FINAL

Site Inspection Report 

Former Chicago Midway Army 

Aviation Support Facility

Chicago, Illinois

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 

July 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....................................................................................................................... 3-1

3.1.1 Fire Extinguisher FTA................................................................................... 3-1

3.1.2 Ramp Area.................................................................................................... 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

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

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

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

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

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

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

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

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

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

7.3.1 AOI 1 ............................................................................................................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. Field Change Request Forms

B4. Survey Data

B5. Investigation-Derived Waste Polygon

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, March 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 

Table 5-2 

Site Inspection Samples by Medium

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

bgs below ground surface 

CAWS Chicago Area Waterway System

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

DPT direct push technology

DQO data quality objective

DUA data usability assessment

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

FAA Federal Aviation Administration

FBO Fixed Base Operator

FTA Fire Training Area

GPRS Ground Penetrating Radar Systems, LLC.

GPS Global positioning system

HDPE high-density polyethylene 

HFPO-DA hexafluoropropylene oxide dimer acid

IDW investigation-derived waste

ILARNG Illinois Army National Guard

ITRC Interstate Technology Regulatory Council

ILWATER State of Illinois’ well database

LC/MS/MS liquid chromatography with tandem mass spectrometry

MIL-SPEC military specification

NELAP National Environmental Laboratory Accreditation Program

ng/L nanograms per liter

OWS Oil/Water Separator

OSD Office of the Secretary of Defense

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid
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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

TARP Tunnel and Reservoir Plan

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

WWTP Wastewater Treatment Plant 
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Former Chicago Midway AASF, Illinois

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

used, stored, disposed, or released historically (see Table ES-2). 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 relevant 

compounds. This SI was completed at the Former Chicago Midway Army Aviation Support Facility 

(Former AASF) in Chicago, Illinois and determined further evaluation under the Comprehensive 

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

Former AASF is also referred to as the “facility” throughout this document. 

The Former AASF is in Cook County and is located directly adjacent to the Chicago Midway 

International Airport. The Former AASF was active from 1939 to 2017 and became inactive when 

the size and condition of the hangar at the Former AASF could no longer support the Illinois Army 

National Guard (ILARNG) for the maintenance and storage of the necessary aircrafts. Currently, 

the ILARNG does not use the Former AASF, and the hangar is vacant. 

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

AOI was 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 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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Former Chicago Midway AASF, Illinois

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

Analyteb

Residential

(Soil)

(μg/kg)a

0-2 feet bgs

Industrial/ Commercial 

Composite Worker

(Soil)

(μg/kg)a

2-15 feet bgs

Tap Water

(Groundwater)

(ng/L)a

PFOA 19 250 6

PFOS 13 160 4

PFBS 1,900 25,000 601

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

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

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

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

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

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

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

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

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

AOI Potential 

Release Area

Soil –

Source 

Area

Groundwater –

Source Area

Groundwater –

Facility Boundary Future 

Action

1 Fire Extinguisher FTA 

& Ramp Area

Proceed 

to RI

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
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Former Chicago Midway AASF, Illinois

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 Former Chicago 

Midway Army Aviation Support Facility (Former AASF) in Chicago. The Former AASF is also

referred to as the “facility” throughout this document. 

The SI project elements were performed in compliance with Comprehensive Environmental 

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

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

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

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

investigations. 

1.2 SI Purpose

A PA was performed at Former AASF (AECOM Technical Services, Inc. [AECOM], 2020) 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 Former AASF is in Cook County, in northeastern Illinois (Figure 2-1). The cities of Oak Park, 

Oak Lawn, and Chicago are within 6 miles of the facility. The facility is adjacent to the Chicago 

Midway International Airport and is accessible from the south via West 63rd Street.

The Former AASF was active from 1939 to 2017. By 2017, the size and condition of the hangar 

at the Former AASF could no longer support the Illinois ARNG (ILARNG) for the maintenance and 

storage of the necessary aircrafts. As a result, the construction of the Kankakee AASF #2 was 

completed, and all assets at the Former AASF were transferred to the Kankakee AASF #2 in 

2017. Currently, the ILARNG does not use the Former AASF and the hangar is vacant. The facility 

occupies about 5 acres. This land was first owned by the Illinois State Armory Board in 1946 and

was transferred to the current owners, the State of Illinois, in the early 1970s. 

2.2 Facility Environmental Setting

Cook County is in northeast Illinois, within in the Chicago Lake Plain physiographic division, which 

is a division characterized by a flat surface (Figure 2-2) with a till base that slopes towards Lake 

Michigan. The slope is separated by low beach ridges, morainic headlands and islands, and large 

glacial drainageways along the Des Plaines River and Sag Channel. Parallel to the lake shores, 

well-developed spits and bars funnel flow to the south and out towards the mouth of the Des 

Plaines River. The Chicago, Calumet, and Des Plaines River pathways are determined by these 

beach ridges due to their lack of valley nature. The Chicago Lake Plain is characterized by poorly 

drained land that can cause the area to become swampy (Leighton et al., 1949). 

2.2.1 Geology

The Former AASF is underlain by glacial tills deposited during the Wisconsin glaciation. The 

uppermost formations are comprised of the Wedron Group. The Wadsworth Formation, which 

consists mostly of clay, silt, and fine-grained sand, is the youngest and stratigraphically highest 

formation within this group in the area of the facility. The Wadsworth Formation is underlain by the 

Lemont Formation, which is characterized by three members and consists of gravelly silt loam to 

loam diamiction (Hansel and Johnson, 1996). The uppermost tills at the facility have also been 

described as wave-scoured lake-bottom glacial till (Schneider and Keller, 1970).

Shallow bedrock units underly the unconsolidated sediments. The uppermost unit, comprised of 

predominantly of dolomitic rocks, cherty limestone, and some shale, is the Silurian Niagaran 

Series (Schneider and Keller, 1970). Previous investigations completed directly to the east and 

northeast of Chicago Midway Airport indicate the depth to the Niagaran Series Dolomite can be 

as shallow as 80 feet (Carnow Conibear, 2010; 2013). 

During the SI, soil borings were completed at depths between 1.2 and 10 feet below ground 

surface (bgs). Fill material (fractured concrete/gravel) from prior construction was observed at 

each boring location at depths of up to 5 feet bgs. Because groundwater was deeper at AOI01-

01 than other borings, it was the only boring advanced below the fill. The dominant lithology 

observed beneath the fill at AOI01-01, described as fine- to coarse-grained sand and lean, 

medium plasticity fines (clays and silts), is consistent with a glacial till depositional environment. 

