FINAL

Site Inspection Report 

MTA Camp Rilea

Warrenton, Oregon

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

August 2023 

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED
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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 ......................................................................................................2-2

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

2.2.3 Hydrology....................................................................................................2-4

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

2.2.5 Current and Future Land Use......................................................................2-5

2.2.6 Sensitive Habitat and Threatened/ Endangered Species.............................2-5

2.3 History of PFAS Use..............................................................................................2-6

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

3.1 AOI 1 Former Fire Station – Building 7241 ............................................................3-1

3.2 AOI 2 UTES: Former Firetruck Parking – Building 7156 ........................................3-1

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 Temporary Well Installation and Groundwater Grab Sampling...............................5-3

5.4 Sediment Sampling ...............................................................................................5-4

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

5.6 Surveying..............................................................................................................5-4

5.7 Investigation-Derived Waste..................................................................................5-5

5.8 Laboratory Analytical Methods ..............................................................................5-5

5.9 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 ......................................................................................6-3

6.4 AOI 2.....................................................................................................................6-3
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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 Sediment Analytical Results ..............................................................6-4

6.4.4 AOI 2 Conclusions ......................................................................................6-4

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

7.2 Groundwater Exposure Pathway...........................................................................7-2

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

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

7.3 Surface Water and Sediment Exposure Pathway ..................................................7-3

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

7.3.2 AOI 2...........................................................................................................7-3

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

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, January 2022

Figure 2-5 Surface Water Features

Figure 3-1 Areas of Interest

Figure 5-1 Site Inspection Sample Locations

Figure 6-1 PFOA Detections in Soil

Figure 6-2 PFOS Detections in Soil

Figure 6-3 PFBS Detections in Soil

Figure 6-4 PFHxS Detections in Soil

Figure 6-5 PFNA Detections in Soil

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

Figure 6-7 PFHxS and PFNA Detections in Groundwater

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

Figure 6-9 PFHxS and PFNA Detections in Sediment

Figure 7-1 Conceptual Site Model, AOI 1

Figure 7-2 Conceptual Site Model, AOI 2

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, Temporary 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

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 6-6 PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Sediment

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

ANG Air National Guard

AOI Area of Interest

ARNG Army National Guard

bgs below ground surface 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CoC chain of custody

CSM conceptual site model

DA Department of the Army

DoD Department of Defense

DOT Department of Transportation

DPT direct push technology

DQO data quality objective

DUA data usability assessment

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

FedEx Federal Express

FTA Fire Training Area

GRPS Ground Penetrating Radar Systems

HDPE high-density polyethylene 

HFPO-DA hexafluoropropylene oxide dimer acid

IDW investigation-derived waste

ITRC Interstate Technology Regulatory Council

LC/MS/MS liquid chromatography with tandem mass spectrometry

LW Lake and Wetland

MDL Method Detection Limit

MIL-SPEC military specification

MR Military Reserve

ND non-detect

NELAP National Environmental Laboratory Accreditation Program

ng/L nanograms per liter

NOAA National Oceanic and Atmospheric Administration

NS Natural Shorelands

ORDEQ Oregon Department of Environmental Quality

OPR Open Space Parks and Recreation

ORARNG Oregon Army National Guard

OSD Office of the Secretary of Defense
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OWRD Oregon Water Resources Department

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PID photoionization detector

PQAPP Programmatic UFP-QAPP

PVC polyvinyl chloride

QA quality assurance

QAPP Quality Assurance Project Plan

QC quality control

QSM Quality Systems Manual

RA-5 Residential Agriculture

RV Recreational Vehicle

SI Site Inspection

SL screening level

SOP standard operating procedure

TOC total organic carbon

TPP Technical Project Planning

UCMR3 Third Unregulated Contaminant Monitoring Rule

UFP Uniform Federal Policy

US United States

USACE United States Army Corps of Engineers

USCS Unified Soil Classification System

USDA United States Department of Agriculture

USDOI United States Department of the Interior

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

USGS United States Geological Survey

UTES Unit Training Equipment Site
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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 two 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 Military Training Area (MTA) Camp Rilea in Warrenton, 

Oregon and determined further investigation is warranted for AOI 1: Former Fire Station – Building 

7241 and AOI 2: Unit Training Equipment Site (UTES): Former Firetruck Parking – Building 7156. 

MTA Camp Rilea will also be referred to as Camp Rilea or the “facility” throughout this document.

Camp Rilea is on the Pacific Coast in northwest Oregon in Clatsop County, approximately 1.4 

miles to the southwest of the City of Warrenton and 5.7 miles to the southwest of the City of 

Astoria. Camp Rilea has operated at the Warrenton location since 1927, under the jurisdiction of 

the State of Oregon, as a training facility for ARNG. The facility was formerly known as Camp 

Clatsop until the name was changed to Camp Rilea in 1959. Numerous improvements were made 

to the original facility during the 1930s. Prior to World War II, the facility was used as a mobilization 

site for the 249th Coast Artillery. After the war, the facility was used as an annual training site by 

many military and non-military groups: air defense units; ARNG infantry, field artillery, and 

engineering units; infantry divisions; Special Forces Groups; various ANG communications units; 

Marine Corps; Coast Guard and Navy Reserve Units; Search and Rescue Organizations; Oregon 

State Defense Force; Oregon State Police and other police organizations; Housing Authority of 

Portland for Camp Rosenbaum; and various local and civic organizations (AECOM Technical 

Services, Inc., 2020).

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

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 and AOI 2.

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 

Former Fire 

Station – 

Building 7241

Proceed to RI 

2 

UTES: Former 

Firetruck 

Parking – 

Building 7156

Proceed to RI

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels
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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 Military Training Area

(MTA) Camp Rilea in Warrenton, Oregon. MTA Camp Rilea is also referred to as Camp Rilea or 

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 Rilea (AECOM, 2020) that identified two Areas of Interest (AOIs) 

where PFAS-containing materials may have been used, stored, disposed, or released historically. 

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 Rilea is located in Warrenton, Clatsop County, Oregon, approximately 1.4 miles to the 

southwest of the City of Warrenton and 5.7 miles to the southwest of the City of Astoria. The 

facility is located west of Highway 101 and includes approximately 3 miles of ocean frontage along 

the Pacific Ocean (Figure 2-1). 

The facility is occupied and operated by the Oregon ARNG (ORARNG) as a military training center 

for military personnel and encompasses 1,870 acres (Mitchell, 2001). Civilians also use certain 

areas throughout Camp Rilea for recreational purposes throughout the year. Camp Rilea’s 

mission for the federal government is to provide facilities and resources as a training center 

contributing readiness and military capability for the armed forces of the US and Oregon. Camp 

Rilea’s mission for the State of Oregon is to provide community service support and serve as the 

regional base for Oregon’s North Coast emergency response and recovery operations (Oregon, 

2018). 

The facility consists of the cantonment area and armory (450 acres), training and range areas 

(1,400 acres), and a wastewater treatment facility with two sewage lagoons adjacent to a spray 

irrigation area (20 acres) (DA, 2001). Camp Rilea’s cantonment area encompasses dining and 

support facilities and temporary living facilities; numerous buildings are scattered across the 

facility for administration, maintenance, medical, petroleum oil and fuel storage, equipment and 

vehicles storage (including at the Unit Training Equipment Site [UTES] facility), and a fire station 

building (DA, 2001). The Air National Guard (ANG) facility operates on approximately 6.25 acres 

along the central/eastern Camp Rilea boundary and consists primarily of a building within a fenced 

area (DA, 2001). Access to Camp Rilea is controlled. Camp Rilea also uses up to 352,000 acres 

of private and public land for military training under landowner agreements and permits (DA, 

2001).

The property that Camp Rilea currently occupies is owned by the State of Oregon, with operations 

beginning in 1927 (DA, 2001). The facility was formerly known as Camp Clatsop until the name 

was changed to Camp Rilea in 1959. Numerous improvements were made to the original facility 

during the 1930s. Prior to World War II, the facility was used as a mobilization site for the 249th 

Coast Artillery. After the war, the facility was used as an annual training site by the 237th Air 

Defense Group (later named the 249th Air Defense Group) and by air defense units from 

Washington, Nevada, Delaware, and Pennsylvania (Shaw Environmental Inc. [Shaw], 2010; DA, 

2001). Camp Rilea has been used by various military units to conduct annual or inactive duty 

training, including: ARNG infantry, field artillery, and engineering units; Infantry Divisions (2nd, 

25th, and 75th); Special Forces Groups (1st, 19th, and 20th); various ANG communications units; 

Marine Corps; Coast Guard and Navy Reserve Units; Search and Rescue Organizations; Oregon 

State Defense Force; Oregon State Police and other police organizations; Housing Authority of 

Portland for Camp Rosenbaum; and by various local and civic organizations.

