FINAL

Site Inspection Report 

Fort William Henry Harrison

Helena, Montana

Perfluorooctanesulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites

ARNG Installations, Nationwide

August 2021

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED
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Table of Contents

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

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

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

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

2. Site Background ...........................................................................................................2-1

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

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

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

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

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

2.2.4 Climate........................................................................................................2-3

2.2.5 Current and Future Land Use......................................................................2-3

2.3 History of AFFF Use..............................................................................................2-4

2.4 Drinking Water Sampling.......................................................................................2-4

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

3.1 AOI 1.....................................................................................................................3-1

3.1.1 Black-Tailed Prairie Dog Relocation ............................................................3-1

3.1.2 MTARNG 1049th Engineer Detachment (Building 1010).............................3-1

3.1.3 Mt. Defensa Avenue Drainage Ditch............................................................3-2

3.1.4 MTARNG 1049th Firefighting Training Area 1 and 3....................................3-2

3.2 AOI 2.....................................................................................................................3-2

3.2.1 Excavated Soil from Mt. Defensa Avenue Drainage Ditch ...........................3-3

3.2.2 Former Weasel Barn ...................................................................................3-3

3.2.3 MTARNG 1049th Engineer Detachment (Building M1)................................3-3

3.2.4 MTARNG 1049th Firefighting Training Area 4..............................................3-3

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

3.3.1 Planned Fire Structure ................................................................................3-3

3.3.2 Burial Trench...............................................................................................3-3

3.3.3 MTARNG 1049th Firefighting Training Area 2..............................................3-4

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

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

4.2 Goals of the Study.................................................................................................4-1

4.3 Information Inputs .................................................................................................4-2

4.4 Study Boundaries..................................................................................................4-2

4.5 Analytical Approach...............................................................................................4-2

4.6 Data Usability Assessment....................................................................................4-3

4.6.1 Precision .....................................................................................................4-3

4.6.2 Accuracy .....................................................................................................4-4

4.6.3 Representativeness ....................................................................................4-5

4.6.4 Comparability ..............................................................................................4-6

4.6.5 Completeness .............................................................................................4-6

4.6.6 Sensitivity....................................................................................................4-6

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

5.1 Pre-Investigation Activities.....................................................................................5-2

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

5.1.2 Utility Clearance..........................................................................................5-2
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5.1.3 Source Water and PFAS Sampling Equipment Acceptability .......................5-2

5.2 Soil Borings and Soil Sampling .............................................................................5-3

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

5.4 Groundwater Sampling from Existing Wells...........................................................5-4

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

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

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

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

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

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

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

6.2 Soil Physicochemical Analyses .............................................................................6-1

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

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

6.3.2 AOI 1 Groundwater Analytical Results.........................................................6-3

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.........................................................6-4

6.4.3 AOI 2 Conclusions ......................................................................................6-4

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

6.5.1 AOI 3 Soil Analytical Results .......................................................................6-5

6.5.2 AOI 3 Groundwater Analytical Results.........................................................6-5

6.5.3 AOI 3 Conclusions ......................................................................................6-5

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

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

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

8.2 SI Goals Evaluation...............................................................................................8-1

8.3 Outcome ...............................................................................................................8-3

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

Appendix A Data Validation Reports

Appendix B Field Documentation

B1. Log of Daily Notice of Field Activities

B2. Sampling Forms

B3. Field Change Request Forms

B4. Survey Data

Appendix C Photographic Log

Appendix D TPP Meeting Minutes/Montana DEQ Memorandum

Appendix E Boring Logs and Well Construction Diagrams

Appendix F Analytical Results

Appendix G Laboratory Reports

Figures

Figure 2-1 Facility Location

Figure 2-2 Groundwater Features

Figure 2-3 Groundwater Elevation Contours, May 2019

Figure 2-4 Groundwater Elevation Contours, October 2020

Figure 2-5 Surface Water Features

Figure 3-1 Areas of Interest

Figure 5-1 SI Mobilization 1 Sample Locations

Figure 5-2 SI Mobilization 2 Sample Locations

Figure 6-1 PFOS Detections in Soil During SI Mobilization 1 (AOI 1-3)

Figure 6-2 PFOA Detections in Soil During SI Mobilization 1 (AOI 1-3)

Figure 6-3 PFOS Detections in Soil During SI Mobilization 2 (AOI 1-3)

Figure 6-4 PFOA Detections in Soil During SI Mobilization 2 (AOI 1-3)

Figure 6-5 PFOA and PFOS Detections in Groundwater During SI Mobilization 1 (AOI

1-3) May 25-30, 2019

Figure 6-6 PFOA and PFOS Detections in Groundwater During SI Mobilization 2 (AOI

1-3) October 9-14, 2020

Figure 7-1 Conceptual Site Model, AOI 1 Mt. Defensa Avenue Drainage Ditch

Figure 7-2 Conceptual Site Model, AOI 2 Cantonment Area Northeast

Figure 7-3 Conceptual Site Model, AOI 3 Cantonment Area Northwest

Tables

Table ES-1 Screening Levels (Soil and Groundwater)

Table ES-2 Summary of Site Inspection Findings

Table ES-3 Site Inspection Recommendations

Table 2-1 Residential Drinking Water Results

Table 5-1 Samples by Medium

Table 5-2 Monitoring Well Screen Intervals

Table 5-3 Groundwater Elevation

Table 6-1 Screening Levels (Soil and Groundwater)

Table 6-2 PFAS Detections in Surface Soil

Table 6-3 PFAS Detections in Shallow Subsurface Soil

Table 6-4 PFAS Detections in Deep Subsurface Soil

Table 6-5 PFAS Detections in Groundwater

Table 8-1 Summary of Site Inspection Findings

Table 8-2 Site Inspection Recommendations
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Acronyms and Abbreviations

6:2 FTS 6:2 Fluorotelomer sulfonate

8:2 FTS 8:2 Fluorotelomer sulfonate

μg/kg micrograms per kilogram

μg/L micrograms per liter

°C degrees Celsius

°F degrees Fahrenheit

AECOM AECOM Technical Services, Inc.

AFFF aqueous film forming foam

amsl above mean sea level

AOI Area of Interest

Argonne Argonne National Laboratory

ARNG Army National Guard

ATSDR Agency for Toxic Substances and Disease Registry

bgs below ground surface 

CDM Camp Dresser, and McKee

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CFR Code of Federal Regulations

COC chain-of-custody

CSM conceptual site model

DA Department of the Army

DASA ESOH Deputy Assistant Secretary of the Army for Environment, Safety and Occupational 

Health

DO dissolved oxygen

DoD Department of Defense

DPW Department of Public Works

DRFS Dominion Restoration’s Foaming Surfactant

DQI data quality indicator

DQO Data Quality Objective

DRFS Dominion Restoration’s Foaming Surfactant

DUA data usability assessment

EIS extracted internal standard

ELAP Environmental Laboratory Approval Program

FRB Field Reagent Blank

FTA firefighting training area

FTWHH Fort William Henry Harrison 

GCAL Gulf Coast Analytical Laboratories, LLC

HA Health Advisory

HDPE high-density polyethylene 

HSA hollow stem auger

IDW investigation-derived waste

ITRC Interstate Technology Regulatory Council

LC/MS/MS liquid chromatography with tandem mass spectrometry

LCS laboratory control spike

LCSD laboratory control spike duplicate
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LOD level of detection

LOQ level of quantitation

MBMG Montana Bureau of Mines and Geology

MDL method detection limit

mph miles per hour

MS matrix spike

MSD matrix spike duplicate

MTARNG Montana Army National Guard

MTDEQ Montana Department of Environmental Quality

NELAP National Environmental Laboratory Accreditation Program

NEtFOSAA N-ethyl perfluorooctanesulfonamidoacetic acid

ng/L nanograms per liter

NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

ORP oxidation reduction potential

OSD Office of the Secretary of Defense

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutyrate

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUdA perfluoroundecanoic acid

PID photoionization detector

PPE personal protective equipment

PQAPP Programmatic UFP-QAPP

PRC PRC Environmental Management, Inc.

PVC polyvinyl chloride

QAPP Quality Assurance Project Plan

QC quality control

QSM Quality Systems Manual

RI Remedial Investigation

RPD relative percent differences

SI Site Inspection

SL screening level

TOC total organic carbon

TPP Technical Project Planning

UFP Uniform Federal Policy
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US United States

USACE United States Army Corps of Engineers

USCS Unified Soil Classification System

USGS United States Geological Survey

USEPA United States Environmental Protection Agency

VA Veterans Administration
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Executive Summary

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

Inspections (SIs) at per- and polyfluoroalkyl substances (PFAS)-impacted sites at ARNG facilities 

nationwide. The objective of the SI at each facility is to identify whether there has been a release 

to the environment from the Areas of Interest (AOIs) identified in the PA and determine the 

presence or absence of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and 

perfluorobutanesulfonic acid (PFBS) at or above screening levels (SLs), as well as the presence 

or absence of an additional 15 PFAS. An SI was completed at Fort William Henry Harrison 

(FTWHH) in Helena, Montana. FTWHH will be referred to as the ‘facility’ throughout this 

document. 

FTWHH is in Lewis and Clark County, approximately 4 miles west of the state capitol of Helena, 

Montana. The facility is bounded by the Scratchgravel Hills to the north, the Spokane Bench to

the east, the Elkhorn Mountains to the south, and the General Eisenhower Mountains to the west. 

During the PA, ten potential PFAS release areas were grouped into three AOIs (AOI 1 through 3).

Results from the first mobilization performed in 2019 identified three additional release areas that 

potentially exist at the facility and one directly off-site across Williams Street. SI field activities

were conducted in two mobilizations. The first mobilization included permanent groundwater 

monitoring well installation, development, and sampling; surface and subsurface soil sampling; 

and groundwater sampling from existing wells from 10 to 20 February 2019 and from 19 to 31

May 2019. The second mobilization included permanent groundwater monitoring well installation, 

development, and sampling; surface and subsurface soil sampling; and groundwater sampling 

from existing wells from 5 to 15 October 2020. 

To fulfill the project Data Quality Objectives (DQOs) set forth in the approved SI Quality Assurance 

Project Plan (QAPP) Addendum (AECOM, 2019), samples were collected and analyzed for a 

subset of 18 PFAS by liquid chromatography with tandem mass spectrometry (LC/MS/MS)

compliant with Quality Systems Manual (QSM) 5.1 Table B-15. The 18 PFAS analyzed as part of 

the ARNG SI program are specific in Section 5.8 of this Report.

The Department of Defense (DoD) has adopted a policy to retain facilities in the Comprehensive 

Environmental Restoration, Compensation, and Liability Act (CERCLA) process based on riskbased SLs for soil and groundwater, as described in a memorandum from the Office of the 

Secretary of Defense (OSD) dated 15 October 2019 (Assistant Secretary of Defense, 2019). The 

ARNG PFAS SIs follow this DoD policy and, when the maximum site concentration for sampled 

media exceed the SLs, the AOI will proceed to a Remedial Investigation (RI), the next phase 

under CERCLA. The SLs apply to three compounds, PFOA, PFOS, and PFBS, for both soil and 

groundwater, as presented in Table ES-1. All other results presented in this report are considered 

informational in nature and serve as an indication as to whether soil and groundwater contain or 

do not contain the 18 PFAS analyzed within the boundaries of the facility. 

Sample chemical analytical concentrations were compared against the project SLs as described 

in Table ES-1. A summary of the results of the SI data relative to the SLs is as follows: 

• PFOS was detected in groundwater at 62.2 nanograms per liters (ng/L) at AOI1-MW3 in 

excess of the SL. Based on the results of the SI, further evaluation of AOI 1 is warranted 

in the RI. 

• PFOS was detected in groundwater at 118 ng/L at AOI2-MW1 in excess of the SL. Based 

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

• Additional offsite residential drinking water sampling is recommended due to the SL 

groundwater exceedance of PFOS at AOI 1 and AOI 2.
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• The detected concentrations of PFOA, PFOS, and PFBS in soil samples from all AOIs 

were below the SLs.

Tables ES-2 summarizes the SI results for soil and groundwater. Based on the conceptual site 

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

to residential drinking water receptors caused by DoD activities at or adjacent to the facility.

Table ES-3 summarizes the rationale used to determine if an AOI should be considered for further 

investigation under CERCLA and undergo an RI. Based on the results of this SI, further evaluation 

is warranted in the RI for AOI 1 and AOI 2.
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Table ES-1 Screening Levels (Soil and Groundwater)

Analyte

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 130 1,600 40

PFOS 130 1,600 40

PFBS 130,000 1,600,000 40,000

Notes:

a.) Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in 

Groundwater and Soil using United States Environmental Protection Agency’s (USEPA’s) Regional Screening 

Level Calculator. HQ=0.1. 15 October 2019.

Table ES-2 Summary of Site Inspection Findings

AOI Potential PFAS Release Area Soil – Source 

Area

Groundwater

– Source Area

Groundwater –

Facility Boundary

1 Mt. Defensa Avenue Drainage Ditch

1 1049th Engineer Detachment Building 

1010 NA

1 Prairie Dog Relocation (three 

locations)

NA NA

1 1049th Firefighting Training Area 1 NA

1 1049th Firefighting Training Area 3 NA NA

1 MacDonald Property NA

2 Former Weasel Barn

2 Excavated Soil from Mt. Defensa Ave 

Drainage Ditch

2 1049th Engineer Detachment Building 

M1

2 1049th Firefighting Training Area 4 NA

3 Planned Structure Fire NA

3 Burial Trench NA NA

3 1049th Firefighting Training Area 2 NA

Legend:

NA = Not applicable (samples not at facility boundary)

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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Table ES-3 Site Inspection Recommendations

AOI Description Rationale Future Action

1

Mt. Defensa Avenue Drainage 

Ditch, 1049th Engineer 

Detachment Building 1010, 

1049th Firefighting Training 

Area 1, 1049th Firefighting 

Training Area 3

No exceedances of SL in 

groundwater at the source area; 

however, exceedances of SLs in 

groundwater at the facility boundary. 

No exceedances of SLs in soil.

Proceed to RI

1 Prairie Dog Relocation (Three 

Release Areas) No exceedances of SLs in soil. No further action

2

Former Weasel Barn, 

Excavated Soil from Mt. 

Defensa Ave Drainage Ditch, 

1049th Firefighting Training 

Area 4

No exceedances of SL in 

groundwater at the source area; 

however, exceedances of SLs in 

groundwater at the facility boundary. 

No exceedances of SLs in soil.

Proceed to RI

2 1049th Engineer Detachment 

Building M1

No exceedances of SLs in 

groundwater or soil. No further action

3

Planned Structure Fire, Burial 

Trench, and 1049th Firefighting 

Training Area 2

No exceedances of SLs in 

groundwater or soil. No further action
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1. Introduction

1.1 Project Authorization

The Army National Guard (ARNG) G9 is the lead agency in performing Preliminary Assessments 

(PAs) and Site Inspections (SIs) for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic 

acid (PFOA) at Impacted Sites, ARNG Installations, Nationwide. This work is supported by the 

United States (US) Army Corps of Engineers (USACE) Baltimore District and their contractor,

AECOM Technical Services, Inc. (AECOM), under Contract Number W912DR-12-D-0014, Task 

Order W912DR17F0192, issued 11 August 2017. The ARNG performed this SI at Fort William 

Henry Harrison (FTWHH) in Helena, Montana. FTWHH will be 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 [CFR] Part 300; USEPA, 1994), and 

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

investigations including specific requirements for sampling for PFOA, PFOS, and 

perfluorobutanesulfonic acid (PFBS), and the group of related compounds known in the industry 

as per- and polyfluoroalkyl substances (PFAS). The term PFAS will be used throughout this report 

to encompass all PFAS chemicals being evaluated, including PFOA, PFOS, and PFBS, which are 

the key components of the suspected releases being evaluated, and the other 15 related 

compounds listed in the task order. 

1.2 SI Purpose

A PA was performed at FTWHH (AECOM, 2018c) that identified ten potential PFAS release areas 

which were grouped into three Areas of Interest (AOIs). Results from the first mobilization 

performed in 2019 identified three additional release areas potentially existed at the facility and 

one directly off-site across Williams Street. The objective of the SI is to identify whether there has 

been a release to the environment from the AOIs and determine the presence or absence of 

PFOA, PFOS, and PFBS at or above screening levels (SLs). 

As stated in the Federal Facilities Remedial Site Inspection Summary Guide (USEPA, 2005), an 

SI has five goals: 

1) Develop information to potentially eliminate a release from further consideration because 

it is determined that it poses no significant threat to human health or the environment.

2) Determine the potential need for a removal action.

3) Collect or develop data to evaluate potential release.

4) Collect data to better characterize the release for more effective and rapid initiation of a 

Remedial Investigation (RI).

5) Collect data to determine whether the release is more than likely the result of activities 

associated with the Department of Defense (DoD).

In addition to the USEPA-identified goals of an SI, the ARNG SI also identifies whether there are 

potential offsite PFAS sources. 
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2. Site Background

2.1 Facility Location and Description

FTWHH is in Lewis and Clark County, approximately 4 miles west of the state capitol of Helena, 

Montana (Figure 2-1). The facility houses the headquarters of the Montana ARNG (MTARNG)

and occupies 6,717 acres. 

FTWHH was authorized by an act of Congress in 1892 and was constructed between 1894 and 

1896 (Argonne National Laboratory [Argonne], 1993). In 1903, the War Department changed the 

installation’s name from Fort Benjamin Harrison to Fort William Henry Harrison. The MTARNG 

began using FTWHH for training in 1911; however, FTWHH remained an active US Army post 

until 1913 (MTARNG, 2001; Argonne, 1993). In 1913, FTWHH was placed in caretaker status by 

the US Army and was periodically occupied by the MTARNG until 1919 (MTARNG, 2001). In 1919, 

the US Public Health Service took possession of the facility and began to operate a hospital, 

which is currently under the jurisdiction of the Federal Government and is operated by the 

Veterans Administration (VA). From 1924 to 1928, the State of Montana expanded the facility area 

by leasing surrounding land. The MTARNG was absent from the facility from 1940 to 1946. During 

that time, the US Army assumed control and used FTWHH as a training base and further 

expanded the facilities. FTWHH has been used for training by the MTARNG since 1947 (Argonne,

1993). FTWHH was under the jurisdiction of the Federal Government until 1966, when it was 

converted to a training site for ARNG, transferring management to the Montana Department of 

Military Affairs. The current lease, which began in 1986, extended the lease for an indefinite term.

2.2 Facility Environmental Setting

FTWHH is within the Northern Rocky Mountain physiographic province on the western edge of 

Helena Valley (PRC Environmental Management, Inc. [PRC] 1996). Helena Valley is a northwesttrending, oval shaped basin that is approximately 875 square miles and is surrounded by 

mountains (MTARNG 2001). The facility is bounded by the Scratchgravel Hills to the north, the 

Spokane Bench to the east, the Elkhorn Mountains to the south, and the General Eisenhower 

Mountains to the west (MTARNG 2001; PRC 1996). Elevations at FTWHH range from 5,318 feet 

above mean sea level (amsl) at the western boundary to approximately 4,060 feet amsl in the 

northeast corner (Camp Dresser, and McKee [CDM], 2006). The Continental Divide is 

approximately 5 miles west of the facility (MTARNG, 2001).

2.2.1 Geology

Helena Valley is bounded by folded and fractured sedimentary, metamorphic, and igneous 

bedrock of Precambrian to Cretaceous age (US Geological Survey [USGS], 1992). The valley fill 

has been mapped with thicknesses of up to 6,000 feet with source materials consisting of fineand coarse-grained Tertiary materials. The valley fill is unconformably overlain by up to 100 feet 

of Quaternary alluvium (Montana Department of Environmental Quality [MTDEQ], 2006). 

FTWHH is on gently sloping pediment gravels at the base of General Eisenhower Mountains

between two principal streams flowing into Helena Valley: Sevenmile Creek to the north and 

Tenmile Creek to the south (MTARNG 2001; CDM 2006). Quaternary alluvial deposits form the 

uppermost unit (Figure 2-2). The thickness of the alluvial deposits is highly variable and is 

predominantly thicker in the northern half of the facility (MTARNG, 2001). The gravel layers of the 

alluvium are made up of fragments of quartzite, shale, and limestone between layers of clay and 

silt (MTARNG, 2001). 

Precambrian rocks crop out in the hills and mountains to the south, west, and north of FTWHH

and underlie it at depths ranging from 80 to 100 feet. The Precambrian bedrock consists mainly 
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of argillite, feldspathic quartzite, limestone, and dolomite of the Empire and Helena formations 

and members of the Missoula Group (Argonne, 1993).

2.2.2 Hydrogeology

Stratified lenses of cobbles, gravel, and sand form the primary Helena Valley aquifer. The water 

bearing zones, intercalated clay, and silt compose the upper few hundred feet of the valley fill. 

Discontinuity of the clay and silt deposits allows for hydraulic connection of the water bearing 

zones to make up a single complex aquifer (USGS, 1992). The estimated transmissivity of the 

water bearing zones is 10,000 square feet per day (Argonne, 1993). 

The principal water bearing zones at FTWHH are Quaternary alluvium and Tertiary pediments 

deposits. The unconfined Quaternary aquifer attains a maximum saturated thickness of about 70 

feet in the southern half of the facility and is largely absent near the northeastern corner (Argonne,

1993).

The depth to groundwater at the facility is typically between 14 and 43 feet below ground surface 

(bgs). In 1992, the USGS estimated that 60% of the wells near the facility are drilled to 70 feet 

bgs or less. 

Regionally, groundwater in the Helena Valley aquifer flows from the south, west, and north 

margins of the valley toward the northeast corner of the Helena Valley basin (USGS, 1992) and

Lake Helena (Figure 2-2). Locally at FTWHH, the groundwater flow direction is predominantly to 

the east in the southern half of the installation and to the east-southeast in the northern part of 

the installation (MTDEQ, 2006). Depth to water measurements from the May 2019 and October 

2020 synoptic gauging event were used to calculate groundwater elevations. The groundwater 

contours for May 2019 and October 2020 are shown in Figure 2-3 and Figure 2-4, respectively.

