FINAL

Site Inspection Report 

General Lucius D. Clay 

National Guard Center

Marietta, Georgia

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 

April 2023

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED
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General Lucius D. Clay National Guard Center, Georgia

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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 ..................................................................................................... 2-3

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

2.2.5 Current and Future Land Use....................................................................... 2-4

2.2.6 Sensitive Habitat and Threatened/ Endangered Species............................. 2-4

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

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

3.1 AOI 1 Hangar/Ramp Area....................................................................................... 3-1

3.2 AOI 2 Hangar 300................................................................................................... 3-1

3.3 AOI 3 Hangar 312................................................................................................... 3-1

3.4 AOI 4 Building 555.................................................................................................. 3-2

3.5 Adjacent Source Information .................................................................................. 3-2

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

5.6 Surveying................................................................................................................ 5-6

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

5.8 Laboratory Analytical Methods................................................................................ 5-7

5.9 Deviations from SI QAPP Addendum ..................................................................... 5-7

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

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

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

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

6.4.2 AOI 2 Groundwater Analytical Results ......................................................... 6-4

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

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

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

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

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

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

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

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

6.6.3 AOI 4 Conclusions........................................................................................ 6-7

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

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

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

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

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

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

7.2 Groundwater Exposure Pathway ............................................................................ 7-3

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

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

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

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

7.3 Surface Water and Sediment Exposure Pathway................................................... 7-4

7.3.1 AOI 1 ............................................................................................................ 7-4

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

7.3.3 AOI 3 ............................................................................................................ 7-5

7.3.4 AOI 4 ............................................................................................................ 7-5

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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General Lucius D. Clay National Guard Center, Georgia 

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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. Nonconformance and Corrective Action Reports 

B5. Survey Data 

B6. Investigation-Derived Waste Polygons 

Appendix C Photographic Log 

Appendix D TPP Meeting Minutes 

Appendix E Boring Logs 

Appendix F Analytical Results 

Appendix G Laboratory Reports 

Figures 

Figure 2-1 Facility Location 

Figure 2-2 Facility Topography 

Figure 2-3 Groundwater Features 

Figure 2-4 Groundwater Elevations, July-October 2021 

Figure 2-5 Surface Water Features 

Figure 3-1 Areas of Interest 

Figure 3-2 Adjacent Sources 

Figure 5-1 Site Inspection Sample Locations – South Property 

Figure 5-2 Site Inspection Sample Locations – North Property 

Figure 6-1 PFOA Detections in Soil 

Figure 6-2 PFOS Detections in Soil 

Figure 6-3 PFBS Detections in Soil 

Figure 6-4 PFHxS Detections in Soil 

Figure 6-5 PFNA Detections in Soil 

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

Figure 6-7 PFHxS and PFNA Detections in Groundwater 

Figure 7-1 Conceptual Site Model, AOI 1 

Figure 7-2 Conceptual Site Model, AOI 2 

Figure 7-3 Conceptual Site Model, AOI 3 

Figure 7-4 Conceptual Site Model, AOI 4 

Tables 

Table ES-1 Screening Levels (Soil and Groundwater) 

Table ES-2 Summary of Site Inspection Findings and Recommendations 

Table 3-1 Adjacent Sources 

Table 5-1 Site Inspection Samples by Medium 

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

Elevations 

Table 6-1 Screening Levels (Soil and Groundwater) 

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

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

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

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

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

% percent

°C degrees Celsius

°F degrees Fahrenheit

μg/kg micrograms per kilogram

AASF Army Aviation Support Facility

AECOM AECOM Technical Services, Inc.

AFFF aqueous film forming foam

AOI Area of Interest

ARB Air Reserve Base

ARNG Army National Guard

bgs below ground surface 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CoC chain of custody

CSM conceptual site model 

DA Department of the Army

DoD Department of Defense

DO dissolved oxygen

DPT direct push technology

DQO data quality objective

DUA data usability assessment

EDRTM Environmental Data Resources, Inc.TM

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

FedEx Federal Express

FTA Fire Training Area

GAARNG Georgia Army National Guard

GPS global positioning system

GRPS Ground Penetrating Radar Systems

HA Health Advisory

HDPE high-density polyethylene 

HFPO-DA hexafluoropropylene oxide dimer acid

IDW investigation-derived waste

ITRC Interstate Technology Regulatory Council

LC/MS/MS liquid chromatography with tandem mass spectrometry

MIL-SPEC military specification

MS matrix spike 

MSD matrix spike duplicate

NAS Naval Air Station

NELAP National Environmental Laboratory Accreditation Program

NGC National Guard Center

ng/L nanograms per liter

NPDES National Pollutant Discharge Elimination System

ORP oxidation-reduction potential
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General Lucius D. Clay National Guard Center, Georgia

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OSD Office of the Secretary of Defense

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PID photoionization detector

PQAPP Programmatic UFP-QAPP

PVC polyvinyl chloride

QA quality assurance

QAPP Quality Assurance Project Plan

QC quality control

QSM Quality Systems Manual

RI Remedial Investigation

RSL Regional Screening Level

SI Site Inspection

SL screening level

SOP standard operating procedure

TCE trichloroethylene

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

USGS United States Geological Survey

WWTP wastewater treatment plant 
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General Lucius D. Clay National Guard Center, Georgia

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Executive Summary

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

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

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 four Areas of Interest (AOIs) where PFAS-containing materials may have been 

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

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

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

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

compounds. This SI was completed at the General Lucius D. Clay National Guard Center (Clay 

NGC) in Marietta, Georgia and determined further evaluation under the Comprehensive 

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

2, AOI 3, and AOI 4. The Clay NGC will also be referred to as the “facility” throughout this 

document. 

Clay NGC is located in Cobb County, approximately 1 mile south of Marietta, Georgia and 

approximately 20 miles northwest of Atlanta, Georgia. It is adjacent to the Dobbins Air Reserve 

Base (ARB) and Air Force Plant 6 (currently operated by Lockheed Martin). Clay NGC is 

constructed on a parcel of land that has been owned and operated by the Georgia ARNG 

(GAARNG) since 2009. From approximately 1943 to 2009, the property was owned by the US

Navy and designated as Naval Air Station (NAS) Atlanta. Collocated, Dobbins ARB and Air Force 

Plant 6 began operations in the early 1940s. The NAS Atlanta property was transferred to the 

GAARNG, who established the Clay NGC at the location, in 2009. The southern portion of the 

Clay NGC is located south of the runway and includes several hangars, storage buildings, and 

administrative offices. The northern portion of the Clay NGC is located north of the runway and 

includes Building 555 at the location of the former GAARNG Army Aviation Support Facility 

(AASF). The former AASF operated from 1983 until 2011, and it is currently leased from Dobbins 

ARB to the GAARNG on an indefinite term. 

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

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

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

(RI) for AOI 1, AOI 2, AOI 3, and AOI 4. 

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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General Lucius D. Clay National Guard Center, Georgia

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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 

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 Hangar 1/Ramp Area Proceed to RI 

2 Hangar 300 Proceed to RI

3 Hangar 312 Proceed to RI

4 Building 555 Proceed to RI

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected

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. 
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General Lucius D. Clay National Guard Center, Georgia

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1. Introduction

1.1 Project Authorization

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

(PAs) and Site Inspections (SIs) on the current or potential historical use of 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 General Lucius D. 

Clay National Guard Center (Clay NGC) in Marietta, Georgia. Clay NGC 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 Clay NGC (AECOM Technical Services, Inc. [AECOM], 2020) that

identified four Areas of Interest (AOIs) where PFAS-containing materials may have been used, 

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

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

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

no further action is required based on screening levels (SLs) for the relevant compounds. 

1

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

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

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

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

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

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

2.1 Facility Location and Description 

Clay NGC is in Cobb County, approximately 1 mile south of Marietta, Georgia (Figure 2-1) and 

approximately 20 miles northwest of Atlanta, Georgia. Clay NGC is adjacent to the Dobbins Air 

Reserve Base (ARB) and Air Force Plant 6 (currently operated by Lockheed Martin). The facility 

is accessible from Halsey Avenue from the east, Richardson Road from the south, and Atlantic 

Avenue from the west.

Clay NGC is constructed on a parcel of land that has been owned and operated by the Georgia 

ARNG (GAARNG) since 2009. From approximately 1943 to 2009, the property was owned by the 

US Navy and designated as Naval Air Station (NAS) Atlanta. Collocated Dobbins ARB and Air 

Force Plant 6 began operations in the early 1940s. The NAS Atlanta property was transferred to 

the GAARNG, who established the Clay NGC at the location, in 2009. The southern portion of the 

Clay NGC is located south of the runway and includes several hangars, storage buildings, and 

administrative offices.

The northern portion of the Clay NGC is located north of the runway and includes Building 555, 

at the location of the former GAARNG Army Aviation Support Facility (AASF). The former AASF 

operated from 1983 until 2011, and it is currently leased from Dobbins ARB to the GAARNG on 

an indefinite term. 

2.2 Facility Environmental Setting

Clay NGC lies within the Central Uplands district, which is characterized by low ridges and large, 

open valleys, with streams 150 to 200 feet below the ridge crests; the streams are generally 

transverse to the underlying geologic structure. Clay NGC is located on a rolling plateau, with 

streams and rivers throughout. The Rottenwood and Poorhouse Creeks are some of the 

predominant stream channels near the facility. The plateau is sloped gradually downward to the 

southeast (Aerostar SES LLC, 2018a and 2018b), and the elevation of the facility is approximately 

1,082 feet above mean sea level (Figure 2-2). 

2.2.1 Geology

Clay NGC is underlain by the Powers Ferry Formation, which consists of intercalated gneiss, 

schist, and amphibolites in decreasing abundance. The Powers Ferry Formation is estimated to 

be more than 3,290-feet thick and dates form the late Precambrian and early Paleozoic eras. 

More specifically, the geology in the region includes mafic gneiss that is primarily composed of 

iron-magnesium silicates, such as amphibolite, hornblende gneiss, and mafic hornblende; biotite 

gneiss is also found in the region. These crystalline rocks are composed of metamorphic rock that 

display gneissic banding, strong foliation, and relatively high biotite-mica content (Georgia 

Department of Natural Resources, 1977). 

The surface soils have a sand-like consistency from micaceous silts and micaceous sandy silts 

originating from the weathering of underlying rock. The subsoils are characterized as a clay loam 

horizon. Overall, red-yellow podzolic soils persist, and in many areas, there are loose rock 

fragments scattered over the surface and outcrops of bedrock (Federal Emergency Management 

Agency, 2013). Local geologic units are shown on Figure 2-3. 

Borings completed as a part of this SI were drilled to depths between 19 and 45 feet below ground 

surface (bgs) where groundwater was encountered. The geologic data collected from the 

boreholes indicate that the lithology of the unconsolidated sediments underlying Clay NGC ranges 
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from lean and fat clays to silty/clayey sands to well-graded sands. Silts and clays were 

predominantly observed from surface to 10 feet bgs with underlying coarser grained sediments 

(sands). At the former AASF, no clay or silt units were observed and fines were only observed in 

minor amounts within the sand-dominated lithologies. 

Many of the logs also reported weathered bedrock (saprolite) present near the groundwater table. 

Saprolite was encountered at depths ranging from 10 to 26 feet bgs on the Clay NGC southern 

property. Refusal due to bedrock was encountered at five out of eleven (11) borings across the 

facility ranging from 2 to 39 feet bgs. 

2.2.2 Hydrogeology

Clay NGC is in the northern Piedmont Physiographic Province, which consists of surficial water 

tables and aquifers within the bedrock. Clay NGC is also within the Rottenwood Creek watershed, 

which drains into the Chattahoochee River. The Chattahoochee River flows generally to the south. 

The residual soil and fragmented bedrock below the ground surface provide the primary pathway 

for groundwater flow. The groundwater occurs within joints and fractures in the bedrock and in the 

pore spaces of the residual soils. Aquifer recharge is predominantly through infiltration of 

precipitation, although some recharge occurs from open water sources. Depth to groundwater 

ranges from 12 feet bgs in the eastern region of the province to 60 feet bgs in the western region 

of the province (Stell, 2012). 

No potable water wells are located within the boundary of the Clay NGC northern and southern 

properties; however, US Geological Survey (USGS) wells and Georgia Department of Public 

Health wells exist within four miles of the facility (USGS, 2022) (Figure 2-3). No domestic or 

drinking well information was available during the PA, but Dobbins ARB personnel stated that 

wells within 1 mile of the facility are used for monitoring and irrigation. Drinking water for the Clay 

NGC is supplied by the Air Force Plant 6 drinking water distribution, which is supplied by the Cobb 

County-Marietta Water Authority. The Cobb County-Marietta Water Authority, which serves the 

area surrounding the Clay NGC, uses the Chattahoochee River and Lake Allatoona as its drinking 

water sources (Marietta Water, 2017). There is no groundwater or reclaimed water used for 

irrigation at the facility.

According to an Environmental Data Resources, Inc.TM (EDRTM) report performed as part of SIs 

for PFAS at the Dobbins ARB and Air Force Plant 6, there is one public water supply well listed 

within 2 to 3 miles northwest of the Dobbins ARB; however, the well address listed is the mailing 

address of the well operator rather than the well itself (Aerostar SES LLC, 2018a and 2018b). 

Groundwater is not used as a drinking water source at Clay NGC or its surrounding areas.

Groundwater flow within the unconsolidated surficial aquifer at the facility is influenced by surface 

topography and surface water bodies. In general, surface topography across the former AASF 

slopes in the southeastern direction towards the facility boundary and to Big Lake. There is an 

approximately 15-foot drop in elevation from the Building 555 area to the eastern edge of the 

former AASF. The topographic slope and nearby Big Lake likely act as a draw on groundwater 

flow. On the facility’s southern property, topography generally slopes north towards the runway 

on the northern half of the ramp area and slopes to the east and west at those respective ends of 

the ramp. At Hangar 312, there is an approximately 15-foot drop from the building area to the 

retention basin immediately to the west that likely acts as a draw on groundwater flow. On the 

southern half of the ramp area, topography generally slopes to the southeast, with an 

approximately 20-foot drop in elevation from the Hangar 300 building area to the retention basin 

at the southeastern facility boundary. 

Synoptic groundwater measurements were recorded during the SI from the existing monitoring 

wells and installed temporary wells. The depth to groundwater across both the northern and 

southern properties ranged between approximately 10.52 to 33.18 feet bgs. 
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In the northern property (location of AOI 4), depth to groundwater ranged between 24.07 to 29.95 

feet bgs. In the southern property (locations of AOI 1, AOI 2, AOI 3, and potentially upgradient 

monitoring wells CNGC-01 and CNGC-MW030), depth to groundwater ranged between 

approximately 10.52 to 33.18 feet bgs. The maximum depth to groundwater in the southern 

property was observed at existing monitoring well CNGC-MW030 located at the western boundary 

of the southern property. The minimum depth to groundwater was observed at CNGC-01, located 

in the north central portion of the southern property. Based on these observations, groundwater 

generally appeared to be shallower at the southern property at the time of synoptic gauging.

