FINAL

Site Inspection Report 

Camp Ripley

Little Falls, Minnesota

Site Inspection for Perfluorooctanoic acid (PFOA), 

Perfluorooctanesulfonic acid (PFOS), Perfluorohexanesulfonic 

acid (PFHxS), Perfluorononanoic acid (PFNA), 

Hexafluoropropylene oxide dimer acid (HFPO-DA), and 

Perfluorobutanesulfonic acid (PFBS) at ARNG Installations, 

Nationwide

September 2023

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED
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Camp Ripley, Little Falls, Minnesota

AECOM i

Table of Contents

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

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

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

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

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

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

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

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

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

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

2.2.4 Climate........................................................................................................2-5

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

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

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

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

3.1 AOI 1 TriMaxTM Discharge Area and Building 8-197 ..............................................3-1

3.2 AOI 2 Burn Pit Fire Training Area ..........................................................................3-1

3.3 AOI 3 DHS Demonstration ....................................................................................3-1

3.4 AOI 4 USFPO Warehouse, CMA Shop, and CMA Discharge Area ........................3-1

3.5 AOI 5 Wastewater Treatment Plant and Sludge Spread Site .................................3-2

3.6 AOI 6 Stormwater Infiltration Basin........................................................................3-2

3.7 AOI 7 Buildings 2-166, 2-203, 2-223, and 2-272....................................................3-2

3.7.1 Building 2-166 .............................................................................................3-2

3.7.2 Building 2-203 .............................................................................................3-3

3.7.3 Building 2-223 .............................................................................................3-3

3.7.4 Building 2-272 .............................................................................................3-3

3.8 AOI 8 Building 8-195 .............................................................................................3-3

3.9 Adjacent Sources ..................................................................................................3-3

3.9.1 Coal Train Collision .....................................................................................3-3

3.9.2 Fuel Tanker Accident...................................................................................3-4

3.9.3 Central Minnesota Ethanol Cooperative Fire...............................................3-4

3.9.4 Keystone Automotive ..................................................................................3-4

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

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

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

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

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

4.5 Data Usability Assessment....................................................................................4-1

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

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

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

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

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

5.2 Soil Borings and Soil Sampling .............................................................................5-2
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5.3 Temporary Well Installation and Groundwater Grab Sampling...............................5-4

5.4 Existing Permanent Well Groundwater Sampling ..................................................5-4

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

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

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

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

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

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

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

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

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

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

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

6.3.3 AOI 1 Conclusions ......................................................................................6-3

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

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

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

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

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

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

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

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

6.6 AOI 4.....................................................................................................................6-5

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

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

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

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

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

6.7.2 AOI 5-WWTP and Existing Facility Wells Groundwater Analytical Results...6-6

6.7.3 AOI 5-WWTP Conclusions ..........................................................................6-7

6.8 AOI 5-Sludge Spread Site .....................................................................................6-7

6.8.1 AOI 5-Sludge Spread Site Soil Analytical Results........................................6-7

6.8.2 AOI 5-Sludge Spread Site Groundwater Analytical Results .........................6-7

6.8.3 AOI 5-Sludge Spread Site Conclusions.......................................................6-8

6.9 AOI 6.....................................................................................................................6-8

6.9.1 AOI 6 Soil Analytical Results .......................................................................6-8

6.9.2 AOI 6 Groundwater Analytical Results.........................................................6-8

6.9.3 AOI 6 Conclusions ......................................................................................6-8

6.10AOI 7.....................................................................................................................6-8

6.10.1AOI 7 Soil Analytical Results .......................................................................6-9

6.10.2AOI 7 Groundwater Analytical Results.........................................................6-9

6.10.3AOI 7 Conclusions ......................................................................................6-9

6.11 AOI 8.....................................................................................................................6-9

6.11.1AOI 8 Soil Analytical Results .......................................................................6-9

6.11.2AOI 8 Groundwater Analytical Results....................................................... 6-10

6.11.3AOI 8 Conclusions .................................................................................... 6-10
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7. Exposure Pathways......................................................................................................7-1

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

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

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

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

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

7.1.5 AOI 5-WWTP ..............................................................................................7-3

7.1.6 AOI 5-Sludge Spread Site ...........................................................................7-3

7.1.7 AOI 6...........................................................................................................7-3

7.1.8 AOI 7...........................................................................................................7-4

7.1.9 AOI 8...........................................................................................................7-4

7.2 Groundwater Exposure Pathway...........................................................................7-4

7.2.1 AOI 1...........................................................................................................7-4

7.2.2 AOI 2...........................................................................................................7-5

7.2.3 AOI 3...........................................................................................................7-5

7.2.4 AOI 4...........................................................................................................7-5

7.2.5 AOI 5-WWTP ..............................................................................................7-5

7.2.6 AOI 5-Sludge Spread Site ...........................................................................7-6

7.2.7 AOI 6...........................................................................................................7-6

7.2.8 AOI 7...........................................................................................................7-6

7.2.9 AOI 8...........................................................................................................7-6

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

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

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

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

7.3.4 AOI 4...........................................................................................................7-8

7.3.5 AOI 5 – WWTP............................................................................................7-8

7.3.6 AOI 5 – Sludge Spread Site ........................................................................7-8

7.3.7 AOI 6...........................................................................................................7-9

7.3.8 AOI 7...........................................................................................................7-9

7.3.9 AOI 8...........................................................................................................7-9

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

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

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

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

Appendix A Data Usability Assessment and Validation Reports

Appendix B Field Documentation

B1. Log of Daily Notice of Field Activities

B2. Sampling Forms

B3. Field Change Request Forms

B4. Survey Data

B5. Investigation-Derived Waste Polygons

Appendix C Photographic Log

Appendix D TPP Meeting Minutes

Appendix E Boring Logs

Appendix F Analytical Results

Appendix G Laboratory Reports

Figures

Figure 2-1 Facility Location

Figure 2-2 Facility Topography

Figure 2-3 Groundwater Features

Figure 2-4 Groundwater Elevations, June 2022

Figure 2-5 Surface Water Features

Figure 2-6 Stormwater Drainage Network

Figure 2-7 Drinking Water Results

Figure 3-1 Areas of Interest

Figure 5-1 Site Inspection Sample Locations

Figure 6-1 PFOA Soil Results for AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, AND AOI 8

Figure 6-2 PFOA Soil Results for AOI 4, AOI 5, AND AOI 7

Figure 6-3 PFOS Soil Results for AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, AND AOI 8

Figure 6-4 PFOS Soil Results for AOI 4, AOI 5, and AOI 7

Figure 6-5 PFBS Soil Results for AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, AND AOI 8

Figure 6-6 PFBS Soil Results for AOI 4, AOI 5, and AOI 7

Figure 6-7 PFHxS Soil Results for AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, AND AOI 8

Figure 6-8 PFHxS Soil Results for AOI 4, AOI 5, and AOI 7

Figure 6-9 PFNA Soil Results for AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, AND AOI 8

Figure 6-10 Soil Results for AOI 4, AOI 5, AND AOI 7

Figure 6-11 PFOA, PFOS, and PFBS Detections in Groundwater for AOI 1, AOI 2, AOI 3, AOI 

5, AOI 6, and AOI 8

Figure 6-12 PFOA, PFOS, and PFBS Detections in Groundwater for AOI 4, AOI 5, and AOI 7

Figure 6-13 PFHxS and PFNA Detections in Groundwater

Figure 7-1 Conceptual Site Model, AOI 1

Figure 7-2 Conceptual Site Model, AOI 2

Figure 7-3 Conceptual Site Model, AOI 3

Figure 7-4 Conceptual Site Model, AOI 4

Figure 7-5 Conceptual Site Model, AOI 5 WWTP

Figure 7-6 Conceptual Site Model, AOI 5 Sludge Spread Site

Figure 7-7 Conceptual Site Model, AOI 6 

Figure 7-8 Conceptual Site Model, AOI 7 

Figure 7-9 Conceptual Site Model, AOI 8
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Camp Ripley, Little Falls, Minnesota

AECOM v

Tables

Table ES-1 Screening Levels (Soil and Groundwater)

Table ES-2 Summary of Site Inspection Findings and Recommendations

Table 2-1 Drinking Water Supply Wells near Camp Ripley Cantonment

Table 2-2 Residential Drinking Water Results

Table 5-1 Site Inspection Samples by Medium

Table 5-2 Soil Boring Depths, Temporary Well Screen Intervals, and Groundwater 

Elevations

Table 5-3 Permanent Monitoring Well Groundwater Elevations

Table 6-1 Screening Levels (Soil and Groundwater)

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

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

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

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

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

% percent

°C degrees Celsius

°F degrees Fahrenheit

μg/kg micrograms per kilogram

AASF Army Aviation Support Facility

ACUB Army Compatible Use Buffer

AECOM AECOM Technical Services, Inc.

AFFF aqueous film-forming foam

amsl above mean sea level

AOI Area of Interest

AR-AFFF alcohol-resistant AFFF

ARNG Army National Guard

BAL Bruce A. Liesch Associates, Inc.

bgs below ground surface 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CMA Combined Maintenance Area

CoC chain of custody

CSM conceptual site model

CSMS Combined Support Maintenance Shop

DA Department of the Army

DHS Department of Homeland Security

DoD Department of Defense

DO dissolved oxygen

DPT direct push technology

DQO data quality objective

DUA data usability assessment

EDRTM Environmental Data Resources, Inc.TM

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

EMTC Emergency Management Training Center

FedEx Federal Express

FTA Fire Training Area

ft/day feet per day

GPS Global positioning system

GPRS Ground Penetrating Radar Systems

HDPE high-density polyethylene 

HFPO-DA hexafluoropropylene oxide dimer acid

IDW investigation-derived waste

ITRC Interstate Technology Regulatory Council

LC/MS/MS liquid chromatography with tandem mass spectrometry

MIL-SPEC military specification

MNARNG Minnesota Army National Guard

n.d. no date
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NELAP National Environmental Laboratory Accreditation Program

ng/L nanograms per liter

ORP oxidation-reduction potential

OSD Office of the Secretary of Defense

PA Preliminary Assessment

PCE Progressive Consulting Engineers

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PID photoionization detector

PQAPP Programmatic UFP-QAPP

PVC polyvinyl chloride

QA quality assurance 

QAPP Quality Assurance Project Plan

QC quality control

QSM Quality Systems Manual

RI Remedial Investigation

SI Site Inspection

SL screening level

SOP standard operating procedure

TOC total organic carbon

TPP Technical Project Planning

UFP Uniform Federal Policy

UMD University of Minnesota Duluth

US United States

USACE United States Army Corps of Engineers

USAEHA United States Army Environmental Hygiene Agency

USAF United States Air Force

USASCHPPM United States Army Center for Health Promotion and Preventative Medicine

USCS Unified Soil Classification System

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

USPFO United States Property and Fiscal Office

WWTP wastewater treatment plant
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AECOM ES-1

Executive Summary

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

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

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

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

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

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

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

, and perfluorobutanesulfonic acid 

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

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

The PA identified six Areas of Interest (AOIs) with seven potential release areas where PFAScontaining materials may have been used, disposed, or released historically. However, since the 

Final PA Report was issued, ARNG adopted a more conservative policy to investigate aqueous 

film-forming foam storage and use areas where no previous releases were reported; thus, seven

additional potential release areas (constituting expansion of AOI 1 and AOI 4, as well as adding 

two additional AOIs (see Table ES-2 for AOI locations). The objective of the SI is to identify 

whether there has been a release to the environment from the identified AOIs and determine 

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

threats, or no further action is required based on SLs for relevant compounds. This SI was 

completed at Camp Ripley in Little Falls, Minnesota under the Comprehensive Environmental 

Response, Compensation, and Liability Act (CERCLA). Further evaluation at Camp Ripley is 

warranted for AOI 1, AOI 2, AOI 4, AOI 5-Wastewater Treatment Plant (WWTP), AOI 6, AOI 7, and 

AOI 8; no further evaluation is warranted for AOI 3 and AOI 5-Sludge Spread Site at this time. 

Camp Ripley will also be referred to as the “facility” throughout this document. 

Camp Ripley is in Morrison County in central Minnesota, near the City of Little Falls. The State of 

Minnesota purchased 12,000 acres of land from the Northwestern Improvement Company in 

1931, formally establishing Camp Ripley. Since 1951, the State of Minnesota has purchased 

additional land that has expanded Camp Ripley to a total of 53,000 acres. Camp Ripley is currently 

a maneuver and training center owned by the State of Minnesota and managed by the Minnesota 

Department of Military Affairs. In addition, the Department of Natural Resources provides 

technical support to the facility (AECOM Technical Services, Inc., 2022a). 

The PA identified six AOIs for investigation during the SI phase; however, two additional AOIs 

were added after the Final PA was issued. SI sampling results from the eight AOIs were compared 

to OSD SLs. Table ES-2 summarizes the SI results for each AOI. Based on the results of this SI, 

further evaluation under CERCLA is warranted in a Remedial Investigation (RI) for AOI 1, AOI 2, 

AOI 4, AOI 5-WWTP, AOI 6, AOI 7, and AOI 8; no further evaluation is warranted for AOI 3 or AOI 

5-Sludge Spread Site at this time.

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

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

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

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

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

individual chemical of concern in the absence of other PFAS
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AECOM ES-2

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

Analyteb

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ Commercial 

Composite Worker

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater)

(ng/L)a

PFOA 19 250 6

PFOS 13 160 4 

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

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

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

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

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

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

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

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

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

AOI Potential 

Release Area

Soil –

Source 

Area

Groundwater – 

Source Area Future Action

1

TriMaxTM Discharge 

Area and Building 8-

197

Proceed to RI 

2 Burn Pit Fire Training 

Area Proceed to RI

3 DHS Demonstration No Further 

Action

4 

USPFO Warehouse, 

CMA Shop, and CMA 

Discharge Area

Proceed to RI

5 

WWTP Proceed to RI

Sludge Spread Site No Further 

Action

6 Stormwater Infiltration 

Basin Proceed to RI

7 Buildings 2-166, 2-

203, 2-223, and 2-272 Proceed to RI

8 Building 8-195 Proceed to RI

Legend:

CMA = Combined Maintenance Activity

DHS = Department of Homeland Security

FTA = fire training area

RI = Remedial Investigation

USPFO = United States Property and Fiscal Office

WWTP = wastewater treatment plant

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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AECOM 1-1

1. Introduction

1.1 Project Authorization

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

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

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

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

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

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

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

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

, and perfluorobutanesulfonic 

acid (PFBS) at ARNG facilities nationwide. The ARNG performed this SI at Camp Ripley in Little 

Falls, Minnesota. Camp Ripley is also referred to as the “facility” throughout this document. 

The SI project elements were performed in compliance with Comprehensive Environmental 

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

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

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

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

investigations. 

1.2 SI Purpose

A PA was performed at Camp Ripley (AECOM Technical Services, Inc. [AECOM], 2019) that

identified seven potential release areas grouped into six Areas of Interest (AOIs) where PFAScontaining materials may have been used, disposed, or released historically. However, since the 

Final PA Report was issued, ARNG adopted a more conservative policy to investigate AFFF

storage and use areas where no previous releases were reported; thus, seven additional potential 

release areas warranted expansion of AOI 1 and AOI 4 as well as creating two additional AOIs. 

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

the eight AOIs and determine whether further investigation is warranted, a removal action is 

required to address immediate threats, or no further action is required based on screening levels 

(SLs) for the relevant compounds. 

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

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

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

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

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

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

2.1 Facility Location and Description

Camp Ripley is in Morrison County in central Minnesota, near the City of Little Falls, and 

approximately 20 miles southwest of Brainerd (Figure 2-1). The State of Minnesota purchased 

12,000 acres of land from the Northwestern Improvement Company in 1931, formally establishing 

Camp Ripley. Since 1951, the State of Minnesota has purchased additional land that has 

expanded Camp Ripley to a total of 53,000 acres. The facility is bordered by the Crow Wing River 

to the north and the Mississippi River to the east.

Camp Ripley is currently a maneuver and training center owned by the State of Minnesota and 

managed by the Minnesota Department of Military Affairs. In addition, the Department of Natural 

Resources provides technical support to the facility. The missions of Camp Ripley are to provide 

realistic joint and combined arms training, provide support for state emergencies, and provide 

resources that add value to the community. A cantonment area is located in the southeast part of 

the facility, which contains barracks and two full-time occupied residences: the Post Commander’s 

house and the Command Sergeant Major’s house. 

2.2 Facility Environmental Setting

Camp Ripley is on the western Lake Section of the Central Lowland physiographic province

(Figure 2-2). The level to slightly rolling topography of Camp Ripley is a result of glacial drift 

during the Pleistocene Epoch (US Army Environmental Hygiene Agency [USAEHA], 1994). 

Ground-surface elevations range from 1,140 to 1,550 feet above mean sea level. Regionally, 

topography slopes to the east-southeast, toward the Mississippi River, where the elevations at 

Camp Ripley are lowest. The most prominent geomorphologic feature at Camp Ripley is the St. 

Croix moraine. This moraine occupies most of the facility, forming a rough belt of uneven 

hummocky topography containing numerous hills, associated depressions, lakes, and wetlands 

(University of Minnesota Duluth [UMD], no date [n.d.]). These higher-relief landforms cover about 

half of Camp Ripley; lower-relief landforms, such as outwash plain, old lakebeds, and alluvium, 

cover about 40 percent (%). The remaining areas consist of level terrain and water features 

(USAEHA, 1994). 

2.2.1 Geology

Surficial deposits at Camp Ripley consist of ice-contact and outwash deposits of the St. Croix 

moraine system (Figure 2-3). The outwash deposits were created by glacial meltwaters that 

flowed through the Mississippi [River] and Crow Wing River valleys, depositing the poorly sorted 

sands and gravels in a band a few miles wide along both sides of the rivers (US Army Center for 

Health Promotion and Preventative Medicine [USACHPPM], 2000). The moraine is composed 

primarily of a heterogeneous mixture of glacial sediment consisting predominantly of sandy 

deposits laid down as flow tills, outwash, and lacustrine sediment by the Rainy and Superior lobes 

during the St. Croix glaciation of the Late Wisconsin Period. These deposits overlie the Hewitt till, 

a loamy glacial deposit laid down by the Wadena lobe during an earlier glacial advance (UMD, 

n.d.). Thicknesses of these unconsolidated deposits vary considerably across Camp Ripley,

ranging from 20 feet to more than 200 feet (USACHPPM, 2000).

Bedrock at Camp Ripley consists of Precambrian age metamorphic rocks (USAEHA, 1994). Slate, 

schist, and metamorphosed mafic and intermediate volcanics compose the bedrock under Camp 

Ripley. Depth to bedrock at Camp Ripley varies and can be 150 feet or greater (USACHPPM, 

2000).
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AECOM 2-2

During the SI, medium to high-permeability sands were observed as the dominant lithology of the 

unconsolidated sediments below Camp Ripley. The borings were completed at depths between 

9 and 25 feet below ground surface (bgs). A majority of borings contained poorly graded sand, 

with frequent layers of well-graded sand. Occasional silt layers were observed in thicknesses 

ranging from 0.75 to 6 feet in thickness. Varying quantities of gravel were noted in several borings

and ranged from 0.1 to 4 feet thick. Many of the logs also reported varying percentages (ranging 

from <5% to 45%) of gravel included in the sand packages. A sample for grain size analysis was 

collected at one location, AOI05-02, and analyzed via American Society for Testing and Materials 

(ASTM) Method D-422. The results indicate that the soil sample was comprised of gravel (2.96%), 

coarse-grained sand (3.69%), fine- to medium-grained sand (61.24%), silt (22.91%), and clay 

(9.19%). These results and facility observations are consistent with the understood regional 

depositional history, which is characterized by glacial moraine and outwash facies. Boring logs 

are presented in Appendix E, and grain size results are presented in Appendix F. 

2.2.2 Hydrogeology

In the region surrounding Camp Ripley, the main water-bearing units are composed of 

heterogeneous glacial sediments and lacustrine sandy deposits (Progressive Consulting 

Engineers, [PCE] n.d.; Quinn, 2006). Occasional sand and gravel components are intercepted at 

some well locations (Bruce A. Liesch Associates, Inc [BAL], 1987). Clay layers have been 

encountered throughout Camp Ripley, but no laterally extensive confining layers exist within the 

unconsolidated deposits (PCE, n.d.).

As reported in the Groundwater Atlas of Morrison County, Minnesota, the water table elevation 

across the facility generally follows topography and ranges from approximately 1,125 to 1,500 

feet; a water table is defined as the surface at which water pressure is equal to atmospheric

pressure (Baratta, 2019). The highest-elevation landforms on the facility are found in training 

areas to the northwest of the cantonment area, while the lowest are found in the cantonment area

near the Mississippi River. The water table elevation in the cantonment area, which includes the 

AOIs, post commander’s house, and command sergeant major’s house, ranges from 

approximately 1,125 to 1,175 feet (Baratta, 2019). As such, surficial groundwater was anticipated 

at or shallower than 35 feet bgs (Foth and Van Dyke, 1997). Additionally, the potential for localized 

perched groundwater conditions was anticipated due to the presence of discontinuous lowpermeability lacustrine clay and fine-grained till deposits across the site (Quinn, 2006). 

The regional groundwater flow is east-southeast toward the Mississippi River and is defined by a 

drainage divide located several miles west of Camp Ripley (UMD, n.d.). Groundwater originating 

east of this divide, which encompasses the facility, follows the east-southeast flow path to the 

discharge boundaries of Little Elk River to the southwest and the Crow Wing and Mississippi 

Rivers to the north and east (UMD, n.d.). The complex glacial topography creates localized 

variations in the groundwater flow paths, where recharge occurs at topographic highs and 

discharge occurs in adjacent topographic lows. In some areas, the shallow groundwater is thought 

to be in communication with the many kettle lakes and wetland areas (USACHPPM, 2000).

The geologic makeup of the Camp Ripley area aquifer consists primarily of coarse-grained glacial 

and lacustrine deposits; therefore, the permeability is considered high. Groundwater studies and 

flow modeling have characterized the hydraulic conductivity of the glacial deposits at Camp Ripley 

from well pump tests and grain size analyses. Calculated hydraulic conductivities from the grain 

size analyses vary widely and range from 9.7 feet per day (ft/day) for dense clay loam till to 334 

ft/day for coarse sand and gravel deposits (Quinn, 2006). A pumping test that was performed at 

an on-facility groundwater supply well in the cantonment area exhibited very rapid recharge. The 

hydraulic conductivity of sediments near this well was calculated to be 408 ft/day (PCE, n.d.).
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 2-3

Natural recharge to the groundwater aquifer system in the Camp Ripley area is primarily through 

surface infiltration through the glacial outwash deposits east of the drainage divide (Quinn 2006). 

Groundwater level results from the Argonne National Labs 2003 groundwater flow model suggest 

that Lake Alexander may contribute to the groundwater recharge (UMD n.d.). Groundwater 

discharges primarily to the Mississippi River, creating a hydrogeologic boundary along the eastern 

side of Camp Ripley (UMD, n.d.). Secondary discharge includes pumping for irrigation and 

drinking water consumption. 

The City of Little Falls utilizes eight wells, two elevated storage tanks, and two ground storage 

tanks to supply drinking water to the residents in the area. The well field for Little Falls is located 

about 6-miles south of Camp Ripley on the opposite side of the Mississippi River (Baratta, 2019). 

There are no public wells near the facility; however, numerous private domestic wells in the 

surrounding communities lie within a 4-mile radius to the facility (Figure 2-3). Camp Ripley is 

located within several watersheds with the depth to water at the southwestern portion of the facility 

for the SI range from 0 to 30 feet bgs. 19 potable water wells and one public water supply well 

are located within the boundary of Camp Ripley (Figure 2-3). Four drinking water supply wells (H 

Well, L Well, N Well, and Well 641304) are located within the southeastern cantonment area of 

the facility in proximity to one or more AOIs (Table 2-1). Drinking water for Camp Ripley’s 

cantonment area is supplied from three wells ranging from 70 to 102 feet deep. The groundwater 

is extracted from an unconfined aquifer lying under the Camp Ripley cantonment area and 

extending to the northwest (MNARNG, 2021). 

Table 2-1: Drinking Water Supply Wells near Camp Ripley Cantonment

Well ID Total Well

Depth (feet 

bgs)

Screen Interval 

(feet bgs) 

Pumping Rate1

gpm

Use as listed in 

the MWI

H Well (permit ID # 

224577) 

70 50-70

(Records indicate 

12-foot screen, 

exact interval 

uncertain)

600-1,000 Public Supply

L Well (permit ID # 

470668)

93 73-98

(Records indicate 

12-foot screen, 

exact interval 

uncertain)

1,106 Public Supply

N Well (permit ID #

622775)

102 75-102 1,000 Public Supply

Well 641304 60 52-60 20 Public Supply

Notes:

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

gpm = gallons per minute

MWI = Minnesota Well Index

1). Construction information collected from the Minnesota Department of Health Well Index ([MWI], 2023).

Depths to water measured in June 2022 during the SI ranged from 3.04 to 24.85 feet bgs. 

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

groundwater flow direction at the facility is primarily to the east-southeast towards the Mississippi 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 2-4

River. It must be noted that one existing permanent well (AOI05-536846) is located over 1.5 miles 

away from the rest of the wells sampled during the SI. Temporary wells at the AOI 5-Sludge 

Spread Site were also excluded from contouring because: 1) two temporary wells, AOI05-01 and 

AOI05-02, were dry during the synoptic gauging on 15 June 2022, and 2) the depths to 

groundwater observed at AOI05-03 and AOI05-04 were much shallower than the rest of the 

cantonment area relative to elevation, and along with the lithology, are believed to represent a 

perched groundwater zone. Thus, AOI05-536846 and AOI05-01 through AOI05-04 were excluded 

from groundwater contouring to avoid a misrepresentation of localized groundwater flow between 

AOI 5-Sludge Spread Site and the remaining AOIs. 

2.2.3 Hydrology 

Camp Ripley has abundant surface water as a result of the glacial processes that shaped the 

landscape including small inland lakes, wetlands, and streams (Minnesota ARNG [MNARNG], 

2018) (Figure 2-5).

Camp Ripley is bordered on the north by the Crow Wing River and on the east by the Mississippi 

River. The Little Elk River flows west to southeast, approximately 4 miles south of Camp Ripley. 

Numerous wetlands and lakes exist in the range areas amid the hummocky landforms of the St. 