2.2 Facility Environmental Setting

Camp Rilea is situated in the Coast Range of the Pacific Border geologic province of Oregon 

(Oregon Department of Environmental Quality [ORDEQ], 2013; US Department of the Interior 

[USDOI], 2018). The facility is bordered by the Pacific Ocean to the west, low lying sand dunes 

to the north and south, and low-lying wetlands and agricultural land to the east (Figure 2-2). The 

Coast Mountain Range is located further to the east. The western facility boundary is comprised 

of sand dunes that parallel the beach from north to south. A series of five sand dune ridges and 
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five interdune areas, oriented north to south, are located throughout the facility; the dunes are 

separated by lakes and creeks (DA, 2001; URS and Arcadis, 2013).

The facility is moderately hilly throughout, with steeper slopes found in the western portion 

characterized by sand dunes; slopes of the sand dunes are less than 10 percent (%). Elevation 

throughout the facility ranges from sea level at the beach up to 75 feet above mean sea level 

(amsl) at the sand dunes. Many of the dunes are covered by vegetation (i.e., brush and trees). 

Elevation along the eastern facility boundary averages 45 feet amsl, with a low of 25 feet amsl in 

the northeastern portion (DA, 2001; Google Earth, 2018).

2.2.1 Geology

Camp Rilea is located in a geologic area characterized as Dune sand of the Holocene age (Figure 

2-3). Dune sand consists of large areas of windblown sand composed of rock-forming minerals, 

mostly feldspar and small amounts of quartz. Constituents are characterized as unconsolidated, 

coarse-detrital sand (US Geological Survey [USGS], 2018a). This geological feature is found 

along the northern Oregon Coastline, extending south to Tillamook Head (approximately 5 miles 

north and 11 miles south of Camp Rilea, respectively) (Frank, 1970).

Dune sand of the Pleistocene and Holocene ages overlies eroded surfaces of the Astoria 

Formation of the Tertiary age. This rock formation underlies the eastern edge of the dunes and 

constitutes bedrock of the sand-dune area, characterized as fine grained and tightly compacted, 

primarily carbonaceous sandstone. The Astoria Formation is a layer up to 1,400 feet thick; dune 

sand layers may be greater than 100 feet thick, and these deposits contain the principal aquifers. 

The geology of the northern Oregon Coast area is characterized by a small extent of alluvium of 

the Quaternary age, characterized by clay, silt, and sand. Dune sand ranges in size from coarse 

to very fine, consisting mostly of quartz with lesser amounts of feldspar, magnetite, mica, and rock 

fragment. Sand is loosely compacted and unconsolidated (Frank, 1970; DA, 2001).

During the SI, fine- to medium-grained, poorly graded sand was observed as the dominant 

lithology of the unconsolidated sediments below Camp Rilea. The borings were completed at 

depths between 7 and 30 feet below ground surface (bgs). These results and facility observations 

are consistent with the reported depositional environment of the region. Boring logs are presented 

in Appendix E.

2.2.2 Hydrogeology

Soils beneath Camp Rilea consist of six different series. From west to east across the facility, the 

soil series are beaches, dune lands, Gearheart fine sandy loam, Heceta-Waldport fine sand, 

Waldport fine sand, and Warrenton loamy fine sand (URS and Arcadis, 2013; US Department of 

Agriculture [USDA], 2018). Beaches are present along the entire western border of the facility, at 

the edge of the Pacific Ocean. Dune lands are present along the entire western boundary of the 

facility, east of the beaches. The beaches and dune lands are characterized with high infiltration 

rates. Warrenton soils are present only in the northeastern portion of the facility. With exception 

for beaches and dune lands, all the soil series beneath the facility consist of very deep and poorly

drained to excessively drained soils formed in sand, dune sands, or eolian sands, located in 

interdunal depressions or on stabilized sand dunes (DA, 2001).

The Dune sands are the primary water-bearing unit in the area (DA, 2001; Frank, 1970). Camp

Rilea is situated above the Pacific Northwest basin-fill aquifer, characterized as unconsolidated 

sand and gravel aquifers at or near the land surface. This type of aquifer is prevalent along stream 

valleys and in lowlands associated with erosional basins and yields a sufficient supply of fresh 

water (and saltwater along the Coast) for public drinking via wells and springs. These deposits 

are mostly alluvial but also consist of eolian, glacial, or volcanic deposits in other areas. The 

thickness of the deposits in stream valleys is typically less than 250 feet. Permeability of the 
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aquifer is variable, depending on the soil series. The dune sands have saturated thicknesses 

ranging from 95 to greater than 150 feet, with most of the discharge flowing west towards the 

ocean (Frank, 1970). Sand and gravel commonly yield groundwater to wells in the range of 20 to 

20,000 gallons per minute (USGS, 1994, 2018b, 2018c). 

Because precipitation infiltrates Dune sands fairly rapidly, precipitation recharges groundwater 

and is distributed fairly evenly throughout the dune area. Approximately 5 inches of precipitation 

raises groundwater levels from their low stages on a monthly basis. Hydraulic gradients near the 

sides of the Dune sand aquifer steepen, causing groundwater to flow towards discharge areas. 

Neacoxie Creek receives groundwater recharge throughout the year, and flow increases in a 

downstream direction (Frank, 1970). Regionally, the water table in the Dune sand fluctuates in 

association with recharge from precipitation, which is quickly absorbed and stored in the Dune 

sand. During warm weather months with little to no precipitation (spring and summer), 

groundwater levels in wells decline. Water level fluctuations in the area are also a result of tidal 

movements. Perched groundwater in the area is noted seasonally, primarily during the wet months 

of fall and winter. (Frank, 1970). The aquifer of the Astoria Formation is recharged in the Coast 

Range to the east of Camp Rilea and discharges at the range margins both to the east and west. 

Groundwater flow beneath Camp Rilea in the bedrock aquifer is toward submarine recharge 

zones to the west. With relatively low hydraulic conductivity, there is likely little interaction between 

the Dune sand and bedrock aquifers (DA, 2001).

The estimated depth to groundwater at the facility (measured historically at several onsite 

groundwater wells in 2001) ranges from 22.6 to 32.8 feet bgs (DA, 2001) Groundwater flow 

beneath Camp Rilea is generally from east to west, towards the Pacific Ocean. However, 

groundwater flow may vary in localized areas of groundwater recharging to surface water, such 

as Neacoxie Creek in the eastern portion of the facility (DA, 2001; URS and Arcadis, 2013). 

Neacoxie Creek flows off-Post to the east, eventually discharging into the Columbia River 

approximately three miles to the northeast of the facility, and ultimately discharging into the Pacific 

Ocean (AMEC, 2009). A USGS monitoring well located on the facility at a depth of 135 feet bgs 

(Site No. CLAT0050230) has groundwater measurements ranging from 10 to 17 feet bgs (USGS, 

2018c) (Figure 2-3). 

Camp Rilea obtains drinking water from two onsite water supply wells located in the 

central/western portion of the facility, east of the beach (Wells #53837 and #53838) (ORDEQ, 

2018; Oregon Water Resources Department [OWRD], 2018). Both wells were installed in 2011 

and completed with 10-inch diameter casing. Well #53837 was drilled to a depth of 172 feet bgs 

and completed with 20 feet of stainless steel 0.02 slotted screen from 142 to 162 feet bgs. Well 

#53838 was drilled to a depth of 157 feet bgs and completed with 15 feet of stainless steel 0.02 

slotted screen from 132 to 147 feet bgs. Depth to groundwater measurements at wells #53837 

and #53838 were 58 feet bgs and 50 feet bgs, respectively (OWRD, 2018). The two wells are 

located approximately 0.5 miles west of AOI 2 and 0.75 miles northwest of AOI 1.

PFAS sampling has been performed at Camp Rilea under the direction of the ARNG. The drinking 

water wells at Camp Rilea were sampled in April 2017 and laboratory analysis included the 

relevant compounds. PFOA was detected at a concentration of 0.719 nanograms per liter (ng/L). 

PFOS, PFBS, PFHxS, and PFNA concentrations were reported below laboratory method 

detection limits (MDLs) (ORDEQ, 2018). The reported laboratory MDLs were below the ORDEQ 

Pollutant Initiation Levels (PILs) (Oregon Administrative Rule [OAR 340-045-0100]).

