FINAL 

Site Inspection Report 

Barrigada Army Aviation Operations Facility 

Barrigada, Guam 

Site Inspections for Perfluorooctanoic Acid (PFOA), Perfluorooctanesulfonic Acid (PFOS), 

Perfluorohexanesulfonic Acid (PFHxS), Perfluorononanoic Acid (PFNA), Hexafluoropropylene 

oxide dimer Acid (HFPO-DA) and Perfluorobutanesulfonic Acid (PFBS) 

ARNG Installations, Nationwide

November 2023 

Prepared for: 

Army National Guard Headquarters 

111 S. George Mason Drive 

Arlington, VA 22204 

UNCLASSIFIED
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TABLE OF CONTENTS

Page

LIST OF APPENDICES ................................................................................................................ iii

LIST OF FIGURES ....................................................................................................................... iv

LIST OF TABLES .......................................................................................................................... v

LIST OF ACRONYMS AND ABBREVIATIONS ...................................................................... vi

EXECUTIVE SUMMARY ...................................................................................................... ES-1

1. INTRODUCTION ............................................................................................... 1-1

1.1 PROJECT AUTHORIZATION ............................................................... 1-1

1.2 SITE INSPECTION PURPOSE .............................................................. 1-1

2. FACILITY BACKGROUND .............................................................................. 2-1

2.1 FACILITY LOCATION AND DESCRIPTION ..................................... 2-1

2.2 FACILITY ENVIRONMENTAL SETTING .......................................... 2-1

2.2.1 Geology ..................................................................................... 2-1

2.2.2 Hydrogeology ........................................................................... 2-2

2.2.3 Hydrology ................................................................................. 2-3

2.2.4 Climate ...................................................................................... 2-3

2.2.5 Current and Future Land Use .................................................... 2-3

2.2.6 Sensitive Habitat and Threatened/Endangered Species ............ 2-3

2.3 HISTORY OF PFAS USE ....................................................................... 2-4

3. SUMMARY OF AREAS OF INTEREST ........................................................... 3-1

3.1 AOI 1 – FIRE EXTINGUISHER MAINTENANCE AREA .................. 3-1

3.2 POTENTIAL ADJACENT SOURCES ................................................... 3-1

3.2.1 NBG Barrigada ......................................................................... 3-1

3.2.2 Guam Antonio B. Won Pat International Airport ..................... 3-2

4. PROJECT DATA QUALITY OBJECTIVES ..................................................... 4-1

4.1 PROBLEM STATEMENT ...................................................................... 4-1

4.2 INFORMATION INPUTS ....................................................................... 4-1

4.3 STUDY BOUNDARIES ......................................................................... 4-1

4.4 ANALYTICAL APPROACH ................................................................. 4-1

4.5 DATA USABILITY ASSESSMENT ...................................................... 4-2

5. SITE INSPECTION ACTIVITIES ...................................................................... 5-1
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5.1 PRE-INVESTIGATION ACTIVITIES ................................................... 5-2

5.1.1 Technical Project Planning ....................................................... 5-2

5.1.2 Utility Clearance ....................................................................... 5-2

5.1.3 Source Water and PFAS Sampling Equipment Acceptability .. 5-2

5.2 SOIL BORINGS AND SOIL SAMPLING ............................................. 5-3

5.3 SURVEYING .......................................................................................... 5-4

5.4 INVESTIGATION-DERIVED WASTE ................................................. 5-4

5.5 LABORATORY ANALYTICAL METHODS ....................................... 5-4

5.6 DEVIATIONS FROM SITE INVESTIGATION UFP-QAPP 

ADDENDUM .......................................................................................... 5-5

6. SITE INSPECTION RESULTS .......................................................................... 6-1

6.1 SCREENING LEVELS ........................................................................... 6-1

6.2 SOIL PHYSICOCHEMICAL ANALYSES ............................................ 6-2

6.3 AOI 1 ....................................................................................................... 6-2

6.3.1 AOI 1 − Soil Analytical Results ............................................... 6-2

6.3.2 AOI 1 - Conclusions ................................................................. 6-3

7. EXPOSURE PATHWAYS .................................................................................. 7-1

7.1 SOIL EXPOSURE PATHWAY .............................................................. 7-1

7.1.1 AOI 1 ........................................................................................ 7-1

7.2 GROUNDWATER EXPOSURE PATHWAY........................................ 7-2

7.2.1 AOI 1 ........................................................................................ 7-2

7.3 SURFACE WATER AND SEDIMENT PATHWAY ............................ 7-2

7.3.1 AOI 1 ........................................................................................ 7-3

8. SUMMARY AND OUTCOME .......................................................................... 8-1

8.1 SITE INSPECTION ACTIVITIES .......................................................... 8-1

8.2 OUTCOME .............................................................................................. 8-1

9. REFERENCES .................................................................................................... 9-1
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LIST OF APPENDICES

Appendix A. Data Usability Assessment and Data Validation Reports

Appendix B. Field Documentation

 B1. Log of Daily Notice of Field Activities

 B2. Sampling Forms 

 B3. Survey Data 

 B4. Investigation-Derived Waste Location 

Appendix C. Photographic Log 

Appendix D. Technical Project Planning Meeting Minutes

Appendix E. Boring Logs 

Appendix F. Analytical Results

Appendix G. Laboratory Reports
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LIST OF FIGURES

Figure 2-1. Facility Location

Figure 2-2. Topography 

Figure 2-3. Groundwater Features 

Figure 2-4. Surface Water Features

Figure 3-1. Area of Interest

Figure 5-1. Site Inspection Sample Locations

Figure 6-1. PFOS Detections in Soil 

Figure 6-2. PFOA Detections in Soil

Figure 6-3. PFBS Detections in Soil

Figure 6-4. PFHxS Detections in Soil

Figure 6-5. PFNA Detections in Soil

Figure 7-1. Conceptual Site Model, AOI 1
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LIST OF TABLES

Table ES-1. Screening Levels (Soil and Groundwater) 

Table ES-2. Summary of Site Inspection Findings and Recommendations 

Table 5-1. Site Inspection Samples by Medium, Barrigada AAOF, Guam, Site Inspection 

Report 

Table 5-2. Soil Boring Depths, Barrigada AAOF, Guam, Site Inspection Report

Table 6-1. Screening Levels (Soil and Groundwater) 

Table 6-2. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil, Site 

Inspection Report, Barrigada AAOF 

Table 6-3. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Shallow Subsurface Soil, 

Site Inspection Report, Barrigada AAOF

Table 6-4. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Deep Subsurface Soil, Site 

Inspection Report, Barrigada AAOF

Table 8-1. Summary of Site Inspection Findings and Recommendations 
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LIST OF ACRONYMS AND ABBREVIATIONS 

°C Degrees Celsius

°F Degrees Fahrenheit

% Percent

μg/kg Microgram(s) per kilogram

AAOF Army Aviation Operations Facility

AECOM AECOM Technical Services, Inc. 

AFFF Aqueous film-forming foam 

amsl Above mean sea level

AOI Area of interest

ARNG Army National Guard

ASTM American Society for Testing and Materials

bgs Below ground surface 

CAFS Compressed air foam system 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

COC Chain-of-custody 

CSM Conceptual site model

DoD Department of Defense

DQO Data quality objective 

DUA Data Usability Assessment

EA EA Engineering, Science, and Technology, Inc., PBC 

EB Equipment Blank 

EDRTM Environmental Data Resources Inc.TM 

EIS Extraction internal standard

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual 

FD Field duplicate 

FedEx Federal Express

ft Foot (feet)

GEPA Guam Environmental Protection Agency 

GUARNG Guam Army National Guard

HA Health advisory 

HDPE High-density polyethylene 

HFPO-DA Hexafluoropropylene oxide dimer acid 

HSA Hollow stem auger 

IDW Investigation-derived waste

ITRC Interstate Technology Regulatory Council 
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LIST OF ACRONYMS AND ABBREVIATIONS (continued)

LC/MS/MS Liquid chromatography tandem mass spectrometry

MIL-SPEC Military Specification

MS Matrix spike

MSD Matrix spike duplicate 

NA Not applicable 

NAVFAC Naval Facilities Engineering Command

NCTAMS Naval Computer and Telecommunications Area Master Station

NELAP National Environmental Laboratory Accreditation Program 

ng/L Nanogram(s) per liter

No. Number 

OSD Office of the Secretary of Defense

PA Preliminary Assessment

PFAS Per- and polyfluoroalkyl substances 

PFBS Perfluorobutanesulfonic acid

PFHxS Perfluorohexanesulfonic acid

PFNA Perfluorononanoic acid 

PFOA Perfluorooctanoic acid

PFOS Perfluorooctanesulfonic acid

PID Photoionization detector 

ppt Part(s) per trillion

QA Quality assurance

QAPP Quality Assurance Project Plan

QC Quality control 

QSM Quality Systems Manual 

RI Remedial investigation 

SB Soil boring

SI Site inspection

SL Screening level

TOC Total organic carbon 

TPP Technical Project Planning 

UFP Uniform Federal Policy 

USACE U.S. Army Corps of Engineers 

USEPA U.S. Environmental Protection Agency 
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EXECUTIVE SUMMARY

The Army National Guard (ARNG) G-9 is performing Preliminary Assessments (PAs) and Site 

Inspections (SIs) at ARNG facilities nationwide based on the current or potential historical use of 

per- and polyfluoroalkyl substances (PFAS) with a focus on the six compounds presented in the 

memorandum from the Office of the Secretary of Defense (OSD) (Assistant Secretary of 

Defense) dated 6 July 2022. The six compounds listed in the OSD memorandum include 

perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic 

acid (PFBS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), and 

hexafluoropropylene oxide dimer acid (HFPO-DA)1. These compounds are collectively referred 

to as “relevant compounds” throughout the document and the applicable screening levels (SLs) 

are provided in Table ES-1

The PA identified one Area of Interest (AOI) where PFAS-containing materials may have been

used, stored, disposed, or released historically (see Table ES-2 for AOI location). The objective 

of the SI is to identify whether there has been a release to the environment from the AOI 

identified in the PA and determine whether further investigation is warranted, a removal action is 

required to address immediate threats, or no further action is required based on SLs for the 

relevant compounds. This SI was completed at the Barrigada Army Aviation Operations Facility 

(AAOF) in Barrigada, Guam and determined no further action is required for AOI 1. Barrigada

AAOF will be referred to as the “Facility” throughout this document. 