Within the vicinity of AOI 1 and 2 on the southern property, groundwater flows southeast, towards 

the retention basin in the southeast corner of the facility. At AOI 3, groundwater appears to flow 

west towards the retention basin located west of Hangar 312. On the western half of the Clay 

NGC southern property, groundwater flows east towards the retention basin located west of 

Hangar 312. Sample locations CNGC-01 and CNGC-MW030 were selected as upgradient 

locations for AOIs 1, 2, and 3; however, it is uncertain whether the sample locations are truly 

upgradient due to the convergence of groundwater flow towards the retention basin west of 

Hangar 312. At the former AASF north of the runway (AOI 4), groundwater flows east towards Big 

Lake. The observed groundwater flow directions reflect surface topography (Figure 2-4). 

2.2.3 Hydrology

The Clay NGC southern property has a freshwater pond to the south and Poorhouse Creek to the 

east (Figure 2-5). Poorhouse Creek is located less than 1.5 miles east of the southern property. 

Poorhouse Creek is a tributary to the Chattahoochee River, which spans a total of 430 miles from 

the northernmost part of Georgia and down to the south, along the Alabama-Georgia border. The 

overland flow at the facility southern property is predominantly in the southeast direction. A 

drainage ditch runs along the eastern boundary of Clay NGC southern property and terminates 

into a retention basin with a storm drain that discharges into Poorhouse Creek, which ultimately 

discharges to the Chattahoochee River. The Chattahoochee River is approximately 4.3 miles to 

the east of the facility and flows from north to south.

In the eastern portion of the southern property, surface water runoff on the main ramp is divided 

between the northern and southern halves of the ramp area. On the northern half, runoff flows 

north and off the ramp, into a drainage ditch that channels runoff east, and then south towards 

the aforementioned retention basin in the southeastern corner of the facility. Surface water runoff 

on the southern half of the ramp flows south and east towards the retention basin. Another 

retention basin is located west of Hangar 312, off-facility. Runoff entering this retention basin 

predominantly flows north via an underground pipe beneath the runway and discharges into Big 

Lake, a water body located on Dobbins ARB property. 

Surface water runoff in the former AASF north of the runway also drains to Big Lake, which is 

located 0.2 miles east of Building 555. Big Lake drains to Rottenwood Creek via Dobbins Spill 

Pond 4. Rottenwood Creek is located less than 1 mile of the northeast of the northern property. 

2.2.4 Climate

The climate at Clay NGC consists of four clearly separated seasons, with predominant weather 

movement from west to east. Temperatures vary from average highs of 70.5 degrees Fahrenheit 

(°F) to average lows of 49.8 °F. The average annual temperature is 62.5 °F. Average precipitation 

is 54.4 inches of rain (World Climate, 2022). 
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AECOM 2-4

2.2.5 Current and Future Land Use

The Clay NGC is a controlled access facility with public roads and is adjacent to the Dobbins ARB 

and Air Force Plant 6 . Reasonably anticipated future land use is not expected to change from the 

current land use; however, future infrastructure improvements, land acquisitions, and land use 

controls at Dobbins ARB and Air Force Plant 6 are unknown. 

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

The following insects, plants, mammals, fishes and clams are federally endangered, threatened, 

proposed, and/ or are listed as candidate species in Cobb County, Georgia (US Fish and Wildlife 

Service [USFWS], 2022). 

• Insects: Monarch butterfly, Danaus plexippus (candidate)

• Mammals: Tricolored bat, Perimyotis subflavus (under review); Northern long-eared bat, 

Myotis septrenionalis (threatened); Little brown bat, Myotis lucifugus (under review)

• Flowering plants: Georgia aster, Symphyotrichum georgianum (resolved taxon); 

Michaux’s sumac, Rhus michauxii (endangered); Little amphianthus, Amphianthus pusillus

(threatened); White fringeless orchid, Platanthera integrilabia (threatened); Georgia 

rockress, Arabis georgiana (threatened)

• Fishes: Lake sturgeon, Acipenser fulvescens (under review); Cherokee darter, Etheostoma 

scotti (threatened)

• Clams: Delicate spike, Elliptio arctata (under review)

2.3 History of PFAS Use 

PFAS were potentially released to soil and groundwater within the boundary of Clay NGC through 

releases from hangar fire suppression systems and wheeled fire extinguishers. Four AOIs were 

identified based on preliminary data and assumed groundwater flow directions (Figure 2-4). A 

description of the four AOIs is presented in Section 3. In addition to the identified AOIs, Clay NGC 

is surrounded on all sides by Dobbins ARB and the Air Force Plant 6 (currently operated by 

Lockheed Martin), which are a part of a much larger military complex. The industrial areas 

associated with the campuses of the Dobbins ARB and Air Force Plant 6 have been historically 

used for the manufacturing, maintenance and modification of military aircrafts (Aerostar, 2018a 

and 2018b). Numerous potential release areas associated with each campus have been identified 

upgradient and downgradient of Clay NGC. It is possible that PFAS from releases on these 

campuses are migrating onto Clay NGC property. 
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Geology

Ropes Creek Metabasalt; Informal unit

of mixed metamorphic assemblage

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assemblage

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Mountain; Cider Gneiss

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metamorphic assemblage

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gneiss

Factory Shoal Formation

Undifferentiated garnet-mica schist

Amphibolite of Powers Ferry Formation

Mica schist, gneiss, and amphibolite of

Powers Ferry Formation

Aluminous schist of Powers Ferry

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Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 2-10

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Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

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, four potential release areas were 

identified at Clay NGC and grouped into four AOIs (AECOM, 2021a). The potential release areas 

are shown on Figure 3-1. 

3.1 AOI 1 Hangar/Ramp Area

AOI 1 is the Hangar 1/Ramp Area at Clay NGC. Hangar 1 was constructed in 1959 and contains 

a fire suppression system that formerly consisted of eight 150-gallon tanks filled with 3% AFFF 

concentrate. There is no information available regarding when the AFFF fire suppression system 

was installed; however, the system was in place when the GAARNG took over the facility in 2009. 

The fire suppression system has been disabled, and the AFFF tanks intact with their AFFF 

contents were removed from the hangar during winter 2020. The tanks were transported from 

Hangar 1 to a hazardous waste storage building on the southeastern corner of the ramp area. 

The tanks are stored on secondary containment structures within the building to prevent spills or 

leaks from escaping. There is no information available on the fire suppression system installation, 

testing frequency of the system, or releases. The wash rack near Hangar 1 currently drains to the 

industrial WWTP and then to the sanitary WWTP. No information was available regarding 

historical activities at the wash rack or whether there were a different drain configuration in the 

past. 

3.2 AOI 2 Hangar 300 

AOI 2 is Hangar 300 at Clay NGC. Hangar 300 was built in the early 1990’s and contains a fire 

suppression system supplied by two 1500-gallon tanks filled with AFFF concentrate. The AFFF 

tanks and pumps that supply the fire suppression system are housed within the hangar. Two 

known releases of AFFF from the fire suppression system have occurred. Both releases occurred 

in the early to mid-2000s, prior to GAARNG assuming occupancy of the building. During both 

releases, foam was released in the hangar, pushed onto the ramp, and ultimately into the retention

basin east of Hangar 300. The retention basin contains a storm drain that discharges into 

Poorhouse Creek, which is a tributary of Rottenwood Creek. The Rottenwood Creek discharges 

to the Chattahoochee River. The concentration of AFFF and volume of the releases are unknown. 

The hangar is outfitted with trench drains that drain to the industrial WWTP and then to the 

sanitary WWTP. 

3.3 AOI 3 Hangar 312

AOI 3 is Hangar 312 at Clay NGC. Hangar 312 was built in 1998 and contains a fire suppression 

system supplied by a 300-gallon tank containing 3% of AFFF low expansion foam. The AFFF tank 

and pumps that supply the fire suppression system are housed in a room within the hangar that 

contains a floor drain that drains to the industrial WWTP and then the sanitary WWTP. During the 

PA site visit, evidence of corrosion down the side of the tank was observed, and the gasket 

between the tank and the outline piping appeared to have been replaced with a gasket not 

intended for the fitting and that stuck out on the sides. 

If there were releases of AFFF at AOI 3, the concentration and volume would be unknown. 

Potential releases to surface soil may have migrated to groundwater via leaching and surface 

water. Based on groundwater and surface water flow direction, potential releases may have 

drained to a retention basin directly west of Hangar 312 then channeled to the north, beneath the 

runway, via an underground pipe before ultimately discharging to Big Lake on the Dobbins ARB 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-2

property. Big Lake discharges to Rottenwood Creek via Dobbins Spill Pond 4, and the Rottenwood 

Creek discharges to the Chattahoochee River. 

3.4 AOI 4 Building 555

AOI 4 is Building 555 and was the location of the former GAARNG AASF from 1983 until 2011. 

The former hangar did not have a fire suppression system, and no information was available 

regarding the use or presence of AFFF at the former GAARNG AASF. Historical aerial 

photographs show evidence of portable fire extinguisher units on the ramp, but it is unknown if 

the portable units contained AFFF. Dobbins ARB personnel stated that no reported AFFF releases 

were recorded by the Dobbins Fire Department for the former AASF, and that portable 

extinguishers used on flightline areas were usually 150-pound halon extinguishers. If there were 

releases of AFFF at AOI 4, the concentration and volume would be unknown. It is also possible 

that releases to adjacent areas discussed in Section 3.5 and shown on Figure 3-2 may have 

impacted environmental media at AOI 4. Potential releases to surface soil at AOI 4 may have 

migrated to groundwater via leaching and surface water. Based on the groundwater and surface 

water flow direction, potential releases may have ultimately drained to the body of water east of 

the former GAARNG AASF known as Big Lake. Big Lake drains to Rottenwood Creek via the 

Dobbins Spill Pond 4, and the Rottenwood Creek discharges to the Chattahoochee River. 

3.5 Adjacent Source Information

In 2018, Aerostar SES LLC completed SIs for PFAS at the Air Force Plant 6 and Dobbins ARB 

(Aerostar, 2018a and 2018b). Thirty-one (31) off-site PFAS sources up- and downgradient of the 

Clay NGC were identified during the PFAS investigations of the Air Force Plant 6 and Dobbins 

ARB. PFAS were detected in surface soil, subsurface soil, surface water, and groundwater across 

the investigation areas, and 27 areas were recommended to proceed to Remedial Investigation 

(RI). Table 3-1 summarizes the findings of the SIs completed at Air Force Plant 6 and Dobbins 

ARB. Figure 3-2 presents the location of potential Clay NGC adjacent source areas. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-3

Table 3-1: Adjacent Sources

Map 

ID Area Description SI Findingsa,b

1 & 2 Sanitary 

Wastewater 

Treatment 

Plant 

(WWTP)* 

This WWTP is a collection 

point for all the sanitary 

sewage systems within the 

installation and an industrial 

WWTP effluent. The WWTP 

effluent discharges into the 

Nickajack Creek in an offinstallation residential area.

PFAS levels in surface soil, 

groundwater, and surface water 

exceeded the 2016 USEPA Health 

Advisory (HA) screening criteria. 

Recommended to proceed to an RI.

3 Industrial 

WWTP* 

A confirmed aqueous film 

forming foam (AFFF) release 

occurred at the former 

Industrial WWTP aeration 

pond. The industrial WWTP is 

used as a collection point for 

manufacturing wastewater 

treatment

PFAS levels in groundwater and 

surface water exceeded the 2016 

USEPA HA screening criteria. 

Recommended to proceed to an RI. 

4 Fire 

Prevention 

Headquarters 

(B-102)* 

This facility has an AFFF fire 

suppression system and was 

originally used as a 

manufacturing facility. 

PFAS levels in groundwater and 

surface soil exceeded the 2018 

USEPA Regional Screening Level 

(RSL)/2016 HA screening criteria. 

Recommended to proceed to an RI.

5 Corporate 

Hangar (T728)* 

The hangar previously stored 

55-gallon drums of AFFF, and

there was a confirmed

release of AFFF.

PFAS levels in groundwater 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI.

6 Fire Station 

#1 (B-4)* 

An active fire station that 

stores AFFF equipment and 

vehicles. An AFFF release 

inside the fire hall due to 

leaking equipment was 

reported. 

PFAS levels in groundwater 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI. 

7 C-5 Fuel

System Test 

Facility (B96)* 

The C-5 fuel system contains 

an AFFF fire suppression 

system that has had a 

confirmed release that leaked 

out of the facility. 

PFAS levels in subsurface soil and 

groundwater exceeded the 2018 

USEPA RSL/2016 HA screening 

criteria. Recommended to proceed to 

an RI.

8 Outfall 1* Outfall 1 is the surface water 

collection and National 

Pollutant Discharge 

Elimination System (NPDES) 

discharge point for Drainage 

Basin 1, which has reported 

AFFF releases.

PFAS not detected above the 

screening criteria. No further action 

recommended. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-4

Map 

ID Area Description SI Findingsa,b

9 Outfall 2* Outfall 2 is the surface water 

collection and NPDES 

discharge point for Drainage 

Basin 2, which has reported 

AFFF releases.

PFAS levels in surface water 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI. 

10 Structural Fire 

Training Area

(FTA) (B-64)* 

This FTA was constructed in 

2003 and uses liquid propane 

gas as a fuel source. The 

training exercises release 2 

to 3 gallons of AFFF per 

event.

PFAS not detected above the 

screening criteria in soil. 

Recommended to proceed to an RI 

based on lack of groundwater 

sampling.

11 Fire Station 

#2 (B-69)* 

This is an active fire station 

that stores AFFF-containing 

equipment and vehicles. An 

AFFF release inside the fire 

hall due to leaking equipment 

was reported.

PFAS not detected above the 

screening criteria. No further action 

recommended. 

12 C-5 Engine

Fire*

An unknown amount of AFFF 

was released to extinguish an 

engine fire. 

PFAS levels in ground water, and 

surface water exceeded the 2016 

USEPA HA screening criteria. 

Recommended to proceed to an RI.

13 AFFF Spray 

Test Area* 

The spray test area was used 

for annual testing of AFFF 

containing 

equipment/vehicles where 

approximately 2,200 gallons 

of AFFF have been 

discharged each test. The 

total volume of AFFF 

released over time and the 

dates of testing are unknown.