Public groundwater systems used as drinking water sources are located at off-Post facilities, 

including the Sunset Lake recreational vehicle (RV) Park (located approximately 0.5 miles to the 

south of the facility) and the City of Warrenton (located less than 1 mile to the north of the facility) 

(ORDEQ, 2018) (Figure 2-3). Within a 4-mile radius of Camp Rilea, the Clatsop Plains Aquifer is 

used for private water supplies, and as of 2001, approximately 300 private well users were 

estimated to be within a 1- to 4-mile radius of the facility (DA, 2001). 
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AECOM 2-4

Depths to water measured in January 2022 during the SI ranged from 1.90 to 23.05 feet bgs. 

Groundwater elevation contours from the SI are presented on Figure 2-4 and indicate the 

groundwater flow direction at AOI 1 at Camp Rilea is primarily to the east-southeast, while 

groundwater flow direction at AOI 2 is primarily to the west-southwest. 

2.2.3 Hydrology

Camp Rilea is located within the Necanicum River subbasin of the North Coast/Lower Columbia 

basin. Within this feature, the eastern portion of the facility is located within the Skipanon/RiverFrontal Columbia River Watershed, the western portion of the facility is located within the Arch 

Cape Creek-Frontal Pacific Ocean Watershed, and the southeastern portion of the facility is 

located in the Lower Necanicum River Watershed (Figure 2-3). Rivers in the North Coast 

subbasin generally begin in the steep terrain of the Coast Mountain Range, located east of Camp 

Rilea. Rivers to the west of the Coast Mountain Range, near the Pacific Coast, are surrounded 

by wetlands and agriculture (ORDEQ, 2003). 

Surface waterbodies at the facility include Neacoxie Creek (including a slough), Sunset Lake, and 

Slusher Lake. Neacoxie Creek originates south of the facility flowing north paralleling the eastern 

property boundary (east fork), entering the central/eastern properly and turning 180 degrees to 

flow south along the eastern property boundary (west fork), before flowing offsite to the east into 

the Skipanon River, which ultimately discharges to the north into the Columbia River. Sunset Lake 

is located in the southeastern corner of the property, where drainage flows south to the Necanicum 

River, ultimately discharging into the Pacific Ocean to the west (DA, 2001). Slusher Lake is located 

in the south/central portion of the facility and is connected to a smaller lake on the adjacent 

property to the south, ultimately discharging to Neacoxie Creek (Frank, 1970; DA, 2001; Shaw, 

2010).

Surface stormwater runoff from paved areas of the facility enters a storm drainage conveyance 

system located throughout the majority of the cantonment area, discharging to an outfall in 

Neacoxie Creek (west fork), located to the west of the facility. Stormwater throughout unpaved 

areas of the property infiltrates the sandy soil (DA, 2001; Shaw, 2010). Because precipitation 

infiltrates Dune sands rapidly, surface water runoff throughout the facility is negligible. Surface 

water runoff at Camp Rilea would occur during heavy precipitation events where precipitation 

exceeds the infiltration rate of the sandy soil (Frank, 1970). Surface water features are presented 

on Figure 2-5.

2.2.4 Climate

Climate at Camp Rilea is marine temperate. Climate of the North Coast Basin is cool and moist, 

characterized by mild summers and wet winters, with moderately low temperatures. The area 

receives heavy rainfall from easterly storms originating in the Pacific Ocean that traverse the 

Cascade Mountain Range to the east. The majority of precipitation occurs as rain during the fall 

and winter, with heavy rainfall experienced between November and March; at least one or two 

heavy storm events occur annually. Snowfall is rare, and the area experiences a frost-free period 

for 200 to 240 days, annually. Winds prevail from the northwest during summer months and from 

the southwest (off the Pacific Coast) during winter months (Frank, 1970; ORDEQ, 2003; URS and 

Arcadis, 2013).

Temperatures recorded for a period of three decades (1961 to 1990) at the Astoria Regional 

Airport weather station (located approximately 2.8 miles northeast of the facility) ranged from a 

low of 36 degrees Fahrenheit (°F) in January to a high of 69 °F in August, averaging 51 °F 

annually. Precipitation recorded for this same time period ranged from an average low of 1.2 

inches in July to an average high of 10.6 inches in December, averaging 6.6 inches annually 

(ORDEQ, 2003).
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 2-5

Temperatures recorded for the most recent time period (2020) at Astoria Regional Airport weather 

station ranged from a low of 37.4°F in February to a high of 68.7°F in August, averaging 51.4°F 

for the year. Precipitation for this same year ranged from a low of 0.83 inches in July to a high of 

11.05 inches in November, averaging 5.9 inches for the year (snow was not reported) (National 

Oceanic and Atmospheric Administration [NOAA], 2022).

2.2.5 Current and Future Land Use

Camp Rilea’s mission for the federal government is to provide facilities and resources as a training 

center contributing readiness and military capability for the armed forces of the US and Oregon. 

Camp Rilea’s mission for the State of Oregon is to provide community service support and serve 

as the regional base for Oregon’s North Coast emergency response and recovery operations 

(Oregon, 2018). 

Access to the facility is controlled. Land use to the north, east, and south is a mixture of residential 

and agriculture with interspersed sand dunes and wetlands. The Astoria Golf and Country Club is 

located east of the southeast corner of the facility. The Pacific Ocean is located adjacent to the 

west. The nearest urban area is Warrenton, 1.4 miles to the northeast.

The facility is zoned by Clatsop County primarily as Military Reserve (MR), with smaller footprints 

zoned as Residential Agriculture 5 (RA-5), Lake and Wetland (LW), Natural Shorelands (NS), and 

Open Space Parks and Recreation (OPR) (Clatsop County, 2018). These additional zoning codes 

are associated with the surface waterbodies on the facility, in addition to the residential/agricultural 

land that OMD also uses for training (Clatsop County, 2018).

Land to the north of the facility is zoned by the City of Warrenton as Open Space Institutional, 

Lake and Freshwater Wetland, and R40 - Low Density Residential (City of Warrenton, 2020). 

Land to the south of the facility is zoned by Clatsop County as LW, OPR, Residential Agriculture 

1 (RA-1), and RA-5. Land to the east of the facility is zoned Single Family Residential, RA-5, 

Agriculture Forest, and LW (Clatsop County, 2018).

Clatsop County’s Comprehensive Plan does not specify restrictions for Camp Rilea or future land 

use changes at Camp Rilea (Clatsop County, 2013). The MR-zoned areas of Camp Rilea are 

defined by Clatsop County as “intended to accommodate the immediate foreseeable demand for 

military activities in areas where a commitment to such activities has already occurred through 

existing uses by the military.” (Mitchell, 2001). It is anticipated that Camp Rilea will remain used 

for military-related uses, including training, in the future. In addition, it is anticipated that the OPR-

, RA-5-, LW-, and NS-zoned footprints of Camp Rilea will remain used for their intended purpose, 

as zoned (Mitchell, 2001).

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

A wildlife survey has not occurred at the facility, and the facility does not have any significant areas 

of habitat. The following species have not been identified at the facility but may be present in the 

surrounding area. 

The following birds, plants, mammals, and reptiles are federally endangered, threatened, 

proposed, and/ or are listed as candidate species in Clatsop, Oregon (US Fish and Wildlife 

Service [USFWS], 2022).

• Birds: Hawaiian petrel, Pterodroma sandwichensis (Endangered); Western snowy plover, 

Charadrius nivosus (Threatened); Marbled murrelet, Brachyramphus marmoratus 

(Threatened); Yellow-billed Cuckoo, Coccyzus americanus (Threatened); Short-tailed 

albatross, Phoebastria (=Diomedea) albatrus (Endangered); Northern spotted owl, Strix 
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 2-6

occidentalis caurina (Threatened); Streaked Horned lark, Eremophila alpestris strigata

(Threatened)

• Fishes: Bull Trout, Salvelinus confluentus (threatened)

• Flowering Plants: Nelson's checker-mallow, Sidalcea nelsoniana (Threatened)

• Insects: Monarch butterfly, Danaus plexippus (Candidate); Oregon silverspot butterfly, 

Speyeria zerene hippolyta (Threatened)

• Mammals: Little brown bat, Myotis lucifugus (Under Review); Pacific Marten, Martes 

caurina (Threatened); Red tree vole, Arborimus longicaudus (Candidate); Columbian whitetailed deer, Odocoileus virginianus leucurus (Threatened)

• Reptiles: Loggerhead sea turtle, Caretta (Endangered); Olive ridley sea turtle, Lepidochelys 

olivacea (Threatened); Leatherback sea turtle, Dermochelys coriacea (Endangered)

• Snails: Burrington jumping-slug, Hemphillia burringtoni (Resolved Taxon)

2.3 History of PFAS Use

Two AOIs were identified in the PA where AFFF may have been used, stored, disposed, or 

released historically at Camp Rilea (AECOM, 2020). AFFF may have historically been released 

at the facility during washing of firetrucks carrying AFFF, flushing out lines used for AFFF 

discharge at other locations, and storage of AFFF as early as the 1970s. The potential release 

areas were grouped into two AOIs based on preliminary data and presumed groundwater flow 

directions. A description of each AOI is presented in Section 3.
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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, two potential release areas were 

identified at Camp Rilea and were designated AOIs (AECOM, 2020). The potential release areas 

are shown on Figure 3-1. 

