24-002-02R3_BGES_Report_Kotzebue_AK_BIA_0001.pdf

Anchorage Seattle 24-002-02R3

FORMER IHS/BIA HOSPITAL-SCHOOL PIPELINE RELEASE

KOTZEBUE, ALASKA

ADEC CONTAMINATED SITES DATABASE FILE NUMBER 410.38.025

HAZARD ID 25558

2024 & 2025 SOIL DELINEATION AND GROUNDWATER MONITORING REPORT

FEBRUARY 2026

Submitted to: Peter Dunlevy

Bureau of Indian Affairs Pacific Region Office 2800 Cottage Way, W2820 Sacramento, California 95825

Submitted by: BGES, INC.

1042 East 6th Avenue Anchorage, Alaska 99501

(907) 644-2900 www.BGESINC.com

Former IHS/BIA Hospital School Pipeline Release BGES, Inc.

Kotzebue, Alaska 2024 & 2025 Groundwater Monitoring Report

Page i 24-002-02R3

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 BACKGROUND

3.0 FIELD ACTIVITIES

3.1 Work Plan Deviations

3.2 Soil Delineation

3.3 2024 Groundwater Monitoring

3.4 Installation of Replacement Monitoring Wells

3.5 2025 Groundwater Monitoring

3.6 Disposal of Investigation Derived Waste

4.0 EVALUATION OF LABORATORY DATA

4.1 2024 Groundwater Samples

4.2 2025 Groundwater Samples

4.3 Waste Characterization Soil Sample

5.0 LABORATORY DATA QUALITY REVIEW

5.1 Eurofins Spokane Report 590-27265-1 (2024 Groundwater Samples)

5.2 Eurofins Spokane Report 590-33069-1 (2025 Groundwater Samples)

6.0 CONCEPTUAL SITE MODEL

7.0 CONCLUSIONS AND RECOMMENDATIONS

8.0 EXCLUSIONS AND CONSIDERATIONS

FIGURES (Located at End of Report)

Figure 1 Property Vicinity Map

Figure 2 2024 & 2025 Groundwater Monitoring Well Results

Figure 3 Attempted Soil Boring Locations

TABLES (Located at End of Report)

Table 1 Monitoring Well Data

Table 2 Groundwater Sample Analytical Results

Table 3 Waste Characterization Sample Analytical Results

APPENDICES

Appendix A Field Notes, Soil Boring Logs, Groundwater Monitoring Logs, and Well Completion Logs

Appendix B Site Photographs

Appendix C Laboratory Analytical Data

Appendix D Laboratory Data Review Checklists

Appendix E Soil Disposal Documentation

Appendix F Conceptual Site Model

2024 & 2025 Groundwater Monitoring Report

Page ii 24-002-02R3

ACRONYMS

AAC - Alaska Administrative Code ADEC - Alaska Department of Environmental Conservation AK - Alaska Method bg - Below Grade BGES - Braunstein Geological and Environmental Services BIA - Bureau of Indian Affairs CCV - Continuing Calibration Verification DRO - Diesel Range Organics EPA - Environmental Protection Agency GAC - Granular Activated Carbon GRO - Gasoline Range Organics HDPE - High-Density Polyethylene IHS - Indian Health Service J - Estimated Quantity LCS - Laboratory Control Sample MDL - Method Detection Limit µg/L - Micrograms per liter mg/Kg - Milligrams per kilogram mL/min - Milliliters per minute ORP - Oxidation Reduction Potential PAHs - Polynuclear Aromatic Hydrocarbons PCBs - Polychlorinated Biphenyls PVC - Polyvinyl Chloride QC - Quality Control QEP - Qualified Environmental Professional RCRA - Resource Conservation and Recovery Act RL - Reporting Limit RPD - Relative Percent Difference RRO - Residual Range Organics SIM - Selected Ion Monitoring VOCs - Volatile Organic Compounds

2024 & 2025 Groundwater Monitoring Report

Page 1 of 17 24-002-02R3

1.0 INTRODUCTION

BGES, Inc. (BGES) was retained by Peter Dunlevy of the Bureau of Indian Affairs (BIA), to conduct soil delineation and groundwater monitoring activities associated with the former Indian Health Service (IHS)

/ BIA Hospital pipeline release in Kotzebue, Alaska; hereafter referred to as the subject property (Figure

1). The purpose of these activities was to evaluate the current groundwater conditions in the vicinity of the subject property.

The field work for the groundwater monitoring activities was performed on September 24 through 26, 2024, November 13, 2024, September 4 through 6, 2025, and September 8, 2025 in general accordance with the work plan prepared by BGES, dated August 15, 2024, and approved by Kelly Walker, Alaska

Department of Environmental Conservation (ADEC) Project Manager, on August 16, 2024; and the Work

Plan Addendum #1, dated November 5, 2024 and approved by Ms. Walker on November 12, 2024. Work plan deviations are enumerated in Section 3.1, below.

2.0 BACKGROUND

The subject property is listed in the ADEC Contaminated Sites database, under file number 410.38.025, and contains four parcels of land:

Lot 3 – former BIA school and small structures, once part of the hospital; currently residential

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

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

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

Heating fuel was historically provided to former IHS/BIA facilities, including a school and a hospital on the subject property, through a buried pipeline that has since been abandoned in place. In 1980, fuel was observed to be seeping into the basement of the school and it was estimated that 100,000 to 200,000 gallons of heating fuel had leaked from the pipeline since the 1950s. Soil, groundwater, and soil vapor sampling have been performed throughout the impacted area since 2014. As detailed in the 2021, 2020

Site Characterization, Limited Removal Action, and Groundwater Monitoring report prepared by Tanana

Commercial Company/Environmental Management LLC JV, 16 soil borings were advanced and 10 monitoring wells were installed during 2020. Four of these borings, located within Lots 4 and 5 along the former path of the pipeline and in the footprint of the former school building, exhibited contaminant

2024 & 2025 Groundwater Monitoring Report

Page 2 of 17 24-002-02R3 concentrations that exceeded the applicable ADEC Human Health Criterion for diesel range organics

(DRO) of 10,250 milligrams per kilogram (mg/Kg). A limited excavation of contaminated soil was subsequently performed to the northwest of the existing structure on Lot 4. The excavation was advanced to a depth of approximately 8 feet below grade (bg), whereafter permafrost, forming an impermeable barrier to the vertical migration of contaminants, was encountered. A total of approximately 200 cubic yards of contaminated soils were removed and placed in a land-farm for remediation. Confirmation samples were collected following the completion of excavation activities, and one sample from the northwest excavation sidewall exhibited concentrations of contaminants in exceedance of applicable

Human Health cleanup criteria.