PFAS levels in surface soil, ground 

water, and surface water exceeded 

the 2018 USEPA RSL/2016 HA 

screening criteria. Recommended to

proceed to an RI. 

14 Outfall 5* Outfall 5 is the surface water 

collection and NPDES 

discharge point for Drainage 

Basin 5, which has reported 

AFFF releases.

PFAS levels in surface water 

exceeded 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI. 

15 Hangar 5** The hangar has an AFFF fire 

suppression system that 

reported two releases in the 

1990s, one release of 600 

gallons of AFFF concentrate 

and one release of 5,000 

gallons of AFFF/water 

mixture. Both releases 

occurred outside the hangar.

PFAS levels in surface soil exceeded 

the 2018 USEPA RSL screening 

criteria. Recommended to proceed to

an RI. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-5

Map 

ID Area Description SI Findingsa,b

16 Motor Pool 

Facility 

(Building 

516)**

A release of 2 to 5 gallons of 

AFFF occurred outside 

building on pavement and 

may have migrated to a 

nearby wooded area.

PFAS levels in surface soil, 

subsurface soil, and groundwater 

exceeded the 2018 USEPA 

RSL/2016 HA screening criteria. 

Recommended to proceed to an RI.

17 Big Lake (OT04)**Visual confirmation of AFFF 

spilling into the Big Lake from 

Building 5 with an unknown 

volume of AFFF. Big Lake 

discharges directly into an 

unnamed tributary of 

Rottenwood Creek. Fish 

were confirmed dead 

following the release.

PFAS levels in surface water and 

groundwater exceeded the 2016 

USEPA HA screening criteria. 

Recommended to proceed to an RI. 

18 L-100-20

Hercules

Crash**

A release of approximately 

1,000 gallons of AFFF/water 

mixture was applied to 

several fires from a crash in 

February 1993.

PFAS levels in surface soil and 

groundwater exceeded the 2018 

USEPA RSL/2016 HA screening 

criteria. Recommended to proceed to 

an RI.

19 Former FTA 

FT-03**

This FTA was operational 

from 1974 to the late 1980s. 

Unknown quantities of AFFF 

were used. AFFF was 

introduced to the Air Force in 

1970.

PFAS levels in surface soil, 

subsurface soil, and groundwater 

exceeded the 2018 USEPA 

RSL/2016 HA screening criteria. 

Recommended to proceed to an RI. 

20 L-188CF

Electra

Crash**

An unknown quantity of AFFF 

was potentially applied to a 

crash that occurred in 

January 1985.

PFAS levels in groundwater 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI.

21 Spill Pond 3** Visual confirmation of an 

unknown type of foam spilling 

into the unlined pond from an 

unknown source. The depth 

to groundwater in the pond is 

5 feet bgs. The pond 

discharges directly into a 

tributary of Rottenwood 

Creek. Fish were confirmed 

dead following the release.

PFAS levels in surface water and 

groundwater exceeded the 2016 

USEPA HA screening criteria. 

Recommended to proceed to an RI. 

22 Building 746 

(Hangar)**

The hangar had an AFFF fire 

suppression system that 

reported a release of up to 

1,500 gallons of AFFF that 

occurred between 1999 to 

2004. The release flowed 

outside the hangar.

PFAS levels in groundwater 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-6

Map 

ID Area Description SI Findingsa,b

23 L-188CF

Electra Crash 

Alternate 

Site**

An unknown quantity of AFFF 

was potentially applied to a 

crash that occurred in 

January 1985.

PFAS levels in groundwater 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI.

24 Former FTA 

FT-02**

This FTA was operational 

from the early 1950s to 1974 

and is constructed of an 

unlined, earthen pit. Potential 

unknown quantities of AFFF 

were used. AFFF was 

introduced to the Air Force in 

1970.

PFAS levels in surface soil and 

groundwater exceeded the 2018 

USEPA RSL/2016 HA screening 

criteria. Recommended to proceed to

an RI. 

25 Current Fire 

Station 

(Building 

745)**

A known release occurred 

during resupply activities 

outside the building. Prior to 

1999, the potential AFFF 

release occurred during fire 

engine cleaning activities 

outside the building. The 

quantity of AFFF released is 

unknown.

PFAS levels in surface soil and 

groundwater exceeded the 2018 

USEPA RSL/2016 HA screening 

criteria. Recommended to proceed to

an RI. 

26 Spill Pond 4** A quantity of up to 1,500 

gallons of AFFF was released 

from Building 731 and flowed 

into the unlined pond. The 

depth to groundwater in the 

pond is 5 feet bgs. The pond 

discharges directly into an 

unnamed tributary of 

Rottenwood Creek. Fish 

were confirmed dead 

following the release.

PFAS levels in surface water, and 

groundwater exceeded the 2016 

USEPA HA screening criteria. 

Recommended to proceed to an RI. 

27 Building 731** This hangar formerly had an 

AFFF fire suppression 

system. A release of up to 

1,500 gallons of AFFF 

occurred in 1999 and flowed 

outside the hangar toward 

grass areas. Another release 

of AFFF occurred in a 

mechanical room and spilled 

into the building drainage 

system.

PFAS levels in surface soil and 

groundwater exceeded the 2018 

USEPA RSL/2016 HA screening 

criteria. Recommended to proceed to

an RI. 

28 E-2 Tire Fire** Approximately 50 to 100 

gallons of AFFF/water 

mixture were used to 

extinguish a tire fire, and 

PFAS may have migrated to 

grassed areas nearby.

PFAS not detected above the 

screening criteria. No further action 

recommended. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-7

Map 

ID Area Description SI Findingsa,b

29 F-18 Tire

Fire**

Approximately 100 gallons of 

AFFF/water mixture were 

used to extinguish a tire fire, 

and PFAS may have 

migrated to grassed areas 

nearby.

PFAS not detected above the 

screening criteria. No further action 

recommended.

30 AFFF Spray 

Test Area**

The spray test area was used 

for annual testing, where 

approximately 100 gallons of 

3 percent (%) AFFF/water 

mixture were discharged per 

year. The total volume of 

AFFF released over time and 

dates of testing are unknown.

PFAS levels in surface soil and 

groundwater exceeded the 2018 

USEPA RSL/2016 HA screening 

criteria. Recommended to proceed to

an RI. 

31 C-5A Galaxy

Fire**

An unknown quantity of AFFF 

was potentially applied to a 

fire that occurred in October 

1970.

PFAS levels in groundwater 

exceeded the 2016 USEPA HA 

screening criteria. Recommended to

proceed to an RI.

* Area identified in Aerostar 2018a.

** Area identified in Aerostar 2018b.

a.) Aerostar SES LLC. 2018a. Final Site Inspections Report of Fire Fighting Foam Usage at Air Force Plant 6 Cobb County, Georgia. 

October. 

b.) Aerostar SES LLC. 2018b. Final Site Inspections Report of Fire Fighting Foam Usage at Dobbins Air Reserve Base Cobb County, 

Georgia. October.
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 3-8

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Rott enwood Creek

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AFFF Inspection Area

Airforce Plant 6 Boundary

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Area of Interest

Potential Release Area

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Wash Rack

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Areas of Interest

12420 Milestone Center Drive

Germantown, MD 20876

Area of Interest

AFFF Inspection Area

Potential Release Area

Facility Boundary

Fomer ARNG AASF Boundary

Airforce Plant 6 Boundary

Dobbins ARB Boundary

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SI

10/10/2022

10/10/2022

Site Inspection at Clay National Guard Center, GA

10/10/2022

1:25,200 ­ Figure 3-2 PM CM 10/10/2022

12420 Milestone Center Drive

Germantown, MD 20876

Adjacent Sources

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

and the GIS User Community

0 1,050 2,100 4,200

Feet

Legend

AFFF Inspection Area

Facility Boundary

Fomer ARNG AASF Boundary

Airforce Plant 6 Boundary

Dobbins ARB Boundary

Water Body

River/Stream

PROJECT

AECOM 3-10
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

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 AOIs identified in the PA. For each 

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

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

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

AOIs.

4.1 Problem Statement 

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

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

SLs are presented in Section 6.1 of this report. 

4.2 Information Inputs

Primary information inputs included:

• The PA for Clay NGC, Georgia (AECOM, 2020);

• Analytical data collected as part of other environmental sampling efforts at Clay NGC;

• 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 current location of Clay NGC and the 

former GAARNG AASF north of the runway (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). 

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 
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General Lucius D. Clay National Guard Center, Georgia

AECOM 4-2

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

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

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

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

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

 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

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, General Lucius D. Clay National Guard Center,

Georgia dated February 2020 (AECOM, 2020);

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

General Lucius D. Clay National Guard Center, Georgia dated April 2021 (AECOM, 2021a);

and

• Final Site Safety and Health Plan, General Lucius D. Clay National Guard Center, Georgia

dated July 2021 (AECOM, 2021b).

The SI field activities were conducted during two mobilizations: the first mobilization took place on

27 May 2021 and 12 July through 16 July 2021, while the second mobilization took place from 29 

September through 1 October 2021 and 20 October 2021. Activities during the first mobilization 

consisted of utility clearance, direct push boring, soil sample collection, temporary monitoring well 

installation, grab groundwater sample collection, and land surveying at the Clay NGC southern 

property. Permission to work on the former GAARNG AASF required a signed Dobbins ARB Civil 

Engineering Dig permit, which was not received until 27 July 2021. As a result, a second 

mobilization was necessary to complete direct push boring, soil sample collection, temporary 

monitoring well installation, grab groundwater sample collection, and land surveying at AOI 4. Field 

activities were conducted in accordance with the SI QAPP Addendum (AECOM, 2021a), except as 

noted in Section 5.9. 

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

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

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

• Thirty (30) soil samples from 11 boring locations;

• Eleven (11) grab groundwater samples from nine temporary well locations and two

permanent monitoring wells;

• Twenty one (21) quality assurance (QA)/quality control (QC) samples.

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

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

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

in Appendix B1. Sampling forms are provided in Appendix B2, Field Change Request Forms 

are provided in Appendix B3, Nonconformance and Corrective Action Reports are provided in 

Appendix B4, land survey data are provided in Appendix B5, and investigation-derived waste 

(IDW) polygons are provided in Appendix B6. Additionally, a photographic log of field activities is 

provided in Appendix C. 
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-2

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 

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 23 February 2021, prior to SI field activities. The 

combined TPP Meeting 1 and 2 was conducted in general accordance with EM 200-1-2. The 

stakeholders for this SI include the ARNG, GAARNG, USACE, and Georgia Environmental 

Protection Division. 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 was held after the field event to discuss the results of the SI. Meeting minutes 

for TPP 3 are included in Appendix D of this report. Future TPP meetings will provide an 

opportunity to discuss the results and findings, and future actions, where warranted. 

5.1.2 Utility Clearance

AECOM placed a ticket with the Georgia 811 “Call Before You Dig” utility clearance provider to 

notify them of intrusive work on 8 June 2021. Georgia 811 confirmed that no conflicts existed 

based on information provided by the one call center. The Georgia 811 ticket was updated 

throughout the duration of field work. 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 on 12 July 2021 with input from the 

AECOM field team. General locating services and ground-penetrating radar were used to 

complete the clearance. The former GAARNG AASF north of the runway, which includes AOI 4, 

also required a signed Dobbins ARB Civil Engineering Dig permit to perform intrusive field 

activities. The signed dig permit was received on 27 July 2021 and was updated throughout the 

duration of the remaining SI field work. 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 Clay NGC was sampled on 27 May 2021 to assess usability for 

decontamination of drilling equipment. Results of the samples collected (CNGC-DECON-01 and 

CNGC-DECON-02) confirmed this source to be acceptable for use in this investigation; therefore, 

it was used throughout the field activities. Specifically, the samples were analyzed by LC/MS/MS 

compliant with QSM 5.3 Table B-15. The results of the decontamination water 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 
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-3

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 

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

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

SI QAPP Addendum (AECOM, 2021a). A GeoProbe® 7822DT dual-tube sampling system was 

used to collect continuous soil cores to the target depth. A hand auger was used to collect soil 

from the top five feet of the boring, in accordance with AECOM utility clearance procedures. The 

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

of the soil cores are included in Appendix C. 

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

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

approximately 2 feet above the groundwater table, and one subsurface soil sample at the midpoint between the surface and the groundwater table. In borings where refusal was encountered 

prior to reaching groundwater, fewer soil samples were collected per boring, in accordance with 

applicable field change requests (Appendix B3). Specifically, only one soil sample was collected 

at location AOI04-01, and only two soil samples were collected at location AOI04-04, for this 

reason. 

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 as a part of this SI were drilled to depths between 19 and 45 feet bgs 

where groundwater was encountered. The geologic data collected from the boreholes indicate 

that the lithology of the unconsolidated sediments underlying Clay NGC ranges from lean and fat 

clays to silty/clayey sands to well-graded sands. Silts and clays were predominantly observed 

from surface to 10 feet bgs with underlying coarser grained sediments (sands). At the former 

GAARNG AASF, no clay or silt units were observed and fines were only observed in minor 

amounts within the sand-dominated lithologies. 

Many of the logs also reported weathered bedrock (saprolite) present near the groundwater table. 

Saprolite was encountered at depths ranging from 10 to 26 feet bgs on the Clay NGC southern 

property. Where refusal was encountered prior to reaching groundwater (AOI04-01 and 

AOI04-04), borings were advanced to depths of 2 and 10.5 feet bgs. Refusal due to bedrock was 

encountered at five out of eleven borings across the facility at depths ranging from 2 to 39 feet.

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 (ASTM D-422) was not performed 

because the sample collected for that analysis, sample GS-AOI02-01, was broken during 

shipment.
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-4

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

as the accompanying samples. Matrix spike (MS)/MS duplicates (MSDs) were collected at a rate 

of 5% and analyzed for the same parameters as the accompanying samples. In instances when 

non-dedicated sampling equipment was used, such as a hand auger for the shallow soil samples, 

equipment rinsate blanks were collected at a rate of 5% and analyzed for the same parameters 

as the soil samples. A temperature blank was placed in each cooler to ensure that samples were 

preserved at or below 6 degrees Celsius (°C) during shipment.

DPT borings were converted to temporary wells, which were subsequently abandoned in 

accordance with the SI QAPP Addendum (AECOM, 2021a) using bentonite chips at completion 

of sampling activities. At location AOI04-02, the borehole was temporarily abandoned on 1 

October 2021 using clean sand for the majority of the column, and bentonite from the surface to 

5 feet bgs. The borehole was over-drilled on 20 October 2021 to remove the clean sand and 

replace it with bentonite in accordance with the SI QAPP Addendum (AECOM, 2021a). Borings 

were installed in grass and gravel areas to avoid disturbing concrete or asphalt surfaces.

