FINAL 

Site Inspection Report 

Robinson Maneuver Training Center 

North Little Rock, Arkansas 

Site Inspections for Perfluorooctanoic Acid (PFOA), Perfluorooctanesulfonic Acid (PFOS), 

Perfluorohexanesulfonic Acid (PFHxS), Perfluorononanoic Acid (PFNA), Hexafluoropropylene 

oxide dimer acid (HFPO-DA) and Perfluorobutanesulfonic Acid (PFBS) 

ARNG Installations, Nationwide

May 2023 

Prepared for: 

Army National Guard Headquarters 

111 S. George Mason Drive 

Arlington, VA 22204

UNCLASSIFIED
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TABLE OF CONTENTS

Page

LIST OF APPENDICES................................................................................................................ iv

LIST OF FIGURES ........................................................................................................................ v

LIST OF TABLES........................................................................................................................ vii

LIST OF ACRONYMS AND ABBREVIATIONS .................................................................... viii

EXECUTIVE SUMMARY ...................................................................................................... ES-1

1. INTRODUCTION ............................................................................................... 1-1

1.1 PROJECT AUTHORIZATION............................................................... 1-1

1.2 SITE INSPECTION 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 Soil............................................................................................ 2-1

2.2.2 Geology..................................................................................... 2-1

2.2.3 Hydrogeology ........................................................................... 2-2

2.2.4 Hydrology ................................................................................. 2-4

2.2.5 Climate...................................................................................... 2-5

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

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

2.3 HISTORY OF PFAS USE....................................................................... 2-6

3. SUMMARY OF AREAS OF INTEREST........................................................... 3-1

3.1 AOI 1 – ECHO PAD................................................................................ 3-1

3.2 AOI 2 – ALL AMERICAN LANDING/DROP ZONE........................... 3-1

3.3 AOI 3 – BUILDING 28001 ..................................................................... 3-2

3.4 AOI 4 – BUILDING 28002 ..................................................................... 3-3

3.5 AOI 5 – WASH BAY .............................................................................. 3-3

3.6 AOI 6 – BUILDING 70200/70201.......................................................... 3-4

3.7 ADJACENT SOURCES.......................................................................... 3-4

3.7.1 Little Rock Air Force Base ....................................................... 3-4

3.7.2 North Little Rock Municipal Airport........................................ 3-4

4. PROJECT DATA QUALITY OBJECTIVES ..................................................... 4-1

4.1 PROBLEM STATEMENT...................................................................... 4-1

4.2 INFORMATION INPUTS ...................................................................... 4-1

4.3 STUDY BOUNDARIES ......................................................................... 4-1

4.4 ANALYTICAL APPROACH ................................................................. 4-1
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4.5 DATA USABILITY ASSESSMENT...................................................... 4-2

5. SITE INSPECTION ACTIVITIES...................................................................... 5-3

5.1 PRE-INVESTIGATION ACTIVITIES................................................... 5-4

5.1.1 Technical Project Planning ....................................................... 5-4

5.1.2 Utility Clearance ....................................................................... 5-4

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

5.3 TEMPORARY WELL INSTALLATION AND GROUNDWATER 

GRAB SAMPLING................................................................................. 5-6

5.4 SYNOPTIC WATER LEVEL MEASUREMENTS ............................... 5-7

5.5 SURVEYING .......................................................................................... 5-7

5.6 INVESTIGATION-DERIVED WASTE................................................. 5-8

5.7 LABORATORY ANALYTICAL METHODS ....................................... 5-8

5.8 DEVIATIONS FROM SITE INVESTIGATION UFP-QAPP 

ADDENDUM .......................................................................................... 5-8

6. SITE INSPECTION RESULTS .......................................................................... 6-1

6.1 SCREENING LEVELS ........................................................................... 6-1

6.2 SOIL PHYSICOCHEMICAL ANALYSES............................................ 6-2

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

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

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

6.3.3 AOI 1 – Conclusions................................................................. 6-4

6.4 AOI 2 ....................................................................................................... 6-4

6.4.1 AOI 2 – Soil Analytical Results................................................ 6-4

6.4.2 AOI 2 – Groundwater Analytical Results................................. 6-5

6.4.3 AOI 2 – Conclusions................................................................. 6-5

6.5 AOI 3 ....................................................................................................... 6-5

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

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

6.5.3 AOI 3 – Conclusions................................................................. 6-6

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

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

6.6.2 AOI 4 – Groundwater Analytical Results................................. 6-7

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

6.7 AOI 5 ....................................................................................................... 6-7
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6.7.1 AOI 5 – Soil Analytical Results................................................ 6-7