Boring logs are presented in Appendix E. 
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Former Chicago Midway AASF, Illinois

AECOM 2-2

2.2.2 Hydrogeology

Groundwater at the Former AASF was first encountered in the surficial glacial till deposits that 

underlie the facility. Monitoring wells were installed within the till to depths less than 10 feet during 

previous investigations at the facility (Wight & Company, 2001). Based on previous results, the 

hydraulic conductivity is estimated to be approximately 5.08x10-4 feet per minute (Wight & 

Company, 2001). Many of the sewers in the Chicago area are old, brick-lined, and susceptible to 

infiltration and possible inflow of groundwater (Duncker and Johnson, 2015). However, the 

materials used to construct the sewers underlying the facility are not known, meaning brick-lined 

sewers may not be applicable to the Former AASF.

The shallow Silurian dolomite aquifer underlies the water table aquifer and resides within the 

dolomitic bedrock of the Niagaran and Alexandrian Series. Groundwater in this aquifer is sourced 

from dissolution cavities, fractures, and bedding planes within the rock (Roadcap et al., 1993). 

Beneath the Silurian dolomite aquifer is the Maquoketa Shale, which is an aquitard and confines 

the deeper Cambrian-Ordovician aquifer (Roadcap et al., 1993).

There are no wells located within the boundary of the Former AASF; however, there are several 

unknown wells within a 2-mile radius surrounding the facility (Figure 2-3). The State of Illinois’ 

well database (ILWATER) does not provide specific well type information (i.e., monitoring well,

domestic well, industrial well, etc.). Wells near the airport are reported to range from a depth of 

13 to >1,900 feet bgs, with 31 wells installed to depths less than 100 feet bgs. Drinking water for 

the Former AASF (and presumably the surrounding area) is supplied by the City of Chicago, which 

sources water from Lake Michigan (Chicago Department of Water Management, 2018). 

Depths to water measured in March 2022 during the SI ranged from 0.64 to 7.57 feet bgs. 

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

groundwater flow direction at the Former AASF is primarily from north to south. 

2.2.3 Hydrology

Floor and trench drains in the hangar drain to the oil/water separator (OWS), which is also located 

in the hangar. The OWS flows to the city sanitary sewer system, which eventually discharges to 

the Stickney Wastewater Treatment Plant (WWTP) in Cicero, Illinois. 

Off-facility storm sewer drain inlets are present on the adjacent aircraft washing area (just north 

of the Ramp Area) and on 63rd street to the south (SCS Engineers, 2014). It is unknown if these 

sewer inlets lead to the OWS. Stormwater in the vicinity of the Former AASF is conveyed to the 

Chicago Area Waterway System (CAWS), which adopted the Tunnel and Reservoir Plan (TARP) 

in order to comply with water quality standards and help with the flow of water throughout the City 

of Chicago. There is a large network of deep tunnels in the TARP; these underground tunnels 

span from 11 to 33 feet in diameter and connect to massive storage reservoirs. The tunnels help 

with flood control, routing of stormwater sewer runoff, and a have a major impact on regional 

hydrology. The tunnels can also be used as a storage area for sewer runoff but are mostly used 

to direct flow to the storage tanks. Since the City of Chicago is a primarily flat urban area, most of 

the hydrology in the city is engineering-designed rather than a natural surface flow. Without the 

engineered drainage system, there would be no way to remove excess water quickly, which would 

create overland flooding, sewer overflow, and flooded basements. Any natural drainage flow that 

exists in Chicago flows towards Lake Michigan through small, low-sloped, sluggish streams, along 

with the major waterways in the Chicago and Calumet Rivers. During the dry season, the CAWS 

can be found in a low-velocity setting, while during heavy periods of precipitation, they will open 

the gates into the tanks and Lake Michigan to prevent any flooding in the tunnels. These 

drawdowns are important and have no noticeable effect on Lake Michigan (Duncker and Johnson, 

2015). Surface water features and drainage pathways are presented on Figure 2-5. 
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Former Chicago Midway AASF, Illinois

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2.2.4 Climate

The climate at the facility has four defined seasons with a variation in temperatures. The summers 

at the facility are warm and often humid. The winters are freezing and extremely windy. Cloud 

cover can be found all times of the year. Temperatures vary from average highs of 59.3 degrees 

Fahrenheit (°F) to average lows of 43.3 °F. The average annual temperature is 51.3 °F. Average 

precipitation is 39.04 inches of rain. April to September is the wet season, while October to March

is the dry season. Chicago’s warm months are from May to October, with an average temperature 

above 60.0 °F. Cold months in Chicago are from November to April (World Climate, 2022). 

2.2.5 Current and Future Land Use

The Former AASF is a controlled access facility and is adjacent to the Chicago Midway 

International Airport. At present, the ILARNG no longer uses the Former AASF, and the land is 

anticipated to be transferred to Chicago Midway International Airport. The ILARNG has no 

intentions of using or occupying this land in the future.

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

The following mammals, insects, birds, reptiles, shellfish, and plants are federally endangered, 

threatened, proposed, and/ or are listed as candidate species in Cook County, Illinois (US Fish 

and Wildlife Service [USFWS], 2022). 

• Mammals: Tricolored bat (Perimyotis subflavus) – proposed endangered; and Northern

long-eared bat (Myotis septentrionalis) - threatened

• Insects: Monarch butterfly (Danaus plexippus) – candidate; Hine’s emerald dragonfly

(Somatochlora hineana) – endangered; Rusty patched bumble bee (Bombus affinis) –

endangered

• Birds: Piping plover (Charadrius melodus) – endangered; Red knot (Calidris canutus rufa)

– endangered

• Reptiles: Eastern Massasauga (Sistrurus catenatus) – threatened

• Shellfish: Snuffbox mussel (Epioblasma triquetra) – endangered

• Plants: Mead’s milkweed (Asclepias meadii) - threatened; Eastern prairie fringed orchid

(Platanthera leucophaea) - threatened; Leafy prairie-clover (Dalea foliosa) – endangered

2.3 History of PFAS Use 

Two potential release areas were identified in the PA where AFFF may have been used during 

fire training exercises and/ or storage (AECOM, 2020). These release areas were grouped into 

one AOI based on preliminary data and assumed groundwater flow directions. A description of 

the AOI is presented in Section 3. 
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CHICAGO MIDWAY AASF

­12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SS

8/30/2022

8/30/2022

PROJECT Site Inspection at Chicago Midway AASF, IL

8/30/2022

1:63,360

PM CM 8/30/2022 Base Map: Sources: Esri, HERE, Garmin, USGS,

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

Figure 2-1

Facility Location

Legend

Facility Boundary

0 0.5 1 2

Miles

^_

AECOM 2-5 
­12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SS

8/30/2022

8/30/2022

PROJECT Site Inspection at Chicago Midway AASF, IL

8/30/2022

1:12,000

PM CM 8/30/2022 Base Map: USGS The National Map: National

Boundaries Dataset, 3DEP Elevation Program,

Figure 2-2

Facility Topography

Legend

Facility Boundary

0 500 1,000 2,000

Feet

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Salt Creek

South Branch

Chicago River

LucasDitch

Des Plaines River

Chicago Sanitary

and Ship Canal

­12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SS

10/7/2022

10/7/2022

PROJECT Site Inspection at Chicago Midway AASF, IL

10/7/2022

1:84,000

PM CM 10/7/2022 Base Map: Source: Esri, Maxar, Earthstar Geographics,

and the GIS User Community

Figure 2-3

Groundwater Features

Legend

Facility Boundary

Water Body

Wetland

River/Stream

Groundwater Flow Direction

Geology

Silurian System

Wells

A! Other/Unknown Well

0 3,500 7,000 14,000

Feet

AECOM 2-7
?! ?!

