FINAL 

Preliminary Assessment Report

Silver Bell Army Heliport

Marana, Arizona

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

SBAH, Marana, AZ

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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 ................................................................................... 7

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

1.5.2 Hydrogeology ................................................................................................. 8

1.5.3 Hydrology ..................................................................................................... 10

1.5.4 Current and Future Land Use ....................................................................... 11

1.5.5 Climate ......................................................................................................... 11

2. Fire Training Areas ........................................................................................................... 15

2.1 Building L4650 - Exterior ......................................................................................... 15

2.2 Building L4603 ........................................................................................................ 15

2.3 Building L4600 - Exterior ......................................................................................... 16

2.4 Building L4300 ........................................................................................................ 17

2.5 Building L4320 - Exterior ......................................................................................... 18

3. Non-Fire Training Areas ................................................................................................... 20

3.1 Building L4650 ........................................................................................................ 20

3.2 Building L4603 ........................................................................................................ 20

3.3 Building L4600 ........................................................................................................ 20

3.4 Building L4300 ........................................................................................................ 21

3.5 Building L4320 ........................................................................................................ 21

3.6 Building L4601 ........................................................................................................ 22

3.7 Building L4605 ........................................................................................................ 23

4. Emergency Response Areas ............................................................................................ 26

5. Adjacent Sources ............................................................................................................. 28

5.1 Pinal Airpark............................................................................................................ 28

5.2 Evergreen Air Center .............................................................................................. 28

5.3 I-10 Accident Response .......................................................................................... 28

6. Preliminary Conceptual Site Model .................................................................................. 30

6.1 AOI 1 Building L4320 ............................................................................................. 30

6.2 AOI 2 Building L4300 ............................................................................................. 31

6.3 AOI 3 Northeastern Boundary Release Locations ................................................... 32

6.4 AOI 4 Alpha, Bravo, and Charlie Rows.................................................................... 33

7. Conclusions ..................................................................................................................... 37

7.1 Findings .................................................................................................................. 37

7.2 Uncertainties ........................................................................................................... 37

7.3 Potential Future Actions .......................................................................................... 39

8. References ...................................................................................................................... 41
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

ii

Figures

Figure ES-1 Summary of Findings

Figure ES-2 

Figure 1-1 

Figure 1-2 

Figure 1-3 

Figure 2-1 

Figure 3-1 

Figure 4-1 

Figure 5-1 

Figure 6-1 

Figure 6-2 

Figure 7-1 

Preliminary Conceptual Site Model, Silver Bell Army Heliport

Facility Location

Groundwater Features

Surface Water Features

Fire Training Areas

Non-Fire Training Areas

Emergency Response Areas

Adjacent Sources

Areas of Interest

Preliminary Conceptual Site Model AOI 1, AOI 2, AOI 3, and AOI 4

Summary of Findings

Tables

Table ES-1 AOIs at SBAH

Table 1-1 On- and Off-Facility Wells at SBAH

Table 3-1 PFAS Releases at Building L4605

Table 7-1 AOIs at SBAH

Table 7-2 Uncertainties within the PA

Table 7-3 PA Findings Summary

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
PFAS Preliminary Assessment Report

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Acronyms and Abbreviations

AASF

AC

ADEMA

Army Aviation Support Facility

Aircraft

Arizona Department of Emergency and Military Affairs

ADEQ Arizona Department of Environmental Quality

ADWR Arizona Department of Water Resources

AECOM AECOM Technical Services, Inc.

AFFF Aqueous Film Forming Foam

AFRC Armed Forces Reserve Center

AMA Active Management Area

amsl Above Mean Sea Level

AOI Area of Interest

ARNG Army National Guard

ASLD Arizona State Land Development

AZ Arizona

AZARNG Arizona Army National Guard

AZNG Arizona National Guard

bgs Below Ground Surface

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CFR Code of Federal Regulations

CSM Conceptual Site Model

EDRTM Environmental Data Resources, Inc.TM

FEMA Federal Emergency Management Agency

ft Feet

FTA Fire Training Area

JLUS Joint Land Use Study

NGWA National Ground Water Association

NOAA National Oceanic and Atmospheric Administration

NRCD Natural Resource Conservation District

NRCS National Resource Conservation Service

PA Preliminary Assessment

PFAS Per- and Poly-fluoroalkyl Substances

PFOA Perfluorooctanoic Acid

PFOS Perfluorooctanesulfonic Acid

SBAH

SI

Silver Bell Army Heliport

Site Inspection

UCMR3 Unregulated Contaminant Monitoring Rule 3

US United States

USACE United States Army Corps of Engineers

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

USGS United States Geological Survey
PFAS Preliminary Assessment Report

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iv

VSI Visual Site Inspection

WAATS Western Army National Guard Aviation Training Site

WWTP Waste Water Treatment Plant
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

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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 Arizona ARNG (AZARNG) Silver Bell Army

Heliport (SBAH) (also referred to as the “facility”), near the town of Marana, Arizona, to assess

potential PFAS release areas and exposure pathways to receptors. 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 9 November 2018 and completed visual site inspections (VSIs) at

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

disposed.

· Interviewed current and former SBAH personnel including the SBAH Deputy and Assistant

Deputy Chief, Former Fire Chief, SBAH Site Safety Officer, and SBAH Plant Supervisor

during the site visit.

· Identified Area(s) of Interest (AOIs) and developed a preliminary conceptual site model (CSM)

to summarize potential source-pathway-receptor linkages of potential PFAS in soil,

groundwater, surface water, and sediment for each AOI.

Four AOIs related to PFAS releases were identified at SBAH during the PA. The AOIs are shown

on Figure ES-1 and described in Table ES-1 below. The preliminary CSM for SBAH is presented

in Figure ES-2.

Table ES-1: AOIs at SBAH

Area of

Interest Name Used by Assumed Release Dates^

AOI 1 Building L4320 AZARNG 2009 - 2018

AOI 2 Building L4300 AZARNG 1985 – 1994; 2006 - 2009

AOI 3 Northeastern Boundary Release

Locations AZARNG 2004, 2007, 2011, 2017,2018

AOI 4 Alpha, Bravo, Charlie Rows AZARNG 2003/2004,

^ In many instances, actual release dates were not available. The release dates have been assumed based on

occupancy and use of the building.

Interviews with SBAH staff whose first-hand knowledge of the facility span 1994 to present

indicate that AZARNG activities at SBAH have contributed PFAS contamination to the

environment through means of fire-training, fire suppression system releases, maintenance

activities, equipment storage, and responses to fuel spills. Based on known AFFF releases at the

AOIs listed above, there is potential for exposure to PFAS contamination in media at or near the

facility. A summary of PA findings is shown on Figure ES-1. The summary preliminary CSM

diagram for SBAH is shown on Figure ES-2.
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The USEPA Unregulated Contaminant Monitoring Rule 3 (UCMR3) data indicate that

PFOS/PFOA were not detected in a public water system above the USEPA lifetime Health

Advisories within a 20-mile radius of the facility. 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.
AOI 2 Building L4300

AOI 1 Building L4320

AOI 3 Northeastern

Boundary Release Locations

AOI 4 Alpha, Bravo,

and Charlie Rows

Building L4710

0 300 600 1,200

Feet

Legend

Area of Interest

Potential PFAS Release (FTAs,

Non-FTAs, and Emergency

Response Areas)

Facility Boundary

Summary of Findings

Figure ES-1

CLIENT

REVISED

SCALE

9/15/2020 MS

BL

9/15/2020

9/15/2020

ARNG

GIS BY

CHK BY

TITLE

PROJECT Preliminary Assessment for PFAS at Silver Bell Army Heliport, AZ

C:\Users\stankevichm\OneDrive - AECOM Directory\ARNG_PFAS_GIS_60552172\MXDs\AZ\Silver_Bell_Figures\Silver_Bell_PA_Figures\Fig_ES-1_SilverBell_Summary.mxd

PM RG 9/15/2020

1:7,200 ­ 12420 Milestone Center Drive

Germantown, MD 20876

Base Map: Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS,

USDA, USGS, AeroGRID, IGN, and the GIS User Community

3
Media 

SOURCE PATHWAY RECEPTOR

AOI 1, AOI 2, 

AOI 3 and 

AOI 4

Fire training, 

AFFF storage 

areas, and fire 

suppression 

system releases

PFAS in 

Surface Soil 

and Gravel 

Landscaping

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ 

Infiltration

Airborne Soil 

Particulate

Surface Soil

Sediment / 

Temporary 

Surface 

Water

Subsurface 

Soil

Groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current / Future

Flow-Chart Continues

Partial / Possible Flow

Incomplete Pathway

Potentially Complete Pathway

Complete Pathway

Site 

Worker

Construction 

Worker Resident Trespasser

Site 

Worker

Construction 

Worker Resident Trespasser

LEGEND

/

Figure ES-2

Preliminary Conceptual Site Model

Silver Bell Army Heliport

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

/ /

/ /

/ / /

/ / /

Ingestion / / /

/

/

/

/

Surface 

Water Flow

PFAS in 

Intermittent 

Surface 

Water 

(Stormwater 

Network)

/

/

4
PFAS Preliminary Assessment Report

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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 Perfluorooctanesulfonic acid (PFOS) and Perfluorooctanoic

acid (PFOA) 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-12-D-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), primarily releases of aqueous film forming

foam (AFFF) released as part of firefighting activities, although other sources of PFAS are

possible. In addition, the ARNG is 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 PFAS compounds

in the environment varies. The US Environmental Protection Agency (USEPA) issued lifetime

Drinking Water Health Advisories for PFOA and PFOS in May 2016, but there are currently no

promulgated national standards regulating PFAS. In the absence of federal standards for PFAS

in any environmental media, some states have adopted their own drinking water standards for

PFAS; the state of Arizona does not currently have promulgated standards for PFAS in any

environmental media.

This report presents the findings of a PA for PFAS-containing materials at the Arizona ARNG

(AZARNG) Silver Bell Army Heliport (SBAH) (also referred to as the “facility”), near the town of

Marana, Arizona, 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 documents the locations where PFAS may have been released into the environment at

SBAH. 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 9 November 2018 and completed visual site inspections (VSIs) at

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

disposed.
PFAS Preliminary Assessment Report

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· Interviewed current and former SBAH personnel during the site visit including the SBAH

Deputy and Assistant Deputy Chief, Former Fire Chief, SBAH Site Safety Officer, and SBAH

Plant Supervisor.

· Identified Area(s) of Interest (AOIs) and developed a preliminary conceptual site model (CSM)

to summarize potential source-pathway-receptor linkages of potential PFAS in soil,

groundwater, surface water, and sediment for each AOI.