The Facility, operated by Guam ARNG (GUARNG), encompasses approximately 51.3 acres in 

Barrigada, Guam. The SI focuses on the northeastern portion of the GUARNG property, which 

includes two buildings (hangar and waste accumulation and storage building), a helipad, and the 

associated area surrounding the buildings and helipad where AFFF familiarization training may 

have occurred as early as 2016 (AECOM 2021a). 

The PA identified one AOI for investigation during the SI phase. SI sampling results from the 

AOI were compared to OSD SLs. Table ES-2 summarizes the SI results for the AOI. Based on 

the results of this SI, no further evaluation is warranted for the AOI 1 at this time. 

1 Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly referred to as 

GenX) was not included as an analyte at the time of this SI. Based on the conceptual site model (CSM) developed 

during the PA and revised based on SI findings, the presence of HFPO-DA is not anticipated at the facility because 

HFPO-DA is generally not a component of military specification (MIL-SPEC) aqueous film forming foam (AFFF) 

and based on its history including distribution limitations that restricted use of GenX, it is generally not a component 

of other products the military used. In addition, it is unlikely that GenX would be an individual chemical of concern 

in the absence of other PFAS.
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Table ES-1. Screening Levels (Soil and Groundwater)

Analyte2

Residential

(Soil)

(μg/kg)

1 

0 to 2 ft bgs

Industrial/Commercial

Composite Worker

(Soil)

(μg/kg)

 1 

2 to 15 ft bgs

Groundwater

(ng/L) 1 

PFOA 19 250 6

PFOS 13 160 4

PFBS 1,900 25,000 601

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

1. Assistant Secretary of Defense. July 2022. Risk Based Screening Levels Calculated for Groundwater and Soil 

using U.S. Environmental Protection Agency’s (USEPA’s) Regional Screening Level Calculator. Hazard 

Quotient (HQ)=0.1. May 2022

2. Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly 

referred to as GenX) was not included as an analyte at the time of this SI. Based on the CSM developed 

during the PA and revised based on SI findings, the presence of HFPO-DA is not anticipated at the facility 

because HFPO-DA is generally not a component of MIL-SPEC AFFF and based on its history including 

distribution limitations that restricted use of GenX, it is generally not a component of other products the 

military used. In addition, it is unlikely that GenX would be an individual chemical of concern in the absence 

of other PFAS. 

μg/kg = Microgram(s) per kilogram

ng/L = Nanogram(s) per liter

Table ES-2. Summary of Site Inspection Findings and Recommendations

AOI Potential Release Area

Soil

Source Area Future Action

1 Fire Extinguisher Maintenance Area No further action

Legend:

 = Detected; exceedance of screening levels

 = Detected; no exceedance of screening levels

 = Not detected
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1. INTRODUCTION

1.1 PROJECT AUTHORIZATION

The Army National Guard (ARNG) G-9 is the lead agency in performing Preliminary 

Assessments (PAs) and Site Inspections (SIs) at ARNG facilities nationwide based on the current 

or potential historical use of per- and polyfluoroalkyl substances (PFAS) with a focus on six 

compounds presented in the memorandum from the Office of the Secretary of Defense (OSD) 

dated 6 July 2022 (Assistant Secretary of Defense 2022). The six components listed in the OSD 

memorandum will be referred to as “relevant compounds” throughout this document and include 

perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic 

acid (PFBS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), and 

hexafluoropropylene oxide-dimer acid (HFPO-DA)2 at ARNG facilities nationwide. The ARNG 

performed this SI at the Barrigada Army Aviation Operations Facility (AAOF) in Barrigada, 

Guam. The Barrigada AAOF is also referred to as the “Facility” throughout this document. 

The SI project elements were performed in accordance with the Comprehensive 

Environmental Response, Compensation, and Liability Act (CERCLA) (U.S. Environmental 

Protection Agency [USEPA] 1980), as amended, the National Oil and Hazardous Substances 

Pollution Contingency Plan (40 Code of Federal Regulations Part 300; USEPA 1994), and in 

compliance with the U.S. Department of the Army) requirements and guidance for field 

investigations. 

1.2 SITE INSPECTION PURPOSE

A PA was performed at the Facility (AECOM Technical Services, Inc. [AECOM] 2021a) that 

identified one Area of Interest (AOI) where PFAS-containing materials were used, stored, and/or 

disposed, or areas where known or suspected releases to the environment occurred. The objective 

of the SI is to identify whether there has been a release to the environment from the AOI 

identified in the PA and determine whether further investigation is warranted, a removal action is 

required to address immediate threats, or no further action is required based on screening levels 

(SLs) for the relevant compounds.

2 Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly referred to as 

GenX) was not included as an analyte at the time of this SI. Based on the conceptual site model (CSM) developed 

during the PA and revised based on SI findings, the presence of HFPO-DA is not anticipated at the facility because 

HFPO-DA is generally not a component of military specification (MIL-SPEC) aqueous film forming foam (AFFF) 

and based on its history including distribution limitations that restricted use of GenX, it is generally not a component 

of other products the military used. In addition, it is unlikely that GenX would be an individual chemical of concern 

in the absence of other PFAS.
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2. FACILITY BACKGROUND

2.1 FACILITY LOCATION AND DESCRIPTION

The Guam ARNG (GUARNG) Barrigada installation is comprised of Readiness Centers, U.S. 

Property and Fiscal Office and Warehouse, Ready Building, and an AAOF to the northeast, and 

it is located southeast of the Guam International Airport in Barrigada, Guam (Figure 2-1). The 

Facility provides training and maintenance for the various units that support the GUARNG. The

Barrigada installation occupies 78.3 acres of land that was all formerly owned by the U.S. Navy 

and known as the Naval Computer and Telecommunications Master Station (NCTAMS), 

Barrigada. Portions of the Facility have been leased to the GUARNG since 1988 and initially 

managed under a Host Tenant Real Estate Agreement with the Navy. In 2002, 51.3 acres was 

transferred from the Navy to the Army. The GUARNG was granted a license for use of this area 

from the Army. The remaining portion of the Facility totaling 27 acres is still under a Host 

Tenant Real Estate Agreement with the Navy. The U.S. Army Corps of Engineers (USACE) has 

issued a license to the GUARNG for its use.

This SI focuses on the AAOF occupying the northeastern portion of the GUARNG leased 

property still under Host Tenant Real Estate Agreement with the Navy, which includes two 

buildings (hangar and waste accumulation and storage building), a helipad, and the associated 

area surrounding those features totaling approximately 27.21 acres. The Barrigada AAOF 

supports a medivac unit and other GUARNG functions. The Barrigada Complex is surrounded 

by a six-foot high security fence on all sides and is not open to the public. 

The remainder of the NCTAMS, which is still operated by the Navy, exists to the north and east 

of the GUARNG property. Along the northwest side of Barrigada Complex and AAOF is Army 

Drive (Route 16). The P.C. Lujan Elementary School is located to the south of the Facility, and 

the residential areas of San Antonio and Ungaguan are to the west (AECOM 2021a). 

2.2 FACILITY ENVIRONMENTAL SETTING

The Barrigada AAOF is located approximately 2.5 miles south of Tumon Bay. There is a buffer 

of undeveloped land immediately surrounding the Barrigada AAOF to the south and east, but 

further south/southwest there are residential areas and a school. To the north of the AAOF are 

lands associated with the former NCTAMS. Immediately to the west of the AAOF, sits the 

ARNG Readiness Center and associated support facilities (located on the former NCTAMS 

property). The Readiness Center and associated support facilities are abutted by residential areas 

further to the west (Figure 2-2). Throughout the Facility, the natural terrain slopes towards south 

towards the southern coastline of Guam, ranging from a maximum elevation of approximately 

250 to 310 feet (ft) above mean sea level (amsl) (AECOM 2021a).

2.2.1 Geology 

Guam has four major physiographic areas: limestone plateau, volcanic uplands, interior basin, 

and coastal lowlands with alluvial valley floors. The Barrigada AAOF overlies the limestone 

plateau, which includes the north plateau, Orote Peninsula, and the fringing limestone of the 

southeast coast. The north plateau is relatively flat and consists of reef associated limestone that 
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has been uplifted above sea level and tilted to the southwest. Sinkholes range from a few ft to 

approximately 75 ft deep over most of the limestone plateau (AECOM 2021a). 