Recharge to the Helena Valley aquifer is through infiltration of streamflow and precipitation, 

leakage from irrigation canals, infiltration of excess irrigation water, and inflow from underlying 

bedrock fractures (USGS, 1992). Lake Helena is the primary point for surface water and 

groundwater discharge from the basin. Discharge also occurs to stream and irrigation canals and 

withdrawals from wells (USGS, 1992). 

Although it is outside Helena city limits, FTWHH draws from the City of Helena water supply. The 

city uses a combination of groundwater and surface water (the Missouri River and Tenmile Creek) 

as sources for its residents (Helena Water Utilities Public Water System, 2004; Department of 

Public Works [DPW], 2012). The Eureka Well is the source of potable water for FTWHH and is 

approximately 3 miles southeast of the facility, in the downtown Helena area (DPW, 2012). 

According to the 2018 Consumer Confidence Report (DPW, 2012), the Eureka Well is a pure 

groundwater source that requires no further treatment. In addition, the City of Helena was selected 

to participate in the Third Unregulated Contaminant Monitoring Rule assessment monitoring, and 

no PFAS were detected for Helena, Montana. A search of the Montana Bureau of Mines and 

Geology (MBMG) Groundwater Information System confirmed the presence of domestic water 

supply wells adjacent to FTWHH (MBMG, 2018). Residential lots east of Williams Street were 

identified as having private wells.

2.2.3 Hydrology

FTWHH is within the Sevenmile Creek watershed (CDM, 2006) (Figure 2-5). Three perennial 

streams and a number of intermittent streams that originate in the foothills west of the facility flow 

through the facility (Argonne, 1993; CDM, 2006). Cherry Creek is a perennial stream that flows 

east through training and maneuver areas at FTWHH (MTARNG, 2001). Granite Creek is a 

perennial tributary of Sevenmile Creek that flows northeast through the northern third of the facility 

(MTARNG, 2001). Blue Cloud Creek, a perennial tributary of Tenmile Creek, crosses the extreme 

southwestern corner of the facility, and drains an area of undeveloped land on the western and 
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southwestern side (MTARNG, 2001; CDM, 2006). Blue Cloud Creek and Granite Creek do not 

drain the Cantonment Area. The rest of the streams on FTWHH are intermittent and occur during

heavy rainfall or rapid snowmelt.

Sevenmile Creek and Tenmile Creek are the largest perennial streams near the facility (CDM,

2006). Sevenmile Creek joins Tenmile Creek about 1 mile east of the downstream property 

boundary (Argonne, 1993; CDM, 2006). The water diverted upgradient of FTWHH from the upper 

Tenmile Creek watershed provides about 70% of the municipal supply for Helena from June 

through September, and 100% of the city supply from October through May (USGS, 2000). 

Streamflow in the lower Tenmile Creek, which runs south of FTWHH, is partly controlled by two 

small municipal-supply reservoirs (Scott and Chessman) in the upper Tenmile Creek watershed 

and by diversions for municipal water supply and irrigation (USGS, 2001). In addition, a 30-acre 

spring-fed man-made lake exists approximately 1 mile southeast of the facility within Spring 

Meadow State Park. The lake is a popular swimming, fishing, and recreational area for Helena 

residents.

A large, unnamed drainage ditch runs from west to east through the VA property adjacent to 

FTWHH, along Mt. Defensa Avenue, and offsite by the Main Gate. For the purposes of this report, 

this drainage ditch will be referred to as the Mt. Defensa Avenue Drainage Ditch. Precipitation, 

snow melt, and other surface runoff on the VA property and much of the Cantonment Area is 

captured in the Mt. Defensa Avenue Drainage Ditch, which flows to the Main Gate on Williams 

Street and offsite. During rapid snow melt or high intensity rain events, runoff is channelized and 

flows rapidly through the ditch and Cantonment Area discharging just outside the Main Gate of 

the facility. As a result of the high velocity flow, limited runoff infiltrates into the subsurface of Mt. 

Defensa Avenue Drainage Ditch itself. Surface water runoff that reaches the Main Gate dissipates 

and infiltrates the subsurface and may reach groundwater. 

2.2.4 Climate

The climate at FTWHH is semiarid (USGS, 1992). In December, the average temperature is 32

degrees Fahrenheit (°F). July and August have the highest average temperatures, at 86°F and 

85°F, respectively. The greatest mean monthly precipitation occurs in June, and the greatest mean 

monthly snowfall occurs in January (World Climate, 2019). The average annual precipitation is 

12.12 inches at the Helena Regional Airport weather station, approximately 6 miles southeast of 

the facility. 

The area is subject to hailstorms. Flash flooding can occur in the Helena Valley during heavy 

rainstorms and rapid snowmelt (Argonne, 1993). The frost-free period is usually from May to 

September. Winds generally blow westerly at about 7 to 8 miles per hour (mph), and stronger 

gusts can reach 55 to 65 mph (MTARNG, 2001). Brisk westerly and northwesterly winds are 

common, particularly in the late winter and early spring. Chinook winds, which produce warmer 

temperatures in the winter months, are also common (Argonne, 1993).

2.2.5 Current and Future Land Use

FTWHH contains a cantonment area with dining and support facilities and five training range 

areas for the ARNG, the US Armed Forces, and other government and civilian organizations to 

practice combat skills and operations; access to the facility is controlled. The VA controls property 

immediately adjacent to the south and west of the Cantonment Area. Land use to the east, west, 

and north of the facility is primarily agricultural with scattered farms and residences, grazing land, 

and hilly to mountainous terrain. Land use to the south is a mixture of residential and agricultural.

The nearest urban area is Helena. According to the 2016 US Census, the estimated population 

of Helena is 31,169 (US Census Bureau, 2016). Helena has experienced significant population 

growth over the last decade, and several agricultural lands have been converted to residential 

subdivisions and single-resident lots to accommodate the growth (MTARNG, 2001). Lands to the 
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 2-4

east and north of FTWHH are designated as urban growth areas for Lewis and Clark County. 

Land use to the south and west is not expected to change.

The influx of people and need for new housing in the vicinity of FTWHH has created the possibility 

of encroachment or intrusion on the land or property owned by the MTARNG (Nakata Planning 

Group, LLC, 2000). In 2015, the Prickly Pear Land Trust acquired 558 acres in the area east of 

Williams Street in partnership with FTWHH with funding from the Army Compatible Use Buffer 

Program to address the encroachment concerns. This land is designated for open space and 

habitat (Westech Environmental Services, Inc., 2017).

2.3 History of AFFF Use

Ten potential PFAS release areas, where aqueous film forming foam (AFFF) may have been used 

or released historically, were identified at FTWHH during the PA (AECOM, 2018c). The potential 

PFAS release areas were grouped into three AOIs based on proximity to one another and 

presumed groundwater flow. A description of each AOI is presented in Section 3. Findings from 

the PA indicated AFFF use at the facility primarily ranged from the late-1980s to the early-2000s. 

AFFF was historically used by the MTARNG during fire training activities (planned structural fires 

and training exercises) and pest removal activities (prairie dog relocation). AFFF was stored in 

several buildings at the facility during this time, but no releases were documented in these areas.

2.4 Drinking Water Sampling

Due to historical fire training activities completed with AFFF, the potential exists for exposure to 

offsite residential drinking water receptors immediately east of the FTWHH boundary. Prior to 

sampling, approval was obtained from the Deputy Assistant Secretary of the Army for 

Environment, Safety and Occupational Health (DASA ESOH). Drinking water samples were 

collected from five potable wells located in closest proximity to the facility boundary (downgradient 

of AOI 1). No drinking water samples were collected downgradient of AOI 2 and AOI 3 because

no residential properties exist at the facility boundary. Sample results are provided below and in 

Table 2-1: 

• PFOA – Detections ranged from 3.75 nanogram per liter (ng/L) (Potable-02) to 16.6 ng/L

(Potable-05).

• PFOS – Detections ranged from 3.11 ng/L (Potable-02) to 22.1 ng/L (Potable-05).

• PFBS – Detections ranged from 2.48 ng/L (Potable-04) to 21.2 ng/L (Potable-05).
CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

JH

5/20/2021

5/20/2021

NOTES Site Inspection for PFAS at Fort William Henry Harrison, MT

5/20/2021

1:63,360 ­ Figure 2-1

PM CM 5/20/2021

C:\Users\stankevichm\OneDrive - AECOM Directory\ARNG_PFAS_GIS_60552172\MXDs\MT\FTWHH\FTWHH_SI\SI_Report\Fig_2-1_FTWHH_Facility_Location.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Facility Location

^_

Base Map: Copyright:© 2013 National Geographic

Society, i-cubed

0 0.5 1 2

Miles

Legend

Facility Boundary

Fort William Henry Harrison

Veterans Administration

2-5
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 2-6

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Veterans Administration

Fort William Henry Harrison

Mt. Defensa Avenue Drainage Ditch

Sweeney Creek

Greenhorn C reek

C herry Creek

Park Creek

Blue Cloud Creek

Wi llowCreek

0 4,000 8,000 16,000

Feet

Legend

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Pipeline

Groundwater Flow

Direction

Geology

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Carbonate

fine-grained mixed

clastic

medium-grained

mixed clastic

Meta-Argillite

quartz monzonite

quartzite

sandstone

volcanic rock

(aphanitic)

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!P Domestic Well

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Figure 2-2

CLIENT

REVISED

SCALE

6/7/2021 MS

JH

6/7/2021

6/7/2021

ARNG

GIS BY

CHK BY

TITLE

PROJECT Site Inspection for PFAS at Fort William Henry Harrison, MT

Q:\Projects\ENV\GEARS\GEO\MAES 2012 Unrestricted\Fort Meade\E. Data Management\GIS\MXDs\Chisholm_6th\March2017\ Fig_2-2_FTWHH_Groundwater_Features.mxd

Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, PM CM 6/7/2021

1:106,175 ­ 12420 Milestone Center Drive

Germantown, MD 20876

2-7
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 2-8

THIS PAGE INTENTIONALLY BLANK
A! A!

A!

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3944.47

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3916.31

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3929.73

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3932.41

AOI1-MW1

3954.67

BH-02

3944.02

FH-02

3920.78

OBTMW-01

3954.66

MW-10

3947.23

MW-08

3931.98

MW-06

3931.90

MW-07

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MW-11

3953.38

PH-1

Cherry Creek

Mt. Defensa Avenue

Drainage Ditch

3940

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A! Monitoring Well

!5 Existing Pumphouse Well

Facility Boundary

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(dashed where inferred)

Groundwater Flow Direction

River/Stream

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

JH

6/7/2021

6/7/2021

NOTES Site Inspection for PFAS at Fort William Henry Harrison, MT

1:9,600

6/7/2021 ­ Figure 2-3

PM CM 6/7/2021

C:\Users\stankevichm\OneDrive - AECOM Directory\ARNG_PFAS_GIS_60552172\MXDs\MT\FTWHH\FTWHH_SI\SI_Report\Fig_2-3_FTWHH_Groundwater_Contours_May2019.mxd

12420 Milestone Center Drive

Germantown, MD 20876

Groundwater Elevation Contours, 

May 2019

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

Geographics, CNES/Airbus DS, USDA, USGS,

0 400 800 1,600

Feet

2-9
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 2-10

THIS PAGE INTENTIONALLY BLANK
A! A!

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3928.047

AOI03-SB1

3959.505

AOI02-SB2

3929.317

AOI01-SB1

3951.218

BH-02

3940.478

FH-02

3920.52

OBTMW-01

3952.919 MW-10

3947.023 MW-08

3930.277

MW-06

3929.016

MW-07

3929.022

MW-11

3951.911

AOI01-MW04

3946.055

AOI01-MW05

3913.781

AOI01-MW06

3918.272

AOI02-MW03

3929.176

AOI03-MW02

3943.691

Cherry Creek

Mt. Defensa Avenue

Drainage Ditch

3960

3955

3915

3920

3925

3950

3930

3935

3950

3925

3945

3940

3945

3935

3930

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12420 Milestone Center Drive

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Surface Water Features

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Table 2-1

PFAS Detections in Residential Drinking Water

Site Inspection Report, Fort William Henry Harrison

Analyte EPA HA a Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS - 7.31 J 4.23 J 4.31 J 2.55 J 2.48 J 21.2 20.6

PFHpA - 10.2 3.82 J 4.05 J 5.77 J 3.81 J 20.9 19.1

PFHxA - 30.2 13.4 14.2 14.4 10.0 54.1 53.2

PFHxS - 59.8 24.3 24.6 19.1 14.6 182 186

PFOA 70 6.46 J 3.75 J 4.41 J 6.87 J 7.76 J 16.6 16.5

PFOS 70 17.0 3.11 J 3.15 J 15.4 13.3 19.5 22.1

Total PFOA+PFOS 70 23.5 6.86 7.56 22.3 21.1 36.1 38.6

Grey Fill Detected concentration exceeded EPA HA Chemical Abbreviations

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHpA perfluoroheptanoic acid

References PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Acronyms and Abbreviations

DUP Duplicate

Interpreted Qualifiers EPA United States Environmental Protection Agency

J = Estimated concentration HA Health Advisory

Qual Interpreted Qualifier

ng/L nanogram per liter

- Not applicable

Area of Interest

Sample ID

POTABLE

POTABLE-05

03/16/2020

POTABLE-05-DUP

03/16/2020

POTABLE-03

12/03/2019

POTABLE-04

12/03/2019

POTABLE-02

12/03/2019

POTABLE-02-DUP

Sample Date 12/03/2019

POTABLE-01

12/03/2019

Water, PFAS via EPA 537.1 (ng/L)

a. United States Environmental Protection Agency. 2016. Drinking Water Health Advisory for Perfluorooctanoic Acid (PFOA). Office of Water (4304T). Health and Ecological Criteria 

Division, Washington, DC 20460. EPA Document Number: 822-R-16-005. May 2016. / EPA. 2016. Drinking Water Health Advisory for Perfluorooctane Sulfonate (PFOS). Office of 

Water (4304T). Health and Ecological Criteria Division, Washington, DC 20460. EPA Document Number: 822-R-16-004. May 2016.

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3. Summary of Areas of Interest

This section presents a summary of each potential PFAS release area by AOI. The FTWHH PA 

identified ten potential PFAS release areas which were grouped into three AOIs based on 

proximity and inferred direction of groundwater flow (Figure 3-1). Results from the first 

mobilization performed in 2019 suggested four additional release areas potentially existed at the 

facility and directly off-site. Additional PA-level interviews were conducted with site workers, and 

as a result, four additional potential PFAS releases areas were identified (MTARNG 1049th 

Firefighting Training Area 1, 2, 3, and 4) within the three existing AOI boundaries. A summary of 

each AOI is presented below.

3.1 AOI 1 

AOI 1 consists of seven potential PFAS release areas as described below, the Black-Tailed Prairie 

Dog Relocation (three relocation areas), MTARNG 1049th Engineer Detachment (Building 1010), 

Mt. Defensa Avenue Drainage Ditch, MTARNG 1049th Firefighting Training Area 1, and MTARNG 

1049th Firefighting Training Area 3. 

3.1.1 Black-Tailed Prairie Dog Relocation

In 1997, the MTARNG began renovations in the southeast section of the Cantonment Area, near 

the Mt. Defensa Avenue Drainage Ditch. At the time, a colony of black-tailed prairie dogs inhabited 

the renovation zone. The MTARNG live-trapped and moved the prairie dogs to a previously 

unoccupied area approximately 0.5 miles north of the Cantonment Area to the Charles M. Russell 

National Wildlife Refuge (FaunaWest, 1998). 

During the last week of trapping in February 1998, an attempt was made to flush remaining prairie 

dogs from their burrows at multiple locations using a mixture of water and firefighting training

foam. The MTARNG 1049th Engineer Detachment recalled using firefighting training foam, not 

AFFF, to flush the prairie dogs from their burrows. The Relocation of the Fort Harrison Prairie Dog 

Colony (FaunaWest, 1998) contains materials information from Defense Supply Center, 

Columbus, for Dominion Restoration’s Foaming Surfactant (DRFS) in a 3% solution. According to 

this pamphlet, DRFS is “a solvent free, environmentally acceptable surrogate that was developed 

to simulate AFFF” and “a non-hazardous, water-based, neutral pH product that is 100 percent 

completely biodegradable” with the same appearance as AFFF. 

The foam mixture was delivered through a 2-inch diameter fire hose from a FTWHH firetruck to 

approximately 20 prairie dog burrows (combined into three areas). Two prairie dogs were flushed 

from their burrows, captured, and placed into a live-trap for later release. Approximately 750 

gallons of the firefighting training foam mixture were used to flush the prairie dog burrows

(FaunaWest, 1998). 

Additionally, the MTARNG relocated a black-tailed prairie dog colony that was on the VA property. 

The colony location was not sampled during the SI because it was outside the boundary of 

FTWHH. 

3.1.2 MTARNG 1049th Engineer Detachment (Building 1010)

The MTARNG 1049th Engineer Detachment currently operates out of Building 1010, which was 

constructed in 1995 and is located at the southeast corner of Rome Avenue and Middle Road. 

AFFF was stored at the MTARNG 1049th Engineer Detachment buildings and was only added to 

the firetrucks when it was intended for imminent use due to its corrosive action on the storage 

tanks. No information was available on the concentration or amount of AFFF stored; however, the 

MTARNG 1049th Engineer Detachment operated two types of trucks: small trucks capable of 
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holding approximately 40 gallons of solution and large trucks capable of holding approximately

100 gallons of solution. Annual AFFF fire training exercises were conducted by the MTARNG 

1049th Fire Department offsite at the Helena Regional Airport and/or at Malmstrom Air Force Base 

in Great Falls, Montana. No regularly scheduled fire training exercises were conducted at 

FTWHH. 

During fire training exercises, the majority of AFFF added to the trucks was expended. The trucks 

were washed, and residual AFFF was discharged with the wash water and allowed to dissipate 

on the ground. Washing and emptying of the trucks occurred at Building 1010 from 1995 to the 

early 2000s. The discharge was washed into the Mt. Defensa Avenue Drainage Ditch. The last 

known occurrence of washing and emptying of the trucks was in the early-2000s. 

3.1.3 Mt. Defensa Avenue Drainage Ditch

As described in Section 2.2.3 , the Mt. Defensa Avenue Drainage Ditch flows west to east through 

the VA property, into FTWHH along Mt. Defensa Avenue, and offsite by the Main Gate on Williams 

Street. Prior to 2016, little to no infiltration occurred within the Mt. Defensa Avenue Drainage Ditch 

due to the high velocity flow during snow melt and high intensity rain events. The ditch was 

reconfigured with large retention areas in 2016, slowing stormwater flow through the ditch. 

Information obtained during the PA indicated potential PFAS releases to soil have occurred along 

the Mt. Defensa Avenue Drainage Ditch from MTARNG activities onsite, as well as VA fire 

department activities upgradient of the facility. In February 2012, a rapid snowmelt event caused 

water to run vigorously through the drainage ditch. The vigorous movement of the water caused 

foaming in the drainage ditch that ran offsite to the retention pond just outside the main gate of 

the facility. The cause of the foaming is unknown; however, potential PFAS releases in and around 

the drainage ditch were noted by interviewees. Therefore, it is possible that the cause of the 

foaming is residual PFAS from training activities.

The Mt. Defensa Avenue Drainage Ditch runs from west to east through the VA property adjacent 

to FTWHH, along Mt. Defensa Avenue, and offsite by the Main Gate. Precipitation, snow melt, 

and other surface runoff on the VA property and much of the Cantonment Area is captured in the

Mt. Defensa Avenue Drainage Ditch, which flows to the Main Gate on Williams Street. Just outside 

the main gate there is a culvert that discharges stormwater across Williams Street between the

MTARNG property and residential properties. During rapid snow melt or high intensity rain events, 

runoff is channelized and flows through the ditch and Cantonment Area discharging just outside 

the main gate between the MacDonald Property and the residential properties. Surface water 

runoff that reaches the area between the MacDonald Property and residential properties 

dissipates and infiltrates the subsurface and may reach groundwater.

3.1.4 MTARNG 1049th Firefighting Training Area 1 and 3

After the first SI mobilization was completed, two firefighting training areas (FTAs) were identified 

in AOI 1. The 1049th trained with foam in the Navy Parking Lot north of AOI1-MW1 (MTARNG 

1049th Firefighting Training Area 1) and in the channel area east of AOI1-MW2 before the channel 

was excavated (MTARNG 1049th Firefighting Training Area 3). Specific details regarding the 

frequency, volume, chemical composition, and concentration of any potential AFFF used at either 

FTA are not known. 

3.2 AOI 2

AOI 2 consists of four potential PFAS release areas as described below, the Excavated Soil from 

Mt. Defensa Avenue Drainage Ditch. Former Weasel Barn, MTARNG 1049th Engineer 

Detachment (Building M1), and MTARNG 1049th Firefighting Training Area 4. 
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3.2.1 Excavated Soil from Mt. Defensa Avenue Drainage Ditch

Due to flooding of the Mt. Defensa Avenue Drainage Ditch during rapid snowmelt and large rainfall

events, the central portion of the ditch within the FTWHH boundary was widened in 2016 by 

excavating soil from the ditch. Based on the potential PFAS releases to this ditch, this soil is 

potentially contaminated with PFAS and was used to create a military vehicle staging area onsite

near a retention pond in the northeast section of the Cantonment Area.

3.2.2 Former Weasel Barn

The Former Weasel Barn located in the northeast section of the Cantonment Area, north of 

Sanananda Drive, was demolished in the winter of 2002 as part of a live-burn fire training exercise. 

The Former Weasel Barn housed the Weasel, a tracked vehicle designed for operations in Arctic 

environments. The MTARNG 1049th burned the structure, and the MTARNG 1049th Team Chief 

recalled using AFFF to extinguish the fire. No information was available on the volume, chemical 

composition, or concentration of AFFF used during the event.

