FINAL

Site Inspection Report 

Camp Roberts

San Miguel, California

Site Inspection for Perfluorooctanoic acid (PFOA), 

Perfluorooctanesulfonic acid (PFOS), Perfluorohexanesulfonic 

acid (PFHxS), Perfluorononanoic acid (PFNA), 

Hexafluoropropylene oxide dimer acid (HFPO-DA), and 

Perfluorobutanesulfonic acid (PFBS) at ARNG Installations, 

Nationwide

September 2023

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED
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Camp Roberts, San Miguel, California

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Table of Contents

Executive Summary ..............................................................................................................ES-1

1. Introduction ..................................................................................................................1-1

1.1 Project Authorization .............................................................................................1-1

1.2 SI Purpose ............................................................................................................1-1

2. Facility Background ......................................................................................................2-1

2.1 Facility Location and Description...........................................................................2-1

2.2 Facility Environmental Setting ...............................................................................2-1

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

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

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

2.2.4 Climate........................................................................................................2-4

2.2.5 Current and Future Land Use......................................................................2-4

2.2.6 Sensitive Habitat and Threatened/ Endangered Species.............................2-4

2.3 History of PFAS Use..............................................................................................2-5

2.4 Potable Well Sampling ..........................................................................................2-6

3. Summary of Areas of Interest .......................................................................................3-1

3.1 AOI 1 East Garrison Old Fire Station.....................................................................3-1

3.1.1 East Garrison Old Fire Station.....................................................................3-1

3.1.2 Army Airfield AFFF Storage.........................................................................3-1

3.2 AOI 2 East Garrison Old FTA ................................................................................3-1

3.3 AOI 3.....................................................................................................................3-2

3.3.1 Main Garrison FTA 2 and Building 7020 ......................................................3-2

3.4 AOI 4 CR FD Fire Station and Shipping Container................................................3-2

3.5 AOI 5 CR FD Building 3000 and Main Garrison Fuel Station.................................3-3

3.5.1 CR FD Building 3000 and Main Garrison Fuel Station.................................3-3

3.6 AOI 6.....................................................................................................................3-3

3.6.1 TUAS Hangar Building 17002 and NPS Airfield Shed AFFF Storage...........3-3

4. Project Data Quality Objectives ....................................................................................4-1

4.1 Problem Statement ...............................................................................................4-1

4.2 Information Inputs .................................................................................................4-1

4.3 Study Boundaries..................................................................................................4-1

4.4 Analytical Approach...............................................................................................4-1

4.5 Data Usability Assessment....................................................................................4-2

5. Site Inspection Activities ...............................................................................................5-1

5.1 Pre-Investigation Activities.....................................................................................5-1

5.1.1 Technical Project Planning ..........................................................................5-1

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

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

5.2 Soil Borings and Soil Sampling .............................................................................5-2

5.3 Permanent Well Installation and Groundwater Sampling.......................................5-3

5.4 Synoptic Water Level Measurements ....................................................................5-4

5.5 Surveying..............................................................................................................5-4

5.6 Investigation-Derived Waste..................................................................................5-4

5.7 Laboratory Analytical Methods ..............................................................................5-5
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5.8 Deviations from SI QAPP Addendum ....................................................................5-5

6. Site Inspection Results .................................................................................................6-1

6.1 Screening Levels...................................................................................................6-1

6.2 Soil Physicochemical Analyses .............................................................................6-2

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

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

6.3.2 AOI 1 Groundwater Analytical Results.........................................................6-2

6.3.3 AOI 1 Conclusions ......................................................................................6-2

6.4 AOI 2.....................................................................................................................6-3

6.4.1 AOI 2 Soil Analytical Results .......................................................................6-3

6.4.2 AOI 2 Groundwater Analytical Results.........................................................6-3

6.4.3 AOI 2 Conclusions ......................................................................................6-3

6.5 AOI 3.....................................................................................................................6-3

6.5.1 AOI 3 Soil Analytical Results .......................................................................6-4

6.5.2 AOI 3 Groundwater Analytical Results.........................................................6-4

6.5.3 AOI 3 Conclusions ......................................................................................6-4

6.6 AOI 4.....................................................................................................................6-4

6.6.1 AOI 4 Soil Analytical Results .......................................................................6-5

6.6.2 AOI 4 Groundwater Analytical Results.........................................................6-5

6.6.3 AOI 4 Conclusions ......................................................................................6-5

6.7 AOI 5.....................................................................................................................6-5

6.7.1 AOI 5 Soil Analytical Results .......................................................................6-5

6.7.2 AOI 5 Conclusions ......................................................................................6-5

6.8 AOI 6.....................................................................................................................6-6

6.8.1 AOI 6 Soil Analytical Results .......................................................................6-6

6.8.2 AOI 6 Conclusions ......................................................................................6-6

7. Exposure Pathways......................................................................................................7-1

7.1 Soil Exposure Pathway .........................................................................................7-1

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

7.1.2 AOI 2...........................................................................................................7-2

7.1.3 AOI 3...........................................................................................................7-2

7.1.4 AOI 4...........................................................................................................7-2

7.1.5 AOI 5...........................................................................................................7-2

7.1.6 AOI 6...........................................................................................................7-3

7.2 Groundwater Exposure Pathway...........................................................................7-3

7.2.1 AOI 1...........................................................................................................7-3

7.2.2 AOI 2...........................................................................................................7-3

7.2.3 AOI 3...........................................................................................................7-3

7.2.4 AOI 4...........................................................................................................7-4

7.3 Surface Water and Sediment Exposure Pathway ..................................................7-4

7.3.1 AOI 1 - AOI 4...............................................................................................7-4

7.3.2 AOI 5 & AOI 6 .............................................................................................7-4

8. Summary and Outcome................................................................................................8-1

8.1 SI Activities............................................................................................................8-1

8.2 Outcome ...............................................................................................................8-1

9. References...................................................................................................................9-1
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Appendices

Appendix A Data Usability Assessment and Validation Reports

Appendix B Field Documentation

B1. Log of Daily Notice of Field Activities

B2. Sampling Forms and Well Development Forms

B3. Survey Data

Appendix C Photographic Log

Appendix D TPP Meeting Minutes

Appendix E Boring Logs and Well Construction Forms 

Appendix F Analytical Results

Appendix G Laboratory Reports

Figures

Figure 2-1 Facility Location

Figure 2-2 Facility Topography

Figure 2-3 Groundwater Features

Figure 2-4 Groundwater Elevations, May 2021

Figure 2-5 Surface Water Features

Figure 3-1 Areas of Interest

Figure 5-1 Site Inspection Sample Locations – AOI 1, AOI 2

Figure 5-2 Site Inspection Sample Locations – AOI 3, AOI 4, AOI 5

Figure 5-3 Site Inspection Sample Locations – AOI 6 

Figure 6-1 PFOA Detections in Soil - AOI 1 thru AOI 5

Figure 6-2 PFOS Detections in Soil - AOI 1 thru AOI 5

Figure 6-3 PFBS Detections in Soil - AOI 1 thru AOI 5

Figure 6-4 PFOA, PFOS, and PFBS Detections in Soil - AOI 6

Figure 6-5 PFHxS Detections in Soil - AOI 1 thru AOI 5

Figure 6-6 PFNA Detections in Soil - AOI 1 thru AOI 5

Figure 6-7 PFHxS and PFNA Detections in Soil - AOI 6

Figure 6-8 PFOA, PFOS, and PFBS Detections in Groundwater

Figure 6-9 PFHxS and PFNA Detections in Groundwater

Figure 7-1 Conceptual Site Model, AOI 1

Figure 7-2 Conceptual Site Model, AOI 2

Figure 7-3 Conceptual Site Model, AOI 3

Figure 7-4 Conceptual Site Model, AOI 4

Figure 7-5 Conceptual Site Model, AOI 5

Figure 7-6 Conceptual Site Model, AOI 6

Tables

Table ES-1 Screening Levels (Soil and Groundwater)

Table ES-2 Summary of Site Inspection Findings and Recommendations

Table 5-1 Site Inspection Samples by Medium

Table 5-2 Soil Boring Depths

Table 5-3 Permanent Monitoring Well Screen Intervals and Groundwater Elevations

Table 6-1 Screening Levels (Soil and Groundwater)

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

Table 6-3 PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Shallow Subsurface Soil
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Table 6-4 PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Deep Subsurface Soil

Table 6-5 PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Groundwater

Table 8-1 Summary of Site Inspection Findings and Recommendations
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Acronyms and Abbreviations

% percent

°C degrees Celsius

°F degrees Fahrenheit

μg/kg micrograms per kilogram

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 

CAARNG California Army National Guard

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CoC chain of custody

CR FD Camp Roberts Fire Department

CSL Chemistry Systems Laboratory

CSM conceptual site model

DA Department of the Army

DoD Department of Defense

DO dissolved oxygen

DQO data quality objective

DUA data usability assessment

DWR Department of Water Resources

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

ERB equipment rinsate blank

FedEx Federal Express

FTA Fire Training Area

GRPS Ground Penetrating Radar Systems

HDPE high-density polyethylene 

HFPO-DA hexafluoropropylene oxide dimer acid

HSA hollow stem auger

IDW investigation-derived waste

ITRC Interstate Technology Regulatory Council

LC/MS/MS liquid chromatography with tandem mass spectrometry

MIL-SPEC military specification

NELAP National Environmental Laboratory Accreditation Program

NOAA National Oceanic and Atmospheric Administration

ng/L nanograms per liter

ORP oxidation-reduction potential

OSD Office of the Secretary of Defense

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid
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PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PID photoionization detector

PQAPP Programmatic UFP-QAPP

PVC polyvinyl chloride

QA quality assurance

QAPP Quality Assurance Project Plan

QC quality control

QSM Quality Systems Manual

RI Remedial Investigation

RWQCB Regional Water Quality Control Board

SAIC Science Applications International Corporation

SI Site Inspection

SL screening level

SOP standard operating procedure

TOC total organic carbon

TPP Technical Project Planning

UFP Uniform Federal Policy

US United States

USACE United States Army Corps of Engineers

USCS Unified Soil Classification System

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

USGS United States Geological Survey
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Executive Summary

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

Inspections (SIs) on the current or potential historical use of per- and polyfluoroalkyl substances 

(PFAS) with a focus on the six compounds presented in the memorandum from the Office of the 

Secretary of Defense (OSD) dated 6 July 2022 (Assistant Secretary of Defense, 2022). The six 

compounds listed in the OSD memorandum include perfluorooctanesulfonic acid (PFOS), 

perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid 

(PFHxS), hexafluoropropylene oxide dimer acid (HFPO-DA)1

, and perfluorobutanesulfonic acid 

(PFBS). These compounds are collectively referred to as “relevant compounds” throughout the 

document and the applicable screening levels (SLs) are provided in Table ES-1. 

The PA identified six Areas of Interest (AOIs) where PFAS-containing materials may have been 

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

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

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

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

compounds. This SI was completed at the Camp Roberts in San Miguel, California and 

determined further evaluation under the Comprehensive Environmental Response, 

Compensation, and Liability Act (CERCLA) is warranted for AOI 1, AOI 2, AOI 3, and AOI 5; no 

further evaluation is warranted for AOI 4 and AOI 6 at this time. Camp Roberts will also be referred 

to as the “facility” throughout this document. 

Camp Roberts occupies 42,784 acres of land and is bordered on the west by the unincorporated 

community of Heritage Ranch and on the east by the unincorporated community of San Miguel. 

Camp Roberts includes three main types of use areas, including cantonment areas, training 

areas, and airfield operational areas. Facilities at Camp Roberts are concentrated in two 

cantonment areas, the Main Garrison and East Garrison. The Main Garrison and East Garrison 

are located in the northeastern portion of Camp Roberts, near the facility’s main gate, and are 

separated by the Salinas River and US Route 101. Training areas include weapons ranges and 

impact areas, open areas for heavy and light maneuver training, and land navigation areas. These 

areas are in the southern, central, and northern portion of the property. Firing ranges occupy areas

in the western and central portions of Camp Roberts. The three airfield operational areas include 

McMillan Airfield, located at the southernmost end of Camp Roberts, the East Garrison Airfield, 

located towards the northern end of the facility, north of US Route 101, and the Parade Field, 

which is also used as a landing field for rotary wing aircraft.

The PA identified six AOIs for investigation during the SI phase. SI sampling results from the six

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

the results of this SI, further evaluation under CERCLA is warranted in a Remedial Investigation

(RI) for AOI 1, AOI 2, AOI 3, and AOI 5; no further evaluation is warranted for AOI 4 and AOI 6 at 

this time. 

1 Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly referred to as GenX) was not 

included as an analyte at the time of this SI. Based on the conceptual site model (CSM) developed during the PA and revised based 

on SI findings, the presence of HFPO-DA is not anticipated at the facility because HFPO-DA is generally not a component of military 

specification (MIL-SPEC) aqueous film forming foam (AFFF) and based on its history including distribution limitations that restricted 

use of GenX, it is generally not a component of other products the military used. In addition, it is unlikely that GenX would be an 

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

Analyteb 

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ Commercial 

Composite Worker

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater)

(ng/L)a

PFOA 19 250 6

PFOS 13 160 4 

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

bgs = below ground surface; μg/kg = micrograms per kilogram; ng/L = nanograms per liter

a.) Assistant Secretary of Defense, 2022. Risk Based Screening Levels in Groundwater and Soil using United States Environmental Protection 

Agency’s (USEPA’s) Regional Screening Level Calculator. Hazard Quotient (HQ) = 0.1. 6 July 2022. 

b.) Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly referred to as GenX) was not included 

as an analyte at the time of this SI. Based on the CSM developed during the PA and revised based on SI findings, the presence of HFPODA is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC AFFF and based on its history including 

distribution limitations that restricted use of GenX, it is generally not a component of other products the military used. In addition, it is 

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

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

AOI Potential 

Release Area

Soil –

Source Area

Groundwater –

Source Area Future Action

1 East Garrison Old Fire Station Proceed to RI 

Army Airfield AFFF Storage N/A Proceed to RI

2 East Garrison Old FTA Proceed to RI

3

Main Garrison FTA 2 Proceed to RI

Building 7020 N/A Proceed to RI

4 CR FD Fire Station and Shipping 

Container No further action

5 

CR FD Building 3000 Warehouse N/A No further action

Main Garrison Fueling Station N/A Proceed to RI

6 

Tactical Unmanned Aerial Systems 

(TUAS) Hangar Building 17002 N/A No further action

NPS Airfield Shed AFFF Storage N/A No further action

Legend:

N/A = not applicable 

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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1. Introduction

1.1 Project Authorization

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

(PAs) and Site Inspections (SIs) on the current or potential historical use of per- and 

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

memorandum from the Office of the Secretary of Defense (OSD) dated 6 July 2022 (Assistant 

Secretary of Defense, 2022). The six compounds listed in the OSD memorandum will be referred 

to as “relevant compounds” throughout this document and include perfluorooctanoic acid (PFOA), 

perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), perfluorononanoic 

acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA)1

, and perfluorobutanesulfonic

acid (PFBS) at ARNG facilities nationwide. The ARNG performed this SI at the Camp Roberts in 

San Miguel, California. Camp Roberts is also referred to as the “facility” throughout this document.