A 2022 investigation (KUNA Engineering, 2023) included advancement of 16 additional soil borings and completion of 6 additional monitoring wells. Soils within two of those borings (one along the former pipeline near its eastern extent and another located near a residence to the west of the former school building) exhibited concentrations of contaminants exceeding applicable Human Health cleanup criteria.

An unknown quantity of contaminated soil remains on Lots 4 and 5 to the north of the previous excavation and in the vicinity of these borings. No contaminants were observed on Lot 3 in exceedance of applicable

Human Health cleanup criteria, and it was determined that this lot will not undergo additional remediation until human health concerns on the remaining lots have been addressed. Free product has been detected in at least two of the sixteen monitoring wells. Gasoline range organics (GRO), DRO, residual range organics (RRO), volatile organic compounds (VOCs), and polynuclear aromatic hydrocarbons (PAHs) have been detected in several monitoring wells at concentrations exceeding ADEC cleanup criteria.

BGES’ Site Delineation & Groundwater Monitoring Work Plan, dated August 2024, included advancement of 17 soil borings via hand auger in the northern portion of Lot 4 and the north and northwestern portions of Lot 5, in order to delineate the extent of contamination above ADEC Human

Health cleanup criteria, and groundwater monitoring of the existing wells. Difficulties in the field, including soil compaction and monitoring wells that could not be located (described in detail in Section

3.1), prevented the completion of the soil sampling activities and sampling of several groundwater monitoring wells. Twelve monitoring wells were sampled during September of 2024.

Because of those difficulties, BGES’ Site Delineation & Groundwater Monitoring Work Plan, Addendum

#1, dated November 2024, detailed the advancement of the 17 soil borings via truck-mounted auger. The work plan addendum also described monitoring well maintenance activities to be performed, including removing the blockage in MW06, replacing three monitoring wells (MW11, MW15, and MW16), and sampling these four monitoring wells. Due to concerns regarding the potential representativeness of

2024 & 2025 Groundwater Monitoring Report

Page 3 of 17 24-002-02R3 samples collected shortly after flooding, the drilling was not performed; however, the replacement monitoring wells (MW11A, MW15A, and MW16A) were installed during November of 2024. One well

(MW16A) was sampled in September of 2025; however, Monitoring Well MW11A exhibited a sheen and

Monitoring Well MW15A was not able to be relocated.

3.0 FIELD ACTIVITIES

The activities presented below were performed by Qualified Environmental Professionals (QEPs) as defined by the ADEC. The onsite activities were performed between September 24, 2024 and September

8, 2025 in general accordance with the ADEC Field Sampling Guidance (August 2024), BGES’ Site

Delineation & Groundwater Monitoring Work Plan (August 15, 2024), and BGES’ Work Plan Addendum

#1 (November 5, 2024).

3.1 Work Plan Deviations

Deviations from the ADEC-approved work plan and work plan addendum included the following:

September 2024 deviations

BGES personnel were unable to locate Monitoring Wells MW11, MW15, and MW16. These wells were thus unable to be sampled during September of 2024.

BGES planned to advance 17 hand-augered soil borings; however, soil boring activities were suspended after multiple unsuccessful attempts to advance a hand auger through rocky and compacted soils. Additionally, an auger bit was broken off at approximately 24 inches bg and was unable to be recovered. As such, BGES was unable to complete the soil borings.

Monitoring Well MW06 exhibited a blockage that appeared to be associated with a well boom that was apparently stuck in the well. Therefore, this well was not sampled.

November 2024 deviations

During well installation activities, an attempt was made to measure the depths to water in the new monitoring wells using an electronic water level indicator; however, due to cold weather conditions the instrument was unable to function, and the groundwater was beginning to freeze. Therefore, the depths of the new well screens were decided using the water depths listed in the 2023 report and visual observations at the time of installation.

BGES planned to advance the 17 soil borings mentioned above, and to collect groundwater samples from the newly-installed wells. However, because of extreme flooding just prior to these efforts, the ADEC had concerns regarding the representativeness of the samples and encouraged

2024 & 2025 Groundwater Monitoring Report

Page 4 of 17 24-002-02R3 delaying the sampling efforts. As such, no soil or groundwater samples were collected during this field effort.

September 2025 deviations

Monitoring Well MW06 was damaged beyond repair upon our arrival and therefore we did not attempt to remove the obstruction that was observed previously or insert a new well boom.

During development of Monitoring Well MW11, a sheen was observed on the development water.

As such, a sample was not collected from this well for laboratory analysis.

Monitoring Well MW15 could not be located, and thus we were unable to collect a sample from this well for laboratory analysis.

A trip blank sample was inadvertently not submitted to the laboratory with the groundwater samples that were collected on September 8, 2025.