Croix moraine and are thought to be in communication with the groundwater. Six surface water 

bodies originate on Camp Ripley and flow off facility to the Mississippi River, the Crow Wing River, 

and the Little Elk River. All three of these rivers are used for recreational activities.

The facility boundary of Camp Ripley intersects with several watersheds, as shown on 

Figure 2-5. However, the two primary watersheds containing the cantonment area of and the 

subsequent AOIs are the City of Little Falls-Mississippi River Watershed and the Broken Bow 

Creek-Mississippi River Watershed, both of which drain to the Mississippi River. The City of Little 

Falls-Mississippi River Watershed covers 6.1 square miles within the facility boundary and 

encompasses AOIs 1, 2, 4, and the AOI 5-Sludge Spread Site. The Broken Bow Creek-Mississippi 

River Watershed covers 21.2 square miles within the facility boundary, although much of that is 

located well north of the cantonment area. The Broken Bow Creek-Mississippi River Watershed 

encompasses AOIs 3, 6, 7, and the AOI 5-WWTP.

Stormwater runoff on the cantonment area is collected in a series of infiltration basins located 

along the Mississippi River. This includes the AOI 6 Stormwater Infiltration Basin which drains 

stormwater from the northeast portion of the cantonment area. Five infiltration basins were 

installed between 2009 and 2022 and are shown on Figure 2-6. AOI boundaries are shown on 

this figure for geographic reference only and are discussed in depth in Section 3. For ease of 

discussion in this and subsequent sections, the five new basins have been labelled as Infiltration 

Basin A through E (Figure 2-6). Drainage from the northern part of the cantonment area drains to 

the northeast for collection in Infiltration Basin A. In the northeastern part of the cantonment area, 

stormwater drains to eastward to Infiltration Basin B, and may also drain to the older Stormwater 

Infiltration Basin (AOI 6). Some stormwater in the eastern section of the cantonment area drains 

east into Infiltration Basin C, while stormwater from the southwestern part of the cantonment area 

(near AOI 4) and the area south of the airfield drains east toward Infiltration Basin D. Lastly, 

stormwater drainage from the southern part of the facility (near AOI 7) drains east-southeast for 

collection in Infiltration Basin E near the WWTP. These basins were installed to reduce pointsource discharges of stormwater to the Mississippi River and were designed with capacity to 

withstand a 100-year rain event and allow stormwater to infiltrate into the subsurface. However, 

due to the permeable nature of the lithology beneath this part of the facility and known connection 

between surface water and shallow groundwater at the facility, the stormwater collected in these 

basins may eventually drain to the Mississippi River. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 2-5

2.2.4 Climate 

The climate at Camp Ripley has wide variations in temperature, ample summer rainfall, and a 

persistent winter snow cover. Spring, summer, and fall temperatures are temperate, while 

occasional Arctic outbreaks occur during the winter (MNARNG, 2018). The average temperature 

is 43.35 degrees Fahrenheit ([°F], World Climate, 2019). The mean annual precipitation at Camp 

Ripley is 26.26 inches, and the mean annual snowfall is about 44 inches, occurring almost entirely 

from November through March.

2.2.5 Current and Future Land Use

Camp Ripley is a controlled-access facility for military training supporting maneuver training; 

weapons familiarization and qualification; aviation and armor gunnery; military occupational 

specialty producing and leadership provision of a central maintenance facility; direct service 

support in all classes of supply; provision of personnel services and chaplain services; and military 

morale, welfare, and recreation activities. The MNARNG is responsible for the protection and 

management of the natural and cultural resources at Camp Ripley and may restrict public access 

to the facility when conducting military training; however, many opportunities for public access 

and use exist including cross country skiing, deer and turkey hunts, fishing, bird watching, walking, 

and camping (MNARNG, 2018). 

In 2004, the MNARNG approved the Camp Ripley Army Compatible Use Buffer (ACUB) Program 

establishing a 3-mile buffer (110,000 acres) around the facility to combat encroachment concerns, 

especially noise, and in 2015, Camp Ripley was designated as the first state sentinel landscape 

in the US to promote natural resource sustainability around the facility. In an effort to expand 

services to private landowners within the ACUB Program and extend out to a 10-mile radius 

around the facility, Camp Ripley was designated as a federal Sentinel Landscape in 2016. The 

federal designation will allow Camp Ripley to more effectively compete for federal funding from 

agencies beyond the Department of Defense (DoD) and to better align federal, state, and local 

programs that could support private landowners in a Sentinel Landscape (MNARNG, 2018).

Currently, Camp Ripley is deficient in maneuver area acreage, and improvements to existing lands 

are planned to meet current and projected training requirements. Planned improvements include 

upgrading existing roads and trails, constructing new maneuver corridors, and creating new 

assembly areas. Reasonably anticipated future land use is not expected to change from the 

current land use described above.

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

The following birds, mammals, and insects are federally endangered, threatened, proposed, and/ 

or are listed as candidate species in Morrison County, Minnesota (United States Fish and Wildlife 

Service [USFWS], 2023a). 

• Birds: Whooping crane, Grus americana (experimental population, endangered in some

other states)

• Migratory Birds: American Golden-plover, Pluvialis dominica (breeds elsewhere); Bald

Eagle, Haliaeetus leucocephalus (breeds December 1 to August 31); Black Tern, Chlidonias

niger (breeds May 15 to August 20); Black-billed Cuckoo, Coccyzus erythropthalmus

(breeds May 15 to October 10); Bobolink, Dolichonyx oryzivorus (breeds May 20 to July 31);

Canada Warbler, Cardellina canadensis (breeds May 20 to August 10); Chimney Swift,

Chaetura pelagica (breeds March 15 to August 25); Common Tern, Sterna hirundo hirundo

(breeds May 1 to August 31); Connecticut Warbler, Oporornis agilis (breeds June 15 to

August 10); Eastern Whip-poor-will, Anstrostomus vociferus (breeds May 1 to August 20);
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 2-6

Golden Eagle, Aquila chrysaetos (breeds January 1 to August 31); Golden-winged Warbler, 

Vermivora chrysoptera (breeds May 1 to July 20); Lesser Yellowlegs, Tringa flavipes

(breeds elsewhere); Marbled Godwit, Limosa fedoa (breeds May 1 to July 31); Olive-sided 

Flycatcher, Contopus cooperi (breeds May 20 to August 31); Red-headed Woodpecker, 

Melanerpes erythrocephalus (breeds May 10 to September 10); Ruddy Turnstone, Arenaria 

interpres morinella (breeds elsewhere); Rusty Blackbird, Euphagus carolinus (breeds 

elsewhere); Short-billed Dowitcher, Limnodromus griseus (breeds elsewhere); Western 

Grebe, aechmophorus occidentalis (breeds June 1 to August 31); Wood Thrush, Hylocichla 

mustelina (breeds May 10 to August 31)

• Insects: Monarch butterfly, Danaus plexippus (candidate)

• Mammals: Northern Long-eared Bat, Myotis septentrionalis (endangered); Canada Lynx,

Lynx canadensis (threatened); Gray Wolf, Canis lupis (threatened); Tricolored Bat,

Perimyotis subflavus (proposed endangered)

According to the USFWS, Camp Ripley does not have any registered critical habitats for the abovelisted species. However, the facility contains numerous wetland areas, ponds, and streams, which 

may be used by migratory birds (USFWS, 2023b).

2.3 History of PFAS Use

Fourteen potential release areas were identified and grouped into eight AOIs where AFFF may 

have been used, stored, disposed, or released historically at Camp Ripley. These potential 

releases may have occurred during familiarization training, demilitarization, fire training activities, 

as well as incidental releases, as early as the 1980s. The potential release areas were grouped 

into eight AOIs based on preliminary data and presumed groundwater flow directions. A 

description of each AOI is presented in Section 3. 

2.4 Potable Well Sampling

On 9 May 2023 through 11 May 2023, ARNG conducted drinking water sampling from off-facility 

private, potable wells due to concentrations of PFOA and PFOS near the southern facility 

boundary. One property measured PFOS concentrations of that exceed 70 ng/L. As there are no 

final federal drinking water standards available for PFAS, Army follows DoD guidance to address 

drinking water containing PFOS or PFOA (individually or combined) at or above 70 ng/L. As a 

result of the initial sampling, several properties adjacent and downgradient of the exceedance 

were selected to be resampled on 21 June 2023 (see Figure 2-7). The other properties measured 

a PFOA and PFOS below the 70 ng/L for PFOS and PFOA. The results of the drinking water 

sampling were provided in letters to the residents and are also provided in Table 2-2. 

The need for a removal action was determined from the results of the off-facility drinking water 

sampling. ARNG has prepared a Time-Critical Removal Action (TCRA) Action Memorandum (AM) 

in response to the presence of PFAS in potable wells. The TCRA AM proposed providing potable

water for affected property whose drinking water exceeds the action level of 70 ng/L for PFOS 

and/or PFOA, until a treatment system can be installed. The selected removal action has been 

finalized and is being implemented as of the date of this report (AECOM, 2021). 
Table 2-2

Residential Drinking Water Results

Site Inspection Report, Camp Ripley

Analyte USEPA HAa Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual

11Cl-PF3OUdS - - - - - < 2.01 4.01 U - - - - - - - - < 2.09 4.17 U < 2.04 4.08 U - - - -

4:2 FTS - < 3.7 7.3 U < 3.01 4.01 U < 3.8 7.5 U < 3.7 7.3 U < 3.13 4.17 U < 3.06 4.08 U < 3.5 7.0 U

6:2 FTS - < 3.7 7.3 U < 3.01 4.01 U < 3.8 7.5 U < 3.7 7.3 U < 3.13 4.17 U < 3.06 4.08 U < 3.5 7.0 U

8:2 FTS - < 3.7 7.3 U < 3.01 4.01 U < 3.8 7.5 U < 3.7 7.3 U < 3.13 4.17 U < 3.06 4.08 U < 3.5 7.0 U

9Cl-PF3ONS - - - - - < 2.01 4.01 U - - - - - - - - < 2.09 4.17 U < 2.04 4.08 U - - - -

ADONA - - - - - < 2.01 4.01 U - - - - - - - - < 2.09 4.17 U < 2.04 4.08 U - - - -

FOSA - < 1.9 3.7 U < 2.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 2.09 4.17 U < 2.04 4.08 U < 1.8 3.5 U

HFPO-DA - < 3.7 7.3 < 4.01 8.03 U < 3.8 7.5 < 3.7 7.3 < 4.17 8.35 U < 4.08 8.17 U < 3.5 7.0

NEtFOSA - - - - - < 4.01 8.03 U - - - - - - - - < 4.17 8.35 U < 4.08 8.17 U - - - -

NEtFOSAA - < 3.7 7.3 U < 4.01 8.03 U < 3.8 7.5 U < 3.7 7.3 U < 4.17 8.35 U < 4.08 8.17 U < 3.5 7.0 U

N-EtFOSE - - - - - < 4.01 8.03 U - - - - - - - - < 4.17 8.35 U < 4.08 8.17 U - - - -

NMEFOSA - - - - - < 4.01 8.03 U - - - - - - - - < 4.17 8.35 U < 4.08 8.17 U - - - -

NMeFOSAA - < 3.7 7.3 U < 4.01 8.03 U < 3.8 7.5 U < 3.7 7.3 U < 4.17 8.35 U < 4.08 8.17 U < 3.5 7.0 U

NMeFOSE - - - - - < 4.01 8.03 U - - - - - - - - < 4.17 8.35 U < 4.08 8.17 U - - - -

PFBA - 7.7 1.9 3.7 4.99 3.51 4.01 11 1.9 3.8 11 1.8 3.6 3.90 3.65 4.17 J 3.86 3.57 4.08 J 5.2 1.8 3.5

PFBS - 2.6 1.9 3.7 J 1.91 2.01 4.01 J 5.4 1.9 3.8 5.5 1.8 3.6 4.19 2.09 4.17 4.12 2.04 4.08 3.5 1.8 3.5

PFDA - < 1.9 3.7 U < 3.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

PFDoA - < 1.9 3.7 U < 3.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

PFDS - < 1.9 3.7 U < 3.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

PFHpA - 2.0 1.9 3.7 J 1.69 3.01 4.01 J 4.3 1.9 3.8 4.4 1.8 3.6 < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

PFHpS - < 1.9 3.7 U < 3.01 4.01 U 1.8 1.9 3.8 J 1.9 1.8 3.6 J 1.36 3.13 4.17 J 1.41 3.06 4.08 J 5.2 1.8 3.5

PFHxA - 4.6 1.9 3.7 4.32 2.01 4.01 12 1.9 3.8 12 1.8 3.6 1.79 2.09 4.17 J 1.65 2.04 4.08 J 2.1 1.8 3.5 J

PFHxS - 64 1.9 3.7 40.7 3.01 4.01 110 1.9 3.8 110 1.8 3.6 60.1 3.13 4.17 61.9 3.06 4.08 66 1.8 3.5

PFNA - < 1.9 3.7 U < 2.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 2.09 4.17 U < 2.04 4.08 U < 1.8 3.5 U

PFNS - < 1.9 3.7 U < 3.51 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.65 4.17 U < 3.57 4.08 U < 1.8 3.5 U

PFOA 70 6.7 1.9 3.7 6.02 2.01 4.01 11 1.9 3.8 11 1.8 3.6 3.07 2.09 4.17 J 3.09 2.04 4.08 J 5.0 1.8 3.5

PFOS 70 49 1.9 3.7 34.9 2.01 4.01 54 1.9 3.8 55 1.8 3.6 26.6 2.09 4.17 27.5 2.04 4.08 30 1.8 3.5

PFPeA - 3.8 1.9 3.7 3.11 2.01 4.01 J 4.9 1.9 3.8 5.0 1.8 3.6 1.03 2.09 4.17 J 0.962 2.04 4.08 J 0.92 1.8 3.5 J

PFPeS - 2.6 1.9 3.7 J 3.06 3.01 4.01 J 6.3 1.9 3.8 6.4 1.8 3.6 4.36 3.13 4.17 4.48 3.06 4.08 6.9 1.8 3.5

PFTeDA - < 1.9 3.7 U < 3.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

PFTrDA - < 1.9 3.7 U < 3.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

PFUnDA - < 1.9 3.7 U < 3.01 4.01 U < 1.9 3.8 U < 1.8 3.6 U < 3.13 4.17 U < 3.06 4.08 U < 1.8 3.5 U

Total PFOA+PFOS 70 55.7 1.9 40.92 2.01 65 1.9 66 1.8 29.67 2.09 30.59 2.04 35 1.8

05/09/2023

Water, PFAS by LCMSMS Compliant with QSM 5.3 Table B-15 (ng/L)

Sample ID

Sample Date

CR-PW-02-062123-D

06/21/2023

CR-PW-03-050923

05/09/2023

CR-PW-02-050923-D

05/09/2023

CR-PW-02-062123

06/21/2023

CR-PW-01-062123

06/21/2023

CR-PW-02-050923

05/09/2023

CR-PW-01-050923

AECOM 2-7
Table 2-2

Residential Drinking Water Results

Site Inspection Report, Camp Ripley

Analyte USEPA HAa Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual

11Cl-PF3OUdS - < 2.06 4.12 U - - - - - - - - - - - - - - - - - - - - - - - -

4:2 FTS - < 3.09 4.12 U < 3.9 7.8 U < 3.7 7.3 U < 3.6 7.2 U < 3.7 7.4 U < 3.7 7.4 U < 3.7 7.3 U

6:2 FTS - < 3.09 4.12 U < 3.9 7.8 U < 3.7 7.3 U < 3.6 7.2 U < 3.7 7.4 U 7.9 3.7 7.4 < 3.7 7.3 U

8:2 FTS - < 3.09 4.12 U < 3.9 7.8 U < 3.7 7.3 U < 3.6 7.2 U < 3.7 7.4 U < 3.7 7.4 U < 3.7 7.3 U

9Cl-PF3ONS - < 2.06 4.12 U - - - - - - - - - - - - - - - - - - - - - - - -

ADONA - < 2.06 4.12 U - - - - - - - - - - - - - - - - - - - - - - - -

FOSA - < 2.06 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

HFPO-DA - < 4.12 8.24 U < 3.9 7.8 < 3.7 7.3 < 3.6 7.2 < 3.7 7.4 < 3.7 7.4 < 3.7 7.3

NEtFOSA - < 4.12 8.24 U - - - - - - - - - - - - - - - - - - - - - - - -

NEtFOSAA - < 4.12 8.24 U < 3.9 7.8 U < 3.7 7.3 U < 3.6 7.2 U < 3.7 7.4 U < 3.7 7.4 U < 3.7 7.3 U

N-EtFOSE - < 4.12 8.24 U - - - - - - - - - - - - - - - - - - - - - - - -

NMEFOSA - < 4.12 8.24 U - - - - - - - - - - - - - - - - - - - - - - - -

NMeFOSAA - < 4.12 8.24 U < 3.9 7.8 U < 3.7 7.3 U < 3.6 7.2 U < 3.7 7.4 U < 3.7 7.4 U < 3.7 7.3 U

NMeFOSE - < 4.12 8.24 U - - - - - - - - - - - - - - - - - - - - - - - -

PFBA - 5.08 3.60 4.12 6.5 2.0 3.9 2.0 1.9 3.7 J 20 1.8 3.6 J+ 9.2 1.9 3.7 5.9 1.9 3.7 3.6 1.9 3.7 J

PFBS - 3.08 2.06 4.12 J < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U 3.7 1.9 3.7 1.2 1.9 3.7 J < 1.9 3.7 U

PFDA - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFDoA - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFDS - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFHpA - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U 3.0 1.9 3.7 J 1.5 1.9 3.7 J < 1.9 3.7 U

PFHpS - 5.17 3.09 4.12 < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFHxA - 2.55 2.06 4.12 J < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U 1.8 1.9 3.7 J 7.1 1.9 3.7 < 1.9 3.7 U

PFHxS - 60.4 3.09 4.12 < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U 8.1 1.9 3.7 < 1.9 3.7 U

PFNA - < 2.06 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFNS - < 3.60 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFOA 70 4.03 2.06 4.12 J < 2.0 3.9 U < 1.9 3.7 U 1.1 1.8 3.6 J 10 1.9 3.7 0.92 1.9 3.7 J < 1.9 3.7 U

PFOS 70 20.5 2.06 4.12 < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U 2.3 1.9 3.7 J < 1.9 3.7 U

PFPeA - 1.05 2.06 4.12 J < 2.0 3.9 U < 1.9 3.7 U 0.93 1.8 3.6 J < 1.9 3.7 U 12 1.9 3.7 < 1.9 3.7 U

PFPeS - 6.16 3.09 4.12 < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U 1.2 1.9 3.7 J < 1.9 3.7 U

PFTeDA - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFTrDA - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

PFUnDA - < 3.09 4.12 U < 2.0 3.9 U < 1.9 3.7 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U

Total PFOA+PFOS 70 24.53 2.06 < 2 U < 1.9 U 1.1 1.8 10 1.9 3.22 1.9 < 1.9 U

06/21/2023

Water, PFAS by LCMSMS Compliant with QSM 5.3 Table B-15 (ng/L)

Sample ID

Sample Date

CR-PW-08-050923

05/09/2023

CR-PW-09-050923

05/09/2023

CR-PW-06-050923

05/09/2023

CR-PW-07-050923

05/09/2023

CR-PW-04-050923

05/09/2023

CR-PW-05-050923

05/09/2023

CR-PW-03-062123

AECOM 2-8
Table 2-2

Residential Drinking Water Results

Site Inspection Report, Camp Ripley

Analyte USEPA HAa Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual

11Cl-PF3OUdS - - - - - - - - - - - - - - - - - - - - - < 1.98 3.96 U - - - -

4:2 FTS - < 3.7 7.3 U < 3.8 7.5 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 2.97 3.96 U < 3.8 7.5 U

6:2 FTS - < 3.7 7.3 U < 3.8 7.5 U < 3.7 7.3 U 6.7 3.7 7.4 J 150 3.7 7.4 30.4 2.97 3.96 < 3.8 7.5 U

8:2 FTS - < 3.7 7.3 U < 3.8 7.5 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 2.97 3.96 U < 3.8 7.5 U

9Cl-PF3ONS - - - - - - - - - - - - - - - - - - - - - < 1.98 3.96 U - - - -

ADONA - - - - - - - - - - - - - - - - - - - - - < 1.98 3.96 U - - - -

FOSA - < 1.9 3.7 U 1.0 1.9 3.8 J < 1.8 3.6 UJ 0.99 1.9 3.7 J < 1.9 3.7 U < 1.98 3.96 U < 1.9 3.7 U

HFPO-DA - < 3.7 7.3 < 3.8 7.5 < 3.7 7.3 < 3.7 7.4 < 3.7 7.4 < 3.96 7.91 U < 3.8 7.5

NEtFOSA - - - - - - - - - - - - - - - - - - - - - < 3.96 7.91 U - - - -

NEtFOSAA - < 3.7 7.3 U < 3.8 7.5 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.96 7.91 U < 3.8 7.5 U

N-EtFOSE - - - - - - - - - - - - - - - - - - - - - < 3.96 7.91 U - - - -

NMEFOSA - - - - - - - - - - - - - - - - - - - - - < 3.96 7.91 U - - - -

NMeFOSAA - < 3.7 7.3 U < 3.8 7.5 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.96 7.91 U < 3.8 7.5 U

NMeFOSE - - - - - - - - - - - - - - - - - - - - - < 3.96 7.91 U - - - -

PFBA - 1.5 1.9 3.7 J 3.5 1.9 3.8 J 3.7 1.8 3.6 23 1.9 3.7 16 1.9 3.7 7.26 3.46 3.96 4.6 1.9 3.7

PFBS - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 11 1.9 3.7 7.5 1.9 3.7 5.25 1.98 3.96 < 1.9 3.7 U

PFDA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 2.97 3.96 U < 1.9 3.7 U

PFDoA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 2.97 3.96 U < 1.9 3.7 U

PFDS - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 2.97 3.96 U < 1.9 3.7 U

PFHpA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 27 1.9 3.7 8.5 1.9 3.7 2.79 2.97 3.96 J < 1.9 3.7 U

PFHpS - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 9.7 1.9 3.7 1.0 1.9 3.7 J < 2.97 3.96 U < 1.9 3.7 U

PFHxA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 93 1.9 3.7 41 1.9 3.7 13.0 1.98 3.96 < 1.9 3.7 U

PFHxS - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 350 9.0 18 52 1.9 3.7 34.0 2.97 3.96 < 1.9 3.7 U

PFNA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 1.98 3.96 U < 1.9 3.7 U

PFNS - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 3.46 3.96 U < 1.9 3.7 U

PFOA 70 < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 47 1.9 3.7 4.7 1.9 3.7 2.67 1.98 3.96 J < 1.9 3.7 U

PFOS 70 < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 350 9.0 18 24 1.9 3.7 18.6 1.98 3.96 < 1.9 3.7 U

PFPeA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 82 1.9 3.7 66 1.9 3.7 18.9 1.98 3.96 < 1.9 3.7 U

PFPeS - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U 20 1.9 3.7 8.8 1.9 3.7 5.73 2.97 3.96 < 1.9 3.7 U

PFTeDA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 2.97 3.96 U < 1.9 3.7 U

PFTrDA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 2.97 3.96 U < 1.9 3.7 U

PFUnDA - < 1.9 3.7 U < 1.9 3.8 U < 1.8 3.6 U < 1.9 3.7 U < 1.9 3.7 U < 2.97 3.96 U < 1.9 3.7 U

Total PFOA+PFOS 70 < 1.9 U < 1.9 U < 1.8 U 397 9 28.7 1.9 21.27 1.98 < 1.9 U

05/09/2023

Water, PFAS by LCMSMS Compliant with QSM 5.3 Table B-15 (ng/L)

Sample ID

Sample Date

CR-PW-13-062123

06/21/2023

CR-PW-14-051023

05/10/2023

CR-PW-12-050923

05/09/2023

CR-PW-13-050923

05/09/2023

CR-PW-11-050923

05/09/2023

CR-PW-11-050923-D

05/09/2023

CR-PW-10-050923

AECOM 2-9
Table 2-2

Residential Drinking Water Results

Site Inspection Report, Camp Ripley

Analyte USEPA HAa Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual

11Cl-PF3OUdS - - - - - - - - - - - - - < 1.99 3.98 U - - - - - - - - - - - -

4:2 FTS - < 3.7 7.4 U < 3.7 7.3 U < 3.9 7.8 U < 2.99 3.98 U < 3.6 7.2 U < 3.6 7.2 U < 3.7 7.3 U

6:2 FTS - < 3.7 7.4 U 55 3.7 7.3 < 3.9 7.8 U < 2.99 3.98 U < 3.6 7.2 U < 3.6 7.2 U < 3.7 7.3 U

8:2 FTS - < 3.7 7.4 U < 3.7 7.3 U < 3.9 7.8 U < 2.99 3.98 U < 3.6 7.2 U < 3.6 7.2 U < 3.7 7.3 U

9Cl-PF3ONS - - - - - - - - - - - - - < 1.99 3.98 U - - - - - - - - - - - -

ADONA - - - - - - - - - - - - - < 1.99 3.98 U - - - - - - - - - - - -

FOSA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 1.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

HFPO-DA - < 3.7 7.4 < 3.7 7.3 < 3.9 7.8 < 3.98 7.96 U < 3.6 7.2 < 3.6 7.2 < 3.7 7.3

NEtFOSA - - - - - - - - - - - - - < 3.98 7.96 UJ - - - - - - - - - - - -

NEtFOSAA - < 3.7 7.4 U < 3.7 7.3 U < 3.9 7.8 U < 3.98 7.96 U < 3.6 7.2 U < 3.6 7.2 U < 3.7 7.3 U

N-EtFOSE - - - - - - - - - - - - - < 3.98 7.96 U - - - - - - - - - - - -

NMEFOSA - - - - - - - - - - - - - < 3.98 7.96 UJ - - - - - - - - - - - -

NMeFOSAA - < 3.7 7.4 U < 3.7 7.3 U < 3.9 7.8 U < 3.98 7.96 U < 3.6 7.2 U < 3.6 7.2 U < 3.7 7.3 U

NMeFOSE - - - - - - - - - - - - - < 3.98 7.96 U - - - - - - - - - - - -

PFBA - 18 1.9 3.7 19 1.8 3.6 7.2 2.0 3.9 6.18 3.48 3.98 1.5 1.8 3.6 J 3.5 1.8 3.6 J 6.9 1.8 3.6 J+

PFBS - 0.98 1.9 3.7 J 7.1 1.8 3.6 21 2.0 3.9 20.6 1.99 3.98 < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFDA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 2.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFDoA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 2.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFDS - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 2.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFHpA - < 1.9 3.7 U 6.1 1.8 3.6 4.3 2.0 3.9 3.58 2.99 3.98 J < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFHpS - < 1.9 3.7 U < 1.8 3.6 U 1.8 2.0 3.9 J 1.67 2.99 3.98 J < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFHxA - < 1.9 3.7 UJ 34 1.8 3.6 18 2.0 3.9 16.5 1.99 3.98 < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFHxS - < 1.9 3.7 U 29 1.8 3.6 100 2.0 3.9 95.9 2.99 3.98 < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFNA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 1.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFNS - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 3.48 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFOA 70 < 1.9 3.7 U 2.5 1.8 3.6 J 6.8 2.0 3.9 5.96 1.99 3.98 < 1.8 3.6 U < 1.8 3.6 U 2.5 1.8 3.6 J