The SI project elements were performed in compliance with Comprehensive Environmental 

Response, Compensation, and Liability Act (CERCLA; United States [US] Environmental 

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

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

compliance with US Department of the Army (DA) requirements and guidance for field 

investigations.

1.2 SI Purpose

A PA was performed at Camp Roberts that identified six Areas of Interest (AOIs) where PFAScontaining materials may have been used, stored, disposed, or released historically (AECOM 

Technical Services, Inc. [AECOM], 2019). The objective of the SI is to identify whether there has 

been a release to the environment from the AOIs identified in the PA and determine whether 

further investigation is warranted, a removal action is required to address immediate threats, or 

no further action is required based on screening levels (SLs) for the relevant compounds.

1 Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly referred to as GenX) was not 

included as an analyte at the time of this SI. Based on the conceptual site model (CSM) developed during the PA and revised based 

on SI findings, the presence of HFPO-DA is not anticipated at the facility because HFPO-DA is generally not a component of military 

specification (MIL-SPEC) aqueous film forming foam (AFFF) and based on its history including distribution limitations that restricted 

use of GenX, it is generally not a component of other products the military used. In addition, it is unlikely that GenX would be an 

individual chemical of concern in the absence of other PFAS.
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2. Facility Background

2.1 Facility Location and Description

Camp Roberts is in southern Monterey and northern San Luis Obispo Counties, in central 

California. The facility is situated along the eastern foothills of the Santa Lucia Mountains, in the 

valley of the Salinas River, which flows towards the northwest through the property. The facility is 

about 12 miles north of Paso Robles and 25 miles east of the Pacific Ocean (Figure 2-1). The 

geographic coordinates and surface elevation at the main gate of the facility are 35 47’53”; 120 

44’40” and 620 feet above mean sea level (amsl), respectively. 

Camp Roberts occupies 42,784 acres of land and is bordered on the west by the unincorporated 

community of Heritage Ranch and on the east by the unincorporated community of San Miguel. 

Camp Roberts includes three main types of use areas, including cantonment areas, training 

areas, and airfield operational areas. Facilities at Camp Roberts are concentrated in two 

cantonment areas, the Main Garrison and East Garrison. The Main Garrison and East Garrison 

are located in the northeastern portion of Camp Roberts, near the facility’s main gate, and are 

separated by the Salinas River and US Route 101. Training areas include weapons ranges and 

impact areas, open areas for heavy and light maneuver training, and land navigation areas. These 

areas are in the southern, central, and northern portion of the property. Firing ranges occupy areas 

in the western and central portions of Camp Roberts. The three airfield operational areas include 

McMillan Airfield, located at the southernmost end of Camp Roberts, the East Garrison Airfield, 

located towards the northern end of the facility, north of US Route 101, and the Parade Field, 

which is also used as a landing field for rotary wing aircraft.

Camp Roberts was originally developed as an Army replacement training center in 1941 

(Environmental Resources Management Inc. [ERM], 1995). The facility was inactivated and then 

reverted to caretaker status from 1946 to 1950. After 1950, Camp Roberts was reactivated during 

the Korean Conflict. Camp Roberts was again inactivated and reverted to caretaker status from 

1954 until it was officially closed by the Army in 1970. Although the facility was active during the 

Vietnam War, it was never officially brought out of inactive status. On 2 April 1971, the California 

ARNG (CAARNG) received control of the site under a license from the Army to establish a 

Reserve Component Training Center.

2.2 Facility Environmental Setting

Camp Roberts is in a region of rolling hills and steep mountainous valleys between the Pacific 

Ocean and the Santa Lucia Mountains. Much of the facility is grasslands and oak woodlands. The 

area surrounding the facility is a mix of agriculture, rural residential, recreation, and open spaces. 

Surface elevations at Camp Roberts range from 600 feet amsl in the area where higher plains 

meet the Nacimiento River Basin area to 1,800 feet amsl in steep slope areas of the southwestern 

portion of the training area (Figure 2-2). The Nacimiento River traverses through the Main 

Garrison and meets the Salinas River near US Route 101, within the boundaries of Camp Roberts. 

Ephemeral tributary streams of the Nacimiento River are located in the northern portion of the 

facility.

2.2.1 Geology

Camp Roberts is situated in the southern portion of the California Coast Ranges section of the 

Pacific Border physiographic province, which stretches over 400 miles from the Klamath 

Mountains in Humbolt County to the Traverse Ranges in Santa Barbara County (FPM Group, Ltd, 

2008). The topography of Camp Roberts is characteristic of the Coast Ranges, with terrain varying 

from low plains and river valleys to steep hills. A series of folds and faults follow a northwest trend 
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as a result of mountain forming episodes that occurred from the late Pliocene into the mid 

Pleistocene.

The most prevalent geologic units at Camp Roberts are composed of Quaternary or Late Tertiary 

semi- to unconsolidated layers of sand, gravel, sandstone, and conglomerate deposits that are 

consistent with stream (alluvial) depositional environments (Figure 2-3). The low and high plains 

are composed of Quaternary (Recent and Late Pleistocene) alluvium and the Paso Robles 

Formation, respectively. The Paso Robles Formation accumulated extensively after withdrawal of 

the Tertiary Sea and is mainly a mixture of semi- to unconsolidated alternating layers of 

conglomerate and sandstone, with smaller amounts of mudstone (US Geological Survey [USGS], 

1974). Other units residing beneath the lower hills in the northern portion of Camp Roberts include 

alternating layers of massive- to thinly bedded Tertiary mudstones, shales, and sandstones of the 

Pancho Rico, Santa Margarita, and Tierra Redonda Formations, and an unnamed Cretaceous 

marine unit (Chemistry Systems Laboratory [CSL], 1983).

The southern Salinas Valley lies mainly on the Salinian block, a structural basement comprised 

of granitic and high-grade metamorphic rocks (USGS, 1974). The Salinian block is bounded by 

the San Andreas and Rinconada fault zones, which are approximately 17.5 miles and 8 miles 

northeast and west of Camp Roberts, respectively. Both faults are active, right-lateral slip faults 

capable of generating significant earthquakes.

Soil borings completed during the SI found poorly graded sands and silts as the dominant lithology 

of the unconsolidated sediments below Camp Roberts. The borings were completed at depths 

between 75 feet to 120.5 feet below ground surface (bgs). Interbedded lenses of cobbles and 

clays were also observed in the borings ranging from a few inches to approximately 6 feet in 

thickness. Differences in lithology between boreholes may be due to the lateral variability in deltaic 

deposits and channelized flow. These observations are consistent with the understood 

depositional environment of the region. Boring logs are presented in Appendix E.

2.2.2 Hydrogeology

Camp Roberts lies within the Salinas Valley Groundwater Basin, which is subdivided into the Paso 

Robles Area Subbasin and the Upper Valley Aquifer Subbasin. Camp Roberts is situated within 

the Paso Robles Area Subbasin, which is bordered on the north by the Upper Valley Aquifer 

Subbasin, on the east by the Temblor Range, on the south by the La Panza Range, and on the 

west by the Santa Lucia Range (California Department of Water Resources [DWR], 2004). The 

limited amounts of groundwater used from the basin are from mostly unconfined Holocene age 

alluvium deposits found as deep as 130 feet bgs, but generally less than 30 feet bgs. Although 

permeability is considered high, limited amounts of groundwater are extracted for use. The most 

important source of groundwater in the basin is found in Pleistocene age Paso Robles Formation, 

which reaches a thickness of 2,000 feet (DWR, 2004). Groundwater recharge of the basin is 

provided by infiltration, seepage from streams, and return flow from irrigation. The estimated 

annual recharge rate for the Paso Robles Area Sub-basin is 47,000 acre-feet, and specific yield 

values in the Paso Robles Area Subbasin range from 7-11 percent (%), with an average yield of 

9%. The estimated usable storage capacity of the Paso Robles Area Subbasin is estimated to be 

1.7 million acre-feet (DWR, 2004). 

Groundwater from the Paso Robles Area Subbasin is the main source of water for the facility. 

Groundwater supply wells located throughout the Salinas Valley region have typical intake depths 

of over 200 feet (DWR, 2004). Groundwater features are presented on Figure 2-3. 

Camp Robert’s potable water is sourced from groundwater wells situated within the boundaries 

of the facility. The primary source of drinking water for the facility is provided from wells located in 

the Main Garrison. These wells include Well Numbers C-3-A, C-4A, and C-5A, which are active 

wells situated adjacent to the Nacimiento River. Well depths range from 350 feet to 450 feet bgs. 
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During a 2012 SI, the depth to water at the northwest end of the Main Garrison and at the East 

Garrison ranged from approximately 82 feet to 85 feet bgs. At the southwest end of the Main 

Garrison, the depth to water was 29 feet to 36 feet bgs (American Integrated Services, Inc., 2012). 

Several logs for wells installed near McMillian Airfield recorded static water levels that ranged

from 60 feet to 78 feet bgs.

In the southeast area of Camp Roberts, there are three wells, two public supply wells, and one 

potable well at the Satellite Communication. The Satellite Communication is a US Army Signal 

Activity - Presidio of Monterey Enclave that is surrounded by Camp Roberts but administratively 

distinct. 

Depths to water measured in May 2021 during this SI ranged from 62.54 feet to 94.91 feet bgs

(571.38 feet and 539.28 feet amsl). Groundwater elevations from the SI are presented on Figure 

2-4. Because depths to water were only measured from four widely spaced locations, one of which 

appears to be screened in a perched layer (AOI02-01), it is difficult to determine a localized 

groundwater gradient. As such, groundwater flow directions are assumed to be consistent with 

those outlined in the Camp Roberts PA (AECOM, 2019). Inferred groundwater flow directions are 

presented on Figure 2-3. 

2.2.3 Hydrology

Waters flowing through or collecting on land surfaces within the boundaries of Camp Roberts 

drain through four watersheds: Kemp Canyon-San Antonio, Portuguese Canyon-Salinas River, 

San Marcos Creek, and the Nacimiento River Watersheds. The Nacimiento River watershed 

occupies the largest portion of surface areas within Camp Robert’s property boundary. Surface 

water features are presented on Figure 2-5.

The major water courses that pass through the cantonment areas of Camp Roberts are the 

Salinas and the Nacimiento Rivers. All surface water draining from Camp Roberts flows to the 

Salinas River or one of its tributaries, which include the San Antonio and Nacimiento Rivers and 

San Marcos Creek. Waters in the Salinas River flow through Monterey County to the Monterey 

Bay National Marine Sanctuary in the Pacific Ocean. 

The Nacimiento River drains approximately 70% of the land surfaces covering Camp Roberts 

(CSL, 1983). The river flows in a northeastern direction, along the north side of the Main Garrison’s 

developed area, and joins the Salinas River approximately 2 miles north of the facility’s main gate. 

Surface waters from the Main Garrison, the southern portion of Camp Roberts, and McMillan 

Airfield drain into the Nacimiento River and its smaller tributaries. The Nacimiento River and San 

Antonio River flow year-round and are controlled by the dams upstream. The Salinas River is 

seasonal and dries up in the summer months. 

Surface waters originating in the East Garrison drain to the Salinas River and its smaller 

tributaries. The Salinas River is more than 175 miles long and flows from the southeast to the 

northwest in the vicinity of Camp Roberts. The Salinas River is designated by the National Marine 

Fisheries Service as a critical habitat for steelhead.

Several seasonal wetlands that include clay flats and vernal pools supporting a fairy shrimp 

population are situated within Camp Roberts boundaries. There are approximately 64 acres of 

ponds and reservoirs of which about 35, 24, and 10 acres are classified as wetlands, seasonal 

wetlands, and clay flats, respectively (Science Applications International Corporation [SAIC], 

2011). The majority of stream bank areas situated along the Salinas River are also classified as 

wetlands.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 2-4

2.2.4 Climate 

Camp Roberts is in a Mediterranean climate zone characterized by warm, dry weather from June 

through September, and mild, rainy weather from November through March. The average annual 

rainfall is approximately 13 inches, with the majority of the rainfall occurring between late fall and 

early spring (National Oceanic and Atmospheric Administration [NOAA], 2022). Summer 

temperatures average 87 degrees Fahrenheit (°F) to 94 oF, and the daily high temperature can 

frequently exceed 110 oF. Winter temperatures average 59oF to 66oF during the day, with average 

nightly temperatures to as low as 33o F. Snowfall at the facility is rare, but frost occurs occasionally. 

2.2.5 Current and Future Land Use

Camp Roberts serves as a year-round training site for the CAARNG. The cantonment area of the 

facility is developed with numerous buildings and related infrastructure, including paved and 

unpaved roadways and parking areas. The cantonment area occupies a small percentage of the 

total area controlled by the CAARNG. The other, much larger lands are occupied by and used as 

training ranges. The ranges are generally in vegetated sloping areas, mostly to the west of the 

cantonment areas. Access to lands under Camp Robert’s purview is restricted and inaccessible 

to the general public in most areas. 

The mission of Camp Roberts is to provide training, administrative, and logistical site support to 

US forces (CAARNG, 2004). Camp Roberts also provides emergency support services for the 

State of California in the event of an emergency or disaster. Reasonably anticipated future land 

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

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

The following amphibians, birds, crustaceans, fish, insects, mammals, plants, reptiles, and snails 

are federally endangered, threatened, proposed, and/ or are listed as candidate species in 

Monterey and San Luis Obispo Counties, California (US Fish and Wildlife Service [USFWS], 

2021a and 2021b). Although this list includes all species generally found in the region, CAARNG 

has indicated that only four of these species have been identified at the facility (California Condor, 

Vernal Pool Fairy Shrimp, Purple Amole, and San Joaquin Kit Fox).