3.1 AOI 1 Former Fire Station – Building 7241

AOI 1 is Building 7241, a former fire station currently occupied by Public Works offices. The former 

fire station dates back to the early 1970s and was operational until at least 1980. Facility personnel 

interviewed could not confirm if a firetruck was operated or parked at the former station. Given 

the history of AFFF reportedly contained in the firetrucks parked at the UTES between 1989 and 

1995 (refer to AOI 2 below), it is assumed if any firetrucks were parked at the former fire station, 

it would have also contained AFFF. Activities at the former fire station may have included washing 

the firetruck carrying AFFF, flushing out lines used for AFFF discharge at other locations, and 

storage of AFFF. 

3.2 AOI 2 UTES: Former Firetruck Parking – Building 7156

AOI 2 is the UTES Former Firetruck Parking area surrounding Building 7156 in the central/eastern 

portion of the facility. One firetruck (model 530C) was present on-Post between 1989 and 1995. 

Another firetruck (model 2500L) was present on-Post from 1995 until an unknown time period. 

Both firetrucks, which had tank capacities of approximately 50 gallons each, reportedly contained 

AFFF. AFFF from the former firetrucks was reportedly never deployed on-Post. OMD maintenance 

personnel performed minor repairs and maintenance of the former firetrucks at the UTES. 
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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, 2021a), 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 Rilea (AECOM, 2020);

• Analytical data collected as part of ARNG drinking water well sampling efforts around the 

facility (ORDEQ, 2018):

• PFOA was detected at a concentration of 0.719 ng/L. PFOS, PFBS, PFHxS, and 

PFNA concentrations were reported below laboratory MDLs;

• 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, 2021a); 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). Temporal boundaries were limited to the winter 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, 2021a).
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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 (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, 2021a).
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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 Rilea, dated February 2020 (AECOM, 2020);

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

Camp Rilea, Warrenton, Oregon dated September 2021 (AECOM, 2021a); and

• Final Site Safety and Health Plan, Camp Rilea, Warrenton, Oregon dated September 2021

(AECOM, 2021b).

The SI field activities were conducted from 11, 12, and 18 to 19 January 2022 and consisted of

utility clearance, direct push boring, soil sample collection, temporary monitoring well installation,

grab groundwater sample collection, sediment collection, and land surveying. Field activities were 

conducted in accordance with the SI QAPP Addendum (AECOM, 2021a).

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:

• Thirteen (13) soil samples from six boring locations;

• Six grab groundwater samples from six temporary wells; 

• Two sediment samples from two locations;

• Thirteen (13) quality assurance (QA)/quality control (QC) samples.

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

list of samples collected for each 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 are provided in Appendix B2, and 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 
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MTA Camp Rilea, Warrenton, Oregon

AECOM 5-2

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

address the AOIs identified in the PA. 

A combined TPP Meeting 1 and 2 was held on 30 June 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, ORARNG, USACE, Oregon DEQ, Oregon Health 

Authority, representatives familiar with the facility, and the regulations. 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, 2021a).

A TPP Meeting 3 was held after the field event (TBD) 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 placed a ticket with the USA North 811 “Call Before You Dig” Oregon utility clearance 

provider to notify them of intrusive work on 12 January 2022. 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 11 January 2022

with input from the AECOM field team and Camp Rilea 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

PFAS-free ASTM Type II deionized water was purchased from Grainger and used in this 

investigation as the main source of decontamination for drilling equipment. Two equipment blanks 

were collected during the event (CR-ERB-01 and CR-ERB-02) and analyzed by LC/MS/MS 

compliant with QSM 5.3 Table B-15. The results of the decontamination water samples associated 

with the equipment blanks 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, 2021a). 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. Soil samples were collected via direct push technology (DPT), in accordance with the 

SI QAPP Addendum (AECOM, 2021a). A GeoProbe® 6712DT dual-tube sampling system was 

used to collect continuous soil cores to the target depth. A hand auger was used to collect soil 

from the top five feet of the boring, in accordance with AECOM utility clearance procedures. The 

soil boring locations are shown on Figure 5-1 and depths are provided Table 5-1.

In general, three discrete soil samples were anticipated to be 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 2 feet above the groundwater table, and one subsurface soil sample 
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MTA Camp Rilea, Warrenton, Oregon

AECOM 5-3

at the mid-point between the surface and the groundwater table. Due to shallow groundwater at 

AOI1, only the surface soil samples were collected at each of the three boreholes and one shallow 

subsurface sample was collected at AOI01-02. All samples were collected as planned at AOI2.

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.

During the SI, fine- to medium-grained, poorly graded sand was observed as the dominant 

lithology of the unconsolidated sediments below Camp Rilea. The borings were completed at 

depths between 7 and 30 feet bgs. These results and facility observations are consistent with the 

reported 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, 2021a).

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.

DPT borings were converted to temporary wells, which were subsequently abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2021a) using bentonite chips at completion 

of sampling activities. Borings were installed in grass areas to avoid disturbing concrete or asphalt 

surfaces.

5.3 Temporary Well Installation and Groundwater Grab Sampling

Temporary wells were installed using a GeoProbe® 6712DT dual-tube sampling system. Once 

the borehole was advanced to the desired depth, a temporary well was constructed of a 5-foot

section of 1-inch Schedule 40 poly-vinyl chloride (PVC) screen with sufficient casing to reach 

ground surface. New PVC pipe and screen were used to avoid cross contamination between 

locations. The screen intervals for the temporary wells are provided in Table 5-2.

Groundwater samples were collected after a period of time after well installation to allow 

groundwater to infiltrate and recharge the temporary well screen intervals. After the recharge 

period, groundwater samples were collected using a bladder pump with PFAS-free HDPE tubing. 

The temporary wells were purged at a rate determined in the field to reduce turbidity and draw 

down prior to sampling. Water quality parameters (e.g., temperature, turbidity, specific 

conductance, pH, dissolved oxygen, and oxidation-reduction potential) were measured using a 

water quality meter and recorded on the field sampling form (Appendix B2) before each grab 

sample was collected. At each well, the turbidity did not reduce to ≤ 25 nephelometric turbidity 

units (NTU) or stabilize at a level above 25 NTU after one hour of low flow purging. In accordance 

with the SI QAPP Addendum, purging was limited to one hour prior to sampling. Additionally, a 
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MTA Camp Rilea, Warrenton, Oregon

AECOM 5-4

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, 2021a).

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.

Following well surveying (described below in Section 5.5), temporary wells were abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2021a) by removing the PVC and backfilling 

the hole with 3/8-inch hydrated bentonite gravel. Upon completion of well abandonment, the 

ground surface at each location was patched to match existing surrounding conditions.

5.4 Sediment Sampling

Sediment samples were collected from AOI 2 within the catch basin. Sediment samples collected 

in accordance with the SI QAPP Addendum (AECOM, 2021a).

A sediment coring device (hand auger) was used to collect the sediment sample from the first 2

foot of sediment. The sediment was transferred to a Ziploc bag, where the sample was 

homogenized and stones in excess of 1 centimeter were removed. The sediment sample 

locations are shown on Figure 5-1, and sample depths are provided

Table 5-1. 

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 for analysis by LC/MS/MS compliant with QSM 5.1 

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

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, equipment rinsate blank samples 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 °C during shipment.

