FINAL

Site Inspection Report 

Army Aviation Support Facility #2

Pendleton, 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

September 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 ........................................................................................................ 2-1

2.2.2 Hydrogeology ............................................................................................... 2-3

2.2.3 Hydrology ..................................................................................................... 2-5

2.2.4 Climate ......................................................................................................... 2-6

2.2.5 Current and Future Land Use....................................................................... 2-6

2.2.6 Sensitive Habitat and Threatened/ Endangered Species............................. 2-7

2.3 History of PFAS Use ............................................................................................... 2-7

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

3.1 AOI 1 Eastern Detention Basin............................................................................... 3-1

3.2 AOI 2 Ramp Area.................................................................................................... 3-1

3.3 AOI 3 Readiness Center......................................................................................... 3-1

3.4 Adjacent Sources.................................................................................................... 3-2

3.4.1 Eastern Oregon Regional Airport.................................................................. 3-2

3.4.2 City of Pendleton Fire Department ............................................................... 3-2

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 ..................................................................................... 4-1

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

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

5.1.1 Technical Project Planning ........................................................................... 5-2

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............................................................................... 5-3

5.3 Temporary Well Installation and Groundwater Grab Sampling ............................... 5-4

5.4 Permanent Well Installation and Groundwater Sampling ....................................... 5-4

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

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

5.7 Investigation-Derived Waste ................................................................................... 5-6

5.8 Laboratory Analytical Methods................................................................................ 5-6

5.9 Deviations from SI QAPP Addendum ..................................................................... 5-6

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
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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

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

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

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

6.5 AOI 3....................................................................................................................... 6-4

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

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

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

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

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

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

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

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

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

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

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

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

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

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

7.3.2 AOI 2 ............................................................................................................ 7-4

7.3.3 AOI 3 ............................................................................................................ 7-4

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

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

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

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

Appendix A Data Usability Assessment and Validation Reports

Appendix B Field Documentation

B1. Log of Daily Notice of Field Activities

B2. Sampling Forms

B3. Survey Data

Appendix C Photographic Log

Appendix D TPP Meeting Minutes

Appendix E Boring Logs 

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, December 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 7-1 Conceptual Site Model, AOI 1

Figure 7-2 Conceptual Site Model, AOI 2

Figure 7-3 Conceptual Site Model, AOI 3

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 and Permanent Well Screen Intervals

Table 5-3 Temporary and Permanent Monitoring Well Screen Intervals and 

Groundwater Elevations

Table 6-1 Screening Levels (Soil and Groundwater)

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

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

Table 6-4 PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Groundwater

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

% percent

°C degrees Celsius

°F degrees Fahrenheit

μg/kg micrograms per kilogram

AASF Army Aviation Support Facility

AECOM AECOM Technical Services, Inc.

AFFF aqueous film-forming foam

amsl above mean sea level

AOI Area of Interest

ARNG Army National Guard

ASR Aquifer Storage and Recovery

bgs below ground surface 

cfs cubic feet per second

CRBG Columbia River Basalt Group

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

DO dissolved oxygen

DOT Department of Transportation

DQO data quality objective

DUA data usability assessment

EDRTM Environmental Data Resources, Inc.TM

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

FedEx Federal Express

GPRS 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

MIL-SPEC military specification

MS/MSD matrix spike/ matrix spike duplicate

NELAP National Environmental Laboratory Accreditation Program

ng/L nanograms per liter

OMD Oregon Military Department

ORARNG Oregon Army National Guard

ORDEQ Oregon Department of Environmental Quality

ORP oxidation-reduction potential

OSD Office of the Secretary of Defense

OWRD Oregon Water Resources Department
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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

RI Remedial Investigation

SI Site Inspection

SL screening level

SOP standard operating procedure

TOC total organic carbon

TPP Technical Project Planning

TSi Terra Sonic

UFP Uniform Federal Policy

US United States

USACE United States Army Corps of Engineers

USCS Unified Soil Classification System

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

USGS United States Geological Survey
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Executive Summary

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

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

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

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

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

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

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

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

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

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

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

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

AOIs identified in the PA and determine whether further investigation is warranted, a removal 

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

relevant compounds. This SI was completed at the Pendleton Army Aviation Support Facility 

(AASF #2) in Pendleton, Oregon and determined further evaluation under the Comprehensive 

Environmental Response, Compensation, and Liability Act (CERCLA) is warranted for AOI 1, 

AOI 2, and AOI 3. Pendleton AASF #2 will also be referred to as the “facility” throughout this 

document. 

Pendleton AASF #2 is located at 2100 NW 56th Street, adjacent to the Eastern Oregon Regional 

Airport, in Umatilla County, in Pendleton, Umatilla County, Oregon. The Pendleton AASF #2 is 

home to the 1st Battalion, 168th Aviation Regiment, Task Force Long Knife, 40th Combat 

Aviation Brigade, which operates rotary-winged aircraft such as helicopters and unmanned 

aerial vehicles for the ORARNG. Operations at the Pendleton AASF #2 include aviation safety 

training, controls utilization, and maintenance, modification, and repair of rotary-winged aircraft. 

In addition to AASF #2, Pendleton has a readiness center for training exercises, natural disaster 

relief, or combat, a helicopter parking ramp, training area, one aircraft wash rack, and one 

ground vehicle wash rack. 

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

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

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

Investigation (RI) for AOI 1, AOI 2, and AOI 3. 

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 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 ES-2: Summary of Site Inspection Findings and Recommendations

AOI Potential 

Release Area

Soil – 

Source Area

Groundwater – 

Source Area

Groundwater –

Facility 

Boundary

Future Action

1 Eastern 

Detention Basin Proceed to RI 

2 Ramp Area Proceed to RI

3 Readiness 

Center N/A Proceed to RI

Legend:

N/A = not applicable

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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1. Introduction

1.1 Project Authorization 

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

Assessments (PAs) and Site Inspections (SIs) on the current or potential historical use of perand 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 Pendleton Army Aviation Support Facility (AASF) #2 in Pendleton, Oregon. Pendleton AASF 

#2 is also referred to as the “facility” throughout this document. 

The SI project elements were performed in compliance with Comprehensive Environmental 

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

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

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

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

investigations. 

1.2 SI Purpose

A PA was performed at Pendleton AASF #2 (AECOM Technical Services, Inc. [AECOM], 2020) 

that identified three 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 

Pendleton AASF #2 is located at 2100 NW 56th Street, adjacent to the Eastern Oregon Regional 

Airport in Pendleton, Umatilla County, Oregon. Pendleton AASF #2 is on the northwestern city 

limits of Pendleton, directly west of the airport and north of Interstate Highway 84 (Figure 2-1). 

The southern communities of Rieth and Green Meadows, and the eastern communities of 

Riverside, Gopher Flats, Mission, and Tutuilla, lie within 10 miles of the facility. 

The Oregon ARNG (ORARNG), by and through the Oregon Military Department (OMD), entered 

a lease with the City of Pendleton in 1987 for the use and occupancy of 14.38 acres of land 

adjacent to the Eastern Oregon Regional Airport. In 1995, the lease was amended to grant the 

ORARNG permission to build AASF #2 by July 1999. The amended lease included the addition 

of 9.21 acres, with the facility currently totaling 23.59 acres. The Pendleton AASF #2 was 

constructed between 1996 and 1999, approximately 550 feet south of Runway 7/25. The

amended lease may be renewed up to a period of 62 years from the original term, with an 

expiration date of 2049.

The Pendleton AASF #2 is home to the 1st Battalion, 168th Aviation Regiment, Task Force Long 

Knife, 40th Combat Aviation Brigade, which operates rotary-winged aircraft such as helicopters 

and unmanned aerial vehicles for the ORARNG. Operations at the Pendleton AASF #2 include 

aviation safety training, controls utilization, and maintenance, modification, and repair of rotarywinged aircraft. In addition to AASF #2, Pendleton has a readiness center for training exercises, 

natural disaster relief, or combat, a helicopter parking ramp, training area, one aircraft wash 

rack, and one ground vehicle wash rack. The Pendleton AASF #2 facility is closed to the public 

and secured with a 6-foot chain-link fence topped with barbed wire. The security gate is guarded 

while the facility is open and locked when the facility is closed (Dudek, 2018). 

2.2 Facility Environmental Setting

The facility is within the Umatilla River Basin in northeastern Oregon, along the south-central 

edge of the Columbia Plateau, which extends north into Washington State. The Oregon portion 

of the plateau is made up entirely of lowlands that extend from the western Cascade Mountains 

to the southeastern Blue Mountains. The topography around the facility is varied, with flat to 

gently sloping lowlands and terraces along the Umatilla River that transition to steeper slopes 

on the hills to the north and south. The approximate center of the facility is located at 1,490 feet 

above mean sea level (amsl). The urbanized City of Pendleton is a center of grain, vegetable 

production, and ranching, and it sits roughly 1,200 feet amsl (City of Pendleton, 2023). 

Much of the facility is paved with either asphalt or concrete, with some small unpaved grassy 

areas along the eastern boundary of the facility. The land around the facility is relatively 

undeveloped, nonresidential land, except for the Pendair Heights Industrial Park located 

immediately south of the airport (Dudek, 2018). The zoning designations for the immediate and 

surrounding area are largely classified as airport activities and light industrial (Alford, 2015).

Interstate 84 passes near the facility, to the south and east of the downtown area. 

2.2.1 Geology

The facility is in the south-central portion of the Columbia Plateau physiographic province. The 

plateau is a structural basin that drains to the Columbia River through its major tributaries: the 

Snake, Yakima, John Day, Umatilla, Spokane, Klickitat, and Deschutes Rivers. The portion of 

the Columbia Plateau in Oregon is formally known as the Deschutes-Umatilla Plateau, or the 
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Columbia-Deschutes Plateau. The basalt plateau dips gently north-northwest and ranges from 

3,000 feet amsl near the base of the Blue Mountains to less than 300 feet amsl near the 

Columbia River (Gonthier, 1990). The Deschutes-Umatilla Plateau axis extends laterally eastwest and is bound in the north by the Columbia River and to the south by the Blue Mountain 

Anticline. The Columbia Plateau is comprised of basaltic lavas that extruded during the 

Miocene. The large flood basalts are formally named the Columbia River Basalt Group (CRBG) 

and underlay parts of Oregon, Washington, and Idaho. The rock group is made up of five major 

basalt flows, including the Steens Basalt, Imnaha Basalt, Grande Ronde Basalt, Wanapum 

Basalt, and Saddle Mountains Basalt.

Northwest-trending fissure volcanic eruptions during the late Miocene and early Pliocene 

produced the series of wide-spread flood basalts that engulfed the Pacific Northwest. The flood 

basalts flows were regionally confined to the north by the Okanogan Highlands, to the east by 

the Rocky Mountains, and to the west by the Cascade Mountains. The southern margin of the 

flood basalt’s boundaries is not distinctive, and flows diminish in thickness from the source 

fissures. The thickness of the CRBG varies widely, with the maximum thickness over 14,000 

feet, near Pasco, Washington, and the average thickness of approximately 3,300 feet. Individual 

flows of the subgroups of the CRBG are typically 30 to 50 feet thick but can range from several 

inches to hundreds of feet. Basalt thicknesses are influenced by the existing topographical 

setting during the eruptions, with thick flows in the existing depressions and thinner where flows 

butted against higher elevations (Gonthier, 1985).

Few sedimentary interbeds are present between select individual basalt flows. Sedimentary 

interbeds of clay, silt, sand, and occasional gravel were deposited in the Miocene epoch, 

between active eruptions. Where present, these interbeds are used to distinguish between the 

discrete flows. The combination of these sedimentary interbeds is referred to as the Ellensburg 

Formation (Gonthier, 1990).

