FINAL

Preliminary Assessment Report

Stockton AASF, California

Perfluorooctane-Sulfonic Acid (PFOS) and Perfluorooctanoic 

Acid (PFOA) Impacted Sites

ARNG Installations, Nationwide

January 2020

Prepared for:

Army National Guard Headquarters

111 S. George Mason Drive

Arlington, VA 22204

US Army Corps of Engineers, Baltimore District

2 Hopkins Plaza

Baltimore, MD 21201

Prepared by:

AECOM

12420 Milestone Center Drive, Suite 150

Germantown, MD 20876

aecom.com

Contract Number: W912DR-12-D-0014

Delivery Order: W912DR17F0192
PFAS Preliminary Assessment Report

Stockton AASF, California
PFAS Preliminary Assessment Report

Stockton AASF, California

i

Table of Contents

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

1. Introduction ........................................................................................................................7

1.1 Authority and Purpose ..............................................................................................7

1.2 Preliminary Assessment Methods .............................................................................7

1.3 Report Organization ..................................................................................................8

1.4 Facility Location and Description...............................................................................8

1.5 Facility Environmental Setting ...................................................................................9

Soil .................................................................................................................9

Geology .........................................................................................................9

Hydrogeology .................................................................................................9

Hydrology .....................................................................................................10

Climate .........................................................................................................10

Current and Future Land Use .......................................................................10

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

2.1 Wash Rack .............................................................................................................15

2.2 Butler Building Parking Fire Training Area ...............................................................15

3. Non-Fire Training Areas ...................................................................................................19

3.1 AASF Hangar..........................................................................................................19

3.2 Airfield.....................................................................................................................19

4. Emergency Response Areas ............................................................................................21

5. Adjacent Sources .............................................................................................................23

5.1 Montezuma Fire Station #18-2 ................................................................................23

5.2 French Camp Fire Station #11-1 .............................................................................23

5.3 Stockton Metropolitan Airport Runway 29R/11L ......................................................23

5.4 Private Aviation Companies at Stockton Metropolitan Airport ..................................23

5.5 Aramark Uniform and Career Apparel, LLC .............................................................24

6. Preliminary Conceptual Site Model ..................................................................................27

6.1 AOI 1: Airfield ..........................................................................................................27

6.2 AOI 2: Wash Rack ..................................................................................................28

6.3 AOI 3: Butler Building Parking FTA .........................................................................28

7. Conclusions .....................................................................................................................33

7.1 Findings ..................................................................................................................33

7.2 Uncertainties ...........................................................................................................34

7.3 Potential Future Actions ..........................................................................................35

8. References ......................................................................................................................39
PFAS Preliminary Assessment Report

Stockton AASF, California

ii

Tables

Table ES-1 AOIs at Stockton AASF

Table 7-1 AOIs at Stockton AASF

Table 7-2 Uncertainties

Table 7-3 PA Findings Summary

Figures

Figure ES-1 Summary of Findings

Figure ES-2 Preliminary Conceptual Site Model, Stockton AASF

Figure 1-1 Stockton AASF Facility Location

Figure 1-2 Groundwater Features

Figure 1-3 Surface Water Features

Figure 2-1 Fire Training Areas

Figure 3-1 Non-Fire Training Areas

Figure 5-1 Adjacent Sources

Figure 6-1 Areas of Interest

Figure 6-2 Preliminary Conceptual Site Model, AOI 1 & AOI 2 Airfield and Wash Rack

Figure 6-3 Preliminary Conceptual Site Model, AOI 3 Butler Building Parking FTA

Figure 7-1 Summary of Findings

Appendices

Appendix A Data Resources

Appendix B Preliminary Assessment Documentation

B.1 Interview Records

B.2 Visual Site Inspection Checklists

B.3 Conceptual Site Model Information

Appendix C Photographic Log
PFAS Preliminary Assessment Report

Stockton AASF, California

iii

Acronyms and Abbreviations

AASF Army Aviation Support Facility

AECOM AECOM Technical Services, Inc.

AFFF aqueous film forming foam

amsl above mean sea level

AOI area of interest

ARNG Army National Guard

bgs below ground surface

CA California

CAARNG California Army National Guard

CAL FIRE California Department of Forestry and Fire Protection

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CSMS Combined Support Maintenance Shop

CSM conceptual site model

EDR Environmental Data Resources

°F degrees Fahrenheit

FAA Federal Aviation Administration

FEMA Federal Emergency Management Agency

FMS Field Maintenance Shop

ft feet

FTA fire training area

HAZMAT hazardous materials

JP-8 jet propellant #8

NOAA National Oceanic and Atmospheric Administration

OTIE Oneida Total Integrated Enterprises

PA Preliminary Assessment

PFAS per- and poly-fluoroalkyl substances

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

ppt

SI

parts per trillion

Site Inspection

UCMR3 Unregulated Contaminant Monitoring Rule 3

US United States

USACE United States Army Corps of Engineers

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

UST underground storage tank

VSI visual site inspection
PFAS Preliminary Assessment Report

Stockton AASF, California

iv
PFAS Preliminary Assessment Report

Stockton AASF, California

1

Executive Summary

The United States (US) Army Corps of Engineers (USACE) Baltimore District on behalf of the

Army National Guard (ARNG)-Installations & Environment Division, Cleanup Branch contracted

AECOM Technical Services, Inc. (AECOM) to perform Preliminary Assessments (PAs) and Site

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

Impacted Sites at ARNG Facilities Nationwide. The ARNG is assessing the potential exposure to

humans and the effect on the environment related to processes at facilities that used per- and

poly-fluoroalkyl substances (PFAS) (a suite of related chemicals), primarily in the form of aqueous

film forming foam (AFFF) released during firefighting activities or training, although other PFAS

sources are possible.

AECOM completed a PA for PFAS at the Stockton Army Aviation Support Facility (AASF) in

Stockton, California (CA), to assess potential PFAS release areas and exposure pathways to

receptors. The performance of this PA included the following tasks:

· Reviewed available environmental reports and Environmental Data Resources (EDR), Inc.

report packages to obtain information relevant to potential PFAS releases

· Conducted a 1-day site visit on 6 March 2019

· Interviewed current Stockton AASF personnel during the site visit including the CAARNG

Maintenance Officer, Environmental Compliance Officer, and Safety Officer; and, a

Montezuma Fire District representative

· Completed visual site inspections (VSIs) at known or suspected PFAS release locations and

documented with photographs

· Identified areas of interest (AOI) 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

Three AOIs related to potential PFAS releases were identified at Stockton AASF during the PA.

The AOIs are shown on Figure ES-1 and in Table ES-1 below:

Table ES-1: AOIs at Stockton AASF

Area of

Interest

Name Used by Release Dates

AOI 1 Airfield CAARNG Potentially as early as 1992

AOI 2 Wash Rack CAARNG Potentially as early as 1992

AOI 3 Butler Building Parking

Area CAARNG Potentially as early as 1992

Based on information obtained during the PA at these AOIs, there is potential for exposure to

PFAS contamination in media at or near the facility.

Based on the US Environmental Protection Agency (USEPA) Unregulated Contaminant

Monitoring Rule 3 (UCMR3) data, it was indicated that drinking water from the City of Lathrop

public water system drinking water wells were identified to exceed USEPA Health Advisory values

for PFAS. These wells lie within a 5- to 10-mile radius from the Stockton AASF. The preliminary

CSM for Stockton AASF is shown on Figure ES-2.
PFAS Preliminary Assessment Report

Stockton AASF, California

2

This Page Intentionally Blank
­ Figure ES-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Preliminary Assessment for PFAS at Stockton AASF, CA

12/5/2019

12/5/2019

12/5/2019

MS

ST

RG

GIS BY

CHK BY

PM

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

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

12/5/2019

1:12,000

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_ES-1_Stockton_AASF_Summary.mxd

Summary of Findings

12420 Milestone Center Drive

Germantown, MD 20876

Stockton Metropolitan 

Airport Runway 29R/11L

French Camp Fire

Station #11-1

Wash Rack

Butler Building Parking

Fire Training Area Airfield

Aramark Uniform and

Career Apparel, LLC Montezuma Fire

Station Wash Rack

Montezuma Fire

Station #18-2

AASF Hangar French Camp Slough

Rydberg Creek

AOI 2

AOI 3 AOI 1

Legend

Area of Interest

Potential PFAS Release

No Suspected Release

Facility Boundary

Water Body

River/Stream

Canal/Ditch

0 500 1,000 2,000

Feet

3
PFAS Preliminary Assessment Report

Stockton AASF, California

4

This Page Intentionally Blank
Media

SOURCE PATHWAY RECEPTOR

AOI 1

AOI 2

AOI 3

Fire Training and 

Mobile Fire 

Extinguishers 

Discharge

PFAS in 

surface soil

PFAS in 

subsurface 

soil

Human 

activities

Precipitation/ 

run-off

Leaching/ 

infiltration

Airborne soil 

particulate

Surface soil 

at AOI

Surface 

water/ 

sediment

Subsurface 

soil

Shallow 

groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Flow-chart continues

Partial/ possible flow

Flow-chart stops

Incomplete pathway

Possible complete pathway

Complete pathway

/ / / /

Site 

Worker

Construction 

Worker Resident Trespasser/ Recreational User

Site 

Worker

Construction 

Worker Resident

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure ES-2

Preliminary Conceptual Site Model

Stockton AASF

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ 

Recreational User

1. The resident receptor refers to an off-site

resident.