3.2.3 MTARNG 1049th Engineer Detachment (Building M1)

Prior to 1995, the MTARNG 1049th Engineer Detachment operated out of the former Post 

Engineers Maintenance Shop (Building M1), near the Field Maintenance Shop #3, at the 

southeast corner of Williams Street and Barrett Road in the 1980s. Although Building M1 is 

located outside the boundary of FTWHH, the property is controlled by MTARNG. AFFF storage

and truck operations are described in Section 3.1.2. During fire training exercises, the majority of 

AFFF added to the trucks was expended. The trucks were washed, and residual AFFF was 

discharged with the wash water and allowed to dissipate on the ground at Building M1 in the late1980s.

3.2.4 MTARNG 1049th Firefighting Training Area 4

After the first SI mobilization was completed, one additional FTA was identified in AOI 2. The 

1049th trained with foam in the parking lot south of MW-08. Specific details regarding the 

frequency, volume, chemical composition, and concentration of any potential AFFF used at the 

FTA are not known.

3.3 AOI 3

AOI 3 consists of three potential PFAS release areas as described below, the Planned Fire 

Structure, Burial Trench, and MTARNG 1049th Firefighting Training Area 2. 

3.3.1 Planned Fire Structure

A structure was burned and used as a live-fire training exercise in the northwest portion of the 

Cantonment Area near the current Dining Facility (Building 410). The MTARNG 1049th Team 

Chief recalled using AFFF to extinguish this structure fire. Based on aerial photography, the 

structure was burned sometime between 1995 and 2002. Specific details regarding the frequency, 

volume, chemical composition, and concentration of the AFFF used during the exercise is not 

known.

3.3.2 Burial Trench

Prior to 1987, an area approximately 200 feet north of Colle Ferro Avenue in the northwest section 

of the Cantonment Area was used to dig a burial trench and dispose of debris and ordnance. One 

MTARNG retiree indicated that vehicles were placed in the burial trench, burned, and 
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extinguished with AFFF by MTARNG Firefighters. This use of AFFF could not be confirmed by

any other interviewees during the PA, and no information was available on the volume, chemical 

composition, and concentration of the potential AFFF released. The Combined Support 

Maintenance Shop was constructed due south of the burial trench in 1987.

3.3.3 MTARNG 1049th Firefighting Training Area 2

After the first SI mobilization was completed, one additional FTA was identified in AOI 3. The 

1049th trained with foam near the former location of Building 410 (Planned Fire Structure). 

Specific details regarding the frequency, volume, chemical composition, and concentration of any 

potential AFFF used at the FTA are not known.
Excavated Soil from Mt.

Defensa Ave Drainage Ditch

Prairie Dog

Relocation

MTARNG 1049th Engineer Detachment Building 1010

MTARNG 1049th Engineer

Detachment Building M1

Burial Trench

Planned Structure Fire

Former Weasel Barn

VA Fire Department

Releases

Mt. Defensa Avenue

Drainage Ditch

Prairie Dog

Relocation

MTARNG 1049th Firefighting Training Area 1

MTARNG 1049th Firefighting Training Area 2

MTARNG 1049th Firefighting Training Area 3

MTARNG 1049th Firefighting

Training Area 4

Veterans Administration

Retaining 

Pond

Landfill

Cherry Creek

Mt. Defensa A venue

Drainage Ditch

AOI 2

AOI 1

AOI 3

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Feet

Figure 3-1

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4. Project Data Quality Objectives

Project Data Quality Objectives (DQOs) are qualitative and quantitative statements that specify 

the quality of data and define the level of certainty required to support the project decision-making

process. The specific DQOs established for this facility are described below. These DQOs were 

developed in accordance with the USEPA’s seven-step iterative process (USEPA, 2006).

4.1 Problem Statement

The following problem statement was developed during project planning:

The presence of PFAS, which may pose a risk to human health or the environment, in 

environmental media at the facility is currently unknown. PFAS are classified as emerging 

environmental contaminants that are garnering increasing regulatory interest due to their potential 

risks to human health and the environment. The regulatory framework for managing PFAS at both 

the federal and state level continues to evolve.

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 Office of the Secretary of 

Defense (OSD) dated 15 October 2019 (Assistant Secretary of Defense, 2019). 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 three compounds: PFOS, PFOA, and PFBS. The SLs are presented in Section 6.1 of 

this Report. 

The following quotes from the DA policy documents form the basis for this project (DA, 2016; DA, 

2018):

• “The Army will research and identify locations where PFOS- and/or PFOA-containing 

products, such as AFFF, are known or suspected to have been used. Installations shall 

coordinate with installation/facility fire response or training offices to identify AFFF use or 

storage locations. The Army will consider FTAs, AFFF storage locations, hangars/buildings 

with AFFF suppression systems, fire equipment maintenance areas, and areas where 

emergency response operations required AFFF use as possible source areas. In addition, 

metal plating operations, which used certain PFOS-containing mist suppressants, shall be 

considered possible source areas.” 

• “Based on a review of site records...determine whether a CERCLA PA is appropriate for 

identifying PFOS/PFOA release sites. If the PA determines a PFOS/PFOA release may have 

occurred, a CERCLA SI shall be conducted to determine presence/absence of 

contamination.” 

• “Identify sites where perfluorinated compounds are known or suspected to have been 

released, with the priority being those sites within 20 miles of the public systems that tested 

above USEPA HA levels” (USEPA, 2016a; USEPA, 2016b).

4.2 Goals of the Study

The following goals were established for this SI:

1) Determine the presence or absence of PFOA, PFOS, and PFBS at or above SLs.

2) Develop information to potentially eliminate a release from further consideration because 

it is determined that it poses no significant threat to human health or the environment.

3) Determine the potential need for a removal action. 
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4) Collect data to better characterize the release areas for more effective and rapid initiation 

of an RI.

5) Identify within 4 miles of the installation other potential PFAS sources (fire stations, major 

manufacturers, other DoD facilities) and receptors, including both groundwater and 

surface water receptors, to determine whether the ARNG is the likely source of PFAS, or 

whether there is an off- facility source of PFAS responsible for installation detections of 

PFAS (USEPA, 2005).

6) Determine whether a potentially complete pathway exists between the source and 

potential receptors and whether ARNG is the likely source of the contamination. 

4.3 Information Inputs

Primary information inputs included:

• PA for FTWHH, Montana (AECOM, 2018c)

• Groundwater and soil samples collected in accordance with the Site Specific Uniform 

Federal Policy (UFP)-Quality Assurance Project Plan (QAPP) Addendum (AECOM, 2019)

• Field data collected during the two SI mobilizations, including groundwater elevation and 

water quality parameters measured at the time of sampling.

4.4 Study Boundaries

The scope of the SI sampling approach was bounded by the property limits of the facility (Figure 

2-1). Offsite sampling was not included in the scope of this SI; however, residential drinking water 

sampling was performed downgradient of FTWHH to determine if a complete drinking water 

pathways exists.

4.5 Analytical Approach

Samples were analyzed by Gulf Coast Analytical Laboratories, LLC (GCAL) during the first SI 

mobilization and Pace Analytical Gulf Coast during the second SI mobilization (GCAL acquired 

by Pace). The lab is accredited under the DoD Environmental Laboratory Accreditation Program 

(DoD ELAP; Accreditation Number 74960) and the National Environmental Laboratory 

Accreditation Program (NELAP; Certificate Number 01955). Data were compared to applicable 

SLs and decision rules as defined in the SI QAPP Addendum (AECOM, 2019). These rules

governed response actions based on the results of the SI sampling effort.

The decision rules described in the Worksheet #11 of the SI QAPP Addendum identify actions 

based on the following:

Groundwater:

• Is there a human receptor within 4 miles of the site?

• What is the concentration of PFOA, PFOS, and PFBS at the potential release area?

• What is the concentration of PFOA, PFOS, and PFBS at the facility boundary upgradient 

and downgradient of the potential release areas?

• What does the conceptual site model (CSM) suggest in terms of source, pathway and 

receptor? 
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Soil:

• What is the concentration of PFOA, PFOS, and PFBS in shallow surface soil (0 to 2 feet 

bgs)?

• What is the concentration of PFOA, PFOS, and PFBS constituents in deep soil (15 to 42 

feet bgs) (i.e., capillary fringe)?

• What does the CSM suggest in terms of source, pathway, and receptor? 

Soil and groundwater samples were collected from each of the potential release areas. 

Groundwater was encountered at approximately 14 to 49 feet bgs.

4.6 Data Usability Assessment

The Data Usability Assessment (DUA) is an evaluation at the conclusion of data collection 

activities that uses the results of both data verification and validation in the context of the overall 

project decisions or objectives. Using both quantitative and qualitative methods, the assessment 

determines whether project execution and the resulting data have met installation-specific DQOs. 

Both sampling and analytical activities are considered to assess whether the collected data are 

of the right type, quality, and quantity to support the decision-making (DoD, 2018a; DoD, 2018b; 

USEPA, 2017).

Data quality indicators (DQIs) (Precision, Accuracy, Representativeness, Comparability, 

Completeness and Sensitivity) are important components in assessing data usability. These DQIs 

were evaluated in the subsequent sections and demonstrate that the data presented in this SI 

report are of high quality. Although the SI data are considered reliable, some degree of uncertainty 

can be associated with the data collected. Specific factors that may contribute to the uncertainty 

of the data evaluation are described below. The Data Validation Report (Appendix A) presents 

explanations for all qualified data in greater detail.

4.6.1 Precision

Precision is the degree of agreement among repeated measurements of the same characteristic 

on the same sample or on separate samples collected as close as possible in time and place. 

Field sampling precision is measured with the field duplicate relative percent differences (RPD); 

laboratory precision is measured with calibration verification, internal standard recoveries, 

laboratory control spike (LCS) and matrix spike (MS) duplicate RPD.

Injection internal standards were added by the laboratory during sample injection to measure 

relative responses of target analytes and used to correct for bias associated with interference or 

losses during injection. Field sample AOI2-HA2-0-2 displayed injection internal standard area 

counts less than the lower quality control (QC) limit of 50% for M2PFDA, M2PFHxA, M2PFOA, 

and M4PFOS. The associated field sample results were positive and were qualified “J+”. These 

anomalies are considered minor, and the results are usable as qualified but should be considered 

as estimated values with a positive bias.

Extraction internal standards were added by the laboratory during sample extraction to measure 

relative responses of target analytes and used to correct for bias associated with matrix 

interferences and sample preparation efficiencies, injection volume variances, mass spectrometry 

ionization efficiencies, and other associated preparation and analytical anomalies. Several field 

samples displayed extraction internal standard percent recoveries associated with multiple 

analytes that were outside the QC limits. The positive field sample results associated with low 

extracted internal standard (EIS) percent recoveries were qualified “J+”, while those associated 

with high EIS percent recoveries were qualified “J-”. The non-detect field sample results 

associated with EIS percent recoveries outside the QC limits were qualified “UJ”. These 
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anomalies are considered minor, and the results are usable as qualified but should be considered 

as an estimated value.

Calibration verifications were performed routinely to ensure that instrument responses for all 

calibrated analytes were within established QC criteria. All calibration verifications were within the 

project established precision limits presented in the SI QAPP Addendum (AECOM, 2019).

LCS/LCS duplicate (LCSD) pairs were prepared by addition of known concentrations of each 

analyte in a matrix-free media known to be free of target analytes. LCS/LCSD pairs were analyzed 

for every analytical batch to demonstrate the ability of the laboratory to detect similar 

concentrations of a known quantity in matrix-free media. The LCS/LCSD pairs were within the 

project established precision limits presented in the SI QAPP Addendum (AECOM, 2019).

MS/MS duplicate (MSD) samples were prepared, analyzed, and reported for all preparation 

batches. MS/MSD samples demonstrated that the analytical system was in control for the matrix 

being tested. MS/MSD samples were submitted to the laboratory for analysis at a rate of 5%. The 

MS/MSD pairs were within the project established precision limits presented in the SI QAPP 

Addendum (AECOM, 2019).

Field duplicate samples were collected at a rate of 10% to assess the overall sampling and 

measurement precision for this sampling effort. The field duplicate samples were analyzed for 

PFAS and general chemistry parameters. The field duplicate samples were within the project 

established precision limits presented in the SI QAPP Addendum (AECOM, 2019).

4.6.2 Accuracy

Accuracy is a measure of confidence in a measurement. The smaller the difference between the 

measurement of a parameter and its "true" or expected value, the more accurate the 

measurement. The more precise or reproducible the result, the more reliable or accurate the 

result. Accuracy is measured through percent recoveries in the LCS/LCSD, MS/MSD, and 

surrogates.

LCS/LCSD samples were prepared by addition of known concentrations of each analyte in a 

matrix free media known to be free of target analytes. LCS/LCSD samples were analyzed for 

every analytical batch and demonstrated that the analytical system was in control during sample 

preparation and analysis, with one exception. The LCS/LCSD prepared in QC batch 661091 

displayed a percent recovery for perfluorotridecanoic acid (PFTrDA) greater than the upper QC 

limit of 130% at 149% in the LCS and 154% in the LCSD. The associated field sample results 

were non-detect; no data qualifying action was required.

MS/MSD samples were prepared, analyzed, and reported at a rate of 5%. MS/MSD samples 

demonstrated that the analytical system was in control for the matrix being tested, with one 

exception. The MS/MSD performed on parent sample AOI2-SS4-0-2 displayed a percent recovery 

for PFOS greater than the upper QC limit of 130% at 187% in the MS. The parent sample result 

was positive and was qualified “J+”. This anomaly is considered minor, and the result is usable 

as qualified but should be considered as an estimated value with a positive bias. The MS/MSD 

performed on parent sample AOI2-MW1 displayed MSD percent recoveries less than the lower 

QC limit of 70% for perfluorohexanesulfonic acid (PFHxS) and perfluorohexanoic acid (PFHxA) 

at 61% and 68%, respectively. The parent sample results were positive and were flagged “J-“.

These anomalies are considered minor, and the results are usable as qualified but should be 

considered as estimated values with a positive bias. The MS/MSD performed on parent sample 

AOI1-MW3-GW displayed percent recoveries greater than the upper QC limit for PFHxS at 133% 

in the MS and 140% in the MSD. The associated parent sample and field duplicate results were 

positive and were qualified “J+”.
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4.6.3 Representativeness

Representativeness qualitatively expresses the degree to which data accurately reflect site 

conditions. Factors that affect the representativeness of analytical data include appropriate 

sample population definitions, proper sample collection and preservation techniques, analytical 

holding times, use of standard analytical methods, and determination of matrix or analyte 

interferences. 

Relating to the use of standard analytical methods, the laboratory followed the method as 

established in PFAS via liquid chromatography with tandem mass spectrometry (LC/MS/MS)

compliant with DoD Quality Systems Manual (QSM) 5.1 Table B-15, including the specific 

preparation requirements (i.e. ENVI-Carb or equivalent used), mass calibration, spectra, all the 

ion transitions identified in Table B-15 were monitored, standards that contained both branch and 

linear isomers when available were used, and isotopically labeled standards were used for 

quantitation.

Field QC samples were collected to assess the representativeness of the data collected. Field 

duplicates were collected at a rate of 10% for all field samples, while MS/MSD samples were 

collected at a rate of 5%. Field sample FH-02-101120 was re-extracted and reanalyzed outside 

of holding time due to an EIS anomaly. The re-extracted results were qualified “J” and are

recommended to be retained within the data set. Several soil samples were submitted for pH 

analysis. The technical holding time for pH analysis is “immediate”; the associated results were 

qualified “J”. All preservation techniques were followed by the field staff, and all technical and 

analytical holding times were met by the laboratory. The laboratory used approved standard 

methods in accordance with the SI QAPP Addendum (AECOM, 2019) for all analyses.

Instrument blanks and method blanks were prepared by the laboratory in each batch as a negative 

control. Several PFAS instrument blanks and method blanks displayed detections greater than 

the detection limit for multiple target analytes. In total, 110 field sample results were qualified “U” 

during data validation due to associated detections in instrument and/or method blanks. The 

reported field sample result values were adjusted to be equal to the level of detection (LOD); the 

LOD was elevated to the concentration of the blank detection in instances where the blank 

concentration was greater than the LOD. The results are usable as qualified but should be 

considered false positives and treated as non-detect.

Equipment blanks and field blanks were also collected for groundwater and soil samples. 

Equipment blank AOI-MW3-EB displayed a detection greater than the detection limit for 

perfluorobutanoic acid (PFBA) at 16.5 ng/L. The positive associated field sample results were 

greater than five times the concentration in the equipment blank; therefore, no data qualifying 

action was required. The field blank sample FIELD BLANK displayed a detection greater than the 

detection limit for PFOS at 1.62 ng/L. The field blank result was associated with an instrument 

blank detection within five times the blank concentration and was qualified “U”. The qualified field 

blank result should be considered as false positive and treated as non-detect; no data qualifying 

action was taken based on the qualified field blank result. Equipment blank FTWHH-ERB-03 in 

QC batch 695178 displayed concentrations greater than the detection limit for 6:2 fluorotelomer 

sulfonate (6:2 FTS). The field sample results associated with the equipment blank were either 

non-detect, or previously qualified due to a method blank contamination; no further data qualifying 

action was required. The field blank FTWHH-FRB in QC batch 695178, displayed concentrations 

greater than the detection limit for 6:2 FTS. The associated field sample results were greater than 

five times the concentration found in the blank detection; no data qualifying action was required.

A sample of the water used for decontamination of the drill rig was collected in advance of the 

field effort. The drill rig decontamination sample FTWHH-DECON displayed non-detect results for 

all target analytes. Based on the sample results, the potable water source was deemed 

acceptable for use during the investigation for decontamination of drilling equipment and during 

well installation.
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Overall, the data are usable for evaluating the presence or absence of PFAS at the facility. 

Sufficient usable data were obtained to meet the objectives of the SI and to complete the risk 

assessment.

4.6.4 Comparability

Comparability is the extent to which data from one study can be compared directly to either past 

data from the current project or data from another study. Using standardized sampling and 

analytical methods, units of reporting, and site selection procedures help ensure comparability. 

Standard field sampling and typical laboratory protocols were used during the SI and are 

considered comparable to ongoing investigations.

4.6.5 Completeness

Completeness is a measure of the amount of valid data obtained from a measurement system 

compared to the amount of data expected under normal conditions. The laboratory provided data 

meeting system QC acceptance criteria for all samples tested. Project completeness was 

determined by evaluating the planned versus actual quantities of data. Percent completeness per 

parameter is as follows: 

• PFAS in groundwater via LC/MS/MS compliant with QSM 5.1 Table B-15 at 100%

• PFAS in soil via LC/MS/MS compliant with DoD QSM 5.1 Table B-15 at 100%

• pH in soil by USEPA Method 9045D at 100%

• Total organic carbon (TOC) by USEPA Method 9060 at 100%

4.6.6 Sensitivity

Sensitivity is the capability of a test method or instrument to discriminate between measurement 

responses representing different levels (e.g., concentrations) of a variable of interest. Examples 

of QC measures for determining sensitivity include laboratory fortified blanks, a method detection 

limit (MDL) study, and calibration standards at the level of quantitation (LOQ). In order to meet 

the needs of the data users, project data must meet the measurement performance criteria for 

sensitivity and project LOQs specified in the SI QAPP Addendum (AECOM, 2019). The laboratory 

provided the requested MDL studies and provided applicable calibration standards at the LOQ. In 

order to achieve the DQOs for sensitivity outlined in the SI QAPP Addendum (AECOM, 2019), the 

laboratory reported all field sample results at the lowest possible dilution. Additionally, any 

analytes detected below the LOQ and above the MDL were reported and qualified “J” as estimated 

values by the laboratory.
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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 dated March 2018 (AECOM, 2018a)

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

• Final Preliminary Assessment Report, Fort William Henry Harrison, Montana dated 

August 2018 (AECOM, 2018c)

• Final Site Safety and Health Plan, Fort William Henry Harrison, Montana dated October

2018 (AECOM, 2018d)

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

Fort William Henry Harrison, Montana dated January 2019 (AECOM, 2019)

• Final Supplemental Site Inspection Uniform Federal Policy-Quality Assurance Project 

Plan Addendum, Fort William Henry Harrison, Montana dated October 2020 (AECOM, 

2020)

SI field activities were conducted in two mobilizations. The first mobilization included permanent 

groundwater monitoring well installation, development, and sampling; surface and subsurface soil 

sampling; and groundwater sampling from existing wells from 10 to 20 February 2019 and from 

19 to 31 May 2019. The second mobilization included permanent groundwater monitoring well 

installation, development, and sampling; surface and subsurface soil sampling; and groundwater 

sampling from existing wells from 5 to 15 October 2020. Field activities were conducted in 

accordance with the SI QAPP Addendum and Supplemental SI QAPP Addendum (AECOM, 2019; 

AECOM, 2020), except as noted in Section 5.9.

To fulfill the project DQOs set forth in the approved the SI QAPP Addendum and Supplemental SI 

QAPP Addendum (AECOM, 2019; AECOM, 2020), samples were collected and analyzed for a 

subset of 18 PFAS by LC/MS/MS compliant with QSM 5.1 Table B-15 to fulfill the project DQOs:

Mobilization 1 –

• 47 soil grab samples from 27 boring locations; and

• 15 groundwater samples, six from new monitoring well locations, eight from existing 

monitoring well locations, and one from an irrigation well location. 

Mobilization 2 –

• 30 soil grab samples from 27 boring locations; and

• 15 groundwater samples, five from new monitoring well locations and ten from existing 

monitoring well locations. 

Figures 5-1 and 5-2 provide the sample locations for all media across the facility for Mobilization 

1 and 2, respectively. Table 5-1 presents all samples collected for each media during Mobilization 

1 and 2, respectively. Daily reports were completed throughout both SI activities, which are 

provided in Appendix B1. Additionally, a photographic log of field activities is provided in 

Appendix C.
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5.1 Pre-Investigation Activities

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

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

each of which is discussed in more detail below.

5.1.1 Technical Project Planning

The USACE TPP Process, 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 quantitative and 

qualitative DQOs, and formulating a sampling approach to address the AOIs identified in the PA. 

TPP Meeting 1 and 2 for Mobilization 1 were held on 8 November 2018, prior to SI field activities. 

Meeting minutes are provided in Appendix D. TPP meetings 1 and 2 were conducted in general 

accordance with EM 200-1-2 (USACE, 2016).