The majority of the CRBG is dominated by the Yakima Basalt Subgroup consisting of the 

Grande Ronde Basalt, the Wanapum Basalt, and the Saddle Mountains Basalt. The Grande 

Ronde Basalt, underlying a large extent of the Columbia Plateau, is comprised of 131 individual 

flows with varying thicknesses. The Grande Ronde Basalt accounts for up to 85 percent (%) of 

the total volume of the CRBG. Sedimentary interbeds between these flows generally range from 

non-existent to several feet thick and are limited in lateral extent, indicating the relatively short 

lag times between eruptions. The upper extent of the Grande Ronde Basalt is difficult to 

distinguish from the overlying Wanapum Basalt, and where present, a weathering zone and/or 

the Wanapum-Grande Ronde can be used to identify the contact between the igneous units 

(Gonthier, 1990). The interbed is comprised of primarily claystone and siltstone and varies from 

non-existent to 100 feet thick; however, the thickness averages around 25 feet. These interbeds 

are formally known as Vantage Member of the Ellensberg Formation in the regional area of the 

facility.

The Wanapum Basalt superimposes the Grande Ronde Basalt, and where present, the 

weathering zone/sedimentary interbeds locally around the facility. Wanapum Basalt is 

composed of approximately 33 individual flows, with more prevalent sedimentary interbeds than 

the underlying Grande Ronde Basalt. Sedimentary interbeds within the Wanapum Basalt are 

typically thin and limited in spatial distribution, varying from 0 to 100 feet. The Wanapum is 

exposed at the surface to the north of the facility in the Missouri, Despain, and Stage Gulches. 

To the south of the facility, Wanapum Basalt is exposed along the Umatilla River Valley and its 

tributaries.

Due to the lithostatic load of these flood basalts, the crust beneath began to subside, producing 

the large, slightly depressed lava plain of the Columbia Plateau, which encompasses more than 

63,000 square miles (Winterbrook Planning, 2012). North-south horizontal tectonic stresses 
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generated regional uplifting known as the Blue Mountains. The northern margin of the Blue 

Mountains near the City of Pendleton consists of a series of northeast-trending, faulted 

monoclines and associated anticlines and synclines (Walker, 1990).

Alluvium deposits from the Umatilla River and its tributaries covers the basalt throughout the 

lowland floodplains (Winterbrook, 2012). Additionally, wind-blown loess deposits are present 

overlying the basalt at the facility and its vicinity. These aeolian deposits are characterized as 

clayey silt and fine sand, with local interbeds of soil, caliche, and some water-laid silt and gravel, 

and range from Pleistocene to Holocene in age (Walker, 1973; Walker, 1977). Based on a 

review of available boring logs, loess deposits within the vicinity of the facility range in thickness 

from approximately 12 feet to 23 feet (Oregon Water Resources Department [OWRD], 2023). 

The soils in the Pendleton area are characterized by well-drained silt loams of the Anderly, Pilot 

Rock, and Walla Walla series. A majority of these soils are found in depressions on the 

floodplains (Winterbrook, 2012).

During the SI, borings were completed to depths ranging between 20 to 33 feet below ground 

surface (bgs). Soils observed generally consisted of dry silts with varying quantities of sand and 

gravel. Weathered and broken basalt bedrock was observed as shallow as 3.5 feet bgs, and 

strong, intact basalt was observed as shallow as 12 feet bgs. Based on surveyed elevation data 

collected at the permanent well locations, the basalt bedrock surface was measured at higher 

elevations in the southwest and decreased in elevation toward the northeast (Figure 2-4). The 

basalt was generally observed to be aphanitic and variably oxidized. Water-bearing vesicles 

were observed in basalt in borings within AOI 2 and AOI 3 from 15 to 33 feet bgs. Small 

quantities of clay were observed within fractures at AOI02-02 and AOI03-01, at depths ranging 

between 26 to 33 feet bgs. The clay appears to be a byproduct of water weathering the parent 

basalt rock. 

The observed silts consist of a mixture of fill and loess, and the basalt encountered appears 

consistent with the mapped Wanapum Basalt underneath the facility. Boring logs are presented 

in Appendix E. 

2.2.2 Hydrogeology

The Columbia Plateau Basaltic Aquifer system is a large regional groundwater resource that 

occupies approximately 50,600 square miles and extends across a small part of northern Idaho, 

northeastern Oregon, and a large part of southeastern Washington. The aquifer system is the 

primary source of groundwater for municipal, industrial, and irrigation uses. The alluvial and 

shallow basalt aquifers provide the main source of domestic water for rural residents, with 

depths to groundwater ranging from approximately 5 to 25 feet bgs in the alluvial aquifer and 50 

to 340 feet bgs in the basalt aquifers (Hogenson, 1964). The CRBG contains permeable 

aquifers separated by less permeable confining units. The productive aquifers typically consist 

of interflow zones separated by low permeability flow interiors (US Geological Survey [USGS], 

2016). While interflow zones generally yield large volumes of water initially, continued 

withdrawals result in large declines in water level due to low storage properties and slow aquifer 

recharge.

The Columbia Plateau Basaltic Aquifer System is a layered series of fractured basalt formations 

of the CRBG, separated by confining units of sedimentary interbeds and unconsolidated 

deposits of loose silt, sand, and occasionally gravel, all underlain by pre-Miocene sedimentary 

rocks (Whitehead, 1994). Over 300 individual flows have been identified within the Columbia 

Plateau (USGS, 2016). The top and bottom of individual flows within the CRBG, which is an 

important source of water supply in the Umatilla Basin, are vesicular, brecciated, and 

permeable.
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Alluvial sand and gravel deposits are found in the lower basin between Boardman and Cold 

Springs Reservoir and within the flood plains of major streams. Groundwater in the shallow 

depths of the alluvial aquifer is unconfined and generally has a strong hydraulic connection with 

surface water, with most recharge in this aquifer being supplied by leaky canals and ditches, as 

well as applied irrigation water (USGS, 2016). However, recharge from precipitation is a 

relatively small proportion of total recharge, given the low yearly average rainfall the City of 

Pendleton receives. Groundwater below the alluvial aquifer occurs in a series of basalt aquifers: 

the Wanapum Basalt, a confining unit, Grand Ronde Basalt, and then pre-Miocene rocks. Based 

on available information, the regional alluvial aquifer was not expected to be present at the 

facility. 

Regional groundwater flow in the CRBG is generally from upland areas in the southeast and 

north, towards the Umatilla River. However, the facility is near a groundwater divide. Also, a 

regional-scale anticline extending east-northeast/west-southwest is mapped within the northern 

vicinity of the facility, identified as the “Rieth Anticline” (Walker, 1977; USGS, 2002; USGS, 

2017), and a south-southeast-dipping normal fault is locally mapped extending approximately 

along-strike of the anticline (McConnell, 2006). Based on these factors, groundwater flow 

direction in the CRBG may differ within the vicinity of the facility. 

Public drinking water for the City of Pendleton is managed by an Aquifer Storage and Recovery 

(ASR) Program (further discussed in Section 2.2.3). Although the degree of uncertainty of their 

reported geographical locations is up to 1-mile, several private drinking water wells, irrigation 

wells, and other wells are reported within a 4-mile radius of the facility, and several are 

discussed below (OWRD, 2023): 

• One privately-owned domestic well located less than 0.5 miles to the north (well report

5603). First encountered water was noted at 72 feet bgs, and static water level is noted

at 21 feet bgs. The well appears to be down-gradient of the facility; however, the well is

proximal to the hanging wall of the mapped normal fault, which may affect localized

groundwater flow directions.

• One privately-owned domestic well located approximately 1.75 miles to the northwest

(well report 1381). First encountered water was noted at 483 feet bgs.

• One privately-owned domestic well located approximately 0.75 miles to the southwest

(well report 537). First encountered water was noted at 365 feet bgs, but the well is

downhill and at a different elevation from the facility.

• One privately-owned domestic well located approximately 1.35 miles to the east (well

report 1406). Groundwater was not initially encountered in the depth drilled to 595 feet

bgs, although static level was noted at 370 feet bgs.

• More than 10 additional wells within 2 miles to the north, south, and east.

Based on these available well logs, depth to groundwater in the CRBG within the vicinity of the 

facility is variable but may be first encountered as shallow as 72 feet bgs and as deep as 

greater than 595 feet bgs. However, perched groundwater may also be present within the 

overlying loess within the vicinity of the facility. If encountered, this perched groundwater may be 

discontinuous, but flow is expected to follow surface topography towards the northeast. 

A Rieth Water District public drinking water well is located 2 miles to the south-southwest of the 

facility (well report UMAT55330). The well was completed in 1942 at 287 feet bgs and static 

groundwater was reported 65 feet bgs (Oregon Health Authority, 2023). 
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Depths to water measured in December 2022 during the SI ranged from 15.81 to 23.87 feet 

bgs. Groundwater elevations were generally measured higher in the southwest and decreased 

toward the northeast. Based on lithologic observations during drilling and measured elevations, 

groundwater appears to flow primarily to the northeast through fractures and vesicles within the 

basalt bedrock. The groundwater flow direction appears to generally follow the direction of 

bedrock dip (discussed in Section 2.2.1). 

However, groundwater flow direction may also be seasonally impacted by nearby agricultural 

activities. Additionally, groundwater flow conditions were assessed within shallow basalt 

underlying the facility. Groundwater within deeper basalt and interbedded sedimentary layers 

may exhibit alternative flow paths. Depth to water-bearing basalt rock may also differ outside of 

the facility boundary due to the incongruent depositional nature of basalt lava. Groundwater and 

bedrock surface elevation contours from the SI are presented on Figure 2-4. 

2.2.3 Hydrology

The facility is in the central part of the Umatilla River basin, approximately 50 river miles 

southeast of the confluence with the Columbia River and about 30 miles from its headwaters in 

the Blue Mountains to the east. The City of Pendleton is developed along the Umatilla River and 

on the adjacent hills to the north and south. Multiple intermittent and perennial streams draining 

to the Umatilla River are present on the hills. 

The facility lies within the southern portion of the Upper Stage Gulch Watershed, with portions of 

the nearby Eastern Oregon Regional Airport located in the northern region of the Cottonwood 

Creek-Umatilla River Watershed (Figure 2-5). The Umatilla River is the nearest surface water 

body, located approximately 1.5 miles south of the facility; the most recent Spill Prevention, 

Control, and Countermeasure Plan for the facility identified associated activities as having the 

potential to impact the Umatilla River (Dudek, 2018). To the north and south of Pendleton AASF 

#2, several mapped freshwater emergent wetlands and drainage swales function as unnamed 

tributaries to the Umatilla and Columbia Rivers. The facility is located adjacent to a surface 

water divide. Generally, surface water flow direction within, around, and to the north of the 

facility is to the northeast. Immediately south of the facility, in the Cottonwood Creek-Umatilla 

River Watershed, surface water flow is to the south and southeast, towards the nearby Umatilla 

River.

Due to a minimal annual rainfall, areas of ponding or standing water were not noted within or 

around the facility, and no known wetlands exist within the vicinity of the facility. However, two 

unlined stormwater detention basins are located to the east and northwest of the aircraft parking 

ramp and receive most surface water runoff from catch basins and trench drains located 

throughout the facility (Dudek, 2018). Both detention basins allow surface water runoff and 

stormwater to gradually infiltrate into the ground. During high volume events, overflow drains in 

these basins help carry excess volume to the adjacent Eastern Oregon Regional Airport 

stormwater system (Dudek, 2018). The eastern detention basin is within the boundary of AOI 1, 

and the northern detention basin is northwest of AOI 2.

