FINAL

Preliminary Assessment Report

Waiawa Gulch Training Site and Unit 

Training and Equipment Site, Oahu, 

Hawai’i

Perfluorooctanesulfonic Acid (PFOS) and Perfluorooctanoic Acid 

(PFOA) Impacted Sites

ARNG Installations, Nationwide

September 2020

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED
PFAS Preliminary Assessment Report

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Table of Contents

Executive Summary .................................................................................................................... 1

1. Introduction ........................................................................................................................ 5

1.1 Authority and Purpose .............................................................................................. 5

1.2 Preliminary Assessment Methods ............................................................................. 5

1.3 Report Organization .................................................................................................. 6

1.4 Facility Location and Description............................................................................... 6

1.5 Facility Environmental Setting ................................................................................... 6

1.5.1 Geology ......................................................................................................... 7

1.5.2 Hydrogeology ................................................................................................. 7

1.5.3 Hydrology ....................................................................................................... 8

1.5.4 Climate ........................................................................................................... 8

1.5.5 Current and Future Land Use ......................................................................... 8

2. Fire Training Areas ........................................................................................................... 12

3. Non-Fire Training Areas ................................................................................................... 13

3.1 Storage Buildings .................................................................................................... 13

3.2 Firetruck Pump Test Area ........................................................................................ 13

3.3 Vehicle Maintenance Facility ................................................................................... 13

4. Emergency Response Areas ............................................................................................ 15

5. Adjacent Sources ............................................................................................................. 16

6. Preliminary Conceptual Site Model .................................................................................. 17

6.1 AOI 1: Firetruck Pump Test Area ............................................................................. 17

6.2 AOI 2: Vehicle Maintenance Facility, Firetruck Parking Area, and Storage

Buildings ................................................................................................................. 17

7. Conclusions ..................................................................................................................... 21

7.1 Findings .................................................................................................................. 21

7.2 Uncertainty ............................................................................................................. 21

7.3 Potential Future Actions .......................................................................................... 22

8. References ...................................................................................................................... 25
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Tables

Table ES- 1 

Table 7-1

Table 7-2

Table 7-3

AOIs at Waiawa Gulch Training Site and UTES 

AOIs at Waiawa Gulch Training Site and UTES 

Uncertainties

PA Findings Summary

Figures

Figure ES-1 Summary of Findings

Figure ES-2 Preliminary Conceptual Site Model

Figure 1-1 Facility Location

Figure 1-2 Groundwater Features

Figure 1-3 Surface Water Features

Figure 3-1 Non-Fire Training Areas

Figure 6-1 Areas of Interest

Figure 6-2 Preliminary Conceptual Site Model, AOI 1

Figure 6-3 Preliminary Conceptual Site Model, AOI 2

Figure 7-1 Summary of Findings

Appendices

Appendix A Data Resources

Appendix B Preliminary Assessment Documentation

B.1 Interview Records

B.2 Visual Site Inspection Checklists

B.3 Conceptual Site Model Information

Appendix C Photographic Log
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Acronyms and Abbreviations

°F degrees Fahrenheit

AECOM AECOM Technical Services, Inc.

AFFF aqueous film forming foam

AOI area of interest

ARNG Army National Guard

bgs below ground surface

CERCLA Comprehensive Environmental Response, Compensation, and Liability

Act

CFR Code of Federal Regulations

CSM conceptual site model

DON Department of the Navy

EDRTM Environmental Data Resources, Inc.TM

FTA

HA

fire training area

Health Advisory

HIARNG Hawai’i Army National Guard

PA Preliminary Assessment

PFAS per- and poly-fluoroalkyl substances

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

SI Site Inspection

US United States

USACE United States Army Corps of Engineers

USEPA United States Environmental Protection Agency

UTES Unit Training and Equipment Site

VSI visual site inspection
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Executive Summary

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

Inspections (SIs) for Perfluorooctanesulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA)

Impacted Sites at ARNG Facilities Nationwide. A PA for per- and polyfluoroalkyl substances

(PFAS)-containing materials was completed for Waiawa Gulch Training Site and Unit Training and

Equipment Site (UTES) facility (also referred to as the “facility”), to assess potential PFAS release

areas and exposure pathways to receptors. Waiawa Gulch Training Site and UTES provides

training and vehicle maintenance for the various units that support the Hawai’i Army National

Guard (HIARNG). The facility includes several buildings associated with Waiawa Gulch Training

Site and UTES functions, including maintenance and office related buildings, warehouse, storage

buildings, and wash rack. The US Navy historically owned the facility property beginning 3 August

1945. On 21 July 1959, the property was transferred from the Navy to the HIARNG (Argonne

National Laboratory 1993).