1.3 Report Organization

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

Preliminary Assessments under CERCLA (1991 USEPA). 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 potential or suspected FTAs at the facility

identified during the site visit

· Section 3 – Non-Fire Training Areas: describes other locations of potential or suspected

PFAS releases at the facility identified during the site visit

· Section 4 – Emergency Response Areas: describes areas of suspected or potential AFFF

release at the facility, specifically in response to emergency situations

· Section 5 – Adjacent Sources: describes sources of PFAS release adjacent to the facility

that are not under the control of ARNG

· Section 6 – Preliminary Conceptual Site Model: describes the pathways of PFAS transport

and receptors at the facility

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

SBAH is approximately 170 acres of land located 2.85 miles west of Interstate 10 and northeast

of East Pinal Air Park Road, which is north of the city of Marana in Pinal County, Arizona (Figure

1-1).

SBAH is located north of Pinal Airpark, which was constructed as the Marana Army Airfield in

1942. After World War II, the Airfield was deeded to Pinal County. The Airfield was a flying school

and a base for covert Central Intelligence Agency air operations. Later, the Airfield became known

as the Pinal Airpark. Since 1979, tenants at the Pinal Airpark have provided passenger and cargo

services along with aircraft maintenance, storage, reconfiguration, and reclamation services.

Today, the primary occupant of the Airpark is Evergreen Air Center, which serves as a “boneyard”

for civilian commercial aircraft, as well as airliner storage, reconfiguration, and reclamation.
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Undeveloped desert landscape bounds SBAH to the west, north, and east. SBAH is largely

developed with buildings, roads, and an airfield.

The land occupied by SBAH was conveyed by the US to the state of Arizona in 1913. In 1983,

161 acres of land were patented by the Arizona State Land Department (ASLD) to the Arizona

Department of Emergency and Military Affairs (ADEMA) for SBAH. By 1987, an armory and an

Army aviation support facility (AASF) (L4600) had been constructed on SBAH property. In 2005,

ADEMA leased 565 acres of land surrounding SBAH from ASLD (AZARNG, 2005; AZARNG,

2010). By 2010, SBAH had over 300,000 square feet (ft) of office space, hangars, and storage

facilities (AZARNG, 2010).

1.5 Facility Environmental Setting

SBAH is located in the central Tucson Basin, within the Basin and Range physiographic province,

a landscape of the interior western US that is dominated by mountain ranges separated by broad

alluvial valleys (Thornbury, 1965). The facility lies within the Yuma Desert portion of the Sonoran

Desert region of Arizona at an elevation of about 1,893 ft above mean sea level (amsl). The

Tortolita Mountains to the east, Tucson Mountains to the west, and the Picacho Mountains to the

north rise to elevations of about 4,000 to 4,500 ft amsl. Local, unnamed, intermittent washes drain

west to the Santa Cruz River, which is about 2 miles southwest of the facility. The Santa Cruz

River flows intermittently, except in short stretches fed by reclaimed effluent from wastewater

treatment plants (WWTP). During prehistoric times, and as late as the beginning of the twentieth

century, the river was a much more reliable source of surface water or shallow groundwater (URS,

2008).

Topographic variability in the region creates environmental zones with varying resources (Fish et.

al, 1985; Goodyear, 1975; Minckley and Brown, 1982). In the valley bottom, the Santa Cruz River

was once a reliable source of water, and the floodplain and adjacent terraces had arable land. A

variety of grasses and cacti covered the lower bajadas (alluvial fans), and paloverde-mixed cacti

communities, rich in saguaro and other edible cacti, grew on the upper bajadas and around

mountain bases. Washes radiating out of the mountains had distinctive xeroriparian vegetation

communities that crossed the bajadas. The mountains had diverse woodland and grassland

environments that supported deer and other large mammals and were a source of rocks for flaked

and ground stone tools; the mountains also had springs that provided water. Natural vegetation

has been eliminated from the adjacent developed areas of SBAH and Pinal Air Park (URS, 2008).

1.5.1 Geology

Soil information was obtained from the Web Soil Survey website maintained by the Natural

Resources Conservation Service of the US Department of Agriculture (National Resource

Conservation Service [NRCS], 2015). Using this tool, soil on the facility was identified as “Denure

sandy loam, 1 to 3 percent slopes.” (NRCS, 2015). Denure sandy loams are deep, somewhat

excessively drained soil found on fan terraces. The Denure sandy loams formed in fan alluvium

derived from mixed sources. This soil unit is used as rangeland agriculture (Natural Resource

Conservation District [NRCD], 1991).

SBAH is located within the Upper Santa Cruz Sub-Basin of the Tucson Basin. This Basin contains

undivided Quaternary surficial deposits consisting of valley fill or alluvium varying up to 12,000 ft

in thickness. The alluvium varies in constitution from dense sand, gravel, and cobble deposits to

silts and clays. In many areas, deposits of heavily cemented sandy clay and clayey sand (caliche)

are encountered (AZARNG, 2005).
PFAS Preliminary Assessment Report

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The alluvium and rock of the Tucson Basin include three major units that form a single, unconfined

aquifer: Fort Lowell Formation, Tinaja Beds, and Pantano Formation. The Fort Lowell Formation,

which comprises the upper 300 to 400 ft, provides most of the groundwater that is withdrawn from

the basin. This Formation includes interbedded silt, sand, and gravel. The Tinaja Beds underlie

the Fort Lowell Formation and are separated from the Fort Lowell Formation by an aquitard. The

Tinaja Beds are comprised of a layer of sand and gravel underlain by gypsiferous clayey silt and

mudstones. The Pantano Formation underlies the Tinaja Beds at depths of several thousand ft in

the central portion of the Basin. The Pantano Formation is a reddish-brown silty sandstone that

overlies bedrock (AZARNG, 2005).

1.5.2 Hydrogeology

SBAH is located within the Tucson Active Management Area (AMA) aquifers. The main aquifer in

this area is the Fort Lowell Formation. Groundwater in the vicinity of SBAH flows to the northwest.

Depth to groundwater ranged from 200 to 300 ft below ground surface (bgs) during 1994-1995

and is suspected to be influenced by surface water infiltration from nearby irrigated fields

(Hammet, 1995). The area is characterized by very little direct recharge to groundwater due to

very low annual rainfall.

Beginning in the 1970s, many municipalities required stormwater to be retained and disposed

onsite at newly developed commercial or industrial properties. Depending upon specific

development and drainage conditions, drywells were a common method used to dispose of

stormwater. Drywells are regulated under the Safe Drinking Water Act. The Arizona Department

of Environmental Quality (ADEQ) maintains a searchable database of drywells (ADEQ, 2019).

The following registration numbers and names are associated with drywells at SBAH (ADEQ,

2019):

· 52217 (6 wells) – Silver Bell Flood Mitigation

· 45031 (4 wells) – Silver Bell WWTP Upgrade

· 44460 (1 well) – Silver Bell Airfield at AFRC [Armed Forces Reserve Center]

· 45659 (1 well) – AZ Army National Guard – AFRC

· 8563 (1 well) – Silver Bell Armory HO 1st BN 285th

Six drywells are located within the stormwater drainage ditches along the northeastern property

line, installed as flood mitigation. Four drywells are located within the northwestern cell of the

wastewater retention basin, installed as part of the WWTP upgrade. Three other registered

drywells exist on-facility, two associated with the AFRC and one associated with the Armory, for a

total of 13 drywells registered with ADEQ at SBAH.

According to the Arizona Department of Water Resources (ADWR) well registry and the EDRTM

report, there are five groundwater wells within 1-mile of SBAH (ADWR, 2019; Appendix A). Two

wells are on-facility, and the remaining three are off-facility. The wells are described in Table 1-1

below.
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Table 1-1: On- and Off-Facility Wells at SBAH

Registration

Number Owner

Location/Dire

ction from

SBAH

Geographical

Center

Well

Depth

(ft bgs)

Water

Level

(ft

bgs)

Use Pump Rate

(gpm)

OnFacility/

OffFacility

55-213034

Arizona

Emergency

& Military

Affairs

Department

~0.49 miles SE 610 200 Mixed Unknown Onfacility

55-507748 Div Military

AFF-AZ ~0.20 miles E 610 230 Mixed 80 Onfacility

55-577144 Evergreen

Air Center

~0.70 miles

WSW 250 220 Monitor

N/A Offfacility

55-615698

(co-located

with 55-

618728)

Arizona

State Land

Department

~0.60 miles N 400 219 Mixed 5

Offfacility

55-618728

(co-located

with 55-

615698)

Arizona

Board of

Regents

~0.60 miles N 400 300 Mixed Unknown Offfacility

Notes:

N = north

E = east

SE = southeast

WSW = west-southwest

gpm = gallons per minute

N/A = Not Applicable

SBAH has two groundwater extraction wells: 55-213034 and 55-507748. The former is located

on the southeastern installation boundary, under the overhead protection (L4503) and behind the

FMO South facility (L4512), and the latter is located east of the former fire station, Aircraft (AC)

Maintenance Hangar, and surrounding area (L4300) and south of WAATS Hangar (L4525)

(Figure 1-2). Groundwater from these wells is used for potable drinking water, fire suppression,

irrigation, and activities related to the mission. Groundwater extraction rates provided by ADWR

are available from 1984 to 2015 for well 55-507748.The average annual extracted groundwater

between 2011 and 2015 was 16.6 acre-ft (5,409,126 gallons).

The USEPA Unregulated Contaminant Monitoring Rule 3 (UCMR3) data indicate that

PFOS/PFOA were not detected in a public water system above the USEPA Health Advisories

within a 20-mile radius of the facility. 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.

Geologic, groundwater, and surface water features interact with and influence one another, and

as such are all shown on Figure 1-2.
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1.5.3 Hydrology

SBAH is within the city of Marana-Santa Cruz River watershed, which consists of approximately

58 square miles of the Lower Santa Cruz watershed in Pinal and Pima Counties. The watershed

lies within a flat plain and includes a drainage area that is predominantly undisturbed desert. The

facility is located on a broad, flat, alluvial fan east of the Santa Cruz River. The area is

characterized by a low-energy erosional environment stabilized by large creosote bushes and

mesquite trees (Harris Group Inc, 2004).

The surface topographic gradient near the facility is less than 15 ft per mile to the west-northwest.

The nearest significant natural drainage feature, the Santa Cruz River, is located approximately

2 miles west of SBAH (US Geological Survey [USGS], 1996). The nearest wetland is located 1.75

miles west-southwest of SBAH. This wetland is categorized as a “freshwater forested/shrub

wetland” (US Fish and Wildlife Service [USFWS], 2015).

SBAH is located in Zone X, according to data from the Federal Emergency Management Agency’s

Flood Map Service Center. Zone X is defined as, “areas of 0.2% annual chance flood; areas of 

1% chance annual flood with average depth of less than 1 foot or with drainage areas less than

1 square mile; and areas protected by levees from 1% annual chance flood.”. A floodplain is

located approximately 0.75 mile west of SBAH. This floodplain is characterized as a, “special flood

hazard areas subject to inundation by the 1% annual chance flood.” (Federal Emergency

Management Agency [FEMA], 2015).

