FINAL

Site Inspection Report 

Holman Field Army Aviation 

Support Facility

St. Paul, 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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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....................................................................................................2-2

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

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

2.2.6 Sensitive Habitat and Threatened/ Endangered Species.............................2-3

2.3 History of PFAS Use..............................................................................................2-3

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

3.1 AOI 1 South Hanger Ramp and Fire Truck Storage Area ......................................3-1

3.2 Adjacent Sources ..................................................................................................3-1

3.2.1 St. Paul Downtown Airport...........................................................................3-1

3.2.2 Upgradient Sources ....................................................................................3-1

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

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

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

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

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

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

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

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

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

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

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

5.7 Laboratory Analytical Methods ..............................................................................5-5

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

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

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

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

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

7.3 Surface Water and Sediment Exposure Pathway ..................................................7-2

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

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

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

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

Appendix A Data Usability Assessment and Validation Reports

Appendix B Field Documentation

B1. Log of Daily Notice of Field Activities

B2. Sampling Forms

B3. Survey Data

Appendix C Photographic Log

Appendix D TPP Meeting Minutes

Appendix E Boring Logs 

Appendix F Analytical Results

Appendix G Laboratory Reports

Figures

Figure 2-1 Facility Location

Figure 2-2 Facility Topography

Figure 2-3 Groundwater Features

Figure 2-4 Groundwater Elevations, May 2022

Figure 2-5 Surface Water Features

Figure 3-1 Area of Interest

Figure 5-1 Site Inspection Sample Locations

Figure 6-1 PFOA Detections in Soil

Figure 6-2 PFOS Detections in Soil

Figure 6-3 PFBS Detections in Soil

Figure 6-4 PFHxS Detections in Soil

Figure 6-5 PFNA Detections in Soil

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

Figure 6-7 PFHxS and PFNA Detections in Groundwater

Figure 7-1 Conceptual Site Model, AOI 1

Tables

Table ES-1 Screening Levels (Soil and Groundwater)

Table ES-2 Summary of Site Inspection Findings and Recommendations

Table 5-1 Site Inspection Samples by Medium

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

Elevations

Table 6-1 Screening Levels (Soil and Groundwater)

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

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

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

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

% percent

°C degrees Celsius

°F degrees Fahrenheit

μg/kg micrograms per kilogram

AASF Army Aviation Support Facility

AECOM AECOM Technical Services, Inc.

AFFF aqueous film-forming foam

AOI Area of Interest

ARNG Army National Guard

ASTM American Society for Testing and Materials

bgs below ground surface 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CoC chain of custody

CSM conceptual site model

DA Department of the Army

DoD Department of Defense

DOT Department of Transportation

DPT direct push technology

DQO data quality objective

DUA data usability assessment

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

FedEx Federal Express

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

MAC Metropolitan Airports Commission

MIL-SPEC military specification

MNARNG Minnesota Army National Guard

MNDNR Minnesota Department of Natural Resources

MS/MSD matrix spike/ matrix spike duplicate

ND non-detect

NELAP National Environmental Laboratory Accreditation Program

ng/L nanograms per liter

OSD Office of the Secretary of Defense

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHxS perfluorohexanesulfonic acid
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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

US United States

USACE United States Army Corps of Engineers

USCS Unified Soil Classification System

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

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 one Area of Interest (AOI) where PFAS-containing materials may have been 

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

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

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

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

compounds. This SI was completed at the Holman Field Army Aviation Support Facility (AASF) in 

St. Paul, Minnesota and determined further evaluation under the Comprehensive Environmental 

Response, Compensation, and Liability Act (CERCLA) is warranted for AOI 1. The Holman Field

AASF will also be referred to as the “facility” or the AASF throughout this document. 

The Holman Field AASF is in southern Ramsey County, Minnesota, approximately 2 miles 

southeast of the City of St. Paul. The facility is accessible from State Highway 52 by Plato 

Boulevard or Eaton Street and Airport Road. The AASF is adjacent to the St. Paul Downtown 

Airport, which is bordered by the Mississippi River on the north, east, and south and on the west 

by a railroad and United States Army Corps of Engineers (USACE) flood control levy. The AASF 

was constructed in the 1920s on a 4.25-acre parcel of land owned by the Metropolitan Airports 

Commission (MAC) (MAC, 2010) and leased to the Minnesota ARNG (MNARNG). The current 

lease agreement expires on 30 September 2028. The AASF facilities include a hangar for the 

operation, maintenance, and repair of MNARNG rotary-winged and fixed-wing aircraft, 

administrative offices, and classrooms (AECOM, 2019). 

The PA identified one AOI for investigation during the SI phase. SI sampling results from the AOI

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

results of this SI, further evaluation under CERCLA is warranted in a Remedial Investigation (RI) 

for AOI 1. 

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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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

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

Groundwater –

Facility 

Boundary

Future Action

1

South 

Hanger 

Ramp and 

Fire Truck 

Storage Area

Proceed to RI 

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

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 the Holman Field Army 

Aviation Support Facility (AASF) in St. Paul, Minnesota. The Holman Field AASF is also referred 

to as the “facility” or the AASF 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 Holman Field AASF (AECOM Technical Services, Inc. [AECOM], 2019) 

that identified one Area of Interest (AOI) where PFAS-containing materials may have been used, 

stored, disposed, or released historically. The objective of the SI is to identify whether there has 

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

investigation is warranted, a removal action is required to address immediate threats, or no further 

action is required based on screening levels (SLs) for the relevant compounds. 

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

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

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

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

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

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

2.1 Facility Location and Description

The AASF is in southern Ramsey County, Minnesota, approximately 2 miles southeast of the City 

of St. Paul (Figure 2-1). The facility is accessible from State Highway 52 by Plato Boulevard or 

Eaton Street and Airport Road. The AASF is adjacent to the St. Paul Downtown Airport, which is 

bordered by the Mississippi River on the north and east, and it is bordered by commercial 

properties to the south, and a railroad and United States Army Corps of Engineers (USACE) flood 

control levy to the west. 

The AASF was constructed in the 1920s, on a 4.25-acre parcel of land owned by the Metropolitan 

Airport Commission (MAC) and leased to the Minnesota ARNG (MNARNG). The AASF facilities 

include a hangar for the operation, maintenance, and repair of MNARNG rotary-winged and fixedwing aircraft, administrative offices, and classrooms. The AASF also includes a separate parking 

area to the west, across State Highway 52. 

2.2 Facility Environmental Setting

The AASF lies within the Twin Cities metropolitan area, which is characterized by rolling to hilly 

terrain with poorly drained depressions that form ponds and lakes. The Mississippi River forms 

ravines, surrounded bluffs, and steep slopes throughout the area, as well as relatively flat areas 

along the flood plain. The elevation of the facility is approximately 705 feet above mean sea level 

and approximately 20 feet above the Mississippi River. The facility is located on the 100-year 

floodplain.