The stakeholders for this SI include the ARNG, MTARNG, USACE, MTDEQ, and the VA, and they 

were provided the opportunity to make comments on the technical sampling approach and 

methods in the TPP 2 meeting. The outcome of TPP meetings 1 and 2 were memorialized in the 

SI QAPP Addendum (AECOM, 2019). Future TPP meetings will provide an opportunity to discuss 

the results and findings, and future actions, where warranted.

No formal TPP Meeting 1 and 2 was held for Mobilization 2 given the scope followed many of the 

same procedures outlined in the SI QAPP Addendum. However, a call was held on 22 September 

2020 with the stakeholders (ARNG, MTARNG, USACE, and MTDEQ) to discuss the proposed 

sampling locations and MTDEQ comments on the Supplemental SI QAPP, which were provided 

before the call. 

5.1.2 Utility Clearance

Utility clearance was conducted by Montana811 and facilitated by MTARNG. MTARNG contacted 

Montana811 one-call utility clearance contractor to notify them of intrusive work. AECOM field 

staff were onsite during the utility locate. Additionally, the first 5 feet of each boring were advanced 

using an air knife and hand augering to verify utility clearance in shallow subsurface where utilities 

would typically be encountered. 

5.1.3 Source Water and PFAS Sampling Equipment Acceptability

A sample from a local potable water source at FTWHH was collected on 8 September 2018, prior 

to Mobilization 1, and analyzed for PFAS via LC/MS/MS compliant with DoD QSM 5.1 Table B15. The potable water source at FTWHH is supplied by the City of Helena. The results of the 

potable well sample are provided in Appendix G. A discussion of the results is presented in 

Section 4.6.3. The same water source was used during Mobilization 2. 

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

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

sampling environment is provided in PQAPP Appendix C, Table 1 (AECOM, 2018a). Prior to the 

start of field work each day, a PFAS 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. 
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5.2 Soil Borings and Soil Sampling

Soil borings and sampling were performed during both Mobilization 1 and 2. During Mobilization 

1, soil samples were collected from boreholes drilled by one of three methods: 1) air knifing, 2) 

hand augering, or 3) rotosonic drilling. In February 2019, when the ground was frozen, the surface 

soil and shallow subsurface samples were collected using an air knife, and in May 2019, during 

warmer weather, surface and shallow subsurface samples were collected with a hand auger. 

Deep subsurface soil samples collected from well borings were collected using a Boart Longyear 

LS250 minisonic drill rig. Three discrete soil samples were collected from the sonic well borings: 

the first from 0 to 2 feet bgs, the second from the mid-point between the surface and the 

groundwater table, and the third from approximately 1 foot above the groundwater table. The 

Mobilization 1 and 2 SI boring locations are shown on Figure 5-1, Mobilization 2 SI boring 

locations are shown on Figure 5-2, and boring depths for both mobilizations are provided Table 

5-1. The soil boring locations were selected based on the AOI information as agreed on through 

TPP and SI QAPP Addendum review. 

During Mobilization 2, soil samples were collected from boreholes drilled by one of three methods: 

1) air knifing, 2) hand augering, or 3) hollow stem auger (HSA). Surface and shallow subsurface 

soil samples were collected as described during Mobilization 1. Deep subsurface soil samples 

were collected from well borings using a CME-75 HSA rig with 18-inch split-spoons.

The soil cores were logged for lithological descriptions by a field geologist using the Unified Soil 

Classification System (USCS). A photoionization detector (PID) was used to screen the breathing 

zone during boring activities as part of personal safety requirements. Observations and 

measurements were recorded on sampling forms (Appendix B2) and in a 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. The boring logs are provided in Appendix E.

Each sample was collected into laboratory-supplied PFAS-free high-density polyethylene (HDPE) 

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

transported via Federal Express under standard chain-of-custody (COC) procedures to the 

laboratory and analyzed for PFAS via LC/MS/MS compliant with DoD QSM 5.1 Table B-15, TOC,

(USEPA Method 9060A) and pH (USEPA Method 9045D) in accordance with the SI QAPP 

Addendum (AECOM, 2019). For cases in which non-dedicated sampling equipment was used,

such as a stainless-steel scoop and mixing bowl used for the 0 to 2 feet bgs soil samples, 

equipment blank samples were collected and analyzed for the same parameters as the soil 

samples.

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 4 degrees Celsius (oC) during shipment.

5.3 Permanent Well Installation and Groundwater Sampling

Permanent monitoring wells were installed during both Mobilization 1 and 2. Six permanent 

groundwater monitoring wells were installed during Mobilization 1, and five were installed during 

Mobilization 2. The wells were installed at locations within or downgradient of potential PFAS 

release areas. Additionally, the new well locations assisted with the understanding of groundwater 

flow direction at the facility.

Boreholes were advanced using the drilling methods described above and used to install 2-inch 

diameter monitoring wells. The monitoring wells were constructed with Schedule 40 polyvinyl 

chloride (PVC), flush threaded 10-feet sections of riser, 0.010-inch slotted well screen, and a 
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Fort William Henry Harrison, MT

AECOM 5-4

threaded bottom cap. A filter pack of 20/40 silica sand was installed in the annulus around the 

well screen to a minimum of 2-feet above the well screen. A 2-feet thick bentonite seal was placed 

above the filter sand and hydrated with distilled water. Bentonite grout was placed in the well 

annulus from the top of the bentonite seal to ground surface during Mobilization 1. Bentonite chips 

were used during Mobilization 2. The bentonite grout/chips were allowed to set for 24-hours prior 

to well completion in accordance with the SI QAPP Addendum and Supplemental SI QAPP 

Addendum (AECOM, 2019; AECOM, 2020). The screen interval of each of the groundwater 

monitoring wells installed during Mobilization 1 and 2 are provided in Table 5-2.

The newly installed monitoring wells were developed no sooner than 24 hours following 

installation by pumping and surging using a variable speed submersible pump. Development of 

wells was completed in accordance with the SI QAPP Addendum and Supplemental SI QAPP 

Addendum (AECOM, 2019; AECOM, 2020).

5.4 Groundwater Sampling from Existing Wells

Groundwater samples were collected from newly installed and existing monitoring wells during 

Mobilization 1 and 2. Samples from newly installed wells were collected no sooner than 24 hours 

following development. All samples were collected via low-flow sampling methods using a bladder 

pump (with a disposable polytetrafluoroethylene bladder) with disposable PFAS-free, HDPE 

tubing. New tubing and bladders were 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, specific conductance, pH, 

dissolved oxygen [DO], turbidity, and oxidation-reduction potential [ORP]) were measured using 

a water quality meter and recorded on the field sampling form (Appendix B2). Water levels were 

measured to the nearest 0.01 inch and recorded. 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. During Mobilization 

1, the Pump House system was flushed and sampled for 15 minutes prior to collecting the 

groundwater sample. The location of wells sampled during Mobilization 1 are provided in Figure 

5-1, Mobilization 2 in Figure 5-2, and the screen interval of each of the groundwater monitoring 

wells is provided in Table 5-2.

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, transported via Federal Express 

under standard COC procedures to the laboratory, and analyzed for PFAS in accordance with the 

SI QAPP Addendum and Supplemental SI QAPP Addendum (AECOM, 2019; AECOM, 2020). 

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

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

same parameters as the accompanying samples. FRBs accompanied each cooler containing 

samples for PFAS analysis and were analyzed for select PFAS. A temperature blank was placed 

in each cooler to ensure that samples were preserved at or below 4 o

C during shipment.

5.5 Synoptic Water Level Measurements

A synoptic groundwater gauging event was performed on 30 May 2019 and 13 October 2020. 

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

flow contour map is provided in Figure 2-4 and Figure 2-5. Depth to water readings and 

calculated groundwater elevation data from both synoptic rounds are provided in Table 5-3.

5.6 Surveying

The northern side of each well casing was surveyed by Montana-Licensed land surveyor following 

guidelines provided in the standard operating procedures provided in the SI QAPP Addendum 
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AECOM 5-5

and Supplemental SI QAPP Addendum (AECOM, 2019; AECOM, 2020). Survey data from the 

newly installed wells were collected on 24 July 2019 and 14 October 2020 in the Montana State 

Plane North American Datum of 1983 and North American Vertical Datum of 1988. The surveyed 

well data is provided in Appendix B3.

5.7 Investigation Derived Waste

Soil investigation-derived waste (IDW) (i.e., soil cuttings) and liquid IDW (purge and 

decontamination water) generated during the SI activities were containerized in 55-gallon drums

for future disposal by ARNG. The soil and liquid IDW was not sampled and assumes the PFAS 

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

Other solids such as spent personal protective equipment (PPE), 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 for PFAS via LC/MS/MS compliant with QSM 5.1 Table B-15 by

GCAL/Pace Analytical Gulf Coast in Baton Rouge, Louisiana, a DoD ELAP and NELAP certified 

laboratory. The 18 PFAS analyzed as part of the ARNG SI program include the following: 

• 6:2 fluorotelomer sulfonate (6:2 FTS)

• 8:2 fluorotelomer sulfonate (8:2 FTS)

• N-ethyl 

perfluorooctanesulfonamidoacetic acid 

(NEtFOSAA)

• N-methyl 

perfluorooctanesulfonamidoacetic acid 

(NMeFOSAA)

• Perfluorobutyrate (PFBA)

• Perfluorobutanesulfonic acid (PFBS)

• Perfluorodecanoic acid (PFDA)

• Perfluorododecanoic acid (PFDoA)

• Perfluoroheptanoic acid (PFHpA)

• Perfluorohexanoic acid (PFHxA)

• Perfluorohexanesulfonic acid (PFHxS)

• Perfluorononanoic acid (PFNA)

• Perfluorooctanoic acid (PFOA)

• Perfluorooctanesulfonic acid (PFOS)

• Perfluoropentanoic acid (PFPeA)

• Perfluorotetradecanoic acid (PFTeDA)

• Perfluorotridecanoic acid (PFTrDA)

• Perfluoroundecanoic acid (PFUdA)

Soil samples were also analyzed for TOC using USEPA Method 9060A, and pH by USEPA 

Method 9045D.

5.9 Deviations from SI QAPP Addendum

Deviations from the SI QAPP Addendum and Supplemental SI QAPP Addendum occurred based 

on field conditions and discussion between AECOM and ARNG. Deviations from both 

mobilizations are noted below:

• During Mobilization 1, the SI QAPP Addendum indicated that groundwater would be sampled 

at nine existing wells. The USGS Well was only a PVC stickup location to measure water 

level and not a properly installed well location; therefore, a groundwater sample was not 

collected from this location.
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• During Mobilization 2, two proposed sample locations within AOI 1 (AOI01-MW4 and AOI01-

SS7) were within the Navy property boundary. The field team shifted these proposed

locations to the east (on FTWHH property) and completed a Field Change Request for team

approval before proceeding with sampling those locations. This has been included in

Appendix B4.
Table 5-1

Samples by Medium

Fort William Henry Harrison, MT

Site Inspection Report

Sample Identification

Sample

Collection 

Date

Sample 

Depth 

(ft bgs)

PFAS (USEPA Method 537 Modified)TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size(ASTM D422)

Comments

AOI1-SB1-0-2 2/13/2019 0-2 x x x

AOI1-SB1-20-22 2/13/2019 20-22 x x x MS/MSD

AOI1-SB1-38-40 2/13/2019 38-40 x x x

AOI1-MW1-18-20 2/13/2019 18-20 x

AOI1-MW1-50-55 2/13/2019 50-55 x

AOI1-SB2-0-2 2/15/2019 0-2 x x x

AOI1-SB2-15-17 2/15/2019 15-17 x x x

AOI1-SB2-28-30 2/15/2019 28-30 x x x

AO1-MW2-35-37 2/15/2019 35-37 x

AOI1-SB3-0-2 2/20/2019 0-2 x x x

AOI1-SB3-18-20 2/20/2019 18-20 x x x

AOI1-SB3-18-20-DUP 2/20/2019 18-20 x x x Field Duplicate

AOI1-SB3-38-40 2/20/2019 38-40 x x x

AOI1-MW3-47-48 2/20/2019 47-48 x

AOI1-HA1-0-2 2/12/2019 0-2 x x x

AOI1-HA1-2-4 2/12/2019 2-4 x x x

AOI1-HA2-0-2 2/12/2019 0-2 x x x

AOI1-HA2-2-4 2/12/2019 2-4 x x x

AOI1-SS1-0-2 2/14/2019 0-2 x x x

AOI1-SS1-0-2R 5/20/2019 0-2 x x x

AOI1-SS2-0-2 2/14/2019 0-2 x x x

AOI1-SS3-0-2 2/14/2019 0-2 x x x MS/MSD

AOI1-SS4-0-2 2/14/2019 0-2 x x x

AOI1-SS5-0-2 2/14/2019 0-2 x x x

AOI1-SS6-0-2 2/20/2019 0-2 x x x

AOI01-04-SB-00-02 10/7/2020 0-2 x

AOI01-04-SB-15-17 10/9/2020 15-17 x

AOI01-04-SB-30-32 10/9/2020 30-32 x x x

AOI01-05-SB-00-02 10/6/2020 0-2 x

AOI01-05-SB-15-17 10/8/2020 15-17 x x x

AOI01-05-SB-15-17-DUP 10/8/2020 15-17 x x Field Duplicate

AOI01-05-SB-15-17-MS 10/8/2020 15-17 x x MS

AOI01-05-SB-15-17-MSD 10/8/2020 15-17 x x MSD

AOI01-05-SB-30-32 10/8/2020 30-32 x

AOI01-06-SB-00-02 10/6/2020 0-2 x

AOI01-06-SB-15-17 10/9/2020 15-17 x

AOI01-06-SB-30-32 10/9/2020 30-32 x

AOI01-SS7-00-02 10/7/2020 0-2 x

AOI01-SS8-00-02 10/6/2020 0-2 x

AOI01-SS9-00-02 10/6/2020 0-2 x

AOI01-SS10-00-02 10/6/2020 0-2 x

AOI01-SS11-00-02 10/7/2020 0-2 x

AOI01-SS12-00-02 10/7/2020 0-2 x

AOI01-SS13-00-02 10/7/2020 0-2 x

AOI01-SS14-00-02 10/7/2020 0-2 x

AOI01-SS15-00-02 10/7/2020 0-2 x

AOI2-SB1-0-2 5/21/2019 0-2 x x x

AOI2-SB1-9-11 5/21/2019 9-11 x x x

AOI2-SB1-18-20 5/21/2019 18-20 x x x

AOI2-SB2-0-2 5/23/2019 0-2 x x x

AOI2-SB2-0-2-DUP 5/21/2019 0-2 x x x Field Duplicate

AOI2-SB2-8-10 5/23/2019 8-10 x x x

AOI2-SB2-18-20 5/23/2019 18-20 x x x

AOI2-HA1-0-2 2/13/2019 0-2 x x x

AOI2-HA1-2-4 2/13/2019 2-4 x x x

AOI2-HA2-0-2 2/13/2019 0-2 x x x MS/MSD

AOI2-HA2-2-4 2/13/2019 2-4 x x x

AOI2-HA2-2-4-DUP 2/13/2019 2-4 x x x Field Duplicate

SI Soil Samples AOI 2

SI Soil Samples AOI 1

SSI Soil Samples AOI 1

AECOM

5-7
Table 5-1

Samples by Medium

Fort William Henry Harrison, MT

Site Inspection Report

Sample Identification

Sample

Collection 

Date

Sample 

Depth 

(ft bgs)

PFAS (USEPA Method 537 Modified)TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size(ASTM D422)

Comments

AOI2-HA3-0-2 2/13/2019 0-2 x x x

AOI2-HA3-2-4 2/13/2019 2-4 x x x

AOI2-HA4-0-2 2/13/2019 0-2 x x x

AOI2-HA4-2-4 2/13/2019 2-4 x x x

AOI2-HA5-0-2 2/13/2019 0-2 x x x

AOI2-HA5-2-4 2/13/2019 2-4 x x x

AOI2-HA6-0-2 2/12/2019 0-2 x x x

AOI2-HA6-2-4 2/12/2019 2-4 x x x

AOI2-HA6-2-4-DUP 2/12/2019 2-4 x x x Field Duplicate

AOI2-SS1-0-2 5/20/2019 0-2 x x x

AOI2-SS2-0-2 5/20/2019 0-2 x x x

AOI2-SS2-0-2-DUP 5/20/2019 0-2 x x x Field Duplicate

AOI2-SS3-0-2 5/20/2019 0-2 x x x

AOI2-SS4-0-2 5/20/2019 0-2 x x x MS/MSD

AOI2-SS5-0-2 5/20/2019 0-2 x x x

AOI02-03-SB-00-02 10/6/2020 0-2 x x x

AOI02-03-SB-00-02-DUP 10/6/2020 0-2 x Field Duplicate

AOI02-03-SB-00-02-MS 10/6/2020 0-2 x MS

AOI02-03-SB-00-02-MSD 10/6/2020 0-2 x MSD

AOI02-03-SB-10-12 10/10/2020 10-12 x

AOI02-03-SB-10-12-DUP 10/10/2020 10-12 x Field Duplicate

AOI02-03-SB-25-27 10/10/2020 25-27 x

AOI02-SS6-00-02 10/6/2020 0-2 x

AOI02-SS7-00-02 10/6/2020 0-2 x

AOI02-SS8-00-02 10/6/2020 0-2 x

AOI3-SB1-0-2 5/22/2019 0-2 x x x

AOI3-SB1-18-20 5/22/2019 18-20 x x x

AOI3-SB1-40-42 5/22/2019 40-42 x x x

AOI3-HA1-0-2 2/12/2019 0-2 x x x

AOI3-HA1-0-4 2/12/2019 2-4 x x x

AOI03-02-SB-00-02 10/6/2020 0-2 x

AOI03-SS1-00-02 10/7/2020 0-2 x

AOI03-SS2-00-02 10/7/2020 0-2 x

AOI03-SS3-00-02 10/7/2020 0-2 x

AOI03-SS4-00-02 10/7/2020 0-2 x

AOI03-SS4-00-02-DUP 10/7/2020 0-2 x Field Duplicate

AOI03-SS5-00-02 10/7/2020 0-2 x x x

AOI1-MW1 5/28/2019 Mid-Screen x

AOI1-MW2 5/29/2019 Mid-Screen x

AOI1-MW2-DUP 5/29/2019 Mid-Screen x Field Duplicate

AOI1-MW3 5/25/2019 Mid-Screen x

BH-02 5/28/2019 Mid-Screen x

FH-02 5/28/2019 Mid-Screen x

AOI2-MW1 5/29/2019 Mid-Screen x

AOI2-MW2 5/30/2019 Mid-Screen x

MW-06 5/29/2019 Mid-Screen x

MW-06-DUP 5/29/2019 Mid-Screen x Field Duplicate

MW-07 5/30/2019 Mid-Screen x

MW-08 5/29/2019 Mid-Screen x

AOI3-MW1 5/29/2019 Mid-Screen x

MW-10 5/29/2019 Mid-Screen x

MW-11 5/30/2019 Mid-Screen x

OBTMW-01 5/30/2019 Mid-Screen x

PH-1 5/30/2019 NA x

PH-2-DUP 5/30/2019 NA x Field Duplicate

AOI1-MW1-GW 10/11/2020 53.0 x

SSI Soil Samples AOI 3

SI Soil Samples AOI 3

SI Groundwater Samples

SSI Groundwater Samples

SSI Soil Samples AOI 2

AECOM

5-8
Table 5-1

Samples by Medium

Fort William Henry Harrison, MT

Site Inspection Report

Sample Identification

Sample

Collection 

Date

Sample 

Depth 

(ft bgs)

PFAS (USEPA Method 537 Modified)TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size(ASTM D422)

Comments

AOI1-MW2-GW 10/12/2020 38.5 x

AOI1-MW3-GW 10/10/2020 45.0 x

AOI1-MW3-GW-DUP 10/10/2020 45.0 x Field Duplicate

AOI1-MW3-GW-MS 10/10/2020 45.0 x MS

AOI1-MW3-GW-MSD 10/10/2020 45.0 x MSD

AOI1-MW04-GW 10/14/2020 36.0 x

AOI1-MW05-GW 10/12/2020 40.0 x

AOI1-MW06-GW 10/13/2020 33.5 x

BH-02-101020 10/10/2020 31.0 x

FH-02-101120 10/11/1010 51.0 x

AOI2-MW1-GW 10/12/2020 35.0 x

AOI2-MW1-GW-DUP 10/12/2020 35.0 x Field Duplicate

AOI2-MW2-GW 10/13/2020 25.0 x

AOI2-MW03-GW 10/14/2020 36.0 x

MW-08-101120 10/11/2020 50.0 x

AOI3-MW1-GW 10/9/2020 56.5 x

AOI3-MW02-GW 10/13/2020 56.0 x

MW-11-100920 10/9/2020 52.0 x

AOI1-HA1-2-4-EB 2/13/2019 x Equipment Blank

AOI1-SS1-0-2-EB 2/14/2019 x Equipment Blank

AOI1-MW3-EB 2/16/2019 x Equipment Blank

AOI2-FRB 5/20/2016 x Field Blank

AOI3-SB1-0-2-EB 5/21/2019 x Equipment Blank

AOI2-SB1-0-2-EB 5/23/2019 x Equipment Blank

FTWHH-ERB-01 10/6/2020 x Equipment Blank

FTWHH-ERB-02 10/7/2020 x Equipment Blank

FTWHH-ERB-03 10/10/2020 x Equipment Blank

FTWHH-ERB-04 10/14/2020 x Equipment Blank

FTWHH-FRB-01 10/10/2020 x Field Blank

Notes:

AOI = Area of Interest

ASTM = American Standard Test Method

EB = equipment blank

ERB = equipment blank

FRB = field reagent blank

GW = groundwater

ft = feet

HA = hand auger

MS/MSD = matrix spike/ matrix spike duplicate

MW = monitoring well

NA = not applicable

PFAS = per- and polyfluoroalkyl substances

PH = Pump House

R = recollected

SB = soil boring

SS = surface soil

TOC = Total Organic Carbon

USEPA = United States Environmental Protection Agency

Field Blank Samples

AECOM

5-9
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 5-10

THIS PAGE INTENTIONALLY BLANK
Table 5-2

Monitoring Well Screen Intervals

Fort William Henry Harrison, MT

Site Inspection Report

Monitoring 

Well ID

Screen 

Interval 

(ft bgs)

