Attachment_1_Data_Gap_Inv_Rpt_Pgs_3001-3827.pdf

SECTION 9

References Alaska Department of Commerce, Community, and Economic Development, Division of Community and Regional Affairs. 2012. Alaska Community Database, Community Information Summaries, Mountain Village.

Alaska Department of Environmental Conservation (ADEC). 2010. Draft Field Sampling Guidance. May.

Alaska Department of Environmental Conservation (ADEC). 2011. Implementing Guidance for the Method 3 Hydrocarbon Risk Calculator. February 25.

Alaska Department of Natural Resources (ADNR). 2013. Well Log Tracking System.

http://www.navmaps.alaska.gov/welts. Accessed during February 2013.

Beans, Robert. 1980. Maintenance Report, Mountain Village Armory.

CH2M HILL. 2011. Final Work Plan for Site Characterization at 21 Alaska Federal Scout Readiness Centers.

Prepared for Alaska Army National Guard. April.

Clearwater Environmental, Inc. (Clearwater). 2005. Final Interim Removal Action Report, Federal Scout Armory, Mountain Village, Alaska. Prepared for Alaska Army National Guard. April.

ERM/Hart Crowser. 1999. Final Site Investigation, Army National Guard Scout Armory, Mountain Village, Alaska.

Prepared for Alaska Army National Guard. August.

Hoefler Consulting Group. 2005. Alternate Cleanup Level Demonstration, Mountain Village Federal Scout Armory Alaska Army National Guard Mountain Village, Alaska. Prepared for Alaska Army National Guard. December.

Integrated Concepts and Research Corporation and Science Applications International Corporation (ICRC/SAIC).

1999. Final Spill Prevention, Control & Countermeasure (SPCC) and Installation Spill Contingency (ISC) Plan, Mountain Village Federal Scout Armory. Prepared for Alaska Army National Guard. September.

Williams, John. 1970. Groundwater in the Permafrost Regions of Alaska. U.S. Geological Survey Professional Paper 696.

ANC123540011/ES012512133154ANC 8-1

http://www.navmaps.alaska.gov/welts

9 REFERENCES

8-2 ANC123540011/ES012512133154ANC

Appendix A Field Notes and Boring Logs

Appendix B Data Quality Evaluation and Laboratory Reports

(laboratory reports provided electronically only)

Appendix C Hydrocarbon Risk Calculator –

Cumulative Risk Results (source files provided electronically only)

Appendix D Response to Comments

F i na l

Nunapitchuk Federal Scout Readiness Center

Data Gap Investigation Report

Prepared for

Alaska Army National Guard Fort Richardson, Alaska

Contract No. W90FYQ-09-D-003 Delivery Order 2Z01

January 2013

949 East 36th Avenue

Suite 500 Anchorage, AK 99508

Contents Section Page

ANC/123540002/ES012512133903ANC III

Acronyms and Abbreviations ............................................................................................................................... v

1 Introduction ......................................................................................................................................... 1‐1

1.1 Goals and Objectives of Data Gap Investigation ............................................................................. 1‐1

1.2 Report Organization ........................................................................................................................ 1‐1

2 Site Background ................................................................................................................................... 2‐1

2.1 Site Location and Climate ................................................................................................................ 2‐1

2.2 Site Characteristics .......................................................................................................................... 2‐1

2.2.1 Surface Water ..................................................................................................................... 2‐1

2.2.2 Hydrogeology ...................................................................................................................... 2‐2

2.3 Site Description and History ............................................................................................................ 2‐2

3 Previous Investigations and Remedial Actions ...................................................................................... 3‐1

3.1 1994 Site Assessment ...................................................................................................................... 3‐1

3.2 1997 Preliminary Assessment and Remedial Investigation ............................................................. 3‐1

3.3 2000 Interim Remedial Action ......................................................................................................... 3‐2

3.4 2003 Alternate Cleanup Level Demonstration ................................................................................ 3‐2

3.5 2007 Compliance Cleanup Site Characterization ............................................................................. 3‐2

4 Data Gap Analysis ................................................................................................................................ 4‐1

4.1 Project Screening Levels .................................................................................................................. 4‐1

4.1.1 Soil Screening Levels ........................................................................................................... 4‐1

4.1.2 Groundwater Screening Levels ........................................................................................... 4‐1

4.2 Data Quality Objectives ................................................................................................................... 4‐3

4.3 Conceptual Site Model .................................................................................................................... 4‐3

4.4 Identification of Data Gaps .............................................................................................................. 4‐4

5 Field Activities...................................................................................................................................... 5‐1

5.1 Site Reconnaissance ........................................................................................................................ 5‐1

5.2 Sample Locations ............................................................................................................................. 5‐1

5.3 Soil Sampling .................................................................................................................................... 5‐1

5.4 Groundwater and Surface Water Sampling ..................................................................................... 5‐2

5.5 Quality Control ................................................................................................................................. 5‐5

5.5.1 Field Duplicate Samples ...................................................................................................... 5‐5

5.5.2 Equipment Blanks ............................................................................................................... 5‐5

5.5.3 Trip Blanks .......................................................................................................................... 5‐5

6 Contamination Assessment .................................................................................................................. 6‐1

6.1 Nature and Extent of Soil Contamination ........................................................................................ 6‐1

6.2 Nature and Extent of Groundwater and Surface Water Contamination ......................................... 6‐1

7 Cumulative Risk Assessment ................................................................................................................ 7‐1

7.1 Assessing Cumulative Risk ............................................................................................................... 7‐1