• Amphibians: California tiger Salamander, Ambystoma californiense (endangered); 

California red-legged frog, Rana draytonii (threatened); Santa Cruz long-toed salamander, 

Ambystoma macrodactylum croceum (endangered); Arroyo toad, Anaxyrus californicus

(endangered)

• Birds: Short-tailed albatross, Phoebastria albatrus (endangered); Yellow-billed Cuckoo, 

Coccyzus americanus (threatened); California condor, Gymnogyps californianus

(endangered); Least Bell's vireo, Vireo bellii pusillus (endangered); Southwestern willow 

flycatcher, Empidonax traillii extimus (endangered); California least tern, Sterna antillarum 

browni (endangered); Western snowy plover, Charadrius nivosus nivosus (threatened); No 

Common Name, Coccyzus americanus ssp. Occidentalis (species of concern); California 

clapper rail, Rallus longirostris obsoletus (endangered); Marbled murrelet, Brachyramphus 

marmoratus (threatened)

• Conifers and Cycads: Gowen cypress, Cupressus goveniana ssp. goveniana (threatened)

• Crustaceans: Conservancy fairy shrimp, Branchinecta conservation (endangered); Vernal 

pool fairy shrimp, Branchinecta lynchi (threatened); Longhorn fairy shrimp, Branchinecta 

longiantenna (endangered)
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 2-5

• Fishes: Delta smelt, Hypomesus transpacificus (threatened); South-Central Coast 

Steelhead Ohcorhynchus mykiss (threatened), Tidewater goby, Eucyclogobius newberryi

(endangered); longfin smelt, Spirinchus thaleichthys (candidate)

• Flowering Plants: Santa Cruz tarplant, Holocarpha macradenia (threatened); Marsh 

Sandwort, Arenaria paludicola (endangered); San Benito evening-primrose, Camissonia 

benitensis (threatened); Salt marsh bird's-beak, Cordylanthus maritimus ssp. Maritimus

(endangered); Coastal dunes milk-vetch, Astragalus tener var. titi (endangered); Menzies' 

wallflower, Erysimum menziesii (endangered); Beach layia, Layia carnosa (endangered); 

Monterey clover, Trifolium trichocalyx (endangered); Monterey gilia, Gilia tenuiflora ssp. 

arenaria (endangered); Monterey spineflower, Chorizanthe pungens var. pungens

(threatened); Clover (Tidestrom''s) lupine, Lupinus tidestromii (endangered); Hickman's 

potentilla, Potentilla hickmanii (endangered); California jewelflower, Caulanthus californicus

(endangered); Yadon's piperia, Piperia yadonii (endangered); Contra Costa goldfields, 

Lasthenia conjugens (endangered); Purple amole, Chlorogalum purpureum (threatened); 

San Joaquin wooly-threads, Monolopia (=Lembertia) congdonii (endangered); California 

seablite, Suaeda californica (endangered); Spreading navarretia, Navarretia fossalis

(threatened); Kern mallow, Eremalche kernensis (endangered); Morro manzanita, 

Arctostaphylos morroensis (threatened); Gambel's watercress, Rorippa gambellii

(endangered); Indian Knob mountainbalm, Eriodictyon altissimum (endangered); La 

Graciosa thistle, Cirsium loncholepis (endangered); Pismo clarkia, Clarkia speciosa ssp. 

immaculata (endangered); Chorro Creek bog thistle, Cirsium fontinale var. obispoense

(endangered); Nipomo Mesa lupine, Lupinus nipomensis (endangered); Gaviota Tarplant, 

Deinandra increscens ssp. villosa (endangered)

• Insects: Monarch butterfly, Danaus plexippus (candidate); Unsilvered fritillary, Speyeria 

adiaste (resolved taxon); Smith's blue butterfly, Euphilotes enoptes smithi (endangered); 

Kern primrose sphinx moth, Euproserpinus Euterpe (threatened)

• Mammals: Southern sea otter, Enhydra lutris nereis (threatened); Giant kangaroo rat, 

Dipodomys ingens (endangered); San Joaquin kit fox, Vulpes macrotis mutica

(endangered); Buena Vista Lake ornate Shrew, Sorex ornatus relictus (endangered); Tipton 

kangaroo rat, Dipodomys nitratoides nitratoides (endangered); Swift fox, Vulpes velox

(resolved taxon); Morro Bay kangaroo rat, Dipodomys heermanni morroensis (endangered)

• Reptiles: Blunt-nosed leopard lizard, Gambelia silus (endangered); Leatherback sea turtle, 

Dermochelys coriacea (endangered); Olive ridley sea turtle, Lepidochelys olivacea

(endangered); Giant garter snake, Thamnophis gigas (threatened)

• Snails: Morro shoulderband snail, Helminthoglypta walkeriana (endangered)

2.3 History of PFAS Use

Ten potential release areas were identified at Camp Roberts during the PA and post-PA activities 

where AFFF may have been used or released historically (AECOM, 2021b). Camp Roberts 

includes multiple areas where, as early as the 1970s, AFFF may have been used during fire 

training activities: East Garrison Old Fire Station, East Garrison Old Fire Training Area (FTA), 

Main Garrison FTA 2. Additionally, AFFF may have been stored in several areas at the facility: 

Army Airfield AFFF Storage, Camp Roberts Fire Department (CR FD) Fire Station Building 7020, 

Current CR FD Fire Station (Building 4050) and Shipping Container, CR FD Building 3000 

Warehouse and Main Garrison Fueling Point, Tactical Unmanned Aerial Systems (TUAS) Hangar 

Building 17002, and Naval Postgraduate School (NPS) Airfield Shed. Although there are no 

documented releases at AFFF storage areas, AFFF may have been released due to incidental 

spills or leaks. The potential release areas were grouped into six AOIs based on proximity to one 

another and presumed groundwater flow. A description of each AOI is presented in Section 3.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 2-6

2.4 Potable Well Sampling

In March 2017, groundwater from the majority of Camp Roberts’ drinking water well network was 

analyzed for a subset of 18 PFAS compounds. PFAS are a large group of related chemicals, 

including PFOA, PFOS, PFHxS, PFNA, and PFBS. The samples were collected at spigots from 

various facilities at Camp Roberts. A tabulated data set is provided in the PA report (AECOM, 

2019). The specific chemicals PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in any 

sample.
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Camp Roberts Facility Location

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Camp Roberts

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12420 Milestone Center Drive

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Facility Topography

Base Map: USGS The National Map: National

Boundaries Dataset, 3DEP Elevation Program,

0 1 2 4

Miles

Legend

Facility Boundary

AECOM 2-8
!C(

!C(

&<

&<

!C(

!C(

&<

Q

QPc

P

QPc

QPc

Ku-Ep

QPc

grMz

Qoa

M

QPc

Q

SanAntonio Ri ver

H uerhuero Creek

BigSandy Creek

Na cimiento River

Estrella River

San Marcos Cre ek

Hames Creek

Sa n Jac ni ot Cree k

BlackKey

M ustardCree k

SnakeCreek

D ip Cre ek

Salinas River

Legend

Facility Boundary

Water Body

River/Stream

Inferred Groundwater

Flow Direction

Geology

Q - Quaternary alluvium

deposits

Qoa - Quaternary older

alluvium deposits

QPc - Pliocenepleistocene sandstone,

shale, and gravel

deposits

P - Pliocene marine

sandstone, siltsone,

shale, and conglomerate

M - Miocene marine

sandstone, shale,

siltsone, and breccia

Ku-Ep - Paleocenecretaceous

unidfferentiated Marine

Sedimentary and

Metasedimentary rocks

grMz - Mesozoic granite,

quartz monzonite,

granodiorite, and quartz

diorite.

Wells

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(PWS) Well

&<

Non-PWS Potable Well

&<

Non-Potable Well

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Groundwater Features

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

and the GIS User Community

0 1 2 4

Miles

AECOM 2-9
!?

!?

!?

!?

AOI01-01

539.28

AOI02-01

571.38*

AOI03-01

551.53

AOI04-01

562.69

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12420 Milestone Center Drive

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Groundwater Elevations, May 2021

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

and the GIS User Community

0 650 1,300 2,600

Feet

Legend

!? Soil Boring/Permanent

Monitoring Well

551.53 = Groundwater Elevation in

feet NAVD88.

* = Well screened in perched

groundwater

AECOM 2-10
Lower

Huerhuero

Creek

Watershed

Nacimiento

Reservoir-Nacimiento

River Watershed

Nacimiento River

Watershed

Kemp Canyon-San

Antonio River

Watershed

Portuguese 

Canyon-Salinas 

River Watershed

Hames Creek Watershed

San Marcos Creek Watershed

Bridge

Canyon-Salinas

River Watershed

Lower Big

Sandy Creek

Watershed

SanAntonio Ri ver

HuerhueroC r e ek

Nacimiento River

Big

Sandy Cree k

Nacimiento River

San Marcos C re ek

Hames Creek

M ustard Creek

Es trellaRiver

SnakeCreek

Dip Cre ek

Salinas River

0 1 2 4

Miles

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Water Body

Wetland

River/Stream

Surface Water Flow

Direction

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Surface Water Features

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and the GIS User Community

AECOM 2-11
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 2-12

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Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 3-1

3. Summary of Areas of Interest 

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

disposed, or released historically. Based on the PA findings, ten potential release areas were 

identified at Camp Roberts and grouped into six AOIs (AECOM, 2019 and AECOM, 2021b). AOI 

1 through AOI 4 were identified during PA, and two AFFF storage areas were added as new AOIs 

(AOI 5 – AOI 6) during post-PA activities (AECOM, 2021b). The potential release areas are shown 

on Figure 3-1.

3.1 AOI 1 East Garrison Old Fire Station

AOI 1 consists of two potential release areas. These areas are described below. 

3.1.1 East Garrison Old Fire Station

AOI 1 is the East Garrison Old Fire Station near Camp Roberts Army Airfield. The Old Fire Station 

was a Fire and Rescue Station associated with the Old FTA (discussed in Section 3.2). Although 

the use of AFFF at this location could not be confirmed, more substantial fire training activities 

occurred as early as 1976, and AOI 1 could be a potential release area. The timeframe during 

which the training activities occurred is commensurate with the use of AFFF for fire training 

purposes.

AOI 1 lies within the Salinas River watershed, and all surface water is drained by tributaries to the 

Salinas River. PFAS are water soluble and can migrate readily from soil to groundwater or surface 

water via leaching and run-off. If releases to surface and subsurface soil occurred, migration from 

surface soil at AOI 1 to groundwater and waters in the Salinas River is possible. Drinking water is 

supplied by potable wells in the Main Garrison, and two active potable water wells are located 

downgradient of the East Garrison. In addition, precipitation infiltrating into the gravel-covered 

areas at AOI 1 may cause migration from surface and subsurface soil to groundwater and surface 

water. 

3.1.2 Army Airfield AFFF Storage

The Camp Roberts Army Airfield is located in the East Garrison, which is east of the Salinas River 

and US Route 101, and includes a 3,656-foot improved surface runway, with 300 feet of “over 

run” on both ends. The approximate geographic coordinates and elevation of the center of the 

airfield runway are 35°48'51.44"N; 120°44'36.44"W and 630 feet amsl, respectively. During the 

PA site visit, four Tri-MaxTM 30 crash fire rescue carts were observed to be stored in an area 

historically used for parking aircraft at the Airfield. Although there are no documented releases of 

AFFF in this storage area, AFFF may have been released due to incidental spills or leaks.

Surface water and groundwater flow to the west, towards the Salinas River in the East Garrison.

No stormwater drainage infrastructure was observed in the areas visited during the PA within the

vicinity of the Airfield.

3.2 AOI 2 East Garrison Old FTA

AOI 2 is the East Garrison Old FTA. The Old FTA is located south of the Old Fire Station Site in 

the East Garrison cantonment area of Camp Roberts, to the east of US Route 101, the Salinas 

River, and the airfield. The approximate geographic coordinates and elevation of the general area 

are 35°48'57.085” N; 120°44'28.714"W, and 636 feet amsl, respectively. The CR FD reportedly 

used this area in the East Garrison for fire training exercises. Although the use of AFFF could not 

be confirmed, more substantial fire training activities occurred as early as 1976, and AOI 2 could 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 3-2

be a potential release area. The timeframe during which the training activities occurred is 

commensurate with the use of AFFF for fire training purposes.

AOI 2 lies within the Salinas River watershed, and all surface water is drained by tributaries to the 

Salinas River. If releases to surface and subsurface soil occurred, migration from surface soil at 

AOI 2 to groundwater and waters in the Salinas River is possible. Drinking water is supplied by 

potable wells in the Main Garrison, and two active potable water wells are located downgradient 

of the East Garrison. In addition, precipitation infiltrating into the gravel-covered areas at AOI 2

may cause the migration from surface and subsurface soil to groundwater and surface water. 

3.3 AOI 3

AOI 3 consists of two potential release areas. The areas are described below.

3.3.1 Main Garrison FTA 2 and Building 7020

AOI 3 is the Main Garrison FTA 2 area, including the former CR FD Fire Station Building 7020. 

The Main Garrison FTA 2 is located in the northwestern portion of the Main Garrison cantonment 

area, on the east side of Utah Avenue and north of the former CR FD Fire Station Building 7020. 

The approximate geographic coordinates and elevation of the area is 35°48'06.16"N; 

120°45'07.15"W and 640 feet amsl. The former CR FD Fire Station Building 7020 is located at 

35°48'3.979"N; 120°45'4.894"W, adjacent to FTA 2. Although the use of AFFF could not be 

confirmed, more substantial fire training activities occurred prior to 2001, and as such, the area 

could be a potential release area.

Surface water at AOI 3 flows to the northeast, towards a small drainage ditch that captures and 

carries water towards the Salinas River. The river is located approximately 0.5 miles to the east 

of AOI 3. If releases to surface soil at AOI 3 occurred, they had potential to migrate from surface 

soil to surface water via run-off and to groundwater via leaching. The nearest groundwater wells 

to AOI 3 are to the west of the AOI. Inferred groundwater flow is to the north/northeast. 