The performance of this PA included the following tasks:

 Reviewed available administrative record documents and Environmental Data Resources,

Inc. (EDR)TM report packages to obtain information relevant to potential PFAS releases, such

as: drinking water well locations, historical aerial photographs, Sanborn maps, and

environmental compliance actions in the area surrounding the facility;

 Conducted a site visit on 30 April 2019 and completed visual site inspections at locations

where PFAS-containing materials were suspected of being stored, used, or disposed;

 Interviewed current Waiawa Gulch Training Site and UTES personnel during the site visit,

including the Facility Manager;

 Developed a preliminary conceptual site model (CSM) to outline the potential release and

pathway of PFAS for the area(s) of interest (AOIs) and the facility.

Two AOIs related to potential PFAS releases were identified at the Waiawa Gulch Training Site

and UTES facility during the PA. The date of potential release for the AOIs is estimated based on

secondary data; exact dates are unknown. The AOIs are shown on Figures ES-1 and described

in Table ES-1 below. The preliminary CSM for the two AOIs at Waiawa Gulch Training Site and

UTES facility is presented in Figure ES-2.

Table ES- 1 AOIs at Waiawa Gulch Training Site and UTES

Area of Interest Name Used by Potential Release Dates

AOI 1 Firetruck Pump Test

Area HIARNG Monthly testing; first date of testing is unknown

AOI 2

Vehicle Maintenance

Area, Firetruck Parking,

and Storage Buildings

HIARNG Latest known early 2000s.

Based on the potential release concerning the AFFF at the facility, there is potential for exposure

to PFAS contamination in media at or near the facility. The preliminary CSM for the Waiawa Gulch

Training Site and UTES, which presents the potential receptors and media impacted, is shown on

Figure ES-2. Based on the US Environmental Protection Agency’s (USEPA) Unregulated

Contaminant Monitoring Rule 3 data, it was indicated that no PFAS were detected in a public

water system above the USEPA’s Lifetime Drinking Water Health Advisory (HA) within 20 miles of

the facility. The HA is 70 parts per trillion for PFOS and PFOA, individually or combined. PFAS

analyses performed in 2016 had method detection limits that were higher than currently
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achievable. Thus, it is possible that low concentrations of PFAS were not detected during the

UCMR3 but might be detected if analyzed today.
Maintenance

Building

Waihona Street

Wash Rack

Waiawa Stream

Waiawa Stream

Vehicle

Maintenance

Facility

Fire Truck

Parking Area

Fire Truck

Pump Test

Area

Storage Buildings

Metal Storage

Containers

AOI 1

AOI 2

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Summary of Findings

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0 300 600 150

Feet

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No Suspected Release

Facility Boundary

River/Stream

Trench Drain

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SOURCE PATHWAY RECEPTOR

AOI 1

and

AOI 2

AFFF 

releases 

during pump 

and nozzle 

testing and 

spills during 

transport and 

storage

Human 

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOI 1

Surface 

Water/

Sediment

Subsurface 

Soil

Groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Complete Pathway

Site 

Worker

Construction 

Worker Resident Trespasser/

Recreational User

Site 

Worker

Construction 

Worker Resident Trespasser

/ /

/ / /

LEGEND

/

Figure ES-2

Preliminary Conceptual Site Model

Waiawa Gulch Training Site and UTES, HI

/

/

/

/

PFAS in 

Surface Soil

Notes:

1. The resident and recreational user 

receptors refer to an off-site resident

and recreational user.

2. Dermal contact exposure pathway

is incomplete for PFAS

/ / /

/ /

/

/ /

/ /

4
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1. Introduction

1.1 Authority and Purpose

The Army National Guard (ARNG)-G9 is the lead agency in performing Preliminary Assessments

(PAs) and Site Inspections (SIs) for Perfluorooctane Sulfonic acid (PFOS) and Perfluorooctanoic

acid (PFOA) at Impacted Sites at ARNG Facilities Nationwide. This work is supported by the

United States (US) Army Corps of Engineers (USACE) Baltimore District and their contractor

AECOM Technical Services, Inc (AECOM) under Contract Number W912DR-12D-0014, Task

Order W912DR17F0192, issued 11 August 2017.

The ARNG is assessing potential effects on human health related to processes at their facilities

that used per- and poly-fluoroalkyl substances (PFAS) (a suite of related chemicals), primarily

releases of aqueous film forming foam (AFFF) although other sources of PFAS are possible. In

addition, the ARNG is informally assessing businesses or operations adjacent to the ARNG facility

(not under the control of ARNG) that could potentially be responsible for a PFAS release.

PFAS are classified as emerging environmental contaminants that are garnering increasing

regulatory interest due to their potential risks to human health and the environment. PFAS

formulations contain highly diverse mixtures of compounds. Thus, the fate of these PFAS

compounds in the environment varies. The regulatory framework at both federal and state levels

continues to evolve. The US Environmental Protection Agency (USEPA) issued Lifetime Drinking

Water Health Advisory (HA) for PFOA and PFOS in May 2016, but there are currently no

promulgated national standards regulating PFAS in drinking water. The HA is 70 parts per trillion

for PFOS and PFOA, individually or combined.