7.2 Cumulative Risk Results ................................................................................................................... 7‐1

8 Conclusions and Recommendations ..................................................................................................... 8‐1

8.1 Conclusions ...................................................................................................................................... 8‐1

8.2 Proposed Soil Alternative Cleanup Levels ....................................................................................... 8‐1

8.3 Recommended Remedial Actions .................................................................................................... 8‐3

8.3.1 Contaminated Soil .............................................................................................................. 8‐3

8.3.2 Contaminated Groundwater and Surface Water ............................................................... 8‐4

CONTENTS

IV ANC/123540002/ES012512133903ANC

8.4 Estimated Soil Volume ..................................................................................................................... 8‐4

8.5 Summary .......................................................................................................................................... 8‐4

9 References ........................................................................................................................................... 9‐1

Appendixes

A Field Notes, Boring Logs, and Well Logs B Data Quality Evaluation and Laboratory Reports (laboratory reports provided electronically only) C Hydrocarbon Risk Calculator – Cumulative Risk Results D Response to Comments

Tables

4‐1 Soil Screening Levels ......................................................................................................................................4‐2 4‐2 Groundwater Screening Levels ......................................................................................................................4‐2 5‐1 Field Screening Results for Soil ......................................................................................................................5‐2 6‐1 Soil Results for BTEX, DRO, GRO, and RRO ....................................................................................................6‐2 6‐2 Soil Results for PAHs ......................................................................................................................................6‐9 6‐3 Groundwater and Surface Water Results for BTEX, DRO, RRO, and GRO .................................................. 6‐13 6‐4 Groundwater and Surface Water Results for PAHs .................................................................................... 6‐15 7‐1 Cumulative Risk Assessment .........................................................................................................................7‐2 7‐2 Risk Assessment of Petroleum Hydrocarbons in Soil ....................................................................................7‐3 8‐1 Soil Ingestion Cleanup Levels .........................................................................................................................8‐2 8‐2 Soil Inhalation Cleanup Levels .......................................................................................................................8‐2 8‐3 Modeled Contaminated Soil Impacts to Groundwater .................................................................................8‐3

Figures

2‐1 Nunapitchuk Location Map ...........................................................................................................................2‐3 2‐2 Site Features and Historical Sample Locations ..............................................................................................2‐5 4‐1 Conceptual Site Model...................................................................................................................................4‐5 4‐2 Conceptual Exposure Model ..........................................................................................................................4‐7 5‐1 Soil, Groundwater and Surface Water Sample Locations ..............................................................................5‐3 6‐1 Soil Sampling Results .....................................................................................................................................6‐7 6‐2 Groundwater and Surface Water Sampling Results ................................................................................... 6‐11 8‐1 Proposed Area of Soil Excavation ..................................................................................................................8‐5

ANC/123540002/ES012512133903ANC V

Acronyms and Abbreviations °F degrees Fahrenheit

AAC Alaska Administrative Code

ACL alternate cleanup level

ADEC Alaska Department of Environmental Conservation

ADNR Alaska Department of Natural Resources

ARNG Army National Guard

AST aboveground storage tank

ASTM ASTM International bgs below ground surface

BTEX benzene, toluene, ethylbenzene, and xylenes

Clearwater Clearwater Environmental, Inc.

CSM conceptual site model

DGI data gap investigation

DQO data quality objective

DRO diesel-range organics

EHS-Alaska Environmental Health Sciences–Alaska, Inc.

EPA U.S. Environmental Protection Agency

EPH extractable aliphatic and aromatic petroleum hydrocarbons

ERM ERM-West, Inc.

FSRC Federal Scout Readiness Center

GRO gasoline-range organics

Hart Crowser Hart Crowser, Inc.

HI hazard index

Hoefler Hoefler Consulting Group

HRC hydrocarbon risk calculator

IC institutional control

IRA interim remedial action mg/kg milligrams per kilogram

NAPL nonaqueous-phase liquid

PA preliminary assessment

PAH polynuclear aromatic hydrocarbon

PID photoionization detector

RI remedial investigation

ACRONYMS AND ABBREVIATIONS

VI ANC/123540002/ES012512133903ANC

RRO residual-range organics

SA site assessment

SL screening level

TAH total aromatic hydrocarbon

TAqH total aqueous hydrocarbon

UFP-QAPP Unified Federal Program-Quality Assurance Project Plan

USGS U.S. Geological Survey

VPH volatile aliphatic and aromatic petroleum hydrocarbons yd3 cubic yards

ANC/123540002/ES012512133903ANC 1-1

SECTION 1

Introduction This data gap investigation (DGI) report provides background information, summarizes previous investigations, describes the updated conceptual site model (CSM), and provides the results of the recently completed field investigation at Nunapitchuk Federal Scout Readiness Center (FSRC). The report includes recommendations for further remedial actions.

This work was conducted under National Guard Bureau Contract W90FYQ-09-D-003, Task Order 2Z01.

1.1 Goals and Objectives of Data Gap Investigation

The goal of this DGI was to ensure that the Alaska Army National Guard (ARNG) has all the environmental data necessary to conduct remedial actions at Nunapitchuk FSRC to allow divestiture of the leased property without the use of institutional controls (ICs).

To fulfill this goal, the following primary project objectives of the DGI at Nunapitchuk FSRC were established:

• Ensure that adequate data are available to delineate the extent of petroleum-contaminated soil and groundwater related to previous heating oil spills and releases at Nunapitchuk FSRC in accordance with Title 18, Chapter 75, Section 335, of the Alaska Administrative Code (18 AAC 75.335), which requires that before proceeding with site cleanup under the site cleanup rules, a responsible person characterize the extent of hazardous substance contamination at the site including:

− Identifying each (potential) hazardous substance at the site, including the concentration and extent of contamination; this information must be sufficient to determine cleanup options without ICs.