5.5 Synoptic Water Level Measurements

A synoptic groundwater gauging event was performed on 19 January 2022. Groundwater 

elevation measurements were collected from the six new temporary monitoring wells. Water level 

measurements were taken from the northern side of the well casing. A groundwater flow contour 

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

5.6 Surveying

The northern side of each temporary well casing was surveyed by Oregon-licensed land 

surveyors following guidelines provided in the SOPs provided in the SI QAPP Addendum 

(AECOM, 2021a). Survey data from the newly installed wells on the facility were collected on 19
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MTA Camp Rilea, Warrenton, Oregon

AECOM 5-5

January 2022 in the applicable Universal Transverse Mercator zone projection with North 

American Datum of 1983 (NAD83) (horizontal) and World Geodetic System 1984 (WGS 1984)

(vertical). The surveyed well data are provided in Appendix B3.

5.7 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, 2021a) and with the DA Guidance for 

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

Soil IDW (i.e., soil cuttings) generated during the SI activities were contained in labeled, 55-gallon 

Department of Transportation (DOT)-approved steel drums and left onsite in a waste storage area

designated by ORARNG. The soil IDW was not sampled and assumes the characteristics of the 

associated soil samples collected from that source location. Based on laboratory results, 

containerized soil cuttings will be managed and disposed by ARNG, either by offsite disposal or, 

where PFAS concentrations are non-detect, ARNG will distribute the soil on the downgradient 

side of the associated borehole.

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

decontamination fluids) were contained in labeled, 55-gallon DOT-approved steel drums, and left 

onsite in the designated waste storage area specified by ORARNG. The liquid IDW was not 

sampled and assumes the PFAS 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). ARNG will further coordinate with the ORDEQ to ensure proper disposal is in 

accordance with OAR Chapter 340 and the Army Guidance for Addressing Releases of PFAS, Q18 

(DA, 2018).

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.

5.8 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.

5.9 Deviations from SI QAPP Addendum

No deviations from the SI QAPP Addendum were identified during the review of field 

documentation.
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MTA Camp Rilea, Warrenton, Oregon

AECOM 5-6

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Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Rilea, Oregon

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 D-422)

Comments

AOI01-01-SB-0-2 1/18/2022 13:40 0 - 2 X

AOI01-01-SB-4-5 1/18/2022 14:15 4 - 5 X

AOI01-02-SB-0-2 1/18/2022 12:00 0 - 2 X

AOI01-02-SB-0-2-D 1/18/2022 12:00 0 - 2 X X X FD

AOI01-02-SB-0-2-MS 1/18/2022 12:00 0 - 2 X X X MS

AOI01-02-SB-0-2-MSD 1/18/2022 12:00 0 - 2 X X X MSD

AOI01-03-SB-0-2 1/18/2022 13:55 0 - 2 X

AOI02-01-SB-0-2 1/19/2022 11:05 0 - 2 X

AOI02-01-SB-13-15 1/19/2022 11:45 13 - 15 X

AOI02-01-SB-22-23 1/19/2022 11:50 22 - 23 X X X

AOI02-01-SB-22-23-D 1/19/2022 11:50 22 - 23 X X X FD

AOI02-02-SB-0-2 1/18/2022 15:10 0 - 2 X

AOI02-02-SB-13-15 1/18/2022 16:20 13 - 15 X

AOI02-02-SB-23.5-24.5 1/18/2022 16:25 23.5-24.5 X

AOI02-03-SB-0-2 1/19/2022 8:55 0 - 2 X

AOI02-03-SB-13-15 1/19/2022 9:25 13 - 15 X

AOI02-03-SB-22-23 1/19/2022 9:45 22 - 23 X

AOI-02-04-SD-0-2 1/19/2022 14:30 0 - 2 X

AOI-02-05-SD-0-2 1/19/2022 14:00 0 - 2 X

AOI-02-05-SD-0-2-D 1/19/2022 14:00 0 - 2 X FD

AOI-02-05-SD-0-2-MS 1/19/2022 14:00 0 - 2 X MS

AOI-02-05-SD-0-2-MSD 1/19/2022 14:00 0 - 2 X MSD

AOI01-01-GW 1/18/2022 16:00 NA X

AOI01-02-GW 1/18/2022 14:25 NA X

AOI01-02-GW-D 1/18/2022 14:25 NA X FD

AOI01-02-GW-MS 1/18/2022 14:25 NA X MS

AOI01-02-GW-MSD 1/18/2022 14:25 NA X MSD

AOI01-04-GW 1/18/2022 12:55 NA X

AOI02-01-GW 1/19/2022 13:50 NA X

AOI02-02-GW 1/19/2022 10:15 NA X

AOI02-03-GW 1/19/2022 12:00 NA X

Soil Samples

Groundwater Samples

Sediment Samples

AECOM 5-7
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Rilea, Oregon

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 D-422)

Comments

CR-ERB-01 1/18/2022 10:45 NA X Hand Auger 

CR-ERB-02 1/19/2022 13:15 NA X DPT Shoe

CR-FRB-01 1/20/2022 9:00 NA X NA

Notes:

ASTM = American Society for Testing and Materials

bgs = below ground surface

CR = Camp Rilea

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, Temporary Well Screen Intervals, and Groundwater Elevations

Site Inspection Report, Camp Rilea, Oregon

Area of 

Interest

Boring 

Location

Soil Boring 

Depth 

(feet bgs)

Temporary Well 

Screen Interval 

(feet bgs)

Top of Casing 

Elevation 

(feet NAVD88)

Ground Surface 

Elevation 

(feet NAVD88)

Depth to 

Water

(feet btoc)

Dept

Wa

(feet 

AOI01-01 10 5 - 10 34.25 34.04 4.96 4.

AOI01-02 7 2 - 7 34.34 31.38 4.86 1.9AOI01-04 15 5 - 15 35.86 35.77 6.39 6.3AOI02-01 30 25 - 30 51.88 47.41 25.71 21

AOI02-02 30 25 - 30 50.54 48.45 25.14 23

AOI02-03 30 25 - 30 48.57 48.51 22.82 22

Notes:

1 Temporary well screen set above total depth to capture groundwater interface

bgs = below ground surfacebtoc = below top of casingNA = not applicableNAVD88 = North American Vertical Datum 1988

21

AECOM 
AECOM 5-10

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OM 5-10
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"J "J

"S

AOI 1

AOI 2

AOI01-01

AOI01-02

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI02-04

AOI02-05

AOI01-03

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

MB

9/19/2022

9/19/2022

PROJECT Site Inspection at Camp Rilea, OR

1:4,800

9/19/2022 ­ Figure 5-1 PM CM 9/19/2022

12420 Milestone Center Drive

Germantown, MD 20876

Site Inspection Sample Locations

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

and the GIS User Community

0 200 400 800

Feet

Legend

?! Soil Boring/Temporary

Monitoring Well

"S Surface Soil Sample

"J Catch Basin Sediment

Sample

Area of Interest

Facility Boundary

Water Body

River/Stream

Surface Water Flow

Direction

Groundwater Flow Direction

AECOM 5-11
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MTA Camp Rilea, Warrenton, Oregon

AECOM 5-12

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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 6.4. Table 6-2 through Table 6-6 present results in soil, groundwater, or sediment

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 to 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. 
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MTA Camp Rilea, Warrenton, Oregon

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: Former Fire Station – Building 7241. 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 6-7.

6.3.1 AOI 1 Soil Analytical Results

Figure 6-1 through Figure 6-5 present the ranges of detections in soil. Table 6-2 through Table 

6-4 summarize the soil results.

Surface soil was sampled from 0 to 2 feet bgs at boring locations AOI01-01 through AOI01-03

and from the shallow subsurface at 4 to 5 feet bgs from AOI01-01. Deep subsurface soil was not 

collected at AOI 1 due to shallow groundwater conditions.

PFOA, PFOS, and PFNA were detected in soil at estimated concentrations less than 1 μg/kg and 

were about two orders of magnitude below their respective SLs in surface soil. PFHxS and PFBS

were not detected in surface soil.

PFOA, PFOS, and PFNA were detected in the single shallow subsurface soil at estimated 

concentrations less than 1 μg/kg and were at least three orders of magnitude below their 

respective SLs. PFHxS and PFBS were not detected in shallow subsurface soil.

6.3.2 AOI 1 Groundwater Analytical Results

Figure 6-6 and Figure 6-7 present the ranges of detections in groundwater. Table 6-5

summarizes the groundwater results.

Groundwater was sampled from temporary monitoring wells AOI01-01, AOI01-02, and AOI01-04.

The results for detected relevant compounds are summarized below. PFNA and PFBS were not 

detected in any groundwater samples.

• PFOA was detected above the SL of 6 ng/L at AOI01-01, with a concentration of 7.66

ng/L.

• PFOA was detected below the SL of 6 ng/L at AOI01-02, with a concentration of 1.29 

J ng/L.
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AECOM 6-3

• PFOS was detected below the SL of 4 ng/L at AOI01-02, with a concentration of 3.13 

J ng/L.