AOI1-MW1 45-55

AOI1-MW2 30-40

AOI1-MW3 40-50

AOI1-MW4 28-38

AOI1-MW5 35-45

AOI1-MW6 27-37

AOI2-MW1 28-38

AOI2-MW2 20-30

AOI2-MW3 30-40

AOI3-MW1 48-58

AOI3-MW2 50-60

BH-02 29-34

FH-02 34.8-54.8

MW-05 29-39.2

MW-06 20-30

MW-07 29.1-39.1

MW-08 39.2-59.2

MW-10 59-79

MW-11 25-55

MW-12 35-55

OBTMW-01 20-50

Notes:

bgs = below ground surface

ft = feet

ID = identification

AECOM

5-11
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 5-12

THIS PAGE INTENTIONALLY BLANK
Table 5-3

Groundwater Elevation

Fort William Henry Harrison, MT

Site Inspection Report

Monitoring Well ID Date 

Measured

Top of Casing 

Elevation (ft amsl)

Depth to Water 

(ft btoc)

Groundwater 

Elevation (ft amsl)

AOI1-MW1 5/30/2019 3985.92 31.25 3954.67

AOI1-MW2 5/30/2019 3976.32 31.85 3944.47

AOI1-MW3 5/30/2019 3948.75 32.44 3916.31

BH-02 5/30/2019 3968.06 24.04 3944.02

FH-02 5/30/2019 3954.95 34.17 3920.78

AOI2-MW1 5/30/2019 3950.83 21.10 3929.73

AOI2-MW2 5/30/2019 3946.64 14.23 3932.41

MW-06 5/30/2019 3952.55 20.65 3931.90

MW-07 5/30/2019 3948.40 16.44 3931.96

MW-08 5/30/2019 3959.17 27.19 3931.98

AOI3-MW1 5/30/2019 4003.43 42.87 3960.56

MW-10 5/30/2019 3977.10 29.87 3947.23

MW-11 5/30/2019 3981.19 27.81 3953.38

OBTMW-01 5/30/2019 3982.56 27.90 3954.66

AOI1-MW1 10/12/2020 3985.93 34.71 3951.22

AOI1-MW2 10/12/2020 3976.33 33.80 3942.53

AOI1-MW3 10/12/2020 3948.76 32.13 3916.63

AOI1-MW4 10/12/2020 3975.46 29.40 3946.06

AOI1-MW5 10/12/2020 3947.70 33.92 3913.78

AOI1-MW6 10/12/2020 3948.09 29.82 3918.27

BH-02 10/12/2020 3968.07 27.59 3940.48

FH-02 10/12/2020 3954.95 34.43 3920.52

AOI2-MW1 10/12/2020 3950.84 22.79 3928.05

AOI2-MW2 10/12/2020 3946.65 17.33 3929.32

AOI2-MW3 10/12/2020 3953.36 24.18 3929.18

MW-05 10/12/2020 3954.99 25.54 3929.45

MW-06 10/12/2020 3952.56 23.54 3929.02

MW-07 10/12/2020 3948.41 19.39 3929.02

MW-08 10/12/2020 3959.18 28.90 3930.28

AOI3-MW1 10/12/2020 4003.44 43.93 3959.51

AOI3-MW2 10/12/2020 3993.34 49.65 3943.69

MW-10 10/12/2020 3977.13 30.11 3947.02

MW-11 10/12/2020 3981.20 29.29 3951.91

MW-12 10/12/2020 3980.48 36.56 3943.92

OBTMW-01 10/12/2020 3982.57 29.65 3952.92

Notes:

amsl = above mean sea level

btoc = below top of casing

ft = feet

AECOM

5-13
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 5-14

THIS PAGE INTENTIONALLY BLANK 
A! A!

A! A!

A!

A!

A!

A!

"S A!

A!

A!

"S

"S

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"S

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"J

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"J

"J

"S "S

"S

"S

!5

Excavated Soil from Mt.

Defensa Ave Drainage Ditch

Prairie Dog

Relocation

MTARNG 1049th Engineer Detachment Building 1010

MTARNG 1049th Engineer

Detachment Building M1

Burial Trench

Planned Structure Fire

Former Weasel Barn

VA Fire Department

Releases

Mt. Defensa Avenue

Drainage Ditch

Prairie Dog

Relocation

MTARNG 1049th Firefighting Training Area 1

MTARNG 1049th Firefighting Training Area 2

MTARNG 1049th Firefighting Training Area 3

MTARNG 1049th Firefighting

Training Area 4

Veterans Administration

Retaining 

Pond

FH-02

BH-02

MW-08

MW-07 MW-06

MW-10 OBTMW-01

Landfill

Excavated Area

1

2

3

MW11

Cherry Creek

Mt. Defensa Avenue Drainage Ditch

AOI 2

AOI 1

AOI 3

AOI3-HA1 AOI3-MW1

AOI1-MW1

AOI1-MW2

AOI1-HA1 AOI1-HA2

AOI1-MW3

AOI2-MW1

AOI2-HA6

AOI2-HA4

AOI2-MW2

AOI2-SS4

AOI2-SS2

AOI2-SS1

AOI2-SS3

AOI2-SS5

AOI1-SS5

AOI1-SS4

AOI1-SS2

AOI1-SS1

AOI1-SS6

AOI1-SS3

AOI2-HA1

AOI2-HA2

AOI2-HA5

AOI2-HA3

PH-1

0 300 600 1,200

Feet

Figure 5-1

SI Mobilization 1 Sample Locations

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

JH

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

1:7,200

C:\Users\stankevichm\OneDrive - AECOM Directory\ARNG_PFAS_GIS_60552172\MXDs\MT\FTWHH\FTWHH_SI\SI_Report\Fig_5-1_FTWHH_SI_Sample_Locations.mxd

A! Monitoring Well

"S Surface/Subsurface Soil Location

"J Surface Soil Location

!5 Existing Pumphouse Well

Area of Interest

Potential PFAS Release

Facility Boundary

River/Stream

Surface Water Flow Direction

Groundwater Flow Direction

5-15
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 5-16

THIS PAGE INTENTIONALLY BLANK
!?

!?

!?

!?

!?

!?

!?

!? !? !? !? !?

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!? !?

!? !?

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!?!?

A!

A!

A!

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A!

A!

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A!

A!

Veterans Administration

Landfill

Excavated Area

MTARNG 1049th Firefighting

Training Area 1

MTARNG 1049th Firefighting

Training Area 2

MTARNG 1049th Firefighting

Training Area 3

MTARNG 1049th Firefighting Training Area 4

AOI01-SS13

AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI01-SS7

AOI01-SS8

AOI01-SS9

AOI01-SS10

AOI01-SS11

AOI01-SS12

AOI01-SS14

AOI01-SS15

AOI02-MW03

AOIO2-SS6

AOIO2-SS7

AOIO2-SS8

AOI03-MW02

AOI03-SS1

AOI03-SS2

AOI03-SS3

AOI03-SS4

AOI03-SS5

AOI01-MW02

AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

BH-02

FH-02

MW-08

MW-11

Cherry Creek

Mt. Defensa Avenue Drainage Ditch

AOI 2

AOI 1

AOI 3

0 300 600 1,200

Feet

Figure 5-2

SI Mobilization 2 Sample Locations

12420 Milestone Center Drive ­ Germantown, MD 20876

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

JH

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

1:7,200

C:\Users\stankevichm\OneDrive - AECOM Directory\ARNG_PFAS_GIS_60552172\MXDs\MT\FTWHH\FTWHH_SI\SI_Report\Fig_5-2_FTWHH_SSI_Supplemental_Sample_Locations.mxd

Area of Interest

Potential PFAS Release

Facility Boundary

River/Stream

Surface Water Flow Direction

Groundwater Flow Direction

A! Existing Monitoring Well

2020 SSI Locations

!? Monitoring Well

!? Soil Sample Location

5-17
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 5-18

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 6-1

6. Site Inspection Results 

This section presents the analytical results of the SI for each AOI. The SLs used in this evaluation 

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

through 6.5. Table 6-2 through Table 6-5 present PFAS results for samples with detections in soil 

and groundwater; only constituents detected in one or more samples are included. 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 15 October 

2019 (Assistant Secretary of Defense, 2019). 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 an RI, the next 

phase under CERCLA. The SLs apply to three compounds, PFOA, PFOS, and PFBS, for both 

soil and groundwater, as presented in Table 6-1. 

All other results presented in this report are considered informational in nature and serve as an 

indication as to whether soil and groundwater contain or do not contain PFAS within the 

boundaries of the facility.

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

Analyte

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 130 1,600 40

PFOS 130 1,600 40

PFBS 130,000 1,600,000 40,000

Notes:

a.) Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in 

Groundwater and Soil using United States Environmental Protection Agency’s (USEPA’s) Regional Screening 

Level Calculator. HQ=0.1. 15 October 2019.

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 of PFAS contaminants. According to the Interstate 

Technology Regulatory Council (ITRC), several important PFAS 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 
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 6-2

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, which includes seven potential PFAS release areas: Black-Tailed Prairie Dog Relocation areas

(three locations), MTARNG 1049th Engineer Detachment Building 1010, Mt. Defensa Avenue 

Drainage Ditch, 1049th Firefighting Training Area 1, and 1049th Firefighting Training Area 3. The 

detected compounds in soil and groundwater are summarized in Tables 6-2 through 6-5. The 

detections of PFOA and PFOS in soil and groundwater are presented on Figures 6-1 through 6-

6.

6.3.1 AOI 1 Soil Analytical Results

Within the Mt. Defensa Avenue Drainage Ditch, soil was sampled at three intervals from soil 

borings locations AOI1-SB1 and AOI1-SB3 and one interval from surface locations AOI1-SS1 

through AOI1-SS6. All PFOA, PFOS, and PFBS results were below SLs. PFOA concentrations 

ranged from non-detect to 0.122 J micrograms per Kilogram (μg/Kg), which occurred at AOI1-

SB3 in the shallow interval (0 to 2 feet bgs). PFOS concentrations ranged from non-detect to 2.23 

μg/Kg, which occurred at AOI1-SS5 in the shallow interval (0 to 2 feet bgs). PFBS concentrations 

ranged from non-detect to 0.012 J μg/Kg, which occurred in AOI1-SB3 in the shallow interval (0 

to 2 feet bgs). In the intermediate interval, PFOA concentrations were non-detect. PFOS 

concentrations ranged from 0.039 J μg/Kg in AOI1-SB1 (20 to 22 feet bgs) to 0.526 J μg/Kg in 

AOI1-SB3 (18 to 20 feet bgs). PFBS concentrations ranged from 0.00418 J μg/Kg in AOI1-SB1 

(20 to 22 feet bgs) to 0.021 J μg/Kg in AOI1-SB3 (18 to 20 feet bgs). In the deep interval, PFOA 

and PFBS concentrations were non-detect. PFOS concentrations ranged from 0.014 J μg/Kg in 

AOI1-SB1 (38 to 40 feet bgs) to 0.135 J μg/Kg, in AOI1-SB3 (38 to 40 feet bgs). Table 6-2 and 

Table 6-4 summarize the detected compounds in soil. Figure 6-1 and Figure 6-2 present ranges 

of detections of PFOS and PFOA in soil. 

Within the 1049th Engineer Detachment Building 1010 area, soil was sampled at three intervals 

from soil boring location AOI1-SB2. All PFOA, PFOS, and PFBS results were below SLs. PFOA 

was non-detect in the shallow interval (0 to 2 feet bgs). PFOS was detected at 0.751 J μg/Kg and 

PFBS was detected at 0.104 J μg/Kg. In the intermediate interval (15 to 17 feet bgs), PFOA was 

detected at 0.055 J μg/Kg, PFOS was detected at 0.478 J μg/Kg, and PFBS was detected at 

0.142 J μg/Kg. PFOA, PFOS, and PFBS were non-detect in the deep interval (28 to30 feet bgs).

Table 6-2 and Table 6-4 summarize the detected compounds in soil. Figure 6-1 and Figure 6-2

present ranges of detections of PFOS and PFOA in soil.

Within in the Prairie Dog Relocation areas, soil was sampled at two intervals from hand auger 

locations AOI1-HA1 and AOI1-HA2. All PFOA, PFOS, and PFBS results were below SLs. PFOA 

and PFOS concentrations were all non-detect in the shallow interval (0 to 2 feet bgs) and 

intermediate interval (2 to 4 feet bgs). PFBS concentrations ranged from non-detect in AOI1-HA2 

(2 to 4 feet bgs) to 0.00547 J μg/Kg in AOI1-HA2 (2 to 4 feet bgs). Table 6-2 and Table 6-3

summarize the detected compounds in soil. Figure 6-1 and Figure 6-2 present ranges of 

detections of PFOS and PFOA in soil.

Soil was sampled at three intervals from soil borings locations AOI01-04-SB through AOI01-06-

SB and one interval from surface locations AOI1-SS8 through AOI1-SS10 at the FTWHH parcel 

of property located on the east side of Williams Street. PFOA, PFOS, and PFBS concentrations 

were non-detect.

Within in the 1049th Firefighting Training Area 1, surface soil was sampled from location AOI01-

SS7. PFOA, PFOS, and PFBS results were below SLs. PFOA and PFBS concentrations were
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 6-3

non-detect. The PFOS concentration was 0.630 J μg/Kg, which occurred in the shallow interval 

(0 to 2 feet bgs). Table 6-2 summarize the detected compounds in soil. Figure 6-3 present the

detections of PFOS in soil.

Within in the 1049th Firefighting Training Area 3, surface soil was sampled from locations AOI01-

SS11 through AOI01-SS15 (0 to 2 feet bgs). All PFOA, PFOS, and PFBS results were below SLs. 

PFOA concentrations ranged from non-detect to 0.166 J μg/Kg, which occurred in AOI1-SS11 (0 

to 2 feet bgs). PFOS concentrations ranged from non-detect to 39.9 μg/Kg, which occurred in 

AOI1-SS11 (0 to 2 feet bgs). PFBS concentrations ranged from non-detect to 1.08 μg/Kg, which 

occurred in AOI1-SS11 (0 to 2 feet bgs). Table 6-2 summarizes the detected compounds in soil. 

Figure 6-3 and Figure 6-4 present ranges of detections of PFOS and PFOA in soil.

6.3.2 AOI 1 Groundwater Analytical Results

PFOA, PFOS, and PFBS were detected in 13 of the 13 groundwater samples collected in AOI 1.

All PFOA and PFBS results were below SLs. PFOA was detected in 12 of 13 samples and ranged 

in concentrations from non-detect to 13.5 ng/L (14.3 ng/L duplicate), which was detected in AOI1-

MW3. PFOS was detected below the SLs at all well locations with the exception of AOI1-MW3. 

PFOS concentrations ranged from 2.61 J ng/L at BH-02 to 62.2 ng/L (61.6 ng/L duplicate) at AOI1-

MW3. PFBS was detected in 12 of 13 samples and ranged in concentrations from non-detect

(BH-02) to 34.1 ng/L (AOI1-MW3). The detected compounds are summarized in Table 6-5. Figure

6-5 and Figure 6-6 present the range of detections for PFOS and PFOA at the facility. 

6.3.3 AOI 1 Conclusions

Based on the results of SI, PFOA, PFOS, and PFBS were detected in soil at AOI 1; however, the 

detected concentrations were below soil SLs. PFOA and PFBS were detected in groundwater at 

AOI 1, and PFOS exceeded SLs. Therefore, further evaluation at AOI 1 is warranted as part of an 

RI.

6.4 AOI 2

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

2, which includes four potential PFAS release areas: Former Weasel Barn, Excavated Soil from 

Mt. Defensa Ave Drainage Ditch, 1049th Engineer Detachment Building M1, and 1049th

Firefighting Training Area 4. The detected compounds in soil and groundwater are summarized in 

Tables 6-2 through 6-5. The detections of PFOS and PFOAin soil and groundwater are presented 

on Figures 6-1 through 6-6.

6.4.1 AOI 2 Soil Analytical Results

Within the Former Weasel Barn area, soil was sampled at three intervals from soil boring location 

AOI2-SB1; two intervals from hand auger location AOI2-HA6; and one interval from surface 

locations AOI2-SS1 through AOI2-SS5. All PFOA, PFOS, and PFBS results were below SLs. 

PFOA concentrations ranged from non-detect to 0.271 J μg/Kg, which occurred at AOI2-SB1 in 

the shallow interval (0 to 2 feet bgs). PFOS concentrations ranged from 0.181 J μg/Kg in AOI2-

SS3 (0 to 2 feet bgs) to 10.9 μg/Kg in AOI2-HA6 (0 to 2 feet bgs). PFBS concentrations ranged 

from non-detect to 0.07 J μg/Kg in AOI2-HA6 (0 to 2 feet bgs). In the intermediate interval, PFOA 

concentrations ranged from non-detect to 0.087 J μg/Kg, which occurred at AOI2-HA6 (2 to 4 feet 

bgs). PFOS concentrations ranged from 0.046 J μg/Kg in AOI2-SB1 (9 to 11 feet bgs) to 0.572 J 

μg/Kg in AOI2-HA6 (2 to 4 feet bgs). PFBS concentrations ranged from non-detect to 0.036 J 

μg/Kg, which was detected in AOI2-HA6 (2 to 4 feet bgs). In the deep interval, PFOS and PFBS 

were non-detect (AOI2-SB1). PFOS was detected at a concentration of 0.00678 J μg/Kg (18 to 

20 feet bgs). Tables 6-2 through 6-4 summarize the detected compounds in soil. Figure 6-1 and 

Figure 6-2 present ranges of detections of PFOS and PFOA in soil.
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 6-4

Within the Excavated Soil from Mt. Defensa Ave Drainage Ditch area, soil was sampled at two

intervals from hand auger locations AOI2-HA1 through AOI2-HA5. All PFOA, PFOS, and PFBS 

results were below SLs. In the shallow interval (0 to 2 feet bgs), PFOA concentrations ranged 

from non-detect to 0.126 J μg/Kg, which occurred at AOI2-HA5. PFOS concentrations ranged 

from 0.086 J μg/Kg in AOI2-HA2 (0 to 2 feet bgs) to 1.73 μg/Kg in AOI2-HA5 (0 to 2 feet bgs). 

PFBS concentrations ranged from non-detect to 0.059 J μg/Kg, which was detected in AOI2-HA3

(0 to 2 feet bgs). In the intermediate interval (2 to 4 feet bgs), concentrations of PFOA ranged 

from non-detect to 0.083 J μg/Kg, which was detected in AOI2-HA4. PFOS concentrations ranged 

from non-detect to 1.92 μg/Kg, which occurred at AOI2-HA5 (2 to 4 feet bgs). PFBS

concentrations ranged from non-detect to 0.047 J μg/Kg, which occurred in AOI2-HA5 (2 to 4 feet 

bgs). Table 6-2 and Table 6-3 summarize the detected compounds in soil. Figure 6-1 and Figure 

6-2 present ranges of detections of PFOS and PFOA in soil.

Within the 1049th Engineer Detachment Building M1 area, soil was sampled at three intervals 

from soil boring location AOI2-SB2. All PFOA, PFOS, and PFBS results were below SLs. In the 

shallow interval (0 to 2 feet bgs), PFOA was detected at a concentration of 0.042 J μg/Kg. PFOS 

was detected at a concentration of 4.31 J μg/Kg (0 to 2 feet bgs). PFBS was non-detect. In the 

intermediate interval (2 to 11 feet bgs), PFOS and PFBS were non-detect. PFOS was detected at 

a concentration of 0.046 J μg/Kg. In the deep interval (18 to 20 feet bgs), PFOA, PFOS, and PFBS 

were non-detect. Tables 6-2 through 6-4 summarize the detected compounds in soil. Figure 6-1

and Figure 6-2 present ranges of detections of PFOS and PFOA in soil.

Within the 1049th Firefighting Training Area 4, soil was sampled at three intervals from soil boring 

location AOI02-03-SB and one interval from surface locations AOI02-SS6 through AOI02-SS8. All 

PFOA, PFOS, and PFBS results were below SLs. In the shallow interval (0 to 2 feet bgs), PFOA 

and PFBS concentrations were non-detect. PFOS concentrations ranged from non-detect to 

0.807 J μg/Kg, which occurred at AOI02-03-SB-DUP (0 to 2 feet bgs). In the intermediate and 

deep intervals, PFOA, PFOS, and PFBS were non-detect with the exception of a PFOS detection 

of 0.00678 J μg/Kg in the deep interval of AOI2-03-SB (25 to 27 feet bgs). Tables 6-2 through 6-

4 summarize the detected compounds in soil. Figure 6-3 and Figure 6-4 present ranges of 

detections of PFOS and PFOA in soil.

6.4.2 AOI 2 Groundwater Analytical Results

PFOA, PFOS, and PFBS were detected in seven of nine groundwater samples collected in AOI 

2. PFOS exceeded SLs at AOI2-MW1 (118 ng/L). PFOA concentrations ranged from non-detect 

to 14.6 ng/L (AOI2-MW1-DUP). PFOS concentrations ranged from non-detect to 118 ng/L (AOI2-

MW1). PFBS concentrations ranged from non-detect to 27.3 ng/L (AOI2-MW1). The detected 

compounds are summarized in Table 6-5. Figure 6-5 and Figure 6-6 present the range of 

detections for PFOS and PFOA at the facility. 

6.4.3 AOI 2 Conclusions

Based on the results of SI, PFOA, PFOS, and PFBS were detected in soil at AOI 2; however, the 

detected concentrations were below soil SLs. PFOA and PFBS were detected in groundwater at 

AOI 2 and PFOS exceeded SLs. Therefore, further evaluation at AOI 2 is warranted as part of an 

RI.