− Evaluating the potential threat to human health, safety, and welfare, as well as to the environment, from site contamination.

− Locating sources of known site contamination, including a description of potential releases into soil, sediment, groundwater, or surface water.

− Evaluating the size of the contaminated area, including the concentrations and extent of any soil, sediment, groundwater, or surface water contamination.

− Identifying the vertical depth to groundwater and the horizontal distance to nearby wells, surface water, and water supply intakes.

− Evaluating the potential for surface water runoff from the site and the potential for surface water or sediment contamination.

− Identifying the soil type and determining whether the soil is a continuing source of groundwater contamination.

• Evaluate the possibility of establishing alternative cleanup levels (ACLs) for soil.

• Identify appropriate remedial alternatives.

1.2 Report Organization

The findings resulting from site activities are provided in the following sections:

• Section 1–Introduction. The introduction presents an overview of the DGI, including goals and objectives and report organization.

• Section 2–Site Background. The regional setting and site background information is presented in this section.

1 INTRODUCTION

1-2 ANC/123540002/ES012512133903ANC

• Section 3–Previous Investigations and Remedial Actions. This section summarizes information from previous preliminary assessments (PAs), site investigations, and remedial actions conducted at Nunapitchuk FSRC.

• Section 4–Data Gap Analysis. This section summarizes project screening levels (SLs), data quality objectives (DQOs), identified data gaps, and the CSM.

• Section 5–Field Activities. This section describes and summarizes methods and procedures used to investigate the affected soil for Nunapitchuk FSRC.

• Section 6–Contamination Assessment. This section assesses the extent of contamination across the site for all affected media utilizing historical and recently obtained data.

• Section 7–Cumulative Risk Assessment. Analytical results are analyzed to establish the potential risk to humans and the environment associated with the existing site contamination.

• Section 8–Recommendations. This section presents conclusions derived from the investigation data, presents proposed ACLs, and estimates the volume of contaminated soil that will require remedial action.

• Section 9–References. This section lists sources referenced in the text.

ANC/123540002/ES012512133903ANC 2-1

PHOTOGRAPH 1

Boardwalks providing access throughout the City of Nunapitchuk, including the FSRC

SECTION 2

Site Background This section summarizes the site location, climate, characteristics, and history of Nunapitchuk FSRC.

2.1 Site Location and Climate

The City of Nunapitchuk is located on the eastern bank of the Johnson River, in the Yukon‐Kuskokwim Delta approximately 22 miles northwest of Bethel. It lies at approximate latitude 60.8945147 degrees north and longitude 162.459482 degrees west, based on the 1984 (revised 2004) World Geodetic System (WGS 84) datum, and in Section 05 of Township 09 North, Range 074, West of the Seward Meridian within the Bethel Recording District (Figure 2‐1). The FSRC is located within the Nunapitchuk city limits, approximately 600 feet south of the village school.

The climate in Nunapitchuk is maritime, with continental influences in the winter. Precipitation falls 300 days of the year; average annual total precipitation is 14 inches, including 80 inches of snowfall (Alaska Department of Commerce, Community, and Economic Development, Division of Community and Regional Affairs, 2012). Average summer temperatures range from 34 degrees Fahrenheit (°F) to 48°F, and winter temperatures average 2°F to

10°F. Extreme temperatures have been recorded ranging from 30 to 65°F. The nearest weather station is in Bethel, where the average annual wind speed has been recorded as 11.3 miles per hour (Western Regional Climate Center, 2012).

2.2 Site Characteristics

Nunapitchuk is located in the Kuskokwim River drainage of the Yukon‐Kuskokwim Coastal Lowland Province, a marshy plain rising from sea level near the coast to a maximum elevation of 300 feet near the eastern boundary of the province.

The area surrounding Nunapitchuk is underlain by sand and silt to an undetermined depth. The surficial deposits are primarily floodplain alluvium consisting of mud, silt, and bog deposits.

Soils in the area are very poorly drained peat soils that are generally acidic in nature; the soils support a dense growth of mosses, lichens, and sedges. The area east of the site consists of wet tundra, with many low‐lying areas containing standing water. Because of wet conditions, boardwalks provide access to the FSRC and other village structures (Photograph 1).

According to a 1970 U.S. Geological Survey (USGS) report, permafrost in the Nunapitchuk area is discontinuous and varies by location (USGS, 1970). However, the results of work conducted at the FSRC in 1994, 1998, 2000, and 2007 (studies identified in Section 3) support the conclusion that continuous permafrost is present beneath the site.

2.2.1 Surface Water

The FSRC is situated at the edge of a relict river terrace, about 20 feet above the level of the Johnson River. The riverbank is located about 500 feet to the west of the FSRC. Surface water is common in the Nunapitchuk area, with wetlands characterized by numerous shallow thaw lakes and ponds or lakes created by meandering streams.

Because of the relatively flat terrain, drainages are virtually indistinguishable from the surrounding terrain, except where soil cover has been disturbed and local permafrost has retreated deeper, resulting in a deepening of the surface water drainage. When this occurs, these local drainages can become significant pathways for surface

2 SITE BACKGROUND

2-2 ANC/123540002/ES012512133903ANC

PHOTOGRAPH 2

Standing surface water (very wet tundra, typical) to the west of the FSRC in June 2011

PHOTOGRAPH 3

New FSRC, 3,000‐gallon AST, and storage van are visible.