There are no naturally occurring surface water features at SBAH (Figure 1-3). Surface water

collecting features at SBAH include the following:

· A two-celled wastewater retention basin located in the northwestern corner of SBAH; and

· A stormwater retention basin located in the northwestern corner of SBAH, adjacent to the west

of the wastewater retention basin.

SBAH contains several locations where surface runoff and stormwater are collected and

ultimately diverted to the stormwater retention basin in the northwestern corner of the facility.

These features generally run along the northeastern, northwestern, southwestern, and

southeastern perimeter of SBAH. The stormwater collection system is closed, and collected water

does not cross SBAH property boundaries. Collected water is removed from SBAH by a

combination of evaporation and infiltration.

SBAH has a WWTP (L4710) capable of treating approximately 100,000 gallons per day that is

located in the southern point of the base (VERSAR, 2010). The WWTP (L4710) was built in 2008

and came online in 2010. The WWTP (L4710) discharges to a two-celled wastewater retention

basin located in the northwestern corner of the SBAH, adjacent and to the east of the stormwater

retention basin. Effluent from the WWTP (L4710) is discharged to the northwestern-most cell,

which contains five drywells that transport the water to the subsurface for infiltration. Wastewater

flow is contained within the bounds of SBAH property, although waste sludge produced by the

WWTP (L4710) is removed from SBAH property and disposed of at an approved waste facility,

as required (ADEMA, 2015).

The stormwater and wastewater retention basins are located in the northwestern corner of SBAH

(Figure 1-3). The geographic coordinates at the approximate center of the stormwater basin are

32°31’25.0” N; 111°20’18.8” W. The geographic coordinates at the approximate center of the

wastewater retention basins are 32°31’29.3” N; 111°20’17.3” W and 32°31’27.7” N; 111°20’15.4”

W for the northern and southern cells, respectively. According to aerial photographs, the
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

11

stormwater retention basin has existed at SBAH since approximately June 1996. The wastewater

retention basins were constructed between August 2006 and June 2007.

The stormwater retention basin is approximately 286,625 square ft and does not have an outlet,

therefore, captured stormwater remains within SBAH property boundaries. The northern and

southern wastewater retention basin cells are approximately 47,000 square ft each. The drywells

located within the wastewater retention basins direct reclaimed WWTP effluent into the shallow

subsurface.

The stormwater retention basin and drainage network receive all of the stormwater and run-off

generated from within the SBAH boundary. The water is removed from the network via surface

infiltration and evaporation. According to the 2018 EDRTM report, SBAH site topography has an

elevational change of approximately 12 ft across the facility from north to south (1865 to 1877 ft

amsl) and an elevational change of approximately 32 ft across the facility from west to east (1856

to 1888 ft amsl) (EDRTM, 2018). The facility’s topological features suggest surface water would

flow to the northwest, towards the stormwater retention basin located in the northwestern corner

of the facility.

1.5.4 Current and Future Land Use

At the time of this report, Pinal County, in conjunction with the Arizona National Guard (AZNG), is

conducting a Joint Land Use Study (JLUS). The Pinal County JLUS is a collaborative effort

between the military and surrounding communities working to promote compatible and

sustainable growth within Pinal County, while simultaneously preserving the mission of the AZNG

(Pinal County, 2018). The current land use of SBAH is specifically designated by Pinal County as

“Airport Reserve”, with the functions being industrial/military. The Pinal Airpark and SBAH lie

within Pinal County’s Red Rock Growth Area, as outlined in the county’s Comprehensive Plan,

with the objective of facilitating mixed use development and a diverse economic center in southern

Pinal County (Pinal County, 2015). The future land use of SBAH is not proposed for change.

1.5.5 Climate

SBAH is located within the Sonoran Desert, which has a warm steppe climate characterized by

low precipitation and high evapotranspiration rates. Precipitation varies depending on location

over the course of a year, but the region is generally arid, and the Tucson Basin receives only

about 12 inches of precipitation annually. Summer rainfall (June through August) accounts for 30

to 60 percent of the yearly precipitation, while winter rains and occasional snow account for 10 to

40 percent of the annual total (Sellers and Hill, 1974) (URS, 2008). The maximum average

monthly temperature in nearby Eloy, AZ occurs in July (105.7degrees Fahrenheit [°F]), with an

average maximum annual temperature of 87.7 °F. The minimum average monthly temperature

occurs in December (35.2 °F), with an average minimum annual temperature of 53.5 °F (National

Oceanic and Atmospheric Administration [NOAA], 2019). The average annual precipitation in

Eloy, AZ from 1971-2000 was 10.60 inches (NOAA, 2019).
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2. Fire Training Areas

FTAs are considered areas where fire training events deliberately using AFFF or other fire-fighting

materials resulted in a release to the environment. This excludes separate areas where the

deliberate discharge of AFFF for disposal or maintenance purposes occurred, and those areas

are discussed in Section 3. Five FTAs were identified during the PA (Figure 2-1). These include

the Singapore Hangar (L4650), a Wash Rack and Drain (L4603) located to the southeast of the

Singapore Hangar (L4650), the AASF #2 hangar (L4600), the former fire station driveway, AC

Maintenance Hangar and Surrounding Area (L4300), and the current fire station (L4320) driveway

and surrounding area also located along the southeastern apron border. Available photographs

of the FTAs are presented in Appendix C. A discussion of the five FTAs identified is presented

below.

2.1 Building L4650 - Exterior

The Singapore Hangar (L4650) is located in the northern corner of SBAH and directly south of

the fuel farm (Figure 2-1). The geographic coordinates at the approximate center of the hangar

structure are 32°31’31.1” N; 111°20’01.5” W. The Singapore Hangar (L4650) was constructed in

2009 and supports joint operations between US forces and visiting international forces.

SBAH personnel stated that fire training activities occur in front of the building. According to

interviewees, the last training in this area was in October 2018. The area used for fire training is

assumed to be along the concrete apron on the south side of the Singapore Hangar (L4650).

Fire training performed annually at this FTA consists of discharging AFFF from one to two TriMaxTM mobile fire extinguishers, per event, at small objects set ablaze. Tri-MaxTM solution is

directly sprayed onto the concrete apron and is not contained using booms or similar products.

After training, Tri-MaxTM solution is washed away using water. AFFF sprayed during training may

travel to the stormwater retention basin, the landscaping gravel planter adjacent to the concrete

apron, and/or the wash rack drain located approximately 75 ft southeast of the Singapore Hangar

(L4650) apron.

The Singapore Hangar (L4650) has landscaping gravel along the northeastern perimeter, asphalt

paving along the southeastern perimeter, a concrete apron and landscaping gravel along the

southwestern perimeter, and asphalt paving along the northwestern perimeter. Stormwater

drainage features are not located in the immediate area of the facility, and the nearest drainage

feature is a small, singular retention basin located approximately 300 ft to the west. The retention

basin does not have any outlets and has one inlet located on the southeast side (in the direction

of the Singapore Hangar [L4650]). Additional information regarding activities not associated with

fire training at the Singapore Hangar (L4650) are discussed further in Section 3.1

2.2 Building L4603

The Wash Rack and Drain (L4603) is located between the Singapore Hangar (L4650) and the

AASF #2 (L4600). The geographic coordinates at the approximate center of the Wash Rack and

Drain (L4603) structure are 32°31’38.8” N; 111°20’00.8” W. Aerial photographs indicate the Wash

Rack and Drain (L4603) has been in operation since 2003. Though the intended purpose of the

Wash Rack and Drain (L4603) is for daily use of vehicle cleaning operations, the Aviation Life

Support Equipment Supervisor stated during interviews that the Wash Rack and Drain (L4603)

may have occasionally been used for fire training with Tri-MaxTM mobile fire extinguishers.
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Fire training is believed to have occurred on the tarmac near the Wash Rack and Drain (L4603),

allowing discharged AFFF to be washed down the drain. The type of training performed on the

tarmac near the Wash Rack and Drain (L4603) is similar to that performed at the Singapore

Hangar (L4650), where one to two Tri-MaxTM mobile fire extinguishers would be used to extinguish

small fires per event.

The Wash Rack and Drain (L4603) is covered only by a shade canopy. The ground surface at the

Wash Rack and Drain (L4603) is a concrete extension of the AASF #2 (L4600) apron. The surface

is sloped inward to a singular drain, allowing for liquid removal via piping directed to the WWTP

(L4710). The Wash Rack and Drain (L4603) has asphalt along the northwest and southwest

perimeters, concrete along the southeast perimeter, and bare earth to the northeast. The nearest

stormwater feature to the Wash Rack and Drain (L4603) is the singular retention basin

approximately 400 ft east-northeast.

Although the Wash Rack and Drain (L4603) has a drain directing fluids to the WWTP (L4710), it

is possible that environmental releases of PFAS have occurred at the Wash Rack and Drain

(L4603) due to cracks and/or leaks in the surface concrete or drainage piping to the WWTP

(L4710). Furthermore, depending on the location of fire training exercises performed at the Wash

Rack and Drain (L4603), the unpaved area to the northeast may have been exposed to liquids

containing PFAS.

Additional information regarding activities not associated with fire training at the Wash Rack and

Drain (L4603) is further described in Section 3.2.

2.3 Building L4600 - Exterior

AASF #2 (L4600) is located along the northeastern boundary of the SBAH and directly southeast

of the Singapore Hangar (L4650) and Wash Rack and Drain (L4603) (Figure 2-1). The geographic

coordinates at the approximate center of AASF #2 (L4600) are 32°31’26.4” N; 111°19’56.3” W.

Aerial photographs indicate that AASF #2 (L4600) was constructed in 1995 and supports SBAH

AZARNG operations. There are three fire suppression systems among eight bays within AASF

#2 (L4600). SBAH personnel stated during interviews that annual fire training with one to two TriMaxTM training mobile fire extinguishers per event occurred annually on the asphalt southwest of

the concrete apron at AASF #2 (L4600) until several years ago; the timeframe in which annual

training occurred is unknown.

Depending on the exact location of fire training at AASF #2 (L4600), AFFF may have discharged

southeast towards a stormwater drainage ditch located southeast of the apron.

AASF #2 (L4600) has a concrete apron to the southwest along the building’s perimeter, bare earth

and asphalt along the northwest perimeter, an asphalt road and bare earth along the northeastern

perimeter, and bare earth bounded by an asphalt paved parking lot along the southeastern

perimeter. The nearest stormwater features are a drainage ditch located approximately 300 ft

northeast and the singular retention basin located approximately 650 ft northwest from the AASF

#2 (L4600), respectively. Additionally, the Wash Rack and Drain (L4603) (Section 2.2, Section

3.2) is located approximately 250 ft west-northwest of the AASF #2 (L4600). There is also a

singular drain associated with a spill pad (L4622) located approximately 400 ft south-southeast of

the AASF #2 (L4600).