Prior to 2003, drinking water for the City of Pendleton was supplied mostly through a series of 

deep basalt wells throughout and near the city. Starting in 2003, the City of Pendleton began an 

ASR Program, which consists of five ASR wells, surface water intakes at the Umatilla River, and 

the Pendleton Water Filtration Plant. Surface water is pumped from Umatilla River to the Water 

Filtration Plant in the winter/spring when flow is greater than 250 cubic feet per second (cfs). In 

the summer/fall, when Umatilla River flow is below 250 cfs, source water is pumped from the 

aquifer into Umatilla River. All water is filtered via membrane ultra-filtration prior to distribution. 

Additionally, in the winter/spring, excess filtered water is pumped into the aquifer. An average of 
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Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 2-6

800 million gallons of water per year are deposited and stored in the aquifer (City of Pendleton, 

2021). 

The shift in reliance to surface water has helped to reduce declines in groundwater aquifer 

storage volumes that were occurring prior to the construction of the Water Filtration Plant. 

Drinking water that has already been treated through the Water Filtration Plant is stored in the 

underground basalt aquifer system beneath the city. This treated water is stored during the 

winter months, when there is greater volume in the Umatilla River, and it is recovered during the 

summer months when the demand is higher, a process known as ASR (City of Pendleton, 

2021). Three ASR wells are located in the City of Pendleton, with Well #14 ASR, the closest one 

to the facility, depicted on Figure 2-4. Approximately 1.9 million meters cubed of treated surface 

water are collectively injected into the permeable interflow zones of these underground aquifers 

from January to June, at depths between 60 and 150 meters (Bonneville et al., 2015). 

2.2.4 Climate

The facility lies within a semi-arid low humidity climate. Air temperatures are regulated 

throughout the year by the Pacific Ocean. During the summer months, air from the Pacific is 

often stalled by high-pressure systems to the north or east, causing temperatures to rise. The 

resulting dry and hot southerly air allows for increased risk of wildfires in the region surrounding 

the facility. Wind in the area tends to be channeled along the Umatilla River valley, in 

conjunction with a prevailing westerly wind direction in the area, resulting in a prevailing westsouthwest wind (US Climate Data, 2018).

Average annual precipitation is 12.83 inches, with the majority of rainfall between October 

through June. Snowfall occurs between October to March, with an annual average of 15.7 

inches. The highest temperatures occur in July, at a mean maximum of 89.2 degrees Fahrenheit 

(°F). The lowest temperatures occur in January, with a mean minimum of 28.0 °F (National 

Oceanic and Atmospheric Administration, 1991-2020). 

2.2.5 Current and Future Land Use

Pendleton AASF #2 encompasses 23.59 acres of land, on the northwestern city limits of 

Pendleton, Oregon. The facility is bound to the north and east by Eastern Oregon Regional 

Airport, to the west by farmland and the Pendleton National Weather Service, and to the south 

by various aviation facilities. A commercial and industrial park is located to the south of the 

aviation facilities, and a hiking area is located 0.25 miles to the southwest. A hotel is located 

approximately 0.5 miles to the southeast of the facility. Residential structures within a 1-mile 

radius of the facility include dispersed residential structures located to the south, east, and west. 

The closest residential structure is approximately 0.5-miles south of the facility.

The area surrounding the facility largely remains agricultural and rural in nature, with much of 

the surrounding land vacant. Pendleton City center is located approximately 3 miles southeast 

of the facility. While there is some growth expected in the overall region, future land use in the 

immediate area is not expected to change and will remain rural in character (Columbia Plateau 

Ecoregion, 2019). Pendleton AASF #2 is entirely fenced with restricted site access and is 

responsible for various training activities and aircraft maintenance. The ARNG lease for

Pendleton AASF #2 expires in 2049, and activities and land use within the facility are not 

expected to change. 
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2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

The following birds, fishes, insects, and mammals are federally endangered, threatened, 

proposed, and/ or are listed as candidate species in Umatilla County, Oregon (US Fish and 

Wildlife Service [USFWS], 2023). 

• Birds: Yellow-billed Cuckoo, Coccyzus americanus (threatened)

• Fishes: Bull Trout, Salvelinus confluentus (threatened)

• Insects: Monarch butterfly, Danaus plexippus (candidate)

• Mammals: Little brown bat, Myotis lucifugus (under review); Gray wolf, Canis lupus

(endangered)

2.3 History of PFAS Use 

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

released historically at RTC (AECOM, 2020). 

• AOI 1 – Eastern Detention Basin: AFFF was historically released at this AOI during

familiarization training and fire training activities between approximately 1998 to 2013.

• AOI 2 – Ramp Area: AFFF was historically stored and released at this AOI during

familiarization training and fire training activities between approximately 1998 to 2013.

• AOI 3 – Readiness Center: From approximately 1988 to 1992, a firetruck that potentially

contained AFFF was parked at this former hangar.

The potential release areas were grouped into three AOIs based on preliminary data and 

presumed groundwater flow directions. A description of each AOI is presented in Section 3. 
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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, three potential release areas were 

identified at Pendleton AASF #2 and grouped into three AOIs (AECOM, 2020). The potential 

release areas are shown on Figure 3-1. 

3.1 AOI 1 Eastern Detention Basin

AOI 1 is the Eastern Detention Basin. While two detention basins exist within the Pendleton 

AASF #2, only the eastern detention pond was used for fire training activities.

Approximately two to three full TriMaxTM 30 mobile fire extinguishers, each containing 

approximately 30 gallons of concentrated AFFF, were released within and near the Detention 

Basin and edge of the ramp area every 2 to 3 years for nozzle practice and fire training 

activities. These nozzle releases occurred between approximately 1998 and 2013. Other fire 

training activities, including previous training events with the City of Pendleton Fire Department, 

burning of organic debris, and helicopter training exercises, all historically occurred in and 

around this Detention Basin; however, according to interviews, none of these activities involved 

the use or release of AFFF.

3.2 AOI 2 Ramp Area

AOI 2 is the Ramp Area used for helicopter staging. This area consists mostly of a mixture of 

paved asphalt and concrete on the eastern side of the facility, adjacent to the AOI 1 Detention 

Basin. As stated above, although a majority of the nozzle testing trainings, which occurred from 

approximately 1998 through 2013, involved the release of AFFF into the Eastern Detention 

Basin, some of the nozzle testing events carried over onto the edge of the Ramp Area. 

Additionally, during this same timeframe, 10 TriMaxTM 30 mobile fire extinguishers were stored 

throughout the ramp area for emergency response purposes.

Spills or releases were not reported from TriMaxTM 30 mobile fire extinguishers during the 

duration of their storage on the ramp area; however, long-term storage in non-climate-controlled 

areas leaves the potential for unintended spills or releases from mobile fire extinguishers. Any 

potential spills or releases in or around the Ramp Area would be captured in the trench drains 

and catch basins located throughout the facility and discharged into the western and eastern 

detention basins at the facility. The Ramp Area is located on the eastern side of the facility, with 

surface water and groundwater flow to the northeast, towards AOI 1. 

3.3 AOI 3 Readiness Center

The Readiness Center is on the southwest corner of the facility. From approximately 1988 to 

1992, a firetruck was parked at this former hangar. The firetruck originated from the Salem 

AASF and was stored at the hangar for several years. While one interviewee claimed the 

firetruck had AFFF present upon arrival to the facility, another interviewee claimed the firetruck 

only held non-PFAS containing material. The type, quantity, and concentration of AFFF (if ever 

present) on the firetruck during the storage period are unknown.

During interviews, it was confirmed that no firefighting material was removed, released, or 

transferred from the truck during the duration of storage at the Readiness Center. If the firetruck 

stored AFFF, there is potential for spills or releases from the truck. The Readiness Center is 

considered a potential release area.
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3.4 Adjacent Sources

Two off-facility, potential sources were identified adjacent to Pendleton AASF #2 during the PA 

and are not associated with ARNG activities. The adjacent potential sources are shown on 

Figure 3-1 and described in the following sections for informational purposes only and will not 

be investigated as part of this SI. 

3.4.1 Eastern Oregon Regional Airport

The Eastern Oregon Regional Airport is located directly adjacent to the Pendleton AASF #2, 

with Runway 7 directly north of the facility and Runway 11 extending diagonally to the eastern 

boundary of the facility. According to one interviewee, the City of Pendleton Fire Department has 

an AFFF-capable firetruck stored at the Eastern Oregon Regional Airport for aviation-related 

emergency response incidents. It is believed that this firetruck was never used or deployed 

during its storage at the airport; however, the timeframe for storage of this firetruck could not be 

confirmed, and airport personnel could not confirm if the firetruck is still parked within the airport. 

Several emergency response incidents have historically occurred at the Eastern Oregon 

Regional Airport. During interviews, the City of Pendleton Fire Chief confirmed that an aviation 

crash occurred in June 2017 that involved the use of AFFF. The crash occurred on the airfield 

adjacent to the Pendleton AASF #2, and an unknown amount of AFFF from the City of 

Pendleton fire department was used to suppress the fire. According to the Fire Chief, the City of 

Pendleton Fire Department has multiple firetrucks with AFFF-capabilities that assists in 

responding to aviation-related emergency response activities. A mixture of 3% and 6% AFFF 

were used to aid in fire suppression for this emergency response incident. During the PA, 

interviewees reported that other emergency response incidents involving the use of AFFF have 

historically occurred at the Eastern Oregon Regional Airport; however, exact dates and potential 

quantities of AFFF released during these emergency response incidents are unknown. 

The Eastern Oregon Regional Airport conducts yearly nozzle testing as required by the FAA. 

The two AFFF-capable firetrucks go to various areas throughout the airport to release several 

gallons of concentrated AFFF during nozzle testing. Interviewees stated that the nozzle testing 

only occurs once per year and requires the release of several gallons of concentrated AFFF; 

however, the location of these nozzle tests varies and happens at randomly chosen areas 

throughout the airport. The Eastern Oregon Regional Airport has bulk AFFF stored inside of the 

fire station within 5-gallon buckets. This bulk AFFF is only used to refill firetrucks following 

emergency response activities or yearly nozzle testing activities. The exact quantity and 

concentration of AFFF stored within the fire station at the airport could not be confirmed. 

3.4.2 City of Pendleton Fire Department

The City of Pendleton Fire Department is located approximately 4 miles southeast of the 

Pendleton AASF #2, along the Umatilla River. This adjacent potential source is identified for 

informational purposes, and given the presumed and measured groundwater flow of the area, 

potential PFAS impacts from this adjacent source are not anticipated to migrate towards the 

facility.
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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, 2022a), 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 Pendleton AASF #2 (AECOM, 2020);

• 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, 2022a); 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 summer 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, 2022a). 

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 
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AECOM 4-2

considered to assess whether the collected data are of the right type, quality, and quantity to 

support the decision-making (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, 2022a). 
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Army Aviation Support Facility #2, Pendleton, Oregon

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, Pendleton Army Aviation Support Facility #2,

Pendleton dated May 2020 (AECOM, 2020);

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

Army Aviation Support Facility #2, Pendleton, Oregon dated August 2022 (AECOM,

2022a); and

• Final Site Safety and Health Plan, Army Aviation Support Facility #2, Pendleton, Oregon

dated August 2022 (AECOM, 2022b).

The SI field activities were conducted from 29 August to 31 August, 1 September to 15 

September 2022 and consisted of utility clearance, sonic drilling, soil sample collection, temporary 

and permanent monitoring well installation, well development, and groundwater sample collection. 

Land surveying and synoptic depth to groundwater measurement was conducted on 14 

December 2022. Field activities were conducted in accordance with the SI QAPP Addendum 

(AECOM, 2022a).