3.2 Soil Delineation

Two BGES personnel mobilized to the subject property on September 25, 2024, equipped with a stainless steel hand auger. BGES attempted to complete soil delineation activities in accordance with the approved work plan, to include advancement of 17 soil borings. Upon arrival, Soil Boring SB1 was initiated just south of Monitoring Well MW11 (installed in 2021). However, an obstruction was encountered after only a few inches of digging. The ground was extremely hard-packed with gravel. BGES attempted to advance four more soil borings (SB2 through SB5) to the west of Monitoring Well MW10 (installed in 2020);

however, multiple obstructions were encountered in these soil borings between depths of 18 and 24 inches

bg. While attempting to overcome an obstruction in Soil Boring SB5 at approximately 24 inches bg, the bit broke off of the hand auger and could not be retrieved from the soil boring. All attempts to advance soil borings with the hand auger ceased at this point.

The locations of Soil Borings SB1, SB2, SB3, SB4, and SB5 are presented on Figure 3. Soil boring logs are included in Appendix A and photographs of the attempted soil boring activities are included in

Appendix B.

3.3 2024 Groundwater Monitoring

Prior to collecting groundwater samples in September of 2024, BGES measured the depth to groundwater and total depth of each monitoring well (except for those wells that could not be located) with a water level indicator and documented the presence of free product, if any. The probe of the water level indicator

2024 & 2025 Groundwater Monitoring Report

Page 5 of 17 24-002-02R3 and all reusable equipment placed inside the wells were decontaminated prior to use in each well with an

Alconox (laboratory-grade detergent) solution, followed by a deionized water rinse. A preexisting sorbent boom containing dissolving petroleum remediation product was temporarily removed from Monitoring

Well MW01 prior to measuring the depth to water and total depth of the well. The depth to water and total depth measurements were recorded on groundwater monitoring logs which are included in Appendix

A and summarized in Table 1. Photographs of project activities are included in Appendix B.

During September 24 through 26, 2024, groundwater samples were collected from Monitoring Wells

MW08, MW07, MW03, MW12, MW05, MW14, MW01, MW02, MW13, MW09, MW10, and MW04

(in that order), using low-flow sampling technology (Figure 2). As mentioned in Section 3.1, above, Monitoring Well MW06 could not be sampled due to an obstruction, and Monitoring Wells MW11, MW15, and MW16 could not be located. In the monitoring wells that were sampled, the bladder pump intake was set approximately 6 inches below the water table. The bladder pump was connected by high-density polyethylene (HDPE) tubing to a compressor and controller, and to a YSI water quality meter and flow-through cell. The pumping rate during the purging activities was between 100 and 350 milliliters per minute (mL/min). Water quality parameters [pH, temperature, oxidation reduction potential (ORP), and conductivity] were monitored during purging. Groundwater samples were collected when parameters stabilized or after approximately three well volumes were purged from each well; whichever occurred first. Prior to collecting the samples, the flow-through cell was removed from the sample collection train in accordance with ADEC Field Sampling Guidance. Groundwater was pumped directly into the laboratory-supplied sample jars, and the containers for volatile analyses were filled first. Care was taken during the sampling process to ensure that none of the preservative spilled from the containers and to minimize headspace within the vials destined for volatile analyses. The pumping rate during the sampling activities was between 100 mL/min and 125 mL/min.

As a quality control (QC) measure, duplicate groundwater samples were collected from MW09 and

MW10. These duplicate samples were submitted “blindly” to the laboratory for analysis. A trip blank sample also accompanied the primary and duplicate samples during the entire sampling and handling process. All samples were labeled, stored, and shipped in a chilled cooler under chain of custody protocol to Eurofins Laboratory in Spokane, Washington (Eurofins Spokane); an ADEC-approved laboratory.

3.4 Installation of Replacement Monitoring Wells

Because Monitoring Wells MW11, MW15, and MW16 could not be located during the September 2024 groundwater sampling activities, BGES subcontracted Discovery Drilling, Inc. to replace these wells.

2024 & 2025 Groundwater Monitoring Report

Page 6 of 17 24-002-02R3

Prior to mobilizing to the subject property for installation of the replacement wells, BGES personnel coordinated with the Alaska One-Call Center for the locating of underground utilities. On November 13, 2024, the replacement wells (identified as Monitoring Wells MW11A, MW15A, and MW16A) were installed. Because the groundwater was beginning to freeze upon exposure to ambient air, rendering the water level indicator ineffective; the precise depth to groundwater could not be determined. Therefore, the prior depths to groundwater within the original wells were assumed for the purposes of placing the well screens within the new monitoring wells. The monitoring wells were constructed with 2-inch diameter polyvinyl chloride (PVC) casing from the ground surface to approximately 0.5 to 3 feet below grade (bg), and 5 feet of 2-inch diameter 10-slot PVC well screen from the bottom of the PVC casing to approximately 6 to 8.5 feet bg; such that the screens approximately bisect the groundwater table. Well

Completion logs are included in Appendix A.

Soil cuttings generated during the installation activities were placed in a 55-gallon drum that was stored in a locked shipping container. A waste characterization sample was collected from the drum on

November 13, 2024 and labeled, stored, and shipped in a chilled cooler under chain of custody protocol to Eurofins Spokane.

3.5 2025 Groundwater Monitoring

On September 4 and 5, 2025, BGES attempted to locate Monitoring Wells MW01 and MW06 in order to perform maintenance, and to locate MW11A, MW15A, and MW16A in order to collect groundwater samples. Upon inspecting the wells, sheen was observed on water bailed from Monitoring Wells MW01 and MW11A, so well booms were placed in these wells and groundwater samples were not collected for laboratory analyses. The depth to groundwater in Monitoring Well MW11A was inadvertently not recorded. As discussed in Section 3.1, above, Monitoring Well MW06 was damaged beyond repair. The

PVC casing was broken at the ground surface and was not encased by a protective cover. Additionally, the PVC well casing was full of sediment. Therefore, no maintenance activities were performed on

Monitoring Well MW06. Lastly, Monitoring Well MW15A could not be located at the time of these activities.