6.7.2 AOI 5 – Groundwater Analytical Results................................. 6-8

6.7.3 AOI 5 – Conclusions................................................................. 6-8

6.8 AOI 6 ....................................................................................................... 6-8

6.8.1 AOI 6 – Soil Analytical Results................................................ 6-9

6.8.2 AOI 6 – Groundwater Analytical Results................................. 6-9

6.8.3 AOI 6 – Conclusions............................................................... 6-10

6.9 ADDITIONAL FACILITY SAMPLING LOCATIONS – DRAINAGE 

PATHWAYS ......................................................................................... 6-10

6.9.1 Additional Facility Sampling Locations – Drainage Pathways –

Soil Analytical Results............................................................ 6-10

6.9.2 Additional Facility Sampling Locations – Drainage Pathways –

Groundwater Analytical Results............................................. 6-11

6.9.3 Additional Facility Sampling Locations – Drainage Pathways –

Conclusions............................................................................. 6-11

7. EXPOSURE PATHWAYS.................................................................................. 7-1

7.1 SOIL EXPOSURE PATHWAY.............................................................. 7-1

7.1.1 AOIs 1, 3, 4, and 5 .................................................................... 7-2

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

7.1.3 AOI 6 ........................................................................................ 7-3

7.2 GROUNDWATER EXPOSURE PATHWAY........................................ 7-3

7.2.1 AOIs 1, 3, 4, and 5 .................................................................... 7-3

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

7.2.3 AOI 6 ........................................................................................ 7-4

7.3 SURFACE WATER AND SEDIMENT EXPOSURE PATHWAY....... 7-4

7.3.1 AOIs within the Robinson Army Airfield (AOI 1, AOI 3, AOI 4, 

and AOI 5) ................................................................................ 7-4

7.3.2 AOI 2 ........................................................................................ 7-5

7.3.3 AOI 6 ........................................................................................ 7-5

8. SUMMARY AND OUTCOME .......................................................................... 8-1

8.1 SITE INSPECTION ACTIVITIES SUMMARY .................................... 8-1

8.2 OUTCOME.............................................................................................. 8-1

9. REFERENCES .................................................................................................... 9-1
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LIST OF APPENDICES

Appendix A. 2022 Aqueous Film-Forming Foam Spill Record

Appendix B. Data Usability Assessment and Data Validation Reports

Appendix C. Field Documentation

C1. Logs of Daily Notice of Field Activities

C2. Sampling Forms 

C3. Survey Data

C4. Field Change Request Form 

Appendix D. Photographic Log

Appendix E. Technical Project Planning Meeting Minutes

Appendix F. Analytical Results

Appendix G. Boring Logs and Well Construction Diagrams

Appendix H. Laboratory Reports
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LIST OF FIGURES

Figure 2-1. Facility Location

Figure 2-2. Facility Topography

Figure 2-3. Groundwater Features

Figure 2-4. AOI 1, AOI 3, AOI 4, and AOI 5 Groundwater Elevations

Figure 2-5. AOI 2 Groundwater Elevations

Figure 2-6. AOI 6 Groundwater Elevations

Figure 2-7. Surface Water Features

Figure 3-1. Areas of Interest

Figure 5-1. AOI 1, AOI 3, AOI 4, and AOI 5 Site Inspection Sample Locations

Figure 5-2. AOI 2 Site Inspection Sample Locations

Figure 5-3. AOI 6 Site Inspection Sample Locations

Figure 6-1. AOI 1, AOI 3, AOI 4, and AOI 5 PFOS Detections in Soil

Figure 6-2. AOI 1, AOI 3, AOI 4, and AOI 5 PFOA Detections in Soil

Figure 6-3. AOI 1, AOI 3, AOI 4, and AOI 5 PFBS Detections in Soil

Figure 6-4. AOI 1, AOI 3, AOI 4, and AOI 5 PFNA Detections in Soil

Figure 6-5. AOI 1, AOI 3, AOI 4, and AOI 5 PFHxS Detections in Soil

Figure 6-6. AOI 1, AOI 3, AOI 4, and AOI 5 PFOS, PFOA, and PFBS Detections in 

Groundwater

Figure 6-7. AOI 1, AOI 3, AOI 4, and AOI 5 PFNA and PFHxS Detections in Groundwater