The Barrigada formation is a white, relatively homogeneous, massive, detrital limestone having a 

characteristic assemblage of large foraminifera. The Barrigada limestone is the principal rock of 

northern Guam and underlies most of the northern half of the island; it unconformably overlies 

Alutom volcanics in some areas and is unconformably overlain by variably thick sequences of 

Mariana limestone. In many places, the Barrigada limestone is brecciated and ranges from 

compact and well-lithified to extremely friable. The permeability of the limestone is relatively 

high and contains fresh basal ground water up to approximately 7 ft amsl (AECOM 2021a).

Soil encountered during SI activities was largely consistent with the above expected lithology, 

mainly ranging from well graded clayey gravels at 0-2 ft bgs to subsurface (below 2 ft bgs) 

poorly graded silty sands. Grain size sample analysis confirmed lithology descriptions, as shown 

in the Grain Size Analysis Table (Appendix F). More than 50 percent of soil was classified as 

sand, with more than half of that designated as medium sand. 

2.2.2 Hydrogeology 

The Barrigada AAOF is part of the northern Guam hydrogeologic province and overlays the 

Northern Guam Lens aquifer situated in the Barrigada limestone. The Barrigada limestone is 

characterized by high porosity due to the dissolution and cavernous features. The term Northern 

Guam Lens” refers to the lens that develops from the rainfall percolates through the surface soil 

to the underlying highly porous limestone and accumulating on and displacing denser water 

(AECOM 2021a).

The Northern Guam Lens aquifer is the primary drinking water source for Guam and underlies 

the entire northern half of the island. The aquifer is divided into vertical zones based on chloride 

concentration. The uppermost zone (i.e., supra-basal) consists of the basal freshwater lens where 

the chloride concentrations are less than 250 milligrams per liter (mg/L) (EPA secondary 

Maximum Concentration Level). This zone is the primary zone used for drinking water. The 

bottom zone (basal) contains saltwater with chloride concentrations at levels nearly of those in 

seawater. In between is a transition zone (parabasal) with chloride concentrations between those 

of freshwater and saltwater chloride concentrations. The thickness of the transition zone depends 

on the extent of mixing between freshwater and saltwater, and is generally several tens of feet 

thick (AECOM 2021b).

The aquifer is composed of six distinct sub-basins and the Facility is located within the Mangilao 

sub-basin. Groundwater in this part of the Mangilao sub-basin is unconfined and characterized as 

parabasal, a term meaning that freshwater lens is of sufficient thickness to be in contact with the 

underlying poorly permeable volcanic basement rock. The elevation of the local water table is 

generally within a few feet above sea level. Static depth to groundwater is generally in excess of 

300 feet bgs given that the Facility generally rests at elevations above 300 feet msl. Reported 

groundwater depths for nearby supply wells are known to range between 290 and 331 feet bgs 

during drilling and well installations. The general direction of groundwater flow is reported to be 

to the south, southeast toward the Pacific Ocean, although pumping from nearby water supply 

wells may affect the flow direction locally (AECOM 2021b). Under the provisions of the Safe 
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Drinking Water Act, the groundwater lens of northern Guam was designated a “principal sole 

source aquifer” (AECOM 2021a).

An Environmental Data Resources, Inc.TM (EDRTM) report conducted a well search for a 1-mile 

radius surrounding the Facility. Using additional online resources, such as state and local 

Geographic Information System databases, wells were researched to a 4-mile radius of the 

Facility. There are no drinking water wells on the Facility, but multiple production wells 

surround the Facility to the north, northeast, and southwest. Based on the south/southeastern 

inferred groundwater direction, some of these production wells may be potentially downgradient 

from the Facility. Groundwater features are presented in Figure 2-3 (AECOM 2021a).

2.2.3 Hydrology 

Despite the large amount of rainfall that occurs on Guam, there are no perennial streams located 

on or in the vicinity of the Facility because of high infiltration rates into the underlying 

limestone. All stormwater at the Barrigada Complex is directed toward ponding basins located 

throughout the facility. All surface water at the AOI is directed to the south into a grass culvert 

where drainage is directed to the south and eventually to the west where is enters a retention 

basin (KHLG & Associates Inc., 2023). The entirety of the Facility lies within the Fonte RiverFrontal Hagatna Bay Watershed (Figure 2-4). 

2.2.4 Climate

Guam’s climate is characterized by mild temperatures, easterly trade winds year-round, and 

humid conditions typical of the tropics. Guam has two seasons: rainy (between July and 

November) and dry (between January and May). The temperature ranges from mid to high-80s 

degrees Fahrenheit (°F), with temperatures decreasing at higher elevations. Humidity on Guam 

ranges from approximately 75 to 100 percent (%). Annual rainfall ranges from 80 inches in the 

coastal lowland areas to 100 inches in the interior upland of southern Guam (AECOM 2021a).

2.2.5 Current and Future Land Use

Current Barrigada AAOF operations include training and maintenance for the various units that 

support the GUARNG. In addition, a medivac unit uses the hangar in the northern portion of the 

property. GUARNG has construction planned and a proposed expansion of the facility's 

footprint. The GUARNG currently leases the property from the U.S. Navy, which borders the 

property to the north and east. The town of Barrigada also abuts the AAOF to the south and west. 

The Facility is fenced, and access is controlled by guarded entry. Reasonably anticipated future 

land use is not expected to change from the current land use described above (AECOM 2021a). 

2.2.6 Sensitive Habitat and Threatened/Endangered Species

A wildlife survey has not occurred at the Facility as part of this investigation, and the Facility 

does not have any significant areas of habitat. The following Species have not been identified at 

the facility but may be present in the surrounding area. 
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The following mammals, birds, reptiles, snails, insects, and plants, are federally endangered, 

threatened, proposed, and/ or are listed as candidate species in Barrigada, Guam (US Fish and 

Wildlife Service [USFWS], 2022). 

• Mammals: Mariana Fruit Bat, Pteropus mariannus (threatened)

• Birds: Guam Micronesian Kingfisher, Halcyon cinnamomina (endangered); Guam Rail 

Rallus owstoni, (endangered); Mariana Common Moorhen, Gallinula chloropus guami, 

(endangered) 

• Reptiles: Slevin’s Skink, Emoia slevini (endangered) 

• Snails: Fragile Tree Snail, Samoana fragilis (endangered); Guam Tree Snail, Partula 

radiolata (endangered); Humped Tree Snail, Partula gibba (endangered) 

• Insects: Mariana Eight-spot Butterfly, Hypolimnas octocula marianensis (endangered); 

Mariana Wandering Butterfly, Vagrans egistina (endangered)

• Flowering Plants: Aplokating-palaoan, Psychotria malaspinae (endangered); 

Berenghenas Halomtano, Solanum guamense (endangered); Cebello Halumtano, 

Bulbophyllum guamense (threatened); Dendrobium guamense (threatened); Eugenia 

bryanii (endangered); Hayun lagu (endangered); Maesa walkeri (threatened); Nervilia 

jacksoniae (threatened), Tabernaemontana rotensis (threatened); Tinospora homosepala 

(endangered); Tuberolabium guamense (threatened); Ufa-halomtano, Heritiera 

logipetiolata (endangered)

• Conifers and Cycads: Fadang, Cycas micronesica (threatened). 

2.3 HISTORY OF PFAS USE 

One AOI was identified in the PA where aqueous film-forming foam (AFFF) may have been 

used, stored, disposed, or released historically at the Facility (AECOM 2021a). Interviews and 

records obtained during the PA indicate that AFFF may have historically been released at the 

Facility during familiarization training and fire training activities as early as 2016. Additional 

AFFF releases may also have occurred from incidental spills. A description of the AOI is 

presented in Section 3. 
Barrigada

Readiness Center

Philippine Sea

Philippine Sea

AAOF

^_

Guam

Facility Data

Facility Boundary

3

0 2

Miles

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:.......WGS 84 UTM 55N

Data Sources:

ESRI 2021

AECOM 2020

Figure 2-1

Facility Location

Army National Guard Site Inspections

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AAOF

Barrigada

Readiness Center

^_

Guam

Facility Data

Facility Boundary

NCTAMS Boundary

3

0 2

Miles

Data Sources:

ESRI 2021

AECOM 2020

Figure 2-2

Topography

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Note: Map by USGS, 2006

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:.......WGS 84 UTM 55N
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Philippine Sea

Philippine Sea

Hagatna River

Chaot River

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River

Sigua River

Lonfit River

Pajon River

^_

Guam

Facility Data

Facility Boundary

Well Type

<! Production Well

Hydrology/Hydrogeology

Inferred Groundwater Flow Direction

River/Stream

Wetlands

3

0 2

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Data Sources:

ESRI 2021

AECOM 2020

Figure 2-3

Groundwater Features

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Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:.......WGS 84 UTM 55N
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Philippine Sea

Philippine Sea

Hagatna River

Chaot River

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Lonfit River

Pajon River

Agana

Watershed Mangilao

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Fonte

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Pago

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Ylig

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Facility Boundary

Area of Interest

Hydrology

Surface Water Flow Direction

River/Stream

Wetlands

Watershed Boundary

3

0 2

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Data Sources:

ESRI 2021

AECOM 2020

Figure 2-4

Surface Water Features

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0 500

Feet

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:.......WGS 84 UTM 55N
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3. SUMMARY OF AREAS OF INTEREST

The PA evaluated areas where PFAS-containing materials may have been used, stored, disposed, 

or released historically. Based on the PA findings, one potential PFAS release area was identified 

at the Barrigada AAOF (AECOM 2021a). The potential release area is shown on Figure 3-1. 