On September 8, 2025, Monitoring Well MW16A was located and in good condition. The depth to water was measured to be 3.59 feet bg, which is within the screened interval of 0.5 to 5.5 feet bg. As such, a groundwater sample and a duplicate sample were collected from this well. Prior to collecting the groundwater samples, BGES measured the depth to groundwater and total depth of the monitoring well with a water level indicator. The probe of the water level indicator and all reusable equipment placed

2024 & 2025 Groundwater Monitoring Report

Page 7 of 17 24-002-02R3 inside the well were decontaminated prior to use with an Alconox (laboratory-grade detergent) solution, followed by a deionized water rinse. The depth to water and total depth measurements were recorded on a groundwater monitoring log which is included in Appendix A and summarized in Table 1.

Groundwater samples (Figure 2) were collected from Monitoring Well MW16A using low-flow sampling technology. The bladder pump intake was set approximately 6 inches below the water table. The bladder pump was connected by HDPE tubing to a compressor and controller, and to a YSI water quality meter and flow-through cell. The pumping rate during the purging activities was approximately 250 milliliters per minute (mL/min). Water quality parameters (pH, temperature, ORP, and conductivity) were monitored during purging. Groundwater samples were collected after approximately three well volumes were purged from the well. Prior to collecting the samples, the flow-through cell was removed from the sample collection train in accordance with ADEC Field Sampling Guidance. Groundwater was pumped directly into the laboratory-supplied sample jars, and the containers for volatile analyses were filled first.

Care was taken during the sampling process to ensure that none of the preservative spilled from the containers and to minimize headspace within the vials destined for volatile analyses. The pumping rate during the sampling activities was approximately 100 mL/min.

As a QC measure, the duplicate groundwater sample collected from MW16A was submitted “blindly” to the laboratory for analysis. The primary and duplicate samples were labeled, stored, and shipped in a chilled cooler under chain of custody protocol to Eurofins Spokane; an ADEC-approved laboratory. A trip blank sample was inadvertently not submitted to the laboratory with the project samples. A copy of the laboratory report is included in Appendix C and data quality checklists are included in Appendix D.

3.6 Disposal of Investigation Derived Waste

Investigation-derived waste included rope, bailers, bladders, tubing, soil cuttings, purge water, development water, decontamination water, an empty methanol preservative container, and miscellaneous personal protective equipment. The drum of soils was transported by US Ecology to Anchorage, Alaska for disposal on September 5, 2025 (see disposal documentation in Appendix E). Approval from the ADEC was inadvertently not obtained prior to transporting the drum of soils offsite. All other solid waste was disposed of as municipal waste. All liquid wastes were filtered through granular activated carbon (GAC) and discharged onsite in a manner that did not cause undue erosion, at least 100 feet from surface water bodies. The GAC was shipped by BGES personnel to Anchorage, Alaska for continued use on other project sites with similar contaminants of concern.

2024 & 2025 Groundwater Monitoring Report

Page 8 of 17 24-002-02R3

4.0 EVALUATION OF LABORATORY DATA

Twelve groundwater samples, from Monitoring Wells MW01, MW02, MW03, MW04, MW05, MW07, MW08, MW09, MW10, MW12, MW13, and MW14, plus two duplicate samples from Monitoring Wells

MW09 and MW10, were collected during the September 2024 sampling event. One groundwater sample and one duplicate sample from Monitoring Well MW16A were collected during the September 2025 sampling event. All groundwater samples were submitted to Eurofins Spokane and were analyzed for

DRO by Alaska Method (AK) 102, RRO by AK 103, VOCs by Environmental Protection Agency (EPA)

Methods 8260D and 8260D Selected Ion Monitoring (SIM), and PAHs by EPA Method 8270E SIM.

One soil sample was collected from the drum of soil cuttings that were generated during the monitoring well replacement activities. The soil sample was submitted to Eurofins Spokane for analysis of DRO, RRO, VOCs, and PAHs by the same methods listed above, and GRO by AK 101, polychlorinated biphenyls (PCBs) by EPA Method 8082A, and Resource Conservation and Recovery Act (RCRA) Metals by EPA Methods 6020B and 7471B to characterize the waste for disposal.

As a QC procedure, trip blank samples for soil and water accompanied the samples that were collected in

2024 at all times from sample collection until submission to the laboratory. The trip blank samples were analyzed for GRO and VOCs by the same methods described above, to evaluate the potential for cross-contamination of the samples to have occurred. As noted above, a trip blank sample was inadvertently omitted from the cooler during the 2025 sampling event. However, because only one sample was submitted to the laboratory during that sampling event, it is our opinion that the lack of a trip blank sample does not affect our interpretation of the laboratory data for their intended use, as no other samples were present to potentially cause cross-contamination.

Groundwater cleanup criteria for DRO, RRO, VOCs, and PAHs are obtained from ADEC 18 Alaska

Administrative Code (AAC) 75.345, Table C, Groundwater Human Health Cleanup Levels (October 18, 2023). Soil cleanup criteria for VOCs, PAHs, PCBs, and RCRA metals are obtained from ADEC 18 AAC

75.341, Table B1, Method 2, Migration to Groundwater values, except for benzo[a]pyrene, benzo[b]fluoranthene, benzo[g,h,i]perylene, benzo[k]fluoranthene, n-butylbenzene, dibenzo[a,h]anthracene, and indeno[1,2,3-cd]pyrene, which are obtained from the more stringent Under

40-inch zone (referring to annual precipitation) human health pathway (October 18, 2023). Soil cleanup criteria for GRO, DRO, and RRO are obtained from Table B2, Method 2, Under 40-Inch Zone (referring to annual precipitation), Migration to Groundwater values; except for RRO, which is obtained from the more stringent Ingestion pathway (October 18, 2023).

2024 & 2025 Groundwater Monitoring Report

Page 9 of 17 24-002-02R3

The groundwater samples were labeled, for example, MW01-092524, where the prefix MW01 indicates the monitoring well from which the groundwater sample was collected and -092524 indicates the month, day, and year the sample was collected. The soil sample was labeled WC01-111324, where the prefix

WC01 indicates the waste characterization sample number and -111324 indicates the month, day, and year the sample was collected. For brevity in the text and in the associated figures, the samples are referred to as MW01, for example, with the date omitted.