2.2.1 Geology

The AASF is situated in the St. Paul Baldwin Plains and Moraines Subsection of the Eastern 

Broadleaf Forest Province as defined by the Minnesota Department of Natural Resources 

(MNDNR) Ecological Classification System. The St. Paul Baldwin Plains and Moraines are 

characterized by Quaternary deposits directly overlying Cambrian or Ordovician bedrock 

formations. The bedrock formations form part of a gently sloping structure centered under the 

Minneapolis-St. Paul metropolitan area, known as the Twin Cities basin (WSB & Associates Inc., 

2011). Bedrock directly underlying the AASF is composed of Lower Ordovician-aged sedimentary 

deposits, namely dolostone, sandy to silty dolostone, and sandstone beds. Naturally occurring 

soils at the AASF generally consist of alluvium deposits approximately 100 feet deep from the

retreating ice of the Wisconsin glaciation. Most of the facility [Holman Field area] was originally 

marsh land; however, several grading operations utilizing river dredge material, predominantly 

sand, and other common fill generally made up of sand, clay, silt, and broken limestone, have 

been completed (MAC, 2010). 

Soils classifications fall under the Chaska and Udorthents associations. These soils are generally 

described as level to very gently sloping. The Chaska soils are present in the southern marshy 

portions of the facility and are poorly drained soils subject to frequent flooding from the Mississippi 

River consisting of silt loam for approximately the top 6 inches. The Udorthents soils are also 

present and consist of variable permeability fill soils comprised of Mississippi River dredging 

materials and various fill materials made up of sand, clay, silt, and broken limestone (MAC, 2010).

During the SI, poorly graded and well-graded sands were observed as the dominant lithology of 

the unconsolidated sediments below the Holman Field AASF. The borings were completed at 

depths between 10 and 15 feet below ground surface (bgs). Varying quantities of low to medium 

plasticity fines (silts and clay) were noted, specifically, isolated layers of silt with sand, silty lean 
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clay, lean clay, clayey silt, sandy silt, and poorly graded sand with silt were also observed in the 

borings with thicknesses ranging from a few inches to 5 feet. Many of the logs also reported 

varying percentages of gravel included in the sand packages. A representative grain-size sample 

was collected at location AOI01-01 and analyzed via American Society for Testing and Materials 

(ASTM) Method D-422. The results indicate that the soil sample is comprised primarily of fine 

sand (30.23 percent [%]) and silt (17.90%). These results and facility observations are consistent 

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

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

2.2.2 Hydrogeology

The AASF is within the Metro Groundwater Province as defined by the MNDNR. Surficial sand 

and gravel aquifers are used for domestic and some irrigation purposes, while public water supply 

and municipal wells in the region draw from deeper bedrock aquifers composed of dolomite and 

sandstone (WSB & Associates Inc., 2011). Depth to groundwater in the area ranges from 0 to 25 

feet bgs, with the shallowest wells closer to lakes, streams, and rivers. Surficial aquifers are

recharged predominantly through infiltration of precipitation, although some recharge occurs from 

open water sources and during periods of high water levels (WSB & Associates Inc., 2011). 

Regional recharge of the five major bedrock aquifers occurs to the south in Freeborn and Mower 

Counties (WSB & Associates Inc., 2011). 

No potable water wells are located within the boundary of the AASF (Figure 2-3). Several 

monitoring, commercial, and industrial wells are within 4 miles of the facility, and one domestic 

well is located less than 0.5 miles due north of the facility. Drinking water for the AASF is supplied 

by the City of St. Paul, which obtains its municipal water through the Saint Paul Regional Water 

Services. The Saint Paul Regional Water Services predominantly uses the Mississippi River as 

its drinking water source although some water is supplied by groundwater aquifers (WSB & 

Associates Inc., 2011). The Mississippi River surface water intakes are located upgradient of the 

facility, approximately 18 miles north near Fridley, Minnesota. 

Depths to water measured in May 2022 during the SI ranged from 3.83 to 7.11 feet bgs. 

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

groundwater flow direction at the AASF is primarily to the southwest. However, due to a limited 

number, spatial arrangement, and differences in depth of wells installed during the SI, these 

contours and flow direction cannot capture the full complexity of groundwater conditions at the 

facility. Groundwater conditions at the AASF will be further characterized and evaluated during 

the RI.

2.2.3 Hydrology 

The Mississippi River borders the AASF to the north and east and is a significant resource for the 

area. However, three reaches of the Mississippi River, including the segment directly adjacent to

the AASF, and several lakes in the Harriet Island-Mississippi River Watershed are listed as 

impaired by the Minnesota Pollution Control Agency due to aluminum, fecal coliform, 

polychlorinated biphenyl, PFOS, and mercury contamination and high turbidity. The largest lake 

near the AASF is Pigs Eye Lake, along the Mississippi River. 

The AASF lies within the 100-year floodplain of the Mississippi River. Freshwater wetlands are 

located to the southwest and northeast of the facility. In 2008, a floodwall was installed to protect 

against flooding (MAC, 2010). Surface water features are presented on Figure 2-5. 
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2.2.4 Climate 

The climate of St. Paul consists of warm to hot, humid summers and cold winters, with moderate 

to heavy snowfall. Thunderstorms with heavy rainfall are common in the spring, summer, and fall. 

Seasonally, temperatures vary from summer highs of 85 degrees Fahrenheit (°F) to winter lows 

of 7 °F (World Climate, 2022). The average temperature is 42.85 °F. Average precipitation is 32.04 

inches of rain and 54.4 inches of snow (World Climate, 2022). The prevailing wind varies from 

north to south, averaging 8 to 12 miles per hour, with arctic air masses throughout the winter. 

2.2.5 Current and Future Land Use

The AASF is a controlled access facility, with public roads adjacent to the St. Paul Downtown 

Airport. The St. Paul Regional Airport is owned and operated by the MAC and provides corporate 

and military air service and a flight training school. The MNARNG uses the AASF for the tie-down 

and servicing of rotary-winged and fixed-wing aircraft. A large portion of the AASF's footprint is 

tarmac for flight operations. The infrastructure on-facility (hangar and other buildings) are used 

for storage and maintenance of ARNG property and operations, as well as administrative and 

training purposes. The AASF is bordered by the Mississippi River to the north and east, a 

combination of mixed-use commercial, office and industrial/utility land uses to the south, as well 

as a USACE flood control levy to the west (MAC, 2010). Residential areas are located northeast 

and southwest of the airport. Future land use developments are continually evaluated by the Joint 

Airport Zoning Board regarding safety zone dimensions and development restrictions. Future land 

use at the facility is not expected to change from the current land use. 

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

A wildlife survey has not occurred at the facility prior to the SI, but a habitat assessment and 

ecological risk evaluation will be performed as a part of the RI. While there are no significant areas 

of habitat on the facility, freshwater wetland areas exist near the facility, with the closest areas 

being approximately 800 feet southwest of the southwestern facility boundary, as well as 

approximately 1,700 feet to the northeast of the facility abutting the Mississippi River (US Fish 

and Wildlife Service [USFWS], 2023a). The following species have not been identified at the 

facility but may be present in the surrounding area. 

The following mollusks, insects, and mammals are federally endangered, threatened, proposed, 

and/ or are listed as candidate species in Ramsey County, Minnesota (USFWS, 2023b). 