This report presents findings of a PA for PFAS-containing materials at Waiawa Gulch Training Site

and Unit Training and Equipment Site (UTES) facility (also referred to as the “facility”) in Pearl

City, Hawai’i in accordance with the Comprehensive Environmental Response, Compensation,

and Liability Act (CERCLA), as amended, the National Oil and Hazardous Substances Pollution

Contingency Plan (40 Code of Federal Regulations [CFR] Part 300), and Army requirements and

guidance.

This PA Report documents potential locations where PFAS containing materials are stored and

have the potential to be released into the environment at or adjacent to the Waiawa Gulch Training

Site and UTES. The term PFAS will be used throughout this report to encompass all PFAS

chemicals being evaluated, including PFOS and PFOA, which are key components of AFFF.

1.2 Preliminary Assessment Methods

The performance of this PA included the following tasks:

 Reviewed available administrative record documents and Environmental Data Resources,

Inc. (EDR)TM report packages to obtain information relevant to potential PFAS releases, such

as: drinking water well locations, historical aerial photographs, Sanborn maps, and

environmental compliance actions in the area surrounding the facility;

 Conducted a site visit on 30 April 2019 and completed visual site inspections (VSIs) at

locations where PFAS-containing materials were suspected of being stored, used, or

disposed;

 Interviewed current Waiawa Gulch Training Site and UTES personnel during the site visit

including the Facility Manager;
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 Developed a preliminary conceptual site model (CSM) to outline the potential release and

pathway of PFAS for the area(s) of interest (AOIs) and the facility.

1.3 Report Organization

This report has been prepared in accordance with the USEPA Guidance for Performing

Preliminary Assessments under CERCLA (USEPA, 1991). The report sections and descriptions

of each are as follows:

 Section 1 – Introduction: identifies the project purpose and authority and describes the

facility location, environmental setting, and methods used to complete the PA

 Section 2 – Fire Training Areas: describes the fire training areas (FTAs) at the facility

identified during the site visit

 Section 3 – Non-Fire Training Areas: describes other locations of potential PFAS releases

at the facility identified during the site visit

 Section 4 – Emergency Response Areas: describes areas of potential PFAS release at the

facility, specifically in response to emergency situations

 Section 5 – Adjacent Sources: describes sources of potential PFAS release adjacent to the

facility that are not under the control of ARNG

 Section 6 – Preliminary Conceptual Site Model: describes the pathways of potential PFAS

transport and receptors at the facility

 Section 7 –Conclusions: summarizes the data findings and presents the conclusions and

uncertainties of the PA

 Section 8 – References: provides the references used to develop this document

 Appendix A – Data Resources

 Appendix B – Preliminary Assessment Documentation

 Appendix C – Photographic Log

1.4 Facility Location and Description

Waiawa Gulch Training Site and UTES facility is located north of Pearl Harbor, on the island of

Oahu (Figure 1-1). The facility falls 0.75 miles northeast of the H1-H2 merge. The facility is

bordered to the north and south by industrial activities, and to the west by a privately-operated

junk yard. The Waiawa Gulch Training Site and UTES facility comprise approximately 20 acres.

Waiawa Gulch Training Site and UTES facility provides training and maintenance for the various

units that support the Hawai’i Army National Guard (HIARNG). The Waiawa Gulch Training Site

and UTES facility consists of office areas, a wash bay, maintenance shop, motor pool, and various

small storage buildings. Historical aerial photography indicates that a large motor pool and

storage facility was located on the northern portion of the property, prior to 2014. The US Navy

historically had ownership of the facility property from 3 August 1945. On 21 July 1959, the

property was transferred to the HIARNG (Argonne National Laboratory 1993).

1.5 Facility Environmental Setting

The Waiawa Gulch Training Site and UTES facility is located approximately 1.25 miles north of

Middle Loch. Throughout Waiawa Gulch Training Site and UTES, the natural terrain slopes south
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towards Pearl Harbor and west towards Waiawa Stream, ranging from a maximum elevation of

90 feet above mean sea level (amsl) to 50 feet amsl.

1.5.1 Geology

Two major volcanic mountain ranges forming the island of Oahu are the Waianae Range in the

west and the much younger Koolau Range in the east. Both ranges are the eroded remnants of

the large elongate Waianae and Koolau shield volcanoes. After a long period of erosion, volcanic

activity resumed with the Honolulu Volcanic Series and its eruption of vents and lava flows. The

eruptions produced by these features tended to be discrete, explosive events that produced

volumes of ash that blanketed older sloping Koolau basalt baserock.

On the central and eastern side of Oahu, the underlying baserock extrusive volcanic layers are

lava flows from the Koolau shield volcano. Layers of A’a flows, pahoehoe flows, and clinker

boundaries can be found in the subsurface (McDonald et. al, 1983). Geology beneath the facility

is older alluvium (Sherrod, et al. 2007).

The facility lies predominately on soil consisting of fill materials originating from dredging or hauled

in from nearby areas (Argonne National Laboratory 1993). This soil is composed of primarily silty

clay and sandy clay. The soil along the boundaries of the facility consists of Kawaihapai stony

clay loam (Department of the Navy [DON] 2016). The total thickness of the soil formation

decreases from north to south, with maximum depth to bedrock at 200 feet below ground surface

(bgs) (DON 1990).