2. Current risk practice suggests the exposure

pathway for dermal contact is insignificant

compared to ingestion, but supporting data is

sparse and continues to be studied.

Notes:

5
PFAS Preliminary Assessment Report

Stockton AASF, California

6
PFAS Preliminary Assessment Report

Stockton AASF, California

7

1. Introduction

1.1 Authority and Purpose

The United States (US) Army Corps of Engineers (USACE) Baltimore District on behalf of the

Army National Guard (ARNG)-Installations & Environment Division, Cleanup Branch contracted

AECOM Technical Services, Inc. (AECOM) to perform Preliminary Assessments (PAs) and Site

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

Impacted Sites at ARNG Facilities Nationwide 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) (a suite of related chemicals), primarily releases of aqueous film forming foam (AFFF)

although other sources of PFAS are possible. In addition, the ARNG is assessing businesses or

operations adjacent to the ARNG facility (not under the control of ARNG) that could potentially be

responsible for a PFAS release.

PFAS are classified as emerging environmental contaminants that are garnering increasing

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

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

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

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

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

national standards regulating PFAS in drinking water. In the absence of federal maximum

contaminant levels, some states have adopted their own drinking water standards for PFAS. On

13 July 2018, under the authority of the Deputy Director of the Division of Drinking Water,

California issued drinking water notification levels of 14 parts per trillion (ppt) for PFOA and 13

ppt for PFOS. Notification levels are non-regulatory health-based advisory levels established for

contaminants in drinking water for which maximum contaminant levels have not been established.

This report presents findings of a PA for PFAS at California Army National Guard (CAARNG)

Stockton Army Aviation Support Facility (AASF) in Stockton, CA, 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 Part 300), and USACE requirements and guidance.

This PA documents the known fire training areas (FTAs) as well as additional locations where

PFAS may have been released to the environment at Stockton AASF. The term PFAS will be used

throughout this report to encompass all PFAS chemicals being evaluated, including PFOS and

PFOA, which are key components AFFF.

1.2 Preliminary Assessment Methods

The performance of this PA included the following tasks:

· Reviewed available administrative record documents and Environmental Data Resources

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

· Conducted a 1-day site visit on 6 March 2019

· Interviewed current Stockton AASF personnel during the site visit including the CAARNG

Maintenance Officer, Environmental Compliance Officer, and Safety Officer; and, a

Montezuma Fire District representative

· Completed visual site inspections (VSIs) at known or suspected PFAS release locations and

documented with photographs
PFAS Preliminary Assessment Report

Stockton AASF, California

8

· Identified areas 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 (USEPA, 1991). The report sections and descriptions

of each are:

· 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 FTAs at the facility identified during the site

visit.

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

at the facility identified during the site visit.

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

facility, specifically in response to emergency situations.

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

facility that are not under the control of ARNG.

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

and receptors at each AOI.

· 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

Stockton AASF is located at 2000 Stimson Road, Stockton, CA 95206 and borders the Stockton

Metropolitan Airport to the south. The Stockton Metropolitan Airport has a history of military use

as a training installation, and has been formerly referred to as Stockton Field and Sharpe Army

Depot Field Annex. In 1973 the US Army vacated the airport; however, the CAARNG presence 

remains. The AASF is situated in the Sacramento-San Joaquin Valley within the Central Valley,

approximately equidistant from the Pacific Ocean and Sierra Nevada Mountains (Figure 1-1). The

latitude, longitude, and surface elevation at the main gate of the AASF are 37°53’13.0” N;

121°14’37.2” W, and 21 feet (ft) above mean sea level (amsl), respectively.

Stockton AASF is a CAARNG aviation maintenance facility for helicopters. Impervious surfaces

make up 82% of the 22-acre facility and include roadways, parking lots, helipads, and taxi lanes.

Physical structures include a hangar, maintenance shop, fuel tank farm, wash rack, and

equipment storage areas. Stockton AASF has been leased from the San Joaquin County since

1972 (White, T., 2019).

Four state-owned divisional areas comprise the entire CAARNG facility, including the AASF, Field

Maintenance Shop (FMS) #24, Armory, and Combined Support Maintenance Shop (CSMS).

However, only the AASF was specifically evaluated in this PA report. FMS #24 is a one-story

maintenance building and the site of two former underground storage tanks (USTs). FMS #24 lies
PFAS Preliminary Assessment Report

Stockton AASF, California

9

adjacent to the southwest of the AASF and has been extensively investigated as a source of 

petroleum hydrocarbons and related compounds in soil and groundwater (Adanta-ECM Joint 

Venture, 2018). 

1.5 Facility Environmental Setting

The areas surrounding Stockton AASF comprise light and heavy industrial areas directly 

north/northwest and farmlands to the east, south, and west. Few residents reside in the rural 

farmlands within a one mile radius of the AASF, although the community of French Camp, CA is 

located approximately 1.5 miles to the west. The site sits at an elevation of 26 ft amsl with a slight 

general topographic gradient to the west. There are no significant natural topographic features 

surrounding the facility. 

Soil

As indicated in the 2019 EDR report (Appendix A), two major soil components were found at the 

Stockton AASF property. The Jacktone and Stockton soil units are both somewhat poorly drained, 

partially hydric clays. The deposits underlying the site are characterized by interbedded silty clays, 

clayey silts, sands, and silty to clayey sands (Oneida Total Integrated Enterprises [OTIE], 2010; 

2013). Boring logs from previous subsurface investigations at FMS #24 encountered fine silts and 

clays to depths of approximately 20 to 30 ft below ground surface (bgs) overlying coarser, 

relatively continuous sands and silts (OTIE, 2010). 

Geology

Stockton AASF lies in the border of the Sacramento Valley and San Joaquin Valley. Deposits 

found within this region are composed of unconsolidated Quaternary sediments made up of 

alluvial and lake deposits. The Sierra Nevada Mountains to the east and the Sacramento Valley 

Coast Ranges to the west are both contributing sources of deposits that originate from a variety 

of metamorphic and sedimentary rocks (Adanta-ECM Joint Venture, 2018). The uppermost 

geologic unit comprises marine and nonmarine (continental) sedimentary rocks (Figure 1-2). The 

Stockton Fault (trending northeast-southwest) is located within Stockton city limits; the Midland 

Fault Zone (trending north) is located approximately 25 miles northwest of Stockton AASF (OTIE, 

2010). The Stockton fault forms the divide between the Sacramento and the San Joaquin Valleys. 

Hydrogeology

Stockton AASF is located within the San Joaquin Groundwater Basin, which contains several 

water-bearing zones within the upper 700 to 800 ft of unconsolidated fill. Shallow groundwater 

primarily occurs in unconfined conditions, although it may occur in semi-confined condition due 

to the distribution of clay lenses in the sediments. Based on historical investigations performed in 

the vicinity of the AASF, coarser sediments are generally discontinuous in the lateral and vertical 

direction above the groundwater table and more laterally continuous below the groundwater table 

(Versar, Inc., 2004; URS Corporation, 2007; OTIE, 2010, 2012, 2013; Environmental Cost 

Management, Inc., 2015). 

According to the California Water Board Groundwater Ambient Monitoring and Assessment 

Program database, multiple public water system wells are located within a 4-mile radius. A public 

water system well is defined as serving “15 or more connections or more than 25 people per day” 

(California Water Board, 2019). Drinking water wells from the City of Lathrop public water system 

were identified in the Unregulated Contaminant Monitoring Rule 3 (UCMR3) data to exceed 

USEPA Health Advisory values for PFAS. These wells lie within a 5- to 10-mile radius from the 

Stockton AASF, and the UCMR3 data is included in Appendix A. Stockton AASF receives potable 

water from the Stockton Municipal Utilities Water Service, which derives approximately 25% of its 

water supply from groundwater wells, while the remaining water supply is from treated surface 
PFAS Preliminary Assessment Report

Stockton AASF, California

10

water supplied by the Stockton East Water District. The locations of Stockton Municipal Utilities 

Water Service wells are unknown. The Stockton East Water District also supplies surface water 

for agricultural irrigation in the area. The Stockton East Water District sources surface water from 

the New Melones Reservoir and the New Hogan Reservoir, located approximately 30 and 38 

miles northeast of the AASF, respectively (City of Stockton, 2019; Stockton East Water District, 

2019). 