Additional information regarding activities not associated with fire training at AASF #2 (L4600) is

further described in Section 3.3.
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2.4 Building L4300

The former fire station driveway, AC Maintenance hangar, and surrounding area (L4300) are

located along the southeastern border of the tarmac and consist of a long asphalt driveway with

gravel planters on either side of the driveway. The former fire house occupies a small space in

the northern most portion of the AC Maintenance hangar (L4300) (Figure 2-1). There is a shade

canopy directly in front of the former fire house along the driveway. The driveway is approximately

100 ft long, 35 ft wide, and the approximate geographic coordinates of the center are 32°31’17.8”

N; 111°19’56.3” W. This portion of the AC Maintenance hangar (L4300) previously operated as a

fire station between 1985 to 1994, then again from 2006 to 2009. This portion of the building is

currently used as classrooms for SBAH personnel. The building was not equipped with a fire

suppression system and did not have floor drains. Fire training activities and equipment inspection

were performed on the driveway and within the surrounding gravel areas.

SBAH personnel stated that foaming occurs in the former FTA area during significant rainfall. TriMaxTM mobile fire extinguishers were discharged and refilled semi-annually at the former fire

station (L4300) during its use as an FTA, but the exact timeframe of fire training there is unknown,

although it likely coincides with the operation as a fire station (1985 -1994; 2006 – 2009). Fire

training and maintenance activities ceased at FTA when the fire station was relocated to the

current fire station (L4320). Training at the former fire station (L4300) involved using one to two

mobile Tri-MaxTM units to extinguish small fires per event. Training is believed to have occurred

on the building driveway.

The former fire station driveway, AC Maintenance hangar, and surrounding area (L4300) are

surrounded predominantly by unpaved areas and landscaping gravel and conjoins with the AC

Maintenance hangar (L4300) to the southwest and an asphalt driveway to the northwest

(Appendix C, photographs number 1-3). The asphalt driveway connects to the asphalt tarmac

and is surrounded by areas of landscaping gravel. An asphalt paved parking lot is located beyond

the bare earth to the southeast. The nearest stormwater feature is approximately 175 ft to the

east of the geographic center of the former fire station driveway. The gravel area on either side of

the driveway directs drainage to either the northeast or southwest of the building. This stormwater

drainage feature is connected to the SBAH-wide drainage channel, and flow within this feature

ultimately deposits into the stormwater retention basin located in the northwestern corner of SBAH

(Figure 3-1). The landscaping gravel on either side of the driveway is without vegetation and is

slightly lower in elevation than the driveway.

Based on visual inspection and descriptions of the fire training and maintenance activities, PFAS

releases to the environment at the former fire station driveway, AC Maintenance hangar, and

surrounding area (L4300) have occurred within the asphalt driveway and surrounding landscaping

gravel. It is possible that sufficient rainfall may cause ponding in the area, allowing PFAS overflow

from the landscaping gravel to the stormwater feature to the east. Additionally, inspection of aerial

photos of this area suggests that water from the gravel areas routinely overflows to the northeast

drainage ditch. There is an observable flow channel through the gravel and a linear stain feature

on the asphalt to the drainage channel.

Additional information regarding activities not associated with fire training at the former fire station

driveway, AC maintenance hangar and surrounding area (L4300) are discussed further in Section

3.4
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2.5 Building L4320 - Exterior

The current fire station (L4320) is located approximately 350 ft southwest of the AC Maintenance

Hangar (L4300) (Section 2.4), along the southeastern border of the tarmac (Figure 2-1). The

current fire station (L4320) consists of a large building, an asphalt and gravel driveway, and

surrounding bare earth and landscaping gravel planters. The driveway is approximately 90 ft long,

60 ft wide, and the geographic coordinates of the approximate center are 32°31’14.6” N;

111°19’59.6” W. The building is equipped with a fire suppression system and has three drains in

each one of its three bays (9 drains in total). The SBAH utility map indicates these drains connect

to the WWTP (L4710). Fire training was performed in front of the current fire station and within

the surrounding gravel areas at the current fire station.

Potential AFFF releases to the environment are suspected to have occurred in this area due to

fire training activities.

Training occurred outside and in front of the current fire station (L4320). The former Fire Chief at

Marana Army Airfield stated during interviews that one to two Tri-MaxTM units were used monthly

for fire training purposes. Fire training activities at the current fire station (L4320) began when it

became operational in 2009 until late in 2018.

The nearest stormwater feature to the current fire station (L4320) is approximately 50 ft to the

west of the geographic center of the fire station driveway (Appendix C, photograph number 5).

This stormwater feature acts as a basin for tarmac run-off in the southern portion of SBAH. The

basin is split into two portions by an asphalt and gravel driveway and hydrologically connected

via a culvert beneath the asphalt and gravel driveway. This stormwater drainage feature is

connected to the SBAH-wide drainage channel, and flow within this feature is directed along the

western property boundary to ultimately discharge into the stormwater retention basin located in

the northwestern corner of SBAH (Figure 2-1). The landscaping gravel on the eastern side of the

driveway is without vegetation and is slightly lower in elevation than the driveway. The stormwater

basin to the west of the current fire station (L4320) driveway is sparsely vegetated with tall grass

and is slightly lower in elevation than the fire station driveway.

Based on historical fire training, the current fire station (L4320) driveway and surrounding area

FTA includes the entire length of the asphalt and gravel driveway, the immediate areas of

landscaping gravel on either side of the driveway, and in front of the current fire station (L4320)

building where the fire training activities occurred. PFAS releases to the environment in this area

occurred within the asphalt and gravel driveway and surrounding landscaping gravel. PFAS

released on the driveway and the landscape gravel may have infiltrated the subsurface via the

stormwater drainage feature located within the stormwater collection basin to the west of the fire

station.

Additional information regarding activities not associated with fire training at the current fire station

driveway (L4320) is discussed further in Section 3.5.
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3. Non-Fire Training Areas

In addition to the FTAs, the PA evaluated areas where PFAS-containing 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. The PA site visit identified

seven non-FTAs where AFFF was intentionally or unintentionally released to the environment: the

Singapore Hangar (L4650), the Wash Rack and Drain (L4603), AASF #2 (L4600), the former fire

station driveway, AC maintenance hangar, and surrounding area (L4300), the current fire station

(L4320), the former fire station (L4601), and the Western Army National Guard Aviation Training

Site (WAATS) Maintenance Hangar (L4605). Non-FTAs are shown on Figure 3-1. Available

photographs of each non-FTA identified during the PA are presented in Appendix C.

3.1 Building L4650

The fire suppression system within the Singapore Hangar (L4650) was initially tested following

the hangar’s construction in 2009. The foam filled about 6 feet high within the hangar bays and

was pushed out the door towards the tarmac and allowed to evaporate. According to SBAH

personnel, the Singapore Hangar (L4650) fire suppression system has been tested annually since

then by a contractor, though no releases have occurred. The contractor states that all additional

annual testing has been performed without releases, and that samples are pulled directly from

the bladder.

Based on visual inspection and descriptions of the maintenance activities, PFAS releases to the

environment at the Singapore Hangar (L4650) could have occurred. The initial test release could

have reached the spill pad drain and/or the stormwater drainage ditch. The location of Singapore

Hangar (L4650) is depicted on Figure 3-1.

3.2 Building L4603

Various types of helicopters, wheeled vehicles, and large aircraft parts are washed at the Wash

Rack and Drain (L4603). Additionally, SBAH personnel stated with confidence during interviews

that helicopters covered with AFFF were washed at the Wash Rack and Drain (L4603) during a

release of the fire suppression system at AASF #2 (L4600).

Although the Wash Rack and Drain (L4603) has a drain directing fluids to the WWTP (L4710), it

is possible that environmental releases of PFAS have occurred at the Wash Rack (L4603) due to

cracks and/or leaks in the surface concrete or drainage piping to the WWTP (L4710). The location

of the Wash Rack and Drain is depicted on Figure 3-1.

3.3 Building L4600

The fire suppression system at AASF #2 (L4600) has been triggered on multiple occasions,

resulting in releases of AFFF. SBAH personnel indicated that the automatic fire suppression

system was unintentionally triggered in 2004 and 2007. The fire suppression system pipes leaked

AFFF to the floor of the AASF #2 (L4600) in 2004. The AFFF was mopped up using a Zamboni

and pushed towards a trench drain that extends the entire length of building L4600. The spill pad

drain and the hangar trench drain transported fluids to a former retention pond where Singapore

Hangar (L4650) is located. In 2007, AFFF solution filled the fire riser room due to a malfunction; 

the solution was directed to the asphalt roads and unpaved areas northeast of AASF #2 (L4600),

leaking out of the Paint Room and Machine Room. It is unclear if the solution reached the
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stormwater drainage ditch. Additionally, the volume of AFFF released during both unintentional

fire suppression system trigger events is unknown.

Based on visual inspection and descriptions of the maintenance activities and unintentional

releases from the fire suppression system, PFAS were released to the environment at AASF #2

(L4600). The releases could have reached the spill pad drain, the former retention pond, and/or

the stormwater drainage ditch, as described above. The location of AASF #2 is depicted on Figure

3-1.

3.4 Building L4300

In addition to the fire training that occurred at the former fire station driveway, AC maintenance

hangar, and surrounding area (L4300), Tri-MaxTM maintenance and recharge were performed

along the driveway and in the landscaping gravel adjacent to the driveway. The maintenance and

recharge included discharging the contents of the Tri-MaxTM units onto the ground surface and

replacing the Tri-MaxTM solution via a 5-gallon bucket. Based on the description of these activities,

the Tri-MaxTM maintenance area is considered to be the entire length of the asphalt driveway and

the immediate areas of landscaping gravel on either side of the driveway.

Based on visual inspection and descriptions of the maintenance activities, PFAS releases to the

environment at the former fire station, AC Maintenance hangar, and surrounding area (L4300)

have occurred within the asphalt driveway and surrounding landscaping gravel. It is possible that

sufficient rainfall may cause ponding in the area, allowing PFAS overflow from the landscaping

gravel to the stormwater feature to the east. The location of the former fire station driveway, AC

maintenance hangar, and surrounding area (L4300) is depicted on Figure 3-1.

3.5 Building L4320

In addition to the fire training that occurred at the current fire station (L4320), equipment storage,

Tri-MaxTM storage, and equipment maintenance all occurred in this area. Fire equipment

inspections were performed on the driveway and within the surrounding gravel and sparsely

vegetated areas at the current fire station driveway and surrounding areas (L4320). Additionally,

Tri-MaxTM mobile fire extinguishers and other AFFF equipment are currently stored along the

western edge of the driveway (Appendix C, photograph number 4).

The current fire station (L4320) maintains six firefighting vehicles as well as equipment designed

to suppress aircraft fires. In addition, firefighting equipment and materials are stored on unpaved

areas adjacent to a CONEX box approximately 90 ft south of the geographic center of the fire

station driveway (Figure 3-1). The approximate geographic coordinates of the storage area are

32°31’13.6” N; 111°19’59.7” W. The 500 square ft storage area is unsheltered. Firefighting

materials have been stored in this area since 2009. Several Tri-MaxTM units, ladders, fire

extinguisher canisters, compressed gases, and hoses are stored in this area. Materials are stored

on the ground between a chain-link fence and the metal CONEX box (Appendix C, photograph

number 8). Potential AFFF releases to the environment are suspected to have occurred in this

area due to leaks from Tri-MaxTM units, fire extinguishers, and material canisters located in the

storage area. The total volume of stored AFFF materials at the current fire station (L4320) is

generally between three to five 55-gallon drums at any one time.