1.5.2 Hydrogeology

The basal aquifer that underlies Waiawa Gulch Training Site and UTES is part of the Pearl Harbor

Aquifer, the most productive aquifer in the state. As such, multiple industrial, agricultural, and

domestic wells are located directly downgradient of the facility (Figure 1-2). An Environmental

Data Resources, Inc (EDR)TM report conducted a well search for a 1-mile radius surrounding the

facility (Appendix A). Using additional online resources, such as state and local GIS databases,

wells were researched to a 4-mile radius of the facility. Numerous wells of various use exist in all

directions surrounding the facility. Directly downgradient of the facility, there are multiple domestic

and irrigation wells. Municipal water supply wells are located both east and west of the facility

within 4 miles. Drinking water at Waiawa Gulch Training Site and UTES is resourced from public

drinking water wells that are located cross-gradient, approximately 0.75 miles west of the facility.

Based on the USEPA Unregulated Contaminant Monitoring Rule 3 (UCMR3) data, it was indicated

that no PFAS were detected in a public water system above the HA within 20 miles of the facility.

The HA is 70 parts per trillion for PFOS and PFOA, individually or combined. PFAS analyses

performed in 2016 had method detection limits that were higher than currently achievable. Thus,

it is possible that low concentrations of PFAS were not detected during the UCMR3, but might be

detected if analyzed today. The basal groundwater originates as rainwater falling in higher

drainage basins to the north and northeast of the facility. The basal groundwater generally

migrates seaward towards Pearl Harbor (Figure 1-2) through zones of clinkers (McDonald,

Abbott, and Peterson 1983). The basal aquifer can be divided into three zones: upper, middle,

and lower. The upper basal aquifer consists of a mixture of rainfall recharge, irrigation return, and

subsurface inflow (DON 1990).

The hydrologic and geologic classification of the upper aquifer in the Waiawa aquifer system

(Aquifer Code 3-02-02-111, Status Code 11111) describes the aquifer as a basal, unconfined

aquifer in horizontally extensive flank basalt lava flows. The groundwater status for the upper

aquifer is classified as the following: a currently used drinking water source that is ecologically

important; fresh water (salinity less than 250 mg/L chloride); irreplaceable in uniqueness; and 
PFAS Preliminary Assessment Report

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highly vulnerable to contamination (Mink and Lau 1990). Based on information provided by

HIARNG, depth to groundwater at the facility is approximately 12 to 15 feet bgs.

1.5.3 Hydrology

The facility is located within the main Pearl Harbor Watershed, which encompasses 110 square

miles and is made of nine subwatersheds. The facility lies within the Waiawa subwatershed, which

consists of Waiawa Stream and its tributaries. Waiawa Stream partially borders Waiawa Gulch

Training Site and UTES along the southwestern boundary (Figure 1-3). Waiawa Stream drains

south to Middle Loch within Pearl Harbor, approximately 1.25 miles away, and subsequently to

the Pacific Ocean. Storm water runoff at the facility is directed towards a series of storm drains

and a seepage pit located in the southwest corner of the property, near the storage buildings. A

dry-well system formerly existed at the facility but has been capped and is no longer functional.

The seepage pit was constructed in 2019 and receives storm water discharge from the wash rack.

Facility storm drains ultimately discharge into Waiawa Stream. Specific details on the seepage pit

were not available at the time of the PA.

1.5.4 Climate

Oahu is located in the tropics, with a climate characterized by mild temperatures, northeasterly

trade winds year-round, and moderate humidity. Hawai’i has two seasons: summer (between May

and October) and winter (between October and April). The average coastal temperature is

approximately 79 degrees Fahrenheit (°F), with temperatures decreasing at higher elevations.

The coldest temperatures are in January (72°F), and the warmest temperatures are in August

(89°F). Humidity on Oahu ranges from approximately 30 to 90 percent. Precipitation

predominantly occurs when the island’s mountain masses capture and cool the rising, warm,

moist ocean air, producing higher rainfall in the windward and mountain areas and lower rainfall

in the leeward and coastal zones. Annual rainfall ranges from 20 inches in the leeward coastal

areas to 250 inches on the Koolau mountain peaks (McDonald et.al, 1983) Waiawa Gulch Training

Site and UTES has a mean annual rainfall of approximately 70 inches.

1.5.5 Current and Future Land Use

Current Waiawa Gulch Training Site and UTES operations include training and maintenance for

the various units that support the HIARNG. In addition to vehicle maintenance and support for

HIARNG, periodic training exercises and course work for the National Guard/Army Reserve units

are conducted at the facility. The facility is staffed by both full- and part-time employees.

Portions of the northern and southern borders of Waiawa Gulch Training Site and UTES are

abutted primarily by industrial land use. A junk yard abuts the northwestern boundary of the facility.