4.1 2024 Groundwater Samples

The monitoring wells were not sampled in order of least to most contaminated, as locating the wells was time intensive and the wells were primarily sampled opportunistically, for the sake of efficiency.

Monitoring Well MW02, which did not contain contaminants at concentrations exceeding ADEC cleanup criteria during the 2022 sampling event, was sampled immediately after Monitoring Well MW14 during this sampling event, which has historically contained a greater degree of contamination. The 2024 samples from these wells both contained chloroform and naphthalene at concentrations exceeding the ADEC cleanup criteria. As such, there is a potential for the results from Monitoring Well MW02 to be biased high, and are qualified with a ”J” in Table 2 and should be considered estimates. The sampling order did not appear to influence the degree of contamination identified in any other wells, as those wells were either sampled after a less-contaminated well, or the results were either below the ADEC cleanup criteria or greatly exceeded the ADEC cleanup criteria.

Sample MW01 exhibited concentrations of DRO [6,800 micrograms per liter (µg/L)], 1,2,4-trimethylbenzene (120 µg/L), 1,3,5-trimethylbenzene (73 µg/L), chloroform (3.1 µg/L), naphthalene (290 µg/L), and 1-methylnaphthalene (71 µg/L), that exceeded their respective ADEC cleanup criteria.

Sample MW02 exhibited concentrations of chloroform (5.6 µg/L) and naphthalene (1.8 µg/L), that exceeded their respective ADEC cleanup criteria. As noted above, these results are qualified with a “J” in Table 2 and should be considered estimates.

Samples MW03 and MW07 did not exhibit any contaminant concentrations that exceeded their respective

ADEC cleanup criteria.

Sample MW04 exhibited a concentration of naphthalene (5.5 µg/L) that exceeded its ADEC cleanup criterion.

Sample MW05 exhibited concentrations of DRO (2,200 µg/L) and naphthalene (51 µg/L) that exceeded

2024 & 2025 Groundwater Monitoring Report

Page 10 of 17 24-002-02R3 their respective ADEC cleanup criteria.

Sample MW08 exhibited a concentration of chloroform (5.8 µg/L) that exceeded its ADEC cleanup criterion.

Samples MW09 and MW17 (duplicate of MW09) exhibited concentrations of DRO (2,800 µg/L), chloroform (4.8 µg/L), naphthalene (67 µg/L), and 1-methylnaphthalene (32 µg/L) that exceeded their respective ADEC cleanup criteria. These detections represent the maximum concentrations reported in

Samples MW09 and MW17.

Samples MW10 and MW18 (duplicate of MW10) exhibited concentrations of DRO (2,500 µg/L) and naphthalene (24 µg/L) that exceeded their respective ADEC cleanup criteria. These detections represent the maximum concentrations reported in Samples MW10 and MW18.

Sample MW12 exhibited concentrations of DRO (12,000 µg/L), 1,2,4-trimethylbenzene (57 µg/L), 1,3,5-trimethylbenzene (68 µg/L), benzene (6.1 µg/L), naphthalene (55 µg/L), 1-methylnaphthalene (62 µg/L), and 2-methylnaphthalene (45 µg/L) that exceeded their respective ADEC cleanup criteria.

Sample MW13 exhibited concentrations of DRO (4,200 µg/L), 1,2,4-trimethylbenzene (79 µg/L), benzene

(7.3 µg/L), chloroform (5.0 µg/L), and naphthalene (140 µg/L) that exceeded their respective ADEC cleanup criteria.

Sample MW14 exhibited concentrations of chloroform (4.9 µg/L) and naphthalene (1.8 µg/L) that exceeded their respective ADEC cleanup criteria.

Various analytes were also detected in the groundwater samples at concentrations that exceeded the laboratory’s reporting limits (RLs) but that were less than the ADEC cleanup criteria.

Analytical results for the September 2024 groundwater samples are presented in Table 2, the laboratory analytical data package is included in Appendix C, and the sample results are shown on Figure 2.

4.2 2025 Groundwater Samples

Samples MW16A and MW17 (duplicate of MW16A) exhibited concentrations of DRO (4,100 µg/L) and naphthalene (9.5 µg/L) that exceeded their respective ADEC cleanup criteria. These detections represent the maximum concentrations reported in Samples MW16A and MW17.

2024 & 2025 Groundwater Monitoring Report

Page 11 of 17 24-002-02R3

Various analytes were also detected in these groundwater samples at concentrations that exceeded the laboratory’s RLs but that were less than the ADEC cleanup criteria.

Analytical results for the September 2025 groundwater samples are presented in Table 2, the laboratory analytical data package is included in Appendix C, and the sample results are shown on Figure 2.

4.3 Waste Characterization Soil Sample

Sample WC01 exhibited concentrations of GRO [1,000 milligrams per kilogram (mg/Kg)], DRO (3,500 mg/Kg) 1,2,3-trichloropropane (0.16 mg/Kg), 1,3,5-trimethylbenzene (4.2 mg/Kg), naphthalene (5.7 mg/Kg), total xylenes (1.7 mg/Kg), 1-methylnaphthalene (2.3 mg/Kg), 2-methylnaphthalene (2.2 mg/Kg), and arsenic (3.4 mg/Kg) that exceeded their respective ADEC cleanup criteria.

Various analytes were also detected in the soil sample at concentrations that exceeded the laboratory’s

RLs but that were less than the ADEC cleanup criteria.

Analytical results for the waste characterization soil sample are presented in Table 3 and the laboratory analytical data package is included in Appendix C.

5.0 LABORATORY DATA QUALITY REVIEW

Data quality was reviewed in accordance with ADEC guidance and standard industry practices. An ADEC laboratory data review checklist was completed for each work order containing groundwater samples, and the checklists are included in Appendix D. The checklists provide an overview of the quality of the laboratory data. The following is a discussion of our evaluation of sample conditions and laboratory procedures for the groundwater samples collected during the September 2024 and September 2025 sampling activities.