?!

?!

?!

Hangar

Oil/Water

Separator

AOI01-01*

610.62

AOI01-02

617.21

AOI01-03

616.63

AOI01-04

617.07

AOI01-05

616.86

616

616

617

618

617

618

­12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SS

10/20/2022

10/20/2022

PROJECT Site Inspection at Chicago Midway AASF, IL

10/20/2022

1:1,440

PM CM 10/20/2022 Base Map: Source: Esri, Maxar, Earthstar Geographics,

and the GIS User Community

Figure 2-4

Groundwater Elevations,

March 2022

Legend

?! DPT Boring Location

Facility Boundary

River/Stream

Groundwater Elevation Contour

Inferred Groundwater Elevation Contour

Groundwater Flow Direction

0 60 120 240

Feet

Groundwater elevations in ft NAVD88.

Groundwater levels at AOI01-01 was not used

to create groundwater contours.

AECOM 2-8
Chicago

Sanitary and

Ship Canal

Maple Lake-Chicago

Sanitary and Ship

Canal Watershed

Stony Creek

Watershed

South Branch Chicago

River-Chicago Sanitary

and Ship Canal Watershed

0 0.25 0.5 1

Miles

­ Figure 2-5

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Chicago Midway AASF, IL

8/30/2022

8/30/2022

8/30/2022

MS

SS

CM

GIS BY

CHK BY

PM

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

8/30/2022

1:31,680

Legend

Facility Boundary

Water Body

Canal/Ditch

Surface Water Flow Direction

Surface Water Features

12420 Milestone Center Drive

Germantown, MD 20876

Maple Lake-Chicago 

Sanitary and Ship Canal Watershed

0 100 200 400

Feet

Note: The site specific surface water flow direction arrows are 

from the SPCC Plan, AASF #2 Midway Airport, February 2014.

AECOM 2-9 
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AECOM 2-10

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AECOM 3-1

3. Summary of Areas of Interest

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

disposed, or released historically. Based on the PA findings, two potential release areas were 

identified at Former AASF and combined into one AOI (AECOM, 2020). Additionally, adjacent 

potential release areas were identified during the PA (AECOM, 2020), including: The Airport 

Crash, Fixed Base Operator (FBO) Hangars, and the Chicago Fire Department. The potential 

release areas and adjacent potential release areas are shown on Figure 3-1. 

3.1 AOI 1

AOI 1 consists of two potential release areas. These release areas are described below

3.1.1 Fire Extinguisher FTA

In approximately 2004, a one-time fire training event occurred inside the hangar, where a TriMaxTM 30 unit was filled with a soap and water mixture and was used to practice putting out a 

small pan fire. After the training exercise was completed, the mixture was washed down floor 

drains to the OWS. The OWS discharges to the city sewer system, which leads to the Stickney 

WWTP. 

It is possible that releases within the hangar may have also flowed out the north-facing hangar 

doors and onto the Ramp Area. The Ramp Area flows to drains on the off-facility, adjacent aircraft 

washing area. These drains are designated as storm sewer drain inlets on the Spill Prevention 

Control and Countermeasure Plan (SCS Engineers, 2014). It is unknown if these off-facility drains 

connect to the OWS. It is possible that AFFF may have infiltrated into the subsurface soil via joints 

in the floor slab or cracks in the pavement.

3.1.2 Ramp Area

Between 2000 and 2005, five Tri-MaxTM 30 fire extinguishers were located at the facility. Three of 

the extinguishers were located by the hangar doors, one was located on the ramp, and one unit 

was located in the hangar. The AFFF from the Tri-MaxTM 30 extinguisher located in the hangar 

was drained into a bucket and filled with a soap and water mixture for training purposes. During 

the winter months, AFFF in the Tri-MaxTM 30 extinguishers was emptied into buckets and replaced 

with cold-weather-approved AFFF to avoid freezing. Releases at the Ramp Area would likely flow 

to nearby grassy areas or to the storm sewer drains, as described in Section 3.1.1. 
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AECOM 3-2

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AOI 1

Hangar

Fire Extinguisher

FTA

FBO Hangar

Airport Crash

Chicago Fire

Department

FBO Hangars

Ramp Area

Maple Lake-Chicago

Sanitary and Ship

Canal Watershed

­12420 Milestone Center Drive

Germantown, MD 20876

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SS

8/31/2022

8/31/2022

PROJECT Site Inspection at Chicago Midway AASF, IL

8/31/2022

1:9,600

PM CM 8/31/2022 Base Map: Source: Esri, Maxar, Earthstar Geographics,

and the GIS User Community

Figure 3-1

Areas of Interest

Legend

Area of Interest

Potential Release Area

Facility Boundary

Surface Water Flow

Direction

Groundwater Flow

Direction

A! Other/Unknown Well

0 400 800 1,600

Feet

AOI 1

Fire

Extinguisher FTA

Ramp Area

AECOM 3-3 
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AECOM 3-4

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AECOM 4-1

4. Project Data Quality Objectives

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

Assurance Project Plan (QAPP) Addendum (AECOM, 2021a), the objective of the SI is to identify 

whether there has been a release to the environment at the AOI identified in the PA. For the 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 Former AASF (AECOM, 2020);

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

with the site-specific Uniform Federal Policy (UFP)-QAPP Addendum (AECOM, 2021a); and

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

parameters measured at the time of sampling.

4.3 Study Boundaries

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

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

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

owner(s). The scope of the SI was bounded vertically by the top 5 feet of the groundwater table. 

Temporal boundaries were limited to the spring, summer, and fall months. 

4.4 Analytical Approach

Samples were analyzed by Pace Analytical Gulf Coast, accredited under the Department of 

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

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

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

as defined in the SI QAPP Addendum (AECOM, 2021a). 