Looking west.

water and contaminant migration. Local surface water drainages in the village are very short (less than 1,000 feet) and flow either to the Johnson River or to local thaw lakes.

Surface drainage from the FSRC is generally in a west‐to‐ southwest direction toward the river. Historically, standing surface water has been observed surrounding most of the New FSRC building (Photograph 2).

2.2.2 Hydrogeology

Information from the available well logs for the area shows a minimum of 250 feet of permafrost separating shallow groundwater on top of the permafrost (suprapermafrost groundwater) from the confined aquifer used for drinking water (Alaska Department of Natural Resources [ADNR], 2012).

A deep, confined aquifer occurring at approximately 230 feet below ground surface (bgs) provides drinking water for the City of Nunapitchuk. The city well is 273 feet deep, with the well screen set below 259 feet of permafrost (ADNR, 2012). No other wells, private or public, are known to exist in Nunapitchuk.

Except for the seasonally perched water found in the shallow subsurface soils above the permafrost table in the summer (active zone), groundwater generally does not exist in the Kuskokwim Lowlands above the permafrost table.

2.3 Site Description and History

Nunapitchuk FSRC is an inoperable scout readiness center.

Buildings and equipment remaining at Nunapitchuk FSRC (Photograph 3 and Figure 2‐2) are:

A 30‐ by 40‐foot, Butler‐style, prefabricated building on a spread footing foundation was constructed in 1988 (New FSRC). This building was moved approximately 35 feet to the northeast from its originally constructed location in 2006 (Hoefler Consulting Group [Hoefler], 2007).

A boardwalk is on the western, northern, and eastern sides of the New FSRC.

A 3,000‐gallon, double‐walled heating oil aboveground storage tank (AST) was installed in 1989. The AST, located to the northwest of the New FSRC, is plumbed with feed‐and‐return pipelines into a 10‐gallon day tank within the building. The AST is welded onto steel skids, which lie on wood beams over blue foam insulation.

A storage van was originally located northwest of the New FSRC. The storage van was moved after 2005 and now lies approximately 15 feet north of the New FSRC’s repositioned location.

Abandoned or removed buildings and equipment relevant to this FSRC are:

A 20‐ by 60‐foot, Butler‐style prefabricated building constructed in 1960 on a spread footing foundation (the Old FSRC), which was removed after 2005.

The boardwalk connecting to the former raised walkway between the New and Old FSRC buildings, which is no longer present and likely was removed after 2005.

CH2MHILL

FIGURE 2-1

Nunapitchuk Location Map Data Gap Investigation Report Army National Guard FSRCs, Alaska

Vicinity Map A R C T I C O C E A N

B E R I N

G S E

A

North Approximate scale in feet

5502750

ES110310215028ANC 403507 ArNG_FSRC_LocMap_Nunapitchuk_03.ai 09/23/11 cts

Nunapitchuk Federal Scout Readiness Center

Jo hnso n R iv er

Bethel

Nome

Anchorage

Alakanuk

Tununak

Kipnuk

Tuntutuliak

NapaskiakEek Kwethluk

Napakiak

Nightmute

Stebbins

Akiak

Emmonak

Gambell Savoonga

Kotlik

Toksook Bay

Kasigluk

Nunapitchuk

St. Mary's Mountain Village

Nunapitchuk

2-4 ANC/123540002/ES012512133903ANC

\\BALDUR\PROJ\USANG_410956\GIS\MAPFILES\NUNAPITCHUK\FIG_2-2_NUNAPITCHUK_SAMPLELOCS_HISTORICAL.MXD TWONG2 3/20/2012 2:34:20 PM

VICINITY MAP

3,000-gallon

AST

Former 3,000-gallon AST

Former 3,000-gallon AST

Storage Van

Former Location of Storage Van

Former Day Tank

Day Tank

Former Day Tank

Former Location of New FSRC

Former Location of Old FSRC

New Federal Scout Readiness

Center (FSRC)

Metal R amp

Boardwalk

Boardwalk Boardwalk

Former 3,000-gallon ASTNUN005

NB-03

NUNG2

NUN002

NUNH3

NB-07

NB-08

NB-09

NB-01

NB-02 NB-04

NB-05

NB-10

NB-11

NB-12

NB-14

NB-15

NUN-ACL-01

NUN-ACL-02

NUN-ACL-03

NUN-ACL-04

NUN-ACL-06

NUN-ACL-07

NUN-ACL-08

NUN-ACL-09

NUN-ACL-10

NUN-ACL-11

NUN-ACL-12

TB-10

TB-11

TB-16

TB-4

TB-9

NUN001

NUN003

NUN004

NUN006

NUN007

NUNA8

NUNB1

NUNB12

NUNB2

NUNB3

NUNB8NUNC7

NUNC9

NUND-2

NUND1

NUND8

NUNE0

NUNE13

NUNF0

NUNF2

NUNG1

NUNG14

NUNG4

NUNH13

NUNH5

NUNH7

NUNI10

NUNJ3

0 157.5

Feet

LEGEND

Federal Scout Readiness Center (FSRC)

Storage Van

AST

Day Tank

Former Feature

2005 ACL Representation of 2001 IRA Excavation

Excavation 2001 IRA

Historical Sample Location

Mountain Village

Savoonga Gambell

Saint Mary's

Alakanuk Emmonak

Stebbins Kotlik

Eek

Tununak Nightmute

Kipnuk

Kwethluk Akiak

NunapitchukKasigluk

Tuntutuliak

Toksook Bay Napakiak

Napaskiak

A L A S K A

Notes:

1. Location of historical samples is approximate based on historical figures and on orthophotography courtesy of Alaska Department of Commerce, Division of Community & Regional Affairs (DCRA), 1-foot pixels.