6.5 AOI 3

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

3, which includes two potential PFAS release area: Planned Structure Fire and 1049th Firefighting 

Training Area 2. The detected compounds in soil and groundwater are summarized in Tables 6-

2 through 6-5. The detections of PFOA and PFOS in soil and groundwater are presented on 

Figures 6-1 through 6-6.
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 6-5

6.5.1 AOI 3 Soil Analytical Results

Within the Planned Structure Fire area, soil was sampled at three intervals from soil boring 

location AOI3-SB1 and two intervals from hand auger location AOI3-HA1. All PFOA, PFOS, and 

PFBS results were below SLs. In the shallow interval (0 to 2 feet bgs), PFOA concentrations 

ranged from non-detect to 0.473 J μg/Kg, which occurred at AOI3-SB1. PFOS concentrations 

ranged from non-detect to 12.3 μg/Kg, which was detected in AOI3-SB1 (0 to 2 feet bgs). PFBS 

concentrations ranged from non-detect to 0.178 J μg/Kg, which was detected in AOI3-SB1 (0 to 

2 feet bgs). In the intermediate interval (2 to 20 feet bgs), PFOA and PFBS were non-detect. 

PFOS was detected at a concentration of 0.056 J μg/Kg in AOI3-SB1 (18 to 20 feet bgs). In the 

deep interval (40 to 42 feet bgs), PFOA was non-detect. PFOS was detected at a concentration 

of 0.021 J μg/Kg in AOI3-SB1 (40 to 42 feet bgs). PFBS was detected at a concentration of 0.147 

J μg/Kg in AOI3-SB1 (40 to 42 feet bgs.). Tables 6-2 through 6-4 summarize the detected 

compounds in soil. Figure 6-1 and Figure 6-2 present ranges of detections of PFOS and PFOA

in soil.

Within the 1049th Firefighting Training Area 2, soil was sampled at one interval from soil boring

location AOI03-02-SB and from surface soil locations AOI03-SS1 through AOI03-SS5. All PFOA, 

PFOS, and PFBS results were below SLs. In the shallow interval (0 to 2 feet bgs), PFOA and 

PFBS concentrations were non-detect. PFOS concentrations ranged from non-detect to 2.91

μg/Kg, which occurred at AOI03-SS3 (0 to 2 feet bgs). Table 6-2 summarizes the detected 

compounds in soil. Figure 6-3 and Figure 6-4 present ranges of detections of PFOS and PFOA 

in soil.

6.5.2 AOI 3 Groundwater Analytical Results

PFOA, PFOS, and PFBS were detected in six of nine groundwater samples collected in AOI 3. 

All PFOA, PFOS, and PFBS results were below SLs. PFOA concentrations ranged from nondetect to 1.71 J ng/L (MW-10). PFOS concentrations ranged from non-detect to 2.32 J ng/L 

(AOI03-MW02). PFBS concentrations ranged from non-detect to 59.2 ng/L (AOI3-MW1). The 

detected compounds are summarized in Table 6-5. Figure 6-5 and Figure 6-6 present the range 

of detections for PFOS and PFOA at the facility.

6.5.3 AOI 3 Conclusions

Based on the results of SI, PFOA, PFOS, and PFBS were detected in soil at AOI 3; however, the 

detected concentrations were below soil SLs. PFOA, PFOS, and PFBS were detected in 

groundwater at AOI 3, but were below groundwater SLs. Therefore, further evaluation at AOI 3 is 

not warranted.
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 6-6

THIS PAGE INTENTIONALLY BLANK
Table 6-2

PFAS Detections in Surface Soil

Site Inspection Report, Fort William Henry Harrison

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

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - 0.043 J 0.043 X ND ND ND ND ND ND ND ND

8:2 FTS - ND ND UX ND ND 0.015 J ND ND ND ND ND

NEtFOSAA - ND ND UX ND ND 0.011 J ND ND ND ND ND

NMeFOSAA - ND ND UX ND ND ND ND ND ND ND ND

PFBA - ND ND UX ND 0.305 J ND ND ND 1.42 ND 0.051 J

PFBS 130000 ND ND UX ND 0.104 J 0.012 J ND ND ND ND ND

PFDA - ND ND UX ND ND ND ND ND ND ND 0.021 J

PFDoA - ND ND UX ND ND ND ND ND ND ND 0.00951 J

PFHpA - 0.015 J ND UX ND 0.163 J 0.043 J ND ND ND ND 0.018 J

PFHxA - 0.197 J 0.068 X 0.03 J 0.618 J ND ND ND ND ND ND

PFHxS - ND ND UX ND 7.97 0.103 J ND ND ND ND 0.011 J

PFNA - ND ND UX ND ND 0.032 J ND ND ND ND 0.066 J

PFOA 130 ND ND UX ND ND 0.122 J ND ND ND ND 0.069 J

PFOS 130 ND ND UX ND 0.751 J 0.664 J ND ND ND 0.082 J 0.386 J

PFPeA - 0.102 J ND UX ND 0.364 J 0.087 J ND ND ND ND ND

PFTeDA - ND ND UX ND ND 0.015 J ND ND ND ND ND

PFTrDA - ND ND UX ND ND 0.00995 J ND ND ND ND ND

PFUnDA - ND ND UX ND ND 0.013 J ND ND ND ND 0.011 J

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

References PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

Interpreted Qualifiers PFNA perfluorononanoic acid

J = Estimated concentration PFOA perfluorooctanoic acid

J+ = Estimated concentration, biased high PFOS perfluorooctanesulfonic acid

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. PFPeA perfluoropentanoic acid

UX/X = The presence or absence of the analyte cannot be substantiated. Acceptance or rejection of the data should be decided by the project team, but exclusion of the data is recommended. PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DL detection limit

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography 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

SS Surface Soil

USEPA United States Environmental Protection Agency

μg/Kg micrograms per Kilogram

- Not applicable

Area of Interest

Sample ID

Sample Date

Depth

AOI1-HA1-0-2

02/12/2019

0 - 2 ft

AOI1-HA2-0-2

02/12/2019

0 - 2 ft

AOI01-04-SB-00-02

10/07/2020

0 - 2 ft 0 - 2 ft

AOI01-05-SB-00-02

10/06/2020

0 - 2 ft

AOI01-06-SB-00-02

10/06/2020

0 - 2 ft

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional 

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on residential scenario for direct ingestion of contaminated soil.

AOI01

A0I1-SB3-0-2

02/20/2019

0 - 2 ft

AOI1-SS1-0-2

02/14/2019

0 - 2 ft

AOI1-SS1-0-2R

05/20/2019

0 - 2 ft

AOI1-SB1-0-2

02/13/2019

0 - 2 ft

AOI1-SB2-0-2

02/15/2019

AECOM 6-7
Table 6-2

PFAS Detections in Surface Soil

Site Inspection Report, Fort William Henry Harrison

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

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - ND ND ND UJ ND ND ND ND ND ND ND

8:2 FTS - ND ND ND UJ ND ND ND ND ND ND ND

NEtFOSAA - ND ND ND UJ 0.014 J ND ND ND ND ND ND

NMeFOSAA - ND ND ND UJ ND ND ND ND ND ND ND

PFBA - ND ND 0.029 J ND ND ND ND ND ND 0.205 J

PFBS 130000 ND ND ND UJ ND 0.010 J ND ND ND ND 1.08

PFDA - ND 0.034 J ND UJ ND ND ND ND ND ND ND

PFDoA - ND ND ND UJ ND 0.016 J ND ND ND ND ND

PFHpA - ND 0.018 J ND UJ 0.023 J 0.026 J ND ND ND ND ND

PFHxA - ND 0.092 J 0.064 J ND ND ND ND ND ND 0.769 J

PFHxS - ND 0.252 J ND UJ 0.058 J 0.068 J ND ND ND ND 4.38

PFNA - ND 0.01 J ND UJ 0.065 J ND ND ND ND ND ND

PFOA 130 ND 0.064 J ND UJ 0.106 J 0.089 J ND ND ND ND 0.166 J

PFOS 130 ND 0.249 J ND UJ 2.23 0.822 J 0.630 J ND ND ND 39.9

PFPeA - ND 0.0099 J ND UJ 0.039 J 0.043 J ND ND ND ND 0.180 J

PFTeDA - ND ND ND UJ ND 0.015 J ND ND ND ND ND

PFTrDA - ND ND ND UJ ND ND ND ND ND ND ND

PFUnDA - ND ND ND UJ ND 0.018 J ND ND ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

References NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

Interpreted Qualifiers PFHxS perfluorohexanesulfonic acid

J = Estimated concentration PFNA perfluorononanoic acid

J+ = Estimated concentration, biased high PFOA perfluorooctanoic acid

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

UX/X = The presence or absence of the analyte cannot be substantiated. Acceptance or rejection of the data should be decided by the project team, but exclusion of the data is recommended. PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DL detection limit

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography 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

SS Surface Soil

USEPA United States Environmental Protection Agency

μg/Kg micrograms per Kilogram

- Not applicable

Area of Interest

Sample ID

Sample Date

Depth

AOI01-SS10-00-02

10/06/2020

0 - 2 ft 0 - 2 ft

AOI1-SS4-0-2

02/14/2019

0 - 2 ft

AOI1-SS2-0-2

02/14/2019

AOI1-SS3-0-2

02/14/2019

0 - 2 ft

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional 

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on residential scenario for direct ingestion of contaminated soil.

AOI01-SS11-00-02

10/07/2020

0 - 2 ft

AOI01

A0I1-SS6-0-2

02/20/2019

0 - 2 ft

AOI01-SS8-00-02

10/06/2020

0 - 2 ft

AOI01-SS9-00-02

10/06/2020

0 - 2 ft

AOI01-SS7-00-02

10/07/2020

AOI1-SS5-0-2

02/14/2019

0 - 2 ft 0 - 2 ft

AECOM 6-8
Table 6-2

PFAS Detections in Surface Soil

Site Inspection Report, Fort William Henry Harrison

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

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - ND ND ND ND ND 0.059 J 0.044 J ND ND ND

8:2 FTS - ND ND ND ND ND ND ND ND ND ND

NEtFOSAA - ND ND ND ND ND ND ND ND ND ND

NMeFOSAA - ND ND ND ND ND ND ND ND ND ND

PFBA - ND ND ND ND ND ND ND ND ND ND

PFBS 130000 ND ND ND ND ND ND 0.059 J ND 0.057 J 0.07 J

PFDA - ND ND ND ND 0.026 J ND ND ND 0.035 J ND

PFDoA - ND ND ND ND ND ND ND ND 0.013 J ND

PFHpA - ND ND ND ND 0.018 J ND 0.029 J 0.02 J 0.066 J 0.124 J

PFHxA - ND ND ND ND 0.066 J 0.029 J 0.151 J 0.053 J 0.179 J 0.351 J

PFHxS - ND ND ND ND 0.042 J 0.025 J 0.118 J 0.05 J 0.628 J 2.27

PFNA - ND ND ND ND ND ND ND 0.013 J ND 0.074 J

PFOA 130 ND ND ND ND ND ND ND 0.042 J 0.126 J 0.265 J

PFOS 130 ND 2.11 0.872 J 1.03 0.217 J 0.086 J 0.233 J 0.407 J 1.73 10.9

PFPeA - ND ND ND ND ND ND ND ND ND 0.154 J

PFTeDA - ND ND ND ND ND ND ND ND 0.016 J ND

PFTrDA - ND ND ND ND ND ND ND ND ND ND

PFUnDA - ND ND ND ND ND ND ND ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

References NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

Interpreted Qualifiers PFHxS perfluorohexanesulfonic acid

J = Estimated concentration PFNA perfluorononanoic acid

J+ = Estimated concentration, biased high PFOA perfluorooctanoic acid

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

UX/X = The presence or absence of the analyte cannot be substantiated. Acceptance or rejection of the data should be decided by the project team, but exclusion of the data is recommended. PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DL detection limit

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography 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

SS Surface Soil

USEPA United States Environmental Protection Agency

μg/Kg micrograms per Kilogram

- Not applicable

AOI01-SS12-00-02

10/07/2020

0 - 2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI2-HA6-0-2

02/12/2019

0 - 2 ft

AOI2-HA4-0-2

02/13/2019

0 - 2 ft

AOI2-HA5-0-2

02/13/2019

0 - 2 ft

AOI01-SS14-00-02

10/07/2020

0 - 2 ft

AOI01-SS15-00-02

10/07/2020

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional 

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on residential scenario for direct ingestion of contaminated soil.

AOI01 AOI02

AOI2-HA3-0-2

02/13/2019

0 - 2 ft

AOI2-HA1-0-2

02/13/2019

0 - 2 ft

AOI2-HA2-0-2

02/13/2019

0 - 2 ft 0 - 2 ft

AOI01-SS13-00-02

10/07/2020

0 - 2 ft

AECOM 6-9
Table 6-2

PFAS Detections in Surface Soil

Site Inspection Report, Fort William Henry Harrison

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

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - 0.022 J 0.027 J ND ND ND ND 0.023 J ND ND ND

8:2 FTS - ND 0.014 J ND ND ND 0.033 J ND ND ND ND

NEtFOSAA - ND 0.013 J ND ND ND ND ND ND ND ND

NMeFOSAA - ND ND ND ND ND ND 0.029 J ND ND ND

PFBA - 0.212 J ND 0.051 J ND ND 0.215 J ND ND 0.071 J ND

PFBS 130000 0.039 J ND ND ND ND 0.03 J ND ND 0.00705 J ND

PFDA - 0.041 J 0.08 J ND ND ND ND ND 0.024 J 0.012 J 0.03 J

PFDoA - ND 0.026 J ND ND ND 0.00614 J ND ND ND ND

PFHpA - 0.145 J 0.018 J 0.055 J ND ND 0.085 J 0.012 J 0.00955 J 0.013 J ND

PFHxA - 0.392 J ND 0.096 J ND ND ND ND ND ND ND

PFHxS - 0.684 J 0.131 J 0.289 J ND ND 0.193 J 0.025 J 0.038 J 0.032 J 0.069 J

PFNA - 0.084 J 0.035 J 0.141 J ND ND 0.074 J 0.03 J 0.025 J ND 0.048 J

PFOA 130 0.271 J 0.042 J 0.135 J ND ND 0.132 J ND 0.055 J ND 0.098 J

PFOS 130 4.14 4.31 J 22 J 0.602 J 0.807 J 2.22 0.893 J 0.758 J 0.181 J 1.09 J+

PFPeA - 0.228 J ND ND ND ND 0.421 J ND ND 0.14 J ND

PFTeDA - ND 0.014 J ND ND ND ND ND ND ND ND

PFTrDA - ND ND ND ND ND ND ND ND ND ND

PFUnDA - 0.015 J 0.022 J ND ND ND ND 0.00894 J ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

References NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

Interpreted Qualifiers PFHxS perfluorohexanesulfonic acid

J = Estimated concentration PFNA perfluorononanoic acid

J+ = Estimated concentration, biased high PFOA perfluorooctanoic acid

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

UX/X = The presence or absence of the analyte cannot be substantiated. Acceptance or rejection of the data should be decided by the project team, but exclusion of the data is recommended. PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DL detection limit

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography 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

SS Surface Soil

USEPA United States Environmental Protection Agency

μg/Kg micrograms per Kilogram

- Not applicable

AOI2-SS4-0-2

05/20/2019

0 - 2 ft

AOI2-SB1-0-2

05/21/2019

0 - 2 ft

AOI2-SS2-0-2

05/20/2019

0 - 2 ft

AOI02-03-SB-00-02

10/06/2020

AOI02-03-SB-00-02-DUP

10/06/2020

0 - 2 ft 0 - 2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI02

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional 

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on residential scenario for direct ingestion of contaminated soil.

AOI2-SS3-0-2

05/20/2019

0 - 2 ft

AOI2-SS1-0-2

05/20/2019

0 - 2 ft

AOI2-SB2-0-2-DUP

05/23/2019

0 - 2 ft

AOI2-SB2-0-2

05/23/2019

0 - 2 ft

AOI2-SS2-0-2-DUP

05/20/2019

0 - 2 ft

AECOM 6-10
Table 6-2

PFAS Detections in Surface Soil

Site Inspection Report, Fort William Henry Harrison

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

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - ND ND ND ND 0.021 J ND ND ND ND ND

8:2 FTS - ND ND ND ND ND ND 0.103 J ND ND ND

NEtFOSAA - 0.00995 J ND ND ND ND ND ND ND ND ND

NMeFOSAA - ND ND ND ND ND ND ND ND ND ND

PFBA - ND ND ND ND ND ND 0.181 J ND ND ND

PFBS 130000 ND ND ND ND 0.178 J ND 0.103 J ND ND ND

PFDA - ND ND ND ND ND ND 0.024 J ND ND ND

PFDoA - ND ND ND ND ND ND ND ND ND ND

PFHpA - 0.021 J ND ND ND 0.04 J ND 0.698 J ND ND ND

PFHxA - ND 0.165 J 0.282 J ND 1.05 J ND 0.792 J ND ND ND

PFHxS - 0.062 J 0.213 J 0.259 J 0.274 J 0.345 J ND 5.02 ND ND 0.278 J

PFNA - 0.048 J ND ND ND ND ND 0.110 J ND ND ND

PFOA 130 0.08 J ND ND ND 0.043 J ND 0.473 J ND ND ND

PFOS 130 0.679 J 0.678 J ND 0.617 J 0.308 J ND 12.3 ND 0.438 J 2.91

PFPeA - ND ND ND ND 1.3 ND 0.248 J ND ND ND

PFTeDA - ND ND ND ND 0.012 J ND ND ND ND ND

PFTrDA - ND ND ND ND ND ND ND ND ND ND

PFUnDA - ND ND ND ND ND ND ND ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

References NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

Interpreted Qualifiers PFHxS perfluorohexanesulfonic acid

J = Estimated concentration PFNA perfluorononanoic acid

J+ = Estimated concentration, biased high PFOA perfluorooctanoic acid

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

UX/X = The presence or absence of the analyte cannot be substantiated. Acceptance or rejection of the data should be decided by the project team, but exclusion of the data is recommended. PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DL detection limit

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography 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

SS Surface Soil

USEPA United States Environmental Protection Agency

μg/Kg micrograms per Kilogram

- Not applicable

AOI3-HA1-0-2

02/12/2019

0 - 2 ft

AOI02-SS7-00-02

10/06/2020

0 - 2 ft

AOI02-SS8-00-02

10/06/2020

0 - 2 ft

AOI03

AOI03-SS3-00-02

10/7/2020

0 - 2 ft

AOI03-SS1-00-02

10/07/2020

0 - 2 ft

AOI03-SS2-00-02

10/07/2020

0 - 2 ft

AOI03-02-SB-00-02

10/06/2020

0 - 2 ft

AOI3-SB1-0-2

05/22/2019

0 - 2 ft

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional 

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on residential scenario for direct ingestion of contaminated soil.

AOI2-SS5-0-2

05/20/2019

0 - 2 ft

Area of Interest AOI02

Sample ID

Sample Date

Depth

AOI02-SS6-00-02

10/06/2020

0 - 2 ft

AECOM 6-11
Table 6-2

PFAS Detections in Surface Soil

Site Inspection Report, Fort William Henry Harrison

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - ND ND ND

8:2 FTS - ND ND ND

NEtFOSAA - ND ND ND

NMeFOSAA - ND ND ND

PFBA - ND ND ND

PFBS 130000 ND ND ND

PFDA - ND ND ND

PFDoA - ND ND ND

PFHpA - ND ND ND

PFHxA - ND ND ND

PFHxS - ND ND ND

PFNA - ND ND ND

PFOA 130 ND ND ND

PFOS 130 0.764 J 0.936 J 0.215 J

PFPeA - ND ND ND

PFTeDA - ND ND ND

PFTrDA - ND ND ND

PFUnDA - ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

References NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

Interpreted Qualifiers PFHxS perfluorohexanesulfonic acid

J = Estimated concentration PFNA perfluorononanoic acid

J+ = Estimated concentration, biased high PFOA perfluorooctanoic acid

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

UX/X = The presence or absence of the analyte cannot be substantiated. Acceptance or rejection of the data should be decided by the project team, but exclusion of the data is recommended. PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DL detection limit

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography 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

SS Surface Soil

USEPA United States Environmental Protection Agency

μg/Kg micrograms per Kilogram

- Not applicable

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional 

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on residential scenario for direct ingestion of contaminated soil.

AOI03-SS4-00-02

10/07/2020

0 - 2 ft

AOI03

AOI03-SS5-00-02

10/07/2020

0 - 2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI03-SS4-00-02-DUP

10/07/2020

0 - 2 ft

AECOM 6-12
Table 6-3

PFAS Detections in Shallow Subsurface Soil

Site Inspection Report, Fort William Henry Harrison

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

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS - 0.058 J 0.041 J ND 0.041 J ND 0.046 J 0.026 J ND 0.019 J ND

NEtFOSAA - 0.018 J ND ND ND ND ND ND ND ND ND

PFBA - ND ND ND ND 0.069 J 0.168 J ND ND ND ND

PFBS 1600000 0.00547 J ND 0.0085 J ND 0.00808 J 0.027 J ND 0.047 J 0.036 J 0.031 J

PFDA - ND ND ND ND ND 0.015 J ND ND ND 0.021 J

PFDoA - 0.013 J ND ND ND ND ND ND 0.018 J ND ND

PFHpA - 0.01 J ND ND ND 0.011 J 0.022 J 0.054 J ND 0.072 J 0.054 J

PFHxA - 0.061 J 0.035 J ND 0.057 J ND 0.146 J 0.141 J 0.144 J 0.263 J 0.22 J

PFHxS - ND ND 0.129 J ND 0.011 J ND 0.091 J 0.307 J 0.285 J 0.25 J

PFNA - ND ND ND ND ND ND 0.037 J 0.043 J 0.019 J ND

PFOA 1600 ND ND ND ND ND ND 0.083 J ND 0.087 J 0.081 J

PFOS 1600 ND ND 0.135 J ND 0.032 J 0.12 J 0.326 J 1.92 0.572 J 0.489 J

PFPeA - ND ND ND ND ND 0.116 J ND ND 0.143 J 0.093 J

PFTeDA - ND ND ND ND ND ND 0.022 J 0.013 J ND ND

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

References PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

Interpreted Qualifiers PFOS perfluorooctanesulfonic acid

J = Estimated concentration PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LOD Limit of Detection

LCMSMS Liquid Chromatography Mass Spectrometry

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

- Not applicable

Area of Interest

Sample ID

Sample Date

Depth

AOI1-HA1-2-4

02/12/2019

2 - 4 ft

AOI1-HA2-2-4

02/12/2019

2 - 4 ft

02/13/2019

2 - 4 ft

AOI2-HA1-2-4

02/13/2019

2 - 4 ft

AOI2-HA2-2-4

02/13/2019

2 - 4 ft

AOI2-HA2-2-4-DUP

2/13/2019

2 - 4 ft

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s 

Regional Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on industrial/commercial composite worker scenario for

incidental ingestion of contaminated soil.