3.4 AOI 4 CR FD Fire Station and Shipping Container

CR’s current Fire Station is Building 4050. The CR FD Fire Station is located mid-way along the 

southwest-facing boundary of the Parade Field on Arizona Boulevard, between Avenue 11 and 

Avenue 12; the approximate geographic coordinates are 35°48'51.44"N; 120°44'36.44"W. During 

the PA site visit, a tactical firefighting truck, which is equipped to carry up to 2,500 gallons of a 

mixture of water and foam of which 65 gallons constitute Class B AFFF, was observed at the CR 

FD Fire Station Building. 

A steel storage container located adjacent to the CR FD Building 4050 is used for storing and 

servicing Tri-MaxTM 30 crash fire rescue carts and for storing AFFF. The geographic coordinates 

of the storage container are 35°47'28.97"N, 120°44'36.19"W. According to CR FD staff 

interviewed, the crash carts were historically filled with AFFF in an area outside the door of the 

container. Staff that were interviewed indicated that incidental leaks and spills may have occurred; 

however, details specific to the filling of carts were not recalled. The area was observed to be 

gravel covered.

Incidental spills of AFFF could migrate through gravel covered areas into surface soil and 

subsurface soil to groundwater via leaching. Nearby tributaries may have been impacted by 

surface water runoff from AOI 4. Surface and groundwater flow are to the north/northeast, towards 

the Salinas River. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 3-3

3.5 AOI 5 CR FD Building 3000 and Main Garrison Fuel Station

AOI 5 consists of two potential release areas. The areas are described below. 

3.5.1 CR FD Building 3000 and Main Garrison Fuel Station

AOI 5 includes CR FD Building 3000 Warehouse and Main Garrison Fueling Point, which are

located in the southeast corner of the Parade Field, near the intersection of Montana Boulevard 

and Wyoming Avenue. The approximate geographic coordinates of the approximate center of the 

area are 35°46'13.06"N; 120°44'02.49"W.

During the PA site visit, 19 5-gallon plastic containers of various brands of AFFF were observed 

to be stored on shelves in the eastern corner of Building 3000, and one Tri-MaxTM 30 crash fire 

rescue cart was observed at the Fueling Point area. The floor of the warehouse is concrete, but 

much of the area around Building 3000 is not paved. The Fueling Point area is on concrete slab. 

Groundwater beneath AOI 5 flows to the east/northeast, towards the Salinas River.

Although no incidental spills of stored AFFF were reported, if spills occurred, AFFF could have 

migrate to the subsurface through cracks in the concrete or off the concrete to unpaved areas at 

AOI 5. Precipitation may cause migration from concrete surfaces, surface soil, and subsurface 

soil to groundwater. Surface waters may have also migrated to Salinas River, which is located 

approximately 2,000 feet to the south of the warehouse. 

3.6 AOI 6

AOI 6 consists of two potential release areas. The areas are described below. 

3.6.1 Hangar Building 17002 and NPS Airfield Shed AFFF Storage 

AOI 6 includes Hangar Building 17002 and NPS Airfield Shed, located at the south end of 

McMillan Airfield, which is in the southern portion of Camp Roberts, between East Perimeter Road 

and Generals Road. The airfield and related facilities are accessible only to facility operations 

staff and personnel. 

During the PA site visit, two Tri-MaxTM 30 crash fire rescue carts were observed to be stored in

the Hangar Building 17002, and one 5-gallon bucket of AFFF concentration was observed in the 

NPS Airfield Shed. AFFF was stored on concrete slab or in paved area. 

Surface water and groundwater flow to the south/southeast into tributaries of San Marcos Creek, 

which eventually empties to the Salinas River. No stormwater drainage infrastructure was 

observed in the areas visited during the PA.

Although no incidental spills of stored AFFF were reported, AFFF could have migrated to the 

subsurface through cracks in the concrete or off the concrete to unpaved areas at AOI 6. If AFFF 

were released, precipitation may have caused migration from concrete surfaces, surface soil, and 

subsurface soil to groundwater. Surface water in San Marcos Creek may be potentially impacted 

by PFAS. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 3-4

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!C(

Main Garrison 

Fire Training Area 2

Camp Roberts 

Fire Dept Fire Station & Shipping Container

Camp Roberts 

Fire Department Building 3000

Camp Roberts 

Main Garrison Fuel Station

East Garrison 

Old Fire Station

East Garrison 

Camp Roberts Army Airfield

East Garrison 

Old Fire Training Area

Fire Station-Building 7020

Salinas River

Nacimien to

River

AOI 4

AOI 3

AOI 1

AOI 2

AOI 5

C-1 &<

&<

NPS Airfield Shed AFFF Storage

TUAS Hangar Building 17002 AFFF Storage

AOI 6

0 800 1,600 3,200

Feet

­ Figure 3-1

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Area of Interest

Potential Release Area

Facility Boundary

Water Body

Wetland

River/Stream

Surface Water Flow Direction

Inferred Groundwater Flow Direction

Wells

&<

Non-PWS Potable Well

!C( Public Water System (PWS) Well

AOI 4

AOI 3

AOI 1

AOI 2

AOI 5

AOI 6

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Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 4-1

4. Project Data Quality Objectives

As identified during the Data Quality Objective (DQO) process and outlined in the SI Quality 

Assurance Project Plan (QAPP) Addendum (AECOM, 2021b), the objective of the SI is to identify 

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

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

address immediate threats, or whether no further action is warranted. This SI evaluated 

groundwater and soil for presence or absence of relevant compounds at each of the sampled 

AOIs.

4.1 Problem Statement

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

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

SLs are presented in Section 6.1 of this report.

4.2 Information Inputs

Primary information inputs included:

• The PA for Camp Roberts (AECOM, 2019);

• Previous environmental investigations performed at the facility;

• Analytical data collected as part of a facility potable well sampling event in March 2017 

(AECOM, 2019);

• Analytical data from groundwater and soil samples collected as part of this SI in accordance 

with the site-specific Uniform Federal Policy (UFP)- QAPP Addendum (AECOM, 2021b);

and

• Field data collected during the SI, including groundwater elevation and water quality 

parameters measured at the time of sampling.

4.3 Study Boundaries

The scope of the SI was bounded by the property limits of the facility (Figure 2-2). Off-facility sampling 

was not included in the scope of this SI. If future off-facility sampling is required, the proper 

stakeholders will be notified, and necessary rights of entry will be obtained by ARNG with property 

owner(s). The SI scope was bounded vertically by the observed depths of the surficial groundwater 

table. Temporal boundaries were limited to the spring season, which was the earliest available time 

field resources were available to complete the study.

4.4 Analytical Approach

Samples were analyzed by Pace Analytical Gulf Coast, accredited under the Department of 

Defense (DoD) Environmental Laboratory Accreditation Program (ELAP; Accreditation Number 

74960) and the National Environmental Laboratory Accreditation Program (NELAP; Certificate

Number 01955). Data were compared to applicable SLs within this document and decision rules 

as defined in the SI QAPP Addendum (AECOM, 2021b).
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 4-2

4.5 Data Usability Assessment

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

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

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

methods, the assessment determines whether project execution and the resulting data have met 

installation-specific DQOs. Both sampling and analytical activities are considered to assess 

whether the collected data are of the right type, quality, and quantity to support the decisionmaking (Department of Defense [DoD], 2019a; DoD, 2019b; USEPA, 2017).

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

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

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

requirements of the SI QAPP Addendum (AECOM, 2021b).
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-1

5. Site Inspection Activities

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

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

in accordance with the following approved documents:

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

(PQAPP) dated March 2018 (AECOM, 2018a);

• Final Programmatic Accident Prevention Plan dated July 2018 (AECOM, 2018b); 

• Final Preliminary Assessment Report, Camp Roberts, San Miguel, California (AECOM, 

2019);

• Final Site Safety and Health Plan, Camp Roberts, San Miguel, California (AECOM, 2021a); 

and

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

Camp Roberts, San Miguel, California (AECOM, 2021b).

The SI field activities were conducted from 10 to 27 May 2021 and consisted of utility clearance, 

hollow stem auger drilling, soil sample collection, permanent monitoring well installation, 

groundwater sample collection, and land surveying. Field activities were conducted in accordance 

with the SI QAPP Addendum (AECOM, 2021b), except as noted in Section 5.8.

The following samples were collected during the SI and analyzed for a subset of 18 compounds

by liquid chromatography with tandem mass spectrometry (LC/MS/MS) compliant with Quality 

Systems Manual (QSM) 5.3 Table B-15 to fulfill the project DQOs:

• Twenty-eight (28) soil samples from 20 surface soil and deeper boring locations;

• Four grab groundwater samples from four permanent well locations; 

• Seventeen (17) quality assurance (QA)/quality control (QC) samples.

Figure 5-1 through Figure 5-3 provide the sample locations for all media across the facility. Table 

5-1 presents the list of samples collected for each media. Field documentation is provided in 

Appendix B. A Log of Daily Notice of Field Activity was completed throughout the SI field 

activities, which is provided in Appendix B1. Sampling forms and well development forms are 

provided in Appendix B2, land survey data are provided in Appendix B3. Additionally, a 

photographic log of field activities is provided in Appendix C.

5.1 Pre-Investigation Activities

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

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

water. Details for each of these activities are presented below.

5.1.1 Technical Project Planning

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

(USACE, 2016) defines four phases to project planning: 1.) defining the project phase; 2.) 

determining data needs; 3.) developing data collection strategies; and 4.) finalizing the data 

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

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

address the AOIs identified in the PA. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-2

A combined TPP Meeting 1 and 2 was held on 10 February 2021, prior to SI field activities. The 

combined TPP Meeting 1 and 2 was conducted in general accordance with EM 200-1-2. The 

stakeholders for this SI include the ARNG, CAARNG, USACE, California Regional Water Quality 

Control Board (RWQCB) – Central Coast Region. Stakeholders were provided the opportunity to 

make comments on the technical sampling approach and methods at the combined TPP Meeting 

1 and 2. The outcome of the combined TPP Meeting 1 and 2 was memorialized in the SI QAPP 

Addendum (AECOM, 2021b).

A TPP Meeting 3 was held after the field event to discuss the results of the SI. Meeting minutes 

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

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

5.1.2 Utility Clearance

AECOM’s drilling subcontractor, Cascade Technical Services, LLC. placed a ticket with the 

DigAlert utility clearance provider to notify them of intrusive work on 5 May 2021. Additionally, 

AECOM contracted Ground Penetrating Radar Systems (GPRS), a private utility location service, 

to perform utility clearance. GPRS performed utility clearance of the proposed boring locations on 

10 May 2021 with input from the AECOM field team and Camp Roberts facility staff. General 

locating services and ground-penetrating radar were used to complete the clearance. Additionally, 

the first 5 feet of each boring were pre-cleared using a hand auger to verify utility clearance in 

shallow subsurface where utilities would typically be encountered.

5.1.3 Source Water and Sampling Equipment Acceptability

A potable water source at Camp Roberts was sampled on 18 March 2021 to assess usability for 

decontamination of drilling equipment. Results of the sample collected (CR-PW-01) confirmed 

this source to be acceptable for use in this investigation; therefore, it was used throughout the 

field activities. Specifically, the samples were analyzed by LC/MS/MS compliant with QSM 5.3

Table B-15. The results of the decontamination water sample associated with the decontamination 

water source used during the SI are provided in Appendix F. A discussion of the results is 

presented in the DUA (Appendix A).

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

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

was provided in the Standard Operating Procedures (SOPs) appendix to the SI QAPP Addendum 

(AECOM, 2021b). Prior to the start of field work each day, a Sampling Checklist was completed 

as an additional layer of control. The checklist served as a daily reminder to each field team 

member regarding the allowable materials within the sampling environment.

5.2 Soil Borings and Soil Sampling

Borings were installed in grass areas where applicable, to avoid disturbing concrete or asphalt 

surfaces. Shallow and deep borings were advanced via hollow stem auger (HSA) drilling, in 

accordance with the SI QAPP Addendum (AECOM, 2021b). A split-spoon sampler was used to 

collect soil samples at the target depths. A hand auger was used to collect surface soil samples

and soil from the top 5 feet of soil borings, in accordance with AECOM utility clearance 

procedures. The soil boring locations are shown on Figure 5-1 through Figure 5-3, and depths 

are provided on Table 5-2 and Table 5-3. During the SI field work, AECOM was informed that the 

location of proposed AOI04-01 might be in conflict with a future building. As a result, the drilling 

location of AOI04-01 was shifted to a new location within 50 feet of the proposed location.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-3

In general, three discrete soil samples were collected from the vadose zone for chemical analysis 

from each soil boring: one surface soil sample (0 to 2 feet bgs), one subsurface soil sample 

approximately 1 foot above the groundwater table, and one subsurface soil sample at 10 feet bgs.

The soil cores were continuously logged for lithological descriptions by an AECOM field geologist 

using the Unified Soil Classification System (USCS). A photoionization detector (PID) was used 

to screen the breathing zone during boring activities as part of personal safety requirements. 

Observations and measurements were recorded on sampling forms (Appendix B2) and in a nontreated field logbook (i.e., composition notebook). Depth interval, recovery thickness, PID 

concentrations, moisture, relative density, color (using a Munsell soil color chart), and texture 

(using the USCS) were recorded. The boring logs are provided in Appendix E.

Soil borings completed during the SI found poorly graded sands and silts as the dominant lithology 

of the unconsolidated sediments below Camp Roberts. The borings were completed at depths 

between 75 feet to 120.5 feet below ground surface (bgs). Interbedded lenses of cobbles and 

clays were also observed in the borings ranging from a few inches to approximately 6 feet in 

thickness. These observations are consistent with the understood depositional environment of the 

region.

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

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

and transported via Federal Express (FedEx) under standard chain of custody (CoC) procedures 

to the laboratory and analyzed by LC/MS/MS compliant with QSM 5.3 Table B-15, total organic 

carbon (TOC) (USEPA Method 9060A), and pH (USEPA Method 9045D) in accordance with the

SI QAPP Addendum (AECOM, 2021b).

Field duplicate samples were collected at a rate of 10% and analyzed for the same parameters 

as the accompanying samples. MS/MSDs were collected at a rate of 5% and analyzed for the 

same parameters as the accompanying samples. In instances when non-dedicated sampling 

equipment was used, such as a hand auger for the shallow soil samples, equipment rinsate blanks

were collected at a rate of 5% and analyzed for the same parameters as the soil samples. A 

temperature blank was placed in each cooler to ensure that samples were preserved at or below 

6 degrees Celsius (°C) during shipment.

