also reported above ADEC Table C cleanup levels in the site’s monitoring wells. Naphthalene was reported at concentrations greater than the 1.7 ug/L cleanup level in the samples from six of the site’s wells with reported concentrations ranging between 2.58 ug/L to 157 mg/L. The highest concentrations were reported in the samples from Well MW6 and MW9. Naphthalene was also analyzed under the PAH analytical suite for the sample from Well MW10 and contained a concentration of 1.85 ug/L.1,2,4-Trimethylbenzene and 1,3,5-trimethylbenzene were also reported at concentrations greater than the 56 ug/L cleanup level in Wells MW6 and MW9 (the primary and duplicate sample) with concentrations ranging between 56.5 and 63.1 ug/L. The only other VOC reported at concentrations greater than the ADEC Table C cleanup level of 2.2 ug/L is chloroform in Wells MW2 (15.7 ug/L) and MW8 (4.84 ug/L).

Table 7 – Historical Groundwater Sampling Results

GRO DRO RRO Benzene Toluene Ethylbenzene Total Xylenes Well 2.2 mg/L 1.5 mg/L 1.1 mg/L 0.005 mg/L 1.0 mg/L 0.7 mg/L 10.0 mg/L

MW1~ 8/25/2014 0.878 31.4 3.37 0.00134 0.00112 0.0333 0.118

MW1~ 7/15/2015 2.01 20.7 1.81 0.0009 0.00114 0.0223 0.118

MW1 8/5/2019 Not sampled - Measurable Product

MW2 8/25/2014 ND ND 0.248 J ND ND ND ND

MW2 7/13/2015 1.40 ND ND ND ND ND ND

MW2 8/7/2019 ND ND ND ND ND ND ND

MW3 8/26/2014 ND ND ND ND ND ND ND

MW3 7/13/2015 Not sampled - Frozen

MW3 8/7/2019 ND ND ND ND ND ND ND

MW4 8/26/2014 0.136 3.53 0.461 J ND 0.00039 J 0.00032 J 0.00170 J

MW4 7/14/2015 0.102 1.40 0.137 J ND ND ND ND

MW4 8/7/2019 ND 3.27 0.872 ND ND ND ND

MW5 8/25/2014 0.188 5.44 1.0 ND 0.410 J 0.00304 0.0107

MW5 7/14/2015 Not sampled - Frozen

MW5 8/7/2019 0.125 3.89 0.663 0.000560 ND 0.00394 0.0108

MW6 8/26/2014 0.373 4.84 0.757 ND ND 0.00824 0.0189

MW6 7/14/2015 Not sampled - Frozen

MW6 8/7/2019 0.322 6.06 0.557 ND ND 0.0121 0.0253

MW7 8/27/2014 0.0389 J 1.19 0.767 ND 0.00032 J ND ND

MW7 7/13/2015 0.0313 J 1.0 0.352 J ND ND ND ND

MW7 8/6/2019 ND 1.41 1.20 ND ND ND ND

MW8 8/26/2014 ND 0.2 J 0.298 J ND ND ND ND

MW8 7/13/2015 ND 0.35 J 0.276 J ND ND ND ND

MW8 8/6/2019 ND ND ND 0.00112 ND ND ND

Job # 17855, December 2019 18

MW9 8/27/2014 0.488 9.35 1.61 0.00605 0.00076 J 0.00475 0.0283

MW9 7/15/2015 0.634 9.02 1.27 0.00343 0.00056 J 0.00665 0.0365

MW9~ 8/6/2019 0.263 12.8 1.36 0.0120 ND 0.00787 0.0107

MW10 8/27/2014 0.843 J 14.8 1.95 0.0568 0.0166 0.0425 0.147

MW10 7/13/2015 0.543 11.0 1.63 0.0343 0.00197 0.0375 0.088

MW10 8/6/2019 ND 24.1 3.59 0.000830 ND 0.00744 0.00767

5.0 QUALITY CONTROL REVIEW

The ADEC Laboratory Data Review Checklist was completed for the SGS reports. The laboratory reports and checklists are included in Appendix D. The following is a summary of the QC issues affecting data quality or usability.

5.1 SGS Report 1193069 Pre-Excavation Soil Characterization Samples No quality control (QC) issues affecting data quality or usability were noted.

5.2 SGS Report 1194483 UST Waste Characterization Samples

No QC issues affecting data quality or usability were noted.

5.3 SGS Report 1194509 Groundwater Samples

The following QC issues and the effect on data quality or usability were noted:

• Several VOA vials contained bubbles greater than 6 millimeters (mm). These included vials from MW2, MW3, MW4, MW9, and MW10. The lab proceeded with limited volume for the analyses. As only two VOA vials are required for each analysis with a third collected for extra volume, and two vials were received without bubbles greater than 6 mm, the data should not be affected.

• The DRO/RRO sample from Well MW5 was analyzed past the 14 day hold time due to laboratory error. The sample results are flagged as biased low in Table 6.

• The LOQ for 1,2,3-trichloropropane exceeded the cleanup level in each of the water samples and trip blank. Based on the detected concentrations at the site and contaminants of concerns, 1,2,3-trichloropropane is not anticipated to present at the site. Therefore, the data is considered usable.

• The AK101 surrogate, 4-bromofluorobenzene, recovery for Sample MW6 was reported at 152 percent with a data quality objective (DQO) of 150 percent. The project sample

* Table C Groundwater Human Health Cleanup Level (18 AAC 75, October 27, 2018)

31.4 Above ADEC Table C Cleanup Level

~ Duplicate sample collected; higher value between the primary and duplicate sample reported mg/kg Milligrams per kilogram

2.01 Detectable concentration reported in the project sample

Job # 17855, December 2019 19 results are well below the cleanup level, so the data is considered usable for the project purpose.

• The primary (MW9) and duplicate (MW29) samples relative percent difference (RPD) exceeded the DQO of 30 percent for RRO, acenaphthene, fluorene, phenanthrene, and n-butylbenzene. With the exception of RRO, each of the primary and duplicate sample concentrations were below the cleanup level so the data is considered usable and representative of the site conditions. The primary sample for RRO exceeds the cleanup level, but the duplicate sample does not. The higher of the two samples will be reported for management decision making purposes.

5.4 SGS Report 1194525 UST Excavation Soil Samples

The following QC issues and the effect on data quality or usability were noted:

• The AK101 surrogate, 4-bromofluorobenzene, recovery for Samples UST BOT-03, UST BOT-04, and UST SW-05; and the DRO surrogate for UST BOT-03 were greater than the with a DQO of 150 percent. The sample concentrations from UST BOT-03 were well above cleanup levels for the analytes, therefore the sample results are considered usable.

While the GRO concentrations for UST BOT-04 and UST SW-05 may be biased high due to surrogate failures, the project sample concentrations were a third or more less than the cleanup level. As a result, the sample results are considered usable.

• The LOQs for various VOCs exceeded the cleanup level in one or more samples. The elevated LOQs were primarily associated with high levels of contamination in the samples and a result of matrix interference. Therefore, the data is considered usable.

• The primary (UST DIS-01) and duplicate (UST DIS-02) samples RPD exceeded the DQO of 30 percent for chromium. The chromium results from both samples were below the cleanup level so the data is considered usable and representative of the site conditions.

6.0 INVESTIGATIVE DERIVED WASTE MANAGEMENT

Investigation…