5.3 Temporary Well Installation and Groundwater Grab Sampling

Nine temporary wells were installed using a GeoProbe® 7822DT dual-tube sampling system. 

Once the borehole was advanced to the desired depth, wherever conditions allowed, 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. At two locations, AOI04-02 and AOI04-05, a 10-

foot section of 1-inch Schedule 40 PVC was used to improve the likelihood of groundwater 

recharge into the temporary wells. New PVC pipe and screen were used to avoid cross 

contamination between locations. The locations of the temporary wells are shown on Figure 5-1

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

Following installation, the temporary wells were allowed to recharge prior to collection of 

groundwater samples. After the recharge period, groundwater samples were collected using a 

peristaltic pump with PFAS-free HDPE tubing or a QED Sample Pro® bladder pump with 

disposable PFAS-free, HDPE tubing. The temporary wells were purged at a rate determined in 

the field to reduce turbidity and draw down prior to sampling. Water quality parameters (e.g., 

temperature, specific conductance, pH, dissolved oxygen [DO], and oxidation-reduction potential 

[ORP]) were measured using a water quality meter and recorded on the field sampling form 

(Appendix B2) before each grab sample was collected. Additionally, a subsample of each 

groundwater sample was collected in a separate container, and a shaker test was completed to 

identify if there was any foaming. No foaming was noted in any of the groundwater samples. 

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

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

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

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

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

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

same parameters as the accompanying samples. One field reagent blank was collected in 

accordance with the PQAPP (AECOM, 2018a). A temperature blank was placed in each cooler to 

ensure that samples were preserved at or below 6°C during shipment.

Following well surveying (described below in Section 5.6), temporary wells were abandoned in 

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

the hole with bentonite chips. At location AOI04-02, the borehole was temporarily abandoned 

using clean sand and bentonite as described in Section 5.2. The borehole was over-drilled and

re-abandoned with bentonite, in accordance with the SI QAPP Addendum, shortly thereafter. 

Temporary wells were installed in grass and gravel areas to avoid disturbing concrete or asphalt. 
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-5

5.4 Permanent Well Groundwater Sampling

During the SI, groundwater from two existing permanent monitoring wells was sampled. Well, 

CNGC-MW030, is located northwest and potentially upgradient of all known potential release 

areas within Clay NGC. The other well, D6-29, is located downgradient of the potential release 

area at AOI 4. The locations of the wells are shown on Figure 5-1 and Figure 5-2. Samples were 

collected using a QED Sample Pro® bladder pump with disposable PFAS-free, HDPE tubing. 

New tubing was used at each well and the pumps were decontaminated between each well. The

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

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

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

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

groundwater sample was collected in a separate container and a shaker test was completed to 

identify if there 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. MS/MSDs were collected at a rate of 5% and analyzed for the 

same parameters as the accompanying samples. One field reagent blank was collected in 

accordance with the PQAPP (AECOM, 2018a). A temperature blank was placed in each cooler to 

ensure that samples were preserved at or below 6°C during shipment.

5.5 Synoptic Water Level Measurements

A groundwater gauging event was performed for locations sampled during the first SI field 

mobilization between 13 and 15 July 2021. Groundwater elevation measurements were collected 

from the seven new temporary monitoring wells, and two existing permanent monitoring wells 

sampled during the first mobilization. A second groundwater gauging event was held between 30 

September 2021 and 1 October 2021 during the second SI field mobilization for the two remaining 

temporary wells, AOI04-02 and AOI04-05. Water level measurements were taken from the 

northern side of the well casing. A groundwater flow contour map is provided in Figure 2-4, and 

groundwater elevation data are provided in Table 5-2. 

Depth to water at the facility measured during the SI ranges from approximately 10.52 to 33.18 

feet bgs. On the Clay NGC southern property, depth to water measured during the SI at the 

temporary wells installed at or near AOI 1, AOI 2 and AOI 3 ranged from 13.68 to 22.42 feet bgs. 

In general, depth to water was greater at the former AASF north of the runway (ranging from 24.07 

feet bgs to 29.95 feet bgs). However, the deepest depth to water was measured at the western 

boundary of the Clay NGC southern property, at existing monitoring well CNGC-MW030 (33.18 

feet bgs). 

Within the vicinity of AOI 1 and 2 on the southern property, groundwater flows southeast towards 

the retention basin in the southeast corner of the facility. At AOI 3, groundwater appears to flow 

west towards the retention basin located west of Hangar 312. On the western half of the Clay 

NGC southern property, groundwater flows east towards the retention basin located west of 

Hangar 312. At the former AASF north of the runway (AOI 4), groundwater flows east towards Big 

Lake. The observed groundwater flow directions reflect surface topography.
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-6

5.6 Surveying 

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

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

data from the newly installed and existing permanent monitoring wells sampled on the facility 

were collected on 16 July 2021 and 1 October 2021 in the applicable Universal Transverse 

Mercator zone projection with World Geodetic System 84 datum (horizontal) and North American 

Vertical Datum 1988 (vertical). The surveyed well data are provided in Appendix B5. 

5.7 Investigation-Derived Waste 

As of the date of this report, the disposal of IDW is not regulated federally. IDW generated during 

the SI is considered non-hazardous waste and was managed in accordance with the SI QAPP 

Addendum (AECOM, 2021a) and with the DAGuidance for Addressing Releases of PFAS, Q18 (DA, 

2018). 

Solid IDW (i.e., soil cuttings) generated during the SI activities were handled as directed by the 

GAARNG. At soil borings AOI02-01 and AOI02-02, solid IDW was containerized due to the 

presence of a known trichloroethylene (TCE) plume in the vicinity of the borings. At all AOI 4 

boring locations, solid IDW was containerized because the former AASF area is a GAARNG 

enclave on the larger Dobbins ARB property. Containerized solid IDW was stored onsite in two 

55-gallon steel drums and three HDPE food grade 5-gallon buckets. Solid IDW was left in place

at the point of the source at all other boring locations. The soil cuttings were distributed on the

ground surface on the downgradient side of the boring. The solid IDW was not sampled and

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

Based on laboratory results, containerized soil cuttings will be managed and disposed by ARNG,

under a separate contract held by EA Engineering, Science, and Technology, Inc. (EA).

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

handled as directed by the GAARNG. At temporary wells AOI02-01 and AOI02-02, liquid IDW was 

containerized due to the presence the nearby TCE plume. Purge water from existing monitoring 

well CNGC-MW030 was also containerized due to the presence of a sheen on the water and the 

known presence of hydrocarbons in groundwater within the vicinity of the well. Containerized 

liquid IDW is stored onsite in one 15-gallon HDPE drum and one HDPE food grade 5-gallon 

bucket. Liquid IDW from all other temporary and existing monitoring wells was discharged directly 

to the ground surface slightly downgradient of the source. The liquid IDW was not sampled and 

assumes the characteristics of the associated groundwater samples collected from that source 

location. Based on laboratory results, containerized liquid IDW will be managed and disposed by 

ARNG under a separate contract for Treating Liquid Investigation-Derived Material (Purge water, 

drilling water, and decontamination fluids) (EA, 2021).

Geographic coordinates were collected using a global positioning system (GPS) around each 

location where IDW was placed (i.e., an IDW polygon). The IDW polygons are displayed on the 

figure in Appendix B6. 

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 as non-hazardous solid waste to be transported to a licensed solid 

waste landfill. 
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-7

5.8 Laboratory Analytical Methods

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

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

were also analyzed for TOC using USEPA Method 9060A and pH by USEPA Method 9045D. 

5.9 Deviations from SI QAPP Addendum

Several deviations from the SI QAPP Addendum (AECOM, 2021a) were identified during SI field 

activity and during review of the field documentation. The deviations are noted below and 

documented in Field Change Request Forms (Appendix B3) and Nonconformance and 

Corrective Action Reports (Appendix B4): 

• During the utility locate site walk, two boring locations were relocated due to utility and

accessibility restrictions (AOI02-02 and AOI04-02), and one boring was removed due to

ongoing construction (AOI04-03). The original location for AOI04-02 was unintentionally

placed beyond the GAARNG fence line. During the site walk, GAARNG advised moving the

location to within the former AASF fence boundary. The revised location was very close to

the original AOI04-03 location and in the same direction downgradient from the potential

AOI 4 source area. Because of the close proximity between the revised AOI04-02 location

and the AOI04-03 location, and the ongoing construction impeding access to the AOI04-03

location, sampling at AOI04-03 was not included during SI activities. The original location

for AOI02-02 was determined to be too densely underlain with utilities for intrusive activities.

A revised location for AOI02-02 within close proximity to the original location was selected

after consultation with GAARNG. These actions were documented in a field change request

form dated 7 July 2021 and are provided in Appendix B3.

• During SI field activity in July 2021, an existing monitoring well (D6-29) was gauged for

synoptic water level measurement and sampled for a subset of 18 compounds that was not

included in the original SI QAPP Addendum scope of work (AECOM, 2021a) to provide an

assessment of potential migration from the AOI 4 source area in the downgradient direction

towards the eastern property boundary. The well is located downgradient of the potential

source area at AOI 4. During this mobilization, it was unknown whether Dobbins ARB would

grant permission to advance borings and temporary wells at AOI 4, so monitoring well D6-

29 was used to provide an assessment of the area. This action was documented in a field

change request form dated 16 July 2021 and is provided in Appendix B3.

• During DPT drilling activities at AOI 1, surface soil was collected from location AOI01-02;

however, the sample was only analyzed for TOC and pH due to chain of custody

discrepancy. No PFOA, PFOS, PFBS, PFHxS, or PFNA analysis was performed on surface

soil at AOI01-02, although the SI QAPP Addendum prescribed that analysis at that boring

location. Subsurface soil samples and groundwater collected and analyzed for a subset of

18 compounds from location AOI01-02 were used to provide an assessment of location

AOI01-02. Additionally, all AOI01-02 soil and groundwater samples, as well as soil and

groundwater samples collected from other AOI 1 locations (AOI01-01 and AOI01-03), were

used to provide an assessment of the entire AOI 1. These actions were documented in a

nonconformance and corrective action report dated 29 March 2022 and are provided in

Appendix B4.

• During DPT drilling activities, refusal was encountered prior to encountering groundwater at

boring locations AOI04-01 and AOI04-04. Rock outcroppings observed near the two

locations suggested site conditions may not allow for DPT or hollow stem auger drilling to

reach groundwater in that area. As a result, only soil samples were collected from the two

locations. At soil boring location AOI04-01, one surface soil sample was collected, and at
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General Lucius D. Clay National Guard Center, Georgia

AECOM 5-8

location AOI04-04, one surface soil and one shallow subsurface soil sample were collected. 

These actions were documented in a field change request form dated 1 October 2021 and 

are provided in Appendix B3. 

• During DPT drilling activities at AOI 4, subsurface soil samples were collected from the midpoints of borings at location AOI04-02 and AOI04-05; however, the mid-point samples were

collected below 15 feet bgs based on the total boring depths. The approved SI QAPP

Addendum states that mid-point subsurface soil samples would be collected from 13 to 15

feet bgs if total boring depth exceeded 30 feet bgs. The total boring depths at both locations

exceeded 30 feet bgs, and the mid-point samples were inadvertently collected at depths

greater than 15 feet bgs. These actions were documented in a nonconformance and

corrective action report dated 29 March 2022 and are provided in Appendix B4.

• During well abandonment on 1 October 2021, the temporary well at location AOI04-02 was

abandoned using clean sand and a 5-foot bentonite seal at the ground surface. The

temporary well was not abandoned in accordance with the SI QAPP Addendum (AECOM,

2021a). On 20 October 2021, the sand used to temporary abandon the well was over-drilled

and removed. The over-drilled boring was abandoned using bentonite in accordance with

the SI QAPP Addendum (AECOM, 2021a). These actions were documented in a

nonconformance and corrective action report dated 21 October 2021 and are provided in

Appendix B4.
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, General Lucius D. Clay National Guard Center, Georgia

Sample Identification

Sample

Collection 

Date/Time

Sample Depth 

(feet bgs)

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

Comments

AOI01-01-SB-0-2 7/14/2021 7:45 0 - 2 x

AOI01-01-SB-0-2-D 7/14/2021 7:45 0 - 2 x FD

AOI01-01-SB-6-8 7/14/2021 8:05 6 - 8 x

AOI01-01-SB-14-16 7/14/2021 8:15 14 - 16 x

AOI01-01-SB-14-16-D 7/14/2021 8:15 14 - 16 x FD

AOI01-02-SB-0-2 7/13/2021 13:00 0 - 2 x x

AOI01-02-SB-0-2-D 7/13/2021 13:00 0 - 2 x FD

AOI01-02-SB-0-2-MS 7/13/2021 13:00 0 - 2 x MS

AOI01-02-SB-0-2-MSD 7/13/2021 13:00 0 - 2 x MSD

AOI01-02-SB-11-13 7/13/2021 13:30 11 - 13 x

AOI01-02-SB-23-25 7/13/2021 13:40 23 - 25 x

AOI01-03-SB-0-2 7/12/2021 15:30 0 - 2 x

AOI01-03-SB-0-2-MS 7/12/2021 15:30 0 - 2 x MS

AOI01-03-SB-0-2-MSD 7/12/2021 15:30 0 - 2 x MSD

AOI01-03-SB-12-14 7/13/2021 9:15 12 - 14 x

AOI01-03-SB-25-27 7/13/2021 9:30 25 - 27 x

AOI02-01-SB-0-2 7/14/2021 9:45 0 - 2 x

AOI02-01-SB-10-12 7/14/2021 10:15 10 - 12 x

AOI02-01-SB-10-12-D 7/14/2021 10:15 10 - 12 x FD

AOI02-01-SB-20-22 7/14/2021 10:25 20 - 22 x x x

GS-AOI02-01 7/14/2021 10:35 20 - 22 x Received broken

AOI02-02-SB-0-2 7/14/2021 11:25 0 - 2 x

AOI02-02-SB-12-14 7/14/2021 11:50 12 - 14 x

AOI02-02-SB-20-22 7/14/2021 12:00 20 - 22 x

AOI03-01-SB-0-2 7/13/2021 14:25 0 - 2 x x x

AOI03-01-SB-10-12 7/13/2021 14:50 10 - 12 x

AOI03-01-SB-19-21 7/13/2021 15:00 19 - 21 x

AOI04-01-SB-0-2 10/1/2021 8:30 0 - 2 x

AOI04-02-SB-0-2 9/29/2021 13:35 0 - 2 x

AOI04-02-SB-18-20 9/29/2021 14:10 18 - 20 x

AOI04-02-SB-37-39 9/29/2021 14:20 37 - 39 x x x

AOI04-04-SB-0-2 9/29/2021 12:50 0 - 2 x

AOI04-04-SB-8-10 9/29/2021 13:10 8 - 10 x

AOI04-05-SB-0-2 9/30/2021 13:55 0 - 2 x

AOI04-05-SB-0-2-FD 9/30/2021 13:55 0 - 2 x FD

AOI04-05-SB-20-22 9/30/2021 14:30 20 - 22 x

AOI04-05-SB-38-40 9/30/2021 14:40 38 - 40 x

CNGC-01-SB-0-2 7/13/2021 11:00 0 - 2 x x x

CNGC-01-SB-0-2-MS 7/13/2021 11:00 0 - 2 x MS

CNGC-01-SB-0-2-MSD 7/13/2021 11:00 0 - 2 x MSD

CNGC-01-SB-12-14 7/13/2021 11:30 12 - 14 x

CNGC-01-SB-23-25 7/13/2021 11:45 23 - 25 x

Soil Samples

AECOM 5-9
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, General Lucius D. Clay National Guard Center, Georgia