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:

• Thirty-six (36) soil samples from seven (7) sonic borings and nineteen (19) hand auger

locations;

• Four (4) grab groundwater samples from three (3) temporary well locations;

• Four (4) groundwater samples from four (4) permanent well locations; and

• Twenty (20) 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.
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 5-2

5.1.1 Technical Project Planning

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

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

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

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

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

address the AOIs identified in the PA. 

A combined TPP Meeting 1 and 2 was held on 18 February 2022, 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, and Oregon Department of 

Environmental Quality (ORDEQ). 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, 2022a). 

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 26 September and 24 August 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 29 August 2022 with input from the AECOM field team and Pendleton AASF #2

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

and/or air knife to verify utility clearance in shallow subsurface where utilities would typically be 

encountered.

5.1.3 Source Water and Sampling Equipment Acceptability

One potable water source at Pendleton AASF #2 was sampled on 9 June 2022 to assess 

usability for decontamination of drilling equipment. Results of the sample collected from a spigot 

(PAASF-DECON-01) connected to the Readiness Center confirmed this source to be 

acceptable for use in this investigation; therefore, it was used throughout the field activities.

Water at the facility is provided by the City of Pendleton and is sourced offsite. Specifically, the 

samples were analyzed by LC/MS/MS compliant with QSM 5.3 Table B-15. The results of the 

decontamination water sample associated with the wash rack spigot source used during the SI 

are provided in Appendix F. A discussion of the results is presented in the DUA (Appendix A). 

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

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

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

QAPP Addendum (AECOM, 2022a). 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. 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 5-3

5.2 Soil Borings and Soil Sampling

Soil samples were collected via sonic drilling technology and hand auger in accordance with the 

SI QAPP Addendum (AECOM, 2022a). A Terra Sonic International (TSi) 150CC Sonic Drill Rig 

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 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 saturated soil or bedrock, and one subsurface soil 

sample at the mid-point between the surface and saturated soil or bedrock. At AOI02-01, 

subsurface soil samples could not be collected due to shallow bedrock; therefore, only the 

surface soil sample (0 to 2 feet bgs) was collected. To supplement the drilled boring locations, 

additional surface soil samples were collected at other locations within each AOI using a hand 

auger.

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 boring logs (Appendix E) 

and in a non-treated 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. 

During the SI, borings were completed to depths ranging between 20 to 33 feet bgs. Soils 

observed generally consisted of dry silts with varying quantities of sand and gravel. Weathered 

and broken basalt bedrock was observed as shallow as 3.5 feet bgs, and strong, intact basalt 

bedrock was observed as shallow as 12 feet bgs. The basalt was generally observed to be 

aphanitic and variably oxidized. Water bearing vesicles were observed in basalt in borings within 

AOI 2 and AOI 3 from 15 to 33 feet bgs. Small quantities of clay were observed within fractures 

at AOI02-02 and AOI03-01, at depths ranging between 26 to 33 feet bgs. The clay appears to 

be a byproduct of water weathering the parent basalt rock. The observed silts may consist of a 

mixture of fill and loess, and the basalt encountered appears consistent with the mapped 

Wanapum Basalt underneath the facility. Each soil sample was collected into laboratorysupplied 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, 

2022a). 

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

as the accompanying samples. Matrix spike/matrix spike duplicates (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.

Sonic borings were converted to temporary wells and/or permanent monitoring wells. The 

temporary wells were subsequently abandoned in accordance with the SI QAPP Addendum 

(AECOM, 2022a) using bentonite chips at completion of sampling activities. 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 5-4

5.3 Temporary Well Installation and Groundwater Grab Sampling

Three temporary wells were installed using a TSi 150CC Sonic Drill Rig (AOI01-01S, AOI01-02, 

and AOI01-03). Once the borehole was advanced to the desired depth, a temporary well was 

constructed of a 5-foot section of 2-inch diameter, 0.020-inch slotted 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 5-3. 

Location AOI01-01 was initially installed as a temporary well (AOI01-01S). The temporary well 

was removed after sampling, and location AOI01-01 was drilled to a deeper depth and 

converted to a permanent monitoring well (AOI01-01D, discussed in Section 5.4). 

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

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

period, groundwater samples were collected using a peristaltic 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 [DO], and oxidation-reduction potential [ORP]) were 

measured using a water quality meter and recorded on the field sampling form (Appendix B2) 

before each grab sample was collected. At two wells (AOI01-01S and AOI01-02), limited 

groundwater recharge rates were observed. Subsequently, in accordance with the SI QAPP 

Addendum, samples were collected prior to turbidity stabilization or reduction to ≤ 25 

nephelometric turbidity units. As discussed in Section 5.4, AOI01-01 was redrilled to a deeper 

depth and sampled as a permanent well. AOI01-02 was initially sampled after installation, but 

due to low recharge and high turbidity, it was allowed to recharge overnight and was resampled 

the following day. However, similar limited recharge conditions were encountered at AOI01-02; 

therefore, the well was sampled prior to turbidity stabilization or reduction to ≤ 25 nephelometric 

turbidity units. 

Additionally, a subsample of each groundwater sample was collected in a separate container, 

and a shaker test was completed to identify if there were any foaming. No foaming was noted in 

any of the groundwater samples. Each sample was collected into laboratory-supplied PFAS-free 

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

and transported via FedEx under standard CoC procedures to the laboratory and analyzed by 

LC/MS/MS compliant with QSM 5.3 Table B-15 in accordance with the SI QAPP Addendum 

(AECOM, 2022a). 

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.

The temporary wells were abandoned in accordance with the SI QAPP Addendum (AECOM, 

2022a) 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 Permanent Well Installation and Groundwater Sampling

During the SI, four permanent monitoring wells (AOI01-01D, AOI02-01, AOI02-02, and AOI03-

01) were installed within or in the vicinity of their respective AOIs. The locations of the wells are

shown on Figure 5-2.
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 5-5

A TSi 150CC Sonic Drill Rig drill rig was used to install four monitoring wells. The monitoring 

wells were constructed with 2-inch diameter Schedule 40 PVC, flush threaded 10-foot sections 

of riser, with a 0.020-inch slotted well screen and a threaded bottom cap. The filter pack of 2/12 

Cemex sand was installed at least 1 foot above the top of the well screen. A well seal consisting 

of hydrated bentonite chips was placed above the sand pack. All monitoring wells were 

completed with flush mount well vaults, with the exception of AOI02-01, which has stickup 

completion. Bollards were also installed around AOI02-01. Wells were installed, completed, and 

developed accordance with Oregon Administrative Rules Chapter 690 Division 240. The screen 

interval of each of the groundwater monitoring wells is provided in Table 5-3. 

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

(AECOM, 2022a). The newly installed monitoring wells were developed no sooner than 24 

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

Samples were collected no sooner than 24 hours following development via low-flow sampling 

methods using a peristaltic pump with disposable PFAS-free, HDPE tubing. New tubing was 

used at each well and the pumps were decontaminated between each well. The wells were 

purged at a rate determined in the field to reduce draw down prior to sampling. Water quality 

parameters (e.g., temperature, turbidity, specific conductance, pH, DO, and ORP) were 

measured using a water quality meter and recorded on the field sampling form (Appendix B2). 

Water levels were measured to the nearest 0.01 inch and recorded. Additionally, a subsample of 

each groundwater sample was collected in a separate container and a shaker test was 

completed to identify if there was 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, 2022a). 

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. 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 14 December 2022. Groundwater 

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

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

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

5.6 Surveying 

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

following guidelines provided in the SOPs provided in the SI QAPP Addendum (AECOM, 

2022a). Survey data from the newly installed wells on the facility were collected on 14

December 2022 in the applicable Universal Transverse Mercator zone projection with both 

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

(WGS84). Survey data was collected in vertical datum North American Vertical Datum 1988 

(NAVD88). The surveyed well data are provided in Appendix B3. 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 5-6

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, 2022a) and with the DA Guidance for 

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

Soil and rock IDW (i.e., soil and rock cuttings) generated during the SI activities were contained 

in labeled, 55-gallon Department of Transportation (DOT)-approved steel drums and left onsite 

in a designated waste storage area located along the southern boundary of AOI 2. The soil IDW 

was not sampled and assumes the characteristics of the associated soil samples collected from 

that source location. ARNG will coordinate waste profiling, transportation, and disposal of the 

solid IDW under a separate contract. 

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 with the soil and rock IDW. The liquid IDW was not sampled and assumes the 

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

Containerized liquid IDW will be managed and disposed of by ARNG (either by offsite disposal 

or onsite disposal with treatment, as appropriate) under a separate contract in accordance with 

SOP No. 042A (EA, 2021).

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

unused monitoring well construction materials, and other environmental media generated during 

the field activities were disposed of at a licensed solid waste landfill.

5.8 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. 
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Pendleton AASF #2, 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 8/31/2022 8:35 0 - 2 X

AOI01-01-SB-5-7 8/31/2022 11:25 5 - 7 X

AOI01-01-SB-8.5-10.5 8/31/2022 11:30 8.5 - 10.5 X

AOI01-02-SB-0-2 8/30/2022 11:10 0 - 2 X

AOI01-02-SB-5-6 8/30/2022 15:00 5 - 6 X

AOI01-02-SB-7-8 8/30/2022 15:05 7 - 8 X

AOI01-03-SB-0-2 8/31/2022 9:25 0 - 2 X

AOI01-03-SB-5-6 8/31/2022 13:05 5 - 6 X

AOI01-03-SB-8-10 8/31/2022 13:10 8 - 10 X

AOI01-04-SB-0-2 8/31/2022 10:20 0 - 2 X

AOI01-05-SB-0-2 8/31/2022 9:40 0 - 2 X

AOI01-06-SB-0-2 9/6/2022 13:15 0 - 2 X

AOI01-07-SB-0-2 9/6/2022 12:50 0 - 2 X

AOI01-07-SB-0-2-DUP 9/6/2022 12:50 0 - 2 X FD

AOI01-08-SB-0-2 9/6/2022 12:30 0 - 2 X

AOI01-09-SB-0-2 8/31/2022 8:55 0 - 2 X

AOI01-09-SB-0-2-DUP 8/31/2022 8:55 0 - 2 X FD

AOI01-10-SB-0-1 8/29/2022 15:10 0 - 1 X

AOI01-10-SB-0-1-MS 8/29/2022 15:10 0 - 1 X

AOI01-10-SB-0-1-MSD 8/29/2022 15:10 0 - 1 X MS

AOI01-11-SB-0-1 8/29/2022 15:50 0 - 1 X X X MSD

AOI01-11-SB-0-1-DUP 8/29/2022 15:50 0 - 1 X X X FD

AOI01-12-SB-0-1 8/29/2022 15:50 0 - 1 X

AOI01-12-SB-0-1-DUP 8/29/2022 15:50 0 - 1 X FD

AOI01-13-SB-0-2 9/6/2022 11:45 0 - 2 X

AOI01-14-SB-0-2 9/6/2022 11:30 0 - 2 X

AOI02-01-SB-1-2 8/30/2022 9:25 1 - 2 X

AOI02-02-SB-0-2 8/30/2022 8:55 0 - 2 X X X

AOI02-02-SB-5-6 8/31/2022 14:10 5 - 6 X

AOI02-02-SB-8-10 8/31/2022 14:15 8 - 10 X

AOI02-03-SB-0-0.5 9/6/2022 13:40 0 - 0.5 X

AOI02-04-SB-0-0.5 9/6/2022 13:55 0 - 0.5 X

AOI02-05-SB-0-0.5 9/6/2022 14:05 0 - 0.5 X

AOI02-06-SB-0-2 8/30/2022 16:30 0 - 2 X

AOI02-07-SB-0-0.5 9/6/2022 10:30 0 - 0.5 X

AOI02-08-SB-0-1 9/6/2022 10:00 0 - 1 X

AOI02-09-SB-0-0.5 9/6/2022 10:50 0 - 0.5 X

AOI03-01-SB-0-0.5 8/31/2022 15:00 0 - 0.5 X X X

AOI03-01-SB-0-0.5-DUP 8/31/2022 15:00 0 - 0.5 X FD

AOI03-01-SB-5-6 9/1/2022 9:55 5 - 6 X

AOI03-01-SB-8-10 9/1/2022 10:00 8 - 10 X

AOI03-02-SB-0-0.5 8/31/2022 15:05 0 - 0.5 X

AOI03-02-SB-0-0.5-MS 8/31/2022 15:05 0 - 0.5 X MS

AOI03-02-SB-0-0.5-MSD 8/31/2022 15:05 0 - 0.5 X MSD

AOI03-03-SB-0-1 8/31/2022 15:25 0 - 1 X X X

AOI03-03-SB-0-1-MS 9/2/2022 9:00 0 - 1 X X X MS

AOI03-03-SB-0-1-MSD 9/2/2022 9:00 0 - 1 X X X MSD

Soil Samples

AECOM 5-7 
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Pendleton AASF #2, 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-GW 9/1/2022 14:35 NA X (AOI01-01S)