AOI01 AOI02

AOI2-HA6-2-4-DUP

02/12/2019

2 - 4 ft

AOI2-HA6-2-4

02/12/2019

2 - 4 ft

AOI2-HA5-2-4

02/13/2019

2 - 4 ft

AOI2-HA3-2-4

02/13/2019

2 - 4 ft

AOI2-HA4-2-4

AECOM 6-13
Table 6-3

PFAS Detections in Shallow Subsurface Soil

Site Inspection Report, Fort William Henry Harrison

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (ug/Kg)

6:2 FTS - ND 0.019 J ND ND ND

NEtFOSAA - ND ND ND ND ND

PFBA - ND ND ND ND ND

PFBS 1600000 ND ND ND ND 0.00739 J

PFDA - ND ND ND ND ND

PFDoA - ND ND ND ND ND

PFHpA - ND ND ND ND ND

PFHxA - ND ND ND ND ND

PFHxS - 0.012 J 0.212 J ND ND 0.06 J

PFNA - ND 0.00501 J ND ND ND

PFOA 1600 ND ND ND ND 0.034 J

PFOS 1600 0.046 J 0.161 J ND ND 0.244 J

PFPeA - ND ND ND ND ND

PFTeDA - ND ND ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

References PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

Interpreted Qualifiers PFOA perfluorooctanoic acid

J = Estimated concentration PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DUP Duplicate

ft feet

HA Hand auger

HQ Hazard quotient

ID identification

LOD Limit of Detection

LCMSMS Liquid Chromatography Mass Spectrometry

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

- Not applicable

AOI03

AOI3-HA1-2-4

02/12/2019

2 - 4 ft

AOI02-03-SB-10-12-DUP

10/10/2020

10 - 12 ft

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s Regional

Screening Level Calculator. HQ=0.1. 15 October 2019. Soil screening levels based on industrial/commercial composite worker scenario for incidental 

ingestion of contaminated soil.

AOI02

AOI02-03-SB-10-12

10/10/2020

10 - 12 ft

AOI2-SB2-8-10

05/23/2019

8 - 10 ft

AOI2-SB1-9-11

05/21/2019

9 - 11 ft

Area of Interest

Sample ID

Sample Date

Depth

AECOM 6-14
Table 6-4

PFAS Detections in Deep Subsurface Soil

Site Inspection Report, Fort William Henry Harrison

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS 0.051 J ND ND ND ND ND ND ND ND

8:2 FTS ND ND ND ND 0.117 J ND ND ND ND

NEtFOSAA ND ND ND ND 0.135 J ND 0.025 J ND ND

NMeFOSAA ND ND ND ND 0.136 J ND 0.02 J ND ND

PFBA 0.00848 J ND ND ND ND ND ND ND ND

PFBS 0.00418 J ND 0.142 J ND 0.021 J ND ND ND ND

PFDA 0.014 J 0.013 J ND ND ND ND ND ND ND

PFDoA 0.00994 J ND ND ND 0.233 J ND 0.013 J ND ND

PFHpA ND ND ND ND 0.021 J 0.00431 J 0.011 J ND ND

PFHxA 0.035 J ND 0.226 J 0.059 J ND ND ND ND ND

PFHxS ND ND 0.916 J ND 0.034 J ND 0.033 J ND ND

PFOA ND ND 0.055 J ND ND ND ND ND ND

PFOS 0.039 J 0.014 J 0.478 J ND 0.526 J ND 0.135 J ND ND

PFPeA ND ND ND ND ND ND ND ND ND

PFTeDA ND ND ND ND 0.13 J 0.012 J 0.015 J ND ND

PFTrDA ND ND ND ND 0.238 J 0.00534 J ND ND ND

PFUnDA 0.00496 J ND ND ND 0.14 J ND ND ND ND

Interpreted Qualifiers Chemical Abbreviations

J = Estimated concentration 6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DUP Duplicate

ft feet

ID identification

LCMSMS Liquid Chromatography Mass Spectrometry

LOD Limit of Detection

ND Analyte not detected above the LOD

QSM Quality Systems Manual

Qual Interpreted Qualifier

SB Soil boring

μg/Kg micrograms per Kilogram

A0I1-SB3-38-40

02/20/2019

38 - 40 ft

AOI01-04-SB-15-17

10/09/2020

15 - 17 ft

AOI01-04-SB-30-32

10/09/2020

30 - 32 ft

AOI01

AOI1-SB2-28-30

02/15/2019

28 - 30 ft

AOI1-SB1-38-40

02/13/2019

38 - 40 ft

AOI1-SB2-15-17

02/15/2019

15 - 17 ft

AOI1-SB1-20-22

02/13/2019

20 - 22 ft

A0I1-SB3-18-20

02/20/2019

18 - 20 ft

A0I1-SB3-18-20-DUP

02/20/2019

18 - 20 ft

AECOM 6-15
Table 6-4

PFAS Detections in Deep Subsurface Soil

Site Inspection Report, Fort William Henry Harrison

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual Result Qual Result Qual

Soil, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (μg/Kg)

6:2 FTS ND ND ND ND ND 0.014 J ND ND ND

8:2 FTS ND ND ND ND ND 0.00707 J ND ND ND

NEtFOSAA ND ND ND ND ND ND ND ND ND

NMeFOSAA ND ND ND ND ND ND ND ND ND

PFBA ND ND ND ND ND ND ND ND 0.059 J

PFBS ND ND ND ND ND 0.00186 J ND ND 0.147 J

PFDA ND ND ND ND ND ND ND ND ND

PFDoA ND ND ND ND ND ND ND ND ND

PFHpA ND ND ND ND ND ND ND ND 0.022 J

PFHxA ND ND ND ND ND ND ND 0.046 J 0.314 J

PFHxS ND ND ND ND ND 0.029 J ND 0.00812 J 0.128 J

PFOA ND ND ND ND ND ND ND ND ND

PFOS ND ND ND ND 0.00678 J ND 0.237 J 0.056 J 0.021 J

PFPeA ND ND ND ND ND ND ND ND 0.129 J

PFTeDA ND ND ND ND ND ND ND ND ND

PFTrDA ND ND ND ND ND ND ND ND ND

PFUnDA ND ND ND ND ND ND ND ND ND

Interpreted Qualifiers Chemical Abbreviations

J = Estimated concentration 6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

NEtFOSAA N-ethyl perfluorooctane- sulfonamidoacetic acid

NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFDoA perfluorododecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

Acronyms and Abbreviations

AOI Area of Interest

DUP Duplicate

ft feet

ID identification

LCMSMS Liquid Chromatography Mass Spectrometry

LOD Limit of Detection

ND Analyte not detected above the LOD

QSM Quality Systems Manual

Qual Interpreted Qualifier

SB Soil boring

μg/Kg micrograms per Kilogram

AOI01

15 - 17 ft 30 - 32 ft 15 - 17 ft 30 - 32 ft

05/22/2019

AOI01-05-SB-15-17 AOI01-05-SB-30-32 AOI01-06-SB-15-17 AOI01-06-SB-30-32

10/08/2020 10/08/2020 10/09/2020 10/09/2020

18 - 20 ft

AOI02-03-SB-25-27

10/10/2020

25 - 27 ft

AOI02 AOI03

AOI2-SB1-18-20

05/21/2019

18 - 20 ft

AOI3-SB1-40-42

05/22/2019

40 - 42 ft

AOI2-SB2-18-20

05/23/2019

18 - 20 ft

AOI3-SB1-18-20

AECOM 6-16
Table 6-5

PFAS Detections in Groundwater

Site Inspection Report, Fort William Henry Harrison

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

Water, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (ng/L)

6:2 FTS - ND ND ND ND ND 3.24 J ND ND ND ND

PFBA - 4.52 J ND 8.34 J 9.18 17.2 30.2 25.9 27.1 2.90 J 18.4

PFBS 40000 3.16 J 3.00 J 4.52 J 4.74 J 11.2 34.1 23.1 25.8 3.24 J 21.7

PFDA - ND UJ ND ND ND ND ND UJ ND ND ND ND

PFHpA - 1.83 J ND 4.00 J 3.84 J 4.90 J 22.4 23.0 23.8 ND 11.5

PFHxA - 7.81 4.32 J 15.2 15.2 33.4 80.9 72.6 84.2 5.05 J 53.3

PFHxS - 22.3 21.0 33.9 34.3 18.0 213 184 J+ 197 J+ 12.2 77.0

PFNA - ND ND ND ND ND ND ND ND ND ND

PFOA 40 1.17 J 2.10 J 4.58 J 4.43 J 2.75 J 12.4 J+ 13.5 14.3 2.34 J 8.19 J

PFOS 40 8.82 5.53 J 29.2 27.3 25.4 24.8 62.2 61.6 5.26 J 34.4

PFPeA - 9.46 4.68 J 16.7 16.7 47.3 103 78.6 88.6 6.51 J 56.5

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

References PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

Interpreted Qualifiers

J = Estimated concentration Acronyms and Abbreviations

J- = Estimated concentration, biased low AOI Area of Interest

J+ = Estimated concentration, biased high DL detection limit

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

GW Groundwater

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography Mass Spectrometry

LOD Limit of Detection

MW monitoring well

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

- Not applicable

AOI1-MW1-GW

10/11/2020

AOI01-MW05-GW

10/12/2020

Area of Interest

Sample ID

Sample Date

AOI01-MW04-GW

10/14/2020

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s 

Regional Screening Level Calculator. HQ=0.1. 15 October 2019. Groundwater screening levels based on residential scenario for direct ingestion of

groundwater.

AOI01

AOI1-MW3-GW-DUP

10/10/2020

AOI1-MW3-GW

10/10/2020

AOI1-MW2-GW

10/12/2020

AOI1-MW3

05/25/2019

AOI1-MW2

05/29/2019

AOI1-MW2-DUP

05/29/2019

AOI1-MW1

05/28/2019

AECOM 6-17
Table 6-5

PFAS Detections in Groundwater

Site Inspection Report, Fort William Henry Harrison

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

Water, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (ng/L)

6:2 FTS - ND ND ND ND ND ND ND ND ND ND

PFBA - 11.6 6.30 4.02 J 7.59 6.42 J 36.2 41.6 43.2 3.74 J ND

PFBS 40000 14.7 1.66 J ND 2.65 J 2.06 J 27.3 16.5 17.5 1.36 J ND

PFDA - ND 1.74 J ND ND ND ND ND ND ND ND

PFHpA - 15.7 2.69 J ND 3.97 J 3.90 J 19.0 21.8 23.0 ND ND

PFHxA - 25.2 10.2 7.25 J 13.8 11.6 102 J- 108 109 3.03 J ND

PFHxS - 114 5.06 4.89 J 16.7 20.4 155 J- 154 153 27.6 1.86 J

PFNA - 1.71 J 0.861 J ND ND ND 1.86 J ND ND ND ND

PFOA 40 9.16 J 4.68 J+ ND 7.31 J+ 7.25 J 10.7 J+ 12.6 14.6 3.07 J+ ND

PFOS 40 34.2 6.88 2.61 J 9.25 8.74 J 118 89.4 110 9.14 4.67 J

PFPeA - 21.6 10.2 7.30 J 16.5 13.1 121 151 153 ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

References PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

Interpreted Qualifiers

J = Estimated concentration Acronyms and Abbreviations

J- = Estimated concentration, biased low AOI Area of Interest

J+ = Estimated concentration, biased high DL detection limit

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

GW Groundwater

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography Mass Spectrometry

LOD Limit of Detection

MW monitoring well

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

- Not applicable

Area of Interest

Sample ID

Sample Date

BH-02

05/28/2019 10/11/2020

FH-02

05/28/2019

BH-02-101020

10/10/2020

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s 

Regional Screening Level Calculator. HQ=0.1. 15 October 2019. Groundwater screening levels based on residential scenario for direct ingestion of

groundwater.

AOI01 AOI02

AOI01-MW06-GW

10/13/2020

AOI2-MW1-GW

10/12/2020

AOI2-MW1-GW-DUP

10/12/2020

AOI2-MW2-GW

10/13/2020

AOI2-MW1

05/29/2019

AOI2-MW2

5/30/2019

FH-02-101120

AECOM 6-18
Table 6-5

PFAS Detections in Groundwater

Site Inspection Report, Fort William Henry Harrison

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

Water, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (ng/L)

6:2 FTS - ND ND ND ND ND ND ND ND ND ND

PFBA - 39.2 10.4 ND ND 45.3 45.8 14.8 4.84 J ND 3.38 J

PFBS 40000 17.2 ND ND ND 20.9 14.6 59.2 18.5 2.07 J ND

PFDA - ND ND ND ND ND ND ND ND ND ND

PFHpA - 24.6 ND ND ND 20.6 25.3 1.60 J ND ND 2.47 J

PFHxA - 87.2 ND 1.82 J 1.74 J 112 116 48.7 16.8 2.40 J 3.52 J

PFHxS - 113 1.99 J ND 2.17 J 69.9 88.3 5.66 J 3.91 J 5.86 J 2.66 J

PFNA - ND ND ND ND ND ND ND ND ND ND

PFOA 40 10.0 ND ND ND 10.8 J+ 12.8 ND ND ND 1.71 J+

PFOS 40 6.29 J 1.83 J ND ND 8.74 8.50 J 1.63 J 2.28 J 2.32 J ND

PFPeA - 152 ND ND ND 171 178 15.4 5.85 J ND 4.65 J

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

References PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

Interpreted Qualifiers

J = Estimated concentration Acronyms and Abbreviations

J- = Estimated concentration, biased low AOI Area of Interest

J+ = Estimated concentration, biased high DL detection limit

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

GW Groundwater

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography Mass Spectrometry

LOD Limit of Detection

MW monitoring well

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

- Not applicable

MW-10

05/29/2019

AOI3-MW1-GW

10/09/2020

AOI3-MW1

05/29/2019

AOI03-MW02-GW

10/14/2020 10/13/2020

Area of Interest

Sample ID

Sample Date

MW-08-101120

10/11/2020

AOI02 AOI03

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s 

Regional Screening Level Calculator. HQ=0.1. 15 October 2019. Groundwater screening levels based on residential scenario for direct ingestion of

groundwater.

MW-08

05/29/2019

MW-06-DUP

05/29/2019

MW-07

05/30/2019

MW-06

05/29/2019

AOI02-MW03-GW

AECOM 6-19
Table 6-5

PFAS Detections in Groundwater

Site Inspection Report, Fort William Henry Harrison

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual

Water, PFAS by LCMSMS Compliant with QSM 5.1 Table B-15 (ng/L)

6:2 FTS - ND ND ND ND ND

PFBA - 5.03 2.23 J 5.32 ND ND

PFBS 40000 ND ND ND ND ND

PFDA - ND ND ND ND ND

PFHpA - ND ND ND ND ND

PFHxA - 5.11 2.71 J 1.36 J ND ND

PFHxS - 2.27 J ND 0.955 J ND ND

PFNA - ND ND ND ND ND

PFOA 40 ND ND ND ND ND

PFOS 40 ND ND 1.10 J ND ND

PFPeA - 6.49 ND ND ND ND

Grey Fill Detected concentration exceeded OSD Screening Level Chemical Abbreviations

6:2 FTS 6:2 fluorotelomer sulfonate

PFAS per- and polyfluoroalkyl substances

PFBA perfluorobutanoic acid

References PFBS perfluorobutanesulfonic acid

PFDA perfluorodecanoic acid

PFHpA perfluoroheptanoic acid

PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PFPeA perfluoropentanoic acid

Interpreted Qualifiers

J = Estimated concentration Acronyms and Abbreviations

J- = Estimated concentration, biased low AOI Area of Interest

J+ = Estimated concentration, biased high DL detection limit

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

GW Groundwater

HQ Hazard quotient

ID identification

LCMSMS Liquid Chromatography Mass Spectrometry

LOD Limit of Detection

MW monitoring well

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

- Not applicable

10/09/2020

a. Assistant Secretary of Defense, 2019. Risk Based Screening Levels Calculated for PFOS, PFOA, PFBS in Groundwater or Soil using USEPA’s 

Regional Screening Level Calculator. HQ=0.1. 15 October 2019. Groundwater screening levels based on residential scenario for direct ingestion of

groundwater.

PH-1

05/30/2019

PH-2-DUP

05/30/2019

MW-11

05/30/2019

OBTMW-01

05/30/2019

Area of Interest

Sample ID

Sample Date

MW-11-100920

AECOM 6-20
AOI01-MW02 AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

AOI01-MW02 AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-HA2 AOI01-HA1 AOI03-HA1

AOI02-HA6

AOI01-MW01

AOI02-HA1 AOI02-HA2

AOI02-HA3

AOI02-HA4 AOI02-HA5

AOI01-MW02

AOI01-MW03

AOI02-MW01

AOI02-SS2

AOI02-SS4

AOI02-SS5

AOI02-SS3

AOI02-SS1

AOI03-MW01

AOI01-SS6

AOI02-MW02

AOI01-HA2 AOI01-HA1

AOI03-HA1

AOI02-HA6

AOI01-SS1

AOI01-SS3

AOI01-SS2

AOI01-SS4

AOI01-MW01

AOI01-SS5

AOI02-HA1 AOI02-HA2

AOI02-HA3

AOI02-HA4 AOI02-HA5

0 390 780 1,560

Feet

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

AB

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

1:9,360 Figure 6-1

PFOS Detections in Soil 

During SI Mobilization 1 (AOI 1-3)

12420 Milestone Center Drive

­ Germantown, MD 20876

Shallow Intermediate Deep

Facility Boundary PFOS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

6-21
AOI01-MW02 AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

AOI01-MW02 AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI1-HA2 AOI1-HA1

AOI3-HA1

AOI2-HA6

AOI01-MW01

AOI2-HA1 AOI2-HA2

AOI2-HA4 AOI2-HA3

AOI2-HA5

AOI01-MW02

AOI01-MW03

AOI02-MW01

AOI02-SS2

AOI02-SS4

AOI02-SS5

AOI02-SS3

AOI02-SS1

AOI03-MW01

AOI01-SS6

AOI02-MW02

AOI01-HA2 AOI01-HA1

AOI03-HA1

AOI02-HA6

AOI01-SS1

AOI01-SS3

AOI01-SS2

AOI01-SS4

AOI01-MW01

AOI01-SS5

AOI02-HA1 AOI02-HA2

AOI02-HA3

AOI02-HA4

AOI02-HA5

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

JH

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

1:9,360 Figure 6-2

PFOA Detections in Soil 

During SI Mobilization 1 (AOI 1-3)

12420 Milestone Center Drive

­ Germantown, MD 20876

Shallow Intermediate Deep

0 390 780 1,560

Feet

Facility Boundary PFOA Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

6-22
AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI02-MW03

AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI02-MW03

AOI01-SS7

AOI01-MW04

AOI01-SS11

AOI01-SS12

AOI01-SS13

AOI01-SS14

AOI01-SS15

AOI01-MW05

AOI01-SS8

AOI01-SS9

AOI01-SS10

AOI01-MW06

AOI02-SS8

AOI02-MW03 AOI02-SS6

AOI02-SS7

AOI03-SS5

AOI03-SS4

AOI03-MW02

AOI03-SS3

AOI03-SS1

AOI03-SS2

0 390 780 1,560

Feet

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

AB

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

1:9,360 Figure 6-3

PFOS Detections in Soil 

During SI Mobilization 2 (AOI 1-3)

12420 Milestone Center Drive

­ Germantown, MD 20876

Shallow Intermediate Deep

Facility Boundary PFOS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

6-23
AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI02-MW03

AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI02-MW03

AOI01-SS7

AOI01-MW04

AOI01-SS11

AOI01-SS12

AOI01-SS13

AOI01-SS14

AOI01-SS15

AOI01-MW05

AOI01-SS8

AOI01-SS9

AOI01-SS10

AOI01-MW06

AOI02-SS8

AOI02-SS6 AOI02-MW03

AOI02-SS7

AOI03-SS5

AOI03-SS4

AOI03-MW02

AOI03-SS3

AOI03-SS1

AOI03-SS2

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

JH

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

1:9,360 Figure 6-4

PFOA Detections in Soil 

During SI Mobilization 2 (AOI 1-3)

12420 Milestone Center Drive

­ Germantown, MD 20876

Shallow Intermediate Deep

0 390 780 1,560

Feet

Facility Boundary PFOA Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

6-24
BH-02

FH-02

OBTMW-01 MW-10

MW-08

MW-06 MW-07

MW-11

PH-1

AOI01-MW02

AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

BH-02

FH-02

OBTMW-01 MW-10

MW-08

MW-06 MW-07

MW-11

PH-1

AOI01-MW02

AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

JH

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

Figure 6-5

PFOA and PFOS Detections in Groundwater 

During SI Mobilization 1 (AOI 1-3) May 25-30, 2019

12420 Milestone Center Drive

Germantown, MD 20876

PFOA PFOS

PFOA Results (ng/L)

ND

>ND - 10

>10 - 40

>40 - 70

>70 - 400

>400

PFOS Results (ng/L)

ND

>ND - 10

>10 - 40

>40 - 70

70 - 400

>400

0 300 600 1,200

Feet

Legend

Facility Boundary

1:7,200 Groundwater Flow Direction ­

6-25
BH-02

FH-02

MW-08

MW-11

AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI02-MW03

AOI03-MW02

AOI01-MW02 AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

BH-02

FH-02

MW-08

MW-11

AOI01-MW04

AOI01-MW05

AOI01-MW06

AOI02-MW03

AOI03-MW02

AOI01-MW02 AOI01-MW03

AOI02-MW01

AOI03-MW01

AOI02-MW02

AOI01-MW01

0 300 600 1,200

Feet

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection for PFAS at Fort William Henry Harrison, MT

6/7/2021

6/7/2021

6/7/2021

MS

JH

CM

GIS BY

CHK BY

PM

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

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

6/7/2021

Figure 6-6

PFOA and PFOS Detections in Groundwater 

During SI Mobilization 2 (AOI 1-3) October 9-14, 2020

12420 Milestone Center Drive

Germantown, MD 20876

PFOA PFOS

PFOA Results (ng/L)

ND

>ND - 10

>10 - 40

>40 - 70

>70 - 400

>400

PFOS Results (ng/L)

ND

>ND - 10

>10 - 40

>40 - 70

>70 - 400

>400

­ Legend

Facility Boundary

1:6,992 Groundwater Flow Direction

6-26
Site Inspection Report

Fort William Henry Harrison, MT

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. 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 

PFOA, PFOS, or PFBS 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 

PFOA, PFOS, or PFBS above the SLs. Areas with an identified potentially complete pathway may 

warrant further investigation. In general, the potential routes of exposure to PFAS 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 PFAS toxicological study. The 

receptors evaluated are consistent with those listed in USEPA guidance for risk screening 

(USEPA, 2001). Receptors include site workers (e.g., facility staff and visiting soldiers), 

construction workers, trespassers, residents outside the facility boundary, and recreational users

outside of the facility boundary. 