No groundwater monitoring data are available for the AASF; however, the CAARNG has been 

monitoring groundwater at the adjoining FMS #24 site since 2010. Depth to groundwater has been 

generally encountered from 30 to 35 ft bgs, and the hydraulic gradient was measured at 

approximately 0.0015 ft/ft in 2013 (Adanta-ECM Joint Venture, 2018). Groundwater flow has been 

consistently measured from nine monitoring wells and two remediation wells in the north/northeast 

direction (ECM Consultants, 2018). In the vicinity of the site, groundwater flow in regional 

unconfined conditions is generally southwesterly toward the valley (Adanta-ECM Joint Venture, 

2018). Groundwater features are presented on Figure 1-2. 

Hydrology

The nearest surface water feature is Rydberg Creek, which wraps around the southern and 

western boundary of the Stockton AASF facility, flows northwest, and connects with French Camp 

Slough. According to the National Wetlands Inventory in the EDR report (Appendix A), there are 

no wetland areas within the AASF property. The western portion of the AASF is in the Federal 

Emergency Management Agency (FEMA) 100-year flood zone. 

Stockton AASF lies within the Walker Slough-French Camp Slough Watershed. Storm water is 

diverted to storm drains inlets that are located on and around the AASF. The storm drains then 

discharge offsite through two discharge points into the city of the Stockton storm sewer system, 

which eventually leads to the San Joaquin River. The western discharge point, however, has not 

been observed to have any flow. Surface water that is not captured in storm drains is drained 

south into an adjoining ditch canal (Rydberg Creek), which is a tributary to the San Joaquin River. 

The closest surface water intake is along the San Joaquin River, approximately 18 miles to the 

northwest. Based on UCMR3 data, there were no detections of PFAS in surface water intakes for 

the cities of Stockton and Lathrop. The AASF has no water treatment system, and the oil water 

separator associated with the wash rack is connected to the Stockton sanitary sewer system 

(HazCon, 2017). Surface water features are presented on Figure 1-3. 

Climate

Stockton AASF is in a semi-arid, Mediterranean climate zone characterized by warm, dry 

summers and mild winters. The average annual rainfall is approximately 13.95 inches, with the 

majority of the rainfall occurring between late fall and early spring. Summer temperatures peak in 

July, with an average high of 94 degrees Fahrenheit (°F) and an average low of 61 °F. Winter 

temperatures are lowest in December to January and range from 53 °F during the day to 37 °F at 

night. Prevailing wind speeds are westerly or northwesterly for nine months out of the year and 

southeasterly for three months out of the year (National Oceanic and Atmospheric Administration 

[NOAA], n.d.). 

Current and Future Land Use

The Stockton AASF serves as a CAARNG aviation maintenance facility for helicopters. The AASF 

includes a maintenance hangar, various storage buildings, and related infrastructure including 

parking lots, aircraft parking areas, wash rack, and refueling pads. The AASF is categorized as a 

small-quantity hazardous waste generator because it manages a variety of hazardous materials. 

Operating hours are from 0700 hours to 1630 hours Monday through Friday, and the AASF is 
PFAS Preliminary Assessment Report

Stockton AASF, California

11

staffed by approximately 95 CAARNG personnel (HazCon, 2017). Reasonably anticipated future

land use is not expected to change from the current land use described above.
CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

ST

5/15/2019

5/15/2019

NOTES Preliminary Assessment for PFAS at Stockton AASF, CA

1:63,360

5/15/2019 ­ Figure 1-1 PM RG 5/15/2019

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_1-1_Stockton_AASF_Facility_Location.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Facility Location

Base Map: Sources: Esri, HERE, DeLorme, USGS,

Intermap, increment P Corp., NRCAN, Esri Japan, METI,

0 0.5 1 2

Miles

^_

Legend

Facility Boundary

Stockton AASF

12
!C(

!

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(

!C(!C( !C(

!C(!C(

!C(

!C(

!C(

!C(

!C(

!C( !C(

!C(

Lone Tree Creek

Fr e nch CampSlough

Littlejohns Creek

Rydberg Creek

Legend

Facility Boundary

Water Body

Wetland

River/Stream

Canal/Ditch

Inferred Groundwater Flow

Direction

Geology

Marine and nonmarine

(continental) sedimentary

rocks

Wells

!C( Municipal Well

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

ST

5/15/2019

5/15/2019

NOTES Preliminary Assessment for PFAS at Stockton AASF, CA

1:31,680

5/15/2019 ­ Figure 1-2 PM RG 5/15/2019

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_1-2_Stockton_AASF_Groundwater.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Groundwater Features

Base Map: Source: Esri, DigitalGlobe, GeoEye,

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

0 0.25 0.5 1

Miles

13
Town of French

Camp-San Joaquin

River Watershed

Simmons

Creek-Littlejohns

Creek Watershed

Walker Slough-French

Camp Slough Watershed

Lower Lone

Tree Creek

Watershed

Lone Tree Creek

Fr e nch CampSlough

Littlejohns Creek

Rydberg Creek

Legend

Facility Boundary

Water Body

Wetland

River/Stream

Canal/Ditch

Surface Water

Flow Direction

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

ST

5/15/2019

5/15/2019

NOTES Preliminary Assessment for PFAS at Stockton AASF, CA

1:31,680

5/15/2019 ­ Figure 1-3 PM RG 5/15/2019

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_1-3_Stockton_AASF_Surface_Water.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Surface Water Features

Base Map: Source: Esri, DigitalGlobe, GeoEye,

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

0 0.25 0.5 1

Miles

14
PFAS Preliminary Assessment Report

Stockton AASF, California

15

2. Fire Training Areas

Two former FTAs were identified through record reviews and site visit interviews during the PA. A

description and the location of the FTAs are shown on Figure 2-1. PA interview and VSI

documents and photographs are included in Appendix B and Appendix C, respectively.

Interviewees had direct knowledge of fire training activities covering the span of 27 years (1992

to present day).

2.1 Wash Rack

Familiarization training with the Tri-MaxTM fire extinguishers occurred at the wash rack.

Occasionally, these exercises would also involve extinguishing live fire from fuel that was poured

and ignited in a tray pan. The contents of approximately one Tri-MaxTM fire extinguisher would be

emptied during each training event and then left in place to evaporate or disperse in the wind. The

drains in the wash rack area lead to an oil water separator, which then flows into the Stockton

sanitary sewer system. The wash rack is located at geographic coordinates 37°53’07.6”N;

121°14’36.9”W.

A hazardous materials (HAZMAT) locker is located on the southwest corner of the wash rack.

During the PA site visit, eighteen 5-gallon 6% AFFF canisters of the brand FireAde Mil-Spec were

observed in the HAZMAT locker. Refilling of the Tri-MaxTM extinguishers also occurred in the wash

rack area, but only minimal spills, if any, would have occurred during this operation. According to

an interview with a Maintenance Officer, AASF personnel also used to wash out aircraft tanks at

the wash rack with an unknown type and quantity of foam or soap. However, personnel stopped

using the foam or soap approximately five to six years ago at the request of the California

Department of Forestry and Fire Protection (CAL FIRE) due to environmental reasons. One TriMaxTM fire extinguisher was also observed stationed nearby the HAZMAT locker.

The AASF personnel interviewed could not recall specific dates of training exercises, but they

could recall the occurrence of training exercises during their entire tenure at the facility, with the

longest tenure extending back to 1992. The training exercises occurred at an annual frequency

until approximately 2010. After 2010, the exercises occurred less frequently because the TriMaxTM fire extinguishers used in the exercises began breaking down. According to an interview

with the Safety Officer, the Tri-MaxTM fire extinguishers tended to break down every five years,

since proper safety inspection was not often performed on them. However, no leak from the TriMaxTM fire extinguishers was ever reported.

There was some uncertainty regarding the contents of the Tri-MaxTM fire extinguishers used

during training activities. The Environmental Compliance Officer, whose knowledge extends back

to 1992, stated that 3% AFFF was used until recently, when the AASF acquired 6% AFFF of the

brand FireAde Mil-Spec. The Safety Officer, whose knowledge extends back to 2004, stated that

sometimes the Tri-MaxTM fire extinguishers would be filled with soap and water rather than AFFF.

Another Maintenance Officer with knowledge extending back to the 2000s claimed that training

was conducted with water, not foam, because the Tri-MaxTM fire extinguishers were hard to refill.