PFOS 70 < 1.9 3.7 U 11 1.8 3.6 61 2.0 3.9 52.1 1.99 3.98 < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFPeA - < 1.9 3.7 U 62 1.8 3.6 12 2.0 3.9 10.4 1.99 3.98 < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFPeS - < 1.9 3.7 U 5.5 1.8 3.6 25 2.0 3.9 22.4 2.99 3.98 < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFTeDA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 2.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFTrDA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 2.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

PFUnDA - < 1.9 3.7 U < 1.8 3.6 U < 2.0 3.9 U < 2.99 3.98 U < 1.8 3.6 U < 1.8 3.6 U < 1.8 3.6 U

Total PFOA+PFOS 70 < 1.9 U 13.5 1.8 67.8 2 58.06 1.99 < 1.8 U < 1.8 U 2.5 1.8

05/10/2023

Water, PFAS by LCMSMS Compliant with QSM 5.3 Table B-15 (ng/L)

Sample ID

Sample Date

CR-PW-19-051023

05/10/2023

CR-PW-20-051023

05/10/2023

CR-PW-17-062123

06/21/2023

CR-PW-18-051023

05/10/2023

CR-PW-16-051023

05/10/2023

CR-PW-17-051023

05/10/2023

CR-PW-15-051023

AECOM 2-10
Table 2-2

Residential Drinking Water Results

Site Inspection Report, Camp Ripley

Analyte USEPA HAa Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual Result LOD LOQ Qual

11Cl-PF3OUdS - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

4:2 FTS - < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.6 7.2 U < 3.6 7.1 U

6:2 FTS - < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.6 7.2 U < 3.6 7.1 U

8:2 FTS - < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.6 7.2 U < 3.6 7.1 U

9Cl-PF3ONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

ADONA - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

FOSA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

HFPO-DA - < 3.7 7.3 < 3.7 7.4 < 3.7 7.3 < 3.7 7.4 U < 3.7 7.4 U < 3.6 7.2 U < 3.6 7.1 U

NEtFOSA - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

NEtFOSAA - < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.6 7.2 U < 3.6 7.1 U

N-EtFOSE - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

NMEFOSA - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

NMeFOSAA - < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.3 U < 3.7 7.4 U < 3.7 7.4 U < 3.6 7.2 U < 3.6 7.1 U

NMeFOSE - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PFBA - 7.1 1.9 3.7 4.8 1.9 3.7 J+ 4.9 1.9 3.7 J+ < 1.9 3.7 U 0.97 1.9 3.7 J < 1.8 3.6 U 1.2 1.8 3.6 J

PFBS - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U 0.95 1.9 3.7 J < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFDA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFDoA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFDS - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFHpA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFHpS - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFHxA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFHxS - 0.95 1.9 3.7 J < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFNA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFNS - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFOA 70 2.4 1.9 3.7 J < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U 0.92 1.9 3.7 J < 1.8 3.6 U < 1.8 3.6 U

PFOS 70 < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFPeA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFPeS - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFTeDA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFTrDA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

PFUnDA - < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.9 3.7 U < 1.8 3.6 U < 1.8 3.6 U

Total PFOA+PFOS 70 2.4 1.9 < 1.9 U < 1.9 U < 1.9 U 0.92 1.9 < 1.8 U < 1.8 U

05/10/2023

Water, PFAS by LCMSMS Compliant with QSM 5.3 Table B-15 (ng/L)

Sample ID

Sample Date

CR-PW-25-051123

05/11/2023

CR-PW-26-051123

05/11/2023

CR-PW-23-051123

05/11/2023

CR-PW-24-051123

05/11/2023

CR-PW-22-051023

05/10/2023

CR-PW-22-051023-D

05/10/2023

CR-PW-21-051023

AECOM 2-11
Table 2-2

Residential Drinking Water Results

Site Inspection Report, Camp Ripley

Grey Fill Detected concentration exceeded USEPA HA Chemical Abbreviations

11Cl-PF3OUdS 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid

References 4:2 FTS 4:2 fluorotelomer sulfonate

6:2 FTS 6:2 fluorotelomer sulfonate

8:2 FTS 8:2 fluorotelomer sulfonate

9Cl-PF3ONS 9-Chlorohexadecafluoro-3-oxanonane-1-sulfonic acid

ADONA 4,8-dioxa-3H-perfluorononanoate

Interpreted Qualifiers FOSA Perfluorooctane sulfonamide

J = Estimated concentration HFPO-DA Hexafluoropropylene oxide dimer acid

J+ = Estimated concentration, biased high NEtFOSA N-ethyl perfluorooctane sulfonamide

U = The analyte was not detected at a level greater than or equal to the LOD NEtFOSAA 2-(N-Ethylperfluorooctanesulfonamido) acetic acid

UJ = The analyte was not detected at a level greater than or equal to the adjusted LOD. However, the reported adjusted LOD is approximate and may be inaccurate or imprecise. N-EtFOSE N-ethyl perfluorooctane sulfonamido ethanol

NMEFOSA N-methyl perfluorooctane sulfonamide

Acronyms and Abbreviations NMeFOSAA N-methyl perfluorooctanesulfonamidoacetic acid

CR Camp Ripley NMeFOSE N-methyl perfluorooctane sulfonamido ethanol

D Duplicate PFBA perfluorobutanoic acid

HA Health Advisory PFBS perfluorobutanesulfonic acid

ID identification PFDA perfluorodecanoic acid

LCMSMS Liquid Chromatography Mass Spectrometry PFDoA perfluorododecanoic acid

LOD Limit of Detection PFDS perfluorodecanesulfonic acid

LOQ Limit of Quantitation PFHpA perfluoroheptanoic acid

PFAS per- and polyfluoroalkyl substances PFHpS perfluoroheptanesulfonic acid

PW potable well PFHxA perfluorohexanoic acid

QSM Quality Systems Manual PFHxS perfluorohexanesulfonic acid

Qual Interpreted Qualifier PFNA perfluorononanoic acid

USEPA United States Environmental Protection Agency PFNS perfluorononanesulfonic acid

ng/l nanogram per liter PFOA perfluorooctanoic acid

- Not applicable PFOS perfluorooctanesulfonic acid

< analyte not detected above the LOD PFPeA perfluoropentanoic acid

PFPeS perfluoropentanesulfonic acid

PFTeDA perfluorotetradecanoic acid

PFTrDA perfluorotridecanoic acid

PFUnDA perfluoro-n-undecanoic acid

a. United States Environmental Protection Agency. 2016. Drinking Water Health Advisory for 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 PFOS. Office of Water (4304T). Health

and Ecological Criteria Division, Washington, DC 20460. EPA Document Number: 822-R-16-004. May 2016.

AECOM 2-12
CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

11/1/2022

11/1/2022

PROJECT Site Inspection at Camp Ripley, MN

1:253,440

11/1/2022 ­ Figure 2-1 PM CM 11/1/2022

12420 Milestone Center Drive

Germantown, MD 20876

Facility Location

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

Intermap, INCREMENT P, NRCan, Esri Japan, METI,

Legend

Facility Boundary

0 2 4 8

Miles

Camp Ripley

^_

AECOM 2-13
CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

9/1/2023

9/1/2023

PROJECT Site Inspection at Camp Ripley, MN

1:24,000

9/1/2023 ­ Figure 2-2 PM CM 9/1/2023

12420 Milestone Center Drive

Germantown, MD 20876

Facility Topography

Base Map: USGS The National Map: National

Boundaries Dataset, 3DEP Elevation Program,

Legend

Facility Boundary

0 1,000 2,000 4,000

Feet 10 Foot Contour Interval.

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250125

Well ID 641304

L Well

N Well

H Well, BLDG 2-248

536846

536845

530012

482900

773250

774333

Lit tl e

N okasipp i River

Hay Cre ek

Lit tle El k Ri ve r

Seve nmil eCr eek

Pil l a g er Cr eek

Nok as ippi R iver

Broken Bow Creek

Fl

etc h erCreek

Sou th Branch Littl e El kRiver

Crow Wing Rive r

GullRiver

Miss is sippi Rive r

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

6/16/2023

6/16/2023

PROJECT Site Inspection at Camp Ripley, MN

1:158,400

6/16/2023 ­ Figure 2-3 PM CM 6/16/2023

12420 Milestone Center Drive

Germantown, MD 20876

Groundwater Features

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

and the GIS User Community

Legend

Facility Boundary

Water Body

Wetland

River/Stream

Canal/Ditch

Groundwater Flow

Direction

Wells

!P Domestic

!P Commercial

!5 Industrial

!5 Irrigation

A!

Monitoring /

Observation /

Piezometer

A! Other/Unknown

&<

Drinking Water Supply

Geology

Mafic Intrusions

Gray Granodiorite to

Granite Intrusions

Slate & Graywacke

Pokegama Quartzite

Little Falls Formation

Mille Lacs and North

Range Groups &

Equivalent Sedimentary

Rocks

Iron Formation in the

Cayuna North and

South Ranges & Mille

Lacs Group

Interlayered Volcanic &

Sedimentary Rocks

Interlayered Volcanic,

Volcaniclastic,

Sedimentary, &

Hypabyssal Intrusive

Rocks

Granitic Intrusion

Dioritic to Granodioritic

Intrusion

Schist & Tonalitic to

Granodioritic

Paragneiss

Volcaniclastic Rocks of

Felsic to Intermediate

Composition 0 1.25 2.5 5

Miles

AECOM 2-15
!?

!?

!?

!?

!?

!?

!? !?

!?

!?

!?

!?

!?

!?

!?

!?!?

!?

!? !?

!?

!?

!?

!?

!?

!?

!?

!?

!? !?

&<

&<

&<

536846 is 1.7 mi to NW

AOI01-01

1129.13

AOI02-01

1134.65

AOI04-01

1134.60

AOI04-02

1134.36

AOI04-03

1134.48

AOI04-04

1133.73

AOI05-01

Dry on 6/15

AOI05-02

Dry on 6/15

AOI05-03

1190.04

AOI05-04

1200.66

AOI02-02

1132.23

AOI02-03

1134.35

AOI01-02

1128.52

AOI01-03

1128.70

AOI04-05

1130.49

AOI03-01

1124.26

AOI03-02

1124.45

AOI03-03

1124.10

AOI06-01

1120.37

AOI06-02

1120.05

AOI06-03

1119.75

AOI07-01

1129.10

AOI07-02

1127.28

AOI07-03

1126.15

AOI07-04

1124.64

AOI08-01

1126.91

AOI08-02

1126.49

AOI08-03

1136.85

AOI05-05

1120.62

AOI05-06

1109.49

773250

1128.66

482900

1122.07

530012

1126.36

Mississippi River

1110

1120

1134

1120

1128

1124

1130

1126

1124

1132

1126

1128

1132

1134

1130

1122

1122

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

the GIS User Community

12420 Milestone Center Drive

Germantown, MD 20876 Figure 2-4

Groundwater Elevations,

June 2022

ARNG

Site Inspection at Camp Ripley, MN

CLIENT

REVISED

SCALE

PROJECT

5/17/2023

1:17,400 5/17/2023

MS 5/17/2023

EB

GIS BY

CHK BY

PM CM 5/17/2023

&<

Existing Facility Well

!? Soil Boring Location

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Groundwater Elevation Contour

Inferred Groundwater Elevation Contour

Groundwater Flow Direction

Groundwater elevations in feet NAVD88.

Existing permanent well AOI05-536846 is located a significant distance

from the rest of the wells and thus was not included in groundwater

contours.

Wells AOI05-01 and AOI05-02 were dry during the synoptic gauging

event on 15 June 2022 and thus were not included.

Wells AOI05-01 and AOI05-02 were dry during the synoptic gauging

event on 15 June 2022 and thus are not shown. Depth to water

measurements collected at AOI 5 were much shallower than the rest of

the cantonment area, so AOI 5 was interpreted to be in a zone of perched

groundwater. Additionally, there are not enough data points in AOI 5 to

establish separate contours for this area.

­

0 725 1,450 2,900

Feet

AECOM 2-16
Li tt le

N okasip p iRiv er

Hay C reek

Flet c her Creek

Ted B

or

ok

Creek

S evenmil eCre e k

Pil l a ge rCreek

Gull River

Lit tle El k R iver

Rice Creek

South BranchLittle El kRiver

Nok a sippi Ri ver

Fsi

h T rap Creek

Cr owWing River

Long P rai ri e River

M is s issippi R i ver

Mosquito

Creek

Watershed

Gull Lake

Watershed

Gull River

Watershed

Pillager

Creek

Watershed

Crow Wing

River

Watershed

Sevenmile

Creek

Watershed

Lake Placid-Crow

Wing River

Watershed

Fletcher

Creek

Watershed

City of Little

Falls-Mississippi

River Watershed

Mud Lake-Mississippi

River Watershed

Crow

Wing Lake

Watershed

Broken Bow

Creek-Mississippi

River Watershed

Hay Creek

Watershed

Little

Nokasippi River

Watershed

Nokasippi

River

Watershed

Round Lake-Hay

Creek Watershed

Headwaters

Little Elk

River Watershed

South Branch

Little Elk

River Watershed

Little

Elk River

Watershed

City of

Brainerd-Mississippi

River Watershed

Long Prairie

River

Watershed

Fish Trap

Lake-Fish Trap

Creek Watershed

Shamineau Lake

Watershed

Rice Creek

Watershed

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

11/1/2022

11/1/2022

PROJECT Site Inspection at Camp Ripley, MN

1:190,080

11/1/2022 ­ Figure 2-5 PM CM 11/1/2022

12420 Milestone Center Drive

Germantown, MD 20876

Surface Water Features

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

and the GIS User Community

Legend

0 1.5 3 6

Miles

Legend

Facility Boundary

Water Body

Wetland

River/Stream

Canal/Ditch

Surface Water Flow Direction

AECOM 2-17
Infiltration

Basin A

Infiltration

Basin B

Infiltration

Basin C

Infiltration

Basin D

Infiltration Basin E

AOI 3

AOI 5

AOI 6

AOI 1

AOI 2

AOI 4

AOI 7

AOI 8

REVISED

SCALE

CLIENT

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

GIS BY

CHK BY

PM

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

User Community

MS

EB

CM

6/14/2023

6/14/2023

6/14/2023

1:17,416

6/14/2023

12420 Milestone Center Drive

Germantown, MD 20876 Figure 2-6

Stormwater Drainage Network ­ Area of Interest

Facility Boundary

Stormwater Drainage Network

Existing Stormwater Retention Basin

Stormwater Infiltration Basin installed after 2009

AOI 5 Sludge Spread Site not visible within map extent

All Stormwater Infiltration Basins depicted are approximate locations of drainage areas. Please do not use them for any types of calculations

AECOM 2-18
AOI 5

AOI 4

AOI 7

Figure 2-7

Drinking Water Results

12420 Milestone Center Drive

Germantown, MD 20876

Base Map: USGS The National Map: National Boundaries Dataset, 3DEP Elevation

Program, Geographic Names Information System, National Hydrography Dataset,

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

9/12/2023

9/12/2023

9/12/2023

MS

GR

CM

GIS BY

CHK BY

PM

9/12/2023

1:10,440

0 435 870 1,740

Feet

­ Legend

Drinking Water Sampling Area

Area of Interest

Facility Boundary

Groundwater Flow Direction

AECOM 2-19
THIS PAGE INTENTIONALLY BLANK 

2-20
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 3-1

3. Summary of Areas of Interest

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

released historically. After the Final PA Report was issued, ARNG adopted a more conservative 

policy to investigate AFFF storage and use areas where no previous releases were reported; thus, 

two additional AOIs were added after the PA. A total of 14 potential release areas were identified 

at Camp Ripley and grouped into eight AOIs (AECOM, 2022a). The potential release areas are 

shown on Figure 3-1. 

3.1 AOI 1 TriMaxTM Discharge Area and Building 8-197

AOI 1 is the TriMaxTM Discharge Area and the Fire Station (Building 8-197). A potential PFAS 

release to soil occurred in the early 2000s, when a TriMaxTM-30 fire extinguisher was discharged 

to the ground. Interviewees were unsure whether the fire extinguisher that was discharged 

contained AFFF or was a training fire extinguisher. 

Camp Ripley Fire and Emergency Services has three firetrucks and three all-terrain vehicles, all 

with AFFF capability in the Fire Station (Building 8-197). Nozzle testing has not been conducted 

at Camp Ripley, and the firetrucks are washed at the current Fire Station (Building 8-197). Wash 

water is discharged to a stormwater drain. No information regarding the concentration or type of 

AFFF potentially discharged was available.

3.2 AOI 2 Burn Pit Fire Training Area

AOI 2 is the Burn Pit fire training area (FTA). A single coordinated fire training event was identified 

during the PA. The event occurred at the Burn Pit FTA, in the late 1980s, between the MNARNG 

and the US Air Force (USAF) 133rd Airlift Wing from Minneapolis. The burn pit may have been 

used for coordinated fire training exercises on multiple occasions; however, additional uses were 

not confirmed during the PA process.

3.3 AOI 3 DHS Demonstration

AOI 3 is the Department of Homeland Security (DHS) Demonstration at the Emergency 

Management Training Center (EMTC). A coordinated fire training event between DHS, MNARNG, 

and local municipalities occurred in November 2014 using approximately one gallon of AFFF 

concentrate and 100 gallons of water. Camp Ripley Fire and Emergency Services personnel 

indicated that not all the foam mixture was used during the event; however, the final disposition 

of the remaining foam mixture could not be determined during the PA process.

3.4 AOI 4 USFPO Warehouse, CMA Shop, and CMA Discharge 

Area

AOI 4 consists of the US Property and Fiscal Office (USPFO) warehouse, Combined Maintenance 

Activity (CMA) Shop, and CMA Discharge Area. Unused or expired fire equipment from MNARNG 

facilities is shipped to the USPFO warehouse at Camp Ripley. At the time of the PA, the fire 

equipment, including TriMaxTM fire extinguishers, was stored and/or processed at the USPFO 

prior to reutilization or disposition. According to USPFO warehouse personnel interviews 

conducted during the PA, TriMaxTM fire extinguishers have been returned to the warehouse for 

disposition. Seven TriMaxTM fire extinguishers from the Holman Field Army Aviation Support 

Facility (AASF) in St. Paul, Minnesota were received empty, nine TriMaxTM fire extinguishers from 

the St. Cloud AASF containing AFFF were received full and are at the warehouse, and six to 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 3-2

seven units from Camp Ripley were received, but it was unknown if the units were received full 

or emptied at the airfield.

Due to the presence of compressed gas cylinders, TriMaxTM fire extinguishers must be 

demilitarized prior to final disposition. Demilitarization of the TriMaxTM fire extinguishers requires 

the equipment to be physically destroyed by the CMA Shop. For demilitarization, the USPFO 

equipment specialist furnishes special instructions regarding the degree of physical destruction 

of the equipment to the CMA. According to CMA interviewees, AFFF was dispensed and allowed 

to dissipate to the ground surface by the MNARNG during demilitarization of a TriMaxTM-30 fire 

extinguisher in approximately 2010. The discharge area is in proximity to up-and side-gradient 

onsite drinking water supply wells L Well and N Well, as well as downgradient onsite drinking 

water supply well H Well. These drinking water supply wells are in operation. As of June 2021, 

the facility processes the TriMaxTM units by draining and triple rinsing. The solution and rinsate 

are handled and managed in accordance with Camp Ripley/Defense Logistics Agency guidelines 

and stored in the CMA Shop hazardous waste storage room.

3.5 AOI 5 Wastewater Treatment Plant and Sludge Spread Site 

AOI 5 consists of two related but non-collocated areas: the WWTP located in the southeast of the 

facility adjacent to the Mississippi River and the Sludge Spread Site northwest of the cantonment 

area. These two areas were grouped as AOI 5 due to a shared source of potential PFAS impacts. 

Camp Ripley has been permitted to perform land application of sludge from the WWTP at the 

Sludge Spread Site since 1987. Because the WWTP does not contain a treatment system for 

PFAS, it is possible that land application of sludge containing PFAS occurred at the Sludge Spread 

Site. The Sludge Spread Site is located upgradient at an elevation approximately 60 feet above

AOI 1. 

3.6 AOI 6 Stormwater Infiltration Basin

AOI 6 is a stormwater infiltration basin located in the northeast portion of the facility adjacent to 

the Mississippi River. AOI 6 receives stormwater from the northeast portion of the cantonment 

area to include stormwater from the practical fire training exercises that occurred at the EMTC

(AOI 3) in November 2014. Camp Ripley Fire and Emergency Services personnel indicated that 

not all of the foam mixture was used during the exercises; however, the final disposition of the 

remaining foam mixture was likely disposed of in the stormwater sewer system, which drains to a 

stormwater infiltration basin. The EMTC fire training exercise area (AOI 3), stormwater sewer, and 

stormwater infiltration basin are all located within the cantonment area.

3.7 AOI 7 Buildings 2-166, 2-203, 2-223, and 2-272

AOI 7 consists of four potential release areas, as described below. 

3.7.1 Building 2-166

The MNARNG 434th Support Maintenance Company, established in 2010, trains with Camp 

Ripley Fire and Emergency Services and assists in fire emergency response at Camp Ripley. The 

434th stores three firetrucks with AFFF capacity at the old Combined Support Maintenance Shop 

(CSMS) (Building 2-166). Additionally, significant vehicle maintenance for current or previous fire 

support vehicles would have been performed at Building 2-166. Details regarding the type of AFFF 

were not available for review; however, the AFFF is being considered as PFAS-containing. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 3-3

3.7.2 Building 2-203

The City of Randall, approximately 8 miles west of Camp Ripley, provided fire emergency 

response for structural fires in the cantonment area at Camp Ripley from the 1970s until 2010. 

From the 1970s until the 1980s, in the event of a fire emergency at the facility, the City of Randall 

utilized two firetrucks owned by Camp Ripley and stored at Building 2-203 for firefighting. No 

information was available regarding whether the firetrucks stored at Building 2-203 were washed 

or whether the firetrucks had maintenance issues; however, it was noted that nozzle testing was 

not conducted with AFFF. Building 2-203 had floor drains plumbed to an oil-water separator, which 

routed to the sanitary sewer and the WWTP at Camp Ripley.

3.7.3 Building 2-223

At the time of the PA, Bulk AFFF was stored in the State Warehouse (Building 2-223) and 

transferred to Camp Ripley firetrucks at the Fire Station (Building 8-197, AOI 1) on an as-needed 

basis. According to the purchasing supervisor, AFFF was last ordered in 2011. During the PA site 

visit in 2018, approximately 300- gallons of Ansul® 3% AFFF and 55 gallons of Phos-Chek® Class 

A foam were observed at Building 2-223.

3.7.4 Building 2-272

According to the retired City of Randall Fire Chief, Camp Ripley did not start using or storing AFFF 

until the 1980s. Bulk AFFF and the crash rescue truck were stored in the west bay of Building 2-

272 to support operations. At the time of the PA, the roads and grounds supervisor at Building 2-

272 did not recall training with AFFF, truck washing, or maintenance issues with the USAF’s 

firetruck. The crash rescue truck was returned to Minneapolis along with USAF’s 133rd Airlift Wing 

each spring; however, the bulk AFFF, which belonged to Camp Ripley, remained stored in Building 

2-272. No information was available on the amount, type, or concentration of AFFF stored in

Building 2-272 at the time of the PA. Floor drains in Building 2-272 are connected to the sanitary

sewer.

3.8 AOI 8 Building 8-195

AOI 8 is Building 8-195. A large crash rescue truck was brought to the facility by the Airfield Fire 

Chief and stored in the old hangar (Building 8-195) following airfield re-paving in 1986-1987. 

Additionally, during winter operations, volunteers would standby with this crash rescue truck at 

Building 8-195 during incoming flights. The lead mechanic at the old hangar (Building 8-195) did 

not recall any maintenance issues with this crash rescue firetruck; however, he did indicate that 

any serious maintenance issues would have required repair at the CSMS (Building 2-166). It is 

unclear if the truck had AFFF capability. Building 8-195 was renovated in 2010 and is currently a 

Morale Welfare Recreation facility. 

3.9 Adjacent Sources

Four off-facility, potential sources were identified adjacent to Camp Ripley during the PA and are 

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

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

investigated as part of this SI. 

3.9.1 Coal Train Collision

On 14 June 1984 two Burlington Northern Railroad Company coal trains collided head-on in a 

wooded area near Motley, Minnesota, approximately one mile south of the intersection of Highway 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 3-4

210 and Bridgeman Road in May Township. The geographic coordinates of the collision are 

46°19'22.1"N and 94°34'46.9"W (Figure 3-1). A massive fire resulted from the collision, and 

approximately 100 gallons of AFFF concentrate were taken from Camp Ripley by firefighters from 

the Cities of Motley, Staples, and Pillager to extinguish the fire. Motley is approximately 30 miles 

north of Camp Ripley. 

3.9.2 Fuel Tanker Accident

According to interviewees, a fuel tanker rolled over on Highway 371 near Brainerd, Minnesota 

sometime in the 1990s. The fuel tanker did not catch fire; however, AFFF was dispensed to 

smother the fuel vapors. Approximately 100 gallons of AFFF concentrate were taken from Camp 

Ripley for this emergency event. The exact location of the fuel tanker rollover could not be 

determined. Brainerd is approximately 25 miles north of Camp Ripley. 

3.9.3 Central Minnesota Ethanol Cooperative Fire

On 29 October 2007, smoldering wood chips in a gasification silo at the Central Minnesota Ethanol 

Cooperative (also referred to as “Co-op”) caused the roof of the silo to explode and collapse.