4.5 Data Usability Assessment 

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

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

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

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

installation-specific DQOs. Both sampling and analytical activities are considered to assess 

whether the collected data are of the right type, quality, and quantity to support the decisionmaking (DoD, 2019a; DoD, 2019b; USEPA, 2017). 
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AECOM 4-2

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

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

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

requirements of the SI QAPP Addendum (AECOM, 2021a). 
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AECOM 5-1

5. Site Inspection Activities

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

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

in accordance with the following approved documents: 

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

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

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

• Final Preliminary Assessment Report, Former Chicago Midway Army Aviation Support

Facility, Chicago, Illinois dated August 2020 (AECOM, 2020);

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

Former Chicago Midway Army Aviation Support Facility, Chicago, Illinois dated November

2021 (AECOM, 2021a); and

• Final Site Safety and Health Plan, Former Chicago Midway Army Aviation Support Facility,

Chicago, Illinois dated November 2021 (AECOM, 2021b).

The SI field activities consisted of utility clearance, direct push boring, soil sample collection, 

temporary monitoring well installation, grab groundwater sample collection, and land surveying. 

Two rounds of utility clearance occurred on 21 October 2021 and 21 March 2022. The remaining 

field activities were conducted from 24 to 25 March 2022 in accordance with the SI QAPP 

Addendum (AECOM, 2021a), except as noted in Section 5.8. 

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:

• Seven soil samples from five boring locations;

• Five grab groundwater samples from five temporary wells;

• Eleven (11) 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, a Field Change Request Form

is provided in Appendix B3, land survey data are provided in Appendix B4, and investigationderived waste (IDW) polygons are provided in Appendix B5. Additionally, a photographic log of 

field activities is provided in Appendix C. 

5.1 Pre-Investigation Activities

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

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

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

5.1.1 Technical Project Planning

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

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

determining data needs; 3.) developing data collection strategies; and 4.) finalizing the data 
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AECOM 5-2

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

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

address the AOIs identified in the PA. 

A combined TPP Meeting 1 and 2 was held on 15 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 included the ARNG, ILARNG, USACE, and Illinois Environmental 

Protection Agency. Stakeholders were provided the opportunity to make comments on the 

technical sampling approach and methods at the combined TPP Meeting 1 and 2. The outcome 

of the combined TPP Meeting 1 and 2 was memorialized in the SI QAPP Addendum (AECOM, 

2021a). 

A TPP Meeting 3 will be held after the field event to discuss the results of the SI. Meeting minutes 

for TPP 3 will be 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 

Chicago 811 “Call Before You Dig” utility clearance provider to notify them of intrusive work in 

March 2022. Additionally, AECOM contracted Ground Penetrating Radar Systems, LLC. (GPRS), 

a private utility location service, to perform utility clearance. GPRS performed utility clearance of 

the proposed boring locations in March 2022 with input from the AECOM field team and the 

Former 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 the Former AASF was sampled from a spigot on the south side of 

the hangar on 12 August 2021 to assess usability for decontamination of drilling equipment. 

Results of the sample collected (CM-DECON-01) confirmed this source to be acceptable for use 

in this investigation; therefore, it was used throughout the field activities. Specifically, the sample 

was analyzed by LC/MS/MS compliant with QSM 5.3 Table B-15. A second decontamination 

sample (CM-DECON-02) was collected from Cascade’s pressure washer to ensure crosscontamination did not occur during the decontamination process. The results of the 

decontamination water samples are provided in Appendix F. A discussion of the results is 

presented in the DUA (Appendix A). 

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

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

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

(AECOM, 2021a). Prior to the start of field work each day, a Sampling Checklist was completed 

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

member regarding the allowable materials within the sampling environment. 

5.2 Soil Borings and Soil Sampling

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

Addendum (AECOM, 2021a). A GeoProbe® 7220DT macrocore sampling system was used to 

collect continuous soil cores where able. A hand auger was used to collect soil from the top five 

feet of the boring, in accordance with AECOM utility clearance procedures. The soil boring 

locations are shown on Figure 5-1, and depths are provided in Table 5-1. 
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AECOM 5-3

Due to shallow depth to groundwater observed at most boring locations, only one discrete surface 

soil sample was collected from the vadose zone for chemical analysis from soil borings AOI01-02 

to AOI01-05. Deeper groundwater was encountered at boring AOI01-01, and three soil samples 

were collected: one surface soil sample, one subsurface soil sample approximately 2 feet above 

the groundwater table, and one subsurface soil sample at the mid-point between the surface and 

the groundwater table. The surface soil sample at boring AOI01-01 was collected at 2 to 3 feet 

bgs due to the top 2 feet consisting mostly of fractured concrete and gravel that was unsuitable 

to be sampled.

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

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

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

Observations and measurements were recorded on sampling forms (Appendix B2) and in a nontreated field logbook (i.e., composition notebook). Depth interval, recovery thickness, PID 

concentrations, moisture, relative density, color (using a Munsell soil color chart), and texture 

(using the USCS) were recorded. The boring logs are provided in Appendix E. 

Soil borings completed during the SI observed gravel fill from prior construction work directly

beneath ground surface at each boring location. At AOI01-01, fine- to coarse-grained sand and 

lean, medium plasticity fines were observed below the gravel fill. The borings were completed at 

depths between 1.2 and 10 feet bgs. The lithology results and facility observations are consistent 

with glacial deposition reported in the region, as discussed in Section 2.2.1. 

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

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

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

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

carbon (TOC) (USEPA Method 9060A) and pH (USEPA Method 9045D), in accordance with the 

SI QAPP Addendum (AECOM, 2021a). Grain size analysis was not performed, in accordance 

with the SI QAPP Addendum, because extensive horizontal and vertical clay units were not 

encountered in the field (AECOM, 2021).

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

parameters as the accompanying samples. MS/MSDs were collected at a rate of 5% and 

analyzed for the same parameters as the accompanying samples. In instances when nondedicated 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.

Four of the borings were drilled in asphalt- or concrete-covered areas. The borings were 

converted to temporary wells, which were sampled, surveyed and subsequently abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2021a). Boreholes drilled in asphalt or 

concrete were patched upon abandonment to match existing ground conditions. 

5.3 Temporary Well Installation and Groundwater Grab Sampling

Temporary wells were installed using a GeoProbe® 7220DT macrocore sampling system. Once 

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

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

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

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

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

groundwater to infiltrate and recharge the temporary well screen intervals. After the recharge 
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AECOM 5-4

period, groundwater samples were collected using a peristaltic pump with PFAS-free HDPE 

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

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

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

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

was collected. Several temporary wells did not have sufficient recharge to collect a groundwater 

sample and measure water quality parameters; therefore, grab samples were collected in 

accordance with the SI QAPP Addendum (AECOM, 2021a) without collecting water quality data. 