AOI01-01-GW-20220915 9/15/2022 9:50 NA X (AOI01-01D)

AOI01-01-GW-20220915-D 9/15/2022 9:50 NA X (AOI01-01D) FD

AOI01-01-GW-MS 9/15/2022 9:50 NA X (AOI01-01D) MS

AOI01-01-GW-MSD 9/15/2022 9:50 NA X (AOI01-01D) MSD

AOI01-02-GW 8/31/2022 9:45 NA X

AOI01-02-GW-2 9/1/2022 15:45 NA X

AOI01-03-GW 9/1/2022 14:10 NA X

AOI02-01-GW 9/15/2022 9:00 NA X

AOI02-02-GW 9/15/2022 10:35 NA X

AOI03-01-GW 9/15/2022 11:20 NA X

PAASF-DECON-01 6/9/2022 7:25 NA X Spigot

PAASF-DECON-02 9/1/2022 9:15 NA X Decon System

PAASF-ERB-01 8/29/2022 14:40 NA X Hand Auger

PAASF-ERB-02 8/29/2022 14:45 NA X Shovel

PAASF-ERB-03 9/1/2022 8:15 NA X Sonic Bit

PAASF-FRB-01 8/29/2022 14:50 NA X

Notes:

AOI = Area of Interest

ASTM = American Society for Testing and Materials

bgs = below ground surface

ERB = equipment rinsate blank

FD = field duplicate

FRB = field reagent blank

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

PAASF = Pendleton AASF #2

QSM = Quality Systems Manual

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

Quality Control Samples

Groundwater Samples

AECOM 5-8
Area of 

Interest

Boring 

Location

Soil Boring 

Depth 

(feet bgs)

Permanent Well 

Screen Interval 

(feet bgs)

AOI01-01S* 20 15 - 20

AOI01-01D* 33 13 - 33

AOI01-02 20 15 - 20

AOI01-03 20 15 - 20

AOI02-01 31 15 - 30

AOI02-02 33 13 - 33

3 AOI03-01 40 20 - 40

Notes:

*AOI01-01S was later overdrilled and replaced with permanent monitoring well AOI01-01D (see Table 5-3)

AASF = Army Aviation Support Facility

AOI = Area of Interest

bgs = below ground surface

S = shallow

D = deep

Table 5-2

Soil Boring Depths and Temporary Well Screen Intervals

Site Inspection Report, Pendleton AASF #2, Pendleton, 

Oregon

2

1

AECOM 5-9 
Area of 

Interest

Monitoring 

Well ID

Well Screen 

Interval 

(feet bgs)

Top of Casing 

Elevation 

(feet NAVD88)

Ground Surface 

Elevation 

(feet NAVD88)

Depth to 

Water

(feet btoc)

Depth to 

Water

(feet bgs)

Groundwater 

Elevation

(feet NAVD88)

1 AOI01-01D* 13 - 33 1485.60 1485.89 18.56 18.85 1467.04

AOI02-01 15 - 30 1485.13 1482.59 18.35 15.81 1466.78

AOI02-02 13 - 33 1487.78 1488.00 18.92 19.14 1468.86

3 AOI03-01 20 - 40 1494.17 1494.52 23.52 23.87 1470.65

Notes:

*Location originally installed as a temporary well (AOI01-01S, as shown in Table 5-2) and was later overdrilled to install permanent well AOI01-01D

AASF = Army Aviation Support Facility

AOI = Area of Interest

bgs = below ground surface

btoc = below top of casing

D = deep

S = shallow

NA = not applicable

NAVD88 = North American Vertical Datum 1988

2

Table 5-3

Permanent Monitoring Well Screen Intervals and Groundwater Elevations

Site Inspection Report, Pendleton AASF #2, Pendleton, Oregon

AECOM 5-10
A!

!?

!?

A!

A!

"S

A! "S "S

"S

"S

"S

"S "S "S

"S

"S "S

"S

"S

"S

"S

"S

"S "S

"S

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI02-03

AOI03-01

AOI03-03 AOI03-02

AOI01-04

AOI01-05

AOI01-06

AOI01-07

AOI01-08 AOI01-09

AOI01-10

AOI01-11 AOI01-12

AOI01-13

AOI01-14

AOI02-04

AOI02-05

AOI02-06

AOI02-07 AOI02-08

AOI02-09

AOI 1

AOI 2

AOI 3

Figure 5-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

2/23/2023

2/23/2023

2/23/2023

MS

AP

CM

GIS BY

CHK BY

PM

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

2/23/2023

Site Inspection Sample Locations

12420 Milestone Center Drive

Germantown, MD 20876

Legend

A! Permanent Monitoring Well

!? Temporary Monitoring Well

"S Surface Soil Sample

Area of Interest

Facility Boundary

Surface Water Flow Direction

1:1,800

Groundwater Flow Direction

0 75 150 300

Feet

­

AECOM 5-11
THIS PAGE INTENTIONALLY BLANK

5-12
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

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 6.5. Table 6-2 through Table 6-4 present results in soil or groundwater for the 

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

laboratory reports are provided in Appendix G. 

6.1 Screening Levels 

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

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

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

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

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

CERCLA. The SLs established in the OSD memorandum apply to the five compounds 

presented on Table 6-1 below.

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

Analyteb

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ 

Commercial 

Composite 

Worker 

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater) 

(ng/L)a

PFOA 19 250 6 

PFOS 13 160 4

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6 

Notes:

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

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

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

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

included as an analyte at the time of this SI. Based on the CSM developed during the PA and revised based on SI findings, the 

presence of 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.

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

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

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

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

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

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

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

Army Aviation Support Facility #2, Pendleton, 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: Eastern Detention Basin. The soil and groundwater results are summarized on Table 6-2

through Table 6-4. Soil and groundwater results are presented on Figure 6-1 through Figure 6-

7. 

6.3.1 AOI 1 Soil Analytical Results

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

AOI01-14. Soil was also sampled from shallow subsurface soil (5 to 10.5 feet bgs) from boring 

locations AOI01-01 through AOI01-03. Deep subsurface samples (>15 feet bgs) were not 

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

Table 6-3 summarize the soil results. 

In surface soil, PFOS exceeded the 13 micrograms per kilogram (μg/kg) SL at two locations, at 

concentrations of 31.0 μg/kg (AOI01-06) and 17.8 μg/kg (AOI01-12). PFOA, PFBS, PFHxS, and 

PFNA were detected in surface soil at concentrations at least one order of magnitude below the 

SLs. The maximum detected concentration was PFHxS at 11.2 μg/kg at AOI01-06.

In shallow subsurface soil, PFOS was detected at two locations. Detected concentrations were 

at least one order of magnitude below the 160 μg/kg SL, with a maximum concentration of 3.79 

J+ μg/kg at AOI01-01 (5 to 7 feet bgs). PFOA, PFBS, PFHxS, and PFNA were not detected in 

shallow subsurface soil at AOI 1. 

6.3.2 AOI 1 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring well AOI01-01D and temporary 

monitoring wells AOI01-01S, AOI01-02, and AOI01-03. Figure 6-6 and Figure 6-7 present the 

ranges of detections in groundwater. Table 6-4 summarizes the groundwater results. 

The following exceedances of the SLs were measured:

• PFOA was detected above the 6 nanograms per liter (ng/L) SL at one of the four

wells, with a concentration of 7.84 J ng/L at AOI01-02.

• PFOS was detected above the 4 ng/L SL at two of the four wells, with concentrations

of 31.0 J ng/L at AOI01-02 and 4.54 J ng/L at AOI01-03.
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 6-3

• PFHxS was detected above the 39 ng/L SL at one of the four wells, with a maximum

concentration of 124 J ng/L at AOI01-02.

• PFNA was detected above the 6 ng/L SL at one of the four wells, with a concentration

of 12.1 ng/L at AOI01-02.

PFBS was detected in groundwater at four of the wells at AOI 1, but below the below the 601 

ng/L SL. 

6.3.3 AOI 1 Conclusions

Based on the results of the SI, PFOS was detected in soil above the SLs. PFOA, PFOS, 

PFHxS, and PFNA were detected in groundwater at concentrations above the SLs. Based on 

the exceedances of the SLs in soil and groundwater, further evaluation at AOI 1 is warranted. 

6.4 AOI 2 

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

AOI 2: Ramp Area. The results in soil and groundwater are summarized on Table 6-2 through 

Table 6-4. Soil and groundwater results are presented on Figure 6-1 through Figure 6-7. 

6.4.1 AOI 2 Soil Analytical Results

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

AOI02-09. Soil was also sampled from shallow subsurface soil (5 to 10 feet bgs) from boring 

location AOI02-02. Deep subsurface soil samples (>15 feet bgs) were not collected. Figure 6-1

through Figure 6-5 present the ranges of detections in soil. Table 6-2 and Table 6-3 summarize 

the soil results. 

In surface soil, PFOA, PFOS, PFHxS, and PFNA were detected at concentrations below the 

SLs. The maximum detected concentration was PFOS at 7.38 μg/kg at AOI02-08. PFBS was 

not detected in surface soil. Relevant compounds were not detected in shallow subsurface soil 

at AOI 2.

6.4.2 AOI 2 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring wells AOI2-01 and AOI2-02. Figure 6-6

and Figure 6-7 present the ranges of detections in groundwater. Table 6-4 summarizes the 

groundwater results. The following exceedances of the SLs were measured:

• PFOA was detected above the 6 ng/L SL at one of the two wells, with a concentration

of 18.1 ng/L at AOI02-1.

• PFOS was detected above the 4 ng/L SL at both wells, with concentrations of 5.15

ng/L at AOI02-01 and 6.67 ng/L at AOI02-02.

• PFHxS was detected above the 39 ng/L SL at one of the two wells, with a

concentration of 519 ng/L at AOI02-01.

PFBS and PFNA were detected in groundwater at AOI 2 below the SLs.

6.4.3 AOI 2 Conclusions

Based on the results of the SI, relevant compounds were detected in soil below the SLs. PFOA, 

PFOS and PFHxS were detected in groundwater at concentrations above the SLs. Well AOI02-

02 is located along the facility boundary and is in the upgradient portion of the facility based on 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 6-4

the groundwater elevations measured during the SI, indicating that there may be an adjacent, 

offsite source. Based on the exceedances of the SLs in groundwater, further evaluation at AOI 2 

is warranted. 