2.2 Butler Building Parking Fire Training Area

The parking area west of the Aviation Maintenance Storage Facility, referred to as the “Butler

Building” by AASF staff, is a paved lot that runs northwest to southeast. The site was used for fire

training activities that involved extinguishing live fire from jet propellant #8 (JP-8) fuel that was

poured and then ignited in tray pans. The training exercises were facilitated by the Montezuma

Fire District, but the AASF provided the Tri-MaxTM fire extinguishers that were used to extinguish

the fire. The contents of approximately one Tri-MaxTM fire extinguisher would be emptied during
PFAS Preliminary Assessment Report

Stockton AASF, California

16

each training event and then left in place to evaporate or disperse in the wind. The parking area

is located at geographic coordinates 37°53’10.8”N; 121°14’39.2”W.

The AASF personnel interviewed could not recall specific dates of fire training exercises, but they

could recall the occurrence of fire training exercises during their entire tenure at the facility, with

the longest tenure extending back to 1992. The fire training exercises occurred at an annual

frequency until approximately 2010 to 2012, when the Butler Building was in construction. During

construction, the soil beneath and in the vicinity of the parking lot was disturbed, and the area

was regraded. The original soil was either left in place or used to fill in a depression that was west

of the road next to the Butler Building. After construction, the area was more prone to flooding, so

fire training activities in the parking lot ceased.

There was some uncertainty regarding the contents of the Tri-MaxTM fire extinguishers used

during fire training activities. The Environmental Compliance Officer, whose knowledge extends

back to 1992, stated that 3% AFFF was used until recently when the AASF acquired 6% AFFF of

the brand FireAde Mil-Spec. The Safety Officer, whose knowledge extends back to 2004, stated

that sometimes the Tri-MaxTM fire extinguishers would be filled with soap and water rather than

AFFF. Another Maintenance Officer with knowledge extending back to the 2000s claimed that

training was conducted with water, not foam, because the Tri-MaxTM fire extinguishers were hard

to refill.

During the PA site visit, potentially distressed vegetation was observed in the grassy area adjacent

to the paved parking lot. Some minor flooding was also observed leading into the area from the

south. The paved parking lot is in a restricted, fenced area with an access gate located on the

northwest side.
Rydberg Creek

Wash Rack

Butler Building Parking Fire Training Area

Legend

Potential PFAS Release

Facility Boundary

Canal/Ditch

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

ST

5/15/2019

5/15/2019

NOTES Preliminary Assessment for PFAS at Stockton AASF, CA

1:7,200

5/15/2019 ­ Figure 2-1 PM RG 5/15/2019

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_2-1_Stockton_AASF_Fire_Training_Areas.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Fire Training Areas

Base Map: Source: Esri, DigitalGlobe, GeoEye,

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

0 300 600 1,200

Feet

17
PFAS Preliminary Assessment Report

Stockton AASF, California

18
PFAS Preliminary Assessment Report

Stockton AASF, California

19

3. Non-Fire Training Areas

Two non-FTAs where AFFF was stored and/or potentially released were identified during the PA.

Descriptions of the non-FTAs are presented below and shown in Figure 3-1.

3.1 AASF Hangar

The AASF Hangar is a maintenance hangar for helicopters and houses various related

maintenance shops, offices, and supply rooms. The AASF Hangar is located at geographic

coordinates 37°53’10.0”N; 121°14’35.6”W.

The hangar was toured during the VSI and was not found to have any storage of AFFF or contain

a fire suppression system. The building is equipped with dry chemical (non-AFFF) fire

extinguishers. According to interviews with AASF personnel, whose knowledge covers the period

of 1992 to present day, AFFF has not been stored or used historically at the hangar.

3.2 Airfield

Training sessions where personnel would familiarize themselves with discharging the Tri-MaxTM

fire extinguishers, also referred to as “familiarization training”, were conducted in the airfield.

Personnel would stand at the flightline boundary and discharge the Tri-MaxTM fire extinguishers

in the northeast direction towards the center of the airfield as a measurement to see how far the

discharge could go. The contents of approximately one Tri-MaxTM fire extinguisher would be

emptied during each training event and then left in place to evaporate or disperse in the wind. The

approximate geographic coordinates of this training area are 37°53’10.6”N; 121°14’29.9”W.

The AASF personnel interviewed could not recall specific dates of the familiarization training, but

they could recall the occurrence of the familiarization training during their entire tenure at the

facility with the longest tenure extending back to 1992. The familiarization training occurred at an

annual frequency until approximately 2010. After 2010, the exercises occurred less frequently

because the Tri-MaxTM fire extinguishers used in the exercises began breaking down. According

to an interview with the Safety Officer, the Tri-MaxTM fire extinguishers tended to break down every

five years, since proper safety inspection was not often performed on them. However, no leak

from the Tri-MaxTM fire extinguishers was ever reported.

There was some uncertainty regarding the contents of the Tri-MaxTM fire extinguishers used

during familiarization training. The Environmental Compliance Officer, whose knowledge extends

back to 1992, stated that 3% AFFF was used until recently when the AASF acquired 6% AFFF of

the brand FireAde Mil-Spec. The Safety Officer, whose knowledge extends back to 2004, stated

that sometimes the Tri-MaxTM fire extinguishers would be filled with soap and water rather than

AFFF. Another Maintenance Officer with knowledge extending back to the 2000s claimed that

training was conducted with water, not foam, because the Tri-MaxTM fire extinguishers were hard

to refill.

Approximately 13 Tri-MaxTM fire extinguishers were observed on or in the vicinity of the airfield

during the VSI. Most of the Tri-MaxTM extinguishers were stationed next to helipads on the airfield.

At least two Tri-MaxTM extinguishers were observed in the northern adjacent helicopter parking

area. The Tri-MaxTM extinguishers remain equipped with presumably either 3% or 6% AFFF,

based on previous and current facility supplies.
Rydberg Creek

AASF Hangar

Airfield

Legend

Potential PFAS Release

No Suspected Release

Facility Boundary

Canal/Ditch

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

ST

5/15/2019

5/15/2019

NOTES Preliminary Assessment for PFAS at Stockton AASF, CA

1:7,200

5/15/2019 ­ Figure 3-1 PM RG 5/15/2019

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_3-1_Stockton_AASF_Non-Fire_Training_Areas.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Non-Fire Training Areas

Base Map: Source: Esri, DigitalGlobe, GeoEye,

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

0 300 600 1,200

Feet

20
PFAS Preliminary Assessment Report

Stockton AASF, California

21

4. Emergency Response Areas

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

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

identified within the current Stockton AASF facility during the PA through interviews with AASF

personnel, whose knowledge covers the period of 1992 to present day, or EDR Reports. Aircraft

and other emergency services are provided by the Montezuma Fire District.
PFAS Preliminary Assessment Report

Stockton AASF, California

22
PFAS Preliminary Assessment Report

Stockton AASF, California

23

5. Adjacent Sources

Numerous potential off-facility sources of PFAS adjacent to the Stockton AASF, not under the

control of the CAARNG, were identified during the PA. A description of each adjacent source is

presented below, and the adjacent sources are shown on Figure 5-1.

5.1 Montezuma Fire Station #18-2

The Montezuma Fire District owns and operates Fire Station #18-2 at 7422 South Lindbergh

Street within the Stockton Metropolitan Airport. The fire station stores and uses 3% AFFF in fire

training activities conducted at a fuel tank containment system behind the fire station and a wash

rack located at geographic coordinates 37°53’25.1”N; 121°14’21.1”W. The Montezuma Fire

Station #18-2 has specialized aircraft crash rescue vehicles that respond to aircraft emergencies

within the Stockton Metropolitan Airport property, including the Stockton AASF, and has been

identified by AASF personnel to have facilitated fire training activities at Stockton AASF.

According to an interview with a Montezuma Fire District Captain, training at the wash rack has

occurred a couple times during the estimated years of 1990s-2000. Training still occurs annually

at the fuel tank containment system. Training exercises typically involve nozzle spray testing using

3% AFFF for a duration of approximately 5 minutes.

5.2 French Camp Fire Station #11-1

The French Camp McKinley Fire District owns and operates out of Fire Station #11-1 at 310 East

French Camp Road, French Camp, CA 95231. It is unknown whether the fire training activities

utilizing AFFF have occurred at the location. Fire Station #11-1 is inferred to be in the

downgradient surface water and cross-gradient groundwater flow path from the AASF. Potential

AFFF releases from Fire Station #11-1 are unlikely to affect the AASF.

5.3 Stockton Metropolitan Airport Runway 29R/11L

The Stockton Metropolitan Airport is a county-owned and operated joint-civil military airport

located northeast of the AASF. The airport has been historically used for various military purposes

under the name Stockton Field and Sharpe Army Depot Field Annex. The US Army vacated the

airport in 1973; however, the CAARNG presence remains. Today, the airport performs domestic

commercial service operations, cargo operations, and a variety of general aviation operations. As

a civil airport, it operates under the purview of Federal Aviation Administration (FAA) guidance. It

is unknown whether AFFF training events are performed at the airport under FAA guidance, or

whether training events have been performed historically.