• PFHxS was detected below the SL of 39 ng/L at AOI01-01, with a concentration of 

1.86 J ng/L. 

6.3.3 AOI 1 Conclusions

Based on the results of the SI, PFOA, PFOS, and PFNA were detected in soil below their 

respective SLs. PFOA in groundwater was detected above the SL of 6 ng/L at AOI01-01. Based 

on the exceedance of an SL in groundwater, further evaluation at AOI 1 is warranted.

6.4 AOI 2

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

SLs for AOI 2: UTES: Former Firetruck Parking – Building 7156. The results in soil, groundwater, 

and sediment are summarized on Table 6-2 through Table 6-6. Soil, groundwater, and sediment

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

6.4.1 AOI 2 Soil Analytical Results

Figure 6-1 through Figure 6-5 present the ranges of detections in soil. Table 6-2 through Table 

6-4 summarize the soil results.

Surface soil was sampled from 0 to 2 feet bgs, from the shallow subsurface interval of 13 to 15

feet bgs, and deep subsurface interval of 22 to 24.5 feet bgs at boring locations AOI02-01 through 

AOI02-03. 

PFOA, PFHxS, PFNA, and PFBS were detected in soil at estimated concentrations less than 1 

μg/kg and were at least two orders of magnitude below their respective SLs in surface soil. PFOS 

was detected below the SL of 13 μg/kg at AOI02-01 and AOI02-03, with concentrations ranging 

from 0.138 J to 5.86 μg/kg, respectively.

PFHxS and PFBS were detected in shallow subsurface soil at estimated concentrations less than 

1 μg/kg and were at least four orders of magnitude below their respective SLs. PFOS was 

detected in shallow subsurface soil above 1 μg/kg but was almost two orders of magnitude below 

the respective SL at AOI02-03. PFOA and PFNA were not detected in shallow subsurface soil.

PFOS, PFHxS, and PFBS were detected in deep subsurface soil at estimated concentrations. 

PFOA and PFNA were not detected in deep subsurface soil.

• PFOS was detected at AOI02-02, with a concentration of 3.23 μg/kg. 

• PFHxS was detected at AOI02-02, with a concentration of 0.436 J μg/kg. 

• PFBS was detected at AOI02-02, with a concentration of 0.056 J μg/kg. 

6.4.2 AOI 2 Groundwater Analytical Results

Figure 6-6 and Figure 6-7 present the ranges of detections in groundwater. Table 6-5

summarizes the groundwater results.

Groundwater was sampled from temporary monitoring wells AOI2-01 through AOI2-03. Results 

are summarized below.
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MTA Camp Rilea, Warrenton, Oregon

AECOM 6-4

• PFOS was detected above the SL of 4 ng/L at AOI02-01, with a concentration of 32.9

ng/L. PFOS was detected at concentrations of 1.81 J ng/L or lower in the other two

wells.

• PFOA was detected below the SL of 6 ng/L at all three locations, with concentrations

ranging from 1.02 J ng/L to 3.93 ng/L.

• PFHxS was detected below the SL of 39 ng/L at all three locations, with concentrations

ranging from 1.38 J ng/L to 14.1 ng/L.

• PFNA was detected below the SL of 6 ng/L at AOI02-01, with a concentration of 1.10 J

ng/L.

• PFBS was detected below the SL of 601 ng/L at AOI02-01, with a concentration of 0.787

J ng/L.

6.4.3 AOI 2 Sediment Analytical Results 

Sediment was sampled at two locations (AOI02-04 and AOI02-05) within the two catch basins 

that surround Building 7156 storage area and general parking area. PFOA and PFNA were not 

detected in both sediment sample locations. Figure 6-8 through Figure 6-9 present the ranges 

of detections in sediment. Table 6-6 summarizes the sediment results. SLs are not available for 

sediment and these results are presented for informational purposes only.

• PFOS was detected in both sediment samples (including one duplicate sample) at

concentrations ranging from 0.301 J μg/kg to 0.584 J μg/kg.

• PFHxS was detected at AOI02-05 (including one duplicate sample) at concentrations

ranging of 0.093 J μg/kg and 0.132 J μg/kg.

• PFBS was detected at AOI02-05 (including one duplicate sample) at concentrations

ranging of 0.045 J μg/kg and 0.047 J μg/kg.

6.4.4 AOI 2 Conclusions

Based on the results of the SI, PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil 

below their respective SLs. PFOS was detected above the SL of 4 ng/L in groundwater at AOI02-

01. PFOS, PFHxS, and PFBS were detected in sediment at AOI 2. There are no established SLs

for sediment; therefore, these results are presented for informational purposes only. Based on the

exceedances of the SL in groundwater, further evaluation at AOI 2 is warranted.
Table 6-2

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil

Site Inspection Report, Camp Rilea

Analyte OSD Screening

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS 1900 ND U ND U ND U ND U ND U ND U 0.087 J

PFHxS 130 ND U ND U ND U ND U ND U ND U 0.736 J

PFNA 19 0.271 J ND U ND U ND U ND U 0.025 J ND U

PFOA 19 0.150 J ND U ND U ND U 0.090 J ND U 0.132 J

PFOS 13 0.313 J 0.117 J 0.075 J ND U 0.138 J ND U 5.86

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

DL detection limit

Notes ft feet

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. 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

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-0-2

01/18/2022

0-2 ft

AOI01-02-SB-0-2

01/18/2022

0-2 ft

AOI01-02-SB-0-2-D

01/18/2022

0-2 ft

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.

AOI01 AOI02

AOI02-02-SB-0-2

01/18/2022

0-2 ft

AOI02-03-SB-0-2

01/19/2022

0-2 ft

AOI01-03-SB-0-2

01/18/2022

0-2 ft

AOI02-01-SB-0-2

01/19/2022

0-2 ft

AECOM 6-5
Table 6-3

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Shallow Subsurface Soil

Site Inspection Report, Camp Rilea

Analyte OSD Screening

Level a

Result Qual Result Qual Result Qual Result Qual

PFBS 25000 ND U ND U ND U 0.063 J

PFHxS 1600 ND U ND U ND U 0.521 J

PFNA 250 0.103 J ND U ND U ND U

PFOA 250 0.146 J ND U ND U ND U

PFOS 160 0.102 J ND U ND U 3.82

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 DL detection limit

ft feet

Notes HQ hazard quotient

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. 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

Area of Interest

Sample ID

Sample Date

Depth

AOI01

AOI01-01-SB-4-5

01/18/2022

4-5 ft

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.

AOI02

AOI02-03-SB-13-15

01/19/2022

13-15 ft

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI02-01-SB-13-15

01/19/2022

13-15 ft

AOI02-02-SB-13-15

01/18/2022

13-15 ft

AECOM 6-6
Table 6-4

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Deep Subsurface Soil

Site Inspection Report, Camp Rilea

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual Result Qual

PFBS ND U ND U 0.056 J ND U

PFHxS ND U ND U 0.436 J ND U

PFNA ND U ND U ND U ND U

PFOA ND U ND U ND U ND U

PFOS ND U ND U 3.23 ND U

Interpreted Qualifiers Chemical Abbreviations

J = Estimated concentration PFBS perfluorobutanesulfonic acid

U = The analyte was not detected at a level greater than or equal to the adjusted DL PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

Notes PFOA perfluorooctanoic acid

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. PFOS perfluorooctanesulfonic acid

Acronyms and Abbreviations

AOI Area of Interest

D duplicate

DL detection limit

ft feet

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

μg/kg micrograms per kilogram

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI02

AOI02-02-SB-23.5-24.5

01/18/2022

23.5-24.5 ft

AOI02-03-SB-22-23

01/19/2022

22-23 ft

AOI02-01-SB-22-23

01/19/2022

22-23 ft

AOI02-01-SB-22-23-D

01/19/2022

22-23 ft

AECOM 6-7
Table 6-5

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Groundwater

Site Inspection Report, Camp Rilea

Analyte OSD Screening

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS 601 ND U ND U ND U ND U 0.787 J ND U ND U

PFHxS 39 1.86 J ND U ND U ND U 14.1 1.38 J 1.82 J

PFNA 6 ND U ND U ND U ND U 1.10 J ND U ND U

PFOA 6 7.66 1.14 J 1.29 J ND U 3.93 2.90 J 1.02 J

PFOS 4 ND U 3.13 J 2.61 J ND U 32.9 0.922 J 1.81 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

DL detection limit

Notes GW groundwater

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. 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

USEPA United States Environmental Protection Agency

ng/l nanogram per liter

Area of Interest

Sample ID

Sample Date

AOI01-01-GW

01/18/2022

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.