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

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

of the groundwater samples. 

Each sample was collected into laboratory-supplied PFAS-free HDPE bottles and labeled using 

a PFAS-free marker or pen. Samples were packaged on ice and transported via FedEx under 

standard CoC procedures to the laboratory and analyzed by LC/MS/MS compliant with QSM 5.3

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

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. One field reagent 

blank was collected in accordance with the PQAPP (AECOM, 2018a). A temperature blank was 

placed in each cooler to ensure that samples were preserved at or below 6°C during shipment.

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

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

the hole with bentonite chips. 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 24 March 2022. Groundwater elevation 

measurements were collected from the five new temporary monitoring wells. 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 Illinois-licensed land surveyors following 

guidelines provided in the SOPs found in the SI QAPP Addendum (AECOM, 2021a). Survey data 

from the newly installed wells on the facility were collected on 24 March 2022 in the applicable 

North American Datum 1983 State Plane Illinois East (US Survey Feet) (horizontal) and North 

American Vertical Datum 1988 (vertical). The surveyed well data are provided in Appendix B4. 

5.6 Investigation-Derived Waste 

As of the date of this report, the disposal of investigation-derived waste (IDW) is not regulated 

federally. IDW generated during the SI is considered non-hazardous waste and was managed in 

accordance with the SI QAPP Addendum (AECOM, 2021a) and with the DA Guidance for 

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

Solid IDW (i.e., soil cuttings and cored material) generated during SI activities were left in place 

at the point of the source (i.e., downhole) or placed in the gravel-covered area to the east of the 

hangar. The solid IDW was not sampled and assumes the characteristics of the associated soil 

samples collected from that source location. Geographic coordinates were collected using a 
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AECOM 5-5

global positioning system (GPS) around each location where IDW was placed (i.e., an IDW 

polygon). The IDW polygons are displayed on the figure in Appendix B5. 

Liquid IDW generated during SI activities (i.e., purge water and decontamination fluids) was

containerized in a properly labeled 55-gallon drum and stored on the facility at a location designated 

by the ILARNG Environmental Manager. The liquid IDW was not sampled and assumes the 

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

IDW will be further managed under separate ARNG contract in accordance with the Army Guidance 

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

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

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

activities were disposed of at a licensed solid waste landfill.

5.7 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. 

5.8 Deviations from SI QAPP Addendum

One deviation from the SI QAPP Addendum was identified prior to mobilization due to the Federal 

Aviation Administration’s (FAA) Final Determination. The deviation is noted below and is 

documented in Field Change Request Form (Appendix B3): 

• The Final Determination submitted by the Federal Aviation Administration (FAA) prohibited

drilling at boring location CM-01 without closing the Chicago Midway International Airport

runway during drilling operation because the location penetrates the Runway 4R/22L

Runway Object Free Area. At the client’s direction, CM-01 was removed from the scope

prior to mobilization. CM-01 is a boundary location with the purpose of determining whether

off-facility adjacent sources of PFAS are migrating onto the northwestern portion of the

facility property. Due to the nature of the FAA Final Determination and the FAA restrictions

of moving drilling locations without resubmitting a new case submission, no additional boring

locations could be substituted for CM-01.
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 5-6

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Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Former Chicago Midway Army Aviation Support Facility, Illinois

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)

Comments

AOI01-01-SB-2-3 3/24/2022 11:10 2 - 3 x

AOI01-01-SB-4-5 3/24/2022 11:15 4 - 5 x

AOI01-01-SB-5-7 3/24/2022 11:20 5 - 7 x x x

AOI01-01-SB-5-7-D 3/24/2022 11:20 5 - 7 x x x FD

AOI01-01-SB-5-7-MS 3/24/2022 11:20 5 - 7 x x x MS

AOI01-01-SB-5-7-MSD 3/24/2022 11:20 5 - 7 x x x MSD

AOI01-02-SB-0-2 3/24/2022 9:25 0 - 1.2 x

AOI01-03-SB-0-1 3/24/2022 10:25 0 - 1 x

AOI01-04-SB-0-2 3/24/2022 10:50 0 - 2 x

AOI01-05-SB-0-2 3/24/2022 9:40 0 - 2 x

AOI01-01-GW 3/25/2022 15:45 NA x

AOI01-02-GW 3/24/2022 13:50 NA x

AOI01-03-GW 3/24/2022 15:00 NA x

AOI01-04-GW 3/24/2022 15:30 NA x

AOI01-05-GW 3/24/2022 14:25 NA x

AOI01-05-GW-D 3/24/2022 14:25 NA x FD

AOI01-05-GW-MS 3/24/2022 14:25 NA x MS

AOI01-05-GW-MSD 3/24/2022 14:25 NA x MSD

CM-FRB-01 3/24/2022 14:15 NA x

CM-ERB-01 3/24/2022 12:20 NA x from rig

CM-ERB-02 3/24/2022 12:30 NA x from hand auger

CM-DECON-01 8/12/2021 7:15 NA x from spigot

CM-DECON-02 3/24/2022 12:10 NA x from washer

Notes:

ASTM = American Society for Testing and Materials

bgs = below ground surface

DECON = decontamination water sample

ERB = equipment rinsate blank

FD = field duplicate

FRB = field reagent blank

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

QSM = Quality Systems Manual

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

Soil Samples

Quality Control Samples

Groundwater Samples

AECOM 5-7 
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 5-8

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Table 5-2

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

Site Inspection Report, Former Chicago Midway Army Aviation Support Facility, Illinois

Area of 

Interest

Boring 

Location

Soil Boring 

Depth 

(feet bgs)

Temporary Well 

Screen Interval 

(feet bgs)

Top of Casing 

Elevation 

(feet NAVD88)

Ground Surface 

Elevation 

(feet NAVD88)

Depth to 

Water

(feet btoc)

Dept

Wa

(feet 

AOI01-01 10 5 - 10 618.51 618.19 7.89 7.5AOI01-02 1.2 0 - 1.2 619.11 617.85 1.90 0.6

AOI01-03 3 0 - 3 619.58 617.52 2.95 0.8

AOI01-04 3 0 - 3 620.07 618.05 3.00 0.9

AOI01-05 3 0 - 3 620.27 618.19 3.41 1.3

Notes:bgs = below ground surfacebtoc = below top of casingNAVD88 = North American Vertical Datum 1988

1

AECOM 
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Former Chicago Midway AASF, Illinois