According to a National Transportation Safety Board accident report, an accident occurred on the

Stockton Metropolitan Airport Runway 29R/11L in 1969 that resulted in the use of “foam” near the

west end of the runway (National Transportation Safety Board, 1969). The type of foam is not

specified in the report. Because an unspecified foam was used in response to a crash on the

runway, and airport runways and their surrounding spaces are a common place for required fire

training events, the runway is considered an adjacent potential PFAS release area.

5.4 Private Aviation Companies at Stockton Metropolitan Airport

A number of private aviation companies are present at the Stockton Metropolitan Airport. At none

of the companies could the use or storage of AFFF be determined during the PA. These

companies are listed below.

· Atlantic Aviation maintains a hangar at 6364 Lindbergh St, Stockton, CA 95206.
PFAS Preliminary Assessment Report

Stockton AASF, California

24

· An Amazon Fulfillment Center is located at 4723 South B Street, Stockton, CA 95206.

Stockton AASF personnel also indicated during the PA interviews that the facility is also the

former location of an Atlas Air hangar. The Amazon Fulfillment Center provides air cargo

services for Amazon customers in the US.

· The A. G. Spanos Jet Center is located at 4800 S Airport Way, Stockton, CA 95206. The A.

G. Spanos Jet Center is a hangar containing a private fleet of jets.

· Big Valley Aviation, Inc. maintains a hangar at 7535 Lindbergh Street, Stockton, CA 95206.

The company provides maintenance and overhaul services for regional helicopters and

fixed wing aircrafts.

· Vintage Aircraft is a maintenance hangar and shop for vintage aircraft. The facility is located

at 7432 C.E. Dixon Street, Stockton, CA 95206.

5.5 Aramark Uniform and Career Apparel, LLC

An Aramark Uniform and Career Apparel, LLC facility is located at 7679 Longe Street, Stockton,

CA 95206. The facility provides uniform-related services such as uniform cleaning and fire

resistant workwear. PFAS contamination from these industrial applications is unknown but

possible.
­ Figure 5-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Preliminary Assessment for PFAS at Stockton AASF, CA

12/5/2019

12/5/2019

12/5/2019

MS

ST

RG

GIS BY

CHK BY

PM

Base Map: Sources: Esri, HERE, Garmin, USGS, Intermap, INCREMENT P, NRCan,

Esri Japan, METI, Esri China (Hong Kong), Esri Korea, Esri (Thailand), NGCC, (c)

12/5/2019

1:15,600

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_5-1_Stockton_AASF_Adjacent_Sources.mxd

Adjacent Sources

12420 Milestone Center Drive

Germantown, MD 20876

Aramark Uniform

and Career

Apparel, LLC

Montezuma

Fire Station

Wash Rack

Montezuma Fire

Station #18-2

Stockton Metropolitan

Airport Runway 29R/11L

French Camp Slough

French Camp Slough

Rydberg Creek

Big Valley Aviation, Inc.

Vintage Aircraft

Atlantic Aviation

Amazon Fulfillment Center

Legend

Potential PFAS Release

Facility Boundary

River/Stream

Canal/Ditch

0 650 1,300 2,600

Feet

French Camp Fire

Station #11-1

0 100 200 400

Feet

25
PFAS Preliminary Assessment Report

Stockton AASF, California

26
PFAS Preliminary Assessment Report

Stockton AASF, California

27

6. Preliminary Conceptual Site Model

Based on the PA findings, there were two FTAs and one non-FTA where AFFF may have been

incidentally spilled or discharged to the ground surface. As such, these AOIs may be potential

PFAS source areas. The AOIs and preliminary CSMs for the AOIs are shown on Figure 6-1 to

Figure 6-3 and summarized below.

The following AOIs were identified as a potential PFAS source area:

· AOI 1 – Airfield

· AOI 2 – Wash Rack

· AOI 3 – Butler Building Parking Area

The following sections describe the CSM components and the specific CSM developed for the

AOI. The CSM identifies the three components necessary for a potentially complete exposure

pathway: (1) source, (2) pathway, (3) receptor. If any of these elements are missing, the pathway

is considered incomplete.

In general, the potential PFAS exposure pathways are ingestion and inhalation. Dermal contact

is not considered to be a potential exposure pathway, as studies have shown very limited

absorption of PFAS through the skin (National Ground Water Association, 2018). Receptors for

Stockton AASF include site workers, construction workers, recreational users, and trespassers.

Groundwater is too deep in the region for direct exposure to construction workers during grounddisturbing activities; however, public water system wells located within a 4-mile radius of the

facility present a potential exposure pathway for groundwater to site workers and off-facility

residents. The preliminary CSMs for each AOI indicate which specific receptors could potentially

be exposed to PFAS.

6.1 AOI 1: Airfield

AOI 1 is the airfield where controlled AFFF releases through familiarization training have occurred

annually potentially as early as 1992 and then less frequently after 2010.

AOI 1 lies within the San Joaquin Valley Groundwater Basin, and all surface water is eventually

drained by tributaries to the San Joaquin River. PFAS are water soluble and can migrate readily

from soil to groundwater or surface water via leaching and run-off. If PFAS releases to surface

and subsurface soil occurred, it is possible that PFAS migrated from surface soil at AOI 1 to

groundwater and waters in the San Joaquin River. In addition, precipitation infiltrating into the

grassy surrounding areas of the AOI may cause the migration of PFAS from surface and

subsurface soil to groundwater and surface water.

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

potential PFAS contamination via inhalation of dust or ingestion of surface and subsurface soil.

Inhalation of dust or ingestion of surface soil may also occur during the routine activities of site

workers. Therefore, the inhalation and ingestion pathways for these receptors are considered

potentially complete. Site workers, construction workers, and trespassers at the facility may be

exposed to PFAS via ingestion of surface water and sediment in the San Joaquin River and its

tributaries. Similarly, recreational users may be exposed to PFAS in surface water and sediment

off-facility.

Due to the presence of public water system wells within a 4-mile radius of the facility, the pathway

for PFAS exposure to off-facility residents via ingestion of groundwater is considered potentially

complete. Because the location of Stockton Municipal Utilities Water Service groundwater wells

that may serve the AASF are unknown, the pathway for PFAS exposure to site workers via
PFAS Preliminary Assessment Report

Stockton AASF, California

28

ingestion of groundwater is also considered potentially complete. The preliminary CSM for AOI 1

is shown on Figure 6-2.

6.2 AOI 2: Wash Rack

AOI 2 is the wash rack area and includes the HAZMAT locker with AFFF storage, located at the

southwest corner of the wash rack. Controlled AFFF releases to the wash rack through activities

related to fire training and familiarization training have occurred annually, potentially as early as

1992, and then less frequently after 2010. Potential AFFF releases from incidental spills in the

wash rack area may have also occurred.

The wash rack drains lead to an oil water separator that connects to the Stockton sanitary sewer

system. Therefore, discharges of AFFF in the wash rack would release directly into the sanitary

sewer system. However, the HAZMAT locker is located near unpaved, grassy areas. Potential

PFAS releases nearby the HAZMAT locker drains via overland surface flow to the adjacent ditch

canal (Rydberg Creek), which is a tributary to the San Joaquin River. The pathways and receptors

for AOI 2 are the same as described in Section 6.1. The preliminary CSM for AOI 2 is shown on

Figure 6-2.

6.3 AOI 3: Butler Building Parking FTA

AOI 3 is a former FTA at what is now the parking area located east of the Butler Building.

Controlled AFFF releases through fire training activities have occurred annually, potentially as

early as 1992, until approximately 2010 to 2012, when the Butler Building was constructed.

Ground-disturbing activities at AOI 3 have occurred and may have resulted in construction worker

exposure to potential PFAS contamination via inhalation of dust from surface soil or ingestion of

surface and subsurface soil. During the construction of the Butler Building, the soil beneath and

in the vicinity of the parking lot was disturbed, and the area was regraded. The original soil was

either left in place or used to fill in a depression west of the road next to the Butler Building.

Therefore, potentially impacted soil remains at AOI 3. The pathways and receptors for AOI 3 are

the same as described in Section 6.1. The preliminary CSM for AOI 3 is shown on Figure 6-3.
­ Figure 6-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Preliminary Assessment for PFAS at Stockton AASF, CA

12/5/2019

12/5/2019

12/5/2019

MS

ST

RG

GIS BY

CHK BY

PM

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

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

12/5/2019

1:12,000

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_6-1_Stockton_AASF_AOIs.mxd

Area of Interest

12420 Milestone Center Drive

Germantown, MD 20876

!C(

!C(

!C(

!C(

!C( !C(

!C(

!C(!C(

!C(

!C(

!C(

!C(!C( !C(

!C(!C(

!C(

!C(

!C(

!C( !C(

!C(

French Camp Fire

Station #11-1

Wash Rack

Butler Building Parking 

Fire Training Area Airfield

Aramark Uniform and

Career Apparel, LLC Montezuma Fire

Station Wash Rack

Montezuma Fire

Station #18-2

AASF Hangar

Montezuma Fire

Station Wash Rack

French Camp Slough

Rydberg Creek

Town of French

Camp-San Joaquin

River Watershed

Walker Slough-French

Camp Slough Watershed

Big Valley Aviation, Inc.