Following completion of soil sampling, HSA borings were converted to permanent monitoring 

wells, as described in Section 5.3.

5.3 Permanent Well Installation and Groundwater Sampling

During the SI, four permanent monitoring wells were installed within or downgradient of potential 

source areas. The locations of the wells are shown on Figure 5-1 and Figure 5-2. 

A CME 85 HSA drill rig was used to install four 2-inch diameter monitoring wells. The monitoring 

wells were constructed using 5- or 10-feet sections of 2-inch Schedule 40 poly-vinyl chloride 

(PVC) screen with sufficient 2-inch PVC casing to reach ground surface. Filter pack was placed 

around the well screen to at least 2 feet above the top of the well screen. To prevent vertical flow 

within the boring from affecting the screened interval, a minimum 3-feet thick layer of bentonite 

chips was installed immediately above the filter sand. Then, the remaining annular space around 

the well was grouted using a grout composed of neat cement and granular bentonite. The 

bentonite grout was allowed to set for 24 hours prior to well completion in accordance with the SI 

QAPP Addendum (AECOM, 2021b). Each monitoring well was completed with a concrete well 

pad consisting of a Portland cement/sand mixture and with a flush mount cover. Well installation

details were recorded on the well construction forms (Appendix E). The screen interval of each 

of the groundwater monitoring wells is provided in Table 5-3.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-4

Development and sampling of wells was completed in accordance with the SI QAPP Addendum 

(AECOM, 2021b). The newly installed monitoring wells were developed no sooner than 24 hours 

following installation by pumping and surging using a variable speed submersible pump. The wells 

were purged at a rate determined in the field to reduce draw down during development. Water 

quality parameters (e.g., temperature, specific conductance, pH, dissolved oxygen [DO], and 

oxidation-reduction potential, [ORP]) were measured using a water quality meter and recorded 

on the field sampling form (Appendix B2). Water levels were measured to the nearest 0.01 inch 

and recorded. Samples were collected no sooner than 24 hours following development using 

HDPE HydrasleevesTM in accordance with the SI QAPP Addendum (AECOM, 2021b). Since the 

HydrasleeveTM is a PFAS-free and disposable passive sampler, this sampling method minimized 

the potential for cross contamination, negated the need for decontamination, and minimized the 

amount of purge water generated. A subsample of each groundwater sample was collected in a 

separate container, and a shaker test was completed to identify if there were any foaming. No 

foaming was noted in any of the groundwater samples.

Each sample was collected into laboratory-supplied PFAS-free HDPE bottles and labeled using 

a PFAS-free marker or pen. Samples were packaged on ice and transported via FedEx under 

standard CoC procedures to the laboratory and analyzed by LC/MS/MS compliant with QSM 5.3 

Table B-15 in accordance with the SI QAPP Addendum (AECOM, 2021b).

Field duplicate samples were collected at a rate of 10% and analyzed for the same parameters 

as the accompanying samples. MS/MSDs were collected at a rate of 5% and analyzed for the 

same parameters as the accompanying samples. One field reagent blank was collected in 

accordance with the PQAPP (AECOM, 2018a). A temperature blank was placed in each cooler to 

ensure that samples were preserved at or below 6°C during shipment.

5.4 Synoptic Water Level Measurements

A synoptic groundwater gauging event was performed on 27 May 2021. Groundwater elevation 

measurements were collected from the four new permanent monitoring wells. Water level 

measurements were taken from the northern side of the well casing. A groundwater elevation map 

is provided in Figure 2-4. Groundwater elevation data are provided in Table 5-3.

5.5 Surveying

The northern side of each well casing was surveyed by California-licensed land surveyors 

following guidelines provided in the SOPs provided in the SI QAPP Addendum (AECOM, 2021b). 

Survey data from the newly installed wells on the facility were collected on 27 May 2021 in North 

American Datum 1983 (2011) State Plane California Zone IV. The surveyed well data are provided 

in Appendix B3.

5.6 Investigation-Derived Waste

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

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

accordance with the SI QAPP Addendum (AECOM, 2021b) and with the DA Guidance for 

Addressing Releases of PFAS, Q18 (DA, 2018).

Soil IDW generated during SI activities was containerized in properly labeled 55-gallon drums. 

The IDW was stored inside a building designated by Camp Roberts Environmental Manager and 

CAARNG. ARNG will coordinate waste profiling, transportation, and disposal of the solid IDW. 

Liquid IDW generated during SI activities (i.e. purge water, development water, and 

decontamination fluids) were containerized in properly-labeled 55-gallon drums and stored inside 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-5

a building designated by CAARNG. The liquid IDW was not sampled and assumes the 

characteristics of the associated groundwater samples collected from that source location. Based 

on laboratory results, containerized liquid IDW will be managed and disposed by ARNG under a 

separate contract for Treating Liquid Investigation-Derived Material (Purge water, drilling water, 

and decontamination fluids) (EA Engineering, Science, and Technology, Inc., 2021).

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

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

activities were disposed of at a licensed solid waste landfill.

5.7 Laboratory Analytical Methods

Samples were analyzed by LC/MS/MS compliant with QSM 5.3 Table B-15 at Pace Analytical Gulf 

Coast in Baton Rouge, Louisiana, a DoD ELAP and NELAP certified laboratory. Soil samples 

were also analyzed for TOC using USEPA Method 9060A and pH by USEPA Method 9045D.

5.8 Deviations from SI QAPP Addendum

Two deviations from the SI QAPP Addendum were identified during review of the field 

documentation. 

• During the SI field work, AECOM was informed that the location of proposed AOI04-01 might 

be in conflict with a future building. As a result, the drilling location of AOI04-01 was shifted 

to a new location within 50 feet of the proposed location. 

• Due to drilling conditions during SI field work, augers were only able to be advanced 3 feet 

into the water bearing zone at AOI01-01. As a result, a 5 foot well screen was installed 

instead of a 10 foot well screen at well location AOI01-01.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-6

THIS PAGE INTENTIONALLY BLANK
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Roberts, San Miguel, California

Sample Identification

Sample

Collection 

Date/Time

Sample Depth 

(feet bgs)

LC/MS/MS compliant with QSM 5.3 Table B-15TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size (ASTM D422)

Comments

AOI01-01-SB-00-02 5/13/2021 11:10 0-2 x

AOI01-01-SB-10-11 5/13/2021 13:48 10-11 x

AOI01-01-SB-118-119 5/14/2021 14:35 118-119 x

AOI01-02-SB-00-02 5/13/2021 12:15 0-2 x

AOI01-03-SB-00-02 5/14/2021 13:00 0-2 x

AOI01-04-SB-00-02 5/13/2021 13:05 0-2 x x x

AOI02-01-SB-00-02 5/11/2021 12:15 0-2 x

AOI02-01-SB-10-11 5/11/2021 14:30 10-11 x

AOI02-01-SB-72-73 5/12/2021 10:05 72-73 x

AOI02-02-SB-00-02 5/12/2021 15:45 0-2 x x x

AOI02-03-SB-00-02 5/12/2021 16:15 0-2 x

AOI02-04-SB-00-02 5/12/2021 16:42 0-2 x

AOI02-05-SB-00-02 5/12/2021 17:01 0-2 x

AOI02-06-SB-00-02 5/12/2021 17:16 0-2 x

AOI03-01-SB-00-02 5/17/2021 15:50 0-2 x x x

AOI03-01-SB-00-02-D 5/17/2021 15:50 0-2 x Field Duplicate

AOI03-01-SB-00-02-MS 5/17/2021 15:50 0-2 x MS

AOI03-01-SB-00-02-MSD 5/17/2021 15:50 0-2 x MSD

AOI03-01-SB-10-11 5/18/2021 9:50 10-11 x

AOI03-01-SB-91-92 5/19/2021 9:30 91-92 x

AOI03-02-SB-00-02 5/17/2021 16:45 0-2 x

AOI03-03-SB-00-02 5/17/2021 17:10 0-2 x

AOI04-01-SB-00-02 5/20/2021 8:20 0-2 x

AOI04-01-SB-09-10 5/20/2021 11:15 9-10 x

AOI04-01-SB-84-85 5/21/2021 8:45 84-85 x

AOI04-02-SB-00-02 5/20/2021 16:25 0-2 x x x

AOI04-02-SB-00-02-MS 5/20/2021 16:25 0-2 x MS

AOI04-02-SB-00-02-MSD 5/20/2021 16:25 0-2 x MSD

AOI04-03-SB-00-02 5/20/2021 16:45 0-2 x

AOI04-03-SB-00-02-D 5/20/2021 16:45 0-2 x Field Duplicate

AOI05-01-SB-00-02 5/21/2021 11:02 0-2 x

AOI05-02-SB-00-02 5/21/2021 10:35 0-2 x x x

AOI06-01-SB-00-02 5/19/2021 14:43 0-2 x

AOI06-02-SB-00-02 5/19/2021 14:10 0-2 x x x

AOI06-02-SB-00-02-D 5/19/2021 14:10 0-2 x x x Field Duplicate

AOI01-01-GW 5/27/2021 10:15 115-120 x

AOI02-01-GW 5/27/2021 9:45 64-74 x

AOI02-01-GW-MS 5/27/2021 9:45 64-74 x MS

AOI02-01-GW-MSD 5/27/2021 9:45 64-74 x MSD

AOI03-01-GW 5/27/2021 9:00 91.5-101.5 x

AOI03-01-GW-D 5/27/2021 9:00 91.5-101.5 x Field Duplicate

AOI04-01-GW 5/27/2021 8:30 85-95 x

Soil Samples

Groundwater Samples

AECOM 5-7
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Roberts, San Miguel, California

Sample Identification

Sample

Collection 

Date/Time

Sample Depth 

(feet bgs)

LC/MS/MS compliant with QSM 5.3 Table B-15TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size (ASTM D422)

Comments

CR-ERB-01 5/18/2021 8:35 x x Stainless Steel Bowl

CR-ERB-02 5/18/2021 9:15 x x Hand Auger

CR-ERB-03 5/18/2021 10:00 x x Split Spoon (core)

CR-ERB-04 5/21/2021 11:25 x Lost During Transportation

CR-ERB-05 5/26/2021 7:30 x x Poly Rope

CR-FRB-01 5/18/2021 8:30 x x

CR-PW-01 3/18/2021 12:30 x x Decon Source

Notes:

ASTM = American Society for Testing and Materials

bgs = below ground surface

ERB = equipment rinsate blank

FD = field duplicate

FRB = field reagent blank

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

QSM = Quality Systems Manual

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

Quality Control Samples

AECOM 5-8
Table 5-2

Soil Boring Depths

Site Inspection Report, Camp Roberts, California

Area of 

Interest

Boring 

Location

Soil Boring 

Depth 

(feet bgs)

AOI01-02 2AOI01-02 2AOI01-03 2AOI01-04 2AOI02-02 2AOI02-03 2AOI02-04 2AOI02-05 2AOI02-06 2AOI03-02 2AOI03-03 2AOI04-02 2AOI04-03 2AOI05-01 2AOI05-02 2AOI06-01 2AOI06-02 2

Notes:bgs = below ground surface

1. Boring locations presented on this table are hand augered surface soil locations.

612345

AECOM 
Table 5-3

Permanent Monitoring Well Screen Intervals and Groundwater Elevations

Site Inspection Report, Camp Roberts, California

Area of 

Interest

Boring 

Location

Soil Boring 

Depth 

(feet bgs)

Permanent Well 

Screen Interval 

(feet bgs)

Top of Casing 

Elevation 

(feet NAVD88)

Ground Surface 

Elevation 

(feet NAVD88)

Depth to 

Water

(feet btoc)

Dept

Wa

(feet 

1 AOI01-01 119 115-120 633.68 634.19 94.40 94

2 AOI02-01 73 64-74 633.48 633.92 62.10 623 AOI03-01 92 91.5-101.5 638.48 639.01 86.95 874 AOI04-01 85 85-95 638.44 638.97 75.75 76

Notes:bgs = below ground surfacebtoc = below top of casingNAVD88 = North American Vertical Datum 1988

AECOM 
!?

"S

"S

"S

!?

"S

"S

"S

"S "S

AOI 1

AOI 2

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI02-06

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SL

8/2/2022

8/2/2022

PROJECT Site Inspection at Camp Roberts, CA

1:2,400

8/2/2022 ­ Figure 5-1 PM CM 8/2/2022

12420 Milestone Center Drive

Germantown, MD 20876

Site Inspection Sample Locations - 

AOI 1, AOI 2

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

and the GIS User Community

0 100 200 400

Feet

Legend

!? Soil Boring/Permanent

Monitoring Well

"S Surface Soil Sample

Area of Interest

Facility Boundary

Localized Inferred

Groundwater Flow

Direction

AECOM 5-11
!?

"S

"S

!?

"S"S

"S

"S

AOI 4

AOI 3

AOI 5

AOI03-01

AOI03-02

AOI03-03

AOI04-01

AOI04-02

AOI04-03

AOI05-01

AOI05-02

Salinas River

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SL

8/22/2022

8/22/2022

PROJECT Site Inspection at Camp Roberts, CA

1:10,800

8/22/2022 ­ Figure 5-2 PM CM 8/22/2022

12420 Milestone Center Drive

Germantown, MD 20876

Site Inspection Sample Locations - 

AOI 3, AOI 4, AOI 5

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

and the GIS User Community

0 450 900 1,800

Feet

Legend

!? Soil Boring/Permanent

Monitoring Well

"S Surface Soil Sample

Area of Interest

Facility Boundary

Water Body

Wetland

River/Stream

Inferred Groundwater

Flow Direction

AECOM 5-12
"S

"S

AOI 6

AOI06-01

AOI06-02

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SL

8/2/2022

8/2/2022

PROJECT Site Inspection at Camp Roberts, CA

1:2,400

8/2/2022 ­ Figure 5-3 PM CM 8/2/2022

12420 Milestone Center Drive

Germantown, MD 20876

Site Inspection Sample Locations - 

AOI 6

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

and the GIS User Community

0 100 200 400

Feet

Legend

"S Surface Soil Sample

Area of Interest

Facility Boundary

Wetland

River/Stream

Inferred Groundwater

Flow Direction

AECOM 5-13
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 5-14

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 6-1

6. Site Inspection Results 

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

presented in Section 6.1. A discussion of the results for each AOI is provided in Section 6.3

through Section 6.8. Table 6-2 through Table 6-5 present results in soil or groundwater for the 

relevant compounds. Tables that contain all results are provided in Appendix F, and the 

laboratory reports are provided in Appendix G. 