• Mollusks: Spectaclecase (mussel), Cumberlandia monodonta (endangered); Winged

Mapleleaf, Quadrula fragosa (endangered); Higgins eye (pearlymussel), Lampsilis higginsii

(endangered); Snuffbox mussel, Epioblasma triquetra (endangered)

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

(under review); Rusty patched bumble bee, Bombus affinis (endangered)

• Mammals: Tricolored bat, Perimyotis subflavus (proposed endangered); Little brown bat,

Myotis lucifugus (under review); Northern Long-Eared Bat, Myotis septentrionalis

(endangered)

2.3 History of PFAS Use

One AOI was identified in the PA where AFFF may have been used, stored, disposed, or released 

historically at the Holman Field AASF (AECOM, 2019). 

PFAS-containing materials were potentially released to soil and groundwater within the boundary 

of Holman Field AASF through fire training exercises and storm water conveyance. The potential 
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release area was grouped into one AOI based on preliminary data and presumed groundwater 

flow directions. A description of the AOI is presented in Section 3. 
CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

10/6/2022

10/6/2022

PROJECT Site Inspection at Holman Field AASF, MN

1:31,680

10/6/2022 ­ Figure 2-1 PM CM 10/6/2022

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 0.25 0.5 1

Miles

Holman Field AASF

^_

AECOM 2-5
CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

10/6/2022

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PROJECT Site Inspection at Holman Field AASF, MN

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10/6/2022 ­ Figure 2-2 PM CM 10/6/2022

12420 Milestone Center Drive

Germantown, MD 20876

Facility Topography

Base Map: USGS The National Map: National

Boundaries Dataset, 3DEP Elevation Program,

Legend

Facility Boundary

0 250 500 1,000

Feet

AECOM 2-6
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AA!!A!

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Battle Creek

Mississippi River

Pigs Eye Lake

Thompson Lake

Lilly Lake

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

5/11/2023

5/11/2023

PROJECT Site Inspection at Holman Field AASF, MN

1:31,680

5/11/2023 ­ Figure 2-3 PM CM 5/11/2023

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

Pipeline

Groundwater Flow

Direction

Geology

Sandstone, Siltstone &

Local Conglomerate

Wells

!P Commercial

!P Domestic

!5 Industrial

A! Monitoring / Observation

/ Piezometer

A! Other/Unknown

0 0.25 0.5 1

Miles

A!

AECOM 2-7
?!

?!

?!

?!

?!

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AOI01-01

694.17

AOI01-02

695.42

AOI01-03

695.38

AOI01-04

695.39

AOI01-05

695.31 AOI01-06

694.19

St. Paul Flight Center

694.50

695.00

695.00

694.50

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

5/11/2023

5/11/2023

PROJECT Site Inspection at Holman Field AASF, MN

1:1,800

5/11/2023 ­ Figure 2-4 PM CM 5/11/2023

12420 Milestone Center Drive

Germantown, MD 20876

Groundwater Elevations,

May 2022

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

and the GIS User Community

Legend

?! SI_Sample_Location

Catch Basins

Facility Boundary

Groundwater Elevation Contour

Inferred Groundwater Elevation Contour

Groundwater Flow Direction

0 75 150 300

Feet

Groundwater elevations in ft NAVD88.

AECOM 2-8
Battle Creek

Mississippi River

Pigs Eye Lake

Thompson Lake

Lilly Lake

McCarrons

Lake

Watershed

Lake Phalen

Watershed

Harriet

Island-Mississippi

River Watershed

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

5/11/2023

5/11/2023

NOTES Site Inspection at Holman Field AASF, MN

1:31,680

5/11/2023 ­ Figure 2-5 PM CM 5/11/2023

12420 Milestone Center Drive

Germantown, MD 20876

Surface Water Features

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

and the GIS User Community

Legend

Facility Boundary

Water Body

Wetland

River/Stream

Canal/Ditch

Pipeline

Surface Water Flow Direction

0 0.25 0.5 1

Miles

AECOM 2-9
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 2-10

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 3-1

3. Summary of Areas of Interest

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

disposed, or released historically. Based on the PA findings, one potential release area was

identified at the facility [Holman Field AASF] and grouped into one AOI (AECOM, 2019). The 

potential release areas are shown on Figure 3-1. 

3.1 AOI 1 South Hanger Ramp and Fire Truck Storage Area

AOI 1 is the South Hangar Ramp and Fire Truck Storage Area. One potential release of AFFF 

occurred in October 2013, when the Tri-MaxTM fire extinguishers were emptied on the east side 

of the South Hangar Ramp by the MNARNG prior to being returned to Camp Ripley for 

demilitarization. In total, approximately 12 gallons of AFFF concentrate were released during this 

event. Additionally, an AFFF-capable firetruck was stored in the northeast corner of the facility 

building from 1987 to 1989. Site personnel indicated AFFF concentrate was transferred to the fire 

truck by pouring AFFF from 5-gallon containers into the tanks. No spills were noted. In addition, 

the former Fire Marshall indicated the firetruck did not have maintenance issues and was never 

used for emergency response or training. The nozzles on the firetruck were tested using water 

only; the proportioning valve was never tested. Periodically, the firetruck was washed in the 

hangar at the indoor wash rack. Water from the indoor wash rack drains to the oil water separator 

and then to the sanitary sewage. 

3.2 Adjacent Sources

One off-facility, potential source was identified adjacent to the AASF during the PA and are not 

associated with ARNG activities. The adjacent potential sources are shown on Figure 3-1 and 

described in the following sections for informational purposes only and will not be investigated as 

part of this SI. 

3.2.1 St. Paul Downtown Airport 

The St. Paul Downtown Airport was constructed in 1926 and is owned and operated by the MAC. 

The AASF is southwest and adjacent to the St. Paul Downtown Airport. The St. Paul Downtown 

Airport is one of several reliever airports in the Twin Cities and consists of several private hangars, 

including hangars for the 3M Company, and the St. Paul Flight Center. The City of St. Paul Fire 

Department provides fire emergency services for the St. Paul Downtown Airport. Based on the

interview with the City of St. Paul Fire Chief’s, none of the hangars at the St. Paul Downtown 

Airport contain AFFF fire suppression systems, and AFFF has not been dispensed at the Holman 

Field Complex, including the AASF. 

3.2.2 Upgradient Sources

Several additional sources of PFAS in the St. Paul area, not adjacent to the AASF facility, were 

identified in a report by Delta Consultants titled Perfluorocarbon (PFC)-Containing Firefighting 

Foams And Their Use In Minnesota. These sources include a 3M Company plant, the 

Minneapolis-St. Paul International Airport / Minneapolis–Saint Paul Joint Air Reserve Station, 

refineries, marina fire locations, and landfills. The AASF is downgradient of these additional 

sources of PFAS; therefore, PFAS use at these locations could potentially impact the AASF.
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 3-2

THIS PAGE INTENTIONALLY BLANK
!P

!5

A!