7.1 Soil Exposure Pathway

The SI results for PFOA, PFOS, and PFBS in soil were used to determine whether a potentially 

complete pathway exists between the source and potential receptors at each AOI based on the 

aforementioned criteria.

7.1.1 AOI 1

From approximately 1995 to 2003, AFFF was released by the MTARNG to soil in AOI 1 through 

firetruck washing and emptying near the 1049th Engineer Detachment Building (1010 Building) 

into the Mt. Defensa Avenue Drainage Ditch. In addition, the 1049th also trained with foam in the 

Navy Parking Lot north of AOI1-MW1 (1049th Firefighting Training Area 1) and in the channel 

area east of AOI1-MW2 before the channel was excavated (1049th Firefighting Training Area 3). 

Specific details regarding the frequency, volume, chemical composition, and concentration of any 

potential AFFF used at either FTA are not known. There is adjacent, offsite potential PFAS 

releases that have occurred upgradient of FTWHH near this ditch from VA fire department 

activities. PFOA, PFOS, and PFBS were detected in soil in this AOI 1; however, concentrations 

were below SLs. Based on the results of the SI in AOI 1, ground-disturbing activities could 

potentially result in site worker, construction worker, trespasser, resident, and recreational user 

exposure to PFOA, PFOS, and PFBS via inhalation of dust. Ground-disturbing activities could 

potentially result in site worker, construction worker, trespasser, and recreational user exposure 
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 7-2

to PFOA, PFOS, and PFBS via ingestion of surface soil. Additionally, ground-disturbing activities 

to subsurface soil could potentially result in construction worker exposure. No current construction 

is occurring at AOI 1. Additionally, off-facility residents may potentially be exposed to PFOA, 

PFOS, and PFBS via inhalation of dust caused by on-facility ground disturbing activities, although 

this exposure is likely insignificant. The CSM for AOI 1 is presented on Figure 7-1.

7.1.2 AOI 2

AFFF was released to soil at three potential PFAS release areas within the AOI 2. The Former 

Weasel Barn located in the northeast section of the Cantonment Area, north of Sanananda Drive, 

was demolished in the winter of 2002 as part of a fire training exercise. Due to flooding of the Mt. 

Defensa Avenue Drainage Ditch (in AOI 1) during rapid snowmelt and large rainfall events, the 

central portion of the ditch was widened in 2016 via excavation. Excavated soil was used to create 

a vehicle staging area in AOI 2, adjacent to the retention pond. AFFF was stored at the MTARNG 

1049th Engineer Detachment buildings. Due to the corrosive nature of AFFF to the firetruck 

storage tanks, AFFF was added just prior to imminent use. The firetrucks were washed near 

Building M1. In addition, the 1049th trained with foam in the parking lot south of MW-08. Specific 

details regarding the frequency, volume, chemical composition, and concentration of any potential 

AFFF used at the FTA are not known. PFAS were detected in soil in this area; however, 

concentrations were below SLs. Based on the results of the SI in AOI 2, ground-disturbing 

activities could potentially result in site worker, construction worker, trespasser, resident, and 

recreational user exposure to PFOA, PFOS, and PFBS via inhalation of dust. Ground-disturbing 

activities could potentially result in site worker, construction worker, trespasser, and recreational 

user exposure to PFOA, PFOS, and PFBS via ingestion of surface soil. Additionally, grounddisturbing activities to subsurface soil could potentially result in construction worker exposure. No 

current construction is occurring at AOI 2. Additionally, off-facility residents may potentially be 

exposed to PFOA, PFOS, and PFBS via inhalation of dust caused by on-facility ground disturbing 

activities, although this exposure is likely insignificant. The CSM for AOI 2 is presented on Figure 

7-2.

7.1.3 AOI 3

A structure was burned in the northwest portion of the Cantonment Area near the current Dining 

Facility (Building 410). The structure was burned sometime between 1995 and 2002. No 

information was available on the concentration or amount of AFFF used during the event. In 

addition, the 1049th trained with foam near the former location of Building 410 (Planned Fire 

Structure). Specific details regarding the frequency, volume, chemical composition, and 

concentration of any potential AFFF used at the FTA are not known. During the SI, PFAS were 

detected in soil in this area; however, concentrations were below SLs. Based on the results of the 

SI in AOI 3, ground-disturbing activities could potentially result in site worker, construction worker, 

trespasser, resident, and recreational user exposure to PFOA, PFOS, and PFBS via inhalation of 

dust. Ground-disturbing activities could potentially result in site worker, construction worker, 

trespasser, and recreational user exposure to PFOA, PFOS, and PFBS via ingestion of surface 

soil. Additionally, ground-disturbing activities to subsurface soil could potentially result in 

construction worker exposure. No current construction is occurring at AOI 3. The CSM for AOI 3 

is presented on Figure 7-3.

7.2 Groundwater Exposure Pathway

The SI results for PFOA, PFOS, and PFBS in groundwater were used to determine whether a 

potentially complete pathway exists between the source and potential receptors at each AOI 

based on the aforementioned criteria.
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 7-3

7.2.1 AOI 1

PFOA, PFOS, and PFBS were detected in groundwater from permanent monitoring wells at AOI 

1 and exceeded the SL for PFOS atAOI1-MW3, which is located near the facility boundary. Private 

residential drinking water well sampling downgradient of AOI 1 was performed in 2019, and PFOA, 

PFOS, and PFBS were detected in groundwater, but were below SLs. Therefore, the ingestion 

exposure pathway for groundwater is considered potentially complete for offsite residents. The 

facility is on city water, which has been tested and confirmed to be PFAS-free (see Section 2.2.2); 

therefore, the ingestion pathway is incomplete for site workers. Further, due to the depth of 

groundwater, the ingestion pathway for construction workers, off-facility recreational users, and 

trespassers is also considered incomplete. The CSM for AOI 1 is presented on Figure 7-1.

7.2.2 AOI 2

PFOA, PFOS, and PFBS were detected in groundwater from permanent monitoring wells at AOI 

2 and exceeded the SL for PFOS at AOI2-MW1, which is located near the facility boundary. Private 

residential drinking water well sampling downgradient of AOI 1 was performed in 2019, and PFOA, 

PFOS, and PFBS were detected in groundwater, but were below SLs. Therefore, the ingestion 

exposure pathway for groundwater is considered potentially complete for offsite residents. The 

facility is on city water, which has been tested and confirmed to be PFAS-free (see Section 2.2.2); 

therefore, the ingestion pathway is incomplete for site workers. Further, due to the depth of 

groundwater, the ingestion pathway for construction workers, off-facility recreational users, and 

trespassers is also considered incomplete. The CSM for AOI 2 is presented on Figure 7-2.

7.2.3 AOI 3

PFOA, PFOS, and/ or PFBS were detected in groundwater, but did not exceed SLs at AOI 3. 

PFOA, PFOS, and PFBS were detected in groundwater from permanent monitoring wells at AOI 

3 at concentrations below the SLs. Therefore, the ingestion exposure pathway for groundwater is 

considered potentially complete for offsite residents. The facility is on city water, which has been 

tested and confirmed to be PFAS-free (see Section 2.2.2); therefore, the ingestion pathway is 

incomplete for site workers. Further, due to the depth of groundwater, the ingestion pathway for 

construction workers, off-facility recreational users, and trespassers is also considered 

incomplete. The CSM for AOI 3 is presented on Figure 7-3.
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 7-4

THIS PAGE INTENTIONALLY BLANK
Media

SOURCE PATHWAY R

AOI 1

Fire Training 

Activities, Fire 

Truck Washing, 

Prairie Dog 

Relocation

PFAS in Soil

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOI

Surface 

Water/ 

Sediment

Shallow 

Groundwater

Subsurface 

Soil

Source Release Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Hu

C

Flow-Chart ContinuesPartial / Possible FlowFlow-Chart StopsIncomplete PathwayPotentially Complete PathwayComplete Pathway

Site 

Worker

Con

W

Site 

Worker

Con

W

LEGEND

Figure 

Conceptual S

AOI 1 Mt. Defensa Ave

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Ingestion

/ 

/

Notes:1. The resident and recreational user receptors referto an off-site resident and recreational user.2. Dermal contact exposure pathway is incompletefor PFAS.

/ 

/ 

/ 
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 7-6

THIS PAGE INTENTIONALLY BLANK
Media

SOURCE PATHWAY R

AOI 2

Fire Training 

Activities, 

Structural Fires, 

Fire Truck 

Washing

PFAS in Soil

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOI

Surface 

Water/ 

Sediment

Shallow 

Groundwater

Subsurface 

Soil

Source Release Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Hu

C

Flow-Chart ContinuesPartial / Possible FlowFlow-Chart StopsIncomplete PathwayPotentially Complete PathwayComplete Pathway

Site 

Worker

Con

W

Site 

Worker

Con

W

LEGEND

Figure 

Conceptual S

AOI 2 Cantonment 

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Ingestion

/ 

/

Notes:1. The resident and recreational user receptors referto an off-site resident and recreational user.2. Dermal contact exposure pathway is incompletefor PFAS.

/ 

/ 

/ 
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 7-8

THIS PAGE INTENTIONALLY BLANK
Media

SOURCE PATHWAY RECEPTOR

AOI 3

Fire Training

Activities,

Structural Fires,

Burial Trench

PFAS in Soil

Human

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne Soil

Particulate

Surface Soil

at AOI

Surface

Water/

Sediment

Shallow

Groundwater

Subsurface

Soil

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

Dust

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Complete Pathway

Site

Worker

Construction

Worker Resident Trespasser/Recreational User

Site

Worker

Construction

Worker Resident Trespasser/

Recreational User

LEGEND

/

Figure 7-3

Conceptual Site Model

AOI 3 Cantonment Area Northwest

Potential

Off-Facility

Source Not

under

Control of

ARNG

/

Ingestion

/ / /

/

Notes:

1. The resident and recreational user receptors refer

to an off-site resident and recreational user.

2. Dermal contact exposure pathway is incomplete

for PFAS.

/ /

/ / /

/ / /

/

/ / / /

/

7-9
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Fort William Henry Harrison, MT

AECOM 7-10

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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 the report. 

The outcome provides general and comparative interpretations of the findings relative to the SLs. 

8.1 SI Activities

SI field activities were conducted in two mobilizations. The first mobilization included permanent 

groundwater monitoring well installation, development, and sampling; surface and subsurface soil 

sampling; and groundwater sampling from existing wells from 10 to 20 February 2019 and from 

19 to 31 May 2019. The second mobilization included permanent groundwater monitoring well 

installation, development, and sampling; surface and subsurface soil sampling; and groundwater 

sampling from existing wells from 5 to 15 October 2020. Field activities were conducted in 

accordance with the SI QAPP Addendum (AECOM, 2019). 

To fulfill the project DQOs set forth in the approved SI QAPP Addendum (AECOM, 2019), samples 

were collected and analyzed for a subset of PFAS via LC/MS/MS compliant with DoD QSM 5.1 

Table B-15 as follows. The 18 PFAS analyzed as part of the ARNG SI program are specified in 

Section 5.8 of this Report.

Mobilization 1 – 

• 47 soil grab samples from 27 boring locations; and

• 15 groundwater samples, six from new monitoring well locations, eight from existing

monitoring well locations, and one from an irrigation well location.

Mobilization 2 – 

• 30 soil grab samples from 27 boring locations; and

• 15 groundwater samples, five from new monitoring well locations and ten from existing

monitoring well locations.

This information gathered during this investigation was used to determine the PFOA, PFOS, and 

PFBS at or above SLs, as well as the presence or absence of an additional 15 PFAS at the facility.

Additionally, the CSMs were refined to assess whether a complete pathway exists between the 

source and receptors for potential exposure to PFOA, PFOS, and PFBS at the AOIs, which are 

described in Section 7. 

8.2 SI Goals Evaluation

As described in Section 4.2, the SI activities were designed to achieve six main goals or DQOs. 

This section describes the SI goals and the conclusions that can be made for each based on the 

data collected during this investigation. 

1) Determine the presence or absence of PFOA, PFOS, and PFBS at or above SLs, as well

as the presence or absence of an additional 15 PFAS at the Site

PFOA, PFOS, and PFBS were detected at FTWHH in both soil and groundwater. PFOA,

PFOS, and PFBS were detected both at the source areas as well as at the facility

boundary between source areas and potential drinking water receptors. PFOS in

groundwater at AOI 1 and AOI 2 exceeded the SL of 40 ng/L. Detections of PFOA and

PFBS in groundwater were below the SLs. Additionally, the detected concentrations of

PFOA, PFOS, and PFBS in soil samples from all AOIs were below the SLs.
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Fort William Henry Harrison, MT

AECOM 8-2

2) Develop information to potentially eliminate a release from further consideration because

it is determined that it poses no significant threat to human health or the environment.

Five potential PFAS release areas were removed from further consideration based on the 

data collected during this SI: Prairie Dog Relocation (AOI 1), 1049th Engineer Detachment 

Building M1 (AOI 2), Burial Trench (AOI 2), Planned Structure Fire (AOI 3), and 1049th 

Firefighting Training Area 2 (AOI 3). PFOA, PFOS, and PFBS results were below the SLs 

in soil and groundwater; therefore, these areas pose no significant threat to human health 

or the environment.

3) Determine the potential need for a removal action. 

As described in Section 2.4, in 2019, offsite residential drinking water samples were 

collected due to the exceedance of SLs observed in groundwater during the FTWHH SI. 

Five properties were selected to be sampled due to their proximity to FTWHH. PFOA, 

PFOS, and/or PFBS were detected in all five of the drinking water samples collected but

were below SLs. Additionally, groundwater samples collected adjacent to the main gate at

the MacDonald Property during Mobilization 2 were also below SLs. A removal action is 

not needed at this time because the drinking water sample results were below the SLs.

4) Collect data to better characterize the release areas for more effective and rapid initiation 

of a RI.

The geological data collected as part of the SI is consistent with the descriptions of the 

Quaternary aged alluvium for the area. The alluvium is described as a gray to brown, 

moderately sorted, pebble to cobble gravel with fine- to coarse-grained sand matrix. 

Boring logs from AOI 1, AOI 2, and AOI 3 are presented in Appendix E. Well borings in 

AOI 1 along the southern facility boundary are aligned from west to east and likely parallel

the depositional direction. Most of the samples were similar in that they contained varying 

percentages of gravel ranging from 5 to 50% in a sand matrix. The sand matrix size and 

size range also varied from fine to coarse. 

Typically, the gravels observed from ground surface to 5 feet bgs ranged from 0.5 inches 

to 1 inch in diameter and from 5 to 20 feet bgs the diameter increased to from 0.5 to 4 

inches. Between 20 and 30 feet bgs the gravel ranged from 3.5 to >5 inches in diameter 

and generally the shape of the gravels became more rounded towards the east. At a depth 

of 50 feet bgs, a white silt/clay layer was encountered in the boring for AOI-MW1. The 

origin of this distinctive white layer is unknown, but it could possibly be the interface 

between the younger alluvium (weathered volcanic ash) and the older lakebed sediments.

The same white layer was also observed in the boring for AOI3-MW1, and AOI03-MW02. 

The borings in AOI 2 were generally shallower than in the other two areas because the 

water table was encountered at a shallower depth at AOI 2. However, a similar pattern of 

better rounding of gravels in the eastern most boring for AOI 2 was observed. 

Depth to water at the facility ranges from approximately 14 to 43 feet bgs. The horizontal 

gradient in the northern portion of the facility between OBTMW-01 and AOI2-MW1 is 0.013

feet per feet. The horizontal gradient in the southern portion of the facility between AOI1-

MW1 and AOI1-MW3 is 0.020 feet per feet.

5) Identify within 4 miles of the installation other potential PFAS sources (fire stations, major 

manufacturers, other DoD facilities) and receptors, including both groundwater and 

surface water receptors, to determine whether the ARNG is the likely source of PFAS, or 

whether there is an offsite source of PFAS responsible for installation detections of PFAS 

(USEPA, 2005).

Based upon the evaluation of groundwater and soil results in comparison to SLs, in 

combination with the groundwater flow direction analysis, the source of PFAS

contamination is likely attributable to ARNG activities.
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Fort William Henry Harrison, MT

AECOM 8-3

6) Determine whether a complete pathway exists between the source and potential 

receptors and whether ARNG is the likely source of the contamination. 

PFOA, PFOS, and PFBS were detected in soil and groundwater at source areas and the

facility boundary indicate a potentially complete pathway between source and receptor.

However, as described in Section 2.4, offsite residential drinking water samples were 

collected due to the exceedance of SLs observed in groundwater during the FTWHH SI. 

Five properties were selected to be sampled due to their proximity to FTWHH. PFOA, 

PFOS, and PFBS were detected in all five of the drinking water samples collected but

were below SLs. Additional offsite residential drinking water sampling is recommended 

due to the SL groundwater exceedance of PFOS at AOI 1 and AOI 2.

8.3 Outcome 

The CSMs were revised based on the SI findings. There is potential for exposure to offsite

residential drinking water receptors from historical firefighting training activities completed with 

AFFF at FTWHH. Offsite drinking water sampling was performed at several residences 

downgradient of AOI 1 and east of the FTWHH property boundary. PFOA, PFOS, and/or PFBS

were detected in the drinking water samples but the concentrations did not exceed SLs. Drinking 

water samples were not collected downgradient of AOI 2. Due to historical firefighting training 

activities completed with AFFF, there is a potential for exposure to offsite residential drinking water 

receptors east of the FTWHH property boundary.

Sample chemical analytical concentrations collected during the SI were compared against the 

project SLs for PFOA, PFOS, and PFBS in soil and groundwater, as described in Table 6-1. The 

following bullets summarize the SI results: 

• PFOA, PFOS, and PFBS were detected in soil at AOI 1, AOI 2, and AOI 3; however, results 

did not exceed SLs.

• PFOA, PFOS, and PFBS were detected in groundwater at AOI 1, AOI 2, and AOI 3. PFOS 

exceeded SLs at AOI 1 and AOI 2; however, no other results exceeded SLs at AOI 3.

Table 8-1 summarizes the SI results for soil and groundwater. Based on the CSMs developed 

and revised in light of the SI findings, there is potential for exposure to residential drinking water 

receptors caused by DoD activities at or adjacent to the facility. 

Table 8-2 summarizes the rationale used to determine if an AOI should be considered for further 

investigation under CERCLA and undergo an RI. Based on the results of this SI, further evaluation 

is warranted in the RI for AOI 1 and AOI 2.
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Fort William Henry Harrison, MT

AECOM 8-4

Table 8-1: Summary of Site Inspection Findings

AOI Potential PFAS Release Area Soil – Source 

Area

Groundwater

– Source Area

Groundwater –

Facility Boundary

1 Mt. Defensa Avenue Drainage Ditch

1 1049th Engineer Detachment Building 

1010 NA

1 Prairie Dog Relocation (three locations) NA NA

1 1049th Firefighting Training Area 1 NA

1 1049th Firefighting Training Area 3 NA NA

1 MacDonald Property NA

2 Former Weasel Barn

2 Excavated Soil from Mt. Defensa Ave 

Drainage Ditch

2 1049th Engineer Detachment Building 

M1

2 1049th Firefighting Training Area 4 NA

3 Planned Structure Fire NA

3 Burial Trench NA NA

3 1049th Firefighting Training Area 2 NA

Legend:

NA = Not applicable

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

Fort William Henry Harrison, MT

AECOM 8-5

Table 8-2: Site Inspection Recommendations

AOI Description Rationale Future Action

1

Mt. Defensa Avenue 

Drainage Ditch, 1049th

Engineer Detachment 

Building 1010, 1049th

Firefighting Training Area 

1, 1049th Firefighting 

Training Area 3

No exceedances of SL in groundwater 

at the source area; however, 

exceedances of SLs in groundwater at 

the facility boundary. No exceedances 

of SLs in soil.

Proceed to RI

1 Prairie Dog Relocation 

(Three Release Areas) No exceedances of SLs in soil. No further action

2

Former Weasel Barn, 

Excavated Soil from Mt. 

Defensa Ave Drainage 

Ditch, 1049th Firefighting 

Training Area 4

No exceedances of SL in groundwater 

at the source area; however, 

exceedances of SLs in groundwater at 

the facility boundary. No exceedances 

of SLs in soil.

Proceed to RI

2 1049th Engineer 

Detachment Building M1

No exceedances of SLs in 

groundwater or soil. No further action

3

Planned Structure Fire, 

Burial Trench, and 1049th

Firefighting Training Area 

2

No exceedances of SLs in 

groundwater or soil. No further action
Site Inspection Report

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AECOM 8-6

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Fort William Henry Harrison, MT

AECOM 9-1

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