2. Location of excavation is approximate based on historical figures.

3. Definition:

AST = aboveground storage tank

FIGURE 2-2

Site Features and Historical Sample Locations Nunapitchuk FSRC Data Gap Investigation Nunapitchuk, Alaska

ANC/123540002/ES012512133903ANC 2-7

• A former 3,000-gallon, single-walled AST, which was removed in 1989 and had been located near the northern corner of the Old FSRC; supply lines connected the AST to a day tank.

• A former 3,000-gallon, double-walled heating oil AST, which was installed at the northern corner of the Old FSRC in 1989. Feed-and-return pipelines plumbed the AST into a 10-gallon day tank within the building. The AST was welded onto steel skids that rested directly on the ground. This AST either has been removed or has been relocated to the current location of the 3,000-gallon AST that is labeled in Figure 2-2.

• A former 3,000-gallon, double-walled heating oil AST, which was installed at the western corner of the New FSRC in 1989. Feed-and-return pipelines plumbed the AST into a 10-gallon day tank within the building. The AST was welded onto steel skids that rested directly on the ground. This AST either has been removed or has been relocated to the current location of the 3,000-gallon AST labeled in Figure 2-2.

• A former pipeline from a tank farm that entered the property from the north and filled the former 3,000-gallon AST.

2-8 ANC/123540002/ES012512133903ANC

ANC/123540002/ES012512133903ANC 3-1

SECTION 3

Previous Investigations and Remedial Actions This section briefly discusses known spills, previous investigations, and the results of each investigation at Nunapitchuk FSRC. SLs discussed in this section are based on those used at the time of each investigation unless otherwise noted. Figure 2-2 presents historical sample locations and known site features at Nunapitchuk FSRC.

A 1992 compliance inspection conducted by ARNG noted two fuel releases at Nunapitchuk FSRC, although the quantity of fuel released and the extent of contamination are unknown.

A 200- to 300-gallon release of heating oil from the piping of the AST next to the Old FSRC occurred in January 1993. The spill reportedly resulted from a faulty fitting along the feed line between the tank and the building. ARNG personnel initially responded by constructing a snow trench and placing a boom along the spill boundary. The cleanup effort was continued by filling drums with the fuel-contaminated snow; ultimately, approximately 100 gallons of the release was recovered. Lab analysis of soil samples collected near the tank indicated the presence of diesel-range organics (DRO) at concentrations up to 295,000 milligrams per kilogram (mg/kg).

An additional 80- to 150-gallon heating oil spill from the same AST occurred during the winter of 1996/1997 and was reported in June 1997. An estimated 200- to 300-square-foot area was contaminated (ERM-West, Inc. [ERM] and Hart Crowser, Inc. [Hart Crowser], 1998); however, the location and extent of the release are unknown.

The following environmental investigations have been conducted at Nunapitchuk FRSC:

• Site assessment (SA) conducted by Environmental Health Sciences–Alaska, Inc. (EHS-Alaska) in 1994 (EHS-Alaska, 1995)

• PA and remedial investigation (RI) conducted by ERM and Hart Crowser in 1997 (ERM/Hart Crowser, 1998)

• Interim remedial action (IRA) conducted by Clearwater Environmental, Inc. (Clearwater) in 2000 (Clearwater, 2001)

• Alternate cleanup level (ACL) demonstration conducted by Hoefler in 2003 (Hoefler, 2005)

• Compliance cleanup site characterization conducted by Hoefler in 2007 (Hoefler, 2007)

3.1 1994 Site Assessment EHS-Alaska conducted an SA in September 1994, during which 18 hand-auger borings were advanced in the area of the fuel spill (EHS-Alaska, 1995). Subsurface refusal occurred when permafrost was encountered at approximately 2.5 feet bgs. A surface soil sample was collected from each boring, and subsurface soil samples were collected at 1-foot intervals. Soil samples were analyzed for DRO using Alaska Method AK102 and for benzene, toluene, ethylbenzene, and total xylenes (BTEX) using U.S. Environmental Protection Agency (EPA) Method SW8020. Alaska Department of Environmental Conservation (ADEC) Method 1, Matrix Level D, cleanup levels were calculated for the site, providing a 2,000-mg/kg cleanup level for DRO. Soil samples from three locations exceeded DRO cleanup levels, with the highest DRO concentration reported at 51,000 mg/kg.

EHS-Alaska estimated that 12 to 25 cubic yards (yd3) of soil exceeded the Matrix Level D cleanup levels for DRO.

3.2 1997 Preliminary Assessment and Remedial Investigation ERM and its subconsultant, Hart Crowser, conducted a PA in 1997 and an RI in late September 1997 for the site (ERM/Hart Crowser, 1998). Soil samples collected from 16 borings were analyzed for DRO (Alaska Method AK102), gasoline-range organics (GRO) (Alaska Method AK101), residual-range organics (RRO) (Alaska Method AK103), and BTEX (EPA Method SW8020). One well point was installed, from which a sample of the suprapermafrost

3 PREVIOUS INVESTIGATIONS AND REMEDIAL ACTIONS

3-2 ANC/123540002/ES012512133903ANC

groundwater was collected and analyzed for DRO (Alaska Method AK102), GRO (Alaska Method AK101), and BTEX (EPA Method SW8020).