Maintenance and storage activities at the current fire station (L4320) began when the current fire

station (L4320) became operational in 2009 until late in 2018. Tri-MaxTM maintenance and

recharge are performed along the driveway and on the landscaping gravel on the side of the

driveway. These activities included discharging the contents of the Tri-MaxTM onto the ground
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surface and replacing the Tri-MaxTM solution via a 5-gallon bucket. According to SBAH personnel,

for more than 12 years, the contractor changed the solution in the Tri-MaxTM units every six

months. The process of decommissioning Tri-MaxTM units included drilling holes in the old units

and dumping the solution in the unpaved area southwest of the current fire station (L4320). SBAH

personnel approximated 100 units per year were dumped in this area.

Vehicles containing AFFF are also maintained and stored within the bays at the current fire station

(L4320). Maintenance activities of these vehicles consist of nozzle testing and spraying, purging

and refilling AFFF storage on vehicles along with washing and servicing of fire trucks and other

similar activities. Vehicles are refilled with AFFF using a pump. According to SBAH personnel,

AFFF leaked from a fire truck within the fire house and drained through the bay floor drain. The

date of this leak and volume of AFFF released is unknown.

The nearest stormwater feature to the current fire station (L4320) is approximately 50 ft to the

west of the geographic center of the fire station driveway. The grassy/gravel area directs drainage

either northeast or southwest of the building, where it flows into the main surface water collection

system. This stormwater feature acts as a basin for tarmac run-off in the southern portion of

SBAH. The basin is split into two portions by an asphalt and gravel driveway and hydrologically

connected via a culvert beneath the asphalt and gravel driveway. This stormwater drainage

feature is connected to the SBAH-wide drainage channel, and flow within this feature is directed

along the western property boundary to ultimately discharge into the stormwater retention basin

located in the northwestern corner of SBAH (Figure 4-1). The landscaping gravel on the eastern

side of the driveway is without vegetation and is lower in elevation than the driveway. The

stormwater basin to the west of the current fire station (L4320) driveway is sparsely vegetated

with tall grass and is slightly lower in elevation than the fire station driveway.

Based on historical maintenance and equipment storage activities at the current fire station

(L4320), PFAS releases to the environment in this area occurred within the asphalt and gravel

driveway and surrounding landscaping gravel and fire station. PFAS released on the driveway

and the landscape gravel may have infiltrated the subsurface via the stormwater drainage feature

located within the stormwater collection basin to the west of the fire station, where it would then

travel to the stormwater retention basin, and then infiltrate groundwater. Any PFAS released within

the fire station were likely removed via the bay drains that direct fluids to the on-site WWTP

(L4710) and ultimately the WWTP (L4710) retention ponds.

3.6 Building L4601

The SBAH former fire station (L4601) is located between the AASF #2 Hangar (L4600) and

WAATS Hangar (L4605) (Figure 3-1). The geographic coordinates at the approximate center of

the former fire station (L4601) are 32°31’25.3” N; 111°19’55.3” W. Historical aerial imagery

suggests that the former fire station (L4601) was constructed in 1994 and was used as a fire

station until 2006. Activities associated with the maintenance and storage of firefighting equipment

were conducted within this facility while it operated as a fire station.

According to SBAH personnel, the former fire station (L4601) did not have a fire suppression

system or drains. Although unverified, PFAS releases may have occurred at the former fire station

(L4601) during its operational years as a fire station based on common activities performed at

other SBAH fire stations, such as the maintenance and storage of firetrucks. It is therefore

assumed that potential AFFF releases at the former fire station (L4601) would have entered the

environment through the spill pad drain and the building’s surrounding areas.
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In June 2003, the fire station (L4601) was surrounded by unpaved areas to the northwestern,

northeastern, and southeastern perimeter, and surrounded by asphalt on the southwestern

perimeter. Currently, the fire station (L4601) is surrounded by asphalt on all sides with the

exception of small unpaved areas on the northwestern and northeastern perimeters. These

unpaved areas are approximately 13 ft wide. The asphalt on the southwestern perimeter of the

fire station (L4601) directly connects to the asphalt tarmac. The nearest stormwater feature is a

spill pad (L4622) approximately 150 ft southwest from the geographic center of the building. The

spill pad (L4622) is a concrete pad with a drain below the ground surface that leads to the WWTP.

3.7 Building L4605

The WAATS Hangar (L4605) is located along the northeastern boundary of SBAH and directly

southeast of AASF #2 (L4600) and the former fire station (L4601) (Figure 3-1). The geographic

coordinates at the approximate center of the WAATS Hangar (L4605) are 32°31’23.3” N;

111°19’52.3” W. Historical aerial photographs indicate the WAATS Hangar (L4605) was

constructed between 2004 and 2005. The WAATS Hangar at (L4605) has 10 bays and is equipped

with a multi-zone fire suppression system. PFAS releases at the WAATS Hangar (L4605) are

depicted in Table 3-1 below.

Table 3-1: PFAS Releases at Building L4605

SBAH personnel stated during interviews that the automatic fire suppression system at the

WAATS Hangar (L4605) unintentionally released AFFF in 2011, April 2017, May 2018, and July

2018. The release in 2011 occurred in the back (northeast) portion of the WAATS Hangar (L4605).

The volume of AFFF released is unknown. The released AFFF likely migrated northeast, along

the asphalt, towards bare earth behind the WAATS Hangar (L4605). The April 2017 and July 2018

releases occurred in the fire riser room at the rear (northeast) of the WAATS Hangar (L4605). A

seal within the fire suppression system failed and caused the fire riser room to fill with AFFF

(Appendix C, photographs number 12-15 for the 2017 event, and photographs number 16-21 for

the 2018 event). The volumes of AFFF released during the April 2017 and July 2018 releases are

unknown.

The May 2018 release occurred during a fire system check conducted at the WAATS Hangars

(L4605). The fire suppression system was deactivated; however, one riser remained activated

Date of Release Location of Release Cause of Release Volume of Release

April 2011 Northeast (Back) Unintentional Unknown

April 2017 Fire Riser Room,

Northeast (Back)

Seal in fire

suppression

system failed

Unknown

May 2018

“Old Paint Booth”

Sheet Metal Shop,

Northeast (Back)

Accident due to

mislabel during fire

suppression

system check

Unknown

July 2018 Fire Riser Room,

Northeast (Back)

Seal in fire

suppression

system failed

Unknown
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due to improper labeling. When the system was tested, the “old paint booth” riser activated and

filled the room with AFFF, though it was no longer the paint booth at that moment, as it was used

as the sheet metal shop. The volume of AFFF released is unknown. According to SBAH

personnel, the release was squeegeed out, washed out, and pushed out to the gravel area

northeast of the building.

The WAATS Hangar (L4605) has a concrete apron along the southwest perimeter, asphalt along

the northwestern and northeastern perimeter, and an unpaved area along a portion of the

northeastern corner and southeastern perimeter. Bare earth follows the asphalt further to the

northeast of the WAATS Hangar (L4605). The nearest stormwater feature(s) are approximately

325 ft to the northeast and southeast of the geographic center of the WAATS Hangar (L4605).

Both of these stormwater drainage features are connected to the SBAH-wide drainage channel,

and flow within these features will ultimately deposit into the stormwater retention basin located

in the northwestern corner of the SBAH (Figure 3-1). In addition, the spill pad (L4622) is located

approximately 350 ft west-northwest of the geographic center of the WAATS Hangar (L4605).

It is presumed that PFAS entered the environment in the unpaved areas to the northeast of the

WAATS Hangar (L4605) as a result of these AFFF releases. Depending on the magnitude of the

releases and rainfall following the events, PFAS may have also migrated to the stormwater feature

to the northeast and to the stormwater retention basin. Possible staining was identified during the

site visit in the bare earth area to the northeast.
Building L4603

Building L4601

Building L4605

Building L4650

Building L4600

Building L4230

Building L4300

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Feet

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Facility Boundary

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4. Emergency Response Areas

Emergency response locations are often considered potential PFAS release areas because AFFF

is commonly used to extinguish crash flames. According to SBAH staff, no crashes or unplanned

fires resulting in AFFF use have occurred at SBAH during their tenure; however, two crashes at

the adjacent Marana Army Airfield were described during interviews. These crashes are discussed

in Section 5.

AFFF is commonly used to extinguish aviation fuel-related fires. Several fuel spills have occurred

on the tarmac at SBAH. AFFF was used to control a fire or fire-potential at spills in the Alpha,

Bravo, Charlie rows of the tarmac southwest of the AASF #2/WAATS Hangar. The Charlie row

spill was speculated by staff to have occurred in 2003 or 2004. The timeframe of the Alpha/Bravo

row spill is unknown, though SBAH personnel stated that the asphalt had to be replaced due to

the extent of the spill. The volume of AFFF used in response to both events is unknown, and spill

records were unavailable during the site visit. Emergency release areas are shown on Figure 4-

1.

Tri-MaxTM units are stored on the facility between each aircraft on the ramp for use during

emergency response. At the time of the VSI, 58 Tri-MaxTM units were on the ramp, with a historical

maximum total of up to 100 units. The Tri-MaxTM units have been used at SBAH since 2002 or

2003. Prior to this, large carbon dioxide containers were used for fire suppression on the ramp,

though they were not stored on the ramp.
Alpha Row

Bravo Row

Charlie Row

0 300 600 1,200

Feet

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Potential PFAS Release

Facility Boundary

Emergency Response Areas

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5. Adjacent Sources

Several known and suspected sources of PFAS, not under the control of AZARNG, have been

identified within 1 mile of SBAH. These sources include firefighting response to fuel-related spills

and fires on Pinal Airpark. The potential adjacent sources are described below, and their locations

are presented on Figure 5-1.

5.1 Pinal Airpark

According to the 2018 EDRTM report, the center of the Pinal Airpark located approximately 0.5

miles east-southeast of SBAH property boundary (EDRTM, 2018). Prior to World War II, the Pinal

Airpark was the Marana Army Airfield. It is unknown whether AFFF were stored in fire suppression

systems at the Airpark; however, SBAH staff stated during interviews that AFFF has been used

during emergency responses along the runway at the Airpark, and releases at Pinal Airpark may

impact the groundwater under portions of SBAH. Two incidents have occurred in which AFFF was

used at the Airpark:

· A Boeing 747 aircraft caught fire on the Airpark property, approximately 900 ft southsoutheast of the current SBAH fire station (L4320). The date of this fire is unknown, but staff

confirmed that AFFF was used to extinguish the flames. The volume of AFFF released in

response to the fire is unknown, and response records were unavailable for this PA. The

approximate location of the Boeing 747 fire is presented on Figure 5-1.