Across the road of the eastern border is a small industrial park. The closest urban center is Pearl

City, approximately 0.1 miles to east.

Reasonably anticipated future land use is not expected to change from the current land use

described above.
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Preliminary Assessment Report Waiawa Gulch Training Site and Unit Training and Equipment Site

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Preliminary Assessment Report Waiawa Gulch Training Site and Unit Training and Equipment Site

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PFAS Preliminary Assessment Report

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2. Fire Training Areas

No FTAs were identified within the facility during the PA through interviews (Appendix B),

Environmental Data Resource (EDRTM) reports (Appendix A), or from observations made during

the VSI. The personnel interviewed had institutional knowledge spanning from 1985 to present.
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3. Non-Fire Training Areas

In addition to FTAs, the PA evaluated areas where PFAS-contining materials may have been

broadly used, stored, or disposed. This may include buildings with fire suppression systems, paint

booths, AFFF storage areas, and areas of compliance demonstrations. Information on these

features obtained during the PA are included in Appendices A and B. Three non-FTAs were

identified during the PA. A description of each non-FTA is presented below, and the non-FTAs are

shown on Figure 3-1. Photographs of each non-FTA appear in Appendix C.

3.1 Storage Buildings

There are multiple storage buildings for hazardous and non-hazardous materials located on the

southern end of the facility, adjacent to the wash rack. One 55-gallon drum of 3% Ansulite AFFF

was originally located in the metal portable storage units located north of the maintenance

building. Later, the drum was moved to the right side of a hazardous materials storage building.

During the VSI, the 55-gallon drum of 3% Ansulite was still present within the hazardous materials

storage building. No leaks or releases, emergency or otherwise, have been reported or

documented from the storage containers, and no evidence of leaking was observed during the

VSI. Trench drains are located adjacent to the storage containers and the maintenance building.

These drains carry stormwater runoff flow from the maintenance building to Waiawa Stream.

3.2 Firetruck Pump Test Area

There is one firetruck located on the facility that is foam capable. According to interviewees, the

AFFF tank is kept empty and is only filled when needed. The firetruck is parked on a grassy area

east of the storage buildings. According to interviews, the pumps on the truck are tested once a

month by spraying water at a tree located within the northern portion of the facility (Figure 3-1).

During the pump testing, the firetruck is parked in the northern portion of the facility. The current

fire captain at the facility started in 2008; since that time, only water has been used for testing. It

is unknown if similar testing practices occurred prior to 2008 with the tanks filled with AFFF.

Additionally, it is not known if residual AFFF remains in the empty tanks/ pumps and is

subsequently released during the testing.

3.3 Vehicle Maintenance Facility

During interviews, it was confirmed that the firetruck was filled with 3% AFFF concentrate in the

early 2000s, and that an unknown quantity of foam was released in a large open area covered in

asphalt between the maintenance buildings adjacent to Waiahona Street. There are two storm

drains located within the reported area of release that release to Waiawa Stream. One storm drain

is located northwest of the release area, and the second is located southeast of the release area.

In addition, vehicle maintenance staff stated that portable Tri-MaxTM units filled with AFFF were

brought from HIARNG at Wheeler Army Airfield to the Waiawa Gulch Training Site and UTES

facility for nozzle testing. Interviewees stated that the nozzle testing of AFFF included discharging

an unspecified volume of foam into trash bags for disposal. It was reported that foam was not

released onto the asphalt or into the environment; however, the disposition of the reportedly

bagged discharged AFFF is unknown.
Wash

Rack

Waihona Street

Maintenance

Building

Vehicle

Maintenance

Facility

Fire Truck

Pump Test Area

Fire Truck

Parking Area

Storage

Buildings

Metal Storage

Containers

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Waiawa Stream

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Non-Fire Training Areas

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contributors, and the GIS user community

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Preliminary Assessment Report Waiawa Gulch Training Site and Unit Training and Equipment Site

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PFAS Preliminary Assessment Report

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4. Emergency Response Areas

Emergency responses to crashes sometimes require flame suppression, which may result in the

release of PFAS to the environment in the form of AFFF. No emergency response areas were

identified within the facility during the PA through interviews or EDRTM reports (Appendix A). In

the event of an emergency, the Honolulu Fire Department is called to respond. The facility

firefighting unit works to mitigate hazards prior to the arrival of the Honolulu Fire Department in

times of emergency.
PFAS Preliminary Assessment Report

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Oahu, Hawai’i

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5. Adjacent Sources

No potential off-site sources of PFAS were identified during the PA; however, fires have been

documented at the adjacent privately-owned junk yard. Interviewees noted that a large explosion

historically occurred in the 1990s at the adjacent junk yard. The explosion caused items from

within the junk yard to be projected over onto the facility property. According to interviewee’s

knowledge of the associated firefighting efforts, the fires were put out with water.
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Oahu, Hawai’i

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6. Preliminary Conceptual Site Model

Based on the PA findings, two AOIs were identified at Waiawa Gulch Training Site and UTES:

Firetruck Pump Test Area (AOI 1) and the Vehicle Maintenance Facility, Firetruck Parking Area,

and Storage Buildings (AOI 2). The following sections describe the CSM components and the

specific preliminary CSMs developed for the AOIs. The CSM identifies the three components

necessary for a potentially complete exposure pathway: (1) source, (2) pathway, and (3) receptor.