AOI01 AOI02

AOI02-02-GW

01/19/2022

AOI02-03-GW

01/19/2022

AOI01-04-GW

01/18/2022

AOI02-01-GW

01/19/2022

AOI01-02-GW

01/18/2022

AOI01-02-GW-D

01/18/2022

AECOM 6-8
Table 6-6

PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Sediment

Site Inspection Report, Camp Rilea

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual

PFBS ND U 0.045 J 0.047 J

PFHxS ND U 0.093 J 0.132 J

PFNA ND U ND U ND U

PFOA ND U ND U ND U

PFOS 0.506 J 0.301 J 0.584 J

Interpreted Qualifiers Chemical Abbreviations

J = Estimated concentration PFBS perfluorobutanesulfonic acid

U = The analyte was not detected at a level greater than or equal to the adjusted DL PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

Notes PFOA perfluorooctanoic acid

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. PFOS perfluorooctanesulfonic acid

Acronyms and Abbreviations

AOI Area of Interest

D duplicate

DL detection limit

ft feet

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

QSM Quality Systems Manual

Qual interpreted qualifier

SD sediment

μg/kg micrograms per kilogram

AOI02-05-SD-0-2-D

01/19/2022

0-2 ft

Sediment, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)

AOI02

AOI02-04-SD-0-2

01/19/2022

0-2 ft

AOI02-05-SD-0-2

01/19/2022

0-2 ft

AECOM 6-9
AECOM 6-10

THIS PAGE INTENTIONALLY BLANK

M 6-10
AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI02-03

AOI01-03

AOI01-01

AOI02-01

AOI02-02

AOI02-03

AOI02-01

AOI02-02

AOI02-03

Shallow Intermediate Deep

­ Figure 6-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

8/17/2022

8/17/2022

8/17/2022

MS

JH

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GIS BY

CHK BY

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Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/17/2022

1:4,800

Facility Boundary

Water Body

River/Stream

PFOA Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

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 6-11
AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI02-03

AOI01-03

AOI01-01

AOI02-01

AOI02-02

AOI02-03

AOI02-01

AOI02-02

AOI02-03

Shallow Intermediate Deep

­ Figure 6-2

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

8/11/2022

8/11/2022

8/11/2022

MS

JH

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GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

PFOS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

Exceedances of the OSD SL are depicted with a yellow halo.

Depth intervals shown represent respective sampling position within a given soil boring location.

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

AECOM 6-12
AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI02-03

AOI01-03

AOI01-01

AOI02-01

AOI02-02

AOI02-03

AOI02-01

AOI02-02

AOI02-03

Shallow Intermediate Deep

­ Figure 6-3

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

8/11/2022

8/11/2022

8/11/2022

MS

JH

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GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

PFBS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

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 6-13
AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI02-03

AOI01-03

AOI01-01

AOI02-01

AOI02-02

AOI02-03

AOI02-01

AOI02-02

AOI02-03

Shallow Intermediate Deep

­ Figure 6-4

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

8/11/2022

8/11/2022

8/11/2022

MS

JH

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GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

PFHxS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

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 6-14
AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI02-03

AOI01-03

AOI01-01

AOI02-01

AOI02-02

AOI02-03

AOI02-01

AOI02-02

AOI02-03

Shallow Intermediate Deep

­ Figure 6-5

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

8/11/2022

8/11/2022

8/11/2022

MS

JH

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GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/11/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

PFNA Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

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 6-15
AOI01-01

AOI01-02

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI01-01

AOI01-02

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI01-01

AOI01-02

AOI01-04

AOI02-01

AOI02-02

AOI02-03

PFOA PFOS PFBS

­ Figure 6-6

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

10/5/2022

10/5/2022

10/5/2022

MS

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GIS BY

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Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

10/5/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

Groundwater Flow Direction

PFOA, PFOS, and PFBS Detections in Groundwater

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

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

Exceedances of the OSD SL are depicted with a yellow halo.

AECOM 6-16
AOI01-01

AOI01-02

AOI01-04

AOI02-01

AOI02-02

AOI02-03

AOI01-01

AOI01-02

AOI01-04

AOI02-01

AOI02-02

AOI02-03

PFHxS PFNA

­ Figure 6-7

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

8/31/2022

8/31/2022

8/31/2022

MS

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Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

8/31/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

Groundwater Flow Direction

PFHxS, and PFNA Detections in Groundwater

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

PFHxS Results (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

Exceedances of the OSD SL are depicted with a yellow halo.

AECOM 6-17
Neacoxie Creek

Neacoxie Slough

AOI02-04

AOI02-05

Neacoxie Creek

Neacoxie Slough

AOI02-04 AOI02-05

Neacoxie Creek

Neacoxie Slough

AOI02-04 AOI02-05

PFOA PFOS PFBS

­ Figure 6-8

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

10/3/2022

10/3/2022

10/3/2022

MS

JH

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GIS BY

CHK BY

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Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

10/3/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

PFOA, PFOS, and PFBS Detections in Sediment

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

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 6-18
Neacoxie Creek

Neacoxie Slough

AOI02-04 AOI02-05

Neacoxie Creek

Neacoxie Slough

AOI02-04

AOI02-05

PFHxS PFNA

­ Figure 6-9

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Rilea, OR

10/3/2022

10/3/2022

10/3/2022

MS

JH

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GIS BY

CHK BY

PM

Base Map: Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

10/3/2022

1:4,800

Facility Boundary

Water Body

Wetland

River/Stream

PFHxS, and PFNA Detections in Sediment

12420 Milestone Center Drive

Germantown, MD 20876

0 200 400 800

Feet

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-19
6-20

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 7-1

7. Exposure Pathways

The CSMs for each AOI, revised based on the SI findings, are presented on Figure 7-1 and

Figure 7-2. 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 and AOI 2 based on the aforementioned 

criteria. 

7.1.1 AOI 1 

AOI 1 is the Former Fire Station – Building 7241, where controlled AFFF releases through 

washing firetrucks carrying AFFF, flushing out lines used for AFFF discharge at other locations, 

and storage of AFFF may have occurred potentially as early as 1970.
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 7-2

Relevant compounds were detected in surface and subsurface soil at AOI 1, at concentrations 

below the SLs. No ongoing construction was observed at the facility during the SI. Site workers 

and future construction workers could contact constituents in surface soil via incidental ingestion 

and inhalation of dust. Therefore, the surface soil exposure pathways for site workers and future 

construction workers are potentially complete. The facility is gated; however, residential structures 

are located approximately 0.3 miles to the east of AOI 1. Therefore, the incidental ingestion and 

inhalation of dust exposure pathways for the off-facility residential, recreational user, and 

trespasser receptors are considered potentially complete.

The construction worker exposure scenario assumes excavation occurs at depths at or above 15 

feet bgs. Therefore, the subsurface soil exposure pathway for future construction workers is 

potentially complete. The CSM for AOI 1 is presented on Figure 7-1. 

7.1.2 AOI 2

AOI 2 is the UTES Former Firetruck Parking area surrounding Building 7156 in the central/eastern 

portion of the facility. Two firetrucks with tank capacities of approximately 50 gallons each

reportedly contained AFFF and were present at the facility from 1989 until an unknown period of 

time. AFFF from the former firetrucks was reportedly never deployed at the facility. OMD 

maintenance personnel performed minor repairs and maintenance of the former firetrucks at the 

UTES.

Relevant compounds were detected in surface and subsurface soil at AOI 2, at concentrations 

below the SLs. No ongoing construction was observed at the facility during the SI. Site workers 

and future construction workers could contact constituents in surface soil via incidental ingestion 

and inhalation of dust. Therefore, the surface soil exposure pathways for site workers and future 

construction workers are potentially complete. The facility is gated; however, residential structures 

are located approximately 600 feet to the east of AOI 2. Therefore, the incidental ingestion and 

inhalation of dust exposure pathways for the off-facility residential, recreational user, and 

trespasser receptors are considered potentially complete.

Construction workers could contact constituents in subsurface soil via incidental ingestion. 

Therefore, the subsurface soil exposure pathway for future construction workers is potentially 

complete. The CSM for AOI 2 is presented on Figure 7-2. 

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. Drinking 

water at the facility is supplied by two onsite water supply wells. Public groundwater systems are 

used for drinking water sources on properties surrounding the facility, including the Sunset Lake 

RV Park (located approximately 0.5 miles to the south) and the City of Warrenton (located less 

than 1 mile to the north). 