Approximately 300 gallons of alcohol-resistant AFFF (AR-AFFF) concentrate were taken from 

Camp Ripley by the Little Falls Fire Department to respond to the emergency event. The Central 

Minnesota Ethanol Co-op is about 5 miles south of Camp Ripley. The geographic coordinates are 

46°01'16.0"N; 94°20'20.8"W (Figure 3-1).

3.9.4 Keystone Automotive

One additional source of PFAS was identified in a report by Delta Consultants titled 

Perfluorocarbon-Containing Firefighting Foams and Their Use in Minnesota: Keystone 

Automotive (Delta Consultants, 2010). Keystone Automotive is a chrome plating operation in 

nearby Brainerd, Minnesota (Figure 3-1). Historically, Keystone Automotive used FumetrolTM 140 

Mist Suppressant to reduce surface tension in chrome plating baths and reduce emissions of 

hexavalent chromium from the plating solution. FumetrolTM 140 Mist Suppressant contains PFAS 

between 1% and 7% by weight. The company reportedly used approximately 30 gallons per year 

of the solution before switching to a different mist suppressant in September 2007 (US Health 

and Human Services, 2008). Brainerd is approximately 25 miles north of Camp Ripley.
!P

!P

!P

!P

!5

!P

!P

!P

!5

!5

!P

!P

!P

!5

!5

!P

!P

!P

!P

!P

!P

!P

!5

!P

!P

!P

!P

!5

!P

!P

!P

!P

!P

!P

!P

!P

!P

!P

A!

!5

!5

!P

!5

!P

!5

!5

!P

!P

!P

!P !P

!P

!P

!P

!P

!P

!P

!P

!P

!P !P

!P

!P

!P

!P

!P

!P

!P

!P

!P

!P

A!

!P

!P

!P

!P

!5

!P

!P

!P

A!

!P

!P

!5

!5

!P

!P

!P

!P

!5

!P

!P

!5

!5

!P

A!

A!

A!

A!

A!

A!

A!

A!

&<

&<

&<

&<

AOI 8

AOI 2

AOI 5

AOI 1

AOI 4

AOI 7

AOI 7

AOI 3

AOI 5

AOI 6

CMA Discharge Area

DHS Demonstration

TriMax Discharge Area

Burn Pit FTA

Building 8-195

Building 2-203

Building 2-272

Building 2-166

WWTP

Sludge

Spread Site

Stormwater

Infiltration Basin

Fire Station

(BLDG 8-197)

USPFO Warehouse

Building 2-223

Well ID 641304

L Well

N Well

H Well, BLDG 2-248

530012

250125

482900

773250

774333

Mississippi River

Fletcher

Creek

Watershed City of Little

Falls-Mississippi

River Watershed

Broken Bow

Creek-Mississippi

River Watershed

CMA

Closed Mixed Municipal Landfill

Biosolid Area

0 1,350 2,700 5,400

Feet

­ Figure 3-1

Areas of Interest

12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

5/15/2023

5/15/2023

5/15/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

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

5/15/2023

1:24,000

Area of Interest

Potential Release Area

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Surface Water Flow Direction

Groundwater Flow Direction

!P Domestic Well

!5 Irrigation Well

A! Other/Unknown

A! Monitoring Well

&<

Drinking Water Supply Well

Watersheds

Broken Bow Creek-Mississippi River

City of Little Falls-Mississippi River

Fletcher Creek

Little Elk River

Fuel Tanker 

Accident

Central Minnesota

Ethanol Co-op Fire

Coal Train

Collision Keystone

Automotive

AECOM 3-5
THIS PAGE INTENTIONALLY BLANK 

3-6
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 4-1

4. Project Data Quality Objectives

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

Federal Policy Quality Assurance Project Plan (UFP-QAPP) Addendum (AECOM, 2022a), the 

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

identified in the PA. For each AOI, ARNG determines if further investigation is warranted, a 

removal action is required to address immediate threats, or whether no further action is warranted. 

This SI evaluated groundwater and soil for presence or absence of relevant compounds at each 

of the sampled AOIs.

4.1 Problem Statement

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

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

SLs are presented in Section 6.1 of this report. 

4.2 Information Inputs

Primary information inputs included:

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

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

with the site-specific UFP-QAPP Addendum (AECOM, 2022a); and

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

parameters measured at the time of sampling.

4.3 Study Boundaries

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

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

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

owner(s). The scope of the SI was vertically bounded by depth to groundwater, with a maximum drilled 

depth of 25 feet bgs. Temporal boundaries were limited to the summer season due to climate and 

field resource availability. 

4.4 Analytical Approach

Samples were analyzed by Pace Analytical Gulf Coast, accredited under the DoD Environmental 

Laboratory Accreditation Program (ELAP; Accreditation Number 74960) and the National 

Environmental Laboratory Accreditation Program (NELAP; Certificate Number 01955). Data were 

compared to applicable SLs within this document and decision rules as defined in the SI QAPP 

Addendum (AECOM, 2022a). 

4.5 Data Usability Assessment

The Data Usability Assessment (DUA), which includes the Data Validation Report (DVR), is 

provided as Appendix A. The 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 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 4-2

of the right type, quality, and quantity to support the decision-making (DoD, 2019a; DoD, 2019b; 

USEPA, 2017).

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

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

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

requirements of the SI QAPP Addendum (AECOM, 2022a).
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 5-1

5. Site Inspection Activities

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

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

in accordance with the following approved documents: 

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

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

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

• Final Preliminary Assessment Report, Camp Ripley, Little Falls, Minnesota dated November

2019 (AECOM, 2019);

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

Camp Ripley, Little Falls, Minnesota dated March 2022 (AECOM, 2022a); and

• Final Site Safety and Health Plan, Camp Ripley, Little Falls, Minnesota dated June 2022

(AECOM, 2022b).

The SI field activities were conducted from 6 to 17 June 2022 and consisted of utility clearance,

direct push boring, soil sample collection, temporary monitoring well installation, grab groundwater 

sample collection, synoptic gauging, temporary well abandonment, and land surveying. Field 

activities were conducted in accordance with the SI QAPP Addendum (AECOM, 2022a), except as 

noted in Section 5.9. 

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

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

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

• Eighty-eight (88) soil samples from 32 boring locations;

• Twenty-nine (29) grab groundwater samples from 30 temporary well locations;

• Four (4) grab groundwater samples from four existing permanent wells;

• Thirty-five (35) quality assurance (QA)/quality control (QC) samples.

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

list of samples collected for each media. Field documentation is provided in Appendix B. A Log 

of Daily Notice of Field Activity was completed throughout the SI field activities, which is provided 

in Appendix B1. Sampling forms are provided in Appendix B2, Field Change Request forms are

provided in Appendix B3, land survey data are provided in Appendix B4, and investigationderived waste (IDW) polygons are provided in Appendix B5. Additionally, a photographic log of 

field activities is provided in Appendix C. 

5.1 Pre-Investigation Activities

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

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

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

5.1.1 Technical Project Planning

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

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

Camp Ripley, Little Falls, Minnesota

AECOM 5-2

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

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

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

address the AOIs identified in the PA. 

A combined TPP Meeting 1 and 2 was held on 17 December 2021, prior to SI field activities. The 

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

stakeholders for this SI include the ARNG G-9, MNARNG, USACE, Minnesota Pollution Control 

Agency, AECOM, and representatives familiar with the facility, the regulations, and the community.

Stakeholders were provided the opportunity to make comments on the technical sampling 

approach and methods at the combined TPP Meeting 1 and 2. The outcome of the combined TPP 

Meeting 1 and 2 was memorialized in the SI QAPP Addendum (AECOM, 2022a). 

A TPP Meeting 3 was held on 4 August 2023 to discuss the results of the SI. Meeting minutes for 

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

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

5.1.2 Utility Clearance 

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

north 811 “Gopher State One Call” Minnesota utility clearance provider to notify them of intrusive 

work on 1 June 2022. Additionally, AECOM contracted Ground Penetrating Radar Systems 

(GPRS), a private utility location service, to perform utility clearance. GPRS performed utility 

clearance of the proposed boring locations on 6 and 7 June 2022 with input from the AECOM field 

team and Camp Ripley facility staff. General locating services and ground-penetrating radar were 

used to complete the clearance. Additionally, the first 5 feet of each boring were pre-cleared using 

a hand auger to verify utility clearance in shallow subsurface where utilities would typically be 

encountered. 

5.1.3 Source Water and Sampling Equipment Acceptability

One potable water source at Camp Ripley was sampled on 12 January 2022 to assess usability 

for decontamination of drilling equipment. Results of the sample collected at the wastewater 

treatment building tap (CR-DECON) confirmed this source to be acceptable for use in this

investigation; therefore, it was used throughout the field activities. Specifically, the samples were 

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

water sample associated with the wastewater building tap source used during the SI are provided 

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

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

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

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

(AECOM, 2022a). Prior to the start of field work each day, a Sampling Checklist was completed 

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

member regarding the allowable materials within the sampling environment. 

5.2 Soil Borings and Soil Sampling

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

surfaces. Soil samples were collected via direct push technology (DPT), in accordance with the 

SI QAPP Addendum (AECOM, 2022a). A GeoProbe® 7822DT dual-tube sampling system was 

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

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

soil boring locations are shown on Figure 5-1 and depths are provided Table 5-2. Several boring 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 5-3

locations were adjusted within a 50-feet offset for reasons including drill rig access, utility 

avoidance and bias toward sampling within observed drainage features.

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

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

approximately 2 feet above the groundwater table, and one subsurface soil sample at the midpoint between the surface and the groundwater table. In instances where groundwater was 

encountered at or above 5 feet bgs, only two soil samples were collected (one from surface and 

a second above water table).

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

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

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

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

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

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

During the SI, medium to high-permeability sands were observed as the dominant lithology of the 

unconsolidated sediments below Camp Ripley. The borings were completed at depths between 9 

and 25 feet bgs. A majority of borings contained poorly graded sand, with frequent layers of wellgraded sand. Occasional silt layers were observed in thicknesses ranging from 0.75 to 6 feet in 

thickness. Varying quantities of gravel were noted in several borings, ranging from 0.1 to 4 feet 

thick. Many of the logs also reported varying percentages (ranging from <5% to 45%) of gravel 

included in the sand layers. A sample for grain size analysis was collected at one location, AOI05-

02 and analyzed via ASTM Method D-422. The results indicate that the soil sample was comprised 

of gravel (2.96%), coarse-grained sand (3.69%), fine- to medium-grained sand (61.24%), silt 

(22.91%), and clay (9.19%). Grain size results are presented in Appendix F. These results and 

facility observations are consistent with the understood regional depositional history, which is 

characterized by glacial moraine and outwash facies. 

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

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

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

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

carbon (TOC) (USEPA Method 9060A), pH (USEPA Method 9045D), and grain size (ASTM 

Method D-422) in accordance with the SI QAPP Addendum (AECOM, 2022a).

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

as the accompanying samples. Matrix spike (MS)/MS duplicates (MSDs) were collected at a rate 

of 5% and analyzed for the same parameters as the accompanying samples. In instances when 

non-dedicated sampling equipment was used, such as a hand auger for the shallow soil samples, 

equipment rinsate blanks were collected at a rate of 5% and analyzed for the same parameters 

as the soil samples. A temperature blank was placed in each cooler to ensure that samples were 

preserved at or below 6 degrees Celsius (°C) during shipment.

DPT borings were converted to temporary wells (described below in Section 5.3).Borings were 

installed in grass areas, where possible, to avoid disturbing concrete or asphalt surfaces. Borings 

were abandoned in accordance with the SI QAPP Addendum (AECOM, 2022a) by backfilling the 

borehole with bentonite chips; however, for borings that were advanced through asphalt or 

concrete, boreholes were backfilled with bentonite chips to six inches bgs with the upper six 

inches replaced in kind to match the surrounding surface area (i.e., asphalt cold patch or 

concrete). 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 5-4

5.3 Temporary Well Installation and Groundwater Grab Sampling

Temporary wells were installed using a GeoProbe® 7822DT dual-tube sampling system. Once 

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

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

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

locations; no additional well construction material (i.e., filter sand) was used during the temporary 

well installation. Details regarding deviations during temporary well installation at AOI05-01 are 

discussed in Section 5.9. Additionally, temporary well AOI05-02 was dry after installation, so an 

offset temporary well was installed in an attempt to collect a groundwater sample. A groundwater 

sample was collected from AOI05-02A and soil samples were collected at the original location, 

AOI05-02. The screen intervals for the temporary wells are provided in Table 5-2.

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

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

period, groundwater samples were collected using a peristaltic pump with PFAS-free HDPE 

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

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

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

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

sample was collected. Additionally, a subsample of each groundwater sample was collected in a 

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

foaming was noted in any of the groundwater samples.

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

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

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

Table B-15 in accordance with the SI QAPP Addendum (AECOM, 2022a).

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

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

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

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

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

Following well surveying (described below in Section 5.6), temporary wells were abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2022a) by removing the PVC and backfilling 

the borehole with bentonite chips. Upon completion of well abandonment, the ground surface at 

each location was restored to match existing conditions. For borings that had to be advanced 

through asphalt or concrete, boreholes were backfilled with bentonite chips to six inches bgs with 

the upper six inches replaced in kind to match the surrounding surface area (i.e., asphalt cold 

patch or concrete).

5.4 Existing Permanent Well Groundwater Sampling

During the SI, four existing permanent monitoring wells were sampled for groundwater. The intent 

for sampling these four wells was to identify potential connection between the two AOI 5 release 

areas: the WWTP in the southeast of the cantonment area, and the Sludge Spread Site to the 

northwest of the cantonment area, as well as any potential upgradient sources (AOI05-536846). 

Due to the existing wells’ locations, these wells should be considered independent from the two 

AOI 5 release areas. The locations of the wells are shown on Figure 5-1. Available well 

construction information such as screen intervals, depths to water, and groundwater elevation 

data are presented on Table 5-3.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 5-5

Samples were collected via low-flow sampling methods using a peristaltic pump with disposable 

PFAS-free, HDPE tubing. New tubing was used at each well and the all down-hole equipment 

was 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, DO, and ORP) were measured using a water quality meter and recorded on 

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

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

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

noted in any of the groundwater samples.

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

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

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

Table B-15 in accordance with the SI QAPP Addendum (AECOM, 2022a).

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

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

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

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

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

5.5 Synoptic Water Level Measurements

A synoptic groundwater gauging event was performed on 15 June 2022. Groundwater elevation 

measurements were collected from 28 of the 30 new temporary monitoring wells. Water level 

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

map is provided in Figure 2-4. Temporary wells AOI05-01 and AOI05-02 were dry after installation 

and during the synoptic gauging. The day of the gauging, AOI05-02A was installed in an attempt 

to reach groundwater and was also dry. The day after the gauging, both AOI05-01 and AOI05-

02A were gauged and a small amount of recharge had been observed; however, as these 

measurements were not collected within the same 24-hour period as the rest of the wells, they 

were not used for groundwater contouring shown on Figure 2-4. Additionally, existing permanent 

well AOI05-536846 was located a significant distance from the AOIs and thus was also excluded 

from groundwater contours. Groundwater elevation data are provided in Table 5-2. 

5.6 Surveying

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

following guidelines provided in the SOPs provided in the SI QAPP Addendum (AECOM, 2022a). 

Survey data from the newly installed wells on the facility were collected from 14 to 17 June 2022 

in the applicable North American Datum 1983 State Plane (horizontal) and North American 

Vertical Datum 1988 (vertical). The surveyed well data are provided in Appendix B4. 

5.7 Investigation-Derived Waste

As of the date of this report, the disposal of IDW is not regulated federally. IDW generated during 

the SI is considered non-hazardous waste and was managed in accordance with the SI QAPP 

Addendum (AECOM, 2022a) and with the DAGuidance for Addressing Releases of PFAS, Q18 (DA, 

2018). 

Soil IDW (i.e., soil cuttings) generated during the SI activities were left in place at the point of the 

source. The soil cuttings were distributed on the downgradient side of the borehole. The IDW was

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

the source location. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 5-6

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

decontamination fluids) were discharged directly to the ground surface slightly downgradient of 

the source of generation in accordance with USEPA Management of IDW (USEPA, 2014). The 

IDW was not sampled and assumes the PFAS characteristics of the associated groundwater 

samples collected from the source location.

Geographic coordinates were collected using a global positioning system (GPS) around each 

location where IDW was placed (i.e., an IDW polygon). The IDW polygons are displayed on the 

figure in Appendix B5. 

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

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

activities were disposed of at a licensed solid waste landfill.

5.8 Laboratory Analytical Methods

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

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

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

5.9 Deviations from SI QAPP Addendum

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

documentation. The deviations are noted below and documented in Field Change Request Forms 

(Appendix B3): 

• While performing utility clearing at AOI 5, soil boring AOI05-04 was determined to be

inaccessible to vehicles. The access roads were blocked with immovable tree debris, large

track vehicle ruts, or otherwise abandoned. The new location for soil boring AOI05-04 was

proposed approximately 500 feet from soil boring AOI05-02 and approximately 2,000

feet from the location proposed in the QAPP. This area was vehicle-accessible, and the

proposed location was cleared of subsurface utilities by GPRS. During field locating and

clearing at soil boring AOI06-01, the location was approximately 70 feet from the intended

location - proximal to the infiltration basin culvert. The boring was moved to its intended

location and cleared of subsurface utilities by GPRS. This action was documented in a field

change request provided in Appendix B3.

• During the installation of a temporary well at soil boring AOI05-01, shallow refusal was

encountered at 13 feet bgs; however, groundwater was encountered and a temporary well

was installed. During the synoptic gauging, this well was dry. Three attempts were made to

drill an adjacent temporary well to increase the screen interval in the water bearing zone.

Two of the three attempts encountered refusal at 8 feet bgs, and the third hit refusal at 12

feet bgs. As such, an additional or replacement temporary well was not installed. During the

purging and sampling (after the synoptic gauging), the temporary well had an insufficient

water column to collect groundwater parameters and laboratory sample; the temporary well

was abandoned. This action was documented in a field change request provided in

Appendix B3.
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Sample Identification

Sample

Collection

Date/Time

Sample Depth

(feet bgs)

PFAS by LC/MS/MScompliant with QSM 5.3Table B-15TOC(USEPA Method 9060A)pH(USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

AOI01-01-SB-00-02 6/8/2022 9:05 00-02 x

AOI01-01-SB-06-08 6/8/2022 9:20 06-08 x

AOI01-01-SB-10.5-12.5 6/8/2022 9:30 10.5-12.5 x

AOI01-02-SB-00-02 6/8/2022 15:25 00-02 x

AOI01-02-SB-6.5-8.5 6/8/2022 15:35 6.5-8.5 x x x

AOI01-02-SB-6.5-8.5-D 6/8/2022 15:35 6.5-8.5 x x x Duplicate

AOI01-02-SB-11.3-13.3 6/8/2022 15:45 11.3-13.3 x

AOI01-03-SB-00-02 6/8/2022 7:45 00-02 x

AOI01-03-SB-00-02-MS 6/8/2022 7:45 00-02 x MS/MSD

AOI01-03-SB-00-02-MSD 6/8/2022 7:45 00-02 x MS/MSD

AOI01-03-SB-07-09 6/8/2022 7:55 07-09 x

AOI01-03-SB-15-17 6/8/2022 8:30 15-17 x

AOI01-03-SB-15-17-D 6/8/2022 8:30 15-17 x Duplicate

AOI02-01-SB-00-02 6/8/2022 12:00 00-02 x

AOI02-01-SB-04-06 6/8/2022 12:05 04-06 x

AOI02-01-SB-08-10 6/8/2022 12:15 08-10 x

AOI02-02-SB-00-02 6/8/2022 14:45 00-02 x

AOI02-02-SB-05-07 6/8/2022 14:55 05-07 x

AOI02-02-SB-10-12 6/8/2022 15:05 10-12 x

AOI02-03-SB-00-02 6/8/2022 10:55 00-02 x

AOI02-03-SB-03-05 6/8/2022 11:00 03-05 x x x

AOI02-03-SB-06-08 6/8/2022 11:10 06-08 x

AOI03-01-SB-00-02 6/9/2022 10:50 00-02 x

AOI03-01-6.3-8.3 6/9/2022 11:25 6.3-8.3 x

AOI03-01-6.3-8.3-MS 6/9/2022 11:25 6.3-8.3 x MS/MSD

AOI03-01-6.3-8.3-MSD 6/9/2022 11:25 6.3-8.3 x MS/MSD

AOI03-01-SB-15-17 6/9/2022 11:45 15-17 x

AOI03-02-SB-00-02 6/9/2022 9:00 00-02 x x x

AOI03-02-SB-05-07 6/9/2022 9:55 05-07 x

AOI03-02-SB-05-07-D 6/9/2022 9:55 05-07 x Duplicate

AOI03-02-SB-10-11.5 6/9/2022 10:00 10-11.5 x

AOI03-03-SB-00-02 6/9/2022 13:55 00-02 x

AOI03-03-SB-10-12 6/9/2022 14:10 10-12 x

AOI03-03-SB-15-16 6/9/2022 14:30 15-16 x

AOI04-01-SB-00-02 6/13/2022 10:40 00-02 x

AOI04-01-SB-03-05 6/13/2022 10:45 03-05 x

AOI04-01-SB-5.5-7.5 6/13/2022 10:50 5.5-7.5 x

AOI04-01-SB-5.5-7.5-D 6/13/2022 10:50 5.5-7.5 x Duplicate

AOI04-020SB-00-02 6/13/2022 11:40 00-02 x

AOI04-02-SB-07-09 6/13/2022 11:50 07-09 x

AOI04-02-SB-11.5-13.5 6/13/2022 12:00 11.5-13.5 x

AOI04-02-SB-11.5-13.5-MS 6/13/2022 12:00 11.5-13.5 x MS/MSD

AOI04-02-SB-11.5-13.5-MSD 6/13/2022 12:00 11.5-13.5 x MS/MSD

AOI04-03-SB-00-02 6/13/2022 10:15 00-02 x

AOI04-03-SB-03-05 6/13/2022 10:20 03-05 x

AOI04-03-SB-5.5-6.5 6/13/2022 10:25 5.5-6.5 x

AOI04-03-SB-5.5-6.5-D 6/13/2022 10:25 5.5-6.5 x Duplicate

AOI04-04-SB-01-03 6/13/2022 13:10 01-03 x

Soil Samples

AECOM 5-7
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Sample Identification

Sample

Collection

Date/Time

Sample Depth

(feet bgs)

PFAS by LC/MS/MScompliant with QSM 5.3Table B-15TOC(USEPA Method 9060A)pH(USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

AOI04-04-SB-03-05 6/13/2022 13:15 03-05 x

AOI04-04-SB-5.5-7.5 6/13/2022 13:20 5.5-7.5 x

AOI04-05-SB-00-02 6/11/2022 8:55 00-02 x

AOI04-05-SB-00-02-D 6/11/2022 8:55 00-02 x Duplicate

AOI04-05-SB-05-07 6/11/2022 9:05 05-07 x x x

AOI04-05-SB-10.5-12.5 6/11/2022 9:15 10.5-12.5 x

AOI04-05-SB-10.5-12.5-MS 6/11/2022 9:15 10.5-12.5 x MS/MSD

AOI04-05-SB-10.5-12.5-MSD 6/11/2022 9:15 10.5-12.5 x MS/MSD

AOI05-01-SB-00-02 6/14/2022 11:25 00-02 x

AOI05-01-SB-04-06 6/14/2022 11:40 04-06 x

AOI05-01-SB-08-10 6/14/2022 11:45 08-10 x

AOI05-02-SB-00-02 6/14/2022 13:15 00-02 x

AOI05-02-SB-03-05 6/14/2022 13:20 03-05 x

AOI05-02-SB-05-07 6/14/2022 13:25 05-07 x

AOI05-02-SB-07-09 6/15/2022 10:25 07-09 x

AOI05-03-SB-00-02 6/14/2022 10:10 00-02 x

AOI05-03-SB-00-02-D 6/14/2022 10:10 00-02 x Duplicate

AOI05-03-SB-03-05 6/14/2022 10:15 03-05 x

AOI05-04-SB-00-02 6/14/2022 14:40 00-02 x

AOI05-04-SB-03-05 6/14/2022 14:45 03-05 x

AOI05-05-SB-00-02 6/10/2022 9:00 00-02 x

AOI05-05-SB-02-04 6/10/2022 9:05 02-04 x

AOI05-06-SB-00-02 6/10/2022 9:45 00-02 x

AOI05-06-SB-05-07 6/10/2022 9:55 05-07 x

AOI05-06-SB-11-13 6/10/2022 10:05 11-13 x

AOI05-07-SB-00-02 6/10/2022 8:25 00-02 x

AOI05-08-SB-00-02 6/10/2022 8:10 00-02 x

AOI05-08-SB-00-02-D 6/10/2022 8:10 00-02 x Duplicate

AOI05-09-SB-00-02 6/10/2022 8:00 00-02 x x x

AOI06-01-SB-00-02 6/14/2022 7:45 00-02 x

AOI06-01-SB-03-05 6/14/2022 7:50 03-05 x

AOI06-02-SB-00-02 6/13/2022 16:45 00-02 x

AOI06-02-SB-03-05 6/13/2022 16:55 03-05 x

AOI06-03-SB-00-02 6/15/2022 15:55 00-02 x x x

AOI06-03-SB-03-05 6/15/2022 16:00 03-05 x

AOI06-03-SB-05-07 6/15/2022 16:05 05-07 x

AOI07-01-SB-00-02 6/10/2022 13:40 00-02 x

AOI07-01-SB-03-05 6/10/2022 13:45 03-05 x

AOI07-01-SB-06-08 6/10/2022 13:50 06-08 x

AOI07-02-SB-00-02 6/10/2022 12:00 00-02 x

AOI07-02-SB-00-02-D 6/10/2022 12:00 00-02 x Duplicate

AOI07-02-SB-05-07 6/10/2022 12:15 05-07 x x x

AOI07-02-SB-10-12 6/10/2022 12:25 10-12 x

AOI07-02-SB-10-12-MS 6/10/2022 12:25 10-12 x MS/MSD

AOI07-02-SB-10-12-MSD 6/10/2022 12:25 10-12 x MS/MSD

AOI07-03-SB-00-02 6/13/2022 14:25 00-02 x

AOI07-03-SB-06-08 6/13/2022 14:35 06-08 x

AOI07-03-SB-11-13 6/13/2022 14:40 11-13 x

AOI07-04-SB-00-02 6/10/2022 15:15 00-02 x

AECOM 5-8
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Sample Identification

Sample

Collection

Date/Time

Sample Depth

(feet bgs)