5.1 Eurofins Spokane Report 590-27265-1 (2024 Groundwater Samples)

The groundwater sample containers were labeled, placed in an ice-filled cooler, and shipped via Alaska

Airlines Goldstreak along with chain-of-custody documentation to Eurofins Spokane. A trip blank sample accompanied the containers scheduled for volatile analyses (GRO and VOCs) throughout the entirety of the sampling process and transportation to the laboratory. The samples contained the proper preservatives for the requested analyses.

The temperatures of the sample coolers were measured at the time of receipt to be 5.0 and 5.5 degrees

Celsius, which are within the ADEC-prescribed optimal range of 0 to 6 degrees Celsius. A case narrative

2024 & 2025 Groundwater Monitoring Report

Page 12 of 17 24-002-02R3 was included in the laboratory report and several QC failures were identified, as discussed below.

The recovery of acetone within the continuing calibration verification (CCV) sample was below the laboratory’s acceptance criteria, indicating the potential for the reported concentrations of acetone to be biased low in the associated project samples. However, because acetone was not detected in the project samples at the laboratory’s RLs, and because the RLs were at least two orders of magnitude below the

ADEC cleanup criterion; it is our opinion that this QC failure does not affect our interpretation of the data.

The recovery of surrogate 4-bromofluorobenzene associated with the analysis of VOCs in Sample MW07 exceeded the laboratory’s acceptance limit, indicating the potential for the reported concentrations of the associated VOCs in this sample to be biased high. However, because none of the associated VOCs were detected in Sample MW07 at the laboratory’s RLs, and because the RLs were less than the ADEC cleanup criteria; it is our opinion that this QC failure does not affect our interpretation of the data.

Samples MW01, MW02, MW03, MW05, MW07, MW08, MW12, and MW14 were reanalyzed for VOCs by EPA Method 8260D because of laboratory QC failures with the initial analyses. The reanalyses were performed out of holding time, resulting in the potential for the reported concentrations of VOCs via

8260D to be biased low in the samples listed above. For this reason, the reported concentrations of VOCs via 8260D in the affected samples are qualified with “J” in Table 2 and should be considered estimates.

However, because one or more analytes were detected in Samples MW01, MW02, MW05, MW08, MW12, and MW14 at concentrations exceeding ADEC cleanup criteria, and because the RLs for all VOCs via 8260D in Samples MW03 and MW07 were at least 75 percent less than the applicable ADEC cleanup criteria (except for those RLs that exceeded the ADEC cleanup criteria, as discussed further below); it is our opinion that this QC failure does not affect our interpretation of the data.

The laboratory reported that laboratory contamination of chloroform is suspected in all of the project samples. For this reason, the reported concentrations of chloroform in the project samples are qualified with “J” in Table 2 and should be considered estimates. However, because various other analytes were detected at concentrations exceeding the ADEC cleanup criteria in all of these project samples that exhibited chloroform at concentrations exceeding the ADEC cleanup criterion, it is our opinion that this

QC failure does not affect our interpretation of the data.

The trip blank sample contained bromoform, chlorodibromomethane, chloroform, and dichlorobromomethane at concentrations greater than the MDLs but less than the RLs; indicating a potential for cross-contamination of the samples to have occurred. For this reason, the reported

2024 & 2025 Groundwater Monitoring Report

Page 13 of 17 24-002-02R3 concentrations of these analytes in the project samples are qualified with a “J” in Table 2 and should be considered estimates. However, because bromoform and chlorodibromomethane were not detected at the laboratory’s RLs in the project samples, and because dichlorobromomethane was not reported at concentrations exceeding the ADEC cleanup criterion in the project samples, and because various other analytes were detected at concentrations exceeding the ADEC cleanup criteria in all of the project samples that exhibited chloroform at concentrations exceeding the ADEC cleanup criterion; it is our opinion that this QC failure does not affect our interpretation of the data.

Sample MW17-092624 was a duplicate of Sample MW09 and was collected to evaluate field sampling precision. The relative percent differences (RPDs) between the reported concentrations of DRO, RRO, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 4-isopropyltoluene, benzene, chloroform, dichlorofluoromethane, isopropylbenzene, naphthalene, trichlorofluoromethane, sec-butylbenzene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, acenaphthylene, anthracene, fluorene, and phenanthrene ranged from 0 to 21 percent, which are below the acceptable limit of 30 percent. This indicates good field sampling precision with respect to these analytes. The RPD for n-butylbenzene was

40 percent, indicating poor field sampling precision with respect to this analyte. Therefore, the concentrations of n-butylbenzene in these two samples are qualified with a “J” in Table 2 and should be considered estimates. However, the concentrations of n-butylbenzene in these samples are two orders of magnitude below the ADEC cleanup criterion; therefore, it is our opinion that this QC failure does not impact our interpretation of the data. The RPDs for the remaining analytes could not be calculated as those analytes were not detected in one or both of the samples in this duplicate sample pair.

Sample MW18 was a duplicate of Sample MW10 and was collected to evaluate field sampling precision.

The RPDs between the reported concentrations of DRO, RRO, 2-hexanone, benzene, chloroform, dichlorofluoromethane, ethylbenzene, naphthalene (via 8260D), total xylenes, and trichlorofluoromethane ranged from 0 to 21 percent, which are below the acceptable limit of 30 percent. This indicates good field sampling precision with respect to these analytes. The RPDs for 1,3,5-trimethylbenzene, 1-methylnaphthalene, acenaphthene, acenaphthylene, anthracene, fluorene, and naphthalene (via 8270E

SIM) ranged from 37 to 161 percent, indicating poor field sampling precision with respect to these analytes. Therefore, the concentrations of these analytes in these two samples are qualified with a “J” in

Table 2 and should be considered estimates. However, because another analyte concentration in these samples exceeded the ADEC cleanup criterion, rendering our interpretation that these water samples indicate contamination in this well, it is our opinion that this QC failure does not impact our interpretation

2024 & 2025 Groundwater Monitoring Report

Page 14 of 17 24-002-02R3 of the data. The RPDs for the remaining analytes could not be calculated as those analytes were not detected in one or both of the samples in this duplicate sample pair.