Figure 6-8. AOI 2 PFOS Detections in Soil

Figure 6-9. AOI 2 PFOA Detections in Soil

Figure 6-10. AOI 2 PFBS Detections in Soil

Figure 6-11. AOI 2 PFNA Detections in Soil
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LIST OF FIGURES (continued)

Figure 6-12. AOI 2 PFHxS Detections in Soil

Figure 6-13. AOI 2 PFOS, PFOA, and PFBS Detections in Groundwater

Figure 6-14. AOI 2 PFNA and PFHxS Detections in Groundwater

Figure 6-15. AOI 6 PFOS Detections in Soil

Figure 6-16. AOI 6 PFOA Detections in Soil 

Figure 6-17. AOI 6 PFBS Detections in Soil

Figure 6-18. AOI 6 PFNA Detections in Soil

Figure 6-19. AOI 6 PFHxS Detections in Soil

Figure 6-20. AOI 6 PFOA, PFOS, and PFBS Detections in Groundwater

Figure 6-21. AOI 6 PFHxS and PFNA Detections in Groundwater

Figure 7-1. Conceptual Site Model, AOIs 1, 3, 4 and 5 

Figure 7-2. Conceptual Site Model, AOI 2

Figure 7-3. Conceptual Site Model, AOI 6
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LIST OF TABLES

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

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

Table 5-1. Samples by Medium, RMTC, North Little Rock, Arkansas, Site Inspection Report

Table 5-2. Soil Boring Depths and Temporary Well Screen Intervals, RMTC, North Little 

Rock, Arkansas, Site Inspection Report

Table 5-3. Groundwater Elevation, RMTC, North Little Rock, Arkansas, Site Inspection 

Report

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

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

Report, RMTC

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

Inspection Report, RMTC

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

Inspection Report, RMTC

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

Report, RMTC

Table 8-1. Summary of Site Inspection Findings and Recommendations
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LIST OF ACRONYMS AND ABBREVIATIONS

°C Degrees Celsius

% Percent

μg/kg Microgram(s) per kilogram

AASF Army Aviation Support Facility 

AECOM AECOM Technical Services, Inc. 

AFB Air Force Base

AFFF Aqueous film-forming foam

amsl Above mean sea level

AOI Area of Interest

ARARNG Arkansas Army National Guard

ARFF Aircraft rescue and firefighting

ARNG Army National Guard

bgs Below ground surface

btoc Below top of casing

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CRFD Camp Robinson Fire Department

CSM Conceptual site model

DoD Department of Defense

DQO Data Quality Objectives

EA EA Engineering, Science, and Technology, Inc., PBC

EB Equipment blank

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

FB Field blank

FD Field duplicate

FedEx Federal Express

ft Foot (feet)

gal Gallon(s)

Genesis Genesis Environmental Consulting, Inc.

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

LOQ Limit of quantification
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LIST OF ACRONYMS AND ABBREVIATIONS (continued)

MIL-SPEC Military specification

MS Matrix spike

MSD Matrix spike duplicate

NA Not applicable

ng/L Nanogram(s) per liter

No. Number

OSD Office of the Assistant Secretary of Defense

PA Preliminary Assessment

PFAS Per- and polyfluoroalkyl substances

PFBS Perfluorobutanesulfonic acid

PFHxS Perfluorohexane sulfonate

PFNA Perfluorononanoic acid

PFOA Perfluorooctanoic acid

PFOS Perfluorooctanesulfonic acid

PID Photoionization detector

PVC Polyvinyl chloride

QAPP Quality Assurance Project Plan

QSM Quality Systems Manual

RI Remedial investigation 

RMTA Robinson Maneuver and Training Area

RMTC Robinson Maneuver Training Center

SI Site inspection

SL Screening level

TOC Total organic carbon

TPP Technical Project Planning

UFP Uniform Federal Policy 

USACE U.S. Army Corps of Engineers

USEPA U.S. Environmental Protection Agency

VSI Visual site inspection

WWII World War II
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EXECUTIVE SUMMARY

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

Inspections (SIs) at ARNG facilities nationwide based 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) (Assistant Secretary of 

Defense) dated 6 July 2022. The six compounds listed in the OSD memorandum include 

perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic 

acid (PFBS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), and

hexafluoropropylene oxide dimer acid (HFPO-DA)

1

. These compounds are collectively referred 

to as “relevant compounds” throughout the document and the applicable Screening Levels (SLs) 

are provided below in Table ES-1.