7.2.1 AOI 1

Relevant compounds were in groundwater detected at AOI 1; PFOA was detected above the SL. 

The onsite water supply wells are located in the central/western portion of the facility, northwest 

of AOI 1, and are not interpreted to be downgradient from the Former Fire Station. Additionally, 

the public groundwater system drinking water sources are not hydraulically downgradient from 

AOI 1. Therefore, the groundwater exposure pathway via ingestion is considered incomplete for 

off-facility residents, recreational users, and trespassers. Additionally, the site worker ingestion 

exposure pathway via drinking water receptors is considered incomplete; however, incidental 

ingestion may occur via shallow groundwater contact, as discussed in the paragraph below.
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 7-3

Active construction was not observed at the facility during the SI. Depths to water measured at 

AOI 1 during the SI in January 2022 ranged from 1.90 to 6.30 feet bgs. The construction worker 

exposure scenario assumes excavation occurs at depths at or above 15 feet bgs. Therefore, the 

incidental ingestion exposure pathway for future construction workers, as well as site workers, is 

considered potentially complete. The CSM for AOI 1 is presented on Figure 7-1. 

7.2.2 AOI 2

PFOS was detected above the SL in groundwater at AOI 2. The onsite water supply wells located 

in the central/western portion of the facility and to the west and downgradient of AOI 2; therefore, 

the groundwater exposure pathway via ingestion is considered potentially complete for site 

workers. The public groundwater system drinking water sources were not observed to be

hydraulically downgradient from AOI 2 during the SI. Therefore, the groundwater exposure 

pathway via ingestion is considered incomplete for off-facility recreational users and residents. 

Depths to water measured at AOI 2 in January 2022 during the SI ranged from 21.14 to 23.05

feet bgs. Therefore, the incidental ingestion exposure pathway for future construction workers is 

considered incomplete. There is no current active construction at the facility. The CSM for AOI 2 

is presented on Figure 7-2. 

7.3 Surface Water and Sediment Exposure Pathway

The SI results in sediment were used to determine whether a potentially complete pathway exists 

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

AOIs where sediment samples were not collected, 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

PFAS are water soluble and can migrate readily from soil to surface water via leaching and runoff. Surface water and sediment samples were not collected at AOI 1; however, relevant 

compounds were detected in soil and groundwater at AOI 1. It is possible that these compounds 

may have migrated from soil and shallow groundwater to the nearby Neacoxie Creek to the eastsoutheast of the facility. Due to potential recreational use of the nearby Neacoxie Creek, the 

surface water and sediment ingestion exposure pathways for off-facility recreational users are

considered potentially complete. Surface water is not used as drinking water in the vicinity, so the 

surface water ingestion pathway for residential receptors is incomplete.

An onsite wastewater treatment system with two sewage lagoons is located to the southeast of 

AOI 1. As a result, the ingestion pathway for surface water and sediment is potentially complete 

for future construction workers during ground disturbing activities and trespassers. Facility 

workers are unlikely to access the sewage lagoons; therefore, the ingestion exposure pathway 

for site workers is considered incomplete. The CSM for AOI 1 is presented on Figure 7-1.

7.3.2 AOI 2

Relevant compounds were detected in sediment samples collected from within the two catch 

basins that surround Building 7156 storage area and general parking area. Surface water samples 

were not collected, however PFAS are water soluble and may have been leached from the 

sediment into the surface water. The closest surface water body is the Neacoxie Slough located 

approximately 200 feet to the west of AOI 2. Due to potential recreational use of the Neacoxie 

Slough that flows to the north, the surface water and sediment ingestion exposure pathway for 

off-facility recreational users is considered potentially complete. The ingestion of surface water 
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 7-4

exposure pathways for the off-facility residential receptors are considered incomplete for the same 

reasons established for AOI 1.

Based on the SI results, the ingestion pathway for surface water and sediment is potentially 

complete for future construction workers during ground disturbing activities and trespassers. 

Facility workers are unlikely to access the catch basins; therefore, the ingestion exposure pathway 

for site workers is considered incomplete. The CSM for AOI 2 is presented on Figure 7-2. 
Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

LEGEND

Figure 7-1

Conceptual Site Model, AOI 1

Camp Rilea, Warrenton, Oregon

1. The resident and recreational users refer to offsite receptors.

2. Construction was not observed during SI field

activities.

NOTES

Media

SOURCE PATHWAY RECEPTOR

AOI 1

Firetruck

Washing, Line

Flushing,

AFFF Storage

Subsurface

Soil

Human

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne Soil

Particulate

Surface Soil

Surface

Water/

Sediment

Subsurface

Soil

Shallow

Groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

Dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Surface

Water

Surface

Water Flow

Surface Soil

/ / / /

Site

Worker

Construction 

Worker2

Resident1

Recreational 

User/Trespasser1

Site 

Worker

Construction 

Worker2 Resident1

/ / / /

Recreational 

User/Trespasser1

Potential

Off-Facility

Source Not

Under

Control of

ARNG

/ / / /

/ / / /

/ / / /

AECOM 7-5
Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

LEGEND

Figure 7-2

Conceptual Site Model, AOI 2

Camp Rilea, Warrenton, Oregon

1. The resident and recreational users refer to offsite receptors.

2. Construction was not observed during SI field

activities.

NOTES

Media

SOURCE PATHWAY RECEPTOR

AOI 2

AFFF Storage

in Firetrucks

Subsurface

Soil

Human

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne Soil

Particulate

Surface Soil

Surface

Water/

Sediment

Subsurface

Soil

Shallow

Groundwater

Source

Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

Dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Surface

Water

Surface

Water Flow

Surface Soil

/ / / /

Site

Worker

Construction 

Worker2

Resident1

Recreational 

User/Trespasser1

Site 

Worker

Construction 

Worker2 Resident1

/ / / /

Recreational 

User/Trespasser1

Potential

Off-Facility

Source Not

Under

Control of

ARNG

/ / / /

/ / / /

/ / / /

AECOM 7-6
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

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 11, 12, and 18 to 19 January 2022 and consisted of 

utility clearance, direct push boring, soil sample collection, temporary monitoring well installation, 

grab groundwater sample collection, sediment sample collection, and land surveying. Field activities 

were conducted in accordance with the SI QAPP Addendum (AECOM, 2021a).

To fulfill the project DQOs set forth in the approved SI QAPP Addendum (AECOM, 2021a), 

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. 

• Thirteen (13) soil samples from six boring locations; 

• Six grab groundwater samples from six temporary wells; 

• Two sediment samples from two locations;

• Thirteen (13) 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 is warranted in an RI for AOI 1: Former Fire 

Station – Building 7241 and AOI 2: UTES: Former Firetruck Parking – Building 7156. Based on 

the CSMs developed and revised in light of the SI findings, there is potential for exposure to 

receptors from AOI 1 and AOI 2 from sources on the facility resulting from historical DoD activities.

Sample analytical concentrations collected during the SI were compared to 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:

• The detected concentrations of PFOA, PFOS, PFBS, PFHxS, and PFNA in soil at 

AOI 1 were below respective SLs. 

• PFOA in groundwater exceeded the 6 ng/L SL at one of the three well locations, 

AOI01-01, at a concentration of 7.66 ng/L. The remaining detected relevant 

compound concentrations were below the SLs.

• Based on the results of the SI, further evaluation of AOI 1 is warranted in an RI.
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MTA Camp Rilea, Warrenton, Oregon

AECOM 8-2

• At AOI 2: 

• The detected concentrations of PFOA, PFOS, PFBS, PFHxS, and PFNA in soil at 

AOI 2 were below their SLs. 

• PFOS in groundwater exceeded the 4 ng/L SL at one of the three well locations, 

AOI02-01, at a concentration of 32.9 ng/L. The remaining detected relevant 

compound concentrations were below the SLs. 

• PFOS, PFHxS, and PFBS were detected in sediment at AOI 2. There are no 

established SLs for sediment, and the results are presented for informational 

purposes only. 

• Based on the results of the SI, further evaluation of AOI 2 is warranted in an RI.

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. 

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

AOI Potential 

Release Area

Soil –

Source Area

Groundwater –

Source Area Future Action

1 Former Fire Station – 

Building 7241 Proceed to RI 

2 UTES: Former Firetruck 

Parking – Building 7156 Proceed to RI

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels
Site Inspection Report

MTA Camp Rilea, Warrenton, Oregon

AECOM 9-1

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MTA Camp Rilea, Warrenton, Oregon

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