If any of these elements are missing, the pathway is considered incomplete.

In general, the potential PFAS exposure pathways 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 PFAS toxicological study (National Ground Water Association, 2018).

Receptors at Waiawa Gulch Training Site and UTES include site workers, construction workers,

trespassers, and off-facility residents. The preliminary CSM for Waiawa UTES indicates which

specific receptors could potentially be exposed to PFAS. The preliminary CSM for the AOIs at

Waiawa Gulch Training Site and UTES is shown in Figure 6-2.

6.1 AOI 1: Firetruck Pump Test Area

AOI 1 comprises a grassy area in the north portion of the facility. Because there is little knowledge

regarding historical pump testing activities, AFFF may have been released within the grassy area

where testing occurred. The AOI is an open grassy area that is used for vehicle storage and for

pump testing of the firetruck. The testing activities may have released AFFF into the grass and

potentially had surface run-off to the adjacent Waiawa Stream.

Because AFFF may have been released directly to surface soil at AOI 1, surface soil at the AOI

is considered a potentially complete pathway to site workers, construction workers, and

trespassers via ingestion and inhalation of soil particulates. PFAS may have also infiltrated from

surface soil to the subsurface, and ground-disturbing activities within the AOI may expose

construction workers to potential PFAS in subsurface soil via ingestion and inhalation.

PFAS are water soluble and can migrate readily from soil to groundwater via leaching; however, 

drinking water at Waiawa Gulch Training Site and UTES is resourced from public drinking water

wells that are located cross-gradient, approximately 0.75 miles west of AOI 1. No drinking water

wells exist at the facility, and groundwater is approximately 12 to 15 feet bgs in the area of AOI 1.

As such, groundwater is considered an incomplete pathway for site workers, construction

workers, and trespassers via ingestion. Several domestic wells exist within 1 mile downgradient

of the AOI to the south and southwest. Therefore, there is a potentially complete pathway for

groundwater to off-facility residents using private wells.

Stormwater runoff at AOI 1 is captured by storm drains that ultimately discharge into Waiawa

Stream located in the vicinity of the storage buildings. The stream flows south to Middle Loch,

within Pearl Harbor, and subsequently the Pacific Ocean. It is possible that PFAS may have been

transported to Pearl Harbor via this drainage network. As such, the pathway for PFAS exposure

via surface water and sediment to off facility residents and recreational users is considered

potentially complete. The preliminary CSM for AOI 1 is shown on Figure 6-2.

6.2 AOI 2: Vehicle Maintenance Facility, Firetruck Parking Area, and

Storage Buildings

AOI 2 comprises the southern portion of the facility that includes the vehicle maintenance facility

and surrounding areas where AFFF was discharged from the facility firetruck in the early 2000s,
PFAS Preliminary Assessment Report

Waiawa Gulch Training Site and UTES,

Oahu, Hawai’i

18

the grassy firetruck parking area, and the storage buildings on the edge of the grassy area where

AFFF has been stored. AOI 2 also includes the paved area outside the vehicle maintenance

facility where portable Tri-MaxTM units were serviced by discharging a volume of foam from the

extinguishers into plastic trash bags.

AFFF discharge and storage within AOI 2 may have resulted in the release of PFAS in grassy

areas at the firetruck parking area and the storage buildings. AFFF was also released to paved

surfaces, and may have migrated from paved surfaces to nearby grassy areas. It is also possible

that AFFF released to paved surface could have infiltrated the subsurface via cracks or joints

between paved areas.

Because AFFF may have been directly or indirectly released to grassy surfaces at AOI 2, surface

soil at the AOI is considered a potentially complete pathway to site workers, construction workers,

and trespassers via ingestion and inhalation of soil particulates. PFAS may have also infiltrated

the subsurface via infiltration through surface soil. As a result, ground-disturbing activities within

the AOI may expose construction workers to potential PFAS in subsurface soil via ingestion and

inhalation. Accidental ingestion of groundwater is considered an incomplete pathway for exposure

to PFAS during construction activities due to the depth to groundwater being an estimated 12 to

15 feet bgs.

During the VSI, two storm drains were observed on the northwest and southeast sides of the

vehicle maintenance facility release area. AFFF released to the pavement may have drained to

either of these storm drains, both of which discharge to an outfall located along Waiawa Stream.

Stormwater runoff at AOI 2 is captured by storm drains that ultimately discharge into Waiawa

Stream located in the vicinity of the storage buildings. The stream ultimately flows to the Pacific

Ocean, similarly to stormwater from AOI 1. As such, the pathway for PFAS exposure via surface

water and sediment from AOI 2 to off facility residents and recreational users is considered

potentially complete.