6.1 Screening Levels 

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

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

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

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

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

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

6-1 below.

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

Analyteb 

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ 

Commercial 

Composite 

Worker

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater)

(ng/L)a

PFOA 19 250 6 

PFOS 13 160 4

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6 

Notes:

bgs = below ground surface; μg/kg = micrograms per kilogram; ng/L = nanograms per liter

a.) Assistant Secretary of Defense, 2022. Risk Based Screening Levels in Groundwater and Soil using United States Environmental Protection 

Agency’s (USEPA’s) Regional Screening Level Calculator. Hazard Quotient (HQ) = 0.1. 6 July 2022. 

b.) Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA (commonly referred to as GenX) was not included 

as an analyte at the time of this SI. Based on the CSM developed during the PA and revised based on SI findings, the presence of HFPODA is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC AFFF and based on its history including 

distribution limitations that restricted use of GenX, it is generally not a component of other products the military used. In addition, it is 

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

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

SLs for groundwater are based on direct ingestion. The SLs for soil are based on incidental 

ingestion and are applied to the depth intervals reasonably anticipated to be encountered by the 

receptors identified at the facility: the residential scenario is applied to surface soil results (0 to 2 

feet bgs) and the industrial/commercial worker scenario is applied to shallow subsurface soil 

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

because 15 feet is the anticipated limit of construction activities. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 6-2

6.2 Soil Physicochemical Analyses

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

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

of the TOC and pH sampling. 

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

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

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

effects, electrostatic interactions, and interfacial behaviors. At relevant environmental pH values, 

certain PFAS are present as organic anions and are therefore relatively mobile in groundwater 

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

soil or sediment (Higgins and Luthy 2006; Guelfo and Higgins, 2013). When sufficient organic 

carbon is present, organic carbon normalized distribution coefficients (Koc values) can help in 

evaluating transport potential, though other geochemical factors (for example, pH and presence 

of polyvalent cations) may also affect PFAS sorption to solid phases (ITRC, 2018).

6.3 AOI 1

This section presents the analytical results for soil and groundwater in comparison to SLs for 

AOI 1: East Garrison Old Fire Station and Army Airfield AFFF Storage. The soil and groundwater 

results are summarized on Table 6-2 through Table 6-5. Soil and groundwater results are 

presented on Figure 6-1 through Figure 6-9.

6.3.1 AOI 1 Soil Analytical Results

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

AOI01-04. Soil was also sampled from shallow subsurface soil (10 to 11 feet bgs) and deep 

subsurface soil (118 to 119 feet bgs) from boring location AOI01-01. Table 6-2 through Table 6-4

summarize the soil results. Figure 6-1 through Figure 6-7 present the ranges of detections in 

soil.

PFOS was detected above the SL of 13 micrograms per kilogram (μg/kg) in surface soil at all four

locations, with concentrations ranging from 19.6 J μg/kg to 443 J μg/kg. PFOA, PFHxS, PFNA, 

and PFBS were detected at concentrations below their respective SLs in surface soil at all four 

locations. The maximum concentrations were PFOA at 16.7 J μg/kg; PFHxS at 60.2 J μg/kg; 

PFNA at 3.04 J μg/kg; and PFBS at 8.59 J μg/kg. PFOA, PFOS, PFHxS, PFNA, and PFBS were 

not detected in shallow subsurface soil or deep subsurface soil. 

6.3.2 AOI 1 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring well location AOI01-01. Table 6-5 

summarizes the groundwater results. Figure 6-8 and Figure 6-9 present the ranges of detections 

in groundwater. PFOS and PFBS were detected at concentrations below their respective SLs in 

groundwater, with concentrations of 1.50 J ng/L and 1.30 J ng/L, respectively. PFOA, PFHxS, and 

PFNA were not detected in groundwater. 

6.3.3 AOI 1 Conclusions

Based on the results of the SI, PFOS was detected in soil at concentrations above the SL. No 

compounds exceeded the SLs in groundwater. Based on the exceedances of the SLs in soil, 

further evaluation at AOI 1 is warranted. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 6-3

6.4 AOI 2

This section presents the analytical results for soil and groundwater in comparison to SLs for 

AOI 2: East Garrison Old FTA. The results in soil and groundwater are summarized on Table 6-2

through Table 6-5. Soil and groundwater results are presented on Figure 6-1 through Figure 6-

9.

6.4.1 AOI 2 Soil Analytical Results

Soil was sampled from surface soil (0 to 2 feet bgs) at boring locations AOI02-01 through AOI02-

06. Soil was also sampled from shallow subsurface soil (10 to 11 feet bgs) and deep subsurface 

soil (72 to 73 feet bgs) from boring location AOI02-01. Table 6-2 through Table 6-4 summarize 

the soil results. Figure 6-1 through Figure 6-7 present the ranges of detections in soil.

PFOS was detected in soil at concentrations above its respective SL in surface soil. PFOS was 

detected above the SL of 13 μg/kg at locations AOI02-03 and AOI02-04, with concentrations of 

103 J μg/kg and 584 J μg/kg, respectively. PFOA, PFHxS, PFNA, and PFBS were detected at 

concentrations below their respective SLs in surface soil with the following maximum 

concentrations:

• PFOA was detected at locations AOI02-02 through AOI02-06, with a maximum 

concentration of 0.429 J μg/kg. 

• PFHxS was detected at all six locations, a maximum concentration of 1.52 J μg/kg. 

• PFNA was detected at four of the six locations, with a maximum concentration of 1.13 

J μg/kg. 

• PFBS was detected at locations AOI02-03 and AOI02-04, with a maximum 

concentration of 0.090 J μg/kg. 

PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in shallow subsurface soil or deep 

subsurface soil.

6.4.2 AOI 2 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring well location AOI02-01. Table 6-5 

summarizes the groundwater results. Figure 6-8 and Figure 6-9 present the ranges of detections 

in groundwater.

PFOS and PFHxS were detected at concentrations above their respective SLs in groundwater. 

PFOS was detected above the SL of 4 ng/L, with a concentration of 15.7 J ng/L. PFHxS was 

detected above the SL of 39 ng/L, with a concentration of 85.6 J ng/L. PFOA and PFBS were 

detected at concentrations below their respective SLs in groundwater, with concentrations of 3.29 

J ng/L and 11.4 J ng/L, respectively. PFNA was not detected in groundwater. 

6.4.3 AOI 2 Conclusions

Based on the results of the SI, PFOS was detected in soil at concentrations above the SL. PFOS 

and PFHxS were detected in groundwater at concentrations above their respective SLs. Based 

on the exceedances of the SLs in soil and groundwater, further evaluation at AOI 2 is warranted. 

6.5 AOI 3

This section presents the analytical results for soil and groundwater in comparison to SLs for 

AOI 3: Main Garrison FTA 2 and Building 7020. The results in soil and groundwater are presented 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 6-4

in Table 6-2 through Table 6-5. Soil and groundwater results are presented on Figure 6-1 through 

Figure 6-9.

6.5.1 AOI 3 Soil Analytical Results

Soil was sampled from surface soil (0 to 2 feet bgs) at boring locations AOI03-01 through AOI03-

03. Soil was also sampled from shallow subsurface soil (10 to 11 feet bgs) and deep subsurface 

soil (91 to 92 feet bgs) from AOI03-01. Table 6-2 through Table 6-4 summarize the soil results.

Figure 6-1 through Figure 6-7 present the ranges of detections in soil. 

PFOS was detected above the SL of 13 μg/kg in surface soil at AOI03-03 with a concentration of 

44.7 J μg/kg. PFOA PFHxS, PFNA, and PFBS were detected at concentrations below their 

respective SLs in surface soil with the following maximum concentrations:

• PFOA and PFHxS were detected at all three locations, with maximum concentrations

of 5.80 J μg/kg and 40.1 J μg/kg, respectively. 

• PFNA was detected at locations AOI03-01 and AOI03-03, with a maximum 

concentration of 0.065 J μg/kg in the field duplicate sample (AOI03-01-SB-00-02D). 

• PFBS was detected at locations AOI03-01 and AOI03-03, with a maximum 

concentration of 1.30 J μg/kg.

PFOA, PFOS, PFHxS, and PFBS were detected at concentrations below their respective SLs in 

shallow subsurface soil at location AOI03-01 with the following concentrations: PFOA at 3.60 J 

μg/kg; PFOS at 0.179 J μg/kg; PFHxS at 12.5 J μg/kg; PFBS at 0.273 J μg/kg. PFNA was not 

detected in shallow subsurface soil. PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected 

in deep subsurface soil. 

6.5.2 AOI 3 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring well location AOI03-01. Table 6-5 

summarizes the groundwater results. Figure 6-8 and Figure 6-9 present the ranges of detections 

in groundwater.

PFOA and PFHxS were detected at concentrations above their respective SLs in groundwater. 

PFOA was detected above the SL of 4 ng/L with a maximum concentration of 8.09 J ng/L. PFHxS 

was detected above the SL of 39 ng/L, with a maximum concentration of 79.5 J ng/L. PFOS and 

PFBS were detected below the respective SLs in groundwater, with concentrations of 3.50 J ng/L 

and 9.70 J ng/L, respectively. PFNA was not detected in groundwater. 

6.5.3 AOI 3 Conclusions

Based on the results of the SI, PFOS was detected in soil above the SL. PFOA and PFHxS were

detected in groundwater at concentrations above their respective SLs. Based on the exceedances 

of the SLs in soil and groundwater, further evaluation at AOI 3 is warranted.

6.6 AOI 4

This section presents the analytical results for soil and groundwater in comparison to SLs for 

AOI 4: CR FD Fire Station and Shipping Container. The results in soil and groundwater are 

presented in Table 6-2 through Table 6-5. Soil and groundwater results are presented on Figure 

6-1 through Figure 6-9.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 6-5

6.6.1 AOI 4 Soil Analytical Results

Soil was sampled from surface soil (0 to 2 feet bgs) at boring locations AOI04-01, AOI04-02, and 

AOI04-03. Soil was also sampled from the shallow subsurface (9 to 10 feet bgs) and deep 

subsurface (84 to 85 feet bgs) from boring location AOI04-01. Table 6-2 through Table 6-4

summarize the soil results. Figure 6-1 through Figure 6-7 present the ranges of detections in 

soil.

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected below their respective SLs in surface soil

at all three locations, with the following maximum concentrations: PFOA at 1.38 μg/kg; PFOS at

7.60 J μg/kg; PFHxS at 2.44 μg/kg; PFNA at 0.728 J μg/kg; and PFBS at 0.080 J μg/kg. 

PFOS, PFHxS, and PFNA were detected below their respective SLs in shallow subsurface soil at 

location AOI04-01, with concentrations of 0.238 J μg/kg, 0.086 J μg/kg, and 0.031 J μg/kg, 

respectively. PFOA and PFBS were not detected in shallow subsurface soil. PFOA, PFOS, 

PFHxs, PFNA, and PFBS were not detected in deep subsurface soil. 

6.6.2 AOI 4 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring well locations AOI04-01. Table 6-5 

summarizes the groundwater results. Figure 6-8 and Figure 6-9 present the ranges of detections 

in groundwater.

PFOS was detected below the SL of 4 ng/L, with a concentration of 1.08 J ng/L. PFOA, PFHxS, 

PFNA, and PFBS were not detected in groundwater. 

6.6.3 AOI 4 Conclusions

Based on the results of the SI, PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil at 

concentrations below their respective SLs. PFOS was detected in groundwater at a concentration 

below the SL. No other compounds were detected in groundwater. Therefore, further evaluation 

is not warranted at AOI 4.

6.7 AOI 5

This section presents the analytical results for soil in comparison to SLs for AOI 5: CR FD Building 

3000 and Main Garrison Fuel Station. Table 6-2 summarizes the soil results. Figure 6-1 through 

Figure 6-7 present the ranges of detections in soil.

6.7.1 AOI 5 Soil Analytical Results

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI05-01 and AOI05-

02. PFOS was detected above the SL of 13 μg/kg in surface soil at AOI05-02, with a concentration 

of 49.3 μg/kg. PFOA, PFHxS, PFNA, and PFBS were detected at concentrations below their 

respective SLs in surface soil. PFOA and PFBS were detected at location AOI05-02, with 

concentrations of 0.840 J μg/kg and 0.110 J μg/kg, respectively. PFHxS and PFNA were detected 

at both locations, with maximum concentrations of 4.19 μg/kg and 0.121 J μg/kg, respectively. 

6.7.2 AOI 5 Conclusions

Based on the results of the SI, PFOS was detected in soil at a concentration above the SL. Based 

on the exceedance of the SL in soil, further evaluation at AOI 5 is warranted.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 6-6

6.8 AOI 6 

This section presents the analytical results for soil in comparison to SLs for AOI 6: Hangar Building 

17002 and NPS Airfield Shed AFFF Storage. Table 6-2 summarizes the soil results. Figure 6-4

and Figure 6-7 present the ranges of detections in soil. 

6.8.1 AOI 6 Soil Analytical Results

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI06-01 and AOI06-

02. PFOS, PFHxS, and PFNA were detected at concentrations below their respective SLs in

surface soil. PFOS was detected at both locations with a maximum concentration of 0.109 J μg/kg.