Sample Identification

Sample

Collection 

Date/Time

Sample Depth 

(feet bgs)

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

Comments

AOI01-01-GW 7/14/2021 12:18 NA x

AOI01-01-GW-D 7/14/2021 12:18 NA x FD

AOI01-02-GW 7/14/2021 9:30 NA x

AOI01-03-GW 7/13/2021 13:32 NA x

AOI02-01-GW 7/14/2021 14:04 NA x

AOI02-01-GW-MS 7/14/2021 14:04 NA x MS

AOI02-01-GW-MSD 7/14/2021 14:04 NA x MSD

AOI02-02-GW 7/14/2021 15:30 NA x

AOI03-01-GW 7/14/2021 11:09 NA x

AOI04-02-GW 9/30/2021 15:35 NA x

AOI04-02-GW-FD 9/30/2021 15:35 NA x FD

AOI04-05-GW 10/1/2021 9:50 NA x

D6-29-GW 7/15/2021 14:40 NA x

CNGC-01-GW 7/13/2021 15:17 NA x

CNGC-MW030-GW 7/15/2021 10:31 NA x

CNGC-DECON-01 5/27/2021 9:10 NA x Collected from spigot

CNGC-DECON-02 5/27/2021 10:30 NA x Collected from spigot via hose

CNGC-ERB-01 7/14/2021 9:50 NA x Collected from hand auger

CNGC-ERB-02 7/14/2021 12:25 NA x Collected from drill rig rod

CNGC-ERB-02* 9/29/2021 14:50 NA x Collected from hand auger

CNGC-FRB-01 9/29/2021 15:15 NA x

Notes:

ASTM = American Society for Testing and Materials

bgs = below ground surface

ERB = equipment rinsate blank

FD = field duplicate

FRB = field reagent blank

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

QSM = Quality Systems Manual

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

* = Field team mistakenly gave the same name to two ERB samples collected during separate mobilizations

Quality Control Samples

Groundwater Samples

AECOM 5-10
Table 5-2

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

Site Inspection Report, General Lucius D. Clay National Guard Center, Georgia

Area of 

Interest

Boring 

Location

Soil Boring 

Depth 

(feet bgs)

Temporary Well 

Screen Interval 

(feet bgs)

Top of Casing 

Elevation 

(feet NAVD88)

Ground Surface 

Elevation 

(feet NAVD88)

Depth to 

Water

(feet btoc)

Depth to 

Water

(feet bgs)

Groundwater 

Elevation

(feet NAVD88)

AOI01-01 19 14 - 19 1060.758 1059.208 16.91 15.36 1043.85

AOI01-02 25 18 - 23 1060.090 1058.390 24.12 22.42 1035.97

AOI01-03 35 27 - 32 1054.989 1052.009 22.05 19.07 1032.94

AOI02-01 30 22 - 27 1045.523 1042.693 16.51 13.68 1029.01

AOI02-02 30 18 - 23 1034.368 1032.348 18.98 16.96 1015.39

AOI03-01 21 16 - 21 1059.919 1055.019 19.47 14.57 1040.45

CNGCMW030* NA NA 1095.986 1096.437 32.73 33.18 1063.26

CNGC-01 35 21 - 26 1051.705 1047.665 14.56 10.52 1037.14

AOI04-01 2 NA NA 1058.050 NA NA NA

AOI04-02 39 29 - 39 1055.580 1055.220 30.31 29.95 1025.27

AOI04-04 10.5 NA NA 1048.660 NA NA NA

AOI04-05 45 35 - 45 1042.750 1039.910 28.83 25.99 1013.92

D6-29* NA NA 1042.612 1042.873 23.81 24.07 1018.80

Notes:

bgs = below ground surface

btoc = below top of casing

NA = not applicable

NAVD88 = North American Vertical Datum 1988

* = existing permanent monitoring well

1

2

4

3

AECOM 5-11
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 5-12

THIS PAGE INTENTIONALLY BLANK
?!

?!

?!

?!

?!

?!

?!

A!

Retention Basin

Retention Basin

Drainage Ditch

AOI 2

AOI 3

AOI 1

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI01-03

CNGC-MW030

0 245 490 980

Feet

Legend

?! Soil Boring

A! Existing Monitoring Well

Area of Interest

Facility Boundary

Water Body

Surface Water Flow Direction

Groundwater Flow Direction

Site Inspection 

Sample Locations - South Property

Figure 5-1

CLIENT

REVISED

SCALE

8/3/2022 MS

JW

8/3/2022

8/3/2022

ARNG

GIS BY

CHK BY

PROJECT Site Inspection at Clay National Guard Center, GA

PM CM 8/3/2022

1:5,880 ­ 12420 Milestone Center Drive

Germantown, MD 20876

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

AECOM 5-13
?!

?!

?!

A! ?!

AOI 4

AOI04-01

AOI04-02

AOI04-04

AOI04-05

WELL-D6-29

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

JW

10/10/2022

10/10/2022

Site Inspection at Clay National Guard Center, GA

10/10/2022

1:4,200 ­ Figure 5-2 PM CM 10/10/2022

12420 Milestone Center Drive

Germantown, MD 20876

Sample Locations - 

North Property

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

and the GIS User Community

0 175 350 700

Feet

Legend

?! Soil Boring

A! Existing Monitoring Well

Area of Interest

Fomer ARNG AASF Boundary

Surface Water Flow Direction

Groundwater Flow Direction

PROJECT

AECOM 5-14
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-1

6. Site Inspection Results

This section presents the analytical results of the SI. The SLs used in this evaluation are 

presented in Section 6.1. A discussion of the results for each AOI is provided in Section 6.3

through Section 6.6. Table 6-2 through Table 6-5 present results in soil or groundwater for the 

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

laboratory reports are provided in Appendix G. 

6.1 Screening Levels 

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

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

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

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

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

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

presented in 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

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

feet is the anticipated limit of construction activities. 

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

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

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

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

of HFPO-DA is not anticipated at the facility because HFPO-DA is generally not a component of MIL-SPEC AFFF and based on its 

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

addition, it is unlikely that GenX would be an individual chemical of concern in the absence of other PFAS. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

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; grain size analysis was not performed because the sample collected 

for that analysis, sample GS-AOI02-01, was broken during shipment. 

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: the Hangar 1/Ramp Area. The soil and groundwater results are summarized on Table 6-2

through Table 6-5. Soil and groundwater results are presented on Figure 6-1 through Figure 6-

7. 

6.3.1 AOI 1 Soil Analytical Results

Table 6-2 through Table 6-4 summarize the soil results. Figure 6-1 through Figure 6-5 present 

the ranges of detections in soil.

Soil was sampled from three intervals at boring locations AOI01-01, AOI01-02 and AOI01-03; 

however, surface soil at boring location AOI01-02 was not analyzed for PFOA, PFOS, PFBS, 

PFHxS, or PFNA as described in Section 5.9. Samples were collected from 2-foot intervals in 

surface soil (0 to 2 feet bgs), shallow subsurface soil (6 to 14 feet bgs), and deep subsurface soil 

intervals (14 to 27 feet bgs). PFOA, PFOS, and PFHxS were detected at concentrations below 

the respective SLs in surface soil; PFBS and PFNA were not detected in surface soil. PFOA was 

detected in surface soil at location AOI01-03, with a concentration of 0.155 J (estimated) 

micrograms per kilogram (μg/kg). PFOS was detected at locations AOI01-01 and AOI01-03, with 

concentrations of 1.02 J μg/kg (Duplicate) and 0.683 J μg/kg, respectively. PFHxS was detected 

at locations AOI01-01 and AOI01-03, with concentrations of 0.261 J μg/kg and 0.127 J μg/kg, 

respectively. PFBS and PFNA were not detected in surface soil at AOI 1. 

In shallow subsurface soil, PFHxS was detected at concentrations below the SL at two of the 

three locations, with concentrations of 0.048 J μg/kg at AOI01-02 and 0.682 J μg/kg at AOI01-03.

PFOA, PFOS, PFBS, and PFNA were not detected in shallow subsurface soil at AOI 1. 

In deep subsurface soil, PFOA, PFOS, PFBS, and PFHxS were detected at AOI 1; PFNA was not 

detected. PFOA was detected at location AOI01-01, with a concentration of 0.116 J μg/kg 

(Duplicate). PFOS was detected at location AOI01-02, with a concentration of 0.128 J μg/kg. 

PFBS was detected at location AOI01-03, with a concentration of 0.044 J μg/kg. PFHxS was 

detected at all three locations, with concentrations ranging from 0.075 J μg/kg (AOI01-02) to 0.587 

J μg/kg (AOI01-03). 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-3

6.3.2 AOI 1 Groundwater Analytical Results

Table 6-5 summarizes the groundwater results. Figure 6-6 and Figure 6-7 present the ranges of 

detections in groundwater.

Groundwater was sampled from temporary monitoring wells AOI01-01, AOI01-02, and AOI01-03. 

PFOA was detected above the SL of 6 nanograms per liter (ng/L) at all three well locations, with 

concentrations ranging from 13.1 ng/L at AOI01-02 to 99.2 ng/L at AOI01-01. PFHxS was detected 

above the SL of 39 ng/L at all three well locations, with concentrations ranging from 57.1 ng/L at 

AOI01-02 to 317 ng/L at AOI01-03. PFBS was detected below the SL of 601 ng/L at all three 

locations, with concentrations ranging from 6.72 ng/L at AOI01-02 to 23.3 ng/L at AOI01-03. PFOS 

and PFNA were not detected at any of the AOI 1 temporary well locations. 

6.3.3 AOI 1 Conclusions

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

respective SLs, while PFNA was not detected at all. PFOA and PFHxS were detected in 

groundwater at concentrations above their respective SLs, and PFBS was detected below its SL. 

PFOS and PFNA were not detected in groundwater at AOI 1. Based on the exceedances of the 

SLs in groundwater, further evaluation at AOI 1 is warranted. 

6.4 AOI 2 

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

AOI 2: Hangar 300. The results in soil and groundwater are summarized on Table 6-2 through 

Table 6-5. Soil and groundwater results are presented on Figure 6-1 through Figure 6-7. 

6.4.1 AOI 2 Soil Analytical Results

Table 6-2 through Table 6-4 summarize the soil results. Figure 6-1 through Figure 6-5 present 

the ranges of detections in soil. 

Soil was sampled from three intervals at boring locations AOI02-01 and AOI02-02. Samples were 

collected from 2-foot intervals in surface soil (0 to 2 feet bgs), shallow subsurface soil (10 to 14 

feet bgs), and deep subsurface soil (20 to 22 feet bgs). PFOS was detected at concentrations 

above the SL of 13 μg/kg in surface soil; PFOA, PFBS, PFHxS, and PFNA were detected in 

surface soil at concentrations below their respective SLs. PFOA was detected at locations AOI02-

01 and AOI02-02, with concentrations of 0.926 J μg/kg and 0.243 J μg/kg, respectively. PFOS 

exceeded the SL of 13 μg/kg in surface soil at locations AOI02-01 and AOI02-02, with 

concentrations of 19.9 μg/kg and 43.9 J μg/kg, respectively. PFBS was detected at locations 

AOI02-01 and AOI02-02, with concentrations of 9.63 μg/kg and 0.028 J μg/kg, respectively. 

PFHxS was detected at locations AOI02-01 and AOI02-02, with concentrations of 39.3 μg/kg and 

1.39 μg/kg, respectively. PFNA was detected at locations AOI02-01 and AOI02-02, with 

concentrations of 0.047 J μg/kg and 0.055 J μg/kg, respectively.

In shallow subsurface soil, PFOS was detected above the SL of 160 μg/kg, with a concentration 

of 609 μg/kg at AOI02-02. PFOS was also detected at a concentration of 0.179 J μg/kg (Duplicate) 

at AOI02-01. PFBS and PFHxS were detected in shallow subsurface soil at concentrations below 

their respective SLs. PFBS was detected in shallow subsurface soil at location AOI02-01, with a 

concentration of 0.094 J μg/kg. PFHxS was detected in shallow subsurface soil at locations 

AOI02-01 and AOI02-02, with concentrations of 0.091 J μg/kg (Duplicate) and 1.64 J μg/kg, 

respectively. PFOA and PFNA were not detected in shallow subsurface at AOI 2. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-4

In deep subsurface soil, PFOA, PFOS, PFBS, and PFHxS were detected at AOI 2; PFNA was not 

detected. PFOA was detected at location AOI02-01, with a concentration of 0.467 J μg/kg. PFOS 

was detected at locations AOI02-01 and AOI02-02, with concentrations of 27.3 μg/kg and 22.6

μg/kg, respectively. PFBS was detected at locations AOI02-01 and AOI02-02, with concentrations 

of 1.10 J μg/kg and 0.086 J μg/kg, respectively. PFHxS was detected at locations AOI02-01 and 

AOI02-02, with concentrations of 7.70 μg/kg and 0.840 J μg/kg, respectively. 

6.4.2 AOI 2 Groundwater Analytical Results

Table 6-5 summarizes the groundwater results. Figure 6-6 and Figure 6-7 present the ranges of 

detections in groundwater.

Groundwater was sampled from temporary monitoring well locations AOI02-01 and AOI02-02 at 

AOI 2. PFOA was detected above the SL of 6 ng/L at AOI02-01 and AOI02-02, with concentrations 

of 3,650 ng/L and 58.6 J ng/L, respectively. PFOS was detected above the SL of 4 ng/L at AOI02-

01 and AOI02-02, with concentrations of 320,000 J ng/L and 39,200 ng/L, respectively. PFBS was 

detected above the SL of 601 ng/L at AOI02-01, with a concentration of 9,430 J- (estimated 

concentration biased low) ng/L. PFBS was detected below the SL of 601 ng/L at AOI02-02, with 

a concentration of 149 J ng/L. PFHxS was detected above the SL of 39 ng/L at AOI02-01 and 

AOI02-02, with concentrations of 63,100 ng/L and 2,030 ng/L, respectively. PFNA was not 

detected in groundwater at AOI 2. 