AOI 1

South Hangar Ramp

Fire Truck Storage Area

Mississippi River

Harriet

Island-Mississippi

River Watershed

3M Hangars

St. Paul Flight Center

St. Paul Downtown Airport

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

5/11/2023

5/11/2023

NOTES Site Inspection at Holman Field AASF, MN

1:7,200

5/11/2023 ­ Figure 3-1 PM CM 5/11/2023

12420 Milestone Center Drive

Germantown, MD 20876

Area of Interest

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

and the GIS User Community

Legend

Area of Interest

Potential Release Area

Facility Boundary

Water Body

Wetland

Surface Water Flow

Direction

Groundwater Flow

Direction

!P Domestic Well

!5 Industrial Well

A! Monitoring / Observation /

Piezometer Well

0 300 600 1,200

Feet

AECOM 3-3
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 3-4

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Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 4-1

4. Project Data Quality Objectives

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

Assurance Project Plan (QAPP) Addendum (AECOM, 2022a), the objective of the SI is to identify 

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

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

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

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

AOIs.

4.1 Problem Statement

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

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

SLs are presented in Section 6.1 of this report. 

4.2 Information Inputs

Primary information inputs included:

• The PA for Holman Field AASF (AECOM, 2019);

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

with the site-specific Uniform Federal Policy (UFP)-QAPP Addendum (AECOM, 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 15 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 Department of 

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

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

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

as defined in the SI QAPP Addendum (AECOM, 2022a). 

4.5 Data Usability Assessment

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

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

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

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

installation-specific DQOs. Both sampling and analytical activities are considered to assess 
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 4-2

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

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

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

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

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

Holman Field Army Aviation Support Facility, St. Paul, 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, Holman Field Army Aviation Support Facility, St.

Paul, Minnesota dated November 2019 (AECOM, 2019);

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

Holman Field Army Aviation Support Facility, St. Paul, Minnesota dated March 2022

(AECOM, 2022a); and

• Final Site Safety and Health Plan, Holman Field Army Aviation Support Facility, St. Paul,

Minnesota dated May 2022 (AECOM, 2022b).

The SI field activities were conducted from 23 to 25 May 2022 and consisted of utility clearance,

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

sample collection, and land surveying. Field activities were conducted in accordance with the SI 

QAPP Addendum (AECOM, 2022a). 

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

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

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

• Fifteen (15) soil samples from six boring locations;

• Six grab groundwater samples from six temporary wells;

• Fourteen (14) quality assurance (QA)/quality control (QC) samples.

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

list of samples collected for each media. Field documentation is provided in Appendix B. A Log 

of Daily Notice of Field Activity was completed throughout the SI field activities, which is provided 

in Appendix B1. Sampling forms are provided in Appendix B2, and land survey data are

provided in Appendix B3. Additionally, a photographic log of field activities is provided in 

Appendix C. 

5.1 Pre-Investigation Activities

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

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

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

5.1.1 Technical Project Planning

The USACE TPP Process, Engineer Manual (EM) 200-1-2 (USACE, 2016) defines four phases 

to project planning: 1.) defining the project phase; 2.) determining data needs; 3.) developing data 

collection strategies; and 4.) finalizing the data collection plan. The process encourages 

stakeholder involvement in the SI, beginning with defining overall project objectives, including 

DQOs, and formulating a sampling approach to address the AOIs identified in the PA. 
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 5-2

A combined TPP Meeting 1 and 2 was held on 8 September 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, MNARNG, USACE, MAC, Minnesota Pollution Control 

Agency, and Stantec. 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, 

202a). A TPP Meeting 3 was held on (date TBD) after the field event to discuss the results of the 

SI. Meeting minutes for TPP 3 are included in Appendix D of this report. Future TPP meetings 

will provide an opportunity to discuss the results and findings, and future actions, where 

warranted. 

5.1.2 Utility Clearance 

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

north 811 “Call Before You Dig” utility clearance provider to notify them of intrusive work on 17

May 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 23 May 2022 with input from the AECOM field team and Holman 

Field AASF 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 Holman Field AASF was sampled on 12 January 2022 to assess 

usability for decontamination of drilling equipment. Results of the sample collected at the North 

Hanger Bay spigot (HF-DECON-01) confirmed this source to be acceptable for use in this

investigation; therefore, it was used throughout the field activities. Specifically, the samples were 

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

water sample associated with the wash rack spigot source used during the SI are provided in 

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

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

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

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

(AECOM, 2022a). Prior to the start of field work each day, a Sampling Checklist was completed 

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

member regarding the allowable materials within the sampling environment. 

5.2 Soil Borings and Soil Sampling

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

surfaces. Soil samples were collected via direct push technology (DPT), in accordance with the 

SI QAPP Addendum (AECOM, 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 5 feet of the boring, in accordance with AECOM utility clearance procedures. The 

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

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

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

approximately 2 feet above the groundwater table, and one subsurface soil sample at the midpoint between the surface and the groundwater table. 
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 5-3

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

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

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

Observations and measurements were recorded on boring logs (Appendix E) and in a 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, poorly graded and well-graded sands were observed as the dominant lithology of 

the unconsolidated sediments in soil borings drilled at the facility. The borings were completed at 

depths between 10 and 15 feet bgs. Varying quantities of low to medium plasticity fines (silts and 

clay) were noted, specifically, isolated layers of silt with sand, silty lean clay, lean clay, clayey silt, 

sandy silt, and poorly graded sand with silt. These layers ranged in thickness from a few inches 

to 5 feet. Many of the logs also reported varying percentages of gravel included in the sand 

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

the region.

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

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

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

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

carbon (TOC) (USEPA Method 9060A), 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, which were subsequently abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2022a) using bentonite chips at completion 

of sampling activities.

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 using either 

5-foot or 10-foot sections of 1-inch Schedule 40 poly-vinyl chloride (PVC) screen with sufficient

casing to reach ground surface. The temporary wells were installed in direct contact with the

native material; filter sand or other well construction material was not used in the construction of

the temporary wells. New PVC pipe and screen were used to avoid cross contamination between

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

Groundwater samples were collected after a period of time 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, DO, and 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. 
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 5-4

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 5.5), temporary wells were abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2022a) by removing the PVC and backfilling 

the hole with neat cement grout. Upon completion of well abandonment, the ground surface at 

each location was patched to match existing surrounding conditions.

5.4 Synoptic Water Level Measurements

A synoptic groundwater gauging event was performed on 25 May 2022. Groundwater elevation 

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

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

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

5.5 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 on 25 May 2022 in the 

applicable Universal Transverse Mercator zone projection with Minnesota Coordinate System of 

1983 (CCS83) datum (horizontal) and North American Vertical Datum 1988 (vertical). The 

surveyed well data are provided in Appendix B3. 

5.6 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). However, due to the proximity to facility operations, ARNG and MNARNG agreed to 

containerize all soil and liquid IDW generated during the SI activities. 

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

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

storage area. The soil IDW was not sampled and assumes the PFAS characteristics of the 

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

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

where PFAS concentrations are below the Industrial/Commercial Composite Worker OSD SLs, 

ARNG will distribute the soil on the downgradient side of the associated borehole. 