Biogenic interference was reported to contribute significantly to the observed high DRO levels (ranging from 210 to 160,000 mg/kg) in the soil samples. Based on laboratory review of all soil sample chromatograms, only 8 of the 34 soil samples analyzed were reported to contain petroleum distillates. The sample of suprapermafrost groundwater did not contain measurable amounts of petroleum hydrocarbons. It was estimated that 60 to 120 yd3 of DRO-contaminated soil exceeded the 12,500-mg/kg cleanup level established during the RI (ERM/Hart Crowser, 1998).

3.3 2000 Interim Remedial Action Clearwater performed an IRA during April 2000, the objective of which was to remove petroleum-contaminated soils resulting from heating oil spills from the AST (Clearwater, 2001). A total of 10 yd3 of DRO-contaminated soil from two areas was removed and sent to an offsite thermal treatment facility. Eight confirmation soil samples were collected from the excavation floor and sidewalls for the purpose of defining the conditions at the perimeter of the excavations. Samples were analyzed for DRO using Alaska Method AK102, for GRO using Alaska Method AK101, and for BTEX using EPA Method SW8021B. Four confirmation soil samples (NUN003, NUN005, NUN006, and NUN007) contained DRO at concentrations in excess of 2,000 mg/kg.

3.4 2003 Alternate Cleanup Level Demonstration Hoefler conducted a demonstration project in October 2003 to determine an ACL for petroleum contamination at Nunapitchuk FSRC (Hoefler, 2005). The ACL project consisted of collecting 13 soil samples (including 1 field duplicate) and 4 suprapermafrost groundwater samples (including 1 field duplicate). All samples were analyzed for DRO (Alaska Method AK102), GRO (Alaska Method AK101), RRO (Alaska Method AK103), and BTEX (EPA Method SW8021B). DRO was detected at a maximum concentration of 54,200 mg/kg, in a soil sample collected between the Old FSRC and the double-walled AST. This investigation did not include sampling beneath the armory. Hoefler noted that the DRO analyses were all biased high because of biogenic sources contributing to the organic compounds in the soil, with background concentrations of DRO ranging from 173 mg/kg to more than 1,000 mg/kg. Based on the proposed cleanup levels, an estimated additional 25 yd3 of soil would need to be removed to bring the site into compliance.

DRO and RRO were detected in the suprapermafrost groundwater near the northeastern corner of the Old FSRC at concentrations greater than cleanup levels.

3.5 2007 Compliance Cleanup Site Characterization In 2007, fifty-four soil borings were installed and sampled by Hoefler at Nunapitchuk FSRC as part of the attempt to delineate the extent and volume of petroleum contamination in soil by DRO at concentrations exceeding 250 mg/kg (Hoefler, 2007). Soil borings were completed on a grid with a 5-foot node spacing where surface water was not present. The sampling was focused around the area of the previous excavation. A total of 106 soil samples were collected and field screened to evaluate the presence or absence of hydrocarbons in the soil.

Twenty-five soil samples were selected for laboratory analysis of DRO by Alaska Method AK102. Sampling was biased to identify areas where DRO concentrations in the soil would be low and would not be contaminated by hydrocarbon releases. Field screening data and analytical results were compared, and an attempt was made to develop a qualitative correlation. However, site conditions such as floating muskeg, little mineral soil, abundant surface water, and soil samples containing high percentages of organic material introduced variables that caused uncertainty in this correlation. DRO concentrations were detected in all 25 soil samples submitted for analysis;

concentrations ranged from 133 mg/kg to a maximum of 34,200 mg/kg (sample located below the northwestern corner of the New FSRC).

ANC/123540002/ES012512133903ANC 4-1

SECTION 4

Data Gap Analysis This section summarizes how SLs and DQOs were established for the DGI and how previous investigation data were used, and presents the CSM of site conditions and the means of potential exposure at Nunapitchuk FSRC.

This section also presents the data gaps identified for Nunapitchuk FSRC that were examined as part of the DGI.

4.1 Project Screening Levels

SLs are conservative, predominantly risk-based values used to characterize and determine the nature and extent of contamination in soil and groundwater. SLs are intended to be used for screening purposes only; exceedance of an SL is not necessarily an indication of unacceptable risk. Details about the SL selection process for each medium are provided in the Unified Federal Program-Quality Assurance Project Plan (UFP-QAPP) published as Final Work Plan for Site Characterization at 21 Alaska Federal Scout Readiness Centers (CH2M HILL, 2011).

4.1.1 Soil Screening Levels

Soil SLs are established in consideration of cumulative exposure of human receptors to contaminants in soil (and sediment) through direct contact and outdoor inhalation, as well as protection of groundwater. The project SLs established for Nunapitchuk FSRC were based on ADEC cleanup levels provided in 18 AAC 75.

As presented in 18 AAC 75.340(a)(2), proposed soil cleanup levels for a site must be based on an estimate of the reasonable maximum exposure expected to occur under current and future site conditions. Soil SLs must be developed using ADEC Method 2 for soil contaminated with chemicals other than petroleum hydrocarbons, as set out in Table B1 of 18 AAC 75.341(c), and for soil contaminated with petroleum hydrocarbons, as set out in Table B2 of 18 AAC 75.341(d). The ADEC Method 2 cleanup levels presented in Tables B1 and B2 were determined for three potential exposure pathways—direct contact/

The project SLs are shown in Table 4-1. The project SLs for GRO and DRO in soil were set equal to the ADEC Method 2 cleanup levels for the migration-to-groundwater pathway; for RRO in soil, the SL was set equal to the ADEC Method 2 cleanup level for the ingestion pathway. For chemicals other than petroleum hydrocarbons, to account for possible cumulative risk associated with multiple chemical exposures, direct contact, and outdoor inhalation, cleanup levels were divided by a factor of 10. The SL for a specific chemical in soil was determined to be the lowest of the adjusted ADEC Method 2 direct contact or outdoor inhalation cleanup level and the ADEC Method 2 migration-to-groundwater cleanup level. Because of the extensive list of possible contaminants, only SLs for BTEX compounds are shown in Table 4-1.

ingestion, inhalation, and migration to groundwater— depending on the climatic zone in which the soil is located (arctic zone, under-40-inch zone, or over-40-inch zone).