· A fuel spill on the Airpark property approximately 4,650 ft southeast of the current fire station

(L4320). AFFF was used to control the spill and prevent potential conflagration. The date of

this incident is unknown, and the volume of AFFF released in response to the spill is unknown.

The approximate location of the fuel spill is presented on Figure 5-1.

5.2 Evergreen Air Center

According to the 2018 EDRTM report, the Evergreen Air Center is located approximately 0.4 miles

southeast of the SBAH property boundary (EDRTM, 2018). The Evergreen Air Center is the

primary occupant of Pinal Airpark, which provides airplane maintenance services and storage for

non-military aircraft (Turnbull, 2005). It is unknown whether AFFF were ever used at Evergreen

Air Center, or if emergency responses using AFFF have occurred at the location. The Evergreen

Air Center is included in this section because airplane maintenance and storage facilities

commonly use AFFF fire suppression systems and/or use AFFF to address aviation fuel-related

fires.

5.3 I-10 Accident Response

According to SBAH personnel, the SBAH fire department has responded to multiple tanker truck

fires and crash incidents on I-10 over the years. It was reported that foam was deployed during

these emergency responses, although information related to exact locations of response along

with the quantity and frequency of AFFF released were unavailable.
747 Fire

Fuel Spill

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Adjacent Sources

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Feet

Legend

I-10 Accident Response is not

mapped due to uncertainty

of the location.

Potential PFAS Release

Facility Boundary

747 Fire

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6. Preliminary Conceptual Site Model

Based on the findings of this PA, four AOIs have been identified at SBAH: AOI 1 Current Fire

Station (L4320), AOI 2 Former Fire Station Driveway, AC Maintenance Hangar, and Surrounding

Area (L4300), AOI 3 Northeastern Boundary Release Locations (which encompasses the

Singapore Hangar [L4650], Wash Rack and Drain [L4603], AASF #2 [L4600], Former Fire Station

[L4601], and WAATS Hangar [L4605]), and AOI 4 Alpha, Bravo, and Charlie rows. An AOI can be

the location of a single known or suspected PFAS release or a group of closely related releases

on a facility. Off-facility releases are not categorized as AOIs but are noted in the preliminary CSM

if there is a potential to impact receptors on the facility. A preliminary CSM is provided for each

AOI with a unique set of sources/pathways/receptors. If the preliminary CSM is identical for

multiple AOIs, then they are shown on one diagram. The AOI locations are shown on Figure 6-1.

The following sections describe the CSM components for each AOI identified. Each preliminary

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.

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 [NGWA], 2018). The receptors for the SBAH AOIs include personnel, onsite

construction workers, trespassers, and nearby residents. The preliminary CSMs for each AOI

discussed indicate which specific receptors could potentially be exposed to PFAS.

6.1 AOI 1 Building L4320

AOI 1 is the current fire station (L4320). Fire training activities described in this area involved

setting small materials ablaze and extinguishing the flames using a Tri-MaxTM mobile fire

extinguisher. Training is believed to have occurred in front of the current fire station (L4320).

Maintenance activities of vehicles containing AFFF that also occur here may include nozzle

testing, purging and refilling of AFFF storage on vehicles, and other maintenance activities. SBAH

personnel also noted an AFFF leak from a firefighting truck to the bay floor drains. Additionally,

firefighting equipment and materials are stored on bare earth adjacent to the fire station to the

south.

The current fire station (L4320) is surrounded by bare earth and landscaping gravel on all

perimeter sides with the exception of a concrete and asphalt driveway to the southeast and an

asphalt and gravel driveway to the northwest. A stormwater feature is located approximately 50 ft

to the west of the geographic center of the fire station driveway and acts as a basin for tarmac

run-off in the southern portion of SBAH. It is possible that AFFF releases during fire training

exercises or discharge of expiring AFFF may have resulted in PFAS contamination to surface soil

at the AOI. There is limited vegetation in this area, indicating possible fugitive dust emissions are

not mitigated by natural surface cover. Therefore, the pathway for potential exposure to PFAS

contamination via inhalation of dust particles or ingestion of surface soil during construction or

maintenance is considered potentially complete at the AOI. Additionally, these dust particles can

travel off-facility, therefore, the pathway for potential exposure to PFAS contamination to residents

is considered potentially complete.

PFAS are water soluble and can migrate readily from soil to groundwater or surface water via

leaching and run-off. Due to this nature, PFAS impacts may migrate from the initial release area

via surface water mobilization and be redeposited as surface water infiltrates or evaporates.
PFAS Preliminary Assessment Report

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Surface water from precipitation will partly evaporate and infiltrate in areas with permeable surface

soils. PFAS released on the driveway and the landscape gravel may have infiltrated the

subsurface via the stormwater drain located within the stormwater collection basin to the west of

the fire station. Any PFAS released within the fire station was likely removed via the bay drains

which direct fluids to the on-site WWTP (L4710) and ultimately the WWTP (L4710) retention

ponds.

SBAH receives potable water from two groundwater extraction wells (55-213034 and 55-507748).

Extraction well 55-213034 is located in the southeastern corner of SBAH, and extraction well 55-

507748 is located east of the AC Maintenance Hangar (L4300) and south of WAATS Hangar

(L4525). As such, the pathway for PFAS in groundwater for SBAH facility staff as well as potential

facility trespassers is considered potentially complete. Additionally, private wells exist off-facility

and down-gradient to the north. Therefore, the pathway for PFAS exposure in drinking water to

off-facility receptors is potentially complete. Depth to groundwater at SBAH is observed at

approximately 200 ft bgs or deeper. Infiltrating water impacted with PFAS may take a prolonged

time before impacting the regional aquifer where groundwater is drawn. In addition, the amount

of rain observed at SBAH also limits the volume of water that infiltrates the subsurface.

It is possible that AFFF releases across this area may have resulted in PFAS transport to the

SBAH stormwater network. Precipitation on paved surfaces will generally flow overland or be

collected by the facility’s stormwater network, where it is ultimately discharged to the stormwater

retention basin in the northwestern corner of SBAH. Therefore, facility staff and construction

workers may be exposed to surface water, and therefore also potentially sediment, at the facility

during periods when standing or flowing water exists, or when construction workers make

modifications to the drainage system; however, the frequency of significant rain events is low in

Arizona. Exposure via surface water and sediment are limited to times when sufficient rain is

falling, which can at times result in standing water at site drainages and the stormwater retention

basins.

Ground-disturbing activities to subsurface soil at AOI 1 could result in construction worker

exposure to potential PFAS contamination via inhalation of dust particles or ingestion of

subsurface soil in the unpaved areas surrounding the current fire station (L4320). Additionally,

dust particles could potentially migrate off the facility, which could result in potential PFAS

contamination via inhalation by nearby residents. Therefore, the exposure pathways for these

receptors are potentially complete. The preliminary CSM diagram for AOI 1 is shown on Figure

6-2.

6.2 AOI 2 Building L4300

AOI 2 is the former fire station driveway, AC Maintenance Hangar, and surrounding area (L4300).

Tri-MaxTM mobile fire extinguishers were discharged and refilled semi-annually at the former fire

station for an unspecified timeframe during its operation. Based on descriptions of the fire training

and maintenance activities, PFAS have been released to the environment within the asphalt

driveway and surrounding landscaping gravel.

The former fire station driveway, AC Maintenance Hangar, and surrounding area (L4300) is

surrounded predominantly by bare earth and landscaping gravel; it conjoins with the AC

Maintenance hangar (L4300) to the southwest and an asphalt driveway to the northwest. It is

possible that AFFF that was released at the AOI may have resulted in PFAS contamination to

surface soil at the AOI. Like AOI 1, this area is not vegetated, indicating possible fugitive dust

emissions are not mitigated by natural surface cover. Therefore, the pathway for potential

exposure to PFAS contamination to SBAH staff and construction workers via inhalation of dust
PFAS Preliminary Assessment Report

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32

particles or exposure to surface soil during construction or maintenance is considered potentially

complete. Additionally, these dust particles can travel off-facility, therefore the pathway for

potential exposure to PFAS contamination to residents is considered potentially complete. The

existence of AFFF in the area is further evidenced by foaming during significant rainfall. Significant

rainfall may cause ponding in the area and overland flow from the landscaping gravel to the

stormwater feature to the east.

Due to the presence of dry wells, PFAS may be transported to the subsurface and into

groundwater. As such, the pathway for PFAS in groundwater to facility staff and construction

workers as well as potential facility trespassers is considered potentially complete. The presence

of private wells north and downgradient from SBAH also signifies that the pathway for PFAS

exposure to off-facility receptors via drinking water is potentially complete.

It is possible that AFFF releases across this area have resulted in PFAS transport to the SBAH

stormwater network. Precipitation on paved surfaces will generally flow overland or be collected

by the facility’s stormwater network infrastructure, where it is ultimately discharged to the

stormwater retention basin in the northwestern corner of SBAH. Therefore, facility staff and

construction workers may be exposed to surface water, and therefore also potentially sediment,

at the facility during periods when standing or flowing water exists at the facility; however, the 

frequency of significant rain events is low in Arizona. Exposure via surface water and sediment

are limited to times when sufficient rain is falling and, therefore, reduces the exposure potential

of site and construction workers to near negligible.

Ground-disturbing activities to subsurface soil at AOI 2 could result in construction worker

exposure to potential PFAS contamination via inhalation of dust particles or ingestion of

subsurface soil in the bare earth areas surrounding the former fire station driveway, AC

Maintenance Hangar, and surrounding area (L4300) or during drainage system modification work.

Additionally, dust particles could potentially migrate off the facility, which could result in potential

PFAS contamination via inhalation by nearby residents. Therefore, the exposure pathways for

these receptors are potentially complete. The preliminary CSM diagram for AOI 2 is shown on

Figure 6-2.

6.3 AOI 3 Northeastern Boundary Release Locations

AOI 3 consists of the Singapore Hangar (L4650), the Wash Rack and Drain (L4603), AASF #2

(L4600), the former fire station (L4601), and the WAATS Hangar (L4605). Fire training using

mobile Tri-MaxTM fire extinguishers resulted in AFFF releases at the Singapore Hangar (L4650),

the Wash Rack and Drain (L4603), AASF#2 (L4600), and the former fire station (L4601).

Additionally, fire suppression systems have released AFFF at AASF #2 (L4600) and the former

fire station (L4601).

AOI 3 includes three adjacent large buildings along the northeast SBAH property boundary with

the large concrete apron to the southwest. Bare earth exists along northeastern perimeters of the

buildings with the exception of the Singapore Hangar (L4650), which is bounded by landscaping

gravel along its northeastern perimeter.