The PA identified two Areas of Interest (AOIs) where PFAS-containing materials may have been

stored, disposed, or released historically. Four additional AOIs were added as a result of the 

scoping process (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 to 

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

immediate threats, or no further action is required based on a comparison of SI results to 

screening levels (SLs) for the relevant compounds. This SI was completed at the Robinson 

Maneuver Training Center (RMTC) in North Little Rock, Arkansas, and determined further 

evaluation under the Comprehensive Environmental Response, Compensation, and Liability Act 

(CERCLA) is warranted for AOI 1, AOI 3, AOI 4, AOI 5, and AOI 6. RMTC will be referred to 

as the “Facility” throughout this document.

The Facility, operated by the Arkansas Army National Guard (ARARNG), encompasses 

approximately 31,900 acres in Pulaski and Faulkner counties within North Little Rock, 

Arkansas. First established in 1917 as Camp Pike, and later renamed to Camp Joseph T. 

Robinson, the Facility was used for basic training through World War II. After World War II, the 

Facility was declared surplus and deeded to the Arkansas State Military Department for its use as 

an ARNG facility. The Facility was eventually renamed RMTC and is utilized by the ARARNG 

for professional military education and infantry training. The Facility is located in the northeast 

edge of the Ouachita Mountain physiographic province and lies on the southeast corner of the 

Fourche Mountains. The Arkansas River is located immediately southwest of the Facility. 

The PA identified two potential PFAS release areas at the Facility: the Echo Pad and 

All American Landing/Drop Zone (AECOM Technical Services, Inc. 2020). As a result of the SI 

scoping process, four additional storage areas/potential release areas were identified, including: 

Building 28001, Building 28002, the Wash Bay, and Building 70200/70201. The potential release 

areas were categorized into six separate AOIs. SI sampling results from the six AOIs were 

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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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 3, AOI 4, AOI 5, and AOI 6.

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

Analyte

Residential

(Soil)

(μg/kg)

1

0 to 2 ft bgs

Industrial/Commercial

Composite Worker

(Soil)

(μg/kg)

1

2 to 15 ft bgs

Tap Water

(Groundwater)

(ng/L) 1

PFOA 19 250 6

PFOS 13 160 4

PFBS 1,900 25,000 601

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

1. Assistant Secretary of Defense. July 2022. Risk Based Screening Levels Calculated for 

Groundwater and Soil using U.S. Environmental Protection Agency’s (USEPA’s) Regional 

Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.

2. 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.

g/kg = Microgram(s) per kilogram

ng/L = Nanogram(s) per liter

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 Echo Pad NA Proceed to RI

2

All American 

Landing/Drop Zone NA No further action

3 Building 28001 NA Proceed to RI

4 Building 28002 NA Proceed to RI

5 Wash Pad NA Proceed to RI

6 Building 70200/70201 NA Proceed to RI

Legend:

 = Detected; exceedance of SLs

 = Detected; no exceedance of SLs

 = Not detected

NA = Not applicable

RI = Remedial investigation
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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) at ARNG facilities nationwide based on the current 

or potential historical use of per- and polyfluoroalkyl substances (PFAS) with a focus on 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 components listed in the OSD

memorandum will be referred to as “relevant compounds” throughout this document and include 

perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic 

acid (PFBS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), and 

hexafluoropropylene oxide-dimer acid (HFPO-DA)2at ARNG facilities nationwide. The ARNG 

performed this SI at the Robinson Maneuver Training Center (RMTC) in North Little Rock, 

Arkansas. RMTC will be referred to as the “Facility” throughout this report.

The SI project elements were performed in accordance with the Comprehensive

Environmental Response, Compensation, and Liability Act (CERCLA) (U.S. 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 Army requirements and guidance for field investigations.

1.2 SITE INSPECTION PURPOSE

A PA was performed at RMTC (AECOM Technical Services, Inc. [AECOM] 2020) that 

identified two Areas of Interest (AOIs) where PFAS-containing materials were used, stored, 

and/or disposed, or areas where known or suspected releases to the environment occurred. 