PFAS by LC/MS/MScompliant with QSM 5.3Table B-15TOC(USEPA Method 9060A)pH(USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

AOI07-04-SB-06-08 6/10/2022 15:30 06-08 x

AOI07-04-SB-15-17 6/10/2022 15:55 15-17 x

AOI08-01-SB-00-02 6/7/2022 9:05 00-02 x x x

AOI08-01-SB-00-02-MS 6/7/2022 9:05 00-02 x x MS/MSD

AOI08-01-SB-00-02-MSD 6/7/2022 9:05 00-02 x x MS/MSD

AOI08-01-SB-7.5-8.5 6/7/2022 9:15 7.5-8.5 x

AOI08-01-SB-15-16.5 6/7/2022 9:50 15-16.5 x

AOI08-02-SB-00-02 6/7/2022 11:35 00-02 x

AOI08-02-SB-00-02-D 6/7/2022 11:35 00-02 x Duplicate

AOI08-02-SB-05-07 6/7/2022 11:55 05-07 x

AOI08-02-SB-10-12 6/7/2022 12:05 10-12 x

AOI08-03-SB-00-02 6/7/2022 13:40 00-02 x

AOI08-03-SB-05-07 6/7/2022 13:50 05-07 x

AOI08-03-SB-11.5-12.5 6/7/2022 14:10 11.5-12.5 x

AECOM 5-9
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Sample Identification

Sample

Collection

Date/Time

Sample Depth

(feet bgs)

PFAS by LC/MS/MScompliant with QSM 5.3Table B-15TOC(USEPA Method 9060A)pH(USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

AOI01-01-GW 6/8/2022 15:08 NA x

AOI01-02-GW 6/7/2022 13:20 NA x

AOI01-03-GW 6/8/2022 16:34 NA x

AOI01-03-GW-D 6/8/2022 16:34 NA x Duplicate

AOI02-01-GW 6/9/2022 12:42 NA x

AOI02-01-GW-D 6/9/2022 12:42 NA x Duplicate

AOI02-01-GW-MS 6/9/2022 12:42 NA x MS/MSD

AOI02-01-GW-MSD 6/9/2022 12:42 NA x MS/MSD

AOI02-02-GW 6/9/2022 11:12 NA x

AOI02-03-GW 6/9/2022 9:58 NA x

AOI03-01-GW 6/10/2022 9:52 NA x

AOI03-02-GW 6/10/2022 8:40 NA x

AOI03-03-GW 6/10/2022 11:20 NA x

AOI04-01-GW 6/13/2022 13:12 NA x

AOI04-02-GW 6/14/2022 11:15 NA x

AOI04-03-GW 6/11/2022 14:30 NA x

AOI04-04-GW 6/14/2022 8:15 NA x

AOI04-05-GW 6/11/2022 12:42 NA x

AOI05-530012-GW 6/11/2022 9:22 NA x

AOI05-530012-GW-D 6/11/2022 9:22 NA x Duplicate

AOI05-482900-GW 6/13/2022 11:25 NA x

AOI05-02-GW 6/16/2022 11:15 NA x

AOI05-03-GW 6/15/2022 9:00 NA x

AOI05-04-GW 6/14/2022 16:25 NA x

AOI05-05-GW 6/10/2022 12:32 NA x

AOI05-06-GW 6/10/2022 13:45 NA x

AOI05-773250-GW 6/8/2022 11:50 NA x

AOI05-536846-GW 6/8/2022 9:20 NA x

AOI06-01-GW 6/14/2022 12:55 NA x

AOI06-02-GW 6/14/2022 14:56 NA x

AOI06-03-GW 6/14/2022 14:16 NA x

AOI07-01-GW 6/13/2022 9:55 NA x

AOI07-02-GW 6/10/2022 14:55 NA x

AOI07-02-GW-D 6/10/2022 14:55 NA x Duplicate

AOI07-02-GW-MS 6/10/2022 14:55 NA x MS/MSD

AOI07-02-GW-MSD 6/10/2022 14:55 NA x MS/MSD

AOI07-03-GW 6/14/2022 9:50 NA x

AOI07-04-GW 6/11/2022 11:28 NA x

AOI08-01-GW 6/7/2022 13:05 NA x

AOI08-02-GW 6/7/2022 14:15 NA x

AOI08-03-GW 6/7/2022 15:34 NA x

CR-FRB-01 6/7/2022 15:30 NA x FRB

CR-ERB-01 6/13/2022 16:00 NA x Hand Auger

CR-ERB-02 6/13/2022 16:30 NA x Drill Shoe

CR-ERB-03 6/14/2022 12:00 NA x Hand Auger

CR-ERB-04 6/14/2022 12:30 NA x Drill Shoe

CR-ERB-05 6/15/2022 12:00 NA x Drill Shoe

Quality Control Samples

Groundwater Samples

AECOM 5-10
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Sample Identification

Sample

Collection

Date/Time

Sample Depth

(feet bgs)

PFAS by LC/MS/MScompliant with QSM 5.3Table B-15TOC(USEPA Method 9060A)pH(USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

CR-DECON-01 1/12/2022 10:10 NA x

Decon Spigot

prior to SI

activities

Notes:

ASTM = American Society for Testing and Materials

bgs = below ground surface

ERB = equipment rinsate blank

FRB = field reagent blank

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

NA = not applicable

PFAS = per- and polyfluoroalkyl substances

QSM = Quality Systems Manual

SI = Site Investigation

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

AECOM 5-11
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 5-12

THIS PAGE INTENTIONALLY BLANK
Table 5-2

Soil Boring Depths, Temporary Well Screen Intervals, and Groundwater Elevations

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Area of

Interest

Boring

Location

Soil Boring

Depth

(feet bgs)

Temporary Well

Screen Interval

(feet bgs)

Top of Casing

Elevation

(feet NAVD88)

Ground Surface

Elevation

(feet NAVD88)

Depth to

Water1,2

(feet btoc)

Depth to

Water

(feet bgs)

Groundwater

Elevation

(feet NAVD88)

AOI01-01 20.00 15.00 - 20.00 1147.51 1147.15 18.38 18.01 1129.13

AOI01-02 20.00 15.00 - 20.00 1147.52 1147.26 19.00 18.74 1128.52

AOI01-03 22.00 17.00 - 22.00 1150.17 1146.95 21.47 18.25 1128.70

AOI02-01 15.00 8.00 - 15.00 1146.41 1145.19 11.76 10.55 1134.65

AOI02-02 17.00 12.00 - 17.00 1148.17 1144.75 15.94 12.52 1132.23

AOI02-03 15.00 8.00 - 15.00 1146.11 1145.73 11.76 11.38 1134.35

AOI03-01 22.00 17.00 - 22.00 1144.55 1141.73 20.29 17.47 1124.26

AOI03-02 20.00 15.00 - 20.00 1140.46 1140.17 16.01 15.72 1124.45

AOI03-03 21.00 16.00 - 21.00 1144.89 1140.78 20.79 16.67 1124.10

AOI04-01 15.00 10.00 - 15.00 1145.30 1145.02 10.70 10.42 1134.60

AOI04-02 20.00 15.00 - 20.00 1151.40 1151.11 17.04 16.75 1134.36

AOI04-03 15.00 10.00 - 15.00 1144.00 1142.60 9.52 8.12 1134.48

AOI04-04 15.00 10.00 - 15.00 1144.50 1144.17 10.77 10.44 1133.73

AOI04-05 20.00 15.00 - 20.00 1146.63 1146.30 16.14 15.81 1130.49

AOI05-01 15.00 5.00 - 15.00 1207.23 1206.65 14.64 14.06 1192.59

AOI05-02 14.00 5.00 - 14.00 1206.99 1206.10 DRY -- --

AOI05-02A3 23.00 13.00 - 23.00 1208.14 1206.10 24.42 22.38 1183.72

AOI05-03 10.00 5.00 - 10.00 1194.18 1193.71 4.14 3.67 1190.04

AOI05-04 10.00 5.00 - 10.00 1207.94 1205.01 7.28 4.34 1200.66

AOI05-05 9.00 4.00 - 9.00 1129.27 1128.88 8.65 8.26 1120.62

AOI05-06 20.00 15.00 - 20.00 1123.76 1122.39 14.27 12.90 1109.49

AOI06-01 10.00 5.00 - 10.00 1126.28 1126.00 5.91 5.64 1120.37

AOI06-02 10.00 5.00 - 10.00 1123.42 1123.09 3.37 3.04 1120.05

AOI06-03 12.00 5.00 - 12.00 1129.23 1125.62 9.48 5.87 1119.75

AOI07-01 15.00 10.00 - 15.00 1141.06 1140.79 11.96 11.69 1129.10

AOI07-02 17.00 12.00 - 17.00 1143.85 1140.73 16.57 13.45 1127.28

AOI07-03 20.00 15.00 - 20.00 1141.75 1141.46 15.60 15.31 1126.15

AOI07-04 22.00 17.00 - 22.00 1145.41 1142.53 20.77 17.89 1124.64

AOI08-01 25.00 15.00 - 25.00 1146.23 1145.80 19.32 18.88 1126.91

AOI08-02 20.00 15.00 - 20.00 1144.37 1144.17 17.88 17.68 1126.49

AOI08-03 20.00 15.00 - 20.00 1144.33 1144.02 17.48 17.17 1126.85

6

7

8

1

2

3

4

5

AECOM 5-13
Table 5-2

Soil Boring Depths, Temporary Well Screen Intervals, and Groundwater Elevations

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Notes:

1. Synoptic gauging event occurred on 15 June 2022.

2.

3.

bgs = below ground surface

btoc = below top of casing

NAVD88 = North American Vertical Datum 1988

Well AOI05-02A was installed after the synoptic gauging as an offset loction to AOI05-02 in an attempt to collect a groundwater sample. Depth to water

shown was measured on 16 June 2022.

Both AOI05-01 and AOI05-02 were dry during the synoptic gauging. As a result, these two locations were excluded from the groundwater contour map

(Figure 2-4). Depth to groundwater listed for AOI05-01 was measured on 16 June 2022, but is not shown on Figure 2-4 as it was not collected within 24

hours of the synoptic gauging event.

AECOM 5-14
Table 5-3

Permanent Monitoring Well Groundwater Elevations

Site Inspection Report, Camp Ripley, Little Falls, Minnesota

Area of

Interest Monitoring Well ID

Well Total Depth (ft

btoc)1

Screen Interval

(feet bgs)1

Top of Casing

Elevation

(feet NAVD88)

Ground Surface

Elevation (feet

NAVD88)

Depth to Water2

(feet btoc)

Depth to Water

(feet bgs)

Groundwater

Elevation

(feet NAVD88)

AOI05-482900 30.38 -- 1141.20 1139.59 19.13 17.52 1122.07

AOI05-530012 25.41 12-22 1144.18 1141.14 17.82 14.79 1126.36

AOI05-5368463 22.23 11-21 1221.77 1219.55 11.92 9.70 1209.85

AOI05-773250 40.27 26-36 1156.40 1153.50 27.74 24.85 1128.66

Notes:

1.

2. Synoptic gauging event occurred on 15 June 2022.

3.

bgs = below ground surface

btoc = below top of casing

NAVD88 = North American Vertical Datum 1988

5

Existing permanent well AOI05-536846 is located a significant distance from the AOIs and thus was not included in the groundwater contours.

Well screen interval data unavailable for existing permanent well AOI05-482900. Well screen interval was estimated using the depth of casing and depth of

borehole.

AECOM 5-15
AECOM 5-16

THIS PAGE INTENTIONALLY BLANK

M 5-16
­ Figure 5-1

Site Inspection Sample Locations

12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

5/17/2023

5/17/2023

5/17/2023

MS

EB

CM

GIS BY

CHK BY

PM

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

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

5/17/2023

1:28,800

Legend

&<

Existing Facility Well

!? Soil Boring Location

"S Surface Soil Sample

Area of Interest

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Surface Water Flow Direction

Groundwater Flow Direction

!?

!?

"S

"S

"S

Mississippi River

AOI 5

AOI05-05

AOI05-06

AOI05-07

AOI05-08

AOI05-09

!?

!?

!?

AOI 3 AOI03-01

AOI03-02

AOI03-03

!?

!?

!?

!?

!?

!?

!? !?

!?

!?

!?!?

!?

!?

!?

!?!?!?

!?!?

!?

!? !?

!?

!?

!?

!? !?

"S"S"S!?!?

&<

&<

&<

&<

Mis sissippi River

AOI 1

AOI 2

AOI 3

AOI 5

AOI 5

AOI 6

AOI 4

AOI 7

AOI 8

AOI01-01

AOI02-01

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI05-01

AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI04-05

AOI03-01

AOI03-02 AOI03-03

AOI06-01

AOI06-02

AOI06-03

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI08-01

AOI08-02

AOI08-03

AOI05-05

AOI05-06

AOI05-07

AOI05-08

AOI05-09

536846

773250

482900

530012

0 1,200 2,400 4,800

Feet

AECOM 5-17
THIS PAGE INTENTIONALLY BLANK 

5-18
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-1

6. Site Inspection Results

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

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

through Section 6.5. Table 6-2 through Table 6-5 present results in soil or groundwater for the

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

laboratory reports are provided in Appendix G. 

6.1 Screening Levels

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

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

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

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

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

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

Table 6-1 below.

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

Analyteb

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ Commercial 

Composite Worker

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater)

(ng/L)a

PFOA 19 250 6 

PFOS 13 160 4

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6 

Notes:

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

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

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

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

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

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

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

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

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

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

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

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

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

because 15 feet is the anticipated limit of construction activities. 

Soil sample depths shown in subsequent tables and figures are grouped into shallow, 

intermediate, and deep categories, which refer to the relative depth at which a sample was 

collected in a given borehole. As such, these categories are not intended to correspond to the 

exposure scenario depths specified above for the OSD SLs. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-2

6.2 Soil Physicochemical Analyses

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

and one soil sample was analyzed for grain size (AOI05-02-SB-07-09), which are important for 

evaluating transport through the soil medium. Appendix F contains the results of the TOC, pH, 

and grain size sampling. 

The TOC, pH, and grain size data collected in this investigation will be used in subsequent 

investigations, where appropriate, to assess fate and transport. According to the Interstate 

Technology Regulatory Council (ITRC), several important partitioning mechanisms include 

hydrophobic and lipophobic effects, electrostatic interactions, and interfacial behaviors. At 

relevant environmental pH values, certain PFAS are present as organic anions and are therefore 

relatively mobile in groundwater (Xiao et al., 2015), but tend to associate with the organic carbon 

fraction that may be present in soil or sediment (Higgins and Luthy, 2006; Guelfo and Higgins, 

2013). When sufficient organic carbon is present, organic carbon normalized distribution 

coefficients (Koc values) can help in evaluating transport potential, though other geochemical 

factors (for example, pH and presence of polyvalent cations) may also affect PFAS sorption to 

solid phases (ITRC, 2018).

6.3 AOI 1 

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

AOI 1: TriMaxTM Discharge Area and Building 8-197. The soil and groundwater results are 

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

Figure 6-1 through Figure 6-13. 

6.3.1 AOI 1 Soil Analytical Results

Figure 6-1, Figure 6-3, Figure 6-5, Figure 6-7, and Figure 6-9 present the ranges of detections 

in soil at AOI 1. Table 6-2 through Table 6-4 summarize the soil results. 

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

AOI01-03. Soil was also sampled from shallow subsurface soil (between 6 and 13.3 feet bgs) 

from boring locations AOI01-01 through AOI01-03, and deep subsurface soil intervals (15 to 17

feet bgs) from boring location AOI01-03. PFOA, PFHxS, and PFNA were detected in surface soil, 

with the maximum concentration of 0.232 micrograms per kilogram (μg/kg) observed at 

AOI01-02. PFOS was detected above the surface soil SL of 13 μg/kg at soil boring location AOI01-

02, with a concentration of 33.6 μg/kg. PFBS was not detected in surface soil at AOI 1.

PFHxS, PFOS, and PFNA were detected in shallow subsurface soil at concentrations below their 

respective SLs. PFHxS was detected at two of the three locations, with concentrations ranging 

from 0.039 J μg/kg to 0.126 J μg/kg. PFOS was detected in both shallow subsurface samples 

collected from AOI01-02, with a maximum concentration of 4.45 J μg/kg. PFNA was also detected 

at AOI01-02, with the highest concentration of 0.028 J μg/kg. PFOA and PFBS were not detected 

in shallow subsurface soil at AOI 1. There were no detections in deep subsurface soil.

6.3.2 AOI 1 Groundwater Analytical Results 

Figure 6-11 and Figure 6-13 present the ranges of detections in groundwater at AOI 1. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI01-01 through AOI01-03. The 

following exceedances of the SLs were measured:
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-3

• PFOS was detected above the SL of 4 nanograms per liter (ng/L) in AOI01-02 and 

AOI01-03, with concentrations of 1500 ng/L and 15.4 ng/L, respectively.

• PFOA was detected above the SL of 6 ng/L at AOI01-01 and AOI01-02, with 

concentrations of 6.16 ng/L to 56.0 ng/L, respectively.

• PFNA was detected above the SL of 6 ng/L at AOI01-02, with a concentration of 

34.9 ng/L.

• PFHxS was detected above the SL of 39 ng/L at AOI01-02, with a concentration of 

216 ng/L.

PFBS was detected below the SL of 601 ng/L in all three wells, with the maximum concentration 

of 10.8 ng/L observed at AOI01-02.

6.3.3 AOI 1 Conclusions

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

PFOS, PFNA, and PFHxS were detected in groundwater at concentrations above their SLs. 

Based on the exceedances of the SLs in soil and groundwater, further evaluation at AOI 1 is 

warranted.

6.4 AOI 2

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

AOI 2: Burn Pit Fire Training Area. The results in soil and groundwater are summarized on Table 

6-2 through Table 6-5. Soil and groundwater results are presented on Figure 6-1 through Figure 

6-13.

6.4.1 AOI 2 Soil Analytical Results

Figure 6-1, Figure 6-3, Figure 6-5, Figure 6-7, and Figure 6-9 present the ranges of detections 

in soil at AOI 2. Table 6-2 through Table 6-4 summarize the soil results.

Soil was sampled from surface soil (0 to 2 feet bgs) and shallow subsurface soil (between 4 and

12 feet bgs) at all three borings in AOI 2. In surface soil, PFOS and PFNA were detected below 

their SLs at all three locations, with a maximum concentration of 0.195 J μg/kg observed at AOI02-

03. PFHxS was detected below the SL at one location, AOI02-03, with a concentration of 0.041 J

μg/kg. PFOA and PFBS were not detected in surface soil. PFOA, PFOS, PFHxS, PFNA, and 

PFBS were not detected in shallow subsurface soil. No deep subsurface soil samples (>15 feet 

bgs) were collected at AOI 2.

6.4.2 AOI 2 Groundwater Analytical Results

Figure 6-11 and Figure 6-13 present the ranges of detections in groundwater at AOI 2. Table 6-5

summarizes the groundwater results.

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

PFOS were detected above their respective SLs at AOI02-01, with concentrations of 8.92 ng/L 

and 20.5 ng/L, respectively. PFBS and PFHxS were detected below their SLs, with a maximum 

concentration of 23.0 ng/L for PFHxS at AOI02-03, and a maximum of 0.972 J ng/L for PFBS at 

AOI02-02. PFNA was not detected in any of the wells.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-4

6.4.3 AOI 2 Conclusions

Based on the results of the SI, PFOS, PFHxS, and PFNA were detected below their respective 

SLs in soil at AOI 2. PFOA and PFOS were detected in groundwater at concentrations above their 

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

warranted.

6.5 AOI 3 

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

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

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

Figure 6-13. 

6.5.1 AOI 3 Soil Analytical Results

Figure 6-1, Figure 6-3, Figure 6-5, Figure 6-7, and Figure 6-9 present the ranges of detections 

in soil at AOI 3. Table 6-2 through Table 6-4 summarize the soil results. 

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI03-01 through 

AOI03-03. Soil was also sampled from shallow subsurface soil (between 5 and 12 feet bgs) from 

all boring locations, and deep subsurface soil (15-17 feet bgs) from AOI03-01 and AOI03-03. 

PFOA, PFOS, and PFNA were detected at concentrations below their SLs in surface soil, with a 

maximum concentration of 0.326 J μg/kg observed at AOI03-02 for PFOS. PFHxS and PFBS 

were not detected in surface soil. PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in 

either shallow or deep subsurface soil. 

6.5.2 AOI 3 Groundwater Analytical Results

Figure 6-11 and Figure 6-13 present the ranges of detections in groundwater at AOI 3. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI03-01, AOI03-02, and AOI03-03. 

PFOA, PFOS, and PFBS were detected below their SLs in groundwater:

• PFOA was detected below the SL of 6 ng/L in all three wells, with concentrations ranging

from 1.32 J ng/L to 3.76 J ng/L at AOI03-02.

• PFOS was detected below the SL of 4 ng/L at all three wells, with concentrations

ranging from 1.32 J ng/L to 2.80 J ng/L at AOI03-02.

• PFBS was detected below the SL of 601 ng/L at all three wells, with a concentration

ranging from 1.26 J ng/L to 1.48 J ng/L at AOI03-03.

PFHxS and PFNA were not detected in any of the wells. 

6.5.3 AOI 3 Conclusions

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

groundwater at concentrations below their SLs. Therefore, further evaluation at AOI 3 is not

warranted.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-5

6.6 AOI 4 

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

AOI 4: USPFO Warehouse, CMA Shop, and CMA Discharge Area. The results in soil and 

groundwater are presented in Table 6-2 through Table 6-5. Soil and groundwater results are 

presented on Figure 6-1 through Figure 6-13. 

6.6.1 AOI 4 Soil Analytical Results

Figure 6-2, Figure 6-4, Figure 6-6, Figure 6-8, and Figure 6-10 present the ranges of detections 

in soil at AOI 4. Table 6-2 through Table 6-4 summarize the soil results. 

Soil was sampled from surface soil (0 to 3 feet bgs) from boring locations AOI04-01 through 

AOI04-05. Soil was also sampled from shallow subsurface soil (between 3 and 13.5 feet bgs) 

from boring locations AOI04-01 through AOI04-05. Deep subsurface soil samples (>15 feet bgs) 

were not collected at AOI 4. 

PFBS was not detected in any surface soil samples. Detections of PFOA, PFOS, PFHxS, and

PFNA in surface soil were all below their SLs. Surface soil collected at AOI04-04 was non-detect 

for all relevant compounds; surface soil at this location was collected from 1 to 3 feet bgs due to 

concrete. PFOA was detected below the SL of 19 μg/kg at locations AOI04-01 and AOI04-03 with 

concentrations of 0.123 J μg/kg and 0.154 J μg/kg, respectively. PFOS was detected below the 

SL of 13 μg/kg in all locations except AOI04-04, with concentrations ranging from 0.587J μg/kg to 

1.79 μg/kg at AOI04-01. PFHxS was detected below the SL of 130 μg/kg at locations AOI04-01 

through AOI04-03, with concentrations ranging from 0.034 J μg/kg to 0.091 J μg/kg at AOI04-02. 

PFNA was detected below the SL of 19 μg/kg at all locations except AOI04-04, with concentrations 

ranging from 0.039 J μg/kg to 0.136 J μg/kg at AOI04-03.

PFOS, PFHxS, and PFNA were detected in shallow subsurface soil at concentrations below their 

SLs. PFOS was detected in three of the five locations, with concentrations ranging from 0.208 J+ 

μg/kg to 0.684 J μg/kg observed at AOI04-03. PFHxS was detected samples from AOI04-02, with 

concentrations of 0.054 J μg/kg and 0.066 J μg/kg observed at AOI04. PFNA was detected in 

samples from AOI04-03, with concentrations of 0.082 J μg/kg and 0.108 J μg/kg. PFOA and PFBS 

were not detected in shallow subsurface soil.

6.6.2 AOI 4 Groundwater Analytical Results

Figure 6-12 and Figure 6-13 present the ranges of detections in groundwater at AOI 4. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI04-01 through AOI04-05. The 

following detections and exceedances of the SLs were measured: 

• PFOA was detected above the SL of 6 ng/L in AOI04-03 and AOI04-04, with

concentrations of 6.79 ng/L and 15.0 ng/L, respectively.

• PFOS was detected above the SL of 4 ng/L in AOI04-03, AOI04-04, and AOI04-05, with

concentrations of 25.2 ng/L, 74.2 ng/L, and 17.6 ng/L, respectively.

• PFHxS was detected above the SL of 39 ng/L at AOI04-04, with a concentration of 132

ng/L.

• PFNA was detected above the SL of 6 ng/L at AOI04-03, with a concentration of 14.7

ng/L.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-6

PFBS was detected below the SL of 601 ng/L at three of the five wells, with a maximum

concentration of 6.56 ng/L. 

6.6.3 AOI 4 Conclusions

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

at concentrations exceeding their respective SLs. All detections in soil were below their SLs. 

Based on the exceedances observed in groundwater, further evaluation at AOI 4 is warranted.

6.7 AOI 5-WWTP 

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

AOI 5-WWTP. The results in soil and groundwater are presented in Table 6-2 through Table 6-5. 

Soil and groundwater results are presented on Figures 6-2, 6-4, 6-6, 6-8, 6-10, 6-12, and Figure 

6-13.

6.7.1 AOI 5-WWTP Soil Analytical Results

Figures 6-2, 6-4, 6-6, 6-8, and Figure 6-10 present the ranges of detections in soil at AOI 5-

WWTP. Table 6-2 through Table 6-4 summarize the soil results. 

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI05-05 through 

AOI05-09. Soil was also sampled from shallow subsurface soil (between 2 and 13 feet bgs) from 

boring locations AOI05-05 and AOI5-06. PFOA, PFOS, PFHxS, and PFNA were detected below 

their SLs in surface soil, with a maximum concentration of 1.29 μg/kg observed AOI05-05 for 

PFOS. PFBS was not detected in surface soil at AOI 5-WWTP. PFOS, PFHxS, and PFBS were 

detected in shallow subsurface soil at concentrations below the SLs, with the highest 

concentration of 0.222 J μg/kg observed at AOI05-06 (5 to 7 feet bgs) for PFOS. PFOA and PFNA 

were not detected in shallow subsurface soil samples. Deep subsurface soil (>15 feet bgs) was 

not sampled at the AOI 5-WWTP. 

6.7.2 AOI 5-WWTP and Existing Facility Wells Groundwater Analytical Results

Figure 6-12 and Figure 6-13 present the ranges of detections in groundwater at AOI 5-WWTP. 