6.4.3 AOI 2 Conclusions

Based on the results of the SI, PFOS was detected at concentrations above its SL in soil, and 

PFOA, PFBS, PFHxS, and PFNA were detected in soil at concentrations below their respective 

SLs. PFOA, PFOS, PFBS, and PFHxS were detected at concentrations above their respective 

SLs in groundwater, and PFNA was not detected in groundwater. Based on the exceedances of 

the SLs in soil and groundwater, further evaluation at AOI 2 is warranted. 

6.5 AOI 3 

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

AOI 3: Hangar 312. The results in soil and groundwater are presented in Table 6-2 through Table 

6-5. Soil and groundwater results are presented on Figure 6-1 through Figure 6-7. 

6.5.1 AOI 3 Soil Analytical Results

Table 6-2 through Table 6-4 summarize the soil results. Figure 6-1 through Figure 6-5 present 

the ranges of detections in soil.

Soil was sampled from three intervals at boring location AOI03-01. Samples were collected from 

2-foot intervals in surface soil (0 to 2 feet bgs), shallow subsurface soil (10 to 12 feet bgs), and 

deep subsurface soil (19 to 21 feet bgs). PFOS was detected above the SL of 13 μg/kg in surface 

soil at AOI03-01 with a concentration of 14.4 μg/kg. PFOA, PFBS, PFHxS, and PFNA were 

detected in soil at concentrations below their respective SLs. PFOA was detected in surface soil, 

with a concentration of 0.851 J μg/kg; PFBS was detected in surface soil, with a concentration of 

0.042 J μg/kg; PFHxS was detected in surface soil, with a concentration of 0.661 J μg/kg; and 

PFNA was detected in surface soil, with a concentration of 2.94 μg/kg. 

In shallow subsurface soil, PFOA, PFOS, and PFHxS were detected below their respective SLs

at AOI03-01; PFBS and PFNA were not detected. PFOA was detected with a concentration of 

2.11 μg/kg, PFOS was detected with a concentration of 0.164 J μg/kg, and PFHxS was detected 

with a concentration of 1.03 J μg/kg. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-5

In deep subsurface soil, PFOA, PFOS, and PFHxS were also detected at location AOI03-01; 

PFBS and PFNA were not detected in deep subsurface soil. PFOA was detected with a 

concentration of 0.748 J μg/kg, PFOS was detected with a concentration of 0.197 J μg/kg, and 

PFHxS was detected with a concentration of 0.164 μg/kg. 

Soil was also sampled from three intervals at boring location CNGC-01 to assess the area 

potentially upgradient of AOI 3. Samples were collected from surface soil (0 to 2 feet bgs), shallow 

subsurface soil (12 to 14 feet bgs), and deep subsurface soil (23 to 25 feet bgs). PFOS and 

PFHxS were detected in surface soil, at concentrations below their respective SLs, with 

concentrations of 0.716 J μg/kg and 0.461 J μg/kg, respectively. PFOA, PFBS, and PFNA were 

not detected in surface soil. 

In shallow subsurface soil, PFHxS was detected below the SL of 1,600 μg/kg at CNGC-01, with 

a concentration of 0.210 J μg/kg. PFOA, PFOS, PFBS, and PFNA were not detected in shallow 

subsurface soil. PFHxS was also detected in deep subsurface soil at CNGC-01, with a 

concentration of 0.059 J μg/kg. PFOA, PFOS, PFBS, and PFNA were not detected in deep 

subsurface soil. 

6.5.2 AOI 3 Groundwater Analytical Results 

Table 6-5 summarizes the groundwater results. Figure 6-6 and Figure 6-7 present the ranges of 

detections in groundwater.

Groundwater was sampled from temporary monitoring well location AOI03-01 at AOI 3. PFOA

was detected above the SL of 6 ng/L, with a concentration of 1,590 ng/L. PFOS was detected 

above the SL of 4 ng/L, with a concentration of 468 ng/L. PFHxS was detected above the SL of 

39 ng/L, with a concentration of 329 ng/L. PFNA was detected above the SL of 6 ng/L, with a 

concentration of 16.5 ng/L. PFBS was detected below the SL of 601 ng/L, with a concentration of 

22.7 ng/L. 

Groundwater was also sampled from temporary monitoring well location CNGC-01 and existing 

monitoring well location CNGC-MW030 to assess the area potentially upgradient of AOI 3. Due 

to the convergence of groundwater flow on the retention basin located west of Hangar 312; 

however, it is uncertain whether locations CNGC-01 and CNGC-MW030 are upgradient of AOI 3. 

PFOA, PFOS, and PFHxS were detected above their respective SLs at both potentially upgradient 

locations. PFOA was detected at both locations above the SL of 6 ng/L, with concentrations 

ranging from 10.2 ng/L (CNGC-01) to 27.9 ng/L (CNGC-MW030). PFOS was detected at both 

locations above the SL of 4 ng/L, with concentrations ranging from 21.4 (CNGC-MW030) to 56.3 

ng/L (CNGC-01). PFHxS was detected at both locations above the SL of 39 ng/L, with 

concentrations ranging from 172 ng/L (CNGC-01) to 433 ng/L (CNGC-MW030). PFBS was 

detected below the SL of 601 ng/L at both locations, with concentrations of ranging from 25.1 ng/L 

(CNGC-01) to 179 ng/L (CNGC-MW030). PFNA was not detected in groundwater at either 

location potentially upgradient of AOI 3. 

6.5.3 AOI 3 Conclusions

Based on the results of the SI, PFOS was detected in soil above the SL. PFOA, PFBS, PFHxS, 

and PFNA were also detected in soil below their respective SLs. PFOA, PFOS, PFHxS, and PFNA 

were detected in groundwater at concentrations above their respective SLs, and PFBS was 

detected in groundwater below its SL. Based on the exceedances of the SLs in soil and 

groundwater, further evaluation at AOI 3 is warranted.
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-6

6.6 AOI 4 

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

4: Building 555. The results in soil and groundwater are presented in Table 6-2 through Table 6-

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

6.6.1 AOI 4 Soil Analytical Results

Table 6-2 through Table 6-4 summarize the soil results. Figure 6-1 through Figure 6-5 present 

the ranges of detections in soil.

Soil was sampled from three intervals at boring locations at AOI 4. Samples were collected from 

2-foot intervals in surface soil (0 to 2 feet bgs), shallow subsurface soil (8 to 10 feet bgs), and 

deep subsurface soil (18 to 40 feet bgs). PFOA, PFOS, PFHxS, and PFNA were detected in 

surface soil at concentrations below their respective SLs; PFBS was not detected in surface soil 

at AOI 4. PFOA was detected in surface soil at location AOI04-04, with a concentration of 0.232

J μg/kg. PFOS was detected in surface soil at locations AOI04-01, AOI04-02, and AOI04-04, with 

concentrations ranging from 0.116 J μg/kg to 0.401 J μg/kg. PFHxS was detected in surface soil 

at locations AOI04-02 and AOI04-04, with concentrations of 0.163 J μg/kg and 0.096 J, 

respectively. PFNA was detected in surface soil at location AOI04-01, with a concentration of 

0.025 J μg/kg. 

In shallow subsurface soil, PFOS and PFHxS were detected below their respective SLs. PFOA, 

PFBS, and PFNA were not detected in shallow subsurface soil at AOI 4. PFOS was detected in 

shallow subsurface soil at location AOI04-04, with a concentration of 0.882 J μg/kg. PFHxS was 

detected in shallow subsurface soil at location AOI04-04, with a concentration of 0.068 J μg/kg. 

In deep subsurface soil, PFOA and PFOS were detected at location AOI04-02, with 

concentrations of 0.108 J μg/kg, and 0.133 J μg/kg, respectively. PFOA and PFOS were not 

detected at any other deep subsurface soil sample locations. PFBS and PFNA were not detected 

in deep subsurface soil at AOI 4. PFHxS was detected in deep subsurface soil at location AOI04-

02, with a concentration of 0.289 J μg/kg. 

6.6.2 AOI 4 Groundwater Analytical Results

Table 6-5 summarizes the groundwater results. Figure 6-6 and Figure 6-7 present the ranges of 

detections in groundwater.

During the first mobilization in July 2021, drilling was not permitted at AOI 4. Groundwater was 

collected from existing permanent monitoring well D6-29. PFOA was detected above the SL of 6 

ng/L, with a concentration of 23.8 ng/L, and PFOS was detected above the SL of 4 ng/L, with a 

concentration of 22.7 ng/L. PFBS was detected below the SL of 601 ng/L, with a concentration of 

7.45 ng/L. PFHxS was also detected below the SL of 39 ng/L, with a concentration of 38.4 ng/L. 

PFNA was not detected. Sampling of monitoring well D6-29 was included to assess the area 

downgradient of AOI 4 in lieu of drilling temporary wells until Dobbins ARB approved drilling 

operations. This action was documented in a field change request provided in Appendix B. 

Upon receiving approval to drill at AOI 4 from Dobbins ARB, a second mobilization commenced 

in September 2021, and two temporary wells were installed, AOI04-02 and AOI04-05. Temporary 

well AOI04-03 was removed from the SI sampling program due to construction area access 

issues, and temporary wells at AOI04-01 and AOI04-04 were not installed due to encountering 

refusal prior to reaching groundwater at those locations. These actions are documented in a field 

change request provided in Appendix B. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-7

PFOA was detected above the SL of 6 ng/L at AOI04-02 and AOI04-05, with concentrations of

41.6 ng/L (Duplicate) and 64.1 ng/L, respectively. PFOS was detected above the SL of 4 ng/L at 

AOI04-02 and AOI04-05, with concentrations of 138 ng/L and 20.3 ng/L, respectively. PFBS was 

detected below the SL of 601 ng/L at locations AOI04-02 and AOI04-05, with concentrations of 11 

ng/L and 33.5 ng/L, respectively. PFHxS was detected above the SL of 39 ng/L at AOI04-02 and 

AOI04-05, with concentrations of 53.7 ng/L and 121 ng/L, respectively. PFNA was not detected in 

groundwater at AOI 4.

6.6.3 AOI 4 Conclusions

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

respective SLs, and PFBS was not detected. PFOA, PFOS, and PFHxS were detected in 

groundwater at concentrations above their respective SLs, and PFBS was detected in 

groundwater below its SL. PFNA was not detected in groundwater. Based on the exceedances of 

the SLs in groundwater, further evaluation at AOI 4 is warranted 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 6-8

THIS PAGE INTENTIONALLY BLANK
Table 6-2

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

Site Inspection Report, Clay National Guard Center

Analyte OSD Screening 

Level a

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

PFBS 1900 ND U ND U ND U 9.63 0.028 J 0.042 J ND U ND U ND U ND U ND U

PFHxS 130 0.261 J 0.251 J 0.127 J 39.3 1.39 0.661 J 0.461 J ND U 0.163 J 0.096 J ND U

PFNA 19 ND U ND U ND U 0.047 J 0.055 J 2.94 ND U 0.025 J ND U ND U ND U

PFOA 19 ND U ND U 0.155 J 0.926 J 0.243 J 0.851 J ND U ND U ND U 0.232 J ND U

PFOS 13 0.605 J 1.02 J 0.683 J 19.9 43.9 J 14.4 0.716 J 0.212 J 0.116 J 0.401 J ND U

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Acronyms and Abbreviations

AOI Area of Interest

CNGC Clay National Guard Center

D/FD 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

AOI03

CNGC-01-SB-0-2

07/13/2021

0-2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-0-2

07/14/2021

0-2 ft

AOI01-01-SB-0-2-D

07/14/2021

0-2 ft

AOI01-03-SB-0-2

07/12/2021

0-2 ft

AOI02-01-SB-0-2

07/14/2021

0-2 ft

AOI02-02-0-2

07/14/2021

0-2 ft

07/13/2021

0-2 ft

AOI04-01-SB-0-2

10/01/2021

0-2 ft

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

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

contaminated soil.

Interpreted Qualifiers

J = Estimated concentration

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

AOI01 AOI02 AOI04

AOI04-05-SB-0-2

09/30/2021

0-2 ft

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

AOI04-02-SB-0-2

09/29/2021

0-2 ft

AOI04-04-SB-0-2

09/29/2021

0-2 ft

AOI03-01-SB-0-2

AECOM 6-9
Table 6-2

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

Site Inspection Report, Clay National Guard Center

Analyte OSD Screening 

Level a

Result Qual Result Qual

PFBS 1900 ND U ND U

PFHxS 130 ND U ND U

PFNA 19 ND U ND U

PFOA 19 ND U ND U

PFOS 13 ND U ND U

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL CNGC Clay National Guard Center

D/FD 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

AOI04-05-SB-0-2

09/30/2021

0-2 ft

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

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

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

contaminated soil.

Area of Interest

Sample ID

Sample Date

Depth

AOI04-05-SB-0-2-FD

09/30/2021

0-2 ft

AOI04

AECOM 6-10
Table 6-3

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

Site Inspection Report, Clay National Guard Center

Analyte OSD Screening 

Level a

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

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

PFBS 25000 ND U ND U ND U 0.094 J 0.082 J ND U ND U ND U ND U

PFHxS 1600 ND U 0.048 J 0.682 J 0.090 J 0.091 J 1.64 J 1.03 J 0.210 J 0.068 J

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

PFOA 250 ND U ND U ND U ND U ND U ND U 2.11 ND U ND U

PFOS 160 ND U ND U ND U ND UJ 0.179 J 609 0.164 J ND U 0.882 J

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AOI Area of Interest

U = The analyte was not detected at a level greater than or equal to the adjusted DL CNGC Clay National Guard Center

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

12-14 ft

AOI03

10-12 ft 8-10 ft

AOI01 AOI04

07/13/2021 09/29/2021

AOI03-01-SB-10-12 AOI04-04-SB-8-10

12-14 ft

CNGC-01-SB-12-14

07/13/2021

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-6-8

07/14/2021

6-8 ft

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

USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022. Soil screening levels based on industrial/commercial composite worker scenario for incidental

ingestion of contaminated soil.