The cleanup level from Table B1 or B2 that applies to Nunapitchuk FSRC is based on the exposure pathway with the most stringent value calculated for a site within the under-40-inch climatic zone. Based on available data, all three exposure pathways were considered potentially complete for Nunapitchuk FSRC.

4.1.2 Groundwater Screening Levels

Groundwater SLs are established in consideration of potential cumulative exposure of human receptors to contaminants through drinking of groundwater. As defined in 18 AAC 75.345(b)(1), contaminated groundwater must meet the cleanup levels in Table C of 18 AAC 75.345(b)(1) if the current use or the reasonably expected potential use of the groundwater, determined under 18 AAC 75.350, is a drinking water source. In addition, 18 AAC 75.345(g) states that groundwater that is closely connected hydrologically to nearby surface water may not cause a violation of the water quality standards in 18 AAC 70 for surface water.

4 DATA GAP ANALYSIS

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TABLE 4-1

Soil Screening Levels Nunapitchuk Federal Scout Readiness Center Data Gap Investigation

Contaminant of Concern

ADEC Method 2 Cleanup Level Exposure Route of Primary Concern

Proposed ADEC Method 2 Soil Cleanup Level

Project Screening

Level Direct Contact/ Outdoor

Inhalation Ingestion Migration to Groundwater

Gasoline-range organics 1,400 1,400 300 Migration to GW 300 300

Diesel-range organics 10,250 12,500 250 Migration to GW 250 250

Residual-range organics 10,000 22,000 11,000 Ingestion 10,000 10,000

Benzene 150 11 0.025 Migration to GW 0.025 0.025

Toluene 8,100 220 6.5 Migration to GW 6.5 6.5

Ethylbenzene 10,100 110 6.9 Migration to GW 6.9 6.9

Xylenes (total) 20,300 63 63 Inhalation 63 6.3

Note: All values are in milligrams per kilogram.

ADEC = Alaska Department of Environmental Conservation GW = groundwater Source: 18 AAC 75.341, Tables B1 and B2, under-40-inch zone

For DRO, GRO, and RRO, the project SLs were set equal to the cleanup levels in Table C of 18 AAC 75.345(b)(1). For all other compounds, SLs were derived by dividing the cleanup levels in Table C by a factor of 10 to account for possible cumulative risk associated with multiple chemical exposures. Table 4-2 summarizes the project SLs for GRO, DRO, RRO, and BTEX compounds only at Nunapitchuk FSRC.

TABLE 4-2

Groundwater Screening Levels Nunapitchuk Federal Scout Readiness Center Data Gap Investigation

Contaminant of Concern

18 AAC 75 Groundwater Cleanup Level

(mg/L)

18 AAC 70 Water Supply, Aquiculture, Cleanup Level

(µg/L) Project Screening Level

(mg/L)

Gasoline-range organics 2.2 -- 2.2

Diesel-range organics 1.5 -- 1.5

Residual-range organics 1.1 -- 1.1

Benzene 0.005 -- 0.0005

Toluene 1.0 -- 0.1

Ethylbenzene 0.7 -- 0.07

Xylenes (total) 10 -- 1.0

Total aromatic hydrocarbons -- 10 --

Total aqueous hydrocarbons -- 15 --µg/L = micrograms per liter AAC = Alaska Administrative Code mg/L = milligrams per liter -- = not analyzed Source: 18 AAC 75.345, Table C, and 18 AAC 70.020(b)(5)(A)(iii)

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4.2 Data Quality Objectives

DQOs were established to provide benchmarks against which the quality of fieldwork and the quality of the resulting analytical data could be evaluated. The DQOs specified the type, quality, quantity, and uses of the data needed to adequately support environmental decisions at Nunapitchuk FSRC. The DQOs could be fulfilled by using either existing data or data to be gathered during the 2011 DGI. To help meet this objective, historical (previous investigation) data were evaluated for usability following the general procedures outlined in the UFP-QAPP (CH2M HILL, 2011). Three DQOs were established for the 2011 DGI for Nunapitchuk FSRC. The DQOs established the type and quantity of data necessary for determining the nature and extent of contamination in soil and groundwater at the FSRC and specified the quality and quantity of data required to assess cumulative human health risk.

• DQO 1 established what data were necessary to determine whether further sampling of the soil would be required to define the nature and extent of contamination (and, secondarily, to support a remedial decision and cost savings for future remedial actions). The lateral extent of soil contamination would be adequately delineated only if all soil samples surrounding the potential source or release location contained concentrations of all target analytes below SLs. To help meet this objective, historical (previous investigation) data were evaluated for usability following the general procedures outlined in the UFP-QAPP (CH2M HILL, 2011). Data that (1) had been properly validated, (2) had been derived through use of ADEC-approved or EPA-approved analytical methods, and (3) reflected analytical detections greater than the limits of detection or less than the SLs were considered usable for the purposes of determining the extent of contamination.