Table 6-5 summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI05-05 and AOI05-06 at the 

WWTP. Exceedances of relevant compounds were observed at both wells. The following 

detections and exceedances of the SLs were measured: 

• PFOS was detected above the SL of 4 ng/L at both AOI05-05 and AOI05-06, with

concentrations of 21.2 ng/L and 62.4 ng/L, respectively.

• PFHxS was detected above the SL of 39 ng/L at AOI05-06, with a concentration of 43.0

ng/L. At AOI05-05, PFHxS was detected below the SL with a concentration of 11.7 ng/L.

PFOA was detected below the SL of 6 ng/L at AOI05-06 with a concentration of 5.24 ng/L. PFNA 

was detected below the SL of 6 ng/L at AOI05-06 with a concentration of 1.67 J ng/L. PFBS was 

detected below the SL of 601 ng/L at AOI05-05 and AOI05-06, with concentrations of 1.15 J ng/L 

and 3.11 J ng/L, respectively. PFOA and PFNA were not detected at AOI05-05.

Four existing facility monitoring wells, AOI05-482900, AOI05-530012, AOI05-536846, and AOI05-

773250, were also sampled during the SI. These wells were originally included as part of AOI 5 

to identify potential connection between AOI 5-WWTP and AOI 5-Sludge Spread Site, as well as 

any potential upgradient sources. However, upon further review as discussed in Section 5.4, 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-7

these wells will be described separately as they are not collocated with the AOI 5 potential release 

areas. The following detections and exceedances of SLs were measured at the facility wells:

• AOI05-482900: PFOS was detected below the SL of 4 ng/L at AOI05-482900 with a

concentration of 1.99 J ng/L; all other relevant compounds were non-detect.

• AOI05-530012: PFOS was detected above the SL with a concentration of 6.87 ng/L.

PFOA, PFHxS, and PFBS were detected below their respective SLs with concentrations

of 4.28 ng/L, 13.0 ng/L, and 0.980 J ng/L, respectively. PFNA was not detected.

• AOI05-773250: PFBS was detected below the SL of 601 ng/L with a concentration of

18.4 ng/L; all other relevant compounds were non-detect.

Groundwater from well AOI05-536846, which is upgradient of the cantonment area and AOI 5-

Sludge Spread Site, was non-detect for all relevant compounds.

6.7.3 AOI 5-WWTP Conclusions

Based on the results of the SI, PFOS and PFHxS were detected in groundwater at concentrations 

above their respective SLs at the AOI 5-WWTP. All detections in soil at AOI 5-WWTP were below 

their SLs. Based on the exceedances of the SLs in groundwater at the WWTP, further evaluation 

at AOI 5-WWTP is warranted. 

6.8 AOI 5-Sludge Spread Site

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

AOI 5-Sludge Spread Site. The results in soil and groundwater are presented in Table 6-2 through 

Table 6-5. Soil and groundwater results are presented on Figures 6-1, 6-3, 6-5, 6-7, 6-9, 6-11, 

and Figure 6-13. 

6.8.1 AOI 5-Sludge Spread Site Soil Analytical Results 

Figures 6-1, 6-3, 6-5, 6-7, and Figure 6-9 present the ranges of detections at soil at AOI 5-Sludge 

Spread Site. Table 6-2 through Table 6-4 summarize the soil results. 

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI05-01 through 

AOI05-04. Soil was also sampled from shallow subsurface soil (between 3 and 10 feet bgs) from 

boring locations AOI05-01 through AOI5-04. PFOA, PFOS, PFHxS, PFNA, and PFBS were 

detected below their SLs in surface soil, with a maximum concentration of 1.33 μg/kg observed 

at AOI05-02 for PFOS. PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in shallow 

subsurface soil at concentrations below their respective SLs, with a maximum concentration of

0.260 J μg/kg observed at AOI05-02 for PFOS. Deep subsurface soil (>15 feet bgs) was not 

sampled at AOI 5-Sludge Spread Site. 

6.8.2 AOI 5-Sludge Spread Site Groundwater Analytical Results 

Figure 6-11 and Figure 6-13 present the ranges of detections in groundwater at AOI 5-Sludge 

Spread Site. Table 6-5 summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI05-02 through AOI05-04 at the 

Sludge Spread Site. Results were non-detect for all relevant compounds at wells AOI05-02 and 

AOI05-03. In well AOI05-04, PFOS was detected below the SL of 4 ng/L with a concentration of 

0.956 J ng/L; all other relevant compounds were not detected at AOI05-04. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-8

6.8.3 AOI 5-Sludge Spread Site Conclusions

Based on the results of the SI, relevant compounds were detected in soil at concentrations below

their respective SLs at the AOI 5-Sludge Spread Site. PFOS was detected in one of three wells 

sampled, below the respective SL; the remaining results were non-detect. Based on the results 

of soil and groundwater at the Sludge Spread Site, no further evaluation at AOI 5-Sludge Spread 

Site is warranted.

6.9 AOI 6

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

AOI 6: Stormwater Infiltration Basin. The results in soil and groundwater are presented in Table 

6-2 through Table 6-5. Soil and groundwater results are presented on Figure 6-1 through 

Figure 6-13.

6.9.1 AOI 6 Soil Analytical Results

Figure 6-1, Figure 6-3, Figure 6-5, Figure 6-7, and Figure 6-9 present the ranges of detections 

in soil at AOI 6. Table 6-2 through Table 6-4 summarize the soil results.

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI06-01 through 

AOI06-03. Soil was also sampled from shallow subsurface soil (between 3 and 7 feet bgs) from

all boring locations. No deep subsurface soil samples (>15 feet bgs) were collected at AOI 6. 

Among the sampled locations, PFOA, PFOS, PFHxS, PFNA, and PFBS were detected below 

their respective SLs, with a maximum concentration of 0.256 J μg/kg observed at AOI06-02 for 

PFOS. 

PFOS was detected in shallow subsurface soil at boring location AOI06-03, with a concentration 

of 0.052 J μg/kg. PFOA, PFHxS, PFNA, and PFBS were not detected in shallow subsurface soil.

Deep subsurface soil was not sampled at AOI 6.

6.9.2 AOI 6 Groundwater Analytical Results

Figure 6-11 and Figure 6-13 present the ranges of detections in groundwater at AOI 6. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI06-01, AOI06-02, and AOI06-03.

PFOS was detected above the SL of 4 ng/L at all three wells, with concentrations of 13.8 ng/L, 

8.77 ng/L, and 4.71 ng/L.

PFOA, PFHxS, PFNA, and PFBS were detected below their SLs, with a maximum concentration 

of 2.69 J ng/L. 

6.9.3 AOI 6 Conclusions

Based on the results of the SI, PFOS was detected in groundwater above the SL. All detections 

in soil were below the SLs. Based on the exceedances of the SL in groundwater, further evaluation 

at AOI 6 is warranted.

6.10 AOI 7

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

AOI 7: Buildings 2-166, 2-203, 2-233, and 2-272. The results in soil and groundwater are 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-9

presented in Table 6-2 through Table 6-5. Soil and groundwater results are presented on Figure 

6-1 through Figure 6-13.

6.10.1 AOI 7 Soil Analytical Results

Figure 6-2, Figure 6-4, Figure 6-6, Figure 6-8, and Figure 6-10 present the ranges of detections 

in soil at AOI 7. Table 6-2 through Table 6-4 summarize the soil results. 

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI07-01 through 

AOI07-04. Soil was also sampled from shallow subsurface soil (between 3 and 13 feet bgs) from 

all boring locations, and deep subsurface soil (15 to 17 feet bgs) from boring location AOI07-04. 

PFOS, PFHxS, PFBS, PFOA, and PFNA were detected at concentrations below their SLs, with 

the highest concentration of 7.06 μg/kg observed at AOI07-02 for PFOS. 

PFOS, PFHxS, and PFBS were detected in shallow subsurface soil, at concentrations below their

SLs, with the maximum concentration of 18.1 μg/kg observed at AOI07-02 for PFOS. PFOA and 

PFNA were not detected in shallow subsurface soil. There were no detections in deep subsurface 

soil.

6.10.2 AOI 7 Groundwater Analytical Results

Figure 6-12 and Figure 6-13 present the ranges of detections in groundwater at AOI 7. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI07-01 through AOI07-04. The 

following exceedances of the SLs were measured: 

• PFOA was detected above the SL of 6 ng/L in AOI07-02, with a concentration of

6.20 ng/L.

• PFOS was detected above the SL of 4 ng/L at AOI07-01 through AOI07-03, with

concentrations ranging from 35.4 ng/L to 237 ng/L at location A0I07-01.

• PFHxS was detected above the SL of 39 ng/L at AOI07-01, with a concentration of

172 ng/L.

PFBS was detected below the SL of 601 ng/L in AOI07-01 through AOI07-03, with a maximum 

concentration of 14.2 ng/L at AOI07-01. PFNA was not detected in any of the wells.

6.10.3 AOI 7 Conclusions

Based on the results of the SI, PFOA, PFOS and PFHxS were detected in groundwater at 

concentrations above their respective SLs. All detections in soil were below their respective SLs. 

Based on the exceedances of the SLs in groundwater, further evaluation at AOI 7 is warranted.

6.11 AOI 8 

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

AOI 8: Building 8-195. The results in soil and groundwater are presented in Table 6-2 through 

Table 6-5. Soil and groundwater results are presented on Figure 6-1 through Figure 6-7. 

6.11.1 AOI 8 Soil Analytical Results

Figure 6-1, Figure 6-3, Figure 6-5, Figure 6-7, and Figure 6-9 present the ranges of detections 

in soil at AOI 8. Table 6-2 through Table 6-4 summarize the soil results. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 6-10

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI08-01 through 

AOI08-03. Soil was also sampled from shallow subsurface soil (between 5 and 12.5 feet bgs) 

from all boring locations, and deep subsurface soil (15 to 16.5 feet bgs) from AOI08-01. In surface 

soil, PFOS, PFHxS, and PFNA were detected at concentrations below their SLs, with a maximum 

concentration of 10.2 μg/kg observed at AOI08-01 for PFOS. PFBS and PFOA were not detected 

in surface soil. 

PFOA, PFOS, PFHxS, and PFNA were detected in shallow subsurface soil, at concentrations 

below the SLs. PFOA, PFHxS, and PFNA were detected below their SLs at AOI08-01, with a 

maximum concentration of 1.66 μg/kg for PFNA. PFOS was detected at AOI08-01 and AOI08-02 

with concentrations of 30.6 μg/kg and 0.287 J μg/kg, respectively. PFBS was not detected in 

shallow subsurface soil, and results for AOI08-03 were non-detect for all six analytes.

PFHxS was detected in deep subsurface soil at a concentration of 0.363 J μg/kg at AOI08-01. 

6.11.2 AOI 8 Groundwater Analytical Results

Figure 6-11 and Figure 6-13 present the ranges of detections in groundwater at AOI 8. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI08-01, AOI08-02, and AOI08-03. 

The following exceedances of the SLs were measured: 

• PFOA was detected above the SL of 6 ng/L in AOI08-01, with a concentration of 20.3

ng/L.

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

ranging from of 19.9 ng/L to 71.0 ng/L at location AOI08-02.

• PFHxS was detected above the SL of 39 ng/L in AOI08-01 with a concentration of 247

ng/L.

PFBS was detected below the SL of 601 ng/L at two of the three wells, with a maximum 

concentration of 5.71 ng/L. PFNA was not detected in any of the wells. 

6.11.3 AOI 8 Conclusions

Based on the results of the SI, PFOA, PFOS, and PFHxS were detected in groundwater at 

concentrations above their SLs. All detections in soil were below their SLs. Based on the 

exceedances of the SLs in groundwater, further evaluation at AOI 8 is warranted.
Table 6-2

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)PFBS 1900 ND U ND U ND U ND U ND UJ ND U ND U ND U ND PFHxS 130 0.045 J 0.123 J ND U ND U ND UJ 0.041 J ND U ND U ND PFNA 19 ND U 0.232 J 0.020 J 0.020 J 0.021 J 0.024 J 0.034 J 0.034 J ND PFOA 19 ND U 0.086 J ND U ND U ND UJ ND U 0.086 J ND U ND PFOS 13 0.272 J 33.6 0.318 J 0.070 J 0.060 J 0.195 J 0.237 J 0.326 J 0.056 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of InterestU = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

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

ft feetHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-00-02

06/08/2022

0-2 ft

AOI01-02-SB-00-02

06/07/2022

0-2 ft

AOI01-03-SB-00-02

06/08/2022

0-2 ft

AOI03-01-SB-00-02

06/09/2022

0-2 ft

AOI03-02-SB-00-02

06/09/2022

0-2 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI01 AOI02 AOI03

AOI03

0

AOI02-01-SB-00-02

06/08/2022

0-2 ft

AOI02-03-SB-00-02

06/08/2022

0-2 ft

AOI02-02-SB-00-02

06/08/2022

0-2 ft

AECOM 
Table 6-2

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)PFBS 1900 ND U ND U ND U ND U ND U 0.025 J 0.066 J ND U ND PFHxS 130 0.091 J 0.034 J ND U ND U ND U 0.066 J 0.084 J ND U ND PFNA 19 0.039 J 0.136 J ND U 0.114 J ND UJ 0.089 J 0.294 J 0.022 J 0.023 PFOA 19 ND U 0.154 J ND U ND U ND U 0.338 J 0.985 J ND U ND PFOS 13 0.604 J 1.30 ND U 0.587 J 0.082 J 0.843 J 1.33 0.074 J 0.076 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of InterestU = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

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

ft feetHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

Area of Interest

Sample ID

Sample Date

Depth

AOI04-03-SB-00-02

06/11/2022

0-2 ft

AOI04-02-SB-00-02

06/13/2022

0-2 ft

AOI04-04-SB-01-03

06/13/2022

1-3 ft

AOI04-05-SB-00-02

06/11/2022

0-2 ft

06/11/2022

0-2 ft

AOI05-01-SB-00-02

06/14/2022

0-2 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI04 AOI05

AOI05-

0

AOI05-02-SB-00-02

06/14/2022

0-2 ft

AOI05-03-SB-00-02

06/14/2022

0-2 ft

AOI04-05-SB-00-02-D

AECOM 
Table 6-2

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)PFBS 1900 ND U ND U ND U ND U ND U ND U ND U 0.180 J ND PFHxS 130 0.104 J ND U ND U ND U ND U ND U ND U 0.174 J ND PFNA 19 0.066 J ND U 0.131 J 0.049 J 0.042 J 0.021 J ND U 0.194 J 0.039 PFOA 19 0.161 J ND U ND U 0.135 J 0.125 J ND U ND U 0.220 J ND PFOS 13 1.29 0.242 J 1.00 J 0.395 J 0.355 J 0.302 J 0.069 J 0.256 J 0.118 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of InterestU = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

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

ft feetHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

06/10/2022

0-2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI05-06-SB-00-02

06/10/2022

0-2 ft

AOI05-05-SB-00-02

06/10/2022

0-2 ft

AOI06-01-SB-00-02

06/14/2022

0-2 ft

AOI06-02-SB-00-02

06/13/2022

0-2 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI05 AOI06

AOI06

0

AOI05-08-SB-00-02-D

06/10/2022

0-2 ft

AOI05-09-SB-00-02

06/10/2022

0-2 ft

AOI05-07-SB-00-02

06/10/2022

0-2 ft

AOI05-08-SB-00-02

AECOM 
Table 6-2

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

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

Soil, LCMSMS compliant with QSM 5.3 Table B-15 (μg/kg)PFBS 1900 0.045 J 0.053 J ND U ND U ND U ND U ND U ND UPFHxS 130 0.679 J 0.672 J 0.037 J ND U 0.219 J 0.135 J 0.038 J ND UPFNA 19 0.020 J 0.021 J 0.020 J ND U 0.032 J ND UJ 0.023 J ND UPFOA 19 0.093 J 0.099 J ND U ND U ND U ND U ND U ND UPFOS 13 6.79 7.06 0.068 J 0.054 J 10.2 0.197 J 0.582 J 0.112 J

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of InterestU = The analyte was not detected at a level greater than or equal to the adjusted DL D duplicate

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

ft feetHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

Area of Interest

Sample ID

Sample Date

Depth

AOI07-02-SB-00-02-D

06/10/2022

0-2 ft

06/07/2022

0-2 ft

AOI07-03-SB-00-02

06/13/2022

0-2 ft

AOI07-04-SB-00-02

06/10/2022

0-2 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

AOI07

06/07/2022

0-2 ft

AOI08-03-SB-00-02

AOI08

AOI07-02-SB-00-02

06/10/2022

0-2 ft

AOI08-02-SB-00-02-D

06/07/2022

0-2 ft

AOI08-01-SB-00-02

06/07/2022

0-2 ft

AOI08-02-SB-00-02

AECOM 
Table 6-3

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 25000 ND U ND U ND U ND U ND U ND U ND U ND U ND PFHxS 1600 0.039 J ND U 0.116 J 0.091 J 0.126 J ND U ND U ND U ND PFNA 250 ND U ND U 0.028 J 0.026 J 0.021 J ND U ND U ND U ND PFOA 250 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOS 160 ND U ND U 1.13 1.18 4.45 ND U ND U ND U ND 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityJ+ = Estimated concentration, biased high AOI Area of Interest

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

DL detection limit

Notes ft feet

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

ID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectiμg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI01 AOI02

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

AOI02-01-SB-08-10

06/08/2022

8-10 ft

AOI02

0

AOI01-03-SB-07-09

06/08/2022

7-9 ft

AOI02-01-SB-04-06

06/08/2022

4-6 ft

AOI01-02-SB-6.5-8.5-D

06/07/2022

6.5-8.5 ft

AOI01-02-SB-11.3-13.3

06/07/2022

11.3-13.3 ft

AOI01-01-SB-10.5-12.5

06/08/2022

10.5-12.5 ft

AOI01-02-SB-6.5-8.5

06/07/2022

6.5-8.5 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-06-08

06/08/2022

6-8 ft

AECOM 
Table 6-3

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 25000 ND U ND U ND U ND U ND U ND U ND U ND U ND PFHxS 1600 ND U ND U ND U ND U ND U ND U ND U ND U ND PFNA 250 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOA 250 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOS 160 ND U ND U ND U ND U ND U ND U ND U 0.208 J+ ND 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityJ+ = Estimated concentration, biased high AOI Area of Interest

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

DL detection limit

Notes ft feet

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

ID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectiμg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI02 AOI03 

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

AOI04-01-SB-03-05

06/13/2022

3-5 ft

AOI04

0

AOI03-02-SB-10-11.5

06/09/2022

10-11.5 ft

AOI03-03-SB-10-12

06/09/2022

10-12 ft

AOI03-02-SB-05-07

06/09/2022

5-7 ft

AOI03-02-SB-05-07-D

06/09/2022

5-7 ft

AOI02-03-SB-06-08

06/08/2022

6-8 ft

AOI03-01-6.3-8.3

06/09/2022

6.3-8.3 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI02-03-SB-03-05

06/08/2022

3-5 ft

AECOM 
Table 6-3

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 25000 ND U ND U ND U ND U ND U ND U ND U ND U ND PFHxS 1600 0.066 J 0.054 J ND U ND U ND U ND U ND U ND U ND PFNA 250 ND U ND U 0.088 J 0.082 J 0.108 J ND U ND U ND U ND PFOA 250 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOS 160 ND U ND U 0.684 J 0.421 J 0.517 J ND U ND U ND U ND 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityJ+ = Estimated concentration, biased high AOI Area of Interest

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

DL detection limit

Notes ft feet

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

ID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectiμg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI04 

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

AOI04-05-SB-05-07

06/11/2022

5-7 ft

AOI04-0

0

1

AOI04-04-SB-03-05

06/13/2022

3-5 ft

AOI04-04-SB-5.5-7.5

06/13/2022

5.5-7.5 ft

AOI04-03-SB-5.5-6.5

06/11/2022

5.5-6.5 ft

AOI04-03-SB-5.5-6.5-D

06/11/2022

5.5-6.5 ft

AOI04-02-SB-11.5-13.5

06/13/2022

11.5-13.5 ft

AOI04-03-SB-03-05

06/11/2022

3-5 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI04-02-SB-07-09

06/13/2022

7-9 ft

AECOM 
Table 6-3

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 25000 ND U ND U ND U ND U ND U ND U ND U 0.073 J ND PFHxS 1600 ND U ND U ND U ND U ND U 0.036 J ND U 0.043 J ND PFNA 250 ND U 0.051 J ND U ND U ND U ND U ND U ND U ND PFOA 250 ND U 0.167 J ND U ND U ND U ND U ND U ND U ND PFOS 160 0.088 J 0.260 J ND U 0.055 J ND U 0.131 J 0.222 J ND U ND 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityJ+ = Estimated concentration, biased high AOI Area of Interest

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

DL detection limit

Notes ft feet

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

ID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectiμg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI05 

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

AOI05-06-SB-11-13

06/10/2022

11-13 ft

AOI06

0

AOI05-05-SB-02-04

06/10/2022

2-4 ft

AOI05-06-SB-05-07

06/10/2022

5-7 ft

AOI05-03-SB-03-05

06/14/2022

3-5 ft

AOI05-04-SB-03-05

06/14/2022

3-5 ft

AOI05-02-SB-03-05

06/14/2022

3-5 ft

AOI05-02-SB-05-07

06/14/2022

5-7 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI05-01-SB-08-10

06/14/2022

8-10 ft

AECOM 
Table 6-3

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 25000 ND U ND U ND U ND U 0.023 J ND U ND U ND U ND PFHxS 1600 ND U ND U 0.051 J 0.126 J 0.926 J 0.149 J ND U ND U ND PFNA 250 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOA 250 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOS 160 0.052 J ND U ND U ND U 18.1 0.785 J ND U ND U ND 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityJ+ = Estimated concentration, biased high AOI Area of Interest

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

DL detection limit

Notes ft feet

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

ID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectiμg/kg micrograms per kilogram

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI06 AOI07 

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

AOI07-03-SB-11-13

06/13/2022

11-13 ft

AOI07

0

AOI07-02-SB-10-12

06/10/2022

10-12 ft

AOI07-03-SB-06-08

06/13/2022

6-8 ft

AOI07-01-SB-06-08

06/10/2022

6-8 ft

AOI07-02-SB-05-07

06/10/2022

5-7 ft

AOI06-03-SB-05-07

06/13/2022

5-7 ft

AOI07-01-SB-03-05

06/10/2022

3-5 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI06-03-SB-03-05

06/13/2022

3-5 ft

AECOM 
Table 6-3

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual

PFBS 25000 ND U ND U ND U ND UPFHxS 1600 ND U ND U ND U ND UPFNA 250 ND U ND U ND U ND UPFOA 250 ND U ND U ND U ND UPFOS 160 0.287 J ND U ND U ND U

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityJ+ = Estimated concentration, biased high AOI Area of Interest

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

DL detection limit

Notes ft feet

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

ID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectiμg/kg micrograms per kilogram

Sample ID

Sample Date

Depth

AOI08-02-SB-05-07

06/07/2022

5-7 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI08

AOI08-03-SB-11.5-12.5

06/07/2022

11.5-12.5 ft

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

AOI08-02-SB-10-12

06/07/2022

10-12 ft

AOI08-03-SB-05-07

06/07/2022

5-7 ft

Area of Interest

AECOM 
Table 6-4

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

Site Inspection Report, Camp Ripley

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS ND U ND U ND U ND U ND U ND UPFHxS ND U ND U ND U ND U ND U 0.363 JPFNA ND U ND U ND U ND U ND U ND UPFOA ND U ND U ND U ND U ND U ND UPFOS ND U ND U ND U ND U ND U ND U

Interpreted Qualifiers Chemical AbbreviationsJ = Estimated concentration PFBS perfluorobutanesulfonic acidU = The analyte was not detected at a level greater than or equal to the adjusted DL PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acidAcronyms and Abbreviations

AOI Area of InterestD duplicateDL detection limitft feetID identificationLCMSMS liquid chromatography with tandem mass LOD limit of detectionND analyte not detected above the LODQSM Quality Systems ManualQual interpreted qualifierSB soil boringμg/kg micrograms per kilogram

15-16 ft

AOI01-03-SB-15-17

06/08/2022

15-17 ft

AOI01-03-SB-15-17-D

06/08/2022

15-17 ft

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

AOI01 AOI03 AOI07

AOI07-04-SB-15-17

06/10/2022

15-17 ft

AOI08

AOI08-01-SB-15-16.5

06/07/2022

15-16.5 ft

AOI03-01-SB-15-17

06/09/2022

15-17 ft

AOI03-03-SB-15-16

06/09/2022

AECOM 
Table 6-5

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 601 2.11 J 10.8 ND UJ 0.691 J 0.872 J ND UJ 0.972 J ND U 1.36 PFHxS 39 12.1 216 ND U ND U 10.9 9.72 ND U 23.0 ND PFNA 6 ND U 34.9 ND U ND U ND U ND U ND U ND U ND 

PFOA 6 6.16 56.0 ND U ND U 8.92 7.95 ND U ND U 2.13 PFOS 4 3.57 J 1500 15.4 15.0 20.5 17.9 3.81 J 0.921 J 1.64 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

D duplicate

Notes DL detection limit

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

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protecting/l nanogram per liter

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI01 AOI02

AOI02-03-GW

06/09/2022

AO

0

AOI02-01-GW-D

06/09/2022

AOI02-02-GW

06/09/2022

AOI01-03-GW-D

06/08/2022

AOI02-01-GW

06/09/2022

AOI01-02-GW

06/07/2022

AOI01-03-GW

06/08/2022

Area of Interest

Sample ID

Sample Date

AOI01-01-GW

06/08/2022

AECOM 
Table 6-5

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 601 1.26 J 1.48 J 0.667 J 4.81 ND U 6.56 ND U ND U 0.980 PFHxS 39 ND U ND U 4.50 9.15 2.34 J 132 1.86 J ND U 13.0PFNA 6 ND U ND U ND U ND U 14.7 ND U ND U ND U ND 

PFOA 6 3.76 J 1.32 J ND U ND U 6.79 15.0 ND U ND U 4.28PFOS 4 2.80 J 1.32 J 3.08 J 1.95 J 25.2 74.2 17.6 1.99 J 6.87

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

D duplicate

Notes DL detection limit

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

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protecting/l nanogram per liter