PFHxS and PFNA were detected at location AOI06-02, with concentrations of 0.049 J μg/kg and

0.036 J μg/kg, respectively.

6.8.2 AOI 6 Conclusions 

Based on the results of the SI, PFOS, PFHxS, and PFNA were detected in soil at concentrations 

below their respective SLs. Therefore, further evaluation is not warranted at AOI 6. 
Table 6-2

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil

Site Inspection Report, Camp Roberts

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS 1900 8.59 J 0.127 J 0.299 J 0.045 J ND UJ ND UJ 0.090 J 0.030 J ND UJ ND UJ

PFHxS 130 60.2 J 4.02 J 7.13 J 2.28 J 0.033 J 0.340 J 1.52 J 1.04 J 0.791 J 0.744 J

PFNA 19 1.32 J 2.65 J 3.04 J 0.154 J ND UJ 0.129 J 1.13 J 0.082 J ND UJ 0.030 J

PFOA 19 16.7 J 3.21 J 3.53 J 3.78 J ND UJ 0.126 J 0.429 J 0.424 J 0.188 J 0.260 J

PFOS 13 443 J 173 J 94.1 J 19.6 J ND UJ 2.75 J 103 J 584 J 1.99 J 9.93 J

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

HQ hazard quotient

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

OSD Office of the Secretary of Defense

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

USEPA United States Environmental Protection Agency

μg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using 

USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI02-06-SB-00-02

05/12/2021

0-2 ft

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI02-04-SB-00-02

05/12/2021

0-2 ft

AOI02-05-SB-00-02

05/12/2021

0-2 ft

AOI02-02-SB-00-02

0-2 ft

AOI02-01-SB-00-02

05/11/2021

0-2 ft

AOI02

05/12/2021

0-2 ft

AOI02-03-SB-00-02

05/12/2021

0-2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-00-02

05/13/2021

0-2 ft

AOI01

AOI01-02-SB-00-02

05/13/2021

0-2 ft

AOI01-03-SB-00-02

05/14/2021

0-2 ft

AOI01-04-SB-00-02

05/13/2021

AECOM 6-7
Table 6-2

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil

Site Inspection Report, Camp Roberts

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS 1900 0.054 J 0.063 J ND UJ 1.30 J 0.029 J 0.080 J 0.056 J 0.062 J ND U 0.110 J

PFHxS 130 4.27 J 5.03 J 0.306 J 40.1 J 0.480 J 1.40 2.44 2.21 0.060 J 4.19

PFNA 19 0.046 J 0.065 J ND UJ 0.053 J 0.728 J 0.428 J 0.065 J 0.084 J 0.044 J 0.121 J

PFOA 19 0.224 J 0.276 J 0.155 J 5.80 J 1.38 0.651 J 0.430 J 0.392 J ND U 0.840 J

PFOS 13 5.17 J 5.94 J 0.088 J 44.7 J 5.45 7.60 J 2.25 2.74 1.18 49.3

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

HQ hazard quotient

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

OSD Office of the Secretary of Defense

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

USEPA United States Environmental Protection Agency

μg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using 

USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI05-02-SB-00-02

05/21/2021

0-2 ft

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI04-03-SB-00-02D

05/20/2021

0-2 ft

AOI05-01-SB-00-02

05/21/2021

0-2 ft

AOI04-02-SB-00-02

AOI04

05/20/2021

0-2 ft

AOI04-03-SB-00-02

05/20/2021

0-2 ft

05/17/2021

0-2 ft

AOI04-01-SB-00-02

05/20/2021

0-2 ft

Area of Interest AOI05

Sample ID

Sample Date

Depth

AOI03-01-SB-00-02

05/17/2021

0-2 ft

AOI03

AOI03-01-SB-00-02D

05/17/2021

0-2 ft

AOI03-02-SB-00-02

05/17/2021

0-2 ft

AOI03-03-SB-00-02

AECOM 6-8
Table 6-2

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil

Site Inspection Report, Camp Roberts

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual

PFBS 1900 ND U ND U ND U

PFHxS 130 ND U 0.049 J ND U

PFNA 19 ND U 0.036 J ND UJ

PFOA 19 ND U ND U ND U

PFOS 13 0.073 J 0.109 J ND U

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

HQ hazard quotient

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

OSD Office of the Secretary of Defense

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

USEPA United States Environmental Protection Agency

μg/kg micrograms per kilogram

05/19/2021

0-2 ft

AOI06

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using 

USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI06-02-SB-00-02

05/19/2021

0-2 ft

AOI06-02-SB-00-02D

05/19/2021

0-2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI06-01-SB-00-02

AECOM 6-9
Table 6-3

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Shallow Subsurface Soil

Site Inspection Report, Camp Roberts

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual

PFBS 25000 ND UJ ND UJ 0.273 J ND UPFHxS 1600 ND UJ ND UJ 12.5 J 0.086 JPFNA 250 ND UJ ND UJ ND UJ 0.031 JPFOA 250 ND UJ ND UJ 3.60 J ND UPFOS 160 ND UJ ND UJ 0.179 J 0.238 J

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of InterestU = The analyte was not detected at a level greater than or equal to the adjusted DL DL detection limit

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. ft feet

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI04

AOI04-01-SB-09-10

05/20/2021

9-10 ft

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI02

AOI02-01-SB-10-11

05/11/2021

10-11 ft

AOI03

AOI03-01-SB-10-11

05/18/2021

10-11 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI01

AOI01-01-SB-10-11

05/13/2021

10-11 ft

AECOM 
Table 6-4

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Deep Subsurface Soil

Site Inspection Report, Camp Roberts

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual Result Qual

PFBS ND UJ ND UJ ND U ND UPFHxS ND UJ ND UJ ND U ND UPFNA ND UJ ND UJ ND U ND UPFOA ND UJ ND UJ ND U ND UPFOS ND UJ ND UJ ND U ND U

Interpreted Qualifiers Chemical AbbreviationsU = The analyte was not detected at a level greater than or equal to the adjusted DL PFBS perfluorobutanesulfonic acidUJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acidAcronyms and Abbreviations

AOI Area of InterestDL detection limitft feetID identificationLCMSMS liquid chromatography with tandem mass LOD limit of detectionND analyte not detected above the LODQSM Quality Systems ManualQual interpreted qualifierSB soil boringμg/kg micrograms per kilogram

05/12/2021

72-73 ft

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI03

AOI03-01-SB-91-92

05/19/2021

91-92 ft

AOI04

AOI04-01-SB-84-85

05/21/2021

84-85 ft

AOI01

AOI01-01-SB-118-119

05/14/2021

118-119 ft

AOI02

AOI02-01-SB-72-73

AECOM 
Table 6-5

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Groundwater

Site Inspection Report, Camp Roberts

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS 601 1.30 J 11.4 J 9.70 J 8.82 J ND UJPFHxS 39 ND UJ 85.6 J 79.5 J 74.5 J ND UJPFNA 6 ND UJ ND UJ ND UJ ND UJ ND UJPFOA 6 ND UJ 3.29 J 8.09 J 7.54 J ND UJPFOS 4 1.50 J 15.7 J 3.50 J 3.38 J 1.08 J

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of InterestUJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. D duplicate

DL detection limitGW groundwaterHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protectiong/l nanogram per liter

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI03-01-GWD

05/27/2021

AOI04

AOI04-01-GW

05/27/2021

AOI02

AOI02-01-GW

05/27/2021

AOI03-01-GW

05/27/2021

Area of Interest

Sample ID

Sample Date

AOI01

AOI01-01-GW

05/27/2021

AOI03

AECOM 
AOI01-01

AOI01-02

AOI01-03 AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI02-06

AOI03-01

AOI03-02

AOI03-03

AOI04-01 AOI04-02

AOI04-03

AOI05-01

AOI05-02

AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 700 1,400 2,800

Feet

Figure 6-1

PFOA Detections in Soil - AOI 1 thru AOI 5

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/11/2022

8/11/2022

8/11/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:16,800

Legend

Facility Boundary

Shallow Intermediate Deep

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-13
AOI05-02

AOI05-01

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI02-06

AOI03-01

AOI03-02

AOI03-03

AOI04-01 AOI04-02

AOI04-03

AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 700 1,400 2,800

Feet

Figure 6-2

PFOS Detections in Soil - AOI 1 thru AOI 5

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/11/2022

8/11/2022

8/11/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:16,800

Legend

Facility Boundary

Shallow Intermediate Deep

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PROJECT

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

AECOM 6-14
AOI05-02

AOI05-01

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI02-06

AOI03-01

AOI03-02

AOI03-03

AOI04-01

AOI04-02

AOI04-03

AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 700 1,400 2,800

Feet

Figure 6-3

PFBS Detections in Soil - AOI 1 thru AOI 5

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/11/2022

8/11/2022

8/11/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:16,800

Legend

Facility Boundary

Shallow Intermediate Deep

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

AECOM 6-15
AOI06-01

AOI06-02

Figure 6-4

PFOA, PFOS, and PFBS Detection in Soil - AOI 6

12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/16/2022

8/16/2022

8/16/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/16/2022

Legend

Facility Boundary

0 125 250 500

1:3,000

Feet ­

AOI06-01

AOI06-02

AOI06-01

AOI06-02

PFOA - Shallow PFOS - Shallow PFBS - Shallow

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

AECOM 6-16
AOI05-02

AOI05-01

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI02-06

AOI03-01

AOI03-02

AOI03-03

AOI04-01

AOI04-02

AOI04-03

AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 700 1,400 2,800

Feet

Figure 6-5

PFHxS Detections in Soil - AOI 1 thru AOI 5

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/11/2022

8/11/2022

8/11/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:16,800

Legend

Facility Boundary

Shallow Intermediate Deep

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

AECOM 6-17
AOI05-02

AOI05-01

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI02-06

AOI03-01

AOI03-02

AOI03-03

AOI04-01

AOI04-02

AOI04-03

AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 700 1,400 2,800

Feet

Figure 6-6

PFNA Detections in Soil - AOI 1 thru AOI 5

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/11/2022

8/11/2022

8/11/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:16,800

Legend

Facility Boundary

Shallow Intermediate Deep

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-18
AOI06-01

AOI06-02

Figure 6-7

PFHxS and PFNA Detection in Soil - AOI 6

12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/16/2022

8/16/2022

8/16/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/16/2022

Legend

Facility Boundary

0 125 250 500

1:3,000

Feet ­

AOI06-01

AOI06-02

PFHxS - Shallow PFNA - Shallow

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

AECOM 6-19
AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 650 1,300 2,600

Feet

Figure 6-8

PFOA, PFOS, and PFBS Detections 

in Groundwater

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

10/5/2022

10/5/2022

10/5/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

10/5/2022

1:15,369

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

PFOS Results (ng/L)

ND

>ND - 4

>4 - 40

>40 - 70

>70

PFBS Results (ng/L)

ND

>ND - 100

>100 - 601

>601 - 2,000

>2,000

Legend

Surface Water Flow Direction

Localized Inferred Groundwater Flow Direction

PFOA PFOS PFBS

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

AECOM 6-20
AOI01-01

AOI02-01

AOI03-01

AOI04-01

AOI01-01

AOI02-01

AOI03-01

AOI04-01

0 650 1,300 2,600

Feet

Figure 6-9

PFHxS and PFNA Detections 

in Groundwater

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

Site Inspection at Camp Roberts, CA

8/11/2022

8/11/2022

8/11/2022

MS

SL

CM

GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:15,369

PFHxS (ng/L)

ND

>ND - 39

>39 - 100

>100 - 1,000

>1,000

PFNA Results (ng/L)

ND

>ND - 6

>6 - 100

>100 - 1,000

>1,000

Legend

Surface Water Flow Direction

Localized Inferred Groundwater Flow Direction

PFHxS PFNA

PROJECT

Exceedances of the OSD SL are depicted with a yellow halo.

AECOM 6-21
THIS PAGE INTENTIONALLY BLANK

6-22
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 7-1

7. Exposure Pathways

The CSMs for each AOI, revised based on the SI findings, are presented on Figure 7-1 through 

Figure 7-6. Please note that while the CSM discussion assists in determining if a receptor may 

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

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

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

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

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

potentially complete when the following conditions are present:

1. Contaminant source;

2. Environmental fate and transport;

3. Exposure point;

4. Exposure route; and

5. Potentially exposed populations.

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

circle symbol to represent an incomplete exposure pathway. Areas with an incomplete pathway 

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

relevant compounds are detected, in which case the CSM figure uses a half-filled circle symbol to 

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

used to indicate when a potentially complete exposure pathway has detections of relevant 

compounds above the SLs. Areas with an identified potentially complete pathway that have 

detections of the relevant compounds above the SLs may warrant further investigation. Although 

the CSMs indicate whether potentially complete exposure pathways may exist, the 

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

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

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

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

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

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

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

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

workers, trespassers, residents outside the facility boundary, and recreational users outside of 

the facility boundary. 

7.1 Soil Exposure Pathway

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

between the source and potential receptors at AOI 1, AOI 2, AOI 3, AOI 4, AOI 5, and AOI 6 based 

on the aforementioned criteria. 

7.1.1 AOI 1 

AFFF may have been released at AOI 1 during fire training activities at the East Garrison Old Fire 

Station or via incidental spills related to the Army Airfield AFFF Storage. 

PFOS was detected in surface soil at concentrations above the SL at AOI 1. PFOA, PFHxS, 

PFNA, and PFBS were detected at concentrations below their respective SLs in surface soil at 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 7-2

AOI 1. Site workers and construction workers could contact constituents in surface soil via 

incidental ingestion and inhalation of dust. Therefore, the surface soil exposure pathway for site 

workers and future construction workers are potentially complete. PFOA, PFOS, PFHxS, PFNA, 

and PFBS were not detected in subsurface soil at AOI 1. Therefore, the subsurface soil exposure 

pathways are incomplete. The CSM for AOI 1 is presented on Figure 7-1. 

7.1.2 AOI 2 

As early as 1976, AFFF may have been released at AOI 2 during fire training activities at the East 

Garrison Old FTA. PFOS was detected in surface soil at concentrations above the SL at AOI 2. 

PFOA, PFHxS, PFNA, and PFBS were detected at concentrations below their respective SLs in 

surface soil at AOI 2. Site workers and construction workers could contact constituents in surface 

soil via incidental ingestion and inhalation of dust. Therefore, the surface soil exposure pathway 

for site workers and future construction workers are potentially complete. PFOA, PFOS, PFHxS, 

PFNA, and PFBS were not detected in subsurface soil at AOI 2. Therefore, the subsurface soil 

exposure pathways are incomplete. The CSM for AOI 2 is presented on Figure 7-2. 