3.1 AOI 1 – FIRE EXTINGUISHER MAINTENANCE AREA

In 2016, new Tri-MaxTM compressed air foam systems (CAFSs) were issued to the GUARNG, 

and personnel received training on the new systems. Training was conducted in the northern 

grassy area of the hangar. As part of the training, personnel were instructed on how to load the 

Tri MaxTM and were shown the various parts of the extinguisher. In addition, hands-on 

demonstrations were conducted on how to properly use the Tri-MaxTM. Based on interviews, 

there was a large amount of foam released during the hands-on demonstrations. One of the 

interviewees maintained that the Tri-MaxTM CAFSs were filled with soap and not AFFF during 

the demonstrations because the AFFF material had not yet arrived (AECOM 2021a).

In early 2019, the Tri-MaxTM CAFSs were emptied of AFFF and the AFFF was moved to 

containers for storage (a 55-gallon drum plus a 5.5-gallon drum). To empty the Tri-MaxTM, the 

personnel interviewed stated that they siphoned the AFFF and then used a shop vac once the 

siphoning was no longer productive. Absorbent pads were placed around the CAFSs and drums 

during the siphoning process to catch any AFFF spills. The shop vac was cleaned with the spigot 

located on the north end of the hangar, and the rinse water was allowed to drain naturally. After 

being cleaned, the shop vac was disposed of in regular municipal waste. The used absorbent pads 

were placed in a single 55-gallon drum and stored with the AFFF drums inside a storage shed, 

located also in the grassy area of the hangar next to where training and maintenance activities 

were conducted (AECOM 2021a).

3.2 POTENTIAL ADJACENT SOURCES

3.2.1 NBG Barrigada

 In 2020 a PA and subsequent SI were performed by Naval Facilities Engineering Command 

(NAVFAC) Pacific of sites at NBG typically associated with PFAS storage or use, or that are 

particularly sensitive to a potential PFAS release, including NBG Barrigada. The PA identified 

seven potential PFAS-affected sites at NBG Barrigada, of which three were identified as 

potential sites for PFAS releases warranting further evaluation (Figure 3-2), including: 

• Building 55 – A former Fire Station located approximately 0.5 miles east-southeast from 

AOI 1. The PA was unable to determine definitive use of the facility for AFFF storage, 

however based on interviews with personnel at other fire stations within NBG, it is 

possible that AFFF was stored and potentially released at this site since AFFF was stored 

at and used by the NBG Fire Department starting in 1976.

• The Nimitz Golf Course, located approximately 0.6 miles from AOI 1 in the 

southwestern portion of the NBG Barrigada boundary, encompasses an approximate 275-

acre area that constitutes a lateral extension southward from the rest of NBG Barrigada. 

The PA determined there was potential that irrigation water used to maintain the golf 
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course was reclaimed from the wastewater treatment plant and may have contained 

PFAS. 

• Two NBG Barrigada potable water supply wells, located approximately 0.6 miles to the 

east, and 0.8 miles to the southeast from AOI 1, are known to exist within the NBG 

Barrigada boundary. The PA determined the potential for PFAS in groundwater at NBG 

(AECOM 2021b). 

During the subsequent SI, soil, sediment, surface water, and potable water samples were 

collected, as appropriate, to further assess the potential for PFAS contamination in the three 

identified areas of concern. PFAS were detected in all surface soil and sediment samples 

collected from NBG Barrigada. Concentrations were generally similar (within an order of 

magnitude) for all samples, and all were below applicable project SLs. PFAS were not detected 

in the surface water located at the former Nimitz Golf Course site indicating PFAS are not 

present in surface water at NBG Barrigada. One potable water sample was collected from a 

supply well which contained concentrations of PFAS at concentrations below the EPA’s drinking 

water lifetime health advisory. The SI recommended additional evaluation of PFAS detections in 

soil and potable water sources at NBG Barrigada (AECOM 2021b).

3.2.2 Guam Antonio B. Won Pat International Airport

The Guam international airport is located to the northwest of the Barrigada Facility and based on 

the south/southeastern inferred groundwater direction, the site is likely upgradient from the 

Facility. Airports generally use AFFF and, while the was no observed AFFF use or release at the 

airport, it is conservatively assumed AFFF is present to respond to airport emergencies. The 

airport is shown on Figure 3-1. 
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NCTAMS

Barrigada

Barrigada

Readiness Center

AAOF

Antonio B.

Won Pat

International

Airport

^_

Guam

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Well Type

<! Production Well

Hydrology

Wetlands

3

0 0.5

Miles

Data Sources:

ESRI 2021

AECOM 2020

Figure 3-1

Area of Interest

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Fire Extinguisher

Maintenance Area

Storage Shed

AOI 1

0 50

Feet

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:.......WGS 84 UTM 55N
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4. PROJECT DATA QUALITY OBJECTIVES

As identified during the data quality objective (DQO) process and outlined in the SI Uniform 

Federal Policy (UFP)−Quality Assurance Project Plan (QAPP) Addendum (EA Engineering, 

Science, and Technology, Inc., PBC [EA] 2022), the objective of the SI is to identify whether 

there has been a release to the environment at the AOIs identified in the PA. For each AOI, 

ARNG determines if further investigation is warranted, a removal action is required to address 

immediate threats, or whether no further action is warranted. This SI evaluated soil for presence 

or absence of relative compounds at each of the sampled AOIs.

4.1 PROBLEM STATEMENT

ARNG will recommend an AOI for Remedial Investigation (RI) if related soil and groundwater 

samples have concentrations of the relevant compounds above the OSD risk-based SLs. The SLs

are presented in Section 6.1 of this report. 

4.2 INFORMATION INPUTS

Primary information inputs for the SI include the following:

• The PA Report for Barrigada AAOF (AECOM 2021a) 

• The Final Preliminary Assessment and Focused Site Inspection of Per- and 

Polyfluoroalkyl Substances, Naval Base Guam, Guam NAVACT Base-wide (AECOM 

2021b) 

• Analytical data from soil samples collected as part of this SI in accordance with the 

site-specific UFP-QAPP Addendum (EA 2022). 

4.3 STUDY BOUNDARIES

The scope of the SI was bounded horizontally by the property limits of the Barrigada AAOF 

(Figure 2-2). Off-Facility sampling was not included in the scope of this SI. If future off-Facility 

sampling is required, the proper stakeholders will be notified, and necessary rights of entry will 

be obtained by GUARNG with property owner(s). Given the anticipated depth to groundwater of 

several hundred ft, the scope of the SI was vertically bounded as follows: soil from hand augers 

(up to 2 ft below ground surface [bgs]) and soil from hollow stem auger (HSA) borings (2 to 30 

ft bgs). Temporal boundaries were limited to the earliest available time field resources were 

available to complete the study.

4.4 ANALYTICAL APPROACH

Samples were analyzed by Eurofins Environment Testing, USA, accredited under the 

Department of Defense (DoD) Environmental Laboratory Accreditation Program (ELAP); 

Accreditation Number [No.] L2468) and the National Environmental Laboratory Accreditation 

Program (NELAP); Certificate No. 4040). PFAS data underwent 100% Stage 2B validation in 

accordance with the DoD General Data Validation Guidelines (2019a) and DoD Data Validation 
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Guidelines Module 3: Data Validation Procedure of Per- and Polyfluoroalkyl Substances 

Analysis by Quality Systems Manual (QSM) Table B-15 (2020). Data were compared to 

applicable SLs and decision rules as defined in the UFP-QAPP Addendum (EA 2022). 

4.5 DATA USABILITY ASSESSMENT

The Data Usability Assessment (DUA), which is provided in Appendix A, is an evaluation at the 

conclusion of data collection activities that uses the results of both data verification and 

validation in the context of the overall project decisions or objectives. Using both quantitative 

and qualitative methods, the assessment determines whether project execution and the resulting 

data have met installation-specific DQOs. Both sampling and analytical activities are considered 

to assess whether the collected data are of the right type, quality, and quantity to support the 

decision-making (DoD 2019a, 2019b; USEPA 2017). 

Based on the DUA, the environmental data collected during the SI were found to be acceptable 

and usable for this SI evaluation with the qualifications documented in the DUA and its 

associated data validation reports. These data are of sufficient quality to meet the objectives and 

requirements of the UFP-QAPP Addendum (EA 2022).
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5. SITE INSPECTION ACTIVITIES 

This section describes the environmental investigation and sampling activities that occurred as 

part of the SI. The SI sampling approach was based on the findings of the PA and was 

implemented in accordance with the following approved documents: 

• Final Preliminary Assessment Report, Barrigada Readiness Center, Guam, dated August 

2020 (AECOM 2021a) 

• Final Programmatic Uniform Federal Policy-Quality Assurance Project Plan, Site 

Inspections for Per- and Polyfluoroalkyl Substances Impacted Sites, ARNG Installations, 

Nationwide, dated December 2020 (EA 2020a) 

• Final Site Inspection Uniform Federal Policy-Quality Assurance Project Plan 

Addendum, Barrigada Army Aviation Operations Facility, Guam, dated February 2022 

(EA 2022) 

• Final Programmatic Accident Prevention Plan, Revision 1, dated November 2020 (EA 

2020b) 

• Final Site Safety and Health Plan, Barrigada Army Aviation Operations Facility, Guam, 

dated November 2021 (EA 2021). 