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

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

onsite in a designated waste storage area. The liquid IDW was not sampled and assumes the 

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

Additionally, petroleum impacts (i.e., sheening and odor) were observed in the purge water from 

temporary well AOI01-06. The liquid IDW from this location was segregated and containerized in 
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 5-5

a separate 55-gallon drum and stored in the northern portion of the hanger exterior. Containerized 

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

with treatment, as appropriate) under a separate contract in accordance with SOP No. 042A (EA, 

2021). ARNG will further manage liquid IDW in accordance with the Army Guidance for 

Addressing Releases of PFAS, Q18 (DA, 2018). ARNG will coordinate transportation and disposal 

of the liquid IDW. 

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

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

activities were disposed of at a licensed solid waste landfill.

5.7 Laboratory Analytical Methods

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

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

were also analyzed for TOC using USEPA Method 9060A and pH by USEPA Method 9045D. 
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 5-6

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Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Holman Field AASF, Minnesota

Sample Identification

Sample

Collection 

Date/Time

Sample 

Depth 

(feet bgs)

LC/MS/MS compliant with QSM 5.3 Table B-15TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

AOI01-01-SB-00-02 5/24/2022 12:05 0-2 x

AOI01-01-SB-00-02-D 5/24/2022 12:05 0-2 x FD

AOI01-01-SB-00-02-MS 5/24/2022 12:05 0-2 x MS

AOI01-01-SB-00-02-MSD 5/24/2022 12:05 0-2 x MSD

AOI01-01-SB-03-05 5/24/2022 12:25 3-5 x x x x

AOI01-01-SB-03-05-D 5/24/2022 12:25 3-5 x x FD

AOI01-01-SB-03-05-MS 5/24/2022 12:25 3-5 x x MS

AOI01-01-SB-03-05-MSD 5/24/2022 12:25 3-5 x x MSD

AOI01-01-SB-05-07 5/24/2022 12:45 5-7 x

AOI01-02-SB-00-02 5/24/2022 9:00 0-2 x

AOI01-02-SB-05-07 5/24/2022 9:10 5-7 x

AOI01-02-SB-05-07-D 5/24/2022 9:10 5-7 x FD

AOI01-02-SB-07-09 5/24/2022 9:15 7-9 x

AOI01-03-SB-00-02 5/24/2022 10:30 0-2 x

AOI01-03-SB-03-05 5/24/2022 10:35 3-5 x

AOI01-04-SB-00-02 5/24/2022 11:15 0-2 x

AOI01-04-SB-03-04 5/24/2022 11:30 3-4 x

AOI01-05-SB-00-02 5/24/2022 13:40 0-2 x

AOI01-05-SB-02-03 5/24/2022 13:45 2-3 x

AOI01-06-SB-00-02 5/24/2022 14:55 0-2 x

AOI01-06-SB-04-06 5/24/2022 15:15 4-6 x

AOI01-06-SB-08-10 5/24/2022 15:25 8-10 x

Soil Samples

AECOM 5-7
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Holman Field AASF, Minnesota

Sample Identification

Sample

Collection 

Date/Time

Sample 

Depth 

(feet bgs)

LC/MS/MS compliant with QSM 5.3 Table B-15TOC(USEPA Method 9060A)pH (USEPA Method 9045D)Grain Size (ASTM D-422)

Comments

AOI01-01-GW 5/25/2022 13:45 NA x

AOI01-01-GW-D 5/25/2022 13:45 NA x FD

AOI01-01-GW-MS 5/25/2022 13:45 NA x MS

AOI01-01-GW-MSD 5/25/2022 13:45 NA x MSD

AOI01-02-GW 5/25/2022 12:30 NA x

AOI01-03-GW 5/25/2022 16:10 NA x

AOI01-04-GW 5/25/2022 15:25 NA x

AOI01-05-GW 5/25/2022 14:25 NA x

AOI01-06-GW 5/25/2022 10:30 NA x

HF-ERB-01 5/24/2022 9:55 NA x From HA

HF-ERB-02 5/24/2022 13:00 NA x From DPT Shoe

HF-FRB-01 5/24/2022 15:45 NA x

HF-DECON-01 1/12/2022 12:42 NA x

Notes:

ASTM = American Society for Testing and Materials

bgs = below ground surface

DPT = direct push technology

ERB = equipment rinsate blank

FD = field duplicate

FRB = field reagent blank

GW = groundwater

HA = hand auger

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

NA = not applicable

pH = potential of hydrogen

QSM = Quality Systems Manual

SB = soil boring

SS = surface soil

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

Quality Control Samples

Groundwater Samples

AECOM 5-8
Table 5-2

Soil Boring Depths, Temporary Well Screen Intervals, and Groundwater Elevations

Site Inspection Report, Holman Field AASF, 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 

Water

(feet btoc)

Depth to 

Water

(feet bgs)

Groundwater 

Elevation

(feet NAVD88)

AOI01-01 15 8-13 700.733 700.829 6.56 6.66 694.17

AOI01-02 15 9-14 701.450 701.423 6.03 6.00 695.42

AOI01-03 10 5-10 700.684 700.607 5.30 5.22 695.38

AOI01-04 10 5-10 700.372 700.406 4.98 5.01 695.39

AOI01-05 10 5-10 699.059 699.141 3.75 3.83 695.31

AOI01-06 15 10-15 701.324 701.303 7.13 7.11 694.19

Notes:

bgs = below ground surface

btoc = below top of casing

NAVD88 = North American Vertical Datum 1988

1

AECOM 5-9
AECOM 5-10

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M 5-10
?!

?!

?!

?!

?!

?!

AOI 1

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

GR

5/11/2023

5/11/2023

PROJECT Site Inspection at Holman Field AASF, MN

1:1,800

5/11/2023 ­ Figure 5-1 PM CM 5/11/2023

12420 Milestone Center Drive

Germantown, MD 20876

Site Inspection Sample Locations

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

and the GIS User Community

Legend

?! Soil Boring/Temporary Monitoring Well

Catch Basins

Area of Interest

Facility Boundary

Surface Water Flow Direction

Groundwater Flow Direction

0 75 150 300

Feet

AECOM 5-11
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 5-12

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Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, 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 theAOI is provided in Section 6.3 through 

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

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

are provided in Appendix G. 

6.1 Screening Levels

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

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

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

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

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

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

6-1 below.

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

Analyteb

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ 

Commercial 

Composite 

Worker

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater)

(ng/L)a

PFOA 19 250 6 

PFOS 13 160 4

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6 

Notes:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 6-2

6.2 Soil Physicochemical Analyses

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

size, which are important for evaluating transport through the soil medium. Appendix F contains 

the results of the TOC, pH, and grain size sampling. 

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

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

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

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

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

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

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

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

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

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

6.3 AOI 1 

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

AOI 1: South Hanger Ramp and Fire Truck Storage Area. The soil and groundwater results are 

summarized on Table 6-2 through Table 6-4. Soil and groundwater results are presented on 

Figure 6-1 through Figure 6-7. 

6.3.1 AOI 1 Soil Analytical Results

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

6-3 summarize the soil results.

Surface soil was sampled from 0 to 2 feet bgs at boring locations AOI01-01 through AOI01-06. 