AOI02

AOI02-02-SB-12-14

07/14/2021

12-14 ft

AOI02-01-SB-10-12

07/14/2021

10-12 ft

AOI02-01-SB-10-12-D

07/14/2021

10-12 ft

AOI01-02-SB-11-13

07/13/2021

11-13 ft

AOI01-03-SB-12-14

07/13/2021

AECOM 6-11
Table 6-4

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

Site Inspection Report, Clay National Guard Center

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual

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

PFBS ND U ND U ND U 0.044 J 1.10 J 0.086 J ND U ND U ND U ND U

PFHxS 0.204 J 0.183 J 0.075 J 0.587 J 7.70 0.840 J 0.164 J 0.059 J ND U 0.289 J

PFNA ND U ND U ND U ND U ND U ND U ND U ND U ND U ND U

PFOA ND UJ 0.116 J ND U ND U 0.467 J ND U 0.748 J ND U ND U 0.108 J

PFOS ND U ND U 0.128 J ND U 27.3 22.6 0.197 J ND U ND U 0.133 J

Interpreted Qualifiers Chemical Abbreviations

J = Estimated concentration PFBS perfluorobutanesulfonic acid

U = The analyte was not detected at a level greater than or equal to the adjusted DL PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Acronyms and Abbreviations

AOI Area of Interest

CNGC Clay National Guard Center

DL detection limit

ft feet

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

μg/kg micrograms per kilogram

07/13/2021

23-25 ft

AOI01 AOI03

AOI01-01-SB-14-16 AOI01-01-SB-14-16-D

07/14/2021 07/14/2021

14-16 ft 14-16 ft 20-22 ft

AOI02-02-SB-20-22

07/14/2021

20-22 ft

AOI01-02-SB-23-25

07/13/2021

23-25 ft

AOI01-03-SB-25-27

07/13/2021

25-27 ft

AOI04-02-SB-37-39

09/29/2021

37-39 ft

AOI02 AOI04

AOI03-01-SB-19-21

07/13/2021

19-21 ft

AOI04-02-SB-18-20

09/29/2021

18-20 ft

AOI02-01-SB-20-22

07/14/2021

CNGC-01-SB-23-25

AECOM 6-12
Table 6-4

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

Site Inspection Report, Clay National Guard Center

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual Result Qual

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

PFBS ND U ND U

PFHxS ND U ND U

PFNA ND U ND U

PFOA ND U ND U

PFOS ND U ND U

Interpreted Qualifiers Chemical Abbreviations

J = Estimated concentration PFBS perfluorobutanesulfonic acid

U = The analyte was not detected at a level greater than or equal to the adjusted DL PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

Acronyms and Abbreviations

AOI Area of Interest

CNGC Clay National Guard Center

DL detection limit

ft feet

ID identification

LCMSMS liquid chromatography with tandem mass spectrometry

LOD limit of detection

ND analyte not detected above the LOD

QSM Quality Systems Manual

Qual interpreted qualifier

SB soil boring

μg/kg micrograms per kilogram

AOI04

AOI04-05-SB-20-22

09/30/2021

20-22 ft

AOI04-05-SB-38-40

09/30/2021

38-40 ft

AECOM 6-13
Table 6-5

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

Site Inspection Report, Clay National Guard Center

Analyte OSD Screening 

Level a

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

PFBS 601 14.1 12.4 6.72 23.3 9430 J- 149 J 22.7 25.1 179

PFHxS 39 303 276 57.1 317 63100 2030 329 172 433

PFNA 6 ND U ND U ND U ND U ND U ND U 16.5 ND U ND U

PFOA 6 99.2 89.0 13.1 26.8 3650 58.6 J 1590 10.2 27.9

PFOS 4 ND U ND U ND U ND U 320000 J 39200 468 56.3 21.4

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 AOI Area of Interest

J- = Estimated concentration, biased low CNGC Clay National Guard Center

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

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

CNGC-01-GW CNGC-MW030-GW

07/13/2021 07/15/2021

AOI03

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

USEPA’s Regional Screening Level Calculator. HQ=0.1, May 2022 Groundwater screening levels based on residential scenario for direct ingestion of groundwater.

AOI01 AOI02

AOI02-02-GW

07/14/2021

AOI03-01-GW

07/14/2021

AOI01-03-GW

07/13/2021

AOI02-01-GW

07/14/2021

AOI01-01-GW-D

07/14/2021

AOI01-02-GW

07/14/2021

Area of Interest

Sample ID

Sample Date

AOI01-01-GW

07/14/2021

AECOM 6-14
Table 6-5

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

Site Inspection Report, Clay National Guard Center

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual

PFBS 601 11.0 11.0 33.5 7.45

PFHxS 39 53.7 52.6 121 38.4

PFNA 6 ND U ND U ND U ND U

PFOA 6 41.5 41.6 64.1 23.8

PFOS 4 138 136 20.3 22.7

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 AOI Area of Interest

J- = Estimated concentration, biased low CNGC Clay National Guard Center

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

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.

AOI04

AOI04-02-GW AOI04-02-GW-FD

09/30/2021 09/30/2021

D6-29-GW

07/15/2021

Area of Interest

Sample ID

Sample Date

AOI04-05-GW

10/01/2021

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

AECOM 6-15
AECOM 6-16

Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

THIS PAGE INTENTIONALLY BLANK
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-05

Big

Lake

AOI01-01

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Shallow Intermediate Deep

­ Figure 6-1

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

8/11/2022

8/11/2022

8/11/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

8/11/2022

1:7,214

PFOA Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

0 300 600 1,200

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.

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-17
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-05

Big

Lake

AOI01-01

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Shallow Intermediate Deep

­ Figure 6-2

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

8/11/2022

8/11/2022

8/11/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

8/11/2022

1:7,214

PFOS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

0 300 600 1,200

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 6-18
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-05

Big

Lake

AOI01-01

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Shallow Intermediate Deep

­ Figure 6-3

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

8/11/2022

8/11/2022

8/11/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

8/11/2022

1:7,214

PFBS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

0 300 600 1,200

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 6-19
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-05

Big

Lake

AOI01-01

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Shallow Intermediate Deep

­ Figure 6-4

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

8/11/2022

8/11/2022

8/11/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

8/11/2022

1:7,214

PFHxS Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

0 300 600 1,200

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 6-20
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

AOI04-05

Big

Lake

AOI01-01

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-01

AOI04-02

AOI01-03

AOI04-04

AOI04-05

Shallow Intermediate Deep

­ Figure 6-5

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

8/11/2022

8/11/2022

8/11/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

8/11/2022

1:7,214

PFNA Detections in Soil

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

0 300 600 1,200

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 6-21
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

CNGC-MW030

AOI04-05

WELL-D6-29

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

CNGC-MW030

AOI04-05

WELL-D6-29 Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

CNGC-MW030

AOI04-05

WELL-D6-29

PFOA PFOS PFBS

­ Figure 6-6

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

10/10/2022

10/10/2022

10/10/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

10/10/2022

1:9,017

PFOA, PFOS, and PFBS Detections in Groundwater

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

0 375 750 1,500

Feet

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

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

AECOM 6-22
Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

CNGC-MW030

AOI04-05

WELL-D6-29

Big

Lake

AOI01-01

AOI01-02

AOI02-01

AOI02-02

AOI03-01

CNGC-01

AOI04-02

AOI01-03

CNGC-MW030

AOI04-05

WELL-D6-29

PFHxS PFNA

­ Figure 6-7

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Clay National Guard Center, GA

8/26/2022

8/26/2022

8/26/2022

MS

JW

CM

GIS BY

CHK BY

PM

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

8/26/2022

1:9,000

PFHxS and PFNA Detections in Groundwater

12420 Milestone Center Drive

Germantown, MD 20876

Legend

Facility Boundary

Fomer ARNG AASF Boundary

PFHxS Results (ng/L)

ND

>ND - 39

>39 - 100

>100 - 1,000

>1,000

0 375 750 1,500

Feet

PFNA Results (ng/L)

ND

>ND - 6

>6 - 100

>100 - 1,000

>1,000

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

AECOM 6-23
AECOM 6-24

Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 7-1

7. Exposure Pathways

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

Figure 7-4. Please note that while the CSM discussion assists in determining if a receptor may 

be impacted, the decision to move from SI to RI or interim action is determined based upon 

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

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

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

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

potentially complete when the following conditions are present:

1. Contaminant source;

2. Environmental fate and transport;

3. Exposure point;

4. Exposure route; and

5. Potentially exposed populations.

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

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

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

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

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

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

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

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

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

recommendation for future study in 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, residents outside the facility boundary, and recreational users outside of the facility 

boundary. 

7.1 Soil Exposure Pathway 

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

between the source and potential receptors AOI 1 through AOI 4 based on the aforementioned 

criteria. 

7.1.1 AOI 1

Hangar 1 previously contained a fire suppression system that used 3% AFFF concentrate. The 

fire suppression system has been disabled, and the AFFF tanks were removed from the hangar 

during winter 2020 intact with their AFFF contents. The tanks were transported from Hangar 1 to 

a hazardous waste storage building on the southeastern corner of the ramp area. The wash rack 

near Hangar 1 currently drains to the industrial WWTP and then to the sanitary WWTP. There are 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 7-2

no known releases of AFFF at AOI 1, but undocumented releases are possible as a result of AFFF 

storage.

PFOA, PFOS, and PFHxS were detected below the SLs in surface soil at AOI 1; PFBS and PFNA 

were not detected. Therefore, ground-disturbing activities could potentially result in site worker 

and future construction worker exposure to constituents in soil via inhalation of dust or ingestion 

of surface soil. PFOS, PFBS, and PFHxS were also detected below the SLs in subsurface soil. 

Therefore, ground-disturbing activities could potentially result in future construction worker 

exposure to constituents in soil via ingestion of subsurface soil. No current construction activities 

are occurring at AOI 1. The CSM for AOI 1 is presented in Figure 7-1. 

7.1.2 AOI 2 

AFFF was released from the Hangar 300 fire suppression system twice in the early to mid-2000s, 

prior to GAARNG assuming occupancy of the building. During both releases, AFFF was released 

in the hangar, pushed onto the ramp to the west, then north and east around the hangar, and 

ultimately into the retention basin east of Hangar 300. The retention basin contains a storm drain 

that discharges into Poorhouse Creek.

PFOA, PFBS, PFHxS, and PFNA were detected below the SLs, and PFOS was detected above 

the SL in surface soil at AOI 2. Therefore, ground-disturbing activities could potentially result in 

site worker and future construction worker exposure to constituents in soil via inhalation of dust 

or ingestion of surface soil. PFOS was detected above the SL and PFOA, PFBS, and PFHxS 

were detected below the SLs, and in subsurface soil at AOI 2. Therefore, ground-disturbing 

activities could also potentially result in future construction worker exposure to constituents in soil

via ingestion of subsurface soil. No current construction activities are occurring at AOI 2. The CSM 

for AOI 2 is presented in Figure 7-2. 

7.1.3 AOI 3 

Hangar 312 contains a fire suppression system supplied 3% AFFF low expansion foam. The AFFF 

tank and pumps that supply the fire suppression system are housed in a room within the hangar 

that contains a floor drain that drains to the industrial WWTP and then the sanitary WWTP. During 

the PA site visit, evidence of corrosion down the side of the tank was observed, and the gasket 

between the tank and the outline piping appeared to have been replaced with an ill-fitting gasket 

that stuck out on the sides.

PFOA, PFBS, PFHxS, and PFNA were detected below the SLs, and PFOS was detected above 

the SL in surface soil at AOI 3. Therefore, ground-disturbing activities could potentially result in 

site worker and future construction worker exposure to constituents in soil via inhalation of dust 

or ingestion of surface soil. PFOA, PFOS, and PFHxS were detected below SLs in subsurface 

soil at AOI 3. Therefore, ground-disturbing activities could also potentially result in future 

construction worker exposure to constituents in soil via ingestion of subsurface soil. No current 

construction activities are occurring at AOI 3. 

In the area potentially upgradient of AOI 3, PFOS and PFHxS were detected below the SLs in 

surface soil, and PFHxS was detected below the SL. The CSM for AOI 3 is presented in Figure 

7-3. 

7.1.4 AOI 4 

There are no documented releases of AFFF at Building 555, the former AASF. The building did 

not have a fire suppression system; however, historical aerial photographs show evidence of 

portable fire extinguishers that could have contained AFFF on the ramp. If AFFF-containing fire 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 7-3

extinguishers were present on the ramp area at AOI 4, then undocumented releases could have 

occurred to the ground surface.

PFOA, PFOS, PFHxS, and PFNA were detected below the SLs in surface soil at AOI 4; PFBS 

was not detected. Therefore, ground-disturbing activities could potentially result in site worker and 

construction worker exposure to constituents in soil via inhalation of dust or ingestion of surface 

soil. PFOA, PFOS, and PFHxS were detected below the SLs in subsurface soil at AOI 4. 

Therefore, ground-disturbing activities could also potentially result in construction worker 

exposure to constituents in soil via ingestion of subsurface soil. Construction activities were 

observed at AOI 4 during SI field activities. The CSM for AOI 4 is presented in Figure 7-4. 

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 and PFHxS were detected above their respective SLs, and PFBS was detected below its 

SL in groundwater samples collected at AOI 1. PFOS and PFNA were not detected in 

groundwater. No potable water wells are located at the facility. Drinking water for the Clay NGC 

is supplied by the Air Force Plant 6 drinking water distribution, which is supplied by the Cobb 

County-Marietta Water Authority. The Cobb County-Marietta Water Authority uses the 

Chattahoochee River and Lake Allatoona as its drinking water sources (Marietta Water, 2017). As 

a result, the ingestion exposure pathway for site workers to groundwater is considered 

incomplete. Depths to water at AOI 1 measured in July 2021 during the SI ranged from 15.36 to 

22.42 feet bgs. Conservatively, it is anticipated that intrusive construction activities may reach 

groundwater at these depths. Therefore, groundwater may be encountered during construction 

activities, and the ingestion exposure pathway for future construction workers is considered 

potentially complete. Groundwater at AOI 1 flows southeast towards the facility boundary. There 

are no known drinking water wells downgradient from AOI 1; therefore, the ingestion exposure 

pathway for groundwater is considered incomplete for off-facility residents. The CSM for AOI 1 is 

presented in Figure 7-1. 

7.2.2 AOI 2 

PFOA, PFOS, PFBS, and PFHxS were detected above their respective SLs in groundwater 

samples collected at AOI 2. PFNA was not detected in groundwater. As described in Section 7.2.1, 

drinking water is provided to the facility and the exposure pathway for site workers to groundwater 

is considered incomplete. Depths to water at AOI 2 measured in July 2021 during the SI ranged 

from 13.68 to 16.96 feet bgs. Therefore, groundwater may be encountered during construction 

activities, and the ingestion exposure pathway for future construction workers is considered 

potentially complete. Groundwater at AOI 2 flows southeast towards the facility boundary. There 

are no known drinking water wells downgradient from AOI 2; therefore, the ingestion exposure 

pathway for groundwater is considered incomplete for off-facility residents. The CSM for AOI 2 is 

presented in Figure 7-2. 