6.5 AOI 3

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

AOI 3: Readiness Center. The results in soil and groundwater are presented in Table 6-2 

through Table 6-4. Soil and groundwater results are presented on Figure 6-1 through Figure 6-

7.

6.5.1 AOI 3 Soil Analytical Results

Soil was sampled from surface soil (0 to 1 feet bgs) from boring locations AOI03-01 through 

AOI03-03. Soil was also sampled from shallow subsurface soil (5 to 10 feet bgs) from boring 

location AOI03-01. Deep subsurface soil samples (>15 feet bgs) were not collected. Figure 6-1 

through Figure 6-5 present the ranges of detections in soil. Table 6-2 and Table 6-3 summarize 

the soil results.

In surface soil, PFOA, PFOS, PFBS, PFHxS, and PFNA were detected at concentrations below 

the SLs. The maximum detected concentration was PFOS at 1.61 μg/kg at AOI03-01.

In shallow subsurface soil, PFOA, PFOS, PFBS, PFHxS, and PFNA were detected at 

concentrations below the SLs. The maximum detected concentration was PFNA at 59.4 μg/kg at 

AOI03-01 (5 to 6 feet bgs).

6.5.2 AOI 3 Groundwater Analytical Results

Groundwater was sampled from permanent monitoring well AOI03-01. Figure 6-6 and Figure 6-

7 present the ranges of detections in groundwater. Table 6-4 summarizes the groundwater 

results. PFOA, PFBS, and PFHxS were detected in groundwater at concentrations below the 

SLs. The maximum detected concentration was PFBS at 22.5 ng/L. PFOS and PFNA were not 

detected in groundwater at AOI 3.

6.5.3 AOI 3 Conclusions

Based on the results of the SI, relevant compounds were detected in soil and groundwater 

below the SLs. However, as AOI 3 is located upgradient of AOI 1 and AOI 2 at which 

exceedances of soil and groundwater were observed, further evaluation of AOI 3 is warranted.
Table 6-2

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

Site Inspection Report, Pendleton Army Aviation Support Facility #2

Analyte OSD Screening

Level a

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

PFBS 1900 ND U ND U ND U ND U ND UJ 0.539 J 0.028 J ND UJ ND U ND U

PFHxS 130 ND U 0.036 J 0.040 J 0.033 J 0.061 J+ 11.2 0.071 J 0.048 J 3.50 0.116 J

PFNA 19 ND U 0.167 J 0.023 J 0.025 J 0.069 J+ 0.262 J ND U ND U ND U 0.189 J

PFOA 19 ND U ND U ND U 0.185 J 0.164 J+ 0.953 J ND U ND U 0.398 J 0.085 J

PFOS 13 0.061 J 0.539 J 0.123 J 0.094 J 0.228 J+ 31.0 0.154 J 0.109 J 2.25 0.360 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 AASF Army Aviation Support Facility

J+ = Estimated concentration, biased high AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL DUP duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

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

AOI01-01-SB-0-2

08/31/2022

0-2 ft

AOI01-02-SB-0-2

08/30/2022

0-2 ft

AOI01-03-SB-0-2

08/31/2022

0-2 ft

09/06/2022

0-2 ft

AOIO1-04-SB-0-2

08/31/2022

0-2 ft

AOI01-05-SB-0-2

08/31/2022

0-2 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 residential scenario for incidental ingestion of contaminated soil.

AOI01

AOI01-09-SB-0-2

08/31/2022

0-2 ft

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

AOI01-07-SB-0-2-D

09/06/2022

0-2 ft

AOI01-08-SB-0-2

09/06/2022

0-2 ft

AOI01-06-SB-0-2

09/06/2022

0-2 ft

AOI01-07-SB-0-2

AECOM 6-5 
Table 6-2

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

Site Inspection Report, Pendleton Army Aviation Support Facility #2

Analyte OSD Screening

Level a

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

PFBS 1900 ND U ND U 0.023 J ND U ND UJ ND U ND U ND U ND U ND U

PFHxS 130 0.072 J 0.196 J 0.177 J 0.166 J 0.346 J 0.046 J ND U ND U 0.051 J 0.034 J

PFNA 19 0.143 J 0.289 J 0.090 J 0.526 J 0.807 J 0.130 J 0.029 J 0.029 J 0.261 J 0.243 J

PFOA 19 ND UJ 0.225 J 0.583 J 0.367 J 0.764 J ND U ND U ND U 0.086 J ND U

PFOS 13 0.223 J 0.819 J 1.02 J 15.6 17.8 0.357 J 0.100 J 0.496 J 0.722 J 0.312 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 AASF Army Aviation Support Facility

J+ = Estimated concentration, biased high AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL DUP duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

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

AOI01-09-SB-0-2-DUP

08/31/2022

0-2 ft

AOI01-10-SB-0-1

08/29/2022

0-1 ft

AOI01-11-SB-0-1

08/29/2022

0-1 ft

AOI01-14-SB-0-2

09/06/2022

0-2 ft

AOI01-12-SB-0-1

08/29/2022

0-1 ft

AOI01-12-SB-0-1-DUP

08/29/2022

0-1 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 residential scenario for incidental ingestion of contaminated soil.

AOI01 AOI02

AOI02-03-SB-0-0.5

09/06/2022

0-0.5 ft

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

AOI02-01-SB-1-2

08/30/2022

1-2 ft

AOI02-02-SB-0-2

08/30/2022

0-2 ft

AOI01-13-SB-0-2

09/06/2022

0-2 ft

AECOM 6-6
Table 6-2

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

Site Inspection Report, Pendleton Army Aviation Support Facility #2

Analyte OSD Screening

Level a

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

PFBS 1900 ND U ND U ND U ND U ND U ND U ND U ND U ND U 0.031 J

PFHxS 130 ND U 0.125 J ND U 0.050 J 1.02 J 0.056 J 0.068 J 0.049 J 0.085 J 0.147 J

PFNA 19 0.129 J 0.515 J ND U 0.078 J 4.88 0.045 J 1.35 1.09 0.730 J 1.52

PFOA 19 ND U 0.094 J ND U 0.126 J 0.237 J ND U ND U ND U ND U 0.083 J

PFOS 13 0.497 J 0.770 J ND U 0.158 J 7.38 0.402 J 1.53 1.61 1.12 J+ 1.54

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 AASF Army Aviation Support Facility

J+ = Estimated concentration, biased high AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL DUP duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

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

AOI02-04-SB-0-0.5

09/06/2022

0-0.5 ft

AOI02-05-SB-0-0.5

09/06/2022

0-0.5 ft

AOI02-06-SB-0-2

08/30/2022

0-2 ft

AOI03-01-SB-0-0.5

08/31/2022

0-0.5 ft

AOI02-07-SB-0-0.5

09/06/2022

0-0.5 ft

AOI02-08-SB-0-1

09/06/2022

0-1 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 residential scenario for incidental ingestion of contaminated soil.

AOI02 AOI03

AOI03-03-SB-0-1-20220831

08/31/2022

0-1 ft

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

AOI03-01-SB-0-0.5-DUP

08/31/2022

0-0.5 ft

AOI03-02-SB-0-0.5

08/31/2022

0-0.5 ft

AOI02-09-SB-0-0.5

09/06/2022

0-0.5 ft

AECOM 6-7
Table 6-3

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

Site Inspection Report, Pendleton Army Aviation Support Facility #2

Analyte OSD Screening

Level a

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

PFBS 25000 ND U ND U ND U ND U ND U ND U ND U ND U 0.032 J 0.425 J

PFHxS 1600 ND U ND U ND U ND U ND U ND U ND U ND U 7.70 1.10 J

PFNA 250 ND U ND U ND U ND U ND U ND U ND U ND U 59.4 ND U

PFOA 250 ND U ND U ND U ND U ND U ND U ND U ND U 1.96 ND U

PFOS 160 3.79 J+ ND U ND U ND U 0.064 J+ ND U ND U ND U 5.48 ND UJ

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 AASF Army Aviation Support Facility

J+ = Estimated concentration, biased high AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. DL detection limit

ft feet

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

AOI01-01-SB-5-7

08/31/2022

5-7 ft

AOI01-01-SB-8.5-10.5

08/31/2022

8-10.5 ft

AOI01-02-SB-5-6

08/30/2022

5-6 ft 8-10 ft

AOI02-02-SB-5-6

08/31/2022

5-6 ft

AOI01-02-SB-7-8

08/30/2022

7-8 ft

AOI01-03-SB-5-6

08/31/2022

5-6 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.

AOI01 AOI02 AOI03

AOI03-01-SB-8-10

09/01/2022

8-10 ft

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

AOI02-02-SB-8-10

08/31/2022

8-10 ft

AOI03-01-SB-5-6

09/01/2022

5-6 ft

AOI01-03-SB-8-10

08/31/2022

AECOM 6-8
Table 6-4

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

Site Inspection Report, Pendleton Army Aviation Support Facility #2

Analyte OSD Screening

Level a

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

PFBS 601 3.99 J 4.20 J 3.96 J 5.68 6.02 ND UJ 31.7 3.44 J 22.5

PFHxS 39 7.31 J 122 J 124 J 12.7 13.6 4.15 J 519 2.77 J 4.97

PFNA 6 ND UJ 12.1 J ND UJ 1.00 J 1.13 J 1.40 J 1.75 J ND U ND U

PFOA 6 1.20 J 7.84 J 2.49 J 1.10 J 1.12 J 2.22 J 18.1 ND U 0.851 J

PFOS 4 0.891 J 31.0 J 2.97 J 1.53 J 1.00 J 4.54 J 5.15 6.67 ND U

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support Facility

U = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

UJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. 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

09/01/2022 09/15/2022

AOI01-02-GW-2

09/01/2022

AOIO1-02-GW

08/31/2022

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

09/15/2022

AOI03

AOI03-01-GW

09/15/2022

AOI01-03-GW

09/01/2022

AOI02-01-GW

09/15/2022

AOI01-01-GW-20220915

09/15/2022

AOI01-01-GW-20220915-D

AECOM 6-9
THIS PAGE INTENTIONALLY BLANK

AECOM 6-10
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI02-03

AOI03-01

AOI03-02

AOI03-03

AOI01-04

AOI01-05

AOI01-06

AOI01-07

AOI01-08

AOI01-09

AOI01-10

AOI01-11

AOI01-12

AOI01-13

AOI01-14

AOI02-04

AOI02-05

AOI02-06

AOI02-08 AOI02-07

AOI02-09

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-1

PFOA Detections in Soil

3/13/2023

3/13/2023

MS 3/13/2023

VG

CM

GIS BY

CHK BY

PM

3/13/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

Shallow

Intermediate

Deep

Legend

Facility Boundary

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

0 105

­

210 420

Feet

AECOM 6-11
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI02-03

AOI03-01

AOI03-02 AOI03-03

AOI01-04

AOI01-05

AOI01-06

AOI01-07

AOI01-08

AOI01-09

AOI01-10

AOI01-11

AOI01-12

AOI01-13

AOI01-14

AOI02-04

AOI02-05

AOI02-06

AOI02-07

AOI02-08

AOI02-09

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-2

PFOS Detections in Soil

3/13/2023

3/13/2023

MS 3/13/2023

VG

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3/13/2023

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REVISED

SCALE

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ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

Shallow

Intermediate

Deep

Legend

Facility Boundary

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

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

0 105

­

210 420

Feet

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

AECOM 6-12
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI02-03

AOI03-01

AOI03-02

AOI03-03

AOI01-04

AOI01-05

AOI01-06

AOI01-07

AOI01-08

AOI01-09

AOI01-10

AOI01-11

AOI01-12

AOI01-13

AOI01-14

AOI02-04

AOI02-05

AOI02-06

AOI02-08 AOI02-07

AOI02-09

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-3

PFBS Detections in Soil

3/13/2023

3/13/2023

MS 3/13/2023

VG

CM

GIS BY

CHK BY

PM

3/13/2023

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REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