AECOM 5-10

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AOI01-01 AOI01-02

AOI01-03

AOI01-04

AOI01-05

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Germantown, MD 20876

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8/31/2022

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and the GIS User Community

Figure 5-1

Site Inspection Sample Locations

Legend

?! DPT Boring Location

Facility Boundary

Groundwater Flow Direction

0 60 120 240

Feet

AECOM 5-11
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 5-12

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Site Inspection Report

Former Chicago Midway AASF, Illinois

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 the AOI is provided in Section 6.3. 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 to the SLs presented in Table 6-1. The SLs 

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

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

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

and the industrial/commercial worker scenario is applied to shallow subsurface soil results (2 to 

15 feet bgs). However, as discussed in Section 5.2, surface soil at AOI01-01 was collected from 

2 to 3 feet bgs due to overlying concrete and fractured concrete and gravel fill. Consequently, the 

residential scenario was applied to this sample, providing a conservative assessment of the 

potential exposure route for site workers and construction workers. 
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 6-2

6.2 Soil Physicochemical Analyses

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

are important for evaluating transport through the soil medium. Appendix F contains the results 

of the TOC and pH sampling. 

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

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

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

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

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

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

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

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

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

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

6.3 AOI 1 

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

AOI 1: Fire Extinguisher FTA and Ramp Area. The soil and groundwater results are summarized 

on Table 6-2 and 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 and Table 6-3

summarize the soil results. 

Surface soil was sampled between 0 to 2 feet bgs at borings AOI01-02 through AOI01-05 and 

from 2 to 3 feet bgs at AOI01-01. Soil was also sampled from the shallow subsurface soil interval 

(4 to 5 feet and 5 to 7 feet bgs) from boring AOI01-01. In surface soil, PFOA, PFOS, PFHxS, and 

PFNA were detected at concentrations below their SLs, whereas PFBS was not detected. The 

ranges of detections in surface soil are as follows:

• PFOA was detected at two of the five borings, with concentrations of 0.084 J

micrograms per kilogram (μg/kg) and 0.105 J μg/kg.

• PFOS was detected at three locations, with concentrations ranging from 0.088 J μg/kg

to 0.802 J μg/kg.

• PFHxS was detected at three locations, with concentrations ranging from 0.039 J μg/kg

to 0.050 J μg/kg.

• PFNA was only detected at AOI01-04, with a concentration of 0.034 J μg/kg.

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

below their SLs. PFOS and PFHxS were detected in both subsurface soil intervals, with maximum

concentrations of 0.243 J μg/kg and 0.057 J μg/kg, respectively. PFOA and PFNA were detected 

only in the shallower interval (4 to 5 feet bgs), at concentrations of 0.398 μg/kg and 0.031 μg/kg, 

respectively. PFBS was not detected in shallow subsurface soil. 

6.3.2 AOI 1 Groundwater Analytical Results

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

summarizes the groundwater results. 
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 6-3

Groundwater was sampled from temporary monitoring wells AOI01-01 through AOI01-05. The 

following exceedances of the SLs were measured.

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

AOI01-01 and AOI01-02, with concentrations of 44.1 ng/L and 19.7 ng/L, respectively.

• PFOS was detected above the SL of 4 ng/L at all five temporary wells, with

concentrations ranging from 5.61 ng/L to 46.9 ng/L. The maximum detection was

observed at AOI01-02.

• PFNA was detected above the SL of 6 ng/L at temporary well AOI01-02 with a

concentration of 12.3 ng/L.

PFHxS and PFBS were detected at concentrations below their SLs. PFHxS was detected at three 

of the five temporary wells, with concentrations ranging from of 1.35 J ng/L to 15.7 ng/L. PFBS 

was detected at four of five temporary well locations, with concentrations ranging from 1.80 J ng/L 

to 5.47 ng/L. 

6.3.3 AOI 1 Conclusions

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

SLs. PFOA, PFOS, and PFNA 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

Former Chicago Midway AASF, Illinois

AECOM 6-4

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Table 6-2

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

Site Inspection Report, Former Chicago Midway AASF

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual

PFBS 1900 ND U ND U ND U ND U ND U

PFHxS 130 ND U 0.050 J ND U 0.041 J 0.039 J

PFNA 19 ND U ND U ND U 0.034 J ND U

PFOA 19 ND U ND U ND U 0.105 J 0.084 J

PFOS 13 ND U 0.088 J ND U 0.802 J 0.102 J

Grey Fill Detected concentration exceeded OSD Screening Levels

Note: The surface soil sample at boring AOI01-01 was collected at 2 to 3 feet bgs due to the top 2 feet consisting mostly of fractured concrete and gravel that was unable to be sampled. Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support Facility

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. AOI Area of Interest

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

DL detection limit

ft feet

HQ hazard quotient

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

OSD Office of the Secretary of Defense

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

USEPA United States Environmental Protection Agency

μg/kg micrograms per kilogram

Area of Interest AOI01

AOI01-04-SB-0-2

03/24/2022

0-2 ft

AOI01-05-SB-0-2

03/24/2022

0-2 ft

AOI01-02-SB-0-2

03/24/2022

0-2 ft

AOI01-03-SB-0-1

03/24/2022

0-1 ft

a. Assistant Secretary of Defense, July 2022. Risk Based Screening Levels Calculated for PFOA, PFOS, PFBS, PFHxS, and PFNA in Groundwater or Soil using 

USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on residential scenario for incidental ingestion of contaminated soil.

Sample ID

Sample Date

Depth

AOI01-01-SB-2-3

03/24/2022

2-3 ft

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

AECOM 6-5
Table 6-3

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

Site Inspection Report, Former Chicago Midway AASF

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual

PFBS 25000 ND U ND U ND U

PFHxS 1600 0.057 J 0.046 J 0.054 J

PFNA 250 0.031 J ND U ND U

PFOA 250 0.398 J ND U ND U

PFOS 160 0.168 J 0.243 J ND UJ

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support Facility

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. AOI Area of Interest

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

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

ft feet

HQ hazard quotient

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

OSD Office of the Secretary of Defense

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

USEPA United States Environmental Protection Agency

μg/kg micrograms per kilogram

AOI01

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

Area of Interest

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.