During scoping, four additional AOIs were added. The objective of the SI is to identify whether 

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

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

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

2 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

RMTC occupies approximately 31,900 acres in Pulaski and Faulkner counties within North

Little Rock, Arkansas. The Facility is approximately 2 miles north and east of the Arkansas

River, 2.5 miles north and east of Little Rock, and 4 miles west of Little Rock Air Force Base 

(AFB). Figure 2-1 illustrates the location of the current RMTC (AECOM 2020).

The Facility was first established in 1917 as Camp Pike and consisted of 6,000 acres, which was 

expanded to 48,188 acres during World War II (WWII) and renamed Camp Joseph T. Robinson. 

Camp Joseph T. Robinson was a basic training facility through WWII and was used to house

German prisoners of war. The Facility was declared surplus after WWII and deeded to the 

Arkansas State Military Department for use as a National Guard facility. After the WWII 

expansion, approximately 16,300 acres were turned over to various public and private 

organizations (AECOM 2020). Currently, the Facility is used by the Arkansas ARNG 

(ARARNG) for professional military education and infantry training (Robinson Maneuver and 

Training Area [RMTA] 2001). 

2.2 FACILITY ENVIRONMENTAL SETTING

RMTC is in the northeast edge of the Ouachita Mountain physiographic province and lies on the 

southeast corner of the Fourche Mountains. The topography is characterized as hilly, with steep 

east-west hog-back ridges, which were developed on the limbs of anticlines and synclines 

formed during the Ouachita orogeny (RMTA 2001). These ridges also enclose numerous valleys 

and watersheds. Locally, elevations range from 255 to 590 feet (ft) above mean sea level (amsl). 

The Arkansas River is located immediately southwest of the Facility (AECOM 2020). 

2.2.1 Soil

The soils at RMTC are generally very low to moderately low permeability and are heavily 

influenced by the surrounding geology; they are composed of clays, silty clays, and some sand

(RMTA 2001). Carnasaw soil complexes are abundant and include Carnasaw gravelly loam, 

Carnasaw-Pirum Littlefir silt loam, Olmstead silt loam, Pirum fine sandy loam, Psyam silt loam, 

and Purdham gravelly loam (Genesis Environmental Consulting Inc. [Genesis] 2005). The heavy 

clays and silt encourage runoff and prevent the development of a significant surface aquifer. The 

Carnasaw, Littlefir, Pirum, and Purdham soils are dominant on hills and ridges, whereas the 

Cato, Psyam, Olmstead, and Maumelle soils are found in valleys and depressions (AECOM 

2020). Soils encountered during the SI activities consisted of interbedded sands, silty clays, and 

clays of varying plasticity from the Carnasaw soil complexes (RMTA 2001).

2.2.2 Geology

RMTC is located within the Ouachita Mountain physiographic province. The Ouachita 

mountains, which rise to 2,130 ft amsl, extend from the northwestern edge of the Mississippi 

Embayment, approximately 125 miles west, to the Gulf Coastal Plain in western Arkansas and 

Oklahoma. The Ouachita Mountain province near RMTC is characterized by Paleozoic bedrock 
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formations displayed and folded into east-west trending broad synclines and narrow anticlines.

(McFarland 2004). Steep ridges were formed from folding and differential weathering of more 

resistant sandstones and less resistant shales. To the east and southeast of the Facility is the fall 

line between the Ouachita Mountain province and the Mississippi Alluvial Plain province, which 

consists of thick Quaternary alluvial layers. The local surface geological formations exposed at 

RMTC are described below (AECOM 2020):

• Quaternary alluvial deposits: The youngest layer at RMTC comprises Quaternary 

alluvium deposits of gravels, sands, silts, and clays. These deposits are the result of 

erosion and reworking of deposits by streams. There are also lenticular and discontinuous 

Quaternary terrace deposits consisting of unconsolidated gravels, sand, silts, and clays. 

These layers vary in thickness across the area (Genesis 2005).

• Atoka Group: Underlying the Quaternary deposits is the Atoka Formation, which is up to 

25,000 ft thick and has the largest areal extent of any Paleozoic formation in Arkansas

(McFarland 2004). The Atoka Group is a marine sequence of silty sandstones and black 

shales (McFarland 2004). The Atoka Group is subdivided into upper, middle, and lower 

formations based on the distinct shale and sandstone units. The Atoka Group gradually 

decreases in thickness to the south and conformably overlies the Johns Valley Shale, 

which does not outcrop at RMTC. The Atoka Group unconformably overlies the Jackfork 

Sandstone Group on the Facility (Genesis 2005).