AFFF releases during fire training activities at the Singapore Hangar (L4650) and AASF #2

(L4600) likely occurred on the concrete apron and surrounding areas (including the concrete spill

pad [L4622] and Wash Rack and Drain [L4603]). AFFF that was released from the fire suppression

system at AASF #2 (L4600) was directed towards asphalt roads and bare earth areas northeast

of the hangar. AFFF releases during fire training activities at the former fire station (L4601) were

likely captured and drained to the WWTP (L4710); however, it is possible the surrounding area
PFAS Preliminary Assessment Report

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may have been impacted by AFFF. AFFF released by the fire suppression system at the WAATS

Hangar (L4605) likely migrated towards bare earth east-northeast and entered the drainage

system.

AFFF released at buildings across this AOI may have resulted in PFAS contamination to surface

soil at. None of these locations have vegetation, indicating possible fugitive dust emissions are

not mitigated by natural surface cover. Therefore, the pathway for potential exposure to PFAS

contamination to SBAH staff and construction workers via inhalation of dust particles or exposure

to surface soil during construction or maintenance is considered potentially complete. Additionally,

these dust particles can travel off-facility, therefore the pathway for potential exposure to PFAS

contamination to residents is considered potentially complete.

It is possible that AFFF releases across this area may have resulted in PFAS transport to the

SBAH stormwater network. Precipitation on paved surfaces will generally flow overland or be

collected by the facility’s stormwater network infrastructure, where it is ultimately discharged to

the stormwater retention basin in the northwestern corner of SBAH. Therefore, facility staff and

construction workers may be exposed to surface water, and therefore also sediment, at the facility

during periods when standing or flowing water exists at the facility; however, the frequency of 

significant rain events is low in Arizona. Exposure via surface water and sediment are limited to

times when sufficient rain is falling and, therefore, reduces the exposure potential of site and

construction workers to near negligible.

PFAS may have also been transported to subsurface soil and groundwater via dry wells in the

SBAH stormwater network. Because drinking supply wells exist at the facility, the pathway for

PFAS in groundwater to facility staff and construction workers as well as potential facility

trespassers is potentially complete. Additionally, private wells exist off-facility and downgradient

to the north. Therefore, the pathway for PFAS exposure in drinking water to off-facility receptors

is potentially complete.

Ground-disturbing activities to subsurface soil at AOI 3 could result in construction worker

exposure to potential PFAS contamination via inhalation of dust particles or ingestion of

subsurface soil in the unpaved areas across the AOI. Additionally, dust particles could potentially

migrate off the facility, which could result in potential PFAS contamination via inhalation by nearby

residents. Therefore, the exposure pathways for these receptors are potentially complete. The

preliminary CSM diagram for AOI 3 is shown on Figure 6-2.

6.4 AOI 4 Alpha, Bravo, and Charlie Rows

AOI 4 is the area surrounding Alpha, Bravo, and Charlie Rows on the tarmac. Emergency

response activities described in this area involved response to aviation fuel-related spills.

Historically, AFFF was used on each of these three rows to control fire or fire-potential at fuel

spills.

AOI 4 is located just northwest of AOIs 1 and 2, and southwest of AOI 3; AOI 4 is surrounded by 

other paved areas, unpaved areas, and landscaping gravel. Like AOIs 2 and 3, this area is not

vegetated, indicating possible fugitive dust emissions are not mitigated by natural surface cover.

Therefore, the pathway for potential exposure to PFAS contamination to SBAH staff and

construction workers via inhalation of dust particles or exposure to surface soil during construction

or maintenance is considered potentially complete. Additionally, these dust particles can travel

off-facility, therefore, the pathway for potential exposure to PFAS contamination to residents is

considered potentially complete.
PFAS Preliminary Assessment Report

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It is possible that AFFF releases across this area may have resulted in PFAS transport to the

SBAH stormwater network. Precipitation on paved surfaces will generally flow overland or be

collected by the facility’s stormwater network infrastructure, where it is ultimately discharged to

the stormwater retention basin in the northwestern corner of SBAH. Therefore, facility staff and

construction workers may be exposed to surface water, and therefore also potentially sediment,

at the facility during periods when standing or flowing water exists at the facility; however, the 

frequency of significant rain events is low in Arizona. Exposure via surface water and sediment

are limited to times when sufficient rain is falling and, therefore, reduces the exposure potential

of site and construction workers to near negligible.

PFAS may have also been transported to subsurface soil and groundwater via dry wells in the

SBAH stormwater network. Because drinking supply wells exist at the facility, the pathway for

PFAS in groundwater to facility staff, construction workers, and trespassers is potentially

complete. Additionally, private wells exist off-facility and downgradient to the north. Therefore, the

pathway for PFAS exposure in drinking water to off-facility receptors is potentially complete.

Ground-disturbing activities to subsurface soil at AOI 4 could result in construction worker

exposure to potential PFAS contamination via inhalation of dust particles or ingestion of

subsurface soil in the unpaved areas within and surrounding the Alpha, Bravo, and Charlie Rows.

Therefore, the exposure pathways for these receptors are potentially complete. The preliminary

CSM diagram for AOI 4 is shown on Figure 6-2.
A!

A!

A!

A!

A!

A!

A!

A!

A! 

A!

A!

AOI 2 Building L4300

AOI 1 Building L4320

AOI 3 Northeastern

Boundary Release Locations

AOI 4 Alpha, Bravo,

and Charlie Rows

 Building L4710

747 Fire

Fuel Spill

Evergreen Air Center

City of

Marana-Santa Cruz

River Watershed

Town of Avra

Watershed

Double Tank

Watershed

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Areas of Interest

Base Map: Source: Esri, Maxar, GeoEye, Earthstar

Geographics, CNES/Airbus DS, USDA, USGS,

C:\Users\stankevichm\OneDrive - AECOM Directory\ARNG_PFAS_GIS_60552172\MXDs\AZ\Silver_Bell_Figures\Silver_Bell_PA_Figures\Fig_6-1_SilverBell_AOIs.mxd

0 650 1,300 2,600

Feet

Legend

Area of Interest

Potential PFAS Release

(FTAs, Non-FTAs,

Emergency Response

Areas, and Adjacent

Sources)

Facility Boundary

Canal/Ditch

Surface Water Flow

Direction*

Inferred Groundwater

Flow Direction

A! Well

* indicates generalized surface water flow over facility; not intended to depict

localized surface water flow off of paved surfaces into the stormwater network.

35
Media 

SOURCE PATHWAY RECEPTOR

AOI 1, AOI 2, 

AOI 3 and 

AOI 4

Fire training, 

AFFF storage 

areas, and fire 

suppression 

system releases

PFAS in 

Surface Soil 

and Gravel 

Landscaping

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ 

Infiltration

Airborne Soil 

Particulate

Surface Soil

Sediment / 

Temporary 

Surface 

Water

Subsurface 

Soil

Groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current / Future

Flow-Chart Continues

Partial / Possible Flow

Incomplete Pathway

Potentially Complete Pathway

Complete Pathway

Site 

Worker

Construction 

Worker Resident Trespasser

Site 

Worker

Construction 

Worker Resident Trespasser

LEGEND

/

Figure 6-2

Preliminary Conceptual Site Model

AOI 1, AOI 2, AOI 3 and AOI 4

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

/ /

/ /

/ / /

/ / /

Ingestion / / /

/

/

/

/

Surface 

Water Flow

PFAS in 

Intermittent 

Surface 

Water 

(Stormwater 

Network)

/

/

36
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

37

7. Conclusions

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

storage of AFFF and other PFAS-related activities at SBAH. The PA findings are based on

personnel interviews, environmental investigations and reports, historical documents, and the VSI

(Appendix A, Appendix B, and Appendix C).

7.1 Findings

Four AOIs related to PFAS releases were identified at SBAH during the PA. The AOIs are shown

on Figure 7-1 and described below in Table 7-1.

Table 7-1: AOIs at SBAH

Area of Interest Name Used by Assumed Release

Dates^

AOI 1 Building L4320 AZARNG 2009 - 2018

AOI 2 Building L4300 AZARNG 1985 – 1994; 2006 -

2009

AOI 3 Northeastern Boundary Release

Locations AZARNG 2004, 2007, 2011,2017, 2018

AOI 4 Alpha, Bravo, Charlie Rows AZARNG 2003/2004

^ In many instances, actual release dates were not available. The release dates have been assumed based on

occupancy and use of the building.

The AOIs are locations where AFFF releases to the environment at SBAH occurred via fire

training, fire suppression system releases, maintenance activities, equipment storage, and

responses to fuel spills. Based on known AFFF releases at the AOIs listed above, there is potential

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

SBAH is shown in Figure 6-2, which presents the potential receptors and media impacted.

7.2 Uncertainties

A number of information sources were reviewed and evaluated during this PA to determine the

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

Historically, documentation of AFFF usage 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 AFFF in training, firefighting, 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. 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.
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

38

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

of PFAS were reviewed, current and former SBAH personnel were interviewed, and the majority

of potential source areas were visually inspected.

Table 7-2 summarizes the uncertainties associated with the PA:

Table 7-2: Uncertainties within the PA

Location Source of Uncertainty

AOI 1 Building L4320

According to SBAH personnel, AFFF leaked from a fire truck

within the fire house and drained through the bay floor drain.

The date of this leak and volume of AFFF released is unknown

AOI 2 Building L4300 The exact timeframe of fire training at this AOI is unknown.

AOI 3 Northeastern

Boundary Release

Locations

The exact frequency of training and number of Tri-MaxTM units

discharged per training event at the Singapore Hangar (L4650)

are unknown.

The frequency of training and volume of AFFF discharged per

training event at the Wash Rack (L4603) are unknown, and it is

unclear whether any discharged AFFF infiltrated cracks in the

ground surface in its vicinity.

The exact timeframe and location of fire training at AASF #2

(L4600) is unknown.

The exact timeframe of the former fire station’s (L4601) use as

a fire station is unknown, and it is unclear whether similar fire

training operations occurred at this fire station that have

occurred at other SBAH fire stations.

The volume of AFFF released during the 2011, 2017, and 2018

releases at the WAATS Hangar (L4605) is unknown. It is also

unclear how exactly released AFFF was disposed of in each

event.

AOI 4 Alpha, Bravo, and

Charlie Row Fuel Spills

The specific locations and dates of these fuel spills are unclear,

and the volume of AFFF used in response to both events is

unknown.

Pinal Airpark

(adjacent source)

It is unknown if AFFF is stored in fire suppression systems at

the airfield. The date and cause of the Boeing 747 fire is

unknown as is the volume of AFFF released in response to the

fire. Additionally, the date, exact location, and volume of AFFF

released in response to the large spill are unknown.

Evergreen Air Center

(adjacent source)

It is unknown whether AFFF is used at Evergreen Air Center, or

if emergency responses using AFFF have occurred at the

location.

I-10 Accident Response

(adjacent source)

SBAH fire department has responded to accidents on I-10 over

the years. It is unknown where the exact locations of accident
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

39

Location Source of Uncertainty

response occurred. The quantity and frequency of AFFF

released are unknown.