7.2.3 AOI 3 

PFOA, PFOS, PFHxS, and PFNA were detected above their respective SLs, and PFBS was 

detected below its SL in groundwater samples collected at AOI 3. As described in Section 7.2.1, 

drinking water is provided to the facility and the exposure pathway for site workers to groundwater 

is considered incomplete. Depths to water at AOI 3 and its potentially upgradient area measured 

in July 2021 during the SI ranged from 10.52 to 32.73 feet bgs. Therefore, groundwater may be 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 7-4

encountered during construction activities, and the ingestion exposure pathway for future 

construction workers is considered potentially complete. Groundwater flow at AOI is to the west 

towards a facility retention basin. There are no known potable wells downgradient from AOI 3; 

therefore, the ingestion exposure pathway for groundwater is considered incomplete for off-facility 

residents. 

PFOA, PFOS, and PFHxS were also detected above their respective SLs, and PFBS was 

detected below its SL in the area potentially upgradient of AOI 3. The CSM for AOI 3 is presented 

in Figure 7-3.

7.2.1 AOI 4 

PFOA, PFOS, and PFHxS were detected in above their respective SLs, and PFBS was detected 

below its SL in groundwater samples collected at AOI 4. PFNA was not detected in groundwater. 

As described in Section 7.2.1, drinking water is provided to the facility and the exposure pathway 

for site workers to groundwater is considered incomplete. Depth to water at AOI 4 measured in 

July 2021 and September/October 2021 during the SI ranged from 23.81 to 29.76 feet bgs. 

Therefore, groundwater is not expected to be encountered during construction activities, and the 

ingestion exposure pathway for future construction workers is considered incomplete. 

Groundwater at AOI 4 flows east towards Big Lake There are no known potable wells 

downgradient from AOI 4; therefore, the ingestion exposure pathway for groundwater is 

considered incomplete for off-facility residents. The CSM for AOI 4 is presented in Figure 7-4. 

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. AOI 1 includes the Hangar 1 area, ramp area, and wash rack. The wash rack currently drains 

to the industrial WWTP and then to the sanitary WWTP. Surface water runoff on the main ramp is 

divided between the northern and southern halves of the ramp area. On the northern half, runoff 

flows north and off of the ramp into a drainage ditch that channels runoff east and then south 

towards the retention basin in the southeastern corner of the facility. Surface water runoff on the 

southern half of the ramp flows south and east towards the retention basin. The retention basin 

includes a storm drain that discharges into Poorhouse Creek, which ultimately discharges to the

Chattahoochee River. The Chattahoochee River is 6 miles to the east of the facility.

Because PFOA, PFOS, PFBS, and PFHxS were detected in soil; and PFOA, PFBS, and PFHxS

were detected in groundwater, it is possible that those compounds may have migrated from soil 

and groundwater at AOI 1 to the retention basin in the southeast corner of the facility’s southern 

property via groundwater discharge or surface water runoff. Therefore, the surface water and 

sediment ingestion exposure pathway for site workers and future construction workers is 

considered potentially complete. Due to potential recreational use of Poorhouse Creek, the 

surface water and sediment ingestion exposure pathway for off-facility recreational users is also 

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

7.3.2 AOI 2 

Surface water runoff at AOI 2 flows into retention basin in the southeastern corner of the facility 

and continues southeast off-facility to Poorhouse Creek. Because PFOA, PFOS, PFBS, PFHxS 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 7-5

and PFNA were detected in soil and PFOA, PFOS, PFBS, and PFHxS were detected in 

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

to Poorhouse Creek via groundwater discharge or stormwater runoff. Therefore, the surface water 

and sediment ingestion exposure pathway for site workers and future construction workers is 

considered potentially complete. The surface water and sediment ingestion exposure pathway for 

off-facility recreational users of Poorhouse Creek is also considered potentially complete. The 

CSM for AOI 2 is presented in Figure 7-2. 

7.3.3 AOI 3 

Surface water runoff at AOI 3 flows west towards the retention basin located behind Hangar 312. 

Runoff entering this retention basin predominantly flows north via an underground pipe beneath 

the runway and discharges into Big Lake, a water body located on Dobbins ARB property. 

Ultimately, Big Lake drains to Rottenwood Creek.

Because PFOA, PFOS, PFBS, PFHxS, and PFNA were detected in soil and groundwater at AOI 

3 and its potentially upgradient area, it is possible that those compounds may have migrated from 

soil and groundwater to the drainage retention basin and ultimately to Big Lake via groundwater 

discharge or stormwater runoff. Therefore, the surface water and sediment ingestion exposure 

pathway for site workers and future construction workers is considered potentially complete. 

Because surface water flows from AOI 3 to Rottenwood Creek, which may be used for recreational 

activities, the surface water and sediment ingestion exposure pathway for off-facility recreational 

users is also considered potentially complete. The CSM for AOI 3 is presented in Figure 7-3. 

7.3.4 AOI 4 

Surface water runoff at AOI 4 flows to the body of water east of the former AASF known as Big 

Lake, which drains to Rottenwood Creek via the Dobbins Spill Pond 4. Because PFOA, PFOS, 

PFHxS, and PFNA were detected in soil, and PFOA, PFOS, PFBS, and PFHxS were detected in 

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

to Big Lake and to Rottenwood Creek via groundwater discharge and surface water runoff. 

Therefore, the surface water and sediment ingestion exposure pathway for site workers and 

construction workers is considered potentially complete. Because Rottenwood Creek may be 

used for recreational purposes, the surface water and sediment ingestion exposure pathway for 

off-facility recreational users is also considered potentially complete. The CSM for AOI 4 is 

presented in Figure 7-4. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 7-6

THIS PAGE INTENTIONALLY BLANK 
in 

SOURCE PATHWAY RECEPTOR

AOI 1

AFFF fire 

suppression 

system storage

Surface Soil

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ 

Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOIs

Surface 

Water/ 

Sediment

Shallow 

Groundwater

Subsurface 

Soil

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Site Worker Construction Worker Recreational User1

Site Worker Construction Worker LEGEND

Figure 7-1

Conceptual Site Model, AOI 1 

Clay NGC

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

/ /

/ / /

/

Ingestion

/

/

/ / / /

/ / /

/

/

/ / /

NOTES

1. The resident and recreational users

refer to off-site receptors.

Resident1

Recreational User Resident 1

1 Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

7-7
Media

SOURCE PATHWAY RECEPTOR

AOI 2

AFFF fire 

suppression 

system storage 

and releases

Surface Soil

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ 

Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOIs

Surface 

Water/ 

Sediment

Shallow 

Groundwater

Subsurface 

Soil

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Site Worker Construction Worker Recreational User1

Site Worker Construction Worker LEGEND

Figure 7-2

Conceptual Site Model, AOI 2

Clay NGC

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

/ /

/ / /

/

Ingestion

/

/

/ / / /

/ / /

/

/

/ / /

NOTES

1. The resident and recreational users

refer to off-site receptors.

Resident1

Recreational User Resident 1

1 Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

7-8
Media

SOURCE PATHWAY RECEPTOR

 AOI 3

AFFF fire 

suppression 

system storage 

and corrosion

Surface Soil

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ 

Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOIs

Surface 

Water/ 

Sediment

Shallow 

Groundwater

Subsurface 

Soil

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Site Worker Construction Worker Recreational User1

Site Worker Construction Worker LEGEND

Figure 7-3

Conceptual Site Model, AOI 3

Clay NGC

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

/ /

/ / /

/

Ingestion

/

/

/ / / /

/ / /

/

/

/ / /

NOTES

1. The resident and recreational users

refer to off-site receptors.

Resident1

Recreational User Resident 1

1 Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

7-9
Media

SOURCE PATHWAY RECEPTOR

AOI 4

Potential AFFF 

storage in 

portable fire 

extinguishers

Surface Soil

Human 

Activities

Precipitation/ 

Run-Off

Leaching/ 

Infiltration

Airborne Soil 

Particulate

Surface Soil 

at AOIs

Surface 

Water/ 

Sediment

Shallow 

Groundwater

Subsurface 

Soil

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

Dust

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Site Worker Construction Worker Recreational User1

Site Worker Construction Worker LEGEND

Figure 7-4

Conceptual Site Model, AOI 4

Clay NGC

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

/ /

/ / /

/

Ingestion

/

/

/ / / /

/ / /

/

/

/ / /

NOTES

1. The resident and recreational users

refer to off-site receptors.

Resident1

Recreational User Resident 1

1 Flow-Chart Continues

Partial / Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

7-10
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 8-1

8. Summary and Outcome

This section summarizes SI activities and findings. The most significant findings are summarized 

in this section and are reproduced directly or abstracted from information contained in this report. 

The outcome provides general and comparative interpretations of the findings relative to the SLs. 

8.1 SI Activities 

The SI field activities were conducted during two mobilizations: the first mobilization took place on

27 May 2021 and 12 July through 16 July 2021, while the second mobilization took place from 29 

September through 1 October 2021 and 20 October 2021. Activities during the first mobilization 

consisted of utility clearance, direct push boring, soil sample collection, temporary monitoring well 

installation, grab groundwater sample collection, and land surveying at the Clay NGC southern 

property. Permission to work on the former GAARNG AASF required a signed Dobbins ARB Civil 

Engineering Dig permit, which was not received until 27 July 2021. As a result, a second 

mobilization was necessary to complete direct push boring, soil sample collection, temporary 

monitoring well installation, grab groundwater sample collection, and land surveying at AOI 4. Field 

activities were conducted in accordance with the SI QAPP Addendum (AECOM, 2021a), except as 

previously noted in Section 5.9. 

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. 

• Thirty (30) soil samples from 11 boring locations; 

• Eleven (11) grab groundwater samples from nine temporary well locations and two 

permanent monitoring wells; 

• Twenty one (21) QA/QC samples. 

An SI is conducted when the PA determines an AOI exists based on probable use, storage, and/or 

disposal of PFAS-containing materials. The SI includes multi-media sampling at AOIs to 

determine whether or not a release has occurred. The SI may conclude further investigation is 

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

required. Additionally, the CSMs were refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at the AOIs, which are 

described in Section 7. 

8.2 Outcome 

Based on the results of this SI, further evaluation is warranted in an RI for AOI 1: Hangar 1/Ramp 

Area, AOI 2: Hangar 300, AOI 3: Hangar 312 and AOI 4: Building 555. Based on the CSMs 

developed and revised in light of the SI findings, the pathway for exposure to drinking water 

receptors from historical DoD activities at AOI 1 through AOI 4 is considered incomplete. Sample 

analytical concentrations collected during the SI were compared against the project SLs in soil 

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

the SLs is as follows: 

• At AOI 1: 

• PFOA and PFHxS in groundwater exceeded their respective SLs. PFOA exceeded 

the SL of 6 ng/L, with a maximum concentration of 99.2 ng/L at location AOI01-01. 

PFHxS exceeded the SL of 39 ng/L, with a maximum concentration of 317 ng/L at 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 8-2

location AOI01-03. PFBS was detected below its SL, and PFOS and PFNA were not 

detected. Based on the results of the SI, further evaluation of AOI 1 is warranted in 

an RI.

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

were below their respective SLs. PFNA was not detected. 

• At AOI 2: 

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

PFOA exceeded the SL of 6 ng/L, with a maximum concentration of 3,650 ng/L at 

AOI02-01. PFOS exceeded the SL of 4 ng/L, with a maximum concentration of 

320,000 J ng/L at location AOI02-01. PFBS exceeded the SL of 601 ng/L, with a 

maximum concentration of 9,430 J- ng/L at location AOI02-01. PFHxS exceeded the 

SL of 39 ng/L, with a maximum concentration of 63,100 ng/L at location AOI02-01. 

PFNA was not detected. Based on the results of the SI, further evaluation of AOI 2 is 

warranted in an RI. 

• PFOS in surface soil exceeded the SL of 13 μg/kg, with a maximum concentration of 

43.9 J μg/kg at location AOI02-02. PFOS in subsurface soil also exceeded the SL of 

160 μg/kg, with a maximum concentration of 609 μg/kg at location AOI02-02. The 

detected concentrations of PFOA, PFBS, PFHxS, and PFNA in soil were below their 

respective SLs. 

• At AOI 3: 

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

PFOA exceed the SL of 6 ng/L, with a maximum concentration of 1,590 ng/L at 

location AOI03-01. PFOS exceeded the SL of 4 ng/L, with a maximum concentration 

of 468 ng/L at AOI03-01. PFHxS exceed the SL of 39 ng/L, with a maximum 

concentration of 329 ng/L at AOI03-01. PFNA exceed the SL of 6 ng/L, with a 

maximum concentration of 16.5 ng/L at location AOI03-01. PFBS was detected 

below its SL at AOI 3. Additionally, PFOA, PFOS, and PFHxS exceeded their 

respective SLs at the potentially upgradient locations CNGC-01 and CNGC-MW030. 

PFOA, PFOS, and PFHxS exceeded the SLs at both upgradient locations, with 

maximum concentrations of 27.9 ng/L at CNGC-MW030, 56.3 ng/L at CNGC-01, 

and 433 ng/L at CNGC-MW030, respectively. PFBS was detected below its SL, and 

PFNA was not detected at the potentially upgradient locations. Based on the results 

of the SI, further evaluation of AOI 3 is warranted in an RI. 

• PFOS in surface soil exceeded the SL of 13 μg/kg at AOI03-01, with a concentration 

of 14.4 μg/kg. The detected concentrations of PFOA, PFBS, PFHxS, and PFNA in 

soil were below their respective SLs.

• At AOI 4: 

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

exceed the SL of 6 ng/L, with a maximum concentration of 64.1 ng/L at location 

AOI04-05. PFOS exceeded the SL of 4 ng/L, with a maximum concentration of 138 

ng/L at AOI04-02. PFHxS exceed the SL of 39 ng/L with a maximum concentration 

of 121 ng/L at location AOI04-05. PFBS was detected below its SL, and PFNA was 

not detected. Based on the results of the SI, further evaluation of AOI 4 is warranted 

in an RI. 

• The detected concentrations of PFOA, PFOS, and PFHxS in soil at AOI 4 were below 

their respective SLs. PFBS and PFNA were not detected. 
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 8-3

Due to the convergence of groundwater flow on the retention basin located west of Hangar 312, 

it is uncertain whether locations CNGC-01 and CNGC-MW030 are upgradient of AOI 3. Based on 

groundwater flow, these locations may not be representative of areas unaffected by potential 

releases at Clay NGC. 

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 Hangar 1/Ramp Area Proceed to RI 

2 Hangar 300 Proceed to RI

3 Hangar 312 Proceed to RI

4 Building 555 Proceed to RI

Legend:

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 8-4

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Site Inspection Report

General Lucius D. Clay National Guard Center, Georgia

AECOM 9-1

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