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI03 AOI04 AOI05

AOI05-482900-GW

06/13/2022

AOI0

0

AOI04-04-GW

06/14/2022

AOI04-05-GW

06/11/2022

AOI04-02-GW

06/14/2022

AOI04-03-GW

06/11/2022

AOI03-03-GW

06/10/2022

AOI04-01-GW

06/13/2022

Area of Interest

Sample ID

Sample Date

AOI03-02-GW

06/10/2022

AECOM 
Table 6-5

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 601 0.652 J ND U 18.4 ND U ND U ND U 1.15 J 3.11 J 0.735 

PFHxS 39 9.68 ND U ND U ND U ND U ND U 11.7 43.0 2.37 

PFNA 6 ND U ND U ND U ND U ND U ND U ND U 1.67 J 1.06 PFOA 6 3.43 J ND U ND U ND U ND U ND U ND U 5.24 1.59 PFOS 4 5.49 ND U ND U ND U ND U 0.956 J 21.2 62.4 13.8

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

D duplicate

Notes DL detection limit

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

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protecting/l nanogram per liter

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI05

AOI05-06-GW

06/10/2022

AO

0

AOI05-04-GW

06/14/2022

AOI05-05-GW

06/10/2022

AOI05-02-GW

06/16/2022

AOI05-03-GW

06/15/2022

AOI05-536846-GW

06/08/2022

AOI05-773250-GW

06/08/2022

Area of Interest

Sample ID

Sample Date

AOI05-530012-GW-D

06/11/2022

AECOM 
Table 6-5

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 601 0.655 J 0.817 J 14.2 0.707 J 0.930 J 1.74 J ND U 5.71 0.785 

PFHxS 39 2.69 J 1.81 J 172 17.9 19.6 2.69 J 1.87 J 247 4.26PFNA 6 ND U ND U ND U ND U ND U ND U ND U ND U ND PFOA 6 ND U 0.935 J 5.04 5.39 6.20 4.96 ND U 20.3 2.28 

PFOS 4 8.77 4.71 237 93.7 107 35.4 1.26 J 34.6 71.0

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

D duplicate

Notes DL detection limit

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

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protecting/l nanogram per liter

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI06 AOI07 AOI08

AOI08-01-GW

06/07/2022

AO

0

AOI07-03-GW

06/14/2022

AOI07-04-GW

06/11/2022

AOI07-02-GW

06/10/2022

AOI07-02-GW-D

06/10/2022

AOI06-03-GW

06/14/2022

AOI07-01-GW

06/13/2022

Area of Interest

Sample ID

Sample Date

AOI06-02-GW

06/14/2022

AECOM 
Table 6-5

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

Site Inspection Report, Camp Ripley

Analyte OSD Screening 

Level a

Result Qual

PFBS 601 ND UPFHxS 39 2.28 JPFNA 6 ND UPFOA 6 1.84 JPFOS 4 19.9

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

D duplicate

Notes DL detection limit

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

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protecting/l nanogram per liter

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

Area of Interest

Sample ID

Sample Date

AOI08

AOI08-03-GW

06/07/2022

AECOM 
Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-1

PFOA Detections in Soil, 

AOI 1, AOI 2, AOI 3, AOI 5, AOI 6 and AOI 8

2/15/2023

2/15/2023

MS 2/15/2023

AB

CM

GIS BY

CHK BY

PM

2/15/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:20,400

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-03

AOI08-01

AOI08-02

AOI08-03

0 850 1,700 3,400

­

Feet

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

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

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

Legend

Facility Boundary

Water Body

River/Stream

Shallow

Intermediate

Deep

AECOM 6-27
Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06 AOI05-07

AOI05-08

AOI05-09

Legend

Facility Boundary

Water Body

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-2

PFOA Detections in Soil, 

AOI 4, AOI 5, AOI 7

11/21/2022

11/21/2022

MS 11/21/2022

AB

CM

GIS BY

CHK BY

PM

11/21/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:12,240

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-06

0 510 1,020 2,040

­

Feet

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

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

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

Mississippi Rive

AOI05-05 r

AOI05-06 AOI05-07

AOI05-08

AOI05-09

Shallow

Intermediate

Deep

AECOM 6-28
Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01

AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-3

PFOS Detections in Soil, 

AOI 1, AOI 2, AOI 3, AOI 5, AOI 6 and AOI 8

2/15/2023

2/15/2023

MS 2/15/2023

AB

CM

GIS BY

CHK BY

PM

2/15/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:20,400

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-03

AOI08-01

AOI08-02

AOI08-03

0 850 1,700 3,400

­

Feet

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

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

Legend

Facility Boundary

Water Body

River/Stream

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

Shallow

Intermediate

Deep

AECOM 6-29
Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06 AOI05-07

AOI05-08

AOI05-09

Legend

Facility Boundary

Water Body

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-4

PFOS Detections in Soil, 

AOI 4, AOI 5, AOI 7

11/21/2022

11/21/2022

MS 11/21/2022

AB

CM

GIS BY

CHK BY

PM

11/21/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:12,240

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-06

0 510 1,020 2,040

­

Feet

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

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

Mississippi River

AOI05-05

AOI05-06 AOI05-07

AOI05-08

AOI05-09

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

Shallow

Intermediate

Deep

AECOM 6-30
Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-5

PFBS Detections in Soil, 

AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, and AOI 8

2/15/2023

2/15/2023

MS 2/15/2023

AB

CM

GIS BY

CHK BY

PM

2/15/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:20,400

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-03

AOI08-01

AOI08-02

AOI08-03

0 850 1,700 3,400

­

Feet

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

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

Legend

Facility Boundary

Water Body

River/Stream

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

Shallow

Intermediate

Deep

AECOM 6-31
Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06 AOI05-07

AOI05-08

AOI05-09

Legend

Facility Boundary

Water Body

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-6

PFBS Detections in Soil, 

AOI 4, AOI 5, AOI 7

11/21/2022

11/21/2022

MS 11/21/2022

AB

CM

GIS BY

CHK BY

PM

11/21/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:12,240

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-06

0 510 1,020 2,040

­

Feet

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

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

Mississippi Rive

AOI05-05 r

AOI05-06 AOI05-07

AOI05-08

AOI05-09

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

Shallow

Intermediate

Deep

AECOM 6-32
Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-7

PFHxS Detections in Soil, 

AOI 1, AOI 2, AOI 3, AOI 5, AOI 6 and AOI 8

2/15/2023

2/15/2023

MS 2/15/2023

AB

CM

GIS BY

CHK BY

PM

2/15/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:20,400

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-03

AOI08-01

AOI08-02

AOI08-03

0 850 1,700 3,400

­

Feet

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

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

Legend

Facility Boundary

Water Body

River/Stream

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

Shallow

Intermediate

Deep

AECOM 6-33
Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06 AOI05-07

AOI05-08

AOI05-09

Legend

Facility Boundary

Water Body

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-8

PFHxS Detections in Soil, 

AOI 4, AOI 5, AOI 7

11/21/2022

11/21/2022

MS 11/21/2022

AB

CM

GIS BY

CHK BY

PM

11/21/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:12,240

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-06

0 510 1,020 2,040

­

Feet

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

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

Mississippi Rive

AOI05-05 r

AOI05-06 AOI05-07

AOI05-08

AOI05-09

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

Shallow

Intermediate

Deep

AECOM 6-34
Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01

AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-9

PFNA Detections in Soil, 

AOI 1, AOI 2, AOI 3, AOI 5, AOI 6 and AOI 8

2/15/2023

2/15/2023

MS 2/15/2023

AB

CM

GIS BY

CHK BY

PM

2/15/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:20,400

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

Mississippi River

AOI01-01

AOI02-01

AOI05-01 AOI05-02

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01 AOI03-02

AOI03-03

AOI06-03

AOI08-01

AOI08-02

AOI08-03

0 850 1,700 3,400

­

Feet

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

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

Legend

Facility Boundary

Water Body

River/Stream

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

Shallow

Intermediate

Deep

AECOM 6-35
Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06 AOI05-07

AOI05-08

AOI05-09

Legend

Facility Boundary

Water Body

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-10

PFNA Detections in Soil, 

AOI 4, AOI 5, AOI 7

11/21/2022

11/21/2022

MS 11/21/2022

AB

CM

GIS BY

CHK BY

PM

11/21/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:12,240

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-06

0 510 1,020 2,040

­

Feet

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

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

Mississippi Rive

AOI05-05 r

AOI05-06 AOI05-07

AOI05-08

AOI05-09

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

Shallow

Intermediate

Deep

AECOM 6-36
AOI01-01

AOI02-01

AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-02 AOI03-01

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

773250

Mississippi River

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-11

PFOA, PFOS, and PFBS Detections in Groundwater, 

AOI 1, AOI 2, AOI 3, AOI 5, AOI 6, and AOI 8

1/12/2023

1/12/2023

MS 1/12/2023

AB

CM

GIS BY

CHK BY

PM

1/12/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:20,400

AOI01-01

AOI02-01

AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01

AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

773250

Mississippi River

AOI01-01

AOI02-01

AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI03-01

AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI08-01

AOI08-02

AOI08-03

773250

Mississippi River

0 850 1,700 3,400

­

Feet

Groundwater was not collected from AOI05-01.

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

Legend

Facility Boundary

Water Body

River/Stream

Groundwater Elevation Contour

Inferred Groundwater Elevation Contour

Groundwater Flow Direction

PFOA

PFOS

PFBS

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

PFOS Results (ng/L)

ND

>ND - 4

>4 - 40

>40 - 70

>70

PFBS Results (ng/L)

ND

>ND - 100

>100 - 601

>601 - 2,000

>2,000

536846 is 3 mi to NW, PFOA Result: ND

536846 is 3 mi to NW, PFOS Result: ND

536846 is 3 mi to NW, PFBS Result: ND

AECOM 6-37
AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

482900

530012

Mississippi River

Legend

Facility Boundary

Water Body

River/Stream

Groundwater Flow Direction

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-12

PFOA, PFOS, and PFBS Detections in 

Groundwater, AOI 4, AOI 5, AOI 7

1/12/2023

1/12/2023

MS 1/12/2023

AB

CM

GIS BY

CHK BY

PM

1/12/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:13,200

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02 AOI07-03

AOI07-04

AOI05-05

AOI05-06

482900

530012

Mississippi River

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI04-05

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI05-05

AOI05-06

482900

530012

Mississippi River

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

PFOA

PFOS

PFBS

PFBS Results (ng/L)

ND

>ND - 100

>100 - 601

>601 - 2,000

>2,000

PFOS Results (ng/L)

ND

>ND - 4

>4 - 40

>40 - 70

>70

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

0 550 1,100 2,200

­

Feet

536846 is 4 mi to NW, PFOS Result: ND

536846 is 4 mi to NW, PFOA Result: ND

536846 is 4 mi to NW, PFBS Result: ND

AECOM 6-38
AOI01-01

AOI02-01

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI04-05

AOI03-01

AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI08-01

AOI08-02

AOI08-03

AOI05-05

AOI05-06

536846

773250

482900

530012

Mississippi River

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-13

PFHxS and PFNA Detections

 in Groundwater

12/8/2022

12/8/2022

MS 12/8/2022

AB

CM

GIS BY

CHK BY

PM

12/8/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Camp Ripley, MN

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

the GIS User Community

1:34,800

AOI01-01

AOI02-01

AOI04-01

AOI04-02

AOI04-03

AOI04-04

AOI05-02

AOI05-03

AOI05-04

AOI02-02

AOI02-03

AOI01-02

AOI01-03

AOI04-05

AOI03-01

AOI03-02

AOI03-03

AOI06-01 AOI06-02

AOI06-03

AOI07-01

AOI07-02

AOI07-03

AOI07-04

AOI08-01

AOI08-02

AOI08-03

AOI05-05

AOI05-06

536846

773250

482900

530012

Mississippi River

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

Legend

Facility Boundary

Water Body

River/Stream

Canal/Ditch

Groundwater Flow Direction

PFHxS

PFNA

PFNA Results (ng/L)

ND

>ND - 6

>6 - 100

>100 - 1,000

>1,000

PFHxS Results (ng/L)

ND

>ND - 39

>39 - 100

>100 - 1,000

>1,000

0 1,450 2,900 5,800

­

Feet

AECOM 6-39
THIS PAGE INTENTIONALLY BLANK

nspection Report

 Ripley, Little Falls, Minnesota
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

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 7-8. Please note that while the CSM discussion assists in determining if a receptor may 

be impacted, the decision to move from SI to RI is determined based upon exceedances of the 

SLs for the relevant compounds and whether the release is more than likely attributable to the 

DoD. A CSM presents the current understanding of the facility conditions with respect to known 

and suspected sources, potential transport mechanisms and migration pathways, and potentially 

exposed human receptors. A human exposure pathway is considered potentially complete when 

the following conditions are present:

1. Contaminant source;

2. Environmental fate and transport;

3. Exposure point;

4. Exposure route; and

5. Potentially exposed populations.

If any of these elements are missing, the pathway is incomplete. The CSM figures use an empty 

circle symbol to represent an incomplete exposure pathway. Areas with an incomplete pathway 

generally warrant no further action. However, the pathway is considered potentially complete if the 

relevant compounds are detected, in which case the CSM figure uses a half-filled circle symbol to 

represent a potentially complete exposure pathway. Additionally, a completely filled circle symbol is 

used to indicate when a potentially complete exposure pathway has detections of relevant 

compounds above the SLs. Areas with an identified potentially complete pathway that have 

detections of the relevant compounds above the SLs may warrant further investigation. Although 

the CSMs indicate whether potentially complete exposure pathways may exist, the 

recommendation for future study in an RI or no action at this time is based on the comparison of 

the SI analytical results for the relevant compounds to the SLs.

In general, the potential routes of exposure to the relevant compounds are ingestion and 

inhalation. Human exposure via the dermal contact pathway may occur, and current risk practice 

suggests it is an insignificant pathway compared to ingestion; however, exposure data for dermal 

pathways are sparse and continue to be the subject of toxicological study. The receptors 

evaluated are consistent with those listed in USEPA guidance for risk screening (USEPA, 2001). 

Receptors at the facility include site workers (e.g., facility staff and visiting soldiers), construction 

workers, trespassers (although unlikely due to restricted access), on-facility residents inside the 

cantonment area, off-facility residents outside the facility boundary, and recreational users outside 

of the facility boundary. 

7.1 Soil Exposure Pathway

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

between the source and potential receptors at AOI 1 through AOI 8 based on the aforementioned 

criteria. 

7.1.1 AOI 1 

AOI 1 is the TriMaxTM Discharge Area and Building 8-197, where potential PFAS releases to soil 

by the MNARNG occurred once in the early 2000s and where three firetrucks and three all-terrain 

vehicles, all with AFFF capabilities, were stored. PFAS were potentially released to soil and 

groundwater from AOI 1 through previous fire training exercises and/or firetruck storage.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-2

PFOA, PFOS, PFHxS, and PFNA were detected in surface soil at AOI 1. Of these, PFOS 

exceeded the SL. Site workers, construction workers, on- and off-facility residents, and 

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

dust. No active construction was observed to be occurring near AOI 1 at the time of the SI. 

Therefore, the surface soil exposure pathway for site workers, on- and off-facility residents, future 

construction workers, and trespassers are potentially complete with exceedances. PFHxS, PFNA,

and PFOS were detected in subsurface soil at AOI 1. Construction workers could contact 

constituents in subsurface soil via incidental ingestion; therefore, the subsurface soil exposure 

pathway for future construction workers is potentially complete. The CSM for AOI 1 is presented 

on Figure 7-1. 

7.1.2 AOI 2 

AOI 2 is the Burn Pit Fire Training Area, where a single coordinated fire training event occurred in 

the late 1980s. The burn pit may have also been used for coordinated fire training exercises; 

however, additional uses were not confirmed during the PA process. 

PFOS, PFHxS, and PFNA were detected in surface soil at AOI 2. Site workers, construction 

workers, on- and off-facility residents, and trespassers could contact constituents in surface soil 

via incidental ingestion and inhalation of dust. No active construction was observed to be 

occurring near AOI 2 at the time of the SI. Therefore, the surface soil exposure pathway for site 

workers, future construction workers, on- and off-facility residents, and trespassers are 

considered potentially complete. PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in 

subsurface soil at AOI 2; therefore, all subsurface soil exposure pathways are considered 

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

7.1.3 AOI 3 

AOI 3 is the DHS Demonstration at the EMTC. A coordinated fire training event occurred in 

November 2014 at the EMTC between DHS, MNARNG, and local municipalities. Potential PFAS 

was released to soil and groundwater from AOI 3 through previous fire training exercises and/or 

firetruck storage.

PFOA, PFOS, and PFNA were detected below their respective SLs in surface soil at AOI 3. Site 

workers, construction workers, on- and off-facility residents, and trespassers could contact 

constituents in surface soil via incidental ingestion and inhalation of dust. At the time of the SI, 

construction activities were occurring approximately 700 feet away from AOI 3. Therefore, the 

surface soil exposure pathway for site workers, current and future construction workers, on- and 

off-facility residents, and trespassers are potentially complete. PFOA, PFOS, PFHxS, PFNA, and 

PFBS were not detected in subsurface soil at AOI 3; therefore, all subsurface soil exposure 

pathways are considered incomplete. The CSM for AOI 3 is presented on Figure 7-3. 

7.1.4 AOI 4 

AOI 4 consists of the USPFO Warehouse, CMA Shop, and CMA Discharge Area. Unused or 

expired fire equipment from MNARNG facilities is shipped to the USPFO warehouse to be stored 

and/or processed prior to reutilization or disposition. TriMaxTM fire extinguishers were required to 

be demilitarized, which involved physically destroying them by the CMA shop, prior to final 

disposition. AFFF was dispensed and allowed to dissipate to the ground surface in approximately 

2010. The discharge area is in proximity to up-and side-gradient onsite drinking water supply wells

L Well and N Well, as well as downgradient onsite drinking water supply well H Well. As of June 

2021, the facility processes TriMaxTM units by draining and triple rinsing. The solution and rinsate 

are stored in the CMA shop in hazardous waste storage rooms. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-3

PFOA, PFOS, PFHxS, and PFNA were detected in surface soil at AOI 4. Site workers, 

construction workers, on- and off-facility residents, and trespassers could contact constituents in 

surface soil via incidental ingestion and inhalation of dust. No active construction was observed 

to be occurring near AOI 4 at the time of the SI. Therefore, the surface soil exposure pathway for 

site workers, future construction workers, on- and off-facility residents, and trespassers are 

considered potentially complete. PFOS, PFNA, and PFHxS were detected in subsurface soil at 

AOI 4. Construction workers could contact constituents in subsurface soil via incidental ingestion; 

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

complete. The CSM for AOI 4 is presented on Figure 7-4. 

7.1.5 AOI 5-WWTP 

AOI 5-WWTP is located in the southeast part of the facility abutting the Mississippi River. The 

WWTP does not contain a treatment for PFAS, leading to the potential release to soil and 

groundwater from AOI 5 through wastewater treatment and sludge disposal at the AOI 5-Sludge 

Spread Site.

PFOA, PFOS, PFHxS, and PFNA, were detected in surface soil at AOI 5-WWTP. Site workers, 

construction workers, on- and off-facility residents, and trespassers could contact constituents in 

surface soil via incidental ingestion and inhalation of dust. At the time of the SI, no construction 

activities were observed to be occurring near AOI 5. Therefore, the surface soil exposure pathway 

for site workers, future construction workers, on- and off-facility residents, and trespassers are 

potentially complete. PFOS, PFHxS, and PFBS were detected in subsurface soil at AOI 5-WWTP. 

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

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

complete. The CSM for the AOI 5-WWTP is presented on Figure 7-5. 

7.1.6 AOI 5-Sludge Spread Site 

The AOI 5-Sludge Spread Site is located to the northwest of the main cantonment area. Since 

1987, Camp Ripley has been permitted to perform land application of sludge from the WWTP at 

the Sludge Spread Site, which may have introduced PFAS to the area. 

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in surface soil at AOI 5. Site workers, 

construction workers, on- and off-facility residents, and trespassers could contact constituents in 

surface soil via incidental ingestion and inhalation of dust. At the time of the SI, no construction 

activities were observed to be occurring near AOI 5-Sludge Spread Site. Therefore, the surface 

soil exposure pathway for site workers, future construction workers, on- and off-facility residents, 

and trespassers are potentially complete. PFHxS, PFBS, PFNA, PFOA, and PFOS were detected 

in subsurface soil at AOI 5-Sludge Spread Site. Construction workers could contact constituents 

in subsurface soil via incidental ingestion, and therefore, the subsurface soil exposure pathway 

for future construction workers is potentially complete. The CSM for AOI 5 Sludge Spread Site is 

presented on Figure 7-6. 

7.1.7 AOI 6 

AOI 6 is the Stormwater Infiltration Basin located in the northeast portion of the facility. Fire training

exercises occurred at the EMTC. The disposition of the foam mixture was likely disposed of in the 

stormwater sewer system, which drains to the stormwater infiltration basin. 

PFOA, PFOS, PFHxS, PFNA, and PFBS was detected in surface soil at AOI 6. Site workers, 

construction workers, on- and off-facility residents, and trespassers could contact constituents in 

surface soil via incidental ingestion and inhalation of dust. There were no construction activities 

observed to be occurring near AOI 6 at the time of the SI. Therefore, the surface soil exposure 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-4

pathway for site workers, future construction workers, on- and off-facility residents, and 

trespassers are potentially complete. PFOS was detected in subsurface soil at AOI 6. 

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

therefore, the subsurface soil exposure pathway for future construction workers is considered 

potentially complete. The CSM for AOI 6 is presented on Figure 7-7. 

7.1.8 AOI 7 

AOI 7 consists of Buildings 2-166, 2-203. 2-223, and 2-272. Three AFFF capable firetrucks were

at the old CSMS, referred to as Building 2-166, two were stored in Building 2-203, and a rescue 

truck was stored in Building 2-272. Significant maintenance for current and previous fire support 

vehicles have been performed, with potential releases of PFAS to the soil and groundwater. Bulk 

AFFF is stored in Buildings 2-223 and 2-272, both containing floor drains that connect to an oilwater separator or to the sanitary sewer. PFAS were potentially released to soil and groundwater 

from AOI 7 through previous fire training exercises and/or firetruck and AFFF storage.

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in surface soil at AOI 7. Site workers, 

construction workers, on- and off-facility residents, and trespassers could contact constituents in 

surface soil via incidental ingestion and inhalation of dust. No active construction activities were 

observed to be occurring near AOI 7 at the time of the SI. Therefore, the surface soil exposure 

pathway for site workers, future construction workers, on- and off-facility residents, and 

trespassers are potentially complete. PFOS, PFHxS, and PFBS were detected in subsurface soil 

at AOI 7. Construction workers could contact constituents in subsurface soil via incidental 

ingestion, and therefore, the subsurface soil exposure pathway for future construction workers is 

potentially complete. The CSM for AOI 7 is presented on Figure 7-8. 

7.1.9 AOI 8 

AOI 8 is Building 8-195, which has stored a large crash rescue truck (011A) since around 1987. 

It is unclear if the truck had AFFF capability. Building 8-195 was renovated in 2010 and is currently 

a Morale Welfare Recreation facility. 

PFOS, PFHxS, and PFNA were detected in surface soil at AOI 8. Site workers, construction 

workers, on- and off-facility residents, and trespassers could contact constituents in surface soil 

via incidental ingestion and inhalation of dust. At the time of the SI, no construction activities were 

observed to be occurring near AOI 8 at the time of the SI. Therefore, the surface soil exposure 

pathway for site workers, future construction workers, on- and off-facility residents, and 

trespassers are potentially complete. PFHxS, PFNA, PFOA, and PFOS were detected in 

subsurface soil at AOI 8. Construction workers could contact constituents in subsurface soil via 

incidental ingestion; therefore, the subsurface soil exposure pathway for future construction 

workers is potentially complete. The CSM for AOI 8 is presented on Figure 7-9. 

7.2 Groundwater Exposure Pathway

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

exists between the source and potential receptors based on the aforementioned criteria.

7.2.1 AOI 1 

PFOA, PFOS, PFNA, and PFHxS were detected above their SLs in groundwater samples 

collected at AOI 1. Due to the presence of domestic wells within a 4-mile radius of the facility,

approximately screened within the same water bearing unit, the pathway for exposure to offfacility residents via ingestion of groundwater is considered potentially complete with 

exceedances. Drinking water at Camp Ripley is provided by on-facility potable wells. Based on 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-5

this and the results of the SI, the pathway for exposure to site workers, on-facility residents, and 

trespassers is considered potentially complete with exceedances. Depths to water measured at 

AOI 1 in June 2022 during the SI ranged from 18.01 to 18.74 feet bgs. Therefore, the ingestion 

exposure pathway for future construction workers is considered incomplete. The CSM for AOI 1

is presented on Figure 7-1. 

7.2.2 AOI 2 

PFOA and PFOS were detected above their SLs in groundwater samples collected at AOI 2. Due 

to the presence of domestic wells within a 4-mile radius of the facility, approximately screened 

within the same water bearing unit, the pathway for exposure to off-facility residents via ingestion 

of groundwater is considered potentially complete with exceedances. Drinking water at Camp 

Ripley is provided by on-facility potable wells. Based on this and the results of the SI, the pathway 

for exposure to site workers, trespassers, and on-facility residents is considered potentially 

complete with exceedances. Depths to water measured in June 2022 during the SI ranged from 

10.55 to 12.52 feet bgs. Therefore, the ingestion exposure pathway for future construction 

workers is considered potentially complete with exceedances. The CSM for AOI 2 is presented 

on Figure 7-2. 

7.2.3 AOI 3 

PFOA, PFOS, and PFBS were detected below their SLs in groundwater samples collected at AOI 

3. Due to the presence of domestic wells within a 4-mile radius of the facility, approximately

screened within the same water bearing unit, the pathway for exposure to off-facility residents via

ingestion of groundwater is considered potentially complete. Drinking water at Camp Ripley is

provided by on-facility potable wells. Based on this and the results of the SI, the pathway for

exposure to site workers, on-facility residents, and trespassers is considered potentially complete.

Depths to water measured in June 2022 during the SI ranged from 15.72 to 17.47 feet bgs. At the

time of the SI, construction activities were occurring approximately 700 feet from AOI 3. Therefore,

the ingestion exposure pathway for current and future construction workers is considered

incomplete. The CSM for AOI 3 is presented on Figure 7-3.

7.2.4 AOI 4 

PFOA, PFOS, PFHxS, and PFNA were detected above their SLs in groundwater samples 

collected at AOI 4. Due to the presence of domestic wells within a 4-mile radius of the facility,

approximately screened within the same water bearing unit, the pathway for exposure to offfacility residents via ingestion of groundwater is considered potentially complete with 

exceedances. Drinking water at Camp Ripley is provided by on-facility potable wells. Based on 

drinking water at the facility and the results of the SI, the pathway for exposure to site workers, 

on-facility residents, and trespassers is considered potentially complete with exceedances. 