7.3 Potential Future Actions

Interviews with SBAH staff whose first-hand knowledge of the facility span 1994 to present

indicate fire training, fire suppression systems, AFFF management, and responses to aviation

emergencies have released PFAS to the environment.

Based on the preliminary CSM developed for SBAH, receptors have been potentially exposed to

PFAS in airborne particulates, surface and subsurface soil, sediment, and groundwater. Table 7-

3 summarizes the rationale used to determine if AOIs at SBAH should be considered for further

investigation using the CERCLA process.

Table 7-3: PA Findings Summary

Area of

Interest AOI Location Rationale Potential Future Action

AOI 1

Building

L4320

32°31’14.6” N;

111°19’59.6” W

Unknown quantity of AFFF

used during fire training

activities equipment storage,

and maintenance activities.

Proceed to an SI, focus on soil

and groundwater

AOI 2

Building

L4300

32°31’17.8” N;

111°19’56.3” W

Unknown quantity of AFFF

used during fire training

activities.

Proceed to an SI, focus on soil

and groundwater

AOI 3

Northeastern

Boundary

Release

Locations

32°31’25.3” N;

111°19’55.3” W

Unknown quantity of AFFF

used during fire training

activities and released from

fire suppression systems.

Proceed to an SI, focus on soil

and groundwater

AOI 4 Alpha,

Bravo, and

Charlie

Rows

32°31’21.5” N;

111°19’54.9” W

Unknown quantity of AFFF

used during emergency

response activities.

Proceed to an SI, focus on soil

and groundwater

ARNG will evaluate the need for an SI at SBAH based on the potential receptors, the potential

migration of PFAS contamination off the facility, and the availability of resources.
AOI 2 Building L4300

AOI 1 Building L4320

AOI 3 Northeastern

Boundary Release Locations

AOI 4 Alpha, Bravo,

and Charlie Rows

Building L4710

0 300 600 1,200

Feet

Legend

Area of Interest

Potential PFAS Release (FTAs,

Non-FTAs, and Emergency

Response Areas)

Facility Boundary

Summary of Findings

Figure 7-1

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PM RG 9/15/2020

1:7,200 ­ 12420 Milestone Center Drive

Germantown, MD 20876

Base Map: Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS,

USDA, USGS, AeroGRID, IGN, and the GIS User Community

40
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

41

8. References

AZARNG, 2010. Arizona Army National Guard Installation Atlas. May.

Arizona Department of Emergency and Military Affairs (ADEMA), 2015. Pre-Construction for the

Silverbell Army Heliport Nitrate Filtration System. June 23, 2015.

Environmental Data Resources Inc. (EDR)TM, 2018. Silver Bell 24641 East Pinal Air Park Road,

Marana, Arizona, 85653 PUR-IQ Report. November 21, 2018.

Federal Emergency Management Agency (FEMA), 2015. Flood Map Service Center, Zip Code

85653. Retrieved June 8, 2015 from https://msc.fema.gov/portal/search?AddressQuery=85653.

Fish, Suzanne K., Paul R. Fish, and John Madsen H. 1985 A Preliminary Analysis of Hohokam

Settlement and Agriculture in the North Tucson Basin. In Proceedings of the 1983 Hohokam

Symposium, Part I, edited by A.E. Dittert and D.E. Dove, pp. 75-100. Occasional Paper 2. Arizona

Archaeological Society, Phoenix.

Goodyear, Albert C. 1975 Hecla II and III: An Interpretative Study of Archaeological Remains from

the Lakeshore Project; Papago Reservation, South-Central Arizona. Anthropological Research

Paper 9. Arizona State University, Tempe.

Hammet and Sicard, 1995. ADWR Open-File Report No. 8, Groundwater Conditions in the Santa

Cruz and Tucson Active Management Areas, Pima, Pinal, and Santa Cruz Counties.

Harris Group Inc., 7 October 2004. A Cultural Resources Inventory of 565.47 Acres near Pinal Air

Park in Marana, Pinal County, Arizona (Revised).

“June 2019 ADEQ Drywell Database.” ADEQ AZURITE Database, 6 June 2019.

Minckley, W.L., and David E. Brown 1982 Wetlands. Desert Plants 4(1-4):223-287.

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

and Practice. January 2018.

National Oceanic and Atmospheric Association (NOAA), 2019. Monthly Station Climate

Summaries, 1981-2010: Station Eloy 4 NE, AZ. https://www.ncdc.noaa.gov/data-access/landbased-station-data/land-based-datasets/climate-normals, accessed March 4, 2019.

Natural Resource Conservation District (NRCD), 1991. Soil Survey of Pinal County Arizona,

Western Part.

National Resource Conservation Service (NRCS), 2015. Web Soil Survey. Retrieved June 9, 2015

from http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx.

Pinal County, Tax Assessor, General Parcel Information, Parcel Viewer. Retrieved May 29, 2015,

from http://pinalcountyaz.gov/departments/informationtechnology/GIS/Pages/Home.aspx#.

(2015 Pinal)

Sellers, William D., and Richard H. Hill 1974 Arizona Climate, 1931-1972. Second, revised edition.

University of Arizona Press, Tucson.

Thornbury, William D. 1965 Regional Geomorphology of the United States. John Wiley & Sons,

New York.
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

42

Turnbull, James., 2005. Pinal Airpark & Silverbell Heliport. Retrieved May 29, 2015 from

http://googlesightseeing.com/2005/05/pinal-silverbell/.

United States, Congress, Olgin, Gilbert. “Pinal County Joint Land Use Study.” Pinal County Joint

Land Use Study, Oct. 2018.

United States, Congress, Pinal County Board of Supervisors. “Pinal County Comprehensive

Plan.” Pinal County Comprehensive Plan, 2015.

www.pinalcountyaz.gov/CommunityDevelopment/Planning/Pages/CompPlan.aspx.

URS, 2008. Draft Cultural Resources Technical Report; Silver Bell Flood Wall. Arizona 

Department of Emergency and Military Affairs, FMA-PJ-09-AZ-2007-001. January 2008.

US Environmental Protection Agency (USEPA), 1991. Guidance for Performing Preliminary

Assessments under CERCLA. EPA/540/G91/013.

US Fish and Wildlife Service (USFWS), 2015. National Wetlands Inventory, Wetlands Mapper.

Retrieved June 9, 2015 from http://www.fws.gov/wetlands/data/mapper.HTML.

US Geological Survey, 1996. Red Rock, AZ. 7.5 minute topographic map. (1996 USGS)

Versar, 2010. Letter to ADEMA; Subject: Revisions to Hydrogeologic Investigation Report for 

Silverbell Wastewater Treatment Plant and Effluent Disposal System.
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

Appendix A

Data Resources
PFAS Preliminary Assessment Report

SBAH, Red Rock, AZ

Data resources will be provided separately on CD. Data resources for Silver Bell Army Heliport

include:

Silver Bell Army Heliport AFFF Release Information

· 2017 SBAH WAATS Hangar April Fire System Release Photos

· 2018 SBAH WAATS Hangar May Fire System Release Summary

· 2018 SBAH WAATS Hangar May Fire System Release Photos

· 2018 SBAH WAATS Hangar July Fire System Release Photos

Silver Bell Army Heliport Construction Planning Documents

· 2008 ADEMA Draft Cultural Resources Technical Report, Silver Bell Flood Wall

· 2009 ADEMA Pre-Construction Site Assessment Vacant 40 Acre Property Within APN

410-14-00309 Marana, Arizona

· 2014 SBAH Utility Site Plan Drawing

· 2015 ADEMA Pre-Construction Assessment for the Silverbell Army Heliport Nitrate

Filtration System

Silver Bell Army Heliport Environmental Investigations and Report Information

· 1994 SBAH Dry Well Registration No. 07-008563-09

· 2006 Phase I Environmental Site Assessment for 170-Acre Marana WWTP Land

Acquisition at SBAH, Marana, Arizona

· 2010 ADEMA Revisions to Hydrogeologic Investigation Report for Silverbell Wastewater

Treatment Plant and Effluent Disposal System

· 2013 Environmental Condition of Property Report for DLA Permitted Assets at SBAH

Silver Bell Army Heliport Environmental Data Resources, Inc.TM Reports

· 2018 Silver Bell Army Heliport EDRTM Reports
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

Appendix B

Preliminary Assessment Documentation
PFAS Preliminary Assessment Report

SBAH, Marana, AZ

Appendix B.1

Interview Records




















PFAS Preliminary Assessment Report

SBAH, Marana, AZ

Appendix B.2

Visual Site Inspection Checklists




PFAS Preliminary Assessment Report

SBAH, Marana, AZ

Appendix B.3

Conceptual Site Model Information



PFAS Preliminary Assessment Report

SBAH, Marana, AZ

Appendix C

Photographic Log
PreliminaryAssessment Report

AECOM

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

Dirt area north of former fire 

station ramp (L4300)

(view to ESE)

Photograph No. 1

Description:

Former fire station ramp 

(L4300)

(view to SE)

Photograph No. 2
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

Former fire station ramp 

(L4300) and low lying area

(view to SW)

Photograph No. 3

Description:

AFFF and Tri-max storage 

area on driveway of current 

fire station (L4320)

(view is NE)

Photograph No. 4
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

Drainage area next to AFFF 

storage area and west of 

current fire station (L4320)

(view to SW)

Photograph No. 5

Description:

Drainage ditch area west of 

current fire station (L4320)

(view to SW)

Photograph No. 6
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

Drywell in drainage ditch 

west of current fire station 

(L4320)

Photograph No. 7

Description:

Tri-max storage area west 

of current fire station 

(L4320)

(view to SW)

Photograph No. 8
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

Floor drain in current fire 

station bay (L4320)

(view to NW)

Photograph No. 9

Description:

Spill pad drain concrete pad 

with cracks

Photograph No. 10
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

April 2017 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to SE)

Photograph No. 11

Description:

April 2017 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to NW)

Photograph No. 12
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

April 2017 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to W)

Photograph No. 13

Description:

April 2017 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to W)

Photograph No. 14
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

May 2018 release of AFFF 

from the “old paint booth”

at the back of the WAATS 

building (L4605)

(view to NW)

Photograph No. 15

Description:

May 2018 release of AFFF 

from the “old paint booth” 

at the back of the WAATS 

building (L4605)

Photograph No. 16
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

May 2018 release of AFFF 

from the “old paint booth” 

at the back of the WAATS 

building (L4605)

Photograph No. 17

Description:

July 2018 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to N)

Photograph No. 18
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description:

July 2018 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to N)

Photograph No. 19

Description:

July 2018 release of AFFF 

from fire riser room at the 

back of the WAATS 

building (L4605)

(view to N)

Photograph No. 20
AECOM

Preliminary Assessment Report 

Silver Bell Army Heliport

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

APPENDIX C – Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS Silver Bell Army Heliport Red Rock, Arizona

Description

Gravel area behind WAATS 

(L4605) where the April 2017, 

May 2018, and July 2018 

releases occurred

(view to N)

Photograph No. 21