7.1.3 AOI 3 

As early as 1971, AFFF may have been released at AOI 3 during fire training activities at the Main 

Garrison FTA 2 and in the vicinity of CR FD Fire Station Building 7020. PFOS was detected in 

surface soil at concentrations above the SL at AOI 3. PFOA, PFHxS, PFNA, and PFBS were 

detected at concentrations below their respective SLs in surface soil at AOI 3. Site workers and 

construction workers could contact constituents in surface soil via incidental ingestion and 

inhalation of dust. Therefore, the surface soil exposure pathway for site workers and future 

construction workers are potentially complete. PFOA, PFOS, PFHxS, and PFBS were detected 

in subsurface soil at AOI 3 at concentrations below their respective SLs. Future construction 

workers could contact constituents in subsurface soil via incidental ingestion, and therefore, the 

subsurface soil exposure pathway is potentially complete. Therefore, the subsurface soil 

exposure pathways are incomplete. The CSM for AOI 3 is presented on Figure 7-3. 

7.1.4 AOI 4 

AFFF may have been released at AOI 4 via incidental spills due to AFFF storage at the Current

CR FD Fire Station and Shipping Container. PFOA, PFOS, PFHxS, PFNA, and PFBS were 

detected at concentrations below their respective SLs in surface soil at AOI 4. Site workers and 

construction workers could contact constituents in surface soil via incidental ingestion and 

inhalation of dust. Therefore, the surface soil exposure pathway for site workers and construction 

workers are potentially complete. PFOS, PFHxS, and PFNA were detected in subsurface soil at 

AOI 4 at concentrations below their respective SLs. Future construction workers could contact 

constituents in subsurface soil via incidental ingestion, and therefore, the subsurface soil 

exposure pathway is potentially complete. Therefore, the subsurface soil exposure pathways are 

incomplete. The CSM for AOI 4 is presented on Figure 7-4. 

7.1.5 AOI 5 

AFFF may have been released at AOI 5 via incidental spills due to AFFF storage at the CR FD 

Building 3000 Warehouse and Main Garrison Fueling Point. PFOS was detected in surface soil 

at concentrations above the SL at AOI 5. PFOA, PFHxS, PFNA, and PFBS were detected at 

concentrations below their respective SLs in surface soil at AOI 5. Site workers and construction 

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

Therefore, the surface soil exposure pathway for site workers and construction workers are 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 7-3

potentially complete. Subsurface soil was not sampled at AOI 5, therefore; this exposure pathway 

was not evaluated. The CSM for AOI 5 is presented on Figure 7-5. 

7.1.6 AOI 6 

AFFF may have been released at AOI 6 via incidental spills due to AFFF storage at the TUAS 

Hangar Building 17002 Warehouse and NPS Airfield Shed. PFOS, PFHxS, and PFNA were 

detected in surface soil at concentrations below their respective SLs at AOI 6. Site workers and 

construction workers could contact constituents in surface soil via incidental ingestion and 

inhalation of dust. Therefore, the surface soil exposure pathway for site workers and construction 

workers are potentially complete. Subsurface soil was not sampled at AOI 5, therefore; this 

exposure pathway was not evaluated. The CSM for AOI 6 is presented on Figure 7-6. 

7.2 Groundwater Exposure Pathway

The SI results in groundwater were used to determine whether a potentially complete pathway 

exists between the source and potential receptors based on the aforementioned criteria.

7.2.1 AOI 1 

PFOS and PFBS were detected below their respective SLs in groundwater samples collected at 

AOI 1. The ingestion exposure pathway for future construction workers is considered incomplete, 

because groundwater is deeper than 15 feet bgs and construction worker contact is unlikely. 

Drinking water is supplied by potable wells in the Main Garrison, and two active potable water 

wells are located downgradient of the East Garrison. Based on an assumed northwestern 

groundwater flow direction, the AOIs are upgradient of potable wells. Because the facility drinking 

water supply wells may be impacted by potential releases at the AOIs, the exposure pathway for 

groundwater to onsite receptors is potentially complete. However, in March 2017, groundwater 

from the majority of Camp Roberts’ well network was analyzed for a subset of 18 PFAS

compounds. PFOA, PFOS, PFHxS, PFNA and PFBS were not detected in any sample (AECOM, 

2019). No off-facility potable wells are located within a four-mile radius of Camp Roberts (Figure 

2-3). The CSM for AOI 1 is presented on Figure 7-1.

7.2.2 AOI 2 

PFOS and PFHxS were detected above their respective SLs in groundwater samples collected 

at AOI 2. PFOA and PFBS were detected in groundwater at concentrations below their respective 

SLs. The ingestion exposure pathway for future construction workers is considered incomplete, 

because groundwater is deeper than 15 feet bgs and construction worker contact is unlikely. 

Because the facility drinking water supply wells may be impacted by potential releases at the 

AOIs, the exposure pathway for groundwater to onsite receptors is potentially complete. However, 

as discussed in Section 7.2.1, PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in the 

Camp Roberts potable well network during a March 2017 PFAS sampling event. The CSM for 

AOI 2 is presented on Figure 7-2. 

7.2.3 AOI 3 

PFOA and PFHxS were detected above their respective SLs in groundwater samples collected at 

AOI 2. PFOS and PFBS were detected in groundwater at concentrations below their respective 

SLs. The ingestion exposure pathway for future construction workers is considered incomplete, 

because groundwater is deeper than 15 feet bgs and construction worker contact is unlikely. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 7-4

The nearest drinking water wells are to the west of AOI 3, and because groundwater is assumed

to flow to the northwest, the supply wells are potentially downgradient of AOI 3. Because the 

drinking water supply wells may be impacted by potential releases at the AOIs, the exposure 

pathway for groundwater to onsite receptors is potentially complete. However, as discussed in 

Section 7.2.1, PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in the Camp Roberts 

potable well network during a March 2017 PFAS sampling event. The CSM for AOI 3 is presented 

on Figure 7-3. 

7.2.4 AOI 4 

PFOS was detected below the respective SL in the groundwater sample collected at AOI 4. The 

ingestion exposure pathway for future construction workers is considered incomplete, because 

groundwater is deeper than 15 feet bgs and construction worker contact is unlikely. 

Based on the assumed northwestern groundwater flow direction, AOI 4 is potentially upgradient 

of potable wells. Because the drinking water supply wells may be impacted by potential releases 

at the AOIs, the exposure pathway for groundwater to onsite receptors is potentially complete.

However, as discussed in Section 7.2.1, PFOA, PFOS, PFHxS, PFNA and PFBS were not 

detected in the Camp Roberts potable well network during a March 2017 PFAS sampling event. 

The CSM for AOI 4 is presented on Figure 7-4. 

7.3 Surface Water and Sediment Exposure Pathway

The SI results in soil and groundwater, in combination with knowledge of the fate and transport 

properties of PFAS, were used to determine whether a potentially complete pathway exists 

between the source and potential receptors.

7.3.1 AOI 1 - AOI 4 

PFAS are water soluble and can migrate readily from soil to surface water via leaching and runoff. Because PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil and groundwater at 

AOI 1 through AOI 4, it is possible that those compounds may have migrated from soil and 

groundwater to the Salinas River via groundwater discharge or surface water flow. Therefore, the 

surface water and sediment ingestion exposure pathway is considered potentially complete for 

site workers and construction workers. All surface water draining from Camp Roberts flows to the 

Salinas River or one of its tributaries, which include the San Antonio and Nacimiento Rivers and 

San Marcos Creek. Waters in the Salinas River flow through Monterey County to the Monterey 

Bay National Marine Sanctuary in the Pacific Ocean. Due to potential recreational use of the 

Salinas River, the surface water and sediment ingestion exposure pathway for off-facility 

recreational users is considered potentially complete. The CSMs for AOI 1 through AOI 4 are 

presented on Figure 7-1 through Figure 7-4, respectively. 

7.3.2 AOI 5 & AOI 6 

Because PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil at AOI 5 and AOI 6, it is 

possible that those compounds may have migrated from soil to the Salinas River via surface water 

flow. Therefore, the surface water and sediment ingestion exposure pathway is considered 

potentially complete for site workers and construction workers. All surface water draining from

Camp Roberts flows to the Salinas River or one of its tributaries, which include the San Antonio 

and Nacimiento Rivers and San Marcos Creek. Waters in the Salinas River flow through Monterey 

County to the Monterey Bay National Marine Sanctuary in the Pacific Ocean. Due to potential 

recreational use of the Salinas River, the surface water and sediment ingestion exposure pathway 

for off-facility recreational users is considered potentially complete. 
Media

SOURCE PATHWAY RECEPTOR

AOI 1 Fire Training 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

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-1

Conceptual Site Model, AOI 1

Camp Roberts

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

1. The resident and recreational users refer to offsite receptors.

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-5
Media

SOURCE PATHWAY RECEPTOR

AOI 2 Fire Training 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

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-2

Conceptual Site Model, AOI 2

Camp Roberts

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

1. The resident and recreational users refer to offsite receptors.

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-6
Media

SOURCE PATHWAY RECEPTOR

AOI 3 Fire Training 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

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-3

Conceptual Site Model, AOI 3

Camp Roberts

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

1. The resident and recreational users refer to offsite receptors.

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-7
Media

SOURCE PATHWAY RECEPTOR

AOI 4 Fire Training 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

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-4

Conceptual Site Model, AOI 4

Camp Roberts

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

1. The resident and recreational users refer to offsite receptors.

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-8
Media

SOURCE PATHWAY RECEPTOR

AOI 5 Incidental Spills 

of Stored AFFF 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

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-5

Conceptual Site Model, AOI 5

Camp Roberts

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

1. The resident and recreational users refer to offsite receptors.

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-9
Media

SOURCE PATHWAY RECEPTOR

AOI 6 Incidental Spills 

of Stored AFFF 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

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-6

Conceptual Site Model, AOI 6

Camp Roberts

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

1. The resident and recreational users refer to offsite receptors.

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-10
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 8-1

8. Summary and Outcome

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

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

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

8.1 SI Activities 

The SI field activities were conducted from 10 to 27 May 2021 and consisted of utility clearance, 

hollow stem auger drilling, soil sample collection, permanent monitoring well installation, 

groundwater sample collection, and land surveying. Field activities were conducted in accordance 

with the SI QAPP Addendum (AECOM, 2021b), except as previously noted in Section 5.8. 

To fulfill the project DQOs set forth in the approved SI QAPP Addendum (AECOM, 2021b), samples 

were collected and analyzed for a subset of 18 compounds by LC/MS/MS compliant with QSM 5.3 

Table B-15 as follows. 

• Twenty-eight (28) soil samples from 20 surface soil and deeper boring locations;

• Four grab groundwater samples from four permanent well locations;

• Seventeen (17) QA/QC samples.

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

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

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

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

required. Additionally, the CSMs were refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at the AOIs, which are 

described in Section 7. 

8.2 Outcome 

Based on the results of this SI, further evaluation under CERCLA is warranted in an RI for AOI 1, 

AOI 2, AOI 3, and AOI 5; no further evaluation is warranted for AOI 4 and AOI 6 at this time (see 

Table 8-1). Based on the CSMs developed and revised in light of the SI findings, there is potential 

for exposure to drinking water receptors from AOI 2 andAOI 3 from sources on the facility resulting 

from historical DoD activities. Sample analytical concentrations collected during the SI were 

compared against the project SLs in soil and groundwater, as described in Table 6-1. A summary 

of the results of the SI data relative to the SLs is as follows: 

• At AOI 1:

• PFOS in soil exceeded the SL of 13 μg/kg, with a maximum concentration of 443 J

μg/kg at location AOI01-01.

• The detected concentrations of PFOS and PFBS in groundwater at AOI 1 were below

their respective SLs. PFOA, PFHxS, and PFNA were not detected in groundwater at

AOI 1.

• Based on the exceedances of the SL in soil, further evaluation of AOI 1 is warranted

in the RI.
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 8-2

• At AOI 2:

• PFOS in soil exceeded the SL of 13 μg/kg, with a maximum concentration of 584 J

μg/kg at location AOI02-04.

• PFOS and PFHxS in groundwater exceeded their respective SLs. PFOS exceeded

the SL of 4 ng/L, with a concentration of 15.7 J ng/L at location AOI02-02. PFHxS

exceeded the SL of 39 ng/L, with a concentration of 85.6 J ng/L at location AOI02-

02.

• Based on the exceedances of the SLs in soil and groundwater, further evaluation of

AOI 2 is warranted in the RI.

• At AOI 3:

• PFOS in soil exceeded the SL of 13 μg/kg, with a maximum concentration of 44.7 J

μg/kg at location AOI03-03.

• PFOA and PFHxS in groundwater exceeded their respective SLs. PFOA exceed the

SL of 6 ng/L, with a maximum concentration of 8.09 J ng/L at location AOI03-01.

PFHxS exceed the SL of 39 ng/L, with a maximum concentration of 79.5 J ng/L at

location AOI03-01.

• Based on the exceedances of the SLs in soil and groundwater, further evaluation of

AOI 3 is warranted in the RI.

• At AOI 4:

• The detected concentrations of PFOA, PFOS, PFHxS, PFNA, and PFBS in soil at

AOI 4 were below their respective SLs.

• The detected concentration of PFOS in groundwater at AOI 4 was below the SL.

• Based on the results of the SI, no further evaluation of AOI 4 is warranted.

• At AOI 5:

• PFOS in soil exceeded the SL of 13 μg/kg, with a maximum concentration of 49.3

μg/kg at location AOI05-02. Based on the results of the SI, further evaluation of AOI

5 is warranted in the RI.

• At AOI 6:

• The detected concentrations of PFOS, PFHxS, and PFNA in soil at AOI 6 were below

their respective SLs. PFOA and PFBS were not detected in soil. Based on the results

of the SI, no further evaluation of AOI 6 is warranted.

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

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

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

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

AFFF and based on its history including distribution limitations that restricted use of GenX, it is 

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

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

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

be considered for further investigation under CERCLA and undergo an RI. 
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 8-3

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

AOI Potential 

Release Area

Soil –

Source Area

Groundwater –

Source Area Future Action

1 

East Garrison Old Fire Station Proceed to RI 

Army Airfield AFFF Storage N/A Proceed to RI

2 East Garrison Old FTA Proceed to RI

3 

Main Garrison FTA 2 Proceed to RI

Building 7020 N/A Proceed to RI

4 CR FD Fire Station and Shipping 

Container No further action

5 CR FD Building 3000 N/A No further action

Main Garrison Fuel Station N/A Proceed to RI

6 

TUAS Hangar Building 17002 N/A No further action

NPS Airfield Shed AFFF Storage N/A No further action

Legend:

N/A = not applicable

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 8-4

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

Camp Roberts, San Miguel, California

AECOM 9-1

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