AOI01-01-SB-5-7-D

03/24/2022

5-7 ft

AOI01-01-SB-4-5

03/24/2022

4-5 ft

AOI01-01-SB-5-7

03/24/2022

5-7 ft

Sample ID

Sample Date

Depth

AECOM 6-6
Table 6-4

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

Site Inspection Report, Former Chicago Midway AASF

Analyte OSD Screening 

Level a

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

PFBS 601 5.47 2.59 J 1.80 J 1.91 J ND U ND U

PFHxS 39 6.29 15.7 ND U ND U 1.35 J 1.48 J

PFNA 6 3.83 J 12.3 2.44 J 2.75 J 1.30 J 1.29 J

PFOA 6 44.1 19.7 4.07 4.47 2.34 J 2.32 J

PFOS 4 5.61 46.9 9.70 9.88 5.78 5.65

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support Facility

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. AOI Area of Interest

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

DL detection limit

GW groundwater

HQ hazard quotient

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

OSD Office of the Secretary of Defense

QSM Quality Systems Manual

Qual interpreted qualifier

USEPA United States Environmental Protection Agency

ng/l nanogram per liter

03/24/2022

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

AOI01-04-GW

03/24/2022

AOI01-05-GW

03/24/2022

AOI01-02-GW

03/24/2022

AOI01-03-GW

03/24/2022

Area of Interest

Sample ID

Sample Date

AOI01-01-GW

03/24/2022

AOI01-05-GW-D

AECOM 6-7
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 6-8 

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AOI01-03

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Facility Boundary

Shallow

Intermediate

Deep

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-1

PFOA Detections in Soil

8/30/2022

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the GIS User Community

1:1,200

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

0 50

­

100 200

Feet

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

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

AECOM 6-9 
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AOI01-03

AOI01-04

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Shallow

Intermediate

Deep

12420 Milestone Center Drive

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PFOS Detections in Soil

8/30/2022

8/30/2022

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the GIS User Community

­

1:1,200

0 50 100 200

Feet

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

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

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

AECOM 6-10
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Shallow

Intermediate

Deep

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-3

PFBS Detections in Soil

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8/30/2022

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­

1:1,200

0 50 100 200

Feet

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

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

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

AECOM 6-11
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Facility Boundary

Shallow

Intermediate

Deep

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-4

PFHxS Detections in Soil

8/30/2022

8/30/2022

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

the GIS User Community

­

1:1,200

0 50 100 200

Feet

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

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

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

AECOM 6-12
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Shallow

Intermediate

Deep

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-5

PFNA Detections in Soil

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the GIS User Community

­

1:1,200

0 50 100 200

Feet

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

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

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-13
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AOI01-03

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AOI01-04

AOI01-05

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AOI01-03

AOI01-04

AOI01-05

Facility Boundary

Groundwater Flow Direction

PFOA

PFOS

PFBS

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-6

PFOA, PFOS, and PFBS Detections

in Groundwater

10/5/2022

10/5/2022

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1:1,440

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

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

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

0 60

­

120 240

Feet

AECOM 6-14
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AOI01-05

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Oil/Water

Separator

AOI01-01 AOI01-02

AOI01-03

AOI01-04

AOI01-05

Facility Boundary

Groundwater Flow Direction

PFHxS

PFNA

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-7

PFHxS and PFNA Detections

in Groundwater

8/31/2022

8/31/2022

MS 8/31/2022

SS

CM

GIS BY

CHK BY

PM

8/31/2022

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Chicago Midway AASF, IL

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

the GIS User Community

­ 1:1,200

0 50 100 200

Feet

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

PFNA Results (ng/L)

ND

>ND - 6

>6 - 100

>100 - 1,000

>1,000

PFHxS Results (ng/L)

ND

>ND - 39

>39 - 100

>100 - 1,000

>1,000

AECOM 6-15
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 6-16

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Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 7-1

7. Exposure Pathways

The CSM for the AOI, 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 Remedial Investigation (RI) or interim action is determined based upon 

exceedances of the SLs for the relevant compounds and whether the release is more than likely 

attributable to the DoD. A CSM presents the current understanding of the site conditions with 

respect to known and suspected sources, potential transport mechanisms and migration 

pathways, and potentially exposed human receptors. A human exposure pathway is considered 

potentially complete when the following conditions are present:

1. Contaminant source;

2. Environmental fate and transport;

3. Exposure point;

4. Exposure route; and

5. Potentially exposed populations.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

boundary, and recreational users outside of the facility boundary. However, because ILARNG 

does not currently use the facility, current site worker and construction worker pathways for all 

media are considered incomplete.

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 Fire Extinguisher FTA and Ramp Area, where Tri-Max 30 fire extinguishers were 

released and stored between 2000 and 2005. 
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 7-2

PFOA, PFOS, PFHxS, and PFNA were detected in surface soil at AOI 1 at concentrations below 

their SLs. Site workers and construction workers could contact constituents in surface soil via 

incidental ingestion and inhalation of dust. Therefore, the surface soil exposure pathways for

future site workers and future construction workers are potentially complete. Off-facility residents 

are located as close as 200 feet from the south of the facility property and could contact 

constituents in surface soil via inhalation of dust. Consequently, the inhalation of dust exposure 

pathway is potentially complete for off-facility residents. PFOA, PFOS, PFHxS, and PFNA were 

detected in subsurface soil at AOI 1 below their SLs. Construction workers could contact 

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

exposure pathway for future construction workers is potentially complete. The facility is secured 

and access is restricted, and therefore trespassers are unlikely. Therefore, the soil exposure 

pathways to trespassers are incomplete. 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 PFNA were detected above their respective SLs in groundwater samples 

collected at AOI 1. Drinking water for the Former AASF is supplied by the City of Chicago and 

sourced from Lake Michigan. Consequently, the ingestion exposure pathway for site workers and 

offsite residents is incomplete. Shallow groundwater was encountered between 0.64 and 7.57 

feet bgs and is therefore shallow enough to be encountered during construction activities; 

consequently, the ingestion exposure pathway for future construction workers is potentially 

complete. Where groundwater is within 2 feet of the surface, the pathway for the site worker is 

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

7.3 Surface Water and Sediment Exposure Pathway

The SI results in soil and groundwater, in combination with knowledge of the fate and transport 

properties of PFAS, were used to determine whether a potentially complete pathway exists 

between the source and potential receptors.