Soil was also sampled at all six locations from two shallow subsurface intervals between 2 to 10

feet bgs). Deeper subsurface soil was not sampled at borings AOI01-03, AOI01-04, and AOI01-

05 due to groundwater being shallower than 15 feet bgs at all locations. On Figures 6-1 through 

6-5, the two shallow subsurface sampling zones are labeled ‘intermediate’ and ‘deep.’

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

the six locations, with the highest concentration of 3.54 μg/kg occurring at AOI01-03. PFHxS, 

PFNA, and PFBS were detected in surface soil at concentrations several orders of magnitude 

lower than their SLs at all locations. PFOA was not detected in surface soil.

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

concentrations several orders of magnitude lower than their SLs at all six locations. 

6.3.2 AOI 1 Groundwater Analytical Results 

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

summarizes the groundwater results. 

Groundwater was sampled from temporary monitoring wells AOI01-01 through AOI01-06. PFNA 

and PFBS were detected below their SLs of 6 ng/L and 601 ng/L, respectively, in all six wells.

The following exceedances of the SLs for PFOA, PFOS, and PFHxS were measured:

• PFOA was detected above the SL of 6 nanograms per liter (ng/L) in four of the six wells,

with concentrations ranging from 7.71 ng/L at AOI01-02 to 103 J- ng/L at location AOI01-

01.
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 6-3

• PFOS was detected above the SL of 4 ng/L in the six wells with concentrations ranging

from of 9.65 ng/L at AOI01-06 to 37.3 ng/L at location AOI01-03.

• PFHxS was detected above the SL of 39 ng/L in two of the six wells, with concentrations

of 239 J- ng/L at AOI01-01 and 69.7 ng/L at AOI01-02.

6.3.3 AOI 1 Conclusions

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

below their SLs. PFOA, PFOS, and PFHxS were detected in groundwater at concentrations above 

their SLs. Based on the exceedances of the SLs in groundwater, further evaluation at AOI 1 is 

warranted. 
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 6-4

THIS PAGE INTENTIONALLY BLANK
Table 6-2

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

Site Inspection Report, Holman Field AASF

Analyte OSD Screening 

Level a

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

PFBS 1900 ND U ND U ND U ND U ND U ND U 0.027 JPFHxS 130 ND U ND U ND U ND U ND U ND U 0.191 JPFNA 19 ND UJ 0.021 J ND U ND U ND U 0.044 J 0.024 JPFOA 19 ND U ND U ND U ND U ND U ND U ND UPFOS 13 0.638 J+ 1.19 J+ 0.091 J 3.54 ND U ND U 0.817 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 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

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

05/24/2022

0-2 ft

05/24/2022

0-2 ft

AOI01-02-SB-00-02

05/24/2022

0-2 ft

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

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidential ingestion of contaminated soil.

AOI01

AOI01-05-SB-00-02

05/24/2022

0-2 ft

AOI01-06-SB-00-02

05/24/2022

0-2 ft

AOI01-03-SB-00-02

05/24/2022

0-2 ft

AOI01-04-SB-00-02

05/24/2022

0-2 ft

AOI01-01-SB-00-02-D

AECOM 
Table 6-3

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

Site Inspection Report, Holman Field AASF

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Re

PFBS 25000 ND U ND U ND U ND U ND U ND U ND U ND U 0.043 PFHxS 1600 0.562 J 0.560 J ND UJ 0.039 J 0.041 J 0.093 J ND U 0.036 J 0.035 PFNA 250 ND U ND U ND UJ 0.032 J 0.031 J ND U ND U 0.108 J ND PFOA 250 ND U ND U ND U ND U ND U ND U ND U 0.109 J ND PFOS 160 0.137 J 0.284 J 0.359 J 0.553 J 0.876 J 0.336 J ND U 0.201 J 0.063 

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 duplicateDL detection limitft feetHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem LOD 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 Protecμg/kg micrograms per kilogram

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-03-05

05/24/2022

3-5 ft

AOI01-01-SB-05-07

05/24/2022

5-7 ft

AOI01-02-SB-05-07

05/24/2022

5-7 ft

05/24/2022

3-4 ft

AOI01-02-SB-05-07-D

05/24/2022

5-7 ft

AOI01-02-SB-07-09

05/24/2022

7-9 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental ingestion of contaminated soil.

AOI01

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

AOI01-05-SB-02-03

05/24/2022

2-3 ft

AOI

AOI01-03-SB-03-05

05/24/2022

3-5 ft

AOI01-04-SB-03-04

AECOM 
Table 6-4

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

Site Inspection Report, Holman Field AASF

Analyte OSD Screening 

Level a

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

PFBS 601 25.8 21.9 2.05 J 1.78 J 1.14 J 2.34 J 3.00 JPFHxS 39 239 J- 197 J- 69.7 14.4 7.02 26.4 25.3

PFNA 6 1.14 J ND UJ ND U 4.21 ND U 1.86 J ND UPFOA 6 103 J- 86.6 J- 7.71 12.0 5.69 10.5 4.18

PFOS 4 33.7 27.3 33.1 37.3 20.3 21.4 9.65

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 low 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

GW groundwaterHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem LOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Protecng/l nanogram per liter

Sample ID

Sample Date

AOI01-01-GW

05/24/2022

Water, LCMSMS compliant with QSM 5.3 Table B-15 (ng/l)

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI01

AOI01-05-GW

05/24/2022

AOI01-06-GW

05/24/2022

AOI01-03-GW

05/24/2022

AOI01-04-GW

05/24/2022

AOI01-01-GW-D

05/24/2022

AOI01-02-GW

05/24/2022

Area of Interest

AECOM 
AECOM 5-10

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M 6-8
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 100 200 400

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

AOI01-01

AOI01-02

AOI01-06

Shallow Intermediate Deep

­ Figure 6-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/3/2023

5/3/2023

5/3/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/3/2023

1:2,400

Legend

Catch Basins

Facility Boundary

PFOA Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

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

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

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-9
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 100 200 400

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

AOI01-01

AOI01-02

AOI01-06

Shallow Intermediate Deep

­ Figure 6-2

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/3/2023

5/3/2023

5/3/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/3/2023

1:2,400

Legend

Catch Basins

Facility Boundary

PFOS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

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

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

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

AECOM 6-10
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 100 200 400

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

AOI01-01

AOI01-02

AOI01-06

Shallow Intermediate Deep

­ Figure 6-3

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/3/2023

5/3/2023

5/3/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/3/2023

1:2,400

Legend

Catch Basins

Facility Boundary

PFBS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

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

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

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

AECOM 6-11
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 100 200 400

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

AOI01-01

AOI01-02

AOI01-06

Shallow Intermediate Deep

­ Figure 6-4

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/3/2023

5/3/2023

5/3/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/3/2023

1:2,400

Legend

Catch Basins

Facility Boundary

PFHxS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

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

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

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

AECOM 6-12
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 100 200 400

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

AOI01-01

AOI01-02

AOI01-06

Shallow Intermediate Deep

­ Figure 6-5

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/3/2023

5/3/2023

5/3/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/3/2023

1:2,400

Legend

Catch Basins

Facility Boundary

PFNA Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

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

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

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-13
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 100 200 400