The SI field activities were conducted on 13 January 2022 and 28 June 2022. Field activities 

consisted of source water sampling and soil sample collection from borings and hand augering 

locations. Field activities were conducted in accordance with the UFP-QAPP Addendum (EA 

2022), except as noted in Section 5.6. 

The following samples were collected during the SI and analyzed for a subset of 24 compounds 

via liquid chromatography/tandem mass spectrometry (LC/MS/MS) compliant with QSM 

Version 5.3 Table B-15 to fulfill the project DQOs:

• Twelve (12) soil samples from 9 soil borings/hand auger locations

• Five (5) quality assurance (QA)/quality control (QC) samples

Figure 5-1 provides the sample locations for all media across the Facility. Table 5-1 presents 

the list of samples collected for each medium. Field documentation is provided in Appendix B. 

A log of Daily Notice of Field Activity was completed throughout the SI field activities, which 

is provided in Appendix B1. Sampling forms are provided in Appendix B2 and land survey 

data is provided in Appendix B3. Additionally, a photographic log of field activities is provided 

in Appendix C. 
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5.1 PRE-INVESTIGATION ACTIVITIES

In preparation for the SI field activities, project team members participated in Technical Project 

Planning (TPP) meetings, performed utility clearance, and sampled decontamination source 

water. Details of these activities are presented below.

5.1.1 Technical Project Planning

The U.S. Army Corps of Engineers (USACE) TPP Process, Engineer Manual (EM) 200-1-2 

(Department of the Army 2016) defines four phases to project planning: (1) defining the project 

phase; (2) determining data needs; (3) developing data collection strategies; and (4) finalizing the

data collection plan. The process encourages stakeholder involvement in the SI, beginning with 

defining overall project objectives, including DQOs, and formulating a sampling approach to 

address the AOIs identified in the PA. 

A combined TPP Meeting 1 and 2 was held on 23 November 2021, prior to SI field activities 

with stakeholders. The combined TPP Meeting 1 and 2 was conducted in general accordance 

with EM 200-1-2. The stakeholders for this SI include ARNG, GUARNG, USACE, and the 

Guam Environmental Protection Agency (GEPA) representatives familiar with the Facility, the

regulations, and the community. Stakeholders were provided the opportunity to make comments 

on the technical sampling approach and methods at the combined TPP Meeting 1 and 2. The 

outcome of the combined TPP Meeting 1 and 2 was memorialized in the UFP-QAPP Addendum 

(EA 2022). 

A TPP Meeting 3 was held on 28 September 2023 to discuss the results of the SI. Meeting 

minutes for TPP 3 are included in Appendix D of this report. Future TPP meetings will provide 

an opportunity to discuss the results and findings, and future actions, where warranted.

5.1.2 Utility Clearance 

EA contacted the GUARNG to notify them of intrusive work at the Facility. Utility clearance 

was performed at each of the proposed boring and hand auger locations on 7 June 2022 with 

input from the GUARNG and the EA field team. Utility maps and access points were used to 

complete the utility clearance. Additionally, for most locations (except AOI01-03) the first 2 ft 

of each boring were pre-cleared by EA’s drilling subcontractor, using a hand auger to verify 

utility clearance in shallow subsurface where utilities would typically be encountered (refer to 

Section 5.6 which discusses deviations). 

5.1.3 Source Water and PFAS Sampling Equipment Acceptability

A sample from a potable water source at the northeast corner of the GUARNG hangar, Building 

800, was collected on 13 January 2022, prior to mobilization, and analyzed for PFAS by 

LC/MS/MS compliant with QSM 5.3 Table B-15.The potable water source used for 

decontamination of drilling equipment was confirmed to be acceptable for use in this 

investigation, and therefore used throughout the field activities. 

Materials that were used within the sampling zone were confirmed as acceptable for use in the 

PFAS sampling environment. The checklist of acceptable materials for use in the PFAS 

sampling 
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environment was provided in the Standard Operating Procedures appendix to the Programmatic 

UFP-QAPP Addendum (EA 2022).

 

5.2 SOIL BORINGS AND SOIL SAMPLING

Surface soil samples from 0 to 2 ft bgs were collected from eight of nine locations using a hand 

auger (except AOI01-03 where the HSA drilling rig was used to collect the 0-2 ft sample). The 

reader is referred to Section 5.6 for a discussions of deviations from the UFP-QAPP. All soil 

sample locations are shown on Figure 5-1. The hand auger location was selected based on the 

AOI information provided in the PA (AECOM 2021a) and as agreed upon by stakeholders 

during the TPP and review of the UFP-QAPP Addendum (EA 2022). Samples were collected in 

grass areas where applicable, to avoid disturbing concrete or asphalt surfaces. Non-dedicated 

sampling equipment (i.e., hand auger) was decontaminated between sampling locations. 

At two locations, subsurface soil samples were collected via HSA drilling methods in accordance 

with UFP-QAPP Addendum (EA 2022) and details of analysis are listed in Table 5-1. A Model 

B-61 sampling system was used to collect continuous soil cores to the target depth. Three 

discrete soil samples were collected for chemical analysis from each soil boring: one sample at 

the surface (0 to 2 ft bgs) and two subsurface soil samples. One subsurface soil sample was 

collected at approximately 15 ft bgs, and one deep subsurface soil sample collected at 30 ft bgs. 

Total boring completion depth was 30 ft bgs at both subsurface boring locations. 

Subsurface soil samples were collected in accordance with the plan, with the exception of 

AOI01-07 which was offset as described in Section 5.6. Borings were installed in grass areas 

where applicable, to avoid disturbing concrete or asphalt surfaces. All soil sample locations are 

shown on Figure 5-1, and boring sample depths are provided in Table 5-2. 

During the sampling, the soil cores were continuously logged for lithological descriptions by the 

field lead using the Unified Soil Classification System. A photoionization detector (PID) was 

used to screen the breathing zone during boring activities as a part of personal safety 

requirements. Observations and measurements were recorded on sampling forms (Appendix B2) 

and in a non-treated field logbook. Depth interval, recovery thickness, PID concentrations, 

moisture, relative density, Munsell color, and Unified Soil Classification System texture were 

recorded. The boring logs are provided in Appendix E. 

Soil borings completed during the SI were found to contain predominantly fine to coarse grained 

sands with varying levels of fines as the dominant subsurface lithology of the unconsolidated 

sediments at the Facility. Surface soils (0-2 ft bgs) were mainly composed of well graded clayey 

gravels. The borings were completed at depths between 2 and 30 ft bgs. These observations are 

consistent with the understood depositional environment of the region.

Each sample was collected into a laboratory-supplied PFAS-free high-density polyethylene 

(HDPE) bottle and labeled using a PFAS-free marker or pen. Samples were packaged on ice and 

transported via Federal Express (FedEx) under standard chain-of-custody (COC) procedures to 

the laboratory and analyzed for PFAS (LC/MS/MS compliant with QSM Version 5.3 Table 

B-15) in accordance with the UFP-QAPP Addendum. QC samples and analysis were performed 

as described in the UFP-QAPP Addendum (EA 2022). 
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Field duplicate samples were collected at a rate of 10% and analyzed for the same parameters as 

the accompanying samples. Matrix spike (MS)/matrix spike duplicates (MSDs) were collected at 

a rate of 5% and analyzed for the same parameters as the accompanying samples. In instances 

when non-dedicated sampling equipment was used, such as a hand auger for the shallow soil 

samples and the HSA for deep soil samples, one equipment blank (EB) was collected per day 

and analyzed for the same parameters as the soil samples. A temperature blank was placed in 

each cooler to ensure that samples were preserved at or below 6 degrees Celsius (°C) during 

shipment. 

After removal of the drill, boreholes were abandoned using the excess soil cuttings from 

borehole drilling activities. 

5.3 SURVEYING

The location of each sampling point was surveyed using a Trimble Geo 7X global positioning 

system. Positions were collected in the applicable Universal Transverse Mercator zone 55N 

projection with World Geodetic System 1984 datum (horizontal) and North American Vertical 

Datum 1988 (vertical). The vertical and horizontal accuracy of the points is +/- 1 meters. 

Position data were collected on 28 June 2022 and are provided in Appendix B3. 

5.4 INVESTIGATION-DERIVED WASTE

As of the date of this report, the disposal of PFAS investigation-derived waste (IDW) is not 

regulated federally. IDW generated during the SI is considered non-hazardous waste and was 

managed in accordance with the UFP-QAPP Addendum (EA 2022). 

Soil IDW (i.e., soil cuttings) and liquid IDW (i.e., purge water, development water, and 

decontamination fluids) generated during the SI activities were placed within the boring and 

discharged directed to the ground surface slightly downgradient from the source of generation, 

respectively (see Appendix B-4 for disposal locations). 

Other solids such as spent personal protective equipment, plastic sheeting, tubing, rope, unused 

monitoring well construction materials, and other environmental media generated during the 

field activities were disposed of at a licensed solid waste landfill. 

5.5 LABORATORY ANALYTICAL METHODS

Samples were analyzed for PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 

at Eurofins Environment Testing, USA, in Sacramento, California, a DoD ELAP- and NELAPcertified laboratory. 