Those data that were considered usable were also retained to characterize the site. For Nunapitchuk FSRC, data that were collected prior to the excavation and were collected within the limits of the excavation are not considered usable data because they were not representative of current site conditions.

• DQO 2 established the type and quantity of data that were necessary to determine whether suprapermafrost groundwater was present, contaminated, and acting as a transport mechanism to nearby surface water bodies. The lateral extent of DRO contamination present in suprapermafrost groundwater and surface water at concentrations greater than the SL had not been adequately delineated at the site. Consequently, additional suprapermafrost groundwater data were needed to adequately characterize the extent of DRO contamination. Possible contamination of surface water bodies present within the site had not been assessed; therefore, surface water samples were necessary to determine the presence (or absence) of DRO in surface water as a result of releases from Nunapitchuk FSRC.

• DQO 3 was established to determine the type and quantity of data required to ascertain whether current or hypothetical residents, occupational workers, or construction/excavation workers might be exposed to constituent contaminant concentrations that could pose potentially unacceptable risks. Historical (previous investigation) data were also evaluated for usability, and those data that were considered usable were retained for use in risk assessment.

4.3 Conceptual Site Model

A CSM integrates (1) existing information and working assumptions about the physical site conditions; (2) the nature, occurrence, and distribution of chemicals; and (3) fate and transport processes. The CSM for Nunapitchuk FSRC is based on the current understanding of site history and conditions and integrates information about leaks and spills of heating oil from the former AST near the northern corner of the Old FSRC (Figure 4-1).

As a pure product, heating oil is less dense than water and is referred to as light nonaqueous-phase liquid (NAPL).

When released to the ground surface, NAPL products spread laterally across the ground surface and infiltrate into the soil. The extent of lateral spreading across the ground surface is a function of quantity and rate of release and the permeability of the surface soil. The infiltrating product from a surface spill tends to flow primarily vertically under the influence of gravity through larger air-filled soil pores, although capillary forces may cause some lateral spreading. When released in sufficient quantities, NAPL product can migrate downward through soil and

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accumulate at the capillary fringe of the groundwater table surface. When the soluble portion of heating oil dissolves in groundwater, the specific gravity of the aqueous plume is nearly the same as that of uncontaminated groundwater, and the plume moves with the groundwater flow. The insoluble portion of heating oil typically is absorbed by the soil particles or becomes disconnected globules in the soil pore spaces. Because the known spills at Nunapitchuk FSRC are at least a decade old, it is very likely that gravity drainage and flow of the NAPL product to a point of immobility have already occurred.

Of the various pathways considered, incidental human ingestion of surface soil and dermal contact with the soil were the two primary exposure routes. Figure 4-2 provides an illustration of the conceptual exposure model.

Dermal contact with surface water is considered to be a potential exposure pathway. Extensive human dermal contact with surface water is not likely because, for the most part, wooden walkways are used to avoid human contact with surface water features. Ingestion of surface water or aquatic organisms affected by contamination is possible but unlikely. Because of the relatively flat topography and the wet, marshy conditions, substantial drainage channel flow is not expected. Because of the slow and dispersive nature of drainage, it is unlikely that contaminant concentrations would reach the Johnson River (which would cause exceedances of surface water quality standards).

Nunapitchuk is prone to flooding. While exposure to floodwaters contaminated from contact with contaminated soil is a potentially complete pathway, the amount of exposure to the contaminated floodwater is considered insignificant. Nunapitchuk is subject to flooding roughly once every 10 to 20 years lasting between 1 to 7 days. If a flood were to occur in the spring, it would be the result of an ice jam on the river, and it is very likely that the ground would be solidly frozen, eliminating the possibility of downward migration of surface water. If the flood happens in the fall, it’s likely caused by a heavy rain event locally or up river and the rise in the river will be quick and dramatic (groundwater table will not have time to rise up to the ground surface, so downward migration is the only means of interaction, not upwards). If surface water does become exposed to contaminated soil and reaches equilibrium with the contamination, the surface water would be undergoing substantial movement during the flood event and there would be an immense amount of mixing (dilution) occurring. The concentration levels within the surface water would be insignificant.

Groundwater is not considered a primary pathway because a minimum of 227 feet of permafrost separates the contamination from the confined aquifer used for drinking water. All of the potentially complete ecological exposure pathways are considered insignificant because of the small size of the site and the presence of more optimal habitat nearby.

4.4 Identification of Data Gaps

Historical site use and previous investigation findings suggest that the primary source of contamination at Nunapitchuk FSRC is associated with spills and leaks from former heating oil ASTs. Data collected during previous investigations and subsequent to the IRA indicated the presence of DRO in soil down to permafrost near the former AST located near the northern corner of the Old FSRC.

Groundwater at the site is water that rests on top of a seasonally active zone of permafrost (suprapermafrost groundwater) that is laterally continuous across the site. The reported RRO and DRO concentrations in the suprapermafrost groundwater were above SLs.

Leak from AST above spilled hydrocarbon mass is sufficient to reach permafrost and mixes with supra-permafrost groundwater.

NAPL Contaminated Soil Source Area

Supra-Permafrost Groundwater

Frozen Soil

CH2MHILL

FIGURE 4-1

Conceptual Site Model Nunapitchuk FSRC Data Gap Investigation Report

403507 ES012512133903ANC_ArNG_Nunapitchuk_ConceptualSiteModel_01.ai 03/28/12 cts

Discharge

Direct contact by receptors

= Potentially complete pathway (to be addressed quantitatively) = Pathway…