Groundwater pathways to receptors at AOI 2 are the same as for AOI 1, therefore, the pathway

to downgradient off-facility residents is potentially complete. Pathways-receptor relationships for

AOI 2 are illustrated in the preliminary CSM shown in Figure 6-2.
!P

!C(

!C(

!P

!P

!P

!P

A!

Waiawa 

Stream-Frontal

Pearl Harbor

Watershed

Halawa 

Stream-Frontal

Pearl Harbor

Watershed

Vehicle

Maintenance

Facility

Fire Truck

Pump Test Area

Fire Truck

Parking Area

Storage

Buildings

Metal Storage

Containers

Maintenance

Building

Waihona Street

Wash

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AOI 1

AOI 2

Waiawa Stream

Waiawa Stream

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Areas of Interest

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Earthstar Geographics, CNES/Airbus DS, USDA, USGS,

C:\Users\grace.canham\AECOM Directory\Stankevich, Michael - ARNG_PFAS_GIS_60552172\MXDs\HI\Waiawa_Figures\Fig_6-1_Waiawa_AOIs.mxd

0 1,000 2,000 500

Feet

Legend

Area of Interest

Potential PFAS Release

No Suspected Release

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Surface Water Flow Direction

Inferred Groundwater Flow Direction

Wells

!P Domestic Well

A! Monitoring Well

!C( Municipal Water Supply Well

Preliminary Assessment Report Waiawa Gulch Training Site and Unit Training and Equipment Site

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SOURCE PATHWAY RECEPTOR

AOI 1

and

AOI 2

AFFF 

releases 

during pump 

and nozzle 

testing and 

spills during 

transport and 

storage

Human 

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOI

Surface 

Water/

Sediment

Subsurface 

Soil

Groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Complete Pathway

Site 

Worker

Construction 

Worker Resident Trespasser/

Recreational User

Site 

Worker

Construction 

Worker Resident Trespasser

/ /

/ / /

LEGEND

/

Figure 6-2

Preliminary Conceptual Site Model, AOI 1

Waiawa Gulch Training Site and UTES, HI

/

/

/

/

PFAS in 

Surface Soil

Notes:

1. The resident and recreational user 

receptors refer to an off-site resident

and recreational user.

2. Dermal contact exposure pathway

is incomplete for PFAS

/ / /

/ /

/

/ /

/ /

20
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7. Conclusions

This report presents a summary of available information gathered during PA efforts on the use

and storage of AFFF and other PFAS-related activities at the Waiawa Gulch Training Site and

UTES. The PA findings are based on personnel interviews, historical documents, and the VSI

(Appendix A and Appendix B).

7.1 Findings

Two AOIs related to potential PFAS releases were identified at the Waiawa Gulch Training Site

and UTES based on PA data (Figure 7-1), and they are summarized in Table 7-1.

Table 7-1 AOIs at Waiawa Gulch Training Site and UTES

Area of Interest Name Used by Potential Release Dates

AOI 1 Firetruck Pump Test Area HIARNG Monthly testing; first date of 

testing is unknown

AOI 2 Vehicle Maintenance

Facility, Firetruck Parking,

and Storage Buildings.

HIARNG Latest known early 2000s.

Based on the known or potential PFAS release at the AOIs, there is potential for exposure to

PFAS contamination in surface soil and subsurface soil at the facility to site workers, construction

workers, and trespassers. Off facility groundwater, surface water, and sediment pathways are

potentially complete for off-facility residents and recreational users. The preliminary CSM for the

AOIs at Waiawa Gulch Training Site and UTES details the specific pathways and receptors for

the AOIs and are shown on Figures 6-2.

7.2 Uncertainty

A number of information sources were investigated during this PA to determine the potential for

PFAS-containing materials to have been present, used, or released at the facility. Historically,

documentation of PFAS use was not required because PFAS were considered benign. Therefore,

records were not typically kept by the facility or available during the PA on the use of PFAS in

training, firefighting, or other non-traditional activities, or on its disposition.

The conclusions of this PA are based on all available information, including: previous

environmental reports, EDRsTM, observations made during the VSI, and interviews. Interviews of

personnel with direct knowledge of a facility generally provided the most useful insights regarding

a facility’s historical and current PFAS-containing materials. Sometimes the provided information

was vague, such as whether AFFF was used during historical pump testing of the firetruck.

Gathered information has a degree of uncertainty due to the absence of written documentation,

the limited number of personnel with direct knowledge due to staffing changes, the time passed

since PFAS was first used (1969 to present), and a reliance on personal recollection. Inaccuracies

may arise in potential PFAS release locations, dates of release, volume of releases, and the

concentration of AFFF used. There is also a possibility the PA has missed a source of PFAS, as

the science of how PFAS may enter the environment continually evolves.

In order to minimize the level of uncertainty, readily available data regarding the use and storage

of PFAS were reviewed, current personnel were interviewed, multiple persons were interviewed

for the same potential source area, and potential source areas were visually inspected.
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Table 7-2 summarizes the uncertainties associated with the PA.