Soil samples were also analyzed for Total organic carbon (TOC) using USEPA Method 9060A, 

pH by USEPA Method 9045D, and grain size by American Society for Testing and Materials 

(ASTM) method D-442. 
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5.6 DEVIATIONS FROM SITE INVESTIGATION UFP-QAPP ADDENDUM

Deviations from the UFP-QAPP Addendum occurred based on conditions encountered during 

the field investigation activities. These deviations were discussed between EA, GUARNG, and 

USACE. Four deviations from the UFP-QAPP Addendum are noted below: 

• The field team deviated from the UFP-QAPP by collecting the surface soil sample from 

0-2 ft bgs from location AOI01-03 using the HSA drilling rig (instead of hand auger). 

• The subsurface soil samples from location AOI01-07 were collected laterally 

approximately 5 ft east of the surface soil sample AOI01-07H due to access issues (the 

drill rig could not set up on the steep slope). 

• Material from multiple locations was composited for the TOC and grain size analysis due 

to similar geologic composition and lack of recovery from borings, which is a deviation 

from the UFP-QAPP. 

• Sample AOI01-03-SB-15 had poor recovery at 15 ft bgs. Due to the poor recovery 

additional material beyond 15 was used to supplement the sample volume. It was also 

noted that the sample is being compared to SLs but this is considered a deviation from the 

UFP-QAPP. 

Table 5-1. Site Inspection Samples by Medium

Barrigada AAOF, Guam

Site Inspection Report

Sample Identification

Sample 

Collection Date

Sample Depth

(ft bgs)

PFAS(USEPA Method 537 Modified)TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

Soil Samples

AOI01-01-SB-2 6/28/2022 0-2 x x

AOI01-02-SB-2 6/28/2022 0-2 x

AOI01-03-SB-2 6/28/2022 0-2 x

AOI01-03-SB-15 6/28/2022 15-184 x MS/MSD

AOI01-03-SB-30 6/28/2022 29-30 x

AOI01-04-SB-2 6/28/2022 0-2 x

AOI01-05-SB-2 6/28/2022 0-2 x

AOI01-06-SB-2 6/28/2022 0-2 x

AOI01-07-SB-21 6/28/2022 0-2 x

AOI01-07-SB-15 6/28/2022 14-15 x

AOI01-07-SB-30 6/28/2022 29-30 x

AOI01-08-SB-2 6/28/2022 0-2 x

AOI01-09-SB-22 6/28/2022 0-2 x FD

AOI01-10-SB-22 6/28/2022 0-2 x FD

BRC-TOC-013 6/28/2022 0-2 x Composite

BRC-GS-013 6/28/2022 0-2 x Composite

Blank Samples
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Sample Identification

Sample 

Collection Date

Sample Depth

(ft bgs)

PFAS(USEPA Method 537 Modified)TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

Soil Samples

ARNG-Tap-01 1/13/2022 NA x Source Water

BRC-EB-01 6/28/2022 NA x EB

Notes:

1 AOI01-SB-2 correlated to location AOI01-07H where the hand auger sample was collected. Subsurface soil samples at AOI01-07 

were collected laterally approximately 5 ft east of the hand auger location as discussed in Section 5.6. 2 These samples are duplicate samples from the original 8 borings, not separate sampling locations as the names may imply. 

3 Material was similar in every location so material was composited due to lack of recovery. See deviation from UFP-QAPP 

addendum listed in Section 5.6. 4 due to poor recovery additional material beyond 15 was used to augment sample volume.

ASTM = American Society for Testing and Materials

FD = field duplicate

GS = grain size

SB = soil boring

EB = equipment blank

Table 5-2. Soil Boring Depths 

Barrigada AAOF, Guam

Site Inspection Report

Area of Interest Boring ID

Soil Boring Depth

(ft bgs)

1 

AOI01-01 2

AOI01-02 2

AOI01-03 30

AOI01-04 2

AOI01-05 2

AOI01-06 2

AOI01-07H 2

AOI01-07 30

AOI01-08 2

Notes:

NA = not applicable
AOI01-01

AOI01-02

AOI01-04

AOI01-06

AOI01-08

AOI01-03

AOI01-05

AOI01-07

AOI 1

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI01-07H

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Sample Locations

Hand Auger 0-2 Feet

Hollow Stem Auger to 30 feet

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

3

0 100

Feet

Data Sources:

ESRI 2021

AECOM 2020

Figure 5-1

Site Inspection Sample Locations

Army National Guard Site Inspections

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Path: \\lovetongis\GISdata\Federal\Nationwide\PFAS\MAES_634250383\PROJECTS\SIReport\Barrigada\BarrigadaSI.aprx

Map Extent

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:.......WGS 84 UTM 55N
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6. SITE INSPECTION RESULTS

This section presents the analytical results of the SI. The SLs used in this evaluation are

presented in Section 6.1. A discussion of the results for the AOI is provided in Section 6.2. 

Tables 6-2 through 6-4 present results for soil for the relevant compounds. Tables that contain 

all results are provided in Appendix F, and the laboratory reports are provided in Appendix G. 

6.1 SCREENING LEVELS

The DoD has adopted a policy to retain facilities in the CERCLA process based on risk-based

SLs for soil and groundwater, as described in a memorandum from the OSD dated 6 July 2022 

(Assistant Secretary of Defense 2022). The ARNG program under which this SI was performed

follows this DoD policy. Should the maximum concentration for sampled media exceed the SLs 

established in the OSD memorandum, the AOI will proceed to the next phase under CERCLA. 

The SLs established in the OSD memorandum apply to the five compounds presented on Table 

6-1. 

Table 6-1. Screening Levels (Soil and Groundwater)

Analyte2

Residential 

(Soil)

(μg/kg)1 

0 to 2 ft bgs

Industrial/Commercial

Composite Worker 

(Soil)

(μg/kg) 1 

2 to 15 ft bgs

Groundwater

(ng/L) 1 

PFOA 19 250 6

PFOS 13 160 4

PFBS 1,900 25,000 601

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

1. Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using 

EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022. 

2. Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly 

referred to as GenX) was not included as an analyte at the time of this SI. Based on the CSM 

developed during the PA and revised based on SI findings, the presence of HFPO-DA is not 

anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC AFFF and 

based on its history including distribution limitations that restricted use of GenX, it is generally not a 

component of other products the military used. In addition, it is unlikely that GenX would be an 

individual chemical of concern in the absence of other PFAS.

 μg/kg = Microgram(s) per kilogram

ng/L = Nanogram(s) per liter

The data in the subsequent sections are compared against the SLs presented in Table 6-1. The 

SLs for soil are based on incidental ingestion and are applied to the depth intervals reasonably 

anticipated to be encountered by the receptors identified at the Facility: the residential scenario is 

applied to surface soil results (0 to 2 ft bgs) and the industrial/commercial worker scenario is 

applied to shallow subsurface soil results (2 to 15 ft bgs). The SLs are not applied to deep 

subsurface soil results (>15 ft bgs) because 15 ft is the anticipated limit of construction activities.
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6.2 SOIL PHYSICOCHEMICAL ANALYSES

To provide basic soil parameter information, soil samples were analyzed for TOC, pH, and grain 

size which are important for evaluating transport through the soil medium. Appendix F contains 

the results of the TOC, pH, and grain size sampling. 

The data collected in this investigation will be used in subsequent investigations, where 

appropriate, to assess fate and transport. According to the Interstate Technology Regulatory 

Council (ITRC), several important PFAS partitioning mechanisms include hydrophobic and 

lipophobic effects, electrostatic interactions, and interfacial behaviors. At relevant environmental 

pH values, certain PFAS are present as organic anions, and are therefore relatively mobile in 

groundwater (Xiao et al., 2015), but tend to associate with the organic carbon fraction that may 

be present in soil or sediment (Higgins and Luthy 2006; Guelfo and Higgins 2013). When 

sufficient organic carbon is present, organic carbon normalized distribution coefficients (Koc 

values) can help in evaluating transport potential, though other geochemical factors (for example, 

pH and presence of polyvalent cations) may also affect PFAS sorption to solid phases (ITRC 

2018). 

Soil pH was measured as 8.4 in samples collected from AOI 1. TOC was 8.6 g/kg in the sample 

collected from AOI 1. 

Grain size was analyzed from a single composite sample (as the material was observed to be 

homogeneous) and compared with United Soil Classification grain size ranges. The combined 

silt and clay content was over 41.5%. The content of sand was 56.5% and grain size ranged from 

16% to 13.2. Only 2.2% gravel was noted in the sample. 

6.3 AOI 1

This section presents the analytical results for soil in comparison to SLs for AOI 1 - Fire 

Extinguisher Maintenance Area. The soil results are summarized on Table 6-2 through Table 6-

4. Soil results are presented on Figure 6-1 through Figure 6-5. 

6.3.1 AOI 1 − Soil Analytical Results

Figures 6-1 through 6-5 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the soil results. 

Soil was sampled from surface soil (0 to 2 ft bgs) from eight locations (AOI01-01 through 

AOI01-08). Soil was also sampled from shallow subsurface soil (15 ft bgs) and deep subsurface 

soil (30 ft bgs) from two boring locations (AOI01-03 and AOI01-07)3. 