The RLs and/or method detection limits (MDLs) for numerous analytes exceeded the applicable ADEC cleanup criteria. As such, it cannot be determined if the actual concentrations of these analytes within these samples exceed the ADEC cleanup criteria, and these analytes have been italicized in Table 1 (and also underlined where the MDLs exceeded the applicable ADEC cleanup criteria).

5.2 Eurofins Spokane Report 590-33069-1 (2025 Groundwater Samples)

The groundwater sample containers were labeled, placed in an ice-filled cooler, and shipped via Alaska

Airlines Goldstreak along with chain-of-custody documentation to Eurofins Spokane. The samples contained the proper preservatives for the requested analyses. A trip blank sample was inadvertently not submitted with the project samples.

The temperature of the sample cooler was measured at the time of receipt to be 0.1 degree Celsius, which is within the ADEC-prescribed optimal range of 0 to 6 degrees Celsius. A case narrative was included in the laboratory report and several QC failures were identified, as discussed below.

The recovery of 4-methyl-2-pentanone within the CCV sample was below the laboratory’s acceptance criteria, indicating the potential for the reported concentrations of this analyte to be biased low in the associated project samples. However, because 4-methyl-2-pentanone was not detected in the project samples at the laboratory’s RLs, and because the RLs were two orders of magnitude below the ADEC cleanup criterion; it is our opinion that this QC failure does not affect our interpretation of the data.

The recoveries of acetone and chloroethane in the Laboratory Control Sample (LCS) and LCS Duplicate exceeded the laboratory control limits, indicating a potential for the reported concentrations of these analytes to be biased high in the project samples. However, because acetone and chloroethane were not detected in the project samples at the laboratory’s RLs, and because the RLs were below the ADEC cleanup criteria; it is our opinion that this QC failure does not affect our interpretation of the data.

The recoveries of 1,1,2-trichlorotrifluoroethane, acetone, carbon disulfide, and chloroethane within the

CCV sample exceeded the laboratory’s acceptance criteria, indicating the potential for the reported concentrations of these analytes to be biased high in the associated project samples. However, because the affected analytes were not detected in the project samples at the laboratory’s RLs, and because the

RLs for those analytes were below the ADEC cleanup criteria; it is our opinion that this QC failure does

2024 & 2025 Groundwater Monitoring Report

Page 15 of 17 24-002-02R3 not affect our interpretation of the data.

The method blank exhibited a detection of 2-hexanone between the RL and the MDL, indicating the potential for the concentrations of this analyte in the project samples to be biased high. However, 2-hexanonone was not detected in the project samples; therefore, it is our opinion that this QC failure does not impact the interpretation of the data.

Sample MW17-090825 was a duplicate of Sample MW16A and was collected to evaluate field sampling precision. The RPDs between the reported concentrations of DRO, RRO, 4-isopropyltoluene, dichlorofluoromethane, toluene, total xylenes, tert-butylbenzene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, acenaphthylene, fluorene, and naphthalene ranged from 2 to 29 percent, which are below the acceptable limit of 30 percent. This indicates good field sampling precision with respect to these analytes. The RPDs for 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, n-propylbenzene, and trichlorofluoromethane ranged from 38 to 91 percent, indicating poor field sampling precision with respect to these analytes. Therefore, the concentrations of these analytes in these two samples are qualified with a “J” in Table 2 and should be considered estimates. However, because multiple unaffected analytes in these samples exhibited contaminant concentrations that exceeded

ADEC cleanup criteria, it is our opinion that this QC failure does not impact our interpretation of the samples as being representative of contaminated groundwater. The RPDs for the remaining analytes could not be calculated as those analytes were not detected in one or both of the samples in this duplicate sample pair.

The RLs and/or MDLs for numerous analytes exceeded the applicable ADEC cleanup criteria. As such, it cannot be determined if the actual concentrations of these analytes within these samples exceed the

ADEC cleanup criteria, and these analytes have been italicized in Table 1 (and also underlined where the

MDLs exceeded the applicable ADEC cleanup criteria).

6.0 CONCEPTUAL SITE MODEL

A graphical conceptual site model detailing the various potential exposure media, transport mechanisms, exposure pathways, and human receptors for identified contamination at this site was prepared and is included in Appendix F. The media identified at the site to which the contamination was directly released are groundwater and subsurface soils. Migration to groundwater, volatilization, flow to surface water, and flow to sediments were identified as transport mechanisms through which contamination could have mobilized. The potential exposure pathways include incidental soil ingestion, dermal absorption of soil, 2024 & 2025 Groundwater Monitoring Report

Page 16 of 17 24-002-02R3 ingestion of groundwater, dermal absorption of contaminants in groundwater, inhalation of indoor and outdoor air, ingestion of surface water, dermal absorption of contaminants in surface water, and direct contact with sediment. The potential receptors of contamination include current and future residents, commercial or industrial workers, site visitors, construction workers, farmers or subsistence harvesters, and subsistence consumers.

7.0 CONCLUSIONS AND RECOMMENDATIONS

Site characterization activities were performed from September 24 to 26, 2024, November 13, 2024, and

September 8, 2025. The purpose of these activities was to further characterize the soil and groundwater contamination onsite stemming from historical releases of fuel that was observed to be seeping into the basement of the former school. However, because of the challenges outlined in Section 3.1, above, none of the soil delineation efforts were successful. As such, additional site characterization activities will likely be required to further define the extent of soil contamination on the subject property.