7.3.1 AOI 1

PFAS are water soluble and can migrate readily from soil to surface water via leaching and runoff. Because PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil and groundwater at 

AOI 1, it is possible that those compounds may have migrated from soil and groundwater to 

downgradient surface water bodies. Off-facility recreational users using these downgradient 

surface water bodies could contact constituents in surface water and sediment. Consequently, 

the exposure pathway to off-facility recreational users is considered potentially complete. There 

are no surface water bodies at the facility and, therefore, the exposure pathways for site workers 

and construction workers are considered incomplete. The CSM for AOI 1 is presented on Figure 

7-1.
Media

SOURCE PATHWAY RECEPTOR

AOI 1 Surface Soil

Human

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne Soil

Particulate

Surface Soil

at AOI

Surface

Water/

Sediment

Subsurface

Soil

Shallow

Groundwater

Source Release

Mechanism Media Transportand Migration Media ExposureRoutes

Inhalation of

Dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors:

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway

with Exceedance of SL

/

Site

Worker

Construction

Worker Resident1 Trespasser /Recreational User1

Site

Worker

Construction

Worker Resident1

/ /

/ /

/ /

/

LEGEND

Figure 7-1

Conceptual Site Model, AOI 1

Former Chicago Midway AASF, Illinois

Potential

Off-Facility

Source Not

under

Control of

ARNG

Trespasser /

Recreational User1

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

Notes:

/ /

/ /

/

Fire training

exercises; AFFF

storage

/

/

/ /

/

/

/

AECOM 7-3 
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 7-4

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Site Inspection Report

Former Chicago Midway AASF, Illinois

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 consisted of utility clearance, direct push boring, soil sample collection, 

temporary monitoring well installation, grab groundwater sample collection, and land surveying. 

Two rounds of utility clearance occurred on 21 October 2021 and on 21 March 2022. The remaining 

field activities were conducted from 24 to 25 March 2022 in accordance with the SI QAPP 

Addendum (AECOM, 2021a), except as noted in Section 5.8. 

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. 

• Seven soil samples from five boring locations;

• Five grab groundwater samples from five temporary wells;

• Eleven (11) 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 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 was refined to assess whether a potentially complete pathway exists 

between the source and potential receptors for potential exposure at the AOI, 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. 

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 AASF 

activities. Sample analytical concentrations collected during the SI were compared to the project

SLs in soil and groundwater, as described in Table 6-1. A summary of the results of the SI data 

relative to the SLs is as follows: 

• At AOI 1:

• The detected concentrations of PFOA, PFOS, PFHxS, and PFNA, in soil at AOI 1

were below their SLs.

• PFOA, PFOS, and PFNA in groundwater exceeded their respective SLs. PFOA

exceeded the SL of 6 ng/L, with a maximum concentration of 44.1 ng/L at location

AOI01-01. PFOS exceeded the SL of 4 ng/L, with a maximum concentration of 46.9

ng/L at location AOI01-02. PFNA exceed the SL of 6 ng/L, with a maximum

concentration of 12.3 ng/L at location AOI01-02. Based on the results of the SI,

further evaluation of AOI 1 is warranted in an RI.
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 8-2

Samples collected at locations AOI01-01 and AOI01-02 are located on the upgradient facility 

boundary and adjacent to the release areas that comprise AOI 1. Therefore, it is unclear if impacts 

to groundwater are migrating from potential adjacent locations or AOI 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 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 Fire Extinguisher FTA

& Ramp Area 

Proceed to 

RI

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

Former Chicago Midway AASF, Illinois

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. 2020. Final Preliminary Assessment Report, Former Chicago Midway Army Aviation 

Support Facility, Chicago, Illinois. August. 

AECOM. 2021a. Final Site Inspection Uniform Federal Policy-Quality Assurance Project Plan 

Addendum, Former Chicago Midway Army Aviation Support Facility, Chicago, Illinois,

Perfluorooctane Sulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA) Impacted Sites 

ARNG Installations, Nationwide. November. 

AECOM. 2021b. Final Site Safety and Health Plan, Former Chicago Midway Army Aviation 

Support Facility, Chicago, Illinois, Perfluorooctane Sulfonic Acid (PFOS) and 

Perfluorooctanoic Acid (PFOA) Impacted Sites ARNG Installations, Nationwide. November. 

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

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

6 July. 

Carnow Conibear. 2010. Comprehensive Site Investigation/ Remedial Objectives/Remedial 

Action Completion Report, Site: Area I (Parcel 112). Midway Airport Terminal Development 

Program. February.

Carnow Conibear. 2013. Comprehensive Site Investigation/ Remedial Objectives/Remedial 

Action Completion Report, Site: Area III (Portions of Parcels 58, 91, 95, 96, 97, and 98). 

Midway Airport Terminal Development Program. March.

Chicago Department of Water Management. 2018. City of Chicago, Department of Water 

Management Source Water Assessment Summary for the 2018 Consumer Confidence 

Report. 

DA. 2016. Army Guidance to Address Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic 

Acid (PFOA) Contamination. August.

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.

Duncker, J.J., and Johnson, K.K. 2015. Hydrology of and Current Monitoring Issues for the 

Chicago Area Waterway System, Northeastern Illinois. US Geological Survey: Scientific 

Investigations Report 2015-5115.
Site Inspection Report

Former Chicago Midway AASF, Illinois

AECOM 9-2

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.

Hansel, A.K., and Johnson, W.H. 1996. Wedron and Mason Groups: Lithostratigraphic 

Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area. Department 

of Natural Resources, Illinois State Geological Survey: Bulletin 104.

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 ant Transport for Per- and Polyfluoroalkyl Substances. March. 

Leighton, M.M., Ekblaw, G.E., and Horberg, L. 1949. Physiographic Divisions of Illinois. State of 

Illinois. January.

Roadcap, G.S., Cravens, S.J., and Smith, E.C. 1993. Meeting the Growing Demand for Water: 

An Evaluation of the Shallow Ground-Water Resources in Will and Southern Cook Counties, 

Illinois. Illinois State Water Survey: Report 123.

Schneider, A.F., and Keller, S.J. 1970. Geologic map of the 1° x 2° Chicago Quadrangle, Indiana, 

Illinois, and Michigan, Showing Bedrock and Unconsolidated Deposits. Indiana Geological 

Survey: Regional Geologic Map No. 4. Scale 1:250,000.

SCS Engineers. 2014. Spill Prevention Control and Countermeasure Plan, AASF #2 Midway 

Airport, 5400 West 63rd Street Chicago, Illinois. February.

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

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

(CERCLA). 

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

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

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

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

Assessments). December.

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

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

Innovation. January.

USEPA. 2021. Technical Fact Sheet: Toxicity Assessment for PFBS. 

https://www.epa.gov/pfas/learn-about-human-health-toxicity-assessment-pfbs. 8 April.

USFWS. 2022. Environmental Conservation Online System, Cook, Illinois. Accessed, 21 

September 2022 at https://ecos.fws.gov/ecp/report/species-listings-by-current-rangecounty?fips=17031. 

Wight & Company. 2001. Corrective Action Completion Report, Midway Army Aviation Support 

Facility, Number Two, 5400 W. 63rd Street, Chicago. IEMA Number 92-3675. February.

World Climate. 2022. Average Weather Data for Chicago, Illinois. Available at 

http://www.worldclimate.com/climate/us/illinois/chicago. (Accessed 23 September 2022). 
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Former Chicago Midway AASF, Illinois

AECOM 9-3

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. 
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