PFOA was detected in surface soil at location AOI01-08 at an estimated concentration of 1.3 J+

Microgram(s) per kilogram (μg/kg) below the SL of 19 μg/kg, but not was not detected at any 

3 As noted in Section 5.6, sample AOI01-03-SB-15 had poor recovery at 15 ft bgs. Due to the poor recovery 

additional material beyond 15 ft bgs (down to 18 ft bgs) was used to supplement the sample volume. This sample is 

being compared to SLs, but this is considered a deviation from the UFP-QAPP.
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other surface soil locations. PFNA was detected at surface soil location AOI01-08 at an 

estimated concentration of 0.57 J+ μg/kg, below the SL of 19 μg/kg, but it was not detected at 

any other surface soil locations. There were no detections of PFOS, PFBS, or PFHxS in any 

surface soil samples associated with AOI 1. 

PFOS was detected within the shallow subsurface soil interval of boring locations AOI01-03 and 

AOI01-07 at estimated concentrations of 2.9 J+ μg/kg and 0.81 J+ μg/kg, respectively. These 

results were below the SL of 160 μg/kg There were no detections of PFOA, PFBS, PFHxS, and 

PFNA in any shallow subsurface soil samples associated with the AOI. 

PFHxS was detected within the deep subsurface soil interval of boring location AOI01-03 at an 

estimated concentration of 0.26 J+ μg/kg. PFOS was also detected at an estimated concentration 

of 5.4 J+ μg/kg within the deep subsurface interval of boring location AOI01-03. PFBS, PFNA, 

and PFOA were not detected in deep subsurface soil at AOI01-03. PFBS, PFHxS, PFNA, PFOS, 

and PFOA were not detected in deep subsurface soil interval from boring location AOI01-07. 

6.3.2 AOI 1 - Conclusions

Based on the results of the SI, all five relevant compounds (PFOA, PFOS, PFHxS, and PFNA) 

were detected in soil below their respective SLs. Therefore, further evaluation at AOI 1 is not 

warranted.
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Analyte Screening Level1,2 Unit Result Qual Result Qual Result Qual Result Qual Result Q

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)Perfluorobutanesulfonic acid (PFBS) 1900 g/kg ND UJ ND UJ ND UJ ND UJ ND 

Perfluorohexanesulfonic acid (PFHxS) 130 g/kg ND UJ ND UJ ND UJ ND UJ ND Perfluorononanoic acid (PFNA) 19 g/kg ND UJ ND UJ ND UJ ND UJ ND Perfluorooctanesulfonic acid (PFOS) 13 g/kg ND UJ ND UJ ND UJ ND UJ ND Perfluorooctanoic acid (PFOA) 19 g/kg ND UJ ND UJ ND UJ ND UJ ND Notes:J+ = Estimated concentration, biased high.UJ = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD). Associated numerical value is approximate.g/kg = Microgram(s) per kilogram.1. Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.2. The Screening Levels for soil are based on a residential scenario for direct ingestion of contaminated soil.ft bgs = Feet below ground surface.Qual = Qualifier. ND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Sample Name AOI01-01-SB-2 AOI01-02-SB-2 AOI01-03-SB-2 AOI01-04-SB-2 AOI01-05-S

Location ID AOI01-01 AOI01-02 AOI01-03 AOI01-04 AOI01-05

Parent Sample ID

Sample Date 6/28/2022 6/28/2022 6/28/2022 6/28/2022 

Table 6-2. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil, Site Inspection Re

Depth (ft bgs) 0-2 0-2 0-2 0-2 0-2

6/28/2022

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Analyte Screening Level1,2 Unit Result Qual R

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)Perfluorobutanesulfonic acid (PFBS) 25000 g/kg ND UJ 

Perfluorohexanesulfonic acid (PFHxS) 1600 g/kg ND UJ Perfluorononanoic acid (PFNA) 250 g/kg ND UJ Perfluorooctanesulfonic acid (PFOS) 160 g/kg 2.9 J+ Perfluorooctanoic acid (PFOA) 250 g/kg ND UJ Notes:J+ = Estimated concentration, biased high.UJ = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD). Associated numerical value is approximate.g/kg = Microgram(s) per kilogram.1. Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022. 2. The Screening Levels for soil are based on incidental ingestion of soil in a industrial/commercial worker scenario. ft bgs = Feet below ground surface.Qual = Qualifier.ND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Sample Name AOI01-03-SB-15 

Table 6-3. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Shallow Subsurface Soil, Site Inspecti

Depth (ft bgs) 15-18 

Parent Sample ID A

Sample Date 6/28/2022 

Location ID AOI01-03 

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Analyte Unit Result Qual 

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)Perfluorobutanesulfonic acid (PFBS) g/kg ND UJ 

Perfluorohexanesulfonic acid (PFHxS) g/kg 0.26 J+ 

Perfluorononanoic acid (PFNA) g/kg ND UJ 

Perfluorooctanesulfonic acid (PFOS) g/kg 5.4 J+ Perfluorooctanoic acid (PFOA) g/kg ND UJ Notes:J+ = Estimated concentration, biased high.UJ = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD). Associated numerical value is approximate.g/kg = Microgram(s) per kilogram.ft bgs = Feet below ground surface.Qual = Qualifier.ND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Table 6-4. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Deep Subsurface Soil, Site Inspectio

Depth (ft bgs) 29-30 

Parent Sample ID

Sample Date 6/28/2022 

Location ID AOI01-03 

Sample Name AOI01-03-SB-30 

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Figure 6-1

PFOS Detections in Soil (AOI 1)

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07

AOI01-06

AOI01-03

AOI01-08

AOI01-05

AOI01-04

AOI01-02

AOI01-01

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

3

0 100

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

Guam

Data Sources:

ESRI 2020

AECOM 2020

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 55N

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

Notes:

PFOS = Perfluorooctanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.
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Figure 6-2

PFOA Detections in Soil (AOI 1)

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07

AOI01-06

AOI01-03

AOI01-08

AOI01-05

AOI01-04

AOI01-02

AOI01-01

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

3

0 100

Feet

^_

Guam

Data Sources:

ESRI 2020

AECOM 2020

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Notes:

PFOA = Perfluorooctanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 55N
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Figure 6-3

PFBS Detections in Soil (AOI 1)

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07

AOI01-06

AOI01-03

AOI01-08

AOI01-05

AOI01-04

AOI01-02

AOI01-01

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

3

0 100

Feet

^_

Guam

Data Sources:

ESRI 2020

AECOM 2020

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

Notes:

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 55N
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Figure 6-4

PFHxS Detections in Soil (AOI 1)

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07

AOI01-06

AOI01-03

AOI01-08

AOI01-05

AOI01-04

AOI01-02

AOI01-01

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

3

0 100

Feet

^_

Guam

Data Sources:

ESRI 2020

AECOM 2020

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Notes:

PFHxS = Perfluorohexanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 55N
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Figure 6-5

PFNA Detections in Soil (AOI 1)

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07

AOI01-06

AOI01-03

AOI01-08

AOI01-05

AOI01-04

AOI01-02

AOI01-01

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

Fire Extinguisher

Maintenance Area

Storage Shed

Hangar

AOI 1

AOI01-07H

AOI01-03

3

0 100

Feet

^_

Guam

Data Sources:

ESRI 2020

AECOM 2020

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Notes:

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Date:..............................May 2023

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 55N
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7. EXPOSURE PATHWAYS

The conceptual site model (CSM) for AOI 1, revised based on the SI findings, is presented on 

Figure 7-1. Please note that while the CSM discussion assists in determining if a receptor may 

be impacted, the decision to move from SI to RI or interim action is determined based upon 

exceedances of the SLs for the relevant compounds and whether the release is more than likely 

attributable to the DoD. A CSM presents the current understanding of the Facility conditions 

with respect to known and suspected sources, potential transport mechanisms and migration 

pathways, and potentially exposed human receptors. A human exposure pathway is considered 

potentially complete when the following conditions are present: 

1. Contaminant source 

2. Environmental fate and transport

3. Exposure point 

4. Exposure route 

5. Potentially exposed populations

If any of these elements are missing, the pathway is incomplete. The CSM figures use an empty 

circle symbol to represent an incomplete exposure pathway. Areas with no identified complete 

pathway generally warrant no further action. However, the pathway is considered potentially 

complete if the relevant compounds are detected, in which case the CSM figure uses a half-filled 

circle symbol to represent a potentially complete exposure pathway. Additionally, a completely 

filled circle symbol is used to indicate when a potentially complete exposure pathway has 

detections of relevant compounds above the SLs. Areas with an identified potentially complete 

pathway that have detections of the relevant compounds above the SLs may warrant further 

investigation. Although the CSMs indicate whether potentially complete exposure pathways may 

exist, the recommendation for future study in an RI or no action at this time is based on the 

comparison of the SI analytical results for the relevant compounds to the SLs. 

In general, the potential routes of exposure to the relevant compounds are ingestion and 

inhalation. Human exposure via the dermal contact pathway may occur, and current risk practice 

suggests it is an insignificant pathway compared to ingestion; however, exposure data for dermal 

pathways are sparse and continue to be the subject of toxicological study. The receptors 

evaluated are consistent with those listed in USEPA guidance for risk screening (USEPA 2001). 

Receptors at the Facility include site workers (e.g., Facility staff and visiting soldiers), 

construction workers, trespassers (although unlikely due to restricted access/fencing), residents 

outside the Facility boundary, and recreational users outside of the Facility boundary. 