Groundwater samples were collected from 12 monitoring wells in 2024 and 1 additional monitoring well in 2025. All samples were analyzed for DRO, RRO, VOCs, and PAHs. Except for samples collected from MW03 and MW07, every sample exhibited concentrations of DRO, VOCs, and/or PAHs that exceeded the ADEC cleanup criteria. Based on these results, it is recommended that ongoing groundwater monitoring be performed. The ADEC has also indicated that Monitoring Well MW06 should be replaced, and that depths to groundwater shall be measured in all monitoring wells during future sampling events.

8.0 EXCLUSIONS AND CONSIDERATIONS

This report presents facts, observations, and inferences based on conditions observed during the period of our project activities, and only those conditions that were evaluated as part of our scope of work. Our conclusions are based solely on our observations made and work conducted and only apply to the immediate vicinities of the locations where samples were collected. In addition, changes to site conditions may have occurred since the completion of our project activities. These changes may be from the actions of man or nature. Changes in regulations may also impact the interpretation of site conditions. BGES will not disclose our findings to any parties other than our client as listed above, except as directed by our client, or as required by law.

The above-described activities were conducted by QEPs Lisa Vitale, Environmental Scientist II, Carson

Kent, former Environmental Scientist II, and Javier Acuna, Environmental Scientist I of BGES. This report was prepared by Emily Adler, Environmental Scientist I, and Rose Kayotuk, Senior Environmental

2024 & 2025 Groundwater Monitoring Report

Page 17 of 17 24-002-02R3

Scientist I. Ms. Adler and Ms. Kayotuk have performed numerous site assessments and remediation projects throughout Alaska. This report was reviewed and approved by Robert N. Braunstein, C.P.G. and

Principal Geologist of BGES. Mr. Braunstein has more than 40 years of professional geological and environmental consulting experience, and he has conducted and managed thousands of environmental projects involving site characterization and remediation efforts throughout Alaska and the lower 48 states.

Sincerely, BGES, INC, Prepared By: Reviewed & Approved By:

Emily Adler Rose Kayotuk Robert N. Braunstein, C.P.G.; P.G.

Environmental Scientist I Senior Environmental Scientist I Principal Geologist

February 2026 Figure 1

Former BIA/IHS Hospital/ School Pipeline Release

Property Vicinity Map

0 1/4 1/2 3/4 1

Approximate Scale in Miles

Approximate Site Location

Source: USGS Topo Map Kotzebue D-2 NE, 2019

KEY

Former Pipeline Location

Approximate Monitoring Well Location (concentrations exceed the ADEC cleanup criteria)

Approximate Monitoring Well Location (concentrations are below the ADEC cleanup criteria)

Approximate Monitoring Well Location (not sampled)

The greatest detected concentrations between the primary and duplicate sample pair are shown.

ADEC = Alaska Department of Environmental Conservation; DRO = diesel range organics; µg/ = micrograms per liter

Third Avenue

MW07-092424

No exceedances

MW01-092524

DRO = 6,800 µg/L 1,2,4-Trimethylbenzene = 120 µg/L 1,3,5-Trimethylbenzene = 73 µg/L Chloroform = 3.1 µg/L Naphthalene = 290 µg/L 1-Methylnaphthalene = 71 µg/L

MW10-092624

Duplicate MW18-092624*

DRO = 2,500 µg/L Naphthalene = 24 µg/L

MW09-092624

Duplicate MW17-092624*

DRO = 2,800 µg/L Chloroform = 4.8 µg/L Naphthalene = 67 µg/L 1-Methylnaphthalene = 32 µg/L

MW08-092424

Chloroform = 5.8 µg/L

MW13-092624

DRO = 4,200 µg/L 1,2,4-Trimethylbenzene = 79 µg/L Benzene = 7.3 µg/L Chloroform = 5.0 µg/L Naphthalene = 140 µg/L

February 2026 Figure 2

Former BIA/IHS Hospital/ School Pipeline Release

Kotzebue, Alaska

2024 & 2025 Groundwater Monitoring Well Results

0 50 100 150 200

Approximate Scale in Feet

MW11

Not sampled

MW15

Not sampled

MW14-092524

Chloroform = 4.9 µg/L Naphthalene = 1.8 µg/L

MW02-092524

Chloroform = 5.6 µg/L Naphthalene = 1.8 µg/L

MW04-092624

Naphthalene = 5.5 µg/L

MW06

Not sampled

MW12-092524

DRO = 12,000 µg/L 1,2,4-Trimethylbenzene = 57 µg/L 1,3,5-Trimetlhylbenzene = 68 µg/L Benzene = 6.1 µg/L Naphthalene = 55 µg/L 1-Methylnaphthalene = 62 µg/L 2-Methylnaphthalene = 45 µg/L

MW05-092524

DRO = 2,200 µg/L Naphthalene = 51 µg/L

MW03-092424

No exceedances

MW16A-090825

Duplicate MW17-090825*

DRO = 4,100 µg/L Naphthalene = 9.5 µg/L

February 2026 Figure 3

Former BIA/IHS Hospital/School Pipeline Release

Attempted Soil Boring Locations

0 125 250 500

Approximate Scale in Feet

KEY

= Attempted Soil Boring Location (2024) = Monitoring Well (Installed 2020)

= Monitoring Well (Installed 2021)

= Former Pipeline Location = Approximate Perimeter of Former

Building ft = feet; bg = below grade

SB1

Depth: 0.3 ft bg

SB2

Depth: 1.75 ft bg

SB3

Depth: ~2 ft bg SB4

Depth: 1 ft bg

SB5

Depth: ~2 ft bg

TABLE 1

KOTZEBUE BIA

KOTZEBUE ALASKA

MONITORING WELL SAMPLING DATA (2024/2025)

BGES, INC.

Well Number MW01 MW02 MW03 MW04 MW05 Date Sampled 09/25/24 09/25/24 09/24/24 09/26/24 09/25/24 Date of Depth and Elevation…