Shallow

Intermediate

Deep

Legend

Facility Boundary

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

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

0 105

­

210 420

Feet

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

AECOM 6-13
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI02-03

AOI03-01

AOI03-02 AOI03-03

AOI01-04

AOI01-05

AOI01-06

AOI01-07

AOI01-08

AOI01-09

AOI01-10

AOI01-11

AOI01-12

AOI01-13

AOI01-14

AOI02-04

AOI02-05

AOI02-06

AOI02-08 AOI02-07

AOI02-09

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-4

PFHxS Detections in Soil

3/13/2023

3/13/2023

MS 3/13/2023

VG

CM

GIS BY

CHK BY

PM

3/13/2023

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REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

Shallow

Intermediate

Deep

Legend

Facility Boundary

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

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

0 105

­

210 420

Feet

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

AECOM 6-14
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI02-03

AOI03-01

AOI03-02 AOI03-03

AOI01-04

AOI01-05

AOI01-06

AOI01-07

AOI01-08

AOI01-09

AOI01-10

AOI01-11

AOI01-12

AOI01-13

AOI01-14

AOI02-04

AOI02-05

AOI02-06

AOI02-07

AOI02-08

AOI02-09

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-5

PFNA Detections in Soil

3/13/2023

3/13/2023

MS 3/13/2023

VG

CM

GIS BY

CHK BY

PM

3/13/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

Shallow

Intermediate

Deep

Legend

Facility Boundary

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

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

0 105

­

210 420

Feet

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-15
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI03-01

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-6

PFOA, PFOS, and PFBS Detections

in Groundwater

2/23/2023

2/23/2023

MS 2/23/2023

VG

CM

GIS BY

CHK BY

PM

2/23/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

PFOA

PFOS

PFBS

Legend

Facility Boundary

Groundwater Flow Direction

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

0 105

­

210 420

Feet

PFBS Results (ng/L)

ND

>ND - 100

>100 - 601

>601 - 2,000

>2,000

PFOS Results (ng/L)

ND

>ND - 4

>4 - 40

>40 - 70

>70

AECOM 6-16
Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI03-01

Detention Basin

AOI01-01S/AOI01-01D

AOI01-02

AOI01-03

AOI02-01

AOI02-02

AOI03-01

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-7

PFHxS and PFNA Detections

in Groundwater

2/23/2023

2/23/2023

MS 2/23/2023

VG

CM

GIS BY

CHK BY

PM

2/23/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Pendleton AASF #2, OR

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

the GIS User Community

1:2,520

PFHxS

PFNA

Legend

Facility Boundary

Groundwater Flow Direction

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

0 105

­

210 420

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

AECOM 6-17
ection Report

ation Support Facility #2, Pendleton, Oregon

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 7-1

7. Exposure Pathways

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

Figure 7-3. 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 a 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 (though unlikely due to restricted access), residents 

outside the facility boundary, and recreational users outside of the facility boundary. 

7.1 Soil Exposure Pathway 

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

between the source and potential receptors at AOI 1, AOI 2, and AOI 3 based on the 

aforementioned criteria. 

7.1.1 AOI 1

AOI 1 is the Eastern Detention Basin, where AFFF was historically released during 

familiarization training and fire training activities between approximately 1998 to 2013.

Relevant compounds were detected in surface soil at AOI 1; PFOS exceeded the SL. No 

ongoing construction was observed at the facility during the SI. Site workers and future 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 7-2

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

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

construction workers are potentially complete. The facility is gated and there are no adjacent 

residential structures or recreational facilities; therefore, the incidental ingestion and inhalation 

of dust exposure pathways for the trespasser, residential, and recreational user receptors are 

considered incomplete.

Relevant compounds were detected in subsurface soil at AOI 1 at concentrations below the 

SLs. The construction worker exposure scenario assumes excavation occurs at depths at or 

above 15 feet bgs. Construction workers could contact constituents in subsurface soil via 

incidental ingestion, and 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 Ramp Area, where AFFF was historically stored and released during familiarization 

training and fire training activities between approximately 1998 to 2013.

Relevant compounds were detected in surface soil at AOI 2, below the SLs. Site workers and 

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

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

construction workers are potentially complete. The incidental ingestion and inhalation of dust

exposure pathways for the trespasser, residential, and recreational user receptors are 

considered incomplete for the same reasons established for AOI 1. 

Relevant compounds were not detected in subsurface soil at AOI 2; therefore, the subsurface 

soil exposure pathways for all receptors are considered incomplete. The CSM for AOI 2 is 

presented on Figure 7-2. 

7.1.3 AOI 3 

AOI 3 is the Readiness Center, where a firetruck potentially containing AFFF was parked at this 

former hangar between approximately 1988 to 1992. 

Relevant compounds were detected in surface soil at AOI 3, below the SLs. However, as AOI 3 

is located upgradient of AOI 1 and AOI 2 at which exceedances of soil and groundwater were 

observed, further evaluation of AOI 3 is warranted. Site workers and future construction workers 

could contact constituents in surface soil via incidental ingestion and inhalation of dust. 

Therefore, the surface soil exposure pathway for site workers and construction workers are 

potentially complete. The incidental ingestion and inhalation of dust exposure pathways for the 

trespasser, residential, and recreational user receptors are considered incomplete for the same 

reasons established for AOI 1.

Relevant compounds were detected in subsurface soil at AOI 3 at concentrations below the 

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

and therefore, the subsurface soil exposure pathway for future construction workers is 

potentially complete. The CSM for AOI 3 is presented on Figure 7-3. 

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.
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 7-3

7.2.1 AOI 1

Relevant compounds were detected in groundwater at AOI 1; PFOA, PFOS, PFHxS, and PFNA 

exceeded the SLs. Due to the potentially variable depth to bedrock and uncertainty of 

groundwater flow direction in the vicinity of the facility, as well as the presence of numerous

domestic wells within a 4-mile radius of the facility, the pathway for exposure to off-facility 

residents via ingestion of groundwater is considered potentially complete. The facility receives 

its drinking water from offsite wells operated by the City of Pendleton. Therefore, the pathway 

for exposure to site workers and recreational user/tresspassers via ingestion of groundwater is 

considered incomplete at this time. Depths to water measured at AOI 1 in December 2022

during the SI were greater than 18 feet bgs. The construction worker exposure scenario 

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

exposure pathway for future construction workers is considered incomplete. The CSM for AOI 1

is presented on Figure 7-1. 

7.2.2 AOI 2 

Relevant compounds were detected in groundwater at AOI 2; PFOA, PFOS, and PFHxS 

exceeded the SLs. The pathway for exposure to off-facility residents via ingestion of 

groundwater is considered potentially complete for the same reasons established for AOI 1.

Depths to water measured at AOI 2 in December 2022 during the SI were greater than 18 feet 

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

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

7.2.3 AOI 3 

Relevant compounds were detected groundwater at AOI 3 at concentrations below the SLs.

However, as AOI 3 is located upgradient of AOI 1 and AOI 2 at which exceedances of soil and 

groundwater were observed, further evaluation of AOI 3 is warranted. The pathway for exposure 

to off-facility residents via ingestion of groundwater is considered potentially complete for the 

same reasons established for AOI 1. 

Depths to water measured at AOI 3 in December 2022 during the SI were greater than 18 feet 

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

incomplete. The CSM for AOI 3 is presented on Figure 7-3. 

7.3 Surface Water and Sediment Exposure Pathway

Surface water and sediment samples were not collected; therefore, 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. Because relevant compounds were detected in soil and groundwater at AOI 1, it is possible 

that those compounds may exist in occasionally ponded surface water within the Eastern 

Detention Basin. Therefore, the surface water and sediment ingestion exposure pathway for site

workers and future construction workers is considered potentially complete. 

Drainage swales and wetlands leading to Pendleton River are located 0.25 miles to the south 

and topographically downgradient of the facility. However, the facility is located at a topographic 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 7-4

high with local surface runoff flowing toward the on-facility, unlined detention basins.

Additionally, Pendleton AASF #2 is located in the Upper Stage Gulch Watershed, and the 

southern drainages are located within the Upper Stage Gulch Watershed. Recreational and 

drinking source surface water bodies that may potentially receive runoff from the facility are 

greater than 15 miles from the facility boundary. Therefore, the surface water and sediment 

ingestion exposure pathway for off-facility residents and recreational users are considered 

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

7.3.2 AOI 2 

Because relevant compounds were detected in soil and groundwater at AOI 2, it is possible that 

those compounds may exist in occasionally ponded surface water within the northwestern 

detention basin. Therefore, the surface water and sediment ingestion exposure pathway for site 

workers and future construction workers is considered potentially complete.

The surface water and sediment ingestion exposure pathway for off-facility residents and 

recreational users are considered incomplete for the same reasons established for AOI 1. The 

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

7.3.3 AOI 3

Surface water bodies are not located in the vicinity of AOI 3. Therefore, the surface water and 

sediment ingestion exposure pathway for site workers and construction workers is considered 

incomplete.

The surface water and sediment ingestion exposure pathway for off-facility residents and 

recreational users are considered incomplete for the same reasons established for AOI 2. The 

CSM for AOI 3 is presented on Figure 7-3. 
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

Pendleton AASF #2, Pendleton, Oregon

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

2. Construction was not observed during SI field

activities.

NOTES

Storage

SOURCE PATHWAY RECEPTOR

AOI 1

AFFF Release

During Fire

Training

Activities

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

Pendleton AASF #2, Pendleton, 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

AFFF Release

and Storage

During Fire

Training

Activities

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

AOI 2

/ /

/ / / /

/

AECOM 7-6
Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

LEGEND

Figure 7-3

Conceptual Site Model, AOI 3

Pendleton AASF #2, Pendleton, 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

Potential 

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 Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Surface 

Water

Surface 

Water Flow

Surface Soil

Recreational 

User/Trespasser1

Site 

Worker

Construction 

Worker2 Resident1

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

AOI 3

/ / / /

/ / / /

/ / / /

/ / / /

/ / / /

Site 

Worker

Construction 

Worker2

Resident1 Recreational 

User/Trespasser1

AECOM 7-7
THIS PAGE INTENTIONALLY BLANK

AECOM 7-8
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, 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 29 August to 31 August, 1 September to 15 

September 2022 and consisted of utility clearance, sonic drilling, soil sample collection, temporary 

and permanent monitoring well installation, well development, grab groundwater sample 

collection, and land surveying. Field activities were conducted in accordance with the SI QAPP 

Addendum (AECOM, 2022a).

To fulfill the project DQOs set forth in the approved SI QAPP Addendum (AECOM, 2022a), 

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. 

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

• Thirty-six (36) soil samples from seven (7) sonic borings and nineteen (19) hand auger

locations;

• Four (4) grab groundwater samples from three (3) temporary well locations;

• Four (4) groundwater samples from four (4) permanent well locations; and

• Twenty (20) QA/QC samples.

An SI is conducted when the PA determines an AOI exists based on probable use, storage, 

and/or disposal of PFAS-containing materials. The SI includes multi-media sampling at AOIs to 

determine whether or not a release has occurred. The SI may conclude further investigation is 

warranted, a removal action is required to address immediate threats, or no further action is 

required. Additionally, the CSMs were refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at the AOIs, which are 

described in Section 7. 