7.1 SOIL EXPOSURE PATHWAY 

The SI results for soil were used to determine whether a potentially complete pathway exists 

between the source and potential receptors at AOI 1 based on the aforementioned criteria. 

7.1.1 AOI 1 

AOI 1 is associated with a fire extinguisher maintenance area where controlled AFFF releases 

through familiarization training may have occurred potentially as early as 2016. PFOA and 
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PFNA were detected below SLs in surface soil at AOI 1. Site workers and construction workers 

could contact constituents in surface soil via incidental ingestion and inhalation of dust. PFOS 

and PFHxS were detected below SLs in shallow subsurface soil. Construction workers could also 

contact constituents in soil via incidental ingestion and inhalation of dust. GUARNG has 

construction planned and a proposed expansion of the facility's footprint. Therefore, the soil 

exposure pathway for site workers and construction workers are considered potentially complete. 

The site is fenced and secured and there are no residents onsite or adjacent to the Facility; 

therefore, the incidental ingestion and inhalation of dust pathways for the Resident and 

Trespasser/ Recreational User are considered incomplete. The CSM is presented in Figure 7-1. 

7.2 GROUNDWATER EXPOSURE PATHWAY

The SI results were used to determine whether a potentially complete pathway exists between the 

source and potential receptors at AOI 1 based on the aforementioned criteria. 

7.2.1 AOI 1 

Groundwater was not encountered during drilling of boring holes, so no groundwater samples 

were collected. The Barrigada formation beneath the facility is limestone which has a relatively 

high permeability. Static depth to groundwater is generally in excess of 300 feet bgs given that 

the Facility generally rests at elevations above 300 feet msl. 

Reported groundwater depths for nearby supply wells are known to range between 290 and 331 

feet bgs during drilling and well installations. The general direction of groundwater flow is 

reported to be to the south, southeast toward the Pacific Ocean. There are no drinking water 

wells on the Facility. Based on the lack of drinking water wells on the facility, depth to 

groundwater, and lack of groundwater/surface water interaction, the groundwater pathway is 

considered incomplete for site workers, and construction workers on the facility. 

Multiple production wells surround the Facility to the north, northeast, and southwest. Based on 

the south/southeastern inferred groundwater direction, some of these production wells may be 

potentially downgradient from the Facility. Soil sampling in the upper soil layers indicated the 

presence of “relevant compounds” at levels below SLs; therefore, the groundwater pathway is 

considered potentially complete for residents downgradient of the facility. Given the depth to 

groundwater, there is no known groundwater/surface water interaction; therefore, the 

Trespasser/Recreational User pathway is considered incomplete. The CSM is presented in 

Figure 7-1. 

7.3 SURFACE WATER AND SEDIMENT PATHWAY

The SI results were used to determine whether a potentially complete pathway exists between the 

source and potential receptors at AOI 1 based on the aforementioned criteria. 
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7.3.1 AOI 1 

All stormwater at the Barrigada Complex is directed toward ponding basins located throughout 

the Facility. All stormwater/surface water at the AOI is directed to the south into a grass culvert 

where drainage is directed to the south and eventually to the west where is enters a retention 

basin on the Facility. Soil sampling within the drainage pathway indicated the presence of 

“relevant compounds” at levels below SLs. Site workers and construction workers could contact 

constituents in drainage pathways (which are accessible onsite) through incidental ingestion and 

inhalation of dust. Therefore, the surface water/sediment pathway is considered potentially 

complete for these receptors. 

The Barrigada Complex is fenced and there is no recreational use on the facility or nearby. Also, 

there are no nearby residential areas and no onsite residential housing; therefore, the stormwater 

and sediment pathway for trespassers and residents is considered incomplete. The CSM is 

presented in Figure 7-1. 
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Notes:

1. Groundwater is generally in excess of 300 ft 

below ground surface. 

2. No current active construction at the facility, 

but construction is planned.

3. The resident and recreational users refer to 

off-site receptors.

4. Inhalation of dust for off-site receptors is 

likely insignificant. 

Figure 7-1

Conceptual Site Model

 AOI 1 Barrigada AAOF

RECEPTOR

Human Receptors:

Current/Future

Site 

Worker

Construction 

Worker1, 2 Resident3,4 Trespasser/ 

Recreational User3,4

AOI 1

PFAS in 

Surface 

Soil

PFAS in 

Subsurface 

Soil

Human 

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne 

Soil 

Particulate

Surface 

Soil

Surface 

Water/ 

Sediment

Subsurface 

Soil

Shallow 

Groundwater

Ingestion

Ingestion

Ingestion

Ingestion

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Fire 

Extinguisher 

Maintenance 

Area

SOURCE

Source Release 

Mechanism Media

PATHWAY

Transport

and Migration Media Exposure 

Routes

Inhalation 

of Dust

Site 

Worker

Construction 

Worker1, 2 Resident3,4 Trespasser/ 

Recreational User3,4
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Site Inspection Report

Barrigada Army Aviation Operations Facility, Guam Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 8-1 

8. SUMMARY AND OUTCOME

This section summarizes SI activities and findings. The most significant findings are summarized 

in this section and are reproduced directly or abstracted from information contained in this 

report. The outcome provides general and comparative interpretations of the findings relative to 

the SLs. 

8.1 SITE INSPECTION ACTIVITIES 

The SI field activities at the Facility were conducted on 13 January 2022 and 28 June 2022. The 

SI field activities included soil sample collection. Field activities were conducted in accordance 

with the UFP-QAPP Addendum (EA 2022), except as previously noted in Section 5.6. 

To fulfill the project DQOs set forth in the approved SI UFP-QAPP Addendum (EA 2022), 

samples were collected and analyzed for a subset of 24 compounds by LC/MS/MS compliant 

with QSM Version 5.3 Table B-15 as follows: 

• Twelve soil samples from 9 locations

• Five (5) QA/QC samples.

An SI is conducted when the PA determines an AOI exists based on probable use, storage, and/or 

disposal of PFAS-containing materials. The SI includes multi-media sampling at AOIs to 

determine whether or not a release has occurred. The SI may conclude further investigation is 

warranted, a removal action is required to address immediate threats, or no further action is 

required. Additionally, the CSM was refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at the AOI, which is 

described in Section 7. 

8.2 OUTCOME

Based on the results of this SI, no further evaluation is warranted for AOI 1 at this time (see 

Table 8-1). No Groundwater sampling was conducted. Based on the CSM developed and 

revised based on the SI findings, there is no potential for soil exposure to site and construction 

workers from releases during historical DoD activities at the Facility. Sample analytical 

concentrations collected during this SI were compared against the project SLs for soil, as 

described in Table 6-1. A summary of the results of the SI data relative to SLs is as follows:

• At AOI 1:

 The detected concentrations of PFOS, PFHxS, PFNA, and PFOA in soil at AOI 1 

were below their respective SLs. 

Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA 

(commonly referred to as GenX) was not included as an analyte at the time of this SI. Based on 

the CSM developed during the PA and revised based on SI findings, the presence of HFPO-DA 

is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC
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AFFF and based on its history including distribution limitations that restricted use of GenX, it is 

generally not a component of other products the military used. In addition, it is unlikely that 

GenX would be an individual chemical of concern in the absence of other PFAS.

Table 8-1 summarizes the SI results for soil used to determine if an AOI should be considered 

for further investigation under CERCLA and undergo an RI. 

Table 8-1. Summary of Site Inspection Findings and Recommendations

AOI Potential Release Area

Soil

Source Area Future Action

1 

Fire Extinguisher Maintenance 

Area No further action

Legend:

 = Detected; exceedance of screening levels

 = Detected; no exceedance of screening levels

 = Not detected
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———. 2021b. Final Preliminary Assessment and Focused Site Inspection of Per- and 

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using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 

2022 

Assistant Secretary of Defense. 2022. Investigation Per- and Polyfluoroalkyl Substances within 

The Department of Defense Cleanup Program. United States Department of Defense. 6 

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Department of the Army. 2016. EM-200-1-2, Environmental Quality, Technical Project 

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———. 2019a. Department of Defense (DoD), Department of Energy (DOE) Consolidated

Quality Systems Manual (QSM) for Environmental Laboratories, Version 5.3. May. 

. 2019b. General Data Validation Guidelines. November. 

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EA Engineering, Science, and Technology, PBC (EA). 2020a. Final Programmatic Uniform 

Federal Policy Quality Assurance Project Plan, Site Inspections for Per- and 

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. 2020b. Final Programmatic Accident Prevention Plan, Revision 1. November. 

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aqueous film-forming foam (AFFF)-impacted sites. Environmental Science and 

Technology 47(9):4164-71. 
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EA Engineering, Science, and Technology, Inc., PBC 9-2 

Higgins, C.P., and R.G. Luthy. 2006. Sorption of perfluorinated surfactants on sediments. 

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. 1994. National Oil and Hazardous Substances Pollution Contingency Plan (Final Rule).

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. 2017. National Functional Guidelines for Organic Superfund Data Review. OLEM 

9355.0-136, EPA-540-R-2017-002. Office of Superfund Remediation and Technology 

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Xiao, F., M. F. Simcik, T.R. Halbach, and J.S Gulliver. 2015, Perfluorooctane sulfonate (PFOS) 

and perfluorooctanoate (PFOA) in soils and groundwater of a U.S. metropolitan area: 

Migration and implications for human exposure. Water Research 72:64-74.