Table 7-2 Uncertainties

Location Source of Uncertainty

AOI 1 – Firetruck Pump

Test Area

Information regarding historical testing practices prior to 2008

are unknown. It is not known if AFFF were used during tests

prior to 2008, it is also unknown if residual AFFF in the firetruck

tanks/lines may have been mixed with water during recent

testing activities.

AOI 2 – Vehicle

Maintenance Facility:

Tri-MaxTM Maintenance

The exact dates, frequency, volume, and concentration of AFFF

sprayed during Tri-MaxTM nozzle testing is unknown. The fate of

the trash bags containing spent AFFF is also unknown.

AOI 2 – Vehicle

Maintenance Facility:

Firetruck Discharge

The exact dates, frequency, and volume of AFFF sprayed during

this release are unknown.

AOI 2 – Storage

Buildings

Information regarding the storage and transport of the AFFF

historically are unknown. It is unknown if any spillage occurred

during transport of the AFFF containers or during storage.

7.3 Potential Future Actions

The degree of uncertainties associated with the interviews and data collected during the PA

indicate that current or former ARNG activities may have resulted in potential PFAS releases at

the two AOIs identified during the PA. Based on the CSMs developed for the AOIs, there is

potential for receptors to be exposed to PFAS contamination in surface soil, subsurface soil, and

off-facility surface water, sediment, and groundwater at these AOIs. Table 7-3 summarizes the

rationale used to determine if the AOI should be considered for further investigation under the

CERCLA process and undergo an SI.

Table 7-3 PA Findings Summary

Area of Interest AOI Location Rationale Potential Future

Action

AOI 1 – Firetruck

Pump Test Area

21°24'20.62"N;

157°58'36.22"W

Monthly firetruck pump tests

occur in this area. AFFF has

historically been stored in

truck tanks and may have

been used during testing

prior to 2008.

Proceed to an SI; focus

on soil, groundwater,

and surface water

and/or sediment that is

discharged from the

facility

AOI 2 – Vehicle

Maintenance

Facility, Firetruck

Parking Area,

and Storage

Buildings

21°24'34.03"N;

157°58'39.10"W

Reported release of AFFF

from the firetruck and

potential incidental release

of AFFF from Tri-MaxTM

extinguisher testing at the

Vehicle Maintenance

Building. Potential releases

may have also occurred as

a result of AFFF storage in

the Firetruck Parking Area

and Storage Buildings.

Proceed to an SI; focus

on soil, groundwater,

and surface water

and/or sediment that is

discharged from the

facility
PFAS Preliminary Assessment Report

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ARNG will evaluate the need for an SI at Waiawa Gulch Training Site and UTES based on the

potential receptors, the potential migration of PFAS contamination off the facility, and the

availability of resources.
Maintenance

Building

Waihona Street

Wash Rack

Waiawa Stream

Waiawa Stream

Vehicle

Maintenance

Facility

Fire Truck

Parking Area

Fire Truck

Pump Test

Area

Storage Buildings

Metal Storage

Containers

AOI 1

AOI 2

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Summary of Findings

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8. References

Anthony, Stephen S. 1997. Evaluation of the U.S. Geological Survey Ground-Water DataCollection Program in Hawai’i, 1992.

Argonne National Laboratory. 1993. Preliminary Assessment Report for Waiawa Gulch,

Installation 15080, Pearl City, Oahu, Hawai’i. Installation Restoration Program. United States.

August.

Department of the Navy. 1990. Assessment of the Potential for Groundwater Contamination Due

to Proposed Urban Development in the Vicinity of the U.S. Navy Waiawa Shaft, Pearl Harbor,

Hawai’i. March.

Department of the Navy. 2016. Draft Environmental Assessment for Waiawa Water Transmission

Main Replacement, Pearl City, Oahu, Hawai’i. June.

Macdonald, G. A., A. T. Abbott, and F. L. Peterson. 1983. Volcanoes in the Sea, The Geology of

Hawai’i. 2nd ed. Honolulu: Univ. of Hawai’i Press.

Mink, J. F., and L. S. Lau. 1990. Aquifer Identification and Classification for Oahu: Groundwater

Protection Strategy for Hawai’i. Revised. Tech. Report No. 179. Honolulu: Univ. of Hawai’i, Water

Resources Research Center. February.

National Ground Water Association, 2018. Groundwater and PFAS: State of Knowledge and

Practice. January.

Sherrod, D.R, Sinton, J. M., Watkins, S. E., and Brunt, K. M., 2007. Geologic Map of the State of

Hawai‘i, Sheet 3 — Island of O‘ahu. US Geological Survey, Sheet 3 of 8, scale 1:100,000,

https://pubs.usgs.gov/of/2007/1089/Oahu_2007.pdf.

United States Environmental Protection Agency (USEPA). 1991. Guidance for Performing

Preliminary Assessments under CERCLA. EPA/540/G-91/013. September 1991.