Vintage Aircraft

Atlantic Aviation

A. G. Spanos Jet Center

Amazon Fulfillment Center

AOI 2

AOI 1

AOI 3

Legend

Area of Interest

Potential PFAS Release

No Suspected Release

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Surface Water Flow Direction

Inferred Groundwater Flow Direction

!C( Municipal Well

0 500 1,000 2,000

Feet

29
PFAS Preliminary Assessment Report

Stockton AASF, California

30

This Page Intentionally Blank
Media

SOURCE PATHWAY RECEPTOR

AOI 1

AOI 2

Fire Training and 

Mobile Fire 

Extinguishers 

Discharge

PFAS in 

surface soil

Human 

activities

Precipitation/ 

run-off

Leaching/ 

infiltration

Airborne soil 

particulate

Surface soil 

at AOI

Surface 

water/ 

sediment

Subsurface 

soil

Shallow 

groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Flow-chart continues

Partial/ possible flow

Flow-chart stops

Incomplete pathway

Possible complete pathway

Complete pathway

/ / / /

Site 

Worker

Construction 

Worker Resident Trespasser/ Recreational User

Site 

Worker

Construction 

Worker Resident

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 6-2

Preliminary Conceptual Site Model

AOI 1 & AOI 2 Airfield and Wash Rack

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ 

Recreational User

1. The resident receptor refers to an off-site

resident.

2. Current risk practice suggests the exposure

pathway for dermal contact is insignificant

compared to ingestion, but supporting data is

sparse and continues to be studied.

Notes:

31
Media

SOURCE PATHWAY RECEPTOR

AOI 3

Fire Training and 

Mobile Fire 

Extinguishers 

Discharge

PFAS in 

surface soil

PFAS in 

subsurface 

soil

Human 

activities

Precipitation/ 

run-off

Leaching/ 

infiltration

Airborne soil 

particulate

Surface soil 

at AOI

Surface 

water/ 

sediment

Subsurface 

soil

Shallow 

groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Flow-chart continues

Partial/ possible flow

Flow-chart stops

Incomplete pathway

Possible complete pathway

Complete pathway

/ / / /

Site 

Worker

Construction 

Worker Resident Trespasser/ Recreational User

Site 

Worker

Construction 

Worker Resident

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 6-3

Preliminary Conceptual Site Model

AOI 3 Butler Building Parking FTA

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ 

Recreational User

1. The resident receptor refers to an off-site

resident.

2. Current risk practice suggests the exposure

pathway for dermal contact is insignificant

compared to ingestion, but supporting data is

sparse and continues to be studied.

Notes:

32
PFAS Preliminary Assessment Report

Stockton AASF, California

33

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 Stockton AASF. The PA findings are based

on the information presented in Appendix A and Appendix B.

7.1 Findings

Three AOIs related to potential PFAS release were identified (Table 7-1) at Stockton AASF during

the PA (Figure 7-1).

Table 7-1: AOIs at Stockton AASF

Area of Interest Name Used by Release Dates

AOI 1 Airfield CAARNG Potentially as early as

1992

AOI 2 Wash Rack CAARNG Potentially as early as

1992

AOI 3 Butler Building Parking

Area CAARNG Potentially as early as1992

The AASF Hangar at Stockton AASF was determined to have no suspected PFAS release to the

environment. The hangar neither contains an AFFF deluge system nor stores AFFF historically or

presently.

Numerous potential off-facility sources of PFAS were considered in the local area surrounding

Stockton AASF. These include:

· Montezuma Fire Station #18-2 – stores AFFF at the fire station and conducts nozzle testing

using AFFF in the fuel containment system and wash rack area within the Stockton

Metropolitan Airport property

· French Camp Fire Station #11-1 – may conduct fire training activities utilizing AFFF

· Stockton Metropolitan Airport Runway 29R/11L – may be the location of historical fire training

events and is the known location of an aircraft crash in which emergency response used an

unknown foam extinguishant

· Private Aviation Companies – Atlantic Aviation, Amazon, A.G. Spanos Jet Center, Big Valley

Aviation, Inc., and Vintage Aircraft all maintain hangars/facilities that may contain or utilize

AFFF

· Aramark Uniform and Career Apparel, LLC – conducts industrial activities related to uniform

manufacturing and fireproofing, which may involve PFAS-containing chemicals

The potential off-facility sources are located in the upstream surface water flow path, with the

exception of French Camp Fire Station #11-1, which is located downstream from the AASF.

However, the off-facility sources are located in the downgradient or cross-gradient groundwater

flow path and are not expected to have impacts on groundwater at the AASF.

Based on information obtained during the PA at these AOIs, there is potential for exposure to

PFAS contamination in media at or near the facility. The preliminary CSMs are shown on Figures

6-2 and 6-3, which presents the potential receptors and media impacted.
PFAS Preliminary Assessment Report

Stockton AASF, California

34

7.2 Uncertainties

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

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

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

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

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

The conclusions of this PA are predominantly based on the information provided during interviews

with personnel who had direct knowledge of PFAS use at the facility. Sometimes, the provided

information was vague or conflicted with other sources. Gathered information has a degree of

uncertainty due to the absence of written documentation, the time passed since PFAS were first

used (1969 to present), and a reliance on personal recollection. Inaccuracies may arise in

potential PFAS release locations, dates of release, volume of releases, and the concentration of

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

how PFAS may enter the environment continually evolves.

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

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

interviewed for the same potential source area, and potential source areas were visually

inspected.

The following Table 7-2 summarizes the uncertainties associated with the PA.

Table 7-2: Uncertainties

Area of Interest Source of Uncertainty

AOI 1: Airfield It could not be confirmed whether the Tri-MaxTM fire

extinguishers stationed on the airfield were currently

equipped with 3% or 6% AFFF.

AOI 2: Wash Rack It is unknown if foam or soap and in what quantity were

used to wash out the aircraft tanks at the wash rack.

Minimal spills of AFFF may have occurred from refilling

the Tri-MaxTM fire extinguishers, but this could not be

confirmed by site records.

AOI 3: Butler Building

Parking Area

Construction plans for the Butler Building were unable

to be obtained, so exact locations of soil excavations

and refill could not be confirmed.

General The AASF personnel interviewed could not recall

specific dates of fire training exercises, but they could

recall the occurrence of fire training exercises during

their entire tenure at the facility. The longest tenure

extended back to 1992, so it is unknown what occurred

prior to 1992.

The contents of the Tri-MaxTM fire extinguishers used

during fire training activities were uncertain, and

interviewees had differing recollections. According to

information gathered during interviews with AASF

personnel, the contents of the extinguishers may have
PFAS Preliminary Assessment Report

Stockton AASF, California

35

Area of Interest Source of Uncertainty

contained either 3% AFFF, 6% AFFF, dishwashing soap,

or water depending on the dates of usage.

7.3 Potential Future Actions

Based on the documented absence (1992 to present) of the use or release of AFFF from the

AASF Hangar, evidence does not indicate that current or former ARNG activities having

contributed PFAS contamination to soil, groundwater, surface water, or sediment at that location.

Interviews and records (covering 1992 to present) indicate that current or former ARNG activities

may have resulted in potential PFAS releases at the three AOIs identified during the PA. Based

on the preliminary CSMs developed for the AOIs, there is potential for receptors to be exposed to

PFAS contamination in soil, surface water, sediment, and groundwater at these AOIs. Table 7-3

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

investigation under the CERCLA process and undergo an SI.