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

PFOA PFOS PFBS

­ Figure 6-6

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/11/2023

5/11/2023

5/11/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/11/2023

1:2,400

Legend

Catch Basins

Facility Boundary

Groundwater Flow Direction

Surface Water Flow Direction

PFOA, PFOS, and PFBS Detections in Groundwater

12420 Milestone Center Drive

Germantown, MD 20876

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

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

AECOM 6-14
AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

0 75 150 300

Feet

AOI01-01

AOI01-02

AOI01-03

AOI01-04

AOI01-05

AOI01-06

PFHxS PFNA

­ Figure 6-7

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Holman Field AASF, MN

5/11/2023

5/11/2023

5/11/2023

MS

GR

CM

GIS BY

CHK BY

PM

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

5/11/2023

1:1,800

Legend

Catch Basins

Facility Boundary

Groundwater Flow Direction

Surface Water Flow Direction

PFHxS and PFNA Detections in Groundwater

12420 Milestone Center Drive

Germantown, MD 20876

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

PFHxS Results (ng/L)

ND

>ND - 39

>39 - 100

>100 - 1,000

>1,000

PFNA Results (ng/L)

ND

>ND - 6

>6 - 100

>100 - 1,000

>1,000

AECOM 6-15
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6-16
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 7-1

7. Exposure Pathways

The CSM for AOI 1, revised based on the SI findings, is presented on Figure 7-1. Please note 

that while the CSM discussion assists in determining if a receptor may be impacted, the decision 

to move from SI to RI or interim action is determined based upon exceedances of the SLs for the 

relevant compounds and whether the release is more than likely attributable to the DoD. A CSM 

presents the current understanding of the site conditions with respect to known and suspected 

sources, potential transport mechanisms and migration pathways, and potentially exposed human 

receptors. A human exposure pathway is considered potentially complete when the following 

conditions are present:

1. Contaminant source;

2. Environmental fate and transport;

3. Exposure point;

4. Exposure route; and

5. Potentially exposed populations.

If any of these elements are missing, the pathway is incomplete. The CSM figures use an empty 

circle symbol to represent an incomplete exposure pathway. Areas with an incomplete pathway 

generally warrant no further action. However, the pathway is considered potentially complete if the 

relevant compounds are detected, in which case the CSM figure uses a half-filled circle symbol to 

represent a potentially complete exposure pathway. Additionally, a completely filled circle symbol is 

used to indicate when a potentially complete exposure pathway has detections of relevant 

compounds above the SLs. Areas with an identified potentially complete pathway that have 

detections of the relevant compounds above the SLs may warrant further investigation. Although 

the CSMs indicate whether potentially complete exposure pathways may exist, the 

recommendation for future study in a RI or no action at this time is based on the comparison of 

the SI analytical results for the relevant compounds to the SLs.

In general, the potential routes of exposure to the relevant compounds are ingestion and 

inhalation. Human exposure via the dermal contact pathway may occur, and current risk practice 

suggests it is an insignificant pathway compared to ingestion; however, exposure data for dermal 

pathways are sparse and continue to be the subject of toxicological study. The receptors 

evaluated are consistent with those listed in USEPA guidance for risk screening (USEPA, 2001). 

Receptors at the facility include site workers (e.g., facility staff and visiting soldiers), construction 

workers, trespassers (though unlikely due to restricted access), residents outside the facility 

boundary, and recreational users outside of the facility boundary. 

7.1 Soil Exposure Pathway

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

between the source and potential receptors at AOI 1 based on the aforementioned criteria. 

7.1.1 AOI 1 

AOI 1 is the South Hanger Ramp and Fire Truck Storage Area where one potential release of 

AFFF occurred in October 2013 when the Tri-MaxTM fire extinguishers were emptied on the east 

side of the South Hangar Ramp by the MNARNG prior to being returned to Camp Ripley for 

demilitarization. In total, approximately 12 gallons of AFFF concentrate were released during this 

event.
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 7-2

Relevant compounds were detected in surface soil at AOI 1. Site workers, construction workers, 

and trespassers (though unlikely due to restricted access) could contact constituents in surface 

soil via incidental ingestion and inhalation of dust. Therefore, the surface soil exposure pathway 

for site workers and construction workers are potentially complete. 

Relevant compounds were detected in subsurface soil at AOI 1. Construction workers could 

contact constituents in subsurface soil via incidental ingestion, and therefore, the subsurface soil 

exposure pathway for construction workers is potentially complete. The CSM for AOI 1 is 

presented on Figure 7-1. 

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, and PFHxS were detected above their SLs in groundwater samples collected at 

AOI 1. Due to the presence of public water system wells within a 4-mile radius of the facility, the 

pathway for exposure to off-facility residents via ingestion of groundwater is considered potentially 

complete. No potable water wells are located within the boundary of the AASF. Several 

monitoring, commercial, and industrial wells are within 4 miles of the facility, and one domestic 

well is located less than 0.5 miles due north of the facility. Drinking water for the AASF is supplied 

by the City of St. Paul, which obtains its municipal water through the Saint Paul Regional Water 

Services. The Saint Paul Regional Water Services predominantly uses the Mississippi River as 

its drinking water source, although some water is supplied by groundwater aquifers. The 

Mississippi River surface water intakes are located upgradient of the facility, approximately 18 

miles north near Fridley, Minnesota; therefore, the pathway for exposure to site workers and 

trespassers (though unlikely due to restricted access) via ingestion of groundwater is considered 

incomplete. Depths to water measured at AOI 1 in May 2022 during the SI ranged from 3.83 to 

7.11 feet bgs. Therefore, the ingestion exposure pathway for current and future construction 

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

7.3 Surface Water and Sediment Exposure Pathway

Surface water and sediment samples were not collected at AOI 1, however, data from 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. PFAS are water soluble and can migrate readily from soil to 

surface water via leaching and run-off. There are no surface water bodies located within the 

facility; therefore, the surface water and sediment ingestion exposure pathway for site workers, 

construction workers, and trespassers (though unlikely due to restricted access) is considered 

incomplete. Because relevant compounds were detected in soil and groundwater at AOI 1, it is 

possible that those compounds may have migrated from soil and groundwater to the canal/ditch

to the southwest of the facility via groundwater discharge. Due to potential recreational use of the 

canal/ditch, the surface water and sediment ingestion exposure pathway for off-facility residents 

and recreational users is also considered potentially complete.
Media

SOURCE PATHWAY RE

AOI 1

Fire Training and 

Mobile Fire 

Extinguishers 

Discharge

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 Transport and Migration Media Exposure Routes

Inhalation of 

dust

Ingestion

Ingestion

Ingestion

Ingestion

Hum

C

Flow-Chart ContinuesPartial/ Possible FlowFlow-Chart StopsIncomplete PathwayPotentially Complete PathwayPotentially Complete Pathway with Exceedance of SL

/ 

Site 

Worker

Cons

Wo

Site 

Worker

Cons

Wo

/ 

/ 

/ / 

LEGEND

Figure 

Conceptual Site M

Holman Field AASF, St

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

1. The resident and recreational users refer to offsite receptors.2. Inhalation of dust for off-site receptors is likelyinsignificant.3. No current active construction at the facility.Notes:

/ 

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M 7-4
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, 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 23 to 25 May 2022 and consisted of utility clearance, 

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

sample collection, and land surveying. Field activities were conducted in accordance with the SI 

QAPP Addendum (AECOM, 2022a). 