8.2 Outcome 

Based on the results of this SI, further evaluation under CERCLA is warranted in an RI for AOI 

1, AOI 2, and AOI 3 (see Table 8-1). Based on the CSMs developed and revised in light of the 

SI findings, there is potential for exposure to drinking water receptors from sources on the

facility resulting from historical DoD activities and/or nearby adjacent sources. Sample analytical 

concentrations collected during the SI were compared against the project SLs in soil and

groundwater, as described in Table 6-1. A summary of the results of the SI data relative to the 

SLs is as follows: 

• At AOI 1:

• PFOS was detected above the 13 μg/kg SL, with a maximum concentration of 31.0

μg/kg in surface soil at location AOI01-06. All other relevant compounds in surface

soil were below their SLs. All relevant compounds were below SLs or not detected

in subsurface soil.
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• PFOA, PFOS, PFHxS, and PFNA in groundwater exceeded their SLs. PFOA

exceeded the 6 ng/L SL, with a maximum concentration of 7.84 J ng/L at AOI01-02;

PFOS exceeded the 4 ng/L SL, with a maximum concentration of 31.0 J ng/L at

AOI01-02; PFHxS exceeded the 39 ng/L SL, with a maximum concentration of 124

J ng/L at AOI01-02; PFNA exceeded the 6 ng/L SL, with a maximum concentration

of 12.1 ng/L at AOI01-02. PFBS was below the SL in groundwater.

• Based on the results of the SI, further evaluation of AOI 1 is warranted.

• At AOI 2:

• PFOA, PFOS, PFHxS, and PFNA were detected in surface soil, at concentrations

below their SLs. PFBS was not detected. Relevant compounds were not detected

in shallow subsurface soil.

• PFOA, PFOS, and PFHxS in groundwater exceeded their SLs. PFOA exceeded the

6 ng/L SL, with a maximum concentration of 18.1 ng/L at AOI02-01; PFOS

exceeded the 4 ng/L SL, with a maximum concentration of 6.67 ng/L at AOI02-02;

PFHxS exceeded the 39 ng/L SL, with a maximum concentration of 519 ng/L at

AOI02-01. PFBS and PFNA were below their SLs in groundwater.

• Well AOI02-02 is located along the facility boundary and is in the upgradient portion

of the facility based on the groundwater elevations measured during the SI,

indicating that there may be an adjacent, offsite source.

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

• At AOI 3:

• PFOA, PFOS, PFBS, PFHxS, and PFNA were detected in surface and shallow

subsurface soil, at concentrations below their SLs.

• PFOA, PFBS, and PFHxS were detected in groundwater, at concentrations below

their SLs. The maximum concentration of the three compounds was PFBS at 22.5

ng/L at AOI03-01. PFOS and PFNA were not detected in groundwater.

• While relevant compounds in soil and groundwater were detected below SLs at AOI

3, this AOI is located upgradient of AOI 1 and AOI 2, at which there were observed

exceedances. Due to this information, AOI 3 cannot be ruled out as a possible

contributing source to AOI 1 and AOI 2; therefore, further evaluation of AOI 3 is

warranted.

Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA 

(commonly referred to as GenX) was not included as an analyte at the time of this SI. Based on 

the CSM developed during the PA and revised based on SI findings, the presence of HFPO-DA 

is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC 

AFFF and based on its history including distribution limitations that restricted use of GenX, it is 

generally not a component of other products the military used. In addition, it is unlikely that 

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

Table 8-1 summarizes the SI results for soil and groundwater used to determine if an AOI 

should be considered for further investigation under CERCLA and undergo an RI. 
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Table 8-1: Summary of Site Inspection Findings and Recommendations

AOI Potential 

Release Area

Soil – 

Source Area

Groundwater – 

Source Area

Groundwater –

Facility 

Boundary

Future Action

1 Eastern 

Detention Basin Proceed to RI 

2 Ramp Area Proceed to RI

3 Readiness 

Center N/A Proceed to RI

Legend:

N/A = not applicable

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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9. References

AECOM. 2018a. Final Site Inspection Programmatic Uniform Federal Policy-Quality Assurance 

Project Plan, Perfluorooctane Sulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA) 

Impacted Sites ARNG Installations, Nationwide Contract No. W912DR-12-D-0014/

W912DR17F0192. 9 March.

AECOM. 2018b. Final Programmatic Accident Prevention Plan, Perfluorooctane Sulfonic Acid 

(PFOS) and Perfluorooctanoic Acid (PFOA) Impacted Sites ARNG Installations, Nationwide 

Contract No. W912DR-12-D-0014/W912DR17F0192. July.

AECOM. 2020. Final Preliminary Assessment Report, Pendleton AASF #2, Oregon, Pendleton, 

Oregon. May.

AECOM. 2022a. Final Site Inspection Uniform Federal Policy-Quality Assurance Project Plan 

Addendum, Army Aviation Support Facility #2, Pendleton, Oregon, Perfluorooctane Sulfonic 

Acid (PFOS) and Perfluorooctanoic Acid (PFOA) Impacted Sites ARNG Installations, 

Nationwide. August. 

AECOM. 2022b. Final Site Safety and Health Plan, Army Aviation Support Facility, Pendleton, 

Oregon, Perfluorooctane Sulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA) Impacted 

Sites ARNG Installations, Nationwide. August. 

Alford, J. 2015. Umatilla Zoning Map. Pendleton Oregon Planning and Zoning Map. 

https://pendleton.or.us/sites/default/files/fileattachments/community_development/page/1151

1/zoning_map_4_15_15_0.pdf 

Assistant Secretary of Defense. 2022. Investigation Per- and Polyfluoroalkyl Substances within 

the Department of Defense Cleanup Program. United States Department of Defense. 

6 July. 

Bonneville, A., Heggy, E., Strickland, C., Normand J., and Dermond J. Geophysical Monitoring 

of Ground Surface Deformation Associated with a Confined Aquifer Storage and Recovery 

Operation. Water Resources Management (2015) 29: 4667. https://doi.org/10.1007/s11269-

015-1083-y

City of Pendleton. 2023. City Information. https://pendleton.or.us/. (Accessed February 2023).

City of Pendleton. 2021. Water Utility: Pendleton’s Water Supply.

https://pendleton.or.us/sites/default/files/fileattachments/public_works/page/12761/cop_2021

_water_quality_report.pdf 

Columbia Plateau Ecoregion. 2019. Interior Low Plateau Ecoregion, Land Scope America. 

www.landscope.org/explore/natural_geographies/ecoregions/Columbia%20Plateau/

DA. 2018. Army Guidance for Addressing Releases of Per- and Polyfluoroalkyl Substances.

4 September.

DoD. 2019a. Department of Defense (DoD), Department of Energy (DOE) Consolidated Quality 

Systems Manual (QSM) for Environmental Laboratories, Version 5.3. 

DoD. 2019b. General Data Validation Guidelines. Environmental Data Quality Workgroup. 

4 November.

Dudek. 2018. Spill Prevention, Control, and Countermeasure Plan (40 CFR 112), Army Aviation 

Support Facility #2 Pendleton, Oregon. Prepared for Oregon Army National Guard. April 

2018.
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 9-2

EA Engineering, Science, and Technology, Inc. 2021. Standard Operating Procedure No. 042A 

for Treating Liquid Investigation-Derived Material (purge water, drilling water, and 

decontamination fluids). Revision 1. March.

Gonthier, J. 1985. A Description of Aquifer Units in Eastern Oregon. USGS WRIW-84-4095. 

https://pubs.er.usgs.gov/publication/wri844095

Guelfo, J.L. and Higgins, C.P. 2013. Subsurface Transport Potential of Perfluoroalkyl Acids at 

Aqueous Film-Forming Foam (AFFF)-Impacted Sites. Environmental Science and 

Technology 47(9): 4164-71.

Higgins, C.P., and Luthy, R.G. 2006. Sorption of perfluorinated surfactants on 

sediments. Environmental Science and Technology 40 (23): 7251-7256.

Hogenson G.M. 1964. Geology and Ground Water of the Umatilla River Basin Oregon. United 

States Geological Survey, Geology Survey Water-Supply Paper 1620.

ITRC. 2018. Environmental Fate and Transport for Per- and Polyfluoroalkyl Substances. March. 

McConnell, V.S. 2006. Preliminary geologic map of the Service Buttes, Echo, Nolin, Barnhart, 

and Pendleton 7.5' quadrangles (west to east), Umatilla County, Oregon. 

https://ngmdb.usgs.gov/Prodesc/proddesc_77365.htm

National Oceanic and Atmospheric Administration. 1991-2020. U.S. Climate Normals. 

Pendleton, Oregon. https://www.ncei.noaa.gov/access/us-climatenormals/#dataset=normals-monthly&timeframe=30&station=USW00024155. (6 January 

2023). 

Oregon Health Authority. 2023. Public Drinking Water Online. OR41 00617 Rieth Water District. 

https://yourwater.oregon.gov/inventory.php?pwsno=00617. (Accessed 20 February 2023).

Oregon Water Resources Department. 2023. Well Report Mapping Tool. 

https://apps.wrd.state.or.us/apps/gw/wl_well_report_map/Default.aspx. (Accessed 10 

February 2023).

USACE. 2016. Technical Project Planning Process, EM-200-1-2. 26 February.

US Climate Data. 2018. Pendleton Oregon Climate Data. 

https://www.usclimatedata.com/climate/pendleton/oregon/united-states/usor0267

USEPA. 1980. Comprehensive Environmental Response, Compensation, and Liability Act 

(CERCLA). 

USEPA. 1994. National Oil and Hazardous Substances Pollution Contingency Plan (Final Rule). 

40 CFR Part 300; 59 Federal Register 47384. September.

USEPA. 2001. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation 

Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk 

Assessments). December.

USEPA. 2017. National Functional Guidelines for Organic Superfund Data Review. OLEM 

9355.0-136, EPA-540-R-2017-002. Office of Superfund Remediation and Technology 

Innovation. January.

USGS. 2002. Open-File Report 03-67, Spatial Digital Database for the Geologic Map of Oregon. 

https://pubs.usgs.gov/of/2003/of03-067. 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

AECOM 9-3

USGS. 2016. Umatilla Basin Ground-Water Study. 

https://or.water.usgs.gov/proj/umatilla_gw/index.html. 

USGS. 2017. Hydrogeologic Framework and Selected Components of the Groundwater Budget 

for the Upper Umatilla River Basin, Oregon. 

https://pubs.er.usgs.gov/publication/sir20175020. 

USFWS. 2023. Species by County Report, County: Umatilla County, Oregon. Environmental 

Conservation Online System. Accessed 6 January 2023 at 

https://ecos.fws.gov/ecp/report/species-listings-by-current-range-county?fips=41059. 

Walker, G.W. 1973. Reconnaissance Geologic Map of the Pendleton Quadrangle, Oregon and 

Washington. https://pubs.er.usgs.gov/publication/i727. 

Walker, G.W. 1977. Geologic Map of Oregon East of the 121st Meridian. 

https://ngmdb.usgs.gov/Prodesc/proddesc_9795.htm. 

Walker, G. 1990. Geology of the Blue Mountains Region of Oregon, Idaho, and Washington: 

Cenozoic Geology of the Blue Ridge Mountains Region. USGS Professional Paper 1437.

Winterbrook Planning. 2012. Local Wetland Inventory Report. Pendleton, Oregon. Prepared for 

City of Pendleton. September.

Xiao, F., Simcik, M. F., Halbach, T. R., and Gulliver, J. S. 2015, Perfluorooctane sulfonate 

(PFOS) and perfluorooctanoate (PFOA) in soils and groundwater of a U.S. metropolitan 

area: Migration and implications for human exposure. Water Research 72: 64-74. 
Site Inspection Report

Army Aviation Support Facility #2, Pendleton, Oregon

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