Table 7-3: PA Findings Summary

Area of Interest AOI Location Rationale Potential Future

Action

AOI 1: Airfield 37°53’10.6”N;

121°14’29.9”W

Confirmed usage of AFFF

during annual training exercises

by interviewees with direct

knowledge

Proceed to an SI,

focus on soil,

groundwater,

surface water,

sediment

AOI 2: Wash Rack 37°53’07.6”N;

121°14’36.9”W

Confirmed usage of AFFF

during annual training exercises

by interviewees with direct

knowledge and potential PFAS

releases from the washing of

aircraft tanks and refilling of TriMaxTM fire extinguishers

Proceed to an SI,

focus on soil,

groundwater,

surface water,

sediment

AOI 3: Butler

Building Parking

Area FTA

37°53’10.8”N;

121°14’39.2”W

Confirmed usage of AFFF

during annual training exercises

by interviewees with direct

knowledge

Proceed to an SI,

focus on soil,

groundwater,

surface water,

sediment

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

potential migration of PFAS contamination off the facility, and the availability of resources.
PFAS Preliminary Assessment Report

Stockton AASF, California

36

This Page Intentionally Blank
­ Figure 7-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Preliminary Assessment for PFAS at Stockton AASF, CA

12/5/2019

12/5/2019

12/5/2019

MS

ST

RG

GIS BY

CHK BY

PM

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

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

12/5/2019

1:12,000

Q:\Projects\ENV\GEARS\GEO\ARNG PFAS\900-CAD-GIS\920-GIS or Graphics\MXD\CA\Stockton_AASF\Fig_7-1_Stockton_AASF_Summary.mxd

Summary of Findings

12420 Milestone Center Drive

Germantown, MD 20876

Stockton Metropolitan 

Airport Runway 29R/11L

French Camp Fire

Station #11-1

Wash Rack

Butler Building Parking

Fire Training Area Airfield

Aramark Uniform and

Career Apparel, LLC Montezuma Fire

Station Wash Rack

Montezuma Fire

Station #18-2

AASF Hangar French Camp Slough

Rydberg Creek

AOI 2

AOI 3 AOI 1

Legend

Area of Interest

Potential PFAS Release

No Suspected Release

Facility Boundary

Water Body

River/Stream

Canal/Ditch

0 500 1,000 2,000

Feet

37
PFAS Preliminary Assessment Report

Stockton AASF, California

38
PFAS Preliminary Assessment Report

Stockton AASF, California

39

8. References

Adanta-ECM Joint Venture. 2018. Remedial Action Completion Report for In-Situ Chemical

Injection (ISCO) & Vapor Energy Generation (VEG), California Army National Guard (CA

ARNG), Field Maintenance Shop #24, 8020 South Airport Way, Stockton, California. February.

California Water Board, 2019. Groundwater Ambient Monitoring and Assessment Program

Online Tools.

https://www.waterboards.ca.gov/water_issues/programs/gama/online_tools.html. (Accessed

November 2019).

City of Stockton. 2019. Water Supplies.

http://www.stocktongov.com/government/departments/municipalUtilities/utilWater.html.

(Accessed May 2019).

Environmental Cost Management, Inc. 2015. Final Summary Letter Report 180 Day ISCO PostInjection Groundwater Monitoring, California Army National Guard Stockton Field Maintenance

Shop #24, Stockton, California. March 30, 2015.

ECM Consultants. 2018. 2018 First Semi-Annual Groundwater Monitoring Report, California Army

National Guard – Field Maintenance Shop #24, 8010 Airport Drive, Stockton, California,

SWRCB Global ID T0607700742. July 3.

HazCon, 2017. Spill Prevention, Control, and Countermeasure Plan, Stockton Army Aviation

Support Facility, 2000 Stimson Road, Stockton, California 95206. May 2017.

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

Practice. January 2018.

National Oceanic and Atmospheric Administration (NOAA). n.d. Stockton California Normals,

Means, and Extremes. https://wrcc.dri.edu/cgi-bin/clilcd.pl?ca23237. (Accessed April 2019).

National Transportation Safety Board, 1969. Aircraft Accident Report, Seaboard World Airlines,

Inc., Douglas DC-8-63F, N8634. Stockton Metropolitan Airport, Stockton California. October

16, 1969. https://www.ntsb.gov/investigations/AccidentReports/Pages/AAR7024.aspx.

Oneida Total Integrated Enterprises (OTIE) 2010. Final Groundwater Monitoring Well Installation

and First Quarter 2010 Groundwater Monitoring Report, California Army National Guard

Stockton Field Maintenance Shop #24, Stockton, California. September.

OTIE, 2012. Semiannual 2012 Groundwater Monitoring Report, California Army National Guard

Field Maintenance Shop #24, Stockton, California. September.

OTIE,2013. Technical Letter Report for MIP Groundwater Investigation, Groundwater Monitoring

Well Installation, Field Maintenance Shop #24, Stockton California Army National Guard

Complex, 8010 South Airport Way, Stockton, California. May.

Stockton East Water District. 2019. Encouraging the Use of Surface Water.

https://sewd.net/encouraging-the-use-of-surface-water/. (Accessed June 2019).

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

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

URS Corporation, 2007. Site Investigation Report, Underground Storage Tank Location at the

Field Maintenance Shop #24, California Army National Guard, Stockton, CA. Final. December.
PFAS Preliminary Assessment Report

Stockton AASF, California

40

Versar, Inc., 2004. Preliminary Assessment/Site Investigation Update Report California Army

National Guard Facility. Final. September.

White, Thomas. “Re: CA ARNG Leasing Documents” Message to Stephanie Tjan. 2019. E-mail.
PFAS Preliminary Assessment Report

Stockton AASF, California

Appendix A

Data Resources
PFAS Preliminary Assessment Report

Stockton AASF, CA

Data resources will be provided separately on CD. Data resources for Stockton AASF include: 

Environmental Data Resources, Inc. Geocheck Report

• 2019 Environmental Data Resources, Inc. Geocheck Report for Stockton AASF, CA

CAARNG Leasing Information

• 2019 CA ARNG Leasing Documents E-mail from Tom White (CAARNG Real Estate

Manager) to Stephanie Tjan (AECOM)

Material Safety Data Sheets

• 2019 Safety Data Sheet – Fire Service Plus, Inc. FireAde MIL 6% AFFF Fire Fighting Foam

Previous CA ARNG Stockton Investigations

• 2018 First Semi-Annual Groundwater Monitoring Report, California Army National Guard –

Field Maintenance Shop #24, 8010 Airport Drive, Stockton, California

• 2018 Remedial Action Completion Report for In-Situ Chemical Injection (ISCO) and Vapor

Energy Generation (VEG), California Army National Guard, Field Maintenance Shop #24,

8020 South Airport Way, Stockton, California

• 2018 Soil Gas Investigation Report, Field Maintenance Shop #24, California Army National 

Guard, Stockton, California

Spill Prevention, Control, and Countermeasure Plan

• 2017 Spill Prevention, Control, and Countermeasure Plan, Stockton Army Aviation Support

Facility, 2000 Stimson Road, Stockton California 95206
PFAS Preliminary Assessment Report

Stockton AASF, California

Appendix B

Preliminary Assessment Documentation
PFAS Preliminary Assessment Report

Stockton AASF, California

Appendix B.1

Interview Records
PA Interview Questionnaire - Other Facility:_StocktonAASF_____

 Interviewer:__ST_____________

 Date/Time:_3/6/19____________

Interviewee:_David Cardoza_____________

Title: Administrative Captain,, Instructor, EMS 

Program Director

Phone Number:_209-464-5234____________

Email:__captain184@montezumafire.com______

Can your name/role be used in the PA Report? Y or N 

Can you recommend anyone we can interview?

Y or N __________________________

Roles or activities with the Facility/Years working at the Facility:

PFAS Use: Identify accidental/intentional release locations, time frame of release, frequency of releases, 

storage container size (maintenance, fire training, firefighting, buildings with suppression systems (as 

builts), fueling stations, crash sites, pest management, recreational, dining facilities, metals plating, or 

waterproofing). How are materials ordered/purchased/disposed/shared with others?

Fire department trains on the airport FD property in a fuel tank area that has a containment system. They 

train ~annually even now. The training events consist of 5 min of shooting foam. They use 3% AFFF.

They also trained at their wash rack a couple times around the 90s-2000. 
PA Interview Questionnaire - Environmental Manager Facility:_Stockton AASF_____

Interviewer:__ST___________

Date/Time:___3/6/19_________

Interviewee:__ ____________

Title:__Safety Officer_________

Phone Number:_________________________

Email:_______________________________

Can your name/role be used in the PA Report? Y or N

Can you recommend anyone we can interview?

Y or N __________________________

1. Roles or activities with the Facility/years working at the Facility.

Been at facility since 1998

2. Where can I find previous facility ownership information?

Building built in 1992 but the other building has been here since WWII

Mike Gamino would have facility ownership info

3. What can you tell us about the history of PFAS including aqueous film forming foam (AFFF) at the 

Facility? Was it used for any of the following activities, circle all that apply and indicate years of active 

use, if known? Identify these locations on a facility map. 

Maintenance

Fire Training Areas Three FTAs – 1) outside Butler Building, 2) wash rack, 3) airfield

Firefighting (Active Fire)

Crash

Fire Suppression Systems (Hangers/Dining Facilities)

Fire Protection at Fueling Stations

Non-Technical/Recreational/ Pest Management

Metals Plating Facility

Waterproofing Uniforms (Laundry Facilities)

Other Altas Hangar, Spanos Jet Center, Airport FD

4. Fill out CSM Information worksheet with the Environmental Manager. 

5. Are any current buildings constructed with AFFF dispensing systems or fire suppression systems? 

What are the AFFF/suppression system test requirements? What is the frequency of testing the 

AFFF/suppression system? Do you have “As Built” drawings for the buildings?