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

were collected and analyzed for a subset of 18 compounds by LC/MS/MS compliant with QSM 5.3 

Table B-15 as follows. 

• Fifteen (15) soil samples from six boring locations;

• Six grab groundwater samples from six temporary wells;

• Fourteen (14) 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 AOI 1 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 CSM were refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at AOI 1, 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

(see Table 8-1). Based on the CSM developed and revised in light of the SI findings, there is 

potential for exposure to drinking water receptors from AOI 1 from sources on the facility resulting 

from historical DoD activities. Sample analytical concentrations collected during the SI were 

compared to the project SLs in soil and groundwater, as described in Table 6-1. A summary of 

the results of the SI data relative to the SLs is as follows: 

• At AOI 1:

• The detected concentrations of relevant compounds in soil at AOI 1 were below their

SLs.

• PFOA, PFOS, and PFHxS in groundwater exceeded their SLs. PFOA exceeded the

SL of 6 ng/L, with a maximum concentration of 103 J- ng/L at location AOI01-01.

PFOS exceeded the SL of 4 ng/L, with a maximum concentration of 37.3 ng/L at

location AOI01-03. PFHxS exceeded the SL of 39 ng/L, with a maximum

concentration of 239 J- ng/L at location AOI01-01. Based on the results of the SI,

further evaluation of AOI 1 is warranted in an RI.

Of the six PFAS compounds presented in the 6 July 2022 OSD memorandum, HFPO-DA 

(commonly referred to as GenX) was not included as an analyte at the time of this SI. Based on 
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Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 8-2

the CSM developed during the PA and revised based on SI findings, the presence of HFPO-DA 

is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC 

AFFF and based on its history including distribution limitations that restricted use of GenX, it is 

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

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

Table 8-1 summarizes the SI results for soil and groundwater used to determine if an AOI should 

be considered for further investigation under CERCLA and undergo an RI. 

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

AOI Potential 

Release Area

Soil –

Source 

Area

Groundwater – 

Source Area

Groundwater – 

Facility Boundary

Future 

Action

1 

South Hanger 

Ramp and Fire 

Truck Storage 

Area

Proceed 

to RI 

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 9-1

9. References

AECOM. 2018a. Final Site Inspection Programmatic Uniform Federal Policy-Quality Assurance 

Project Plan, Perfluorooctane Sulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA) 

Impacted Sites ARNG Installations, Nationwide Contract No. W912DR-12-D-0014/

W912DR17F0192. 9 March.

AECOM. 2018b. Final Programmatic Accident Prevention Plan, Perfluorooctane Sulfonic Acid 

(PFOS) and Perfluorooctanoic Acid (PFOA) Impacted Sites ARNG Installations, Nationwide 

Contract No. W912DR-12-D-0014/W912DR17F0192. July.

AECOM. 2019. Final Preliminary Assessment Report, Holman Field Army Aviation Support 

Facility, Minnesota. November. 

AECOM. 2022a. Final Site Inspection Uniform Federal Policy-Quality Assurance Project Plan 

Addendum, Holman Field Army Aviation Support Facility, St. Paul, Minnesota, Perfluorooctane 

Sulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA) Impacted Sites ARNG Installations, 

Nationwide. March. 

AECOM. 2022b. Final Site Safety and Health Plan, Holman Field Army Aviation Support Facility, 

St. Paul, Minnesota, Perfluorooctane Sulfonic Acid (PFOS) and Perfluorooctanoic Acid 

(PFOA) Impacted Sites ARNG Installations, Nationwide. May. 

Assistant Secretary of Defense. 2022. Investigation Per- and Polyfluoroalkyl Substances within 

the Department of Defense Cleanup Program. United States Department of Defense. 

6 July. 

DA. 2018. Army Guidance for Addressing Releases of Per- and Polyfluoroalkyl Substances.

4 September.

DoD. 2019a. Department of Defense (DoD), Department of Energy (DOE) Consolidated Quality 

Systems Manual (QSM) for Environmental Laboratories, Version 5.3. 

DoD. 2019b. General Data Validation Guidelines. Environmental Data Quality Workgroup. 

4 November.

EA Engineering, Science, and Technology, Inc. 2021. Standard Operating Procedure No. 042A 

for Treating Liquid Investigation-Derived Material (purge water, drilling water, and 

decontamination fluids). Revision 1. March.

Guelfo, J.L. and Higgins, C.P. 2013. Subsurface Transport Potential of Perfluoroalkyl Acids at 

Aqueous Film-Forming Foam (AFFF)-Impacted Sites. Environmental Science and Technology 

47(9): 4164-71.

Higgins, C.P., and Luthy, R.G. 2006. Sorption of perfluorinated surfactants on 

sediments. Environmental Science and Technology 40 (23): 7251-7256.

ITRC. 2018. Environmental Fate and Transport for Per- and Polyfluoroalkyl Substances. March. 

Metropolitan Airports Commission (MAC). 2010. St. Paul Downtown Airport (STP) Long-Term 

Comprehensive Plan. June.

USACE. 2016. Technical Project Planning Process, EM-200-1-2. 26 February.

USEPA. 1980. Comprehensive Environmental Response, Compensation, and Liability Act 

(CERCLA). 
Site Inspection Report

Holman Field Army Aviation Support Facility, St. Paul, Minnesota

AECOM 9-2

USEPA. 1994. National Oil and Hazardous Substances Pollution Contingency Plan (Final Rule). 

40 CFR Part 300; 59 Federal Register 47384. September.

USEPA. 2001. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation 

Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk 

Assessments). December.

USEPA. 2014. Management of Investigation Derived Waste. SESD Operating Procedure. 

SESDPROC-202-R3. July. 

USEPA. 2017. National Functional Guidelines for Organic Superfund Data Review. OLEM 

9355.0-136, EPA-540-R-2017-002. Office of Superfund Remediation and Technology 

Innovation. January.

USFWS. 2023a. National Wetlands Inventory: Wetlands Mapper. Accessed 9 May 2023 at 

https://fwsprimary.wim.usgs.gov/wetlands/apps/wetlands-mapper/. 

USFWS. 2023b. Species by County Report, County: Ramsey, Minnesota. Environmental 

Conservation Online System. Accessed 12 January 2023 at 

https://ecos.fws.gov/ecp/report/species-listings-by-current-range-county?fips=27123

World Climate. 2022. Average Weather Data for Saint Paul, Minnesota. Available at 

http://www.worldclimate.com/climate/us/minnesota/saint-paul (Accessed 27 December

2022).

WSB & Associates, Inc. 2011. Watershed Management Plan. August.

Xiao, F., Simcik, M. F., Halbach, T. R., and Gulliver, J. S. 2015, Perfluorooctane sulfonate (PFOS) 

and perfluorooctanoate (PFOA) in soils and groundwater of a U.S. metropolitan area: 

Migration and implications for human exposure. Water Research 72: 64-74.