Depths to water measured in June 2022 during the SI ranged from 8.12 to 16.75 feet bgs. 

Therefore, the ingestion exposure pathway for future construction workers is considered 

potentially complete with exceedances. The CSM for AOI 4 is presented on Figure 7-4. 

7.2.5 AOI 5-WWTP 

PFOS and PFHxS were detected above their SLs in groundwater samples collected at the AOI 5-

WWTP. Drinking water at Camp Ripley is provided by on-facility potable wells, which are located 

upgradient of the WWTP and thus are not interpreted to be at risk of receiving contamination from 

the WWTP. Based on this and the results of the SI, the pathway for exposure to site workers, onfacility residents, and trespassers is considered incomplete. Depths to water measured in June 

2022 during the SI ranged from 8.26 to 12.90 feet bgs at AOI 5-WWTP. Therefore, the ingestion 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-6

exposure pathway for future construction workers is considered potentially complete with 

exceedances. The CSM for AOI 5 is presented on Figure 7-5. 

Four existing facility wells were sampled along with AOI 5; however, they are considered

independent from the AOI 5 release areas and have no bearing on either the AOI 5-WWTP or the 

AOI 5-Sludge Spread Site CSM. 

7.2.6 AOI 5-Sludge Spread Site 

The AOI 5-Sludge Spread Site is located to the northwest of the main cantonment area, 

upgradient of drinking water wells supplying the cantonment area. PFOS was detected below the 

SL at one well (AOI05-04) and results were non-detect for all relevant compounds at the other 

wells at the Sludge Spread Site. Therefore, the pathway for exposure to site workers, on-facility 

residents, and trespassers is considered incomplete. Depths to water measured in June 2022 

during the SI ranged from 3.67 to 22.38 feet bgs. Therefore, the ingestion exposure pathway for 

future construction workers is considered potentially complete. The CSM for the AOI 5-Sludge 

Spread Site is shown on Figure 7-6. 

7.2.7 AOI 6 

PFOS was detected above the SL in groundwater samples collected at AOI 6. Due to the presence 

of domestic wells within a 4-mile radius of the facility, approximately screened within the same 

water bearing unit, the pathway for exposure to off-facility residents via ingestion of groundwater 

is considered potentially complete with exceedances. Drinking water at Camp Ripley is provided 

by on-facility potable wells. Based on this and the results of the SI, the pathway for exposure to 

site workers, on-facility residents, and trespassers is considered potentially complete with 

exceedances. Depths to water measured in June 2022 during the SI ranged from 3.04 to 5.87

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

potentially complete with exceedances. The CSM for AOI 6 is presented on Figure 7-7. 

7.2.8 AOI 7 

PFOA, PFOS, and PFHxS were detected above their SLs in groundwater samples collected at 

AOI 7. Due to the presence of domestic wells within a 4-mile radius of the facility, approximately 

screened within the same water bearing unit, the pathway for exposure to off-facility residents via 

ingestion of groundwater is considered potentially complete with exceedances. Drinking water at 

Camp Ripley is provided by on-facility potable wells. Based on this and the results of the SI, the 

pathway for exposure to site workers, on-facility residents, and trespassers is considered 

potentially complete with exceedances. Depths to water measured in July 2022 during the SI 

ranged from 11.69 to 17.89 feet bgs. Therefore, the ingestion exposure pathway for future 

construction workers is considered potentially complete with exceedances. The CSM for AOI 7 is 

presented on Figure 7-8. 

7.2.9 AOI 8 

PFOA, PFOS, and PFHxS were detected above their respective SLs in groundwater samples 

collected at AOI 8. Due to the presence of domestic wells within a 4-mile radius of the facility,

approximately screened within the same water bearing unit, the pathway for exposure to offfacility residents via ingestion of groundwater is considered potentially complete with 

exceedances. Drinking water at Camp Ripley is provided by on-facility potable wells. Based on 

this and the results of the SI, the pathway for exposure to site workers, on-facility residents, and 

trespassers is considered potentially complete with exceedances. Depths to water measured in 

June 2022 during the SI ranged from 17.17 to 18.88 feet bgs. Therefore, the ingestion exposure 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-7

pathway for future construction workers is considered incomplete. The CSM for AOI 8 is presented 

on Figure 7-9. 

7.3 Surface Water and Sediment Exposure Pathway

The SI results in soil and groundwater, in combination with knowledge of the fate and transport 

properties of PFAS, were used to determine whether a potentially complete pathway exists 

between the source and potential receptors.

7.3.1 AOI 1 

PFAS are water soluble and can migrate readily from soil to surface water via leaching and runoff. PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil and groundwater at AOI 1. It is

possible that those compounds may have migrated from soil and groundwater to the Mississippi 

River via shallow groundwater discharge or discharge to the stormwater infiltration basins along 

the southeastern facility boundary. These infiltration basins are designed to allow stormwater to 

infiltrate into the subsurface and subsequently the unconfined surficial aquifer, which is in 

connection with surface water. Therefore, the surface water and sediment ingestion exposure 

pathway for site workers, future construction workers, on- and off-facility residents, or 

trespassers/recreational user is considered potentially complete. 

There is documentation of a PFAS release from a TriMaxTM fire extinguisher discharge at AOI 1 in 

the early 2000s. The area within and outside the facility boundaries are relatively flat, making the 

possible route of runoff uncertain. Stormwater conveyance at the airfield is primarily via overland 

flow, so stormwater may either locally infiltrate in grassy areas, or eventually drain east-southeast.

As surface water and shallow groundwater are connected, stormwater from these basins may 

eventually enter the Mississippi River. Due to potential recreational use of the Mississippi River

and City of Little Falls-Mississippi River watershed south of the facility, the surface water and 

sediment ingestion exposure pathway for off-facility recreational users is also considered 

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

7.3.2 AOI 2 

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil and groundwater at AOI 2. It is 

possible that those compounds may have migrated from soil and groundwater to the Mississippi 

River via shallow groundwater discharge. As AOI 2 is located in a grassy area north of the airfield 

runway, any surface water is likely to infiltrate locally into the soil and subsequently may migrate

into the unconfined surficial aquifer. Therefore, the surface water and sediment ingestion 

exposure pathway for site workers, future construction workers, on- and off-facility residents, or 

trespassers is considered potentially complete. 

Shallow groundwater at the facility is understood to be in connection with surface water; due to 

potential recreational use of the Mississippi River downgradient of AOI 2, the surface water and 

sediment exposure pathway for off-facility recreational users is also considered potentially 

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

7.3.3 AOI 3 

PFOA, PFOS, PFNA, and PFBS were detected in soil and groundwater at AOI 3 below their 

respective SLs. It is possible that those compounds may have migrated from soil and groundwater 

to the Mississippi River via shallow groundwater discharge or discharge to the stormwater 

infiltration basins along the southeastern facility boundary. As AOI 3 is primarily located in grassy 

or non-paved areas, any surface water likely infiltrates locally into the soil which may subsequently 

migrate into the unconfined surficial aquifer. Therefore, the surface water and sediment ingestion 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-8

exposure pathway for site workers, future construction workers, on- and off-facility residents, or 

trespassers is considered potentially complete. 

Shallow groundwater at the facility is understood to be in connection with surface water; due to 

potential recreational use of the Mississippi River downgradient of AOI 3, the surface water and 

sediment exposure pathway for off-facility residents and recreational users is also considered 

potentially complete. The CSM for AOI 3 is presented on Figure 7-3. 

7.3.4 AOI 4 

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil and groundwater at AOI 4. It is 

possible that those compounds may have migrated from soil and groundwater to the Mississippi 

River via shallow groundwater discharge or discharge to the stormwater infiltration basins along 

the southeastern facility boundary. Additionally, AOI 4 is serviced by a stormwater drainage 

network which discharges to Infiltration Basin D; any stormwater runoff from this area may locally 

infiltrate directly to the soil in non-paved areas or gets captured in the infiltration basin. PFOA, 

PFOS, PFHxS, and PFNA were detected with exceedances in groundwater at AOI 4. TriMaxTM

fire extinguishers containing AFFF were historically shipped to and demilitarized by the CMA shop 

located within AOI 4. It is unknown if the units were received full or emptied at the airfield. 

Therefore, the surface water and sediment ingestion exposure pathway for site workers, future 

construction workers, on- and off-facility residents, or trespassers is considered potentially 

complete.

Shallow groundwater and surface water at the facility are understood to be connected. The 

Infiltration Basin D collecting runoff from AOI 4 allows stormwater to infiltrate into the subsurface, 

where it can migrate to shallow groundwater and then downgradient to the Mississippi River. Due 

to potential recreational use of the Mississippi River, the surface water and sediment ingestion 

exposure pathway for off-facility recreational users is also considered potentially complete. The 

CSM for AOI 4 is presented on Figure 7-4. 

7.3.5 AOI 5 – WWTP

PFAS was potentially released to soil and groundwater from wastewater treatment at AOI 5-

WWTP through leaching and/or stormwater conveyance. The WWTP does not contain a PFAS 

treatment system, leading to a potential release through surface water infiltration into the 

subsurface or via a stormwater outfall which discharges to the Mississippi River. PFOS and 

PFHxS were detected with exceedances of their respective SLs in groundwater at the WWTP.

Therefore, the surface water and sediment ingestion exposure pathway for site workers, future 

construction workers, on- and off-facility residents, or trespassers is considered incomplete. 

As mentioned, surface water may migrate to shallow groundwater at the WWTP and discharge to 

the Mississippi River through infiltration or the WWTP stormwater outfall. Therefore, due to 

potential recreational use of the Mississippi River, the surface water and sediment ingestion 

exposure pathway for off-facility recreational users is considered potentially complete. The CSM 

for AOI 5-WWTP is presented on Figure 7-5. 

As discussed in Section 7.2.5, the four existing facility wells sampled along with AOI 5-WWTP 

and the AOI 5-Sludge Spread Site are not evaluated as part of the CSM. 

7.3.6 AOI 5 – Sludge Spread Site

PFAS was potentially released to soil and groundwater from the AOI 5-WWTP during sludge land 

application at the AOI 5-Sludge Spread Site. There were no exceedances of soil and groundwater 

at this release area, and two of the three wells sampled in this upgradient area (AOI05-02 and 

AOI05-03) were non-detect for all relevant PFAS. Surface water at the Sludge Spread Site likely 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-9

infiltrates locally but is not connected to the stormwater drainage network like the AOIs in the 

cantonment area. It is possible that surface water may migrate to shallow groundwater at this 

location followed by drinking water supply wells located downgradient of the Sludge Spread Site. 

Therefore, the surface water and sediment ingestion exposure pathway for site workers, future 

construction workers, and on- and off-facility residents, or trespassers is considered incomplete. 

As surface water may migrate to the unconfined surficial aquifer on the facility, it may eventually 

discharge to the Mississippi River. The surface water and sediment ingestion exposure pathway 

for off-facility recreational users is considered potentially complete. The CSM for AOI 5-Sludge 

Spread Site is presented on Figure 7-6. 

7.3.7 AOI 6 

AOI 6 is a Stormwater Infiltration Basin, located in the northeast portion of the facility, bordering 

the Mississippi River. PFAS from other potential releases of AFFF within the cantonment area 

may have been drained to AOI 6 via sewers or infiltrated shallow groundwater and migrated to 

the Mississippi River. PFAS was potentially released to soil and groundwater from AOI 6 during 

previous fire training exercises held at the EMTC. The final disposition of any remaining foam 

mixture was likely disposed of in the stormwater sewer system, which drains to the AOI 6

stormwater infiltration basin. PFOS was detected with exceedances in groundwater at AOI 6. The 

stormwater collected in the infiltration basin eventually migrates to the subsurface. As AOI 6 is 

located generally up- or side-gradient of some drinking water supply wells in the cantonment area, 

there is potential for impacts from soil and groundwater at AOI 6 to these wells via surface water 

infiltration and migration. Therefore, the surface water and sediment exposure pathways for site 

workers, future construction workers, on- and off-facility residents, trespassers, and off-facility 

recreational users are potentially complete. The CSM for AOI 6 is presented on Figure 7-7. 

7.3.8 AOI 7 

PFOA, PFOS, PFHxS, and PFBS were detected in soil and groundwater at AOI 7. The buildings 

located within AOI 7 stored fire and rescue trucks, as well as bulk AFFF. Floor drains in Building 

2-272, which stored the bulk AFFF and rescue truck, are connected to the sanitary sewer. It is

possible that those compounds may have migrated from soil and groundwater to the Mississippi

River in the east-southeast portion of the facility via shallow groundwater discharge or discharge

to the stormwater Infiltration Basin E. PFOA, PFOS, and PFHxS were detected with exceedances

in groundwater. Therefore, the surface water and sediment ingestion exposure pathway for site

workers, future construction workers, on- and off-facility residents, or trespassers is considered

potentially complete.

Stormwater drainages across AOI 7 convey runoff to Infiltration Basin E, which eventually 

infiltrates into the subsurface. As surface water may migrate to the unconfined surficial aquifer on 

the facility, it may eventually discharge to the Mississippi River. The surface water and sediment 

ingestion exposure pathway for off-facility recreational users is also considered potentially 

incomplete. The CSM for AOI 7 is presented on Figure 7-8. 

7.3.9 AOI 8 

AOI 8 is Building 8-195, which has stored a large crash rescue truck (011A) since around 1987. 

It is unclear if the truck had AFFF capability. Building 8-195 was renovated in 2010 and is currently 

a Morale Welfare Recreation facility, which has an outside recreation and eating area frequented 

by facility residents and personnel, family members (including children), and site workers.

PFOA, PFOS, and PFHxS were detected in groundwater at concentrations above their SLs. AOI 

8 has stormwater drainage conveyance to Infiltration Basin A. It is possible that releases from AOI 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 7-10

8 migrated to surface water either by infiltration through the subsurface to groundwater or via 

stormwater conveyance. Stormwater in the infiltration basin may eventually migrate to the 

Mississippi River. Therefore, the surface water and sediment ingestion exposure pathway for site 

workers, future construction workers, on- and off-facility residents, or trespassers is considered 

potentially complete. Due to recreational use of the Mississippi River, the surface water and 

sediment ingestion exposure pathway for off-facility recreational users is also considered 

potentially complete. The CSM for AOI 8 is presented on Figure 7-9. 
Media

SOURCE PATHWAY RECEPTOR

AOI 1

TriMaxTM

Discharge Area

and Building 8-

197

Surface soil

Human

activities

Precipitation/

run-off

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-1

Conceptual Site Model, AOI 1

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 1.

Notes:

Leaching/

infiltration

7-11
Media

SOURCE PATHWAY RECEPTOR

AOI 2 Burn Pit Fire

Training Area

Surface soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-2

Conceptual Site Model, AOI 2

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 2.

Notes:

7-12
Media

SOURCE PATHWAY RECEPTOR

AOI 3

DHS

Demonstration at 

EMTC

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-3

Conceptual Site Model, AOI 3

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

DHS = Department of Homeland Security

EMTC = Emergency Management Training Center

1. The resident and recreational users refer to on- and

off-facility receptors.

2. Inhalation of dust for off-facility receptors is likely

insignificant.

3. At the time of the SI, construction was occurring

approximately 700 feet away from AOI 3.

Notes:

7-13
Media

SOURCE PATHWAY RECEPTOR

AOI 4

USFPO

Warehouse, CMA

Shop, CMA

Discharge Area

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-4

Conceptual Site Model, AOI 4

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

CMA = Combined Maintenance Activity

USFPO = US Property and Fiscal Office

1. The resident and recreational users refer to on- and

off-facility receptors.

2. Inhalation of dust for off-facility receptors is likely

insignificant.

3. No current active construction at AOI 4.

Notes:

7-14
Media

SOURCE PATHWAY RECEPTOR

AOI 5 Wastewater

Treatment Plant

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-5

Conceptual Site Model, AOI 5-Wastewater Treatment Plant

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 5-WWTP.

Notes:

7-15
Media

SOURCE PATHWAY RECEPTOR

AOI 5 Sludge Spread

Site

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-6

Conceptual Site Model, AOI 5-Sludge Spread Site

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 5-Sludge

Spread Site.

Notes:

7-16
Media

SOURCE PATHWAY RECEPTOR

AOI 6 Stormwater

Infiltration Basin

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-7

Conceptual Site Model, AOI 6

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 6.

Notes:

7-17
Media

SOURCE PATHWAY RECEPTOR

AOI 7

Buildings 2-166,

2-203, 2-223, and

2-272

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-8

Conceptual Site Model, AOI 7

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 7.

Notes:

7-18
Media

SOURCE PATHWAY RECEPTOR

AOI 8 Building 8-195

Surface soil

Subsurface

soil

Human

activities

Precipitation/

run-off

Leaching/

infiltration

Airborne soil

particulate

Surface soil

at AOI

Surface

water/

sediment

Subsurface

soil

Shallow

groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/ / / /

Site

Worker

Construction 

Worker3 Resident1,2 Trespasser/ Recreational User1

Site

Worker

Construction 

Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-9

Conceptual Site Model, AOI 8

Camp Ripley

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser/ 

Recreational User1

1. The resident and recreational users refer to onand off-facility receptors.

2. Inhalation of dust for off-facility receptors is

likely insignificant.

3. No current active construction at AOI 8.

Notes:

7-19
AECOM 5-16

THIS PAGE INTENTIONALLY BLANK

M 7-20
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 8-1

8. Summary and Outcome

This section summarizes SI activities and findings. The most significant findings are summarized 

in this section and are reproduced directly or abstracted from information contained in this report. 

The outcome provides general and comparative interpretations of the findings relative to the SLs. 

8.1 SI Activities 

The SI field activities were conducted from 6 to 17 June 2022 and consisted of utility clearance, 

direct push boring, soil sample collection, temporary monitoring well installation, grab groundwater 

sample collection, synoptic gauging, temporary well abandonment, and land surveying. Field 

activities were conducted in accordance with the SI QAPP Addendum (AECOM, 2022a), except as 

previously noted in Section 5.9. 

To fulfill the project DQOs set forth in the approved SI QAPP Addendum (AECOM, 2022a), samples 

were collected and analyzed for a subset of 18 compounds by LC/MS/MS compliant with QSM 5.3 

Table B-15 as follows. 

• Eighty-eight (88) soil samples from 32 boring locations;

• Twenty-nine (29) grab groundwater samples from 30 temporary well locations;

• Four (4) grab groundwater samples from four existing permanent wells;

• Thirty-five (35) QA/ QC samples.

An SI is conducted when the PA determines an AOI exists based on probable use, storage, and/or 

disposal of PFAS-containing materials. The SI includes multi-media sampling at AOIs to 

determine whether or not a release has occurred. The SI may conclude further investigation is 

warranted, a removal action is required to address immediate threats, or no further action is 

required. Additionally, the CSMs were refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at the AOIs, which are 

described in Section 7. 

8.2 Outcome 

Based on the results of this SI, further evaluation under CERCLA is warranted in an RI for AOI 1, 

AOI 2, AOI 4, AOI 5-WWTP, AOI 6, AOI 7, and AOI 8; no further evaluation is warranted for AOI 3 

or AOI 5-Sludge Spread Site at this time (see Table 8-1). Based on the CSMs developed and 

revised in light of the SI findings, there is potential for exposure to drinking water receptors from 

AOI 1, AOI 2, AOI 4, AOI 5-WWTP, AOI 6, AOI 7, and AOI 8 from sources on the facility resulting 

from historical DoD activities. Sample analytical concentrations collected during the SI were 

compared against the project SLs in soil and groundwater, as described in Table 6-1. A summary 

of the results of the SI data relative to the SLs is as follows: 

• At AOI 1:

• PFOA, PFOS, PFNA, and PFHxS in groundwater exceeded their SLs. PFOA

exceeded the SL of 6 ng/L, with a maximum concentration of 56.0 ng/L at location

AOI01-02. PFOS exceeded the SL of 4 ng/L, with a maximum concentration of 1500

ng/L at location AOI01-02. PFNA exceeded the SL of 6 ng/L, with a maximum

concentration of 34.9 ng/L at location AOI01-02. PFHxS exceeded the SL of 39 ng/L,

with a maximum concentration of 216 ng/L at location AOI01-02. Based on the results

of the SI, further evaluation of AOI 1 is warranted in an RI.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 8-2

• PFOS in surface soil exceeded the SL of 13 μg/kg at AOI01-02, with a concentration

of 33.6 μg/kg. The detected concentrations of PFOA, PFHxS, and PFNA in soil were

below their respective SLs.

• At AOI 2:

• PFOA and PFOS in groundwater exceeded their SLs. PFOA exceeded the SL of 6

ng/L with a concentration of 8.92 ng/L at location AOI02-01. PFOS exceeded the SL

of 4 ng/L with a maximum concentration of 20.5 ng/L at location AOI02-01. Based on

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

• The detected concentrations of PFOS, PFHxS, and PFNA in soil at AOI 2 were below

their respective SLs.

• At AOI 3:

• The detected concentrations of PFOA, PFOS, and PFBS in groundwater at AOI 3

were below their respective SLs. Based on the results of the SI, further evaluation of

AOI 3 is not warranted in an RI.

• Detected concentrations of PFOA, PFOS, and PFNA in surface soil at AOI 3 were

below their respective SLs.

• At AOI 4:

• PFOA, PFOS, PFHxS, and PFNA in groundwater exceeded their respective SLs.

PFOA exceeded the SL of 6 ng/L, with a maximum concentration of 15.0 ng/L at

location AOI04-04. PFOS exceeded the SL of 4 ng/L, with a maximum concentration

of 74.2 ng/L at location AOI04-04. PFHxS exceeded the SL of 39 ng/L, with a

concentration of 132 ng/L at location AOI04-04. PFNA exceeded the SL of 6 ng/L,

with a concentration of 14.7 ng/L at location AOI04-03. Based on the results of the

SI, further evaluation of AOI 4 is warranted in an RI.

• Detected concentrations of PFOA, PFOS, PFHxS, and PFNA in surface soil at AOI

4 were below their respective SLs.

• At AOI 5-WWTP:

• PFOS and PFHxS in groundwater exceeded their SLs. PFOS exceeded the SL of 4

ng/L, with a maximum concentration of 62.4 ng/L at location AOI05-06. PFHxS

exceeded the SL of 39 ng/L, with a concentration of 43.0 ng/L at location AOI05-06.

Based on the results of the SI, further evaluation of AOI 5-WWTP is warranted in an

RI.

• Detected concentrations of PFOA, PFOS, PFHxS, PFNA, and PFBS in soil at AOI

5-WWTP were below their respective SLs.

• At AOI 5-Sludge Spread Site

• PFOS was detected below the SL of 4 ng/L in one well, AOI05-04, with a

concentration of 0.956 J ng/L. All other relevant compounds were non-detect for

AOI05-04, and all relevant compounds were non-detect for wells AOI05-02 and

AOI05-03. Based on the results of the SI, further evaluation of AOI 5-Sludge Spread

Site is not warranted in an RI.

• Detected concentrations of PFOA, PFOS, PFHxS, PFNA, and PFBS in soil at AOI 5-

Sludge Spread Site were below their respective SLs.
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 8-3

• At AOI 6:

• PFOS detected in groundwater at AOI 6 exceeded the SL of 4 ng/L in all three wells

sampled, with a maximum concentration of 13.8 ng/L at location AOI06-01. The

detected concentrations of PFOA, PFNA, PFHxS, and PFBS in groundwater at AOI

6 were below their respective SLs. Based on the results of the SI, further evaluation

of AOI 6 is warranted in an RI.

• Detected concentrations of PFOA, PFOS, PFHxS, PFNA, and PFBS in surface soil

at AOI 6 were below their respective SLs.

• At AOI 7:

• PFOA, PFOS, and PFHxS in groundwater at AOI 7 exceeded their respective SLs.

PFOA exceeded the SL of 6 ng/L, with a concentration of 6.20 ng/L at location AOI07-

02. PFOS exceeded the SL of 4 ng/L, with a maximum concentration of 237 ng/L at

location AOI07-01. PFHxS exceeded the SL of 39 ng/L, with a maximum

concentration of 172 ng/L at location AOI07-01. Based on the results of the SI, further

evaluation of AOI 7 is warranted in an RI.

• Detected concentrations of PFOS, PFNA, PFHxS, PFBS, and PFOA in surface soil

at AOI 7 were below their SLs.

• At AOI 8:

• PFOA, PFOS, and PFHxS in groundwater at AOI 8 exceeded their respective SLs.

PFOA exceeded the SL of 6 ng/L, with a concentration of 20.3 ng/L at location AOI08-

01. PFOS exceeded the SL of 4 ng/L at all three wells sampled, with a maximum

concentration of 71.0 ng/L at location AOI08-02. PFHxS exceeded the SL of 39 ng/L,

with a concentration of 247 ng/L at location AOI08-01. Based on the results of the SI,

further evaluation of AOI 8 is warranted in an RI.

• Detected concentrations of PFOS, PFNA, and PFHxS in surface soil at AOI 8 were

below their respective SLs.

Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA 

(commonly referred to as GenX) was not included as an analyte at the time of this SI. Based on 

the CSM developed during the PA and revised based on SI findings, the presence of HFPO-DA 

is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC 

AFFF and based on its history including distribution limitations that restricted use of GenX, it is 

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

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

Table 8-1 summarizes the SI results for soil and groundwater used to determine if an AOI should 

be considered for further investigation under CERCLA and undergo an RI. 
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 8-4

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

AOI Potential 

Release Area

Soil –

Source 

Area

Groundwater – 

Source Area Future Action

1 TriMaxTM Discharge 

Area and Building 8-197 Proceed to RI 

2 Burn Pit Fire Training 

Area Proceed to RI

3 DHS Demonstration No Further Action

4 

USPFO Warehouse, 

CMA Shop, and CMA 

Discharge Area

Proceed to RI

5 

WWTP Proceed to RI

Sludge Spread Site No Further Action

6 Stormwater Infiltration 

Basin Proceed to RI

7 Buildings 2-166, 2-203, 

2-223, and 2-272 Proceed to RI

8 Building 8-195 Proceed to RI

Legend:

CMA = Combined Maintenance Activity

DHS = Department of Homeland Security

FTA = fire training area

RI = Remedial Investigation

USPFO = United States Property and Fiscal Office

WWTP = wastewater treatment plant

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

Camp Ripley, Little Falls, Minnesota

AECOM 9-1

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