No
PA Interview Questionnaire - Environmental Manager Facility:_Stockton AASF_____

Interviewer:__ST___________

Date/Time:___3/6/19_________

6. Are fire suppression systems currently charged with AFFF or have they been retrofitted for use of 

high expansion foam? If retrofitted, when was that done?

No

7. How is AFFF procured? Do you have an inventory/procurement system that tracks use? 

They would purchase with government purchasing card. The disposal would be taken care of by 

the environmental compliance team.

8. What type of AFFF has been/is being used (3%, 6%, Mil Spec Mil-F-24385, High Expansion)? 

Manufacturer (3M, Dupont, Ansul, National Foam, Angus, Chemguard, Buckeye, Fire Service Plus)?

See copies of SDS. However, the SDS given to us may not be the same as what was used historically.

9. Where is the AFFF stored? How is it stored (tanks, 55-gallon drums, 5-gallon buckets)? What 

size are the storage tanks? Is the AFFF stored as a mixed solution (3% or 6%) or concentrated 

material?

5 gallon buckets in HAZMAT locker, concentrated version

10. How many FTAs are/were on this facility and where are they? Locate on a map. How many FTAs 

are active and inactive? For inactive FTAs, when was the last time that fire training using AFFF 

was conducted at them? 

Exercises were conducted approximately annually until ~2010; afterwards the exercises slowed down 

because the Tri-Maxes started breaking down (they never received regular safety inspection).

D. Harvey believes the training was done with air and water not foam because the Tri-Maxes were 

hard to refill with foam. This was decided by the Fire Department. His knowledge goes back to the 

2000s. 
PA Interview Questionnaire - Environmental Manager Facility:_Stockton AASF_____

Interviewer:__ST___________

Date/Time:___3/6/19_________

11. When a release of AFFF occurs during a fire training exercise, now and in the past, how is the 

AFFF cleaned and disposed of? Were retention ponds built to store discharged AFFF? Was the 

AFFF trickled to the sanitary sewer or left in the pond to infiltrate?

Just left it to evaporate

12. Can you recall specific times when city, county, and/or state personnel came on-post for training? If so, 

please state which state/county agency or military entity? Do you have any records, including 

photographs to share with us?

Municipal FD only came on-site for the FTA #1. FD just facilitated, and the foam for the exercise was 

provided by ARNG. 

13. Did military routinely or occasionally fire train off-post? List the units that you can recall used/trained 

at various areas.

Not near facility

14. Did individual units come with their own safety personnel, did they also bring their own AFFF? Was 

training with AFFF part of these exercises? How were emergencies handled under these circumstances?

No

15. Are there specific emergency response incident reports (i.e., aircraft or vehicle 

crash sites and fires)? If so, may we please copy these reports? Who (entity) was 

the responder?

Can’t remember
PA Interview Questionnaire - Environmental Manager Facility:_Stockton AASF_____

Interviewer:__ST___________

Date/Time:___3/6/19_________

16. Do you have records of fuel spill logs? Was it common practice to wash away fuel spills with

AFFF? Is/was AFFF used as a precaution in response to fuel releases or emergency runway 

landings to prevent fires?

Never washed fuel spills with AFFF.

17. Was AFFF used for forest fires or fire management on-post/off-post? If so, please describe what 

happened and who was involved?

No

18. Are there mutual aid/use agreements between county, city, and local fire department? Please list, even 

if informal. If formalized, may we have a copy of the agreement?

No

19. Can you provide any other locations where AFFF has been stored, released, or used (i.e. hangars, 

buildings, fire stations, firefighting equipment testing and maintenance areas, emergency response

sites, storm water/surface water, waste treatment plants, and AFFF ponds)?

Tri-Maxes used to be stored on airfield and at fuel farm.

20. Are you aware of any other creative uses of AFFF? If so, how was AFFF used? What entities were 

involved?

D. Harvey – back in the 90s, they used foam (or soap) on aircraft tanks to wash them out at the wash rack. 

This happened until 5-6 years ago when CalFire told them to stop using foam because of environmental 

reasons. 
PA Interview Questionnaire - Environmental Manager Facility:_Stockton AASF_____

Interviewer:__ST___________

Date/Time:___3/6/19_________

21. Are there past studies you are aware of with environmental information on plants/animals/ 

groundwater/soil types, etc., such as Integrated Cultural Resources Management Plans or Integrated 

Natural Resources Management Plans?

22. What other records might be helpful to us (environmental compliance, investigation records, admin 

record) and where can we find them?

23. Do you have or did you have a chrome plating shop on base? What were/are the years of operation

of that chrome plating shop?

24. Do you know whether the shop has/had a foam blanket mist suppression system or used a fume 

hood for emissions control? If foam blanket mist suppression was used, where was the foam 

stored, mixed, applied, etc.?

25. How is off-spec AFFF disposed (used for training, turned in, or given to a local Fire Station)? If 

applicable, do you know the name of the vendor that removes off-spec AFFF? Do you have copies of 

the manifest or B/L?
PA Interview Questionnaire - Environmental Manager Facility:_Stockton AASF_____

Interviewer:__ST___________

Date/Time:___3/6/19_________

26. Do you recommend anyone else we can interview? If so, do you have contact information for them?

Mike Gamino
PA Interview Questionnaire - Other Facility:_Stockton AASF________

Interviewer:__ST______________

Date/Time:__3/6/19______________

Interviewee:___Mike Gamino__________

Title:_1SG, ECO__________________

Phone Number:__209-983-5339____________

Email:___michael.j.gamino.mil@mail.mil__

Can your name/role be used in the PA Report? Y or N 

Can you recommend anyone we can interview?

Y or N __________________________

Roles or activities with the Facility/Years working at the Facility:

Mechanic up until 2015 and then environmental officer; been at facility since 1992

PFAS Use: Identify accidental/intentional release locations, time frame of release, frequency of releases, 

storage container size (maintenance, fire training, firefighting, buildings with suppression systems (as 

builts), fueling stations, crash sites, pest management, recreational, dining facilities, metals plating, or 

waterproofing). How are materials ordered/purchased/disposed/shared with others?

Confirmed three FTAs on-facility

Muncipal FD also came to the airfield last year to do some training with aircraft but never released foam. 

Training was just to get familiar with aircraft emergencies. 

Fire training was conducted approximately yearly with one Tri-Max being used up per event.

Believes the foam was 3%. The new milspec is currently 6% but that came in only recently. 
PFAS Preliminary Assessment Report

Stockton AASF, California

Appendix B.2

Visual Site Inspection Checklists












PFAS Preliminary Assessment Report

Stockton AASF, California

Appendix B.3

Conceptual Site Model Information



PFAS Preliminary Assessment Report

Stockton AASF, California

Appendix C

Photographic Log
Appendix C - Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS

Stockton AASF Stockton, California

Preliminary Assessment Report

Stockton AASF

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

Photograph No. 1

Description:

Fire training area shown just 

past the fence and west of the 

Butler Building; some 

flooding and vegetative stress 

is observed

Orientation:

Northwest

Date 3/6/2019

Time 9:42

Photograph No. 2

Description:

Wash rack area with 

HAZMAT locker and TriMax 30 mobile fire 

extinguisher in distance

Orientation:

Southeast

Date 3/6/2019

Time 9:45

AECOM Page 1 of 3
Appendix C - Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS

Stockton AASF Stockton, California

Preliminary Assessment Report

Stockton AASF

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

Photograph No. 3

Description:

Tri-Max 30 mobile fire 

extinguishers found parked 

nearby the AASF Airfield

Orientation:

Southwest

Date 3/6/2019

Time 9:46

Photograph No. 4

Description:

Multiple 5-gallon buckets of 

6% AFFF FireAde 2000 Mil 

Spec observed in the 

HAZMAT locker

Orientation:

Northwest

Date 3/6/2019

Time 9:47

AECOM Page 2 of 3
Appendix C - Photographic Log

Army National Guard, Preliminary 

Assessment for PFAS

Stockton AASF Stockton, California

Preliminary Assessment Report

Stockton AASF

Perfluorooctane-Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide

Photograph No. 5

Description:

Fire training area shown on 

the airfield

Orientation:

Northeast

Date 3/6/2019

Time 9:51

Photograph No. 6

Description:

A dry chemical (non-AFFF) 

fire extinguisher observed in 

the Maintenance Hangar

Orientation:

Southeast

Date 3/6/2019

Time 10:07

AECOM Page 3 of 3