• Jackfork Sandstone Group: The Jackfork Sandstone Group varies in thickness from 

3,500 to 6,000 ft. It is a Pennsylvanian-age formation with fine to coarse sandstones, as 

well as brown silty sandstones and gray-black shales (McFarland 2004). The Jackfork 

Sandstone Group has been deformed during mountain building processes similar to other 

formations in the area. The Jackfork Sandstone is known to host lead- and zinc-bearing 

quartz veins (Arkansas Geological Survey 2011).

During the SI, unconsolidated silts, sands, and clays and their diagenetic analogs were observed 

as the dominant lithology below RMTC. The borings were completed at depths between 4.5 and 

20 ft below ground surface (bgs). Layers of poorly graded and clayey sand with fat and lean clay 

lenses of varying thickness and fill material including asphalt and rock were encountered during 

drilling. Samples for grain size analyses were collected at four locations, AOI01-01, AOI02-04, 

AOI03-02, and AOI05-02, and analyzed via American Society for Testing and Materials 

(ASTM) Method D-422. The results indicate that the soil samples are comprised primarily of silt 

(48.7 [percent] % to 65.6%) and clay (23% to 34%).

2.2.3 Hydrogeology

Groundwater on RMTC occurs primarily in fractures, joints, and other openings in the shale and 

sandstone units. Based on drilling logs from monitoring wells installed at the Facility, shallow 

bedrock can occur from as little as 8 inches to 48 ft bgs (Genesis 2005). The overburden above 

bedrock generally consists of clay or silty clay, which impedes the development of a significant 

surface aquifer. The fractures and secondary openings of the sandstone and shale units can yield 
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water; however, wells are generally less than 300 ft deep and produce less than 10 gallons (gal)

per minute (Genesis 2005).

The water table generally mimics surface topography (Figure 2-2), and the generalized flow 

direction in the northern half of the Facility is to the southwest and in the southern half to the 

northeast, although some local variations exist across the Facility and surrounding the AOIs

(Genesis 2005). This generally correlates with the direction of groundwater flow (Figure 2-3). 

The Facility and the majority of Central Arkansas receive potable water from Central Arkansas 

Water via surface water intakes at Lake Maumelle (URS Group, Inc. and Arcadis 2013).

Groundwater is not used for any purposes at RMTC but may be present at shallow occurrences 

(less than 6 ft bgs). Multiple facility monitoring wells surround two operational range areas that

are depicted in the PA (AECOM 2020).

Depths to groundwater encountered during the SI (October 2021) were recorded to be between 

0.2 to 18.8 ft bgs. Groundwater flow direction, based on observed groundwater elevations during 

the SI activities, varied by location. It should be noted that during sample collection groundwater 

elevations could be off slightly due to settlement and placement of the stadia rod during 

surveying. Final depth to water measurements at all locations used for potentiometric maps and 

tables were collected after surveying had been completed, so these elevations were not affected

and are therefore correct.

Groundwater flow direction at the Robinson Army Airfield (AOIs 1, 3, 4, and 5) follows facility

topography and generally flows east along a centrally located groundwater divide (Figure 2-4). 

Soil encountered during drilling was generally comprised of layers of tight silt and clay lenses 

and poorly graded sands, which limits groundwater flow.

Groundwater generally flows to the southeast at AOI 2 (Figure 2-5). Soil encountered during

drilling was comprised of tight clays and silts. Well recharge during drilling was very slow.

Groundwater generally flows to the east/southeast at AOI 6 (Figure 2-6); however, based on the 

linear distribution of the groundwater elevation data collected at AOI 6, groundwater flow 

direction may not be entirely accurate at this location. Shallow groundwater likely follows 

topography, which decreases in elevation to the south. According to base personnel, in order to 

elevate building 70200/70201 (Camp Robinson Fire Department [CRFD] Building), fill was 

placed prior to construction. Soil encountered during drilling was comprised of low permeable 

silts, clays, and clayey and silty sands.

Groundwater is used as a potable water source east of the fall line, which delineates the contact 

between local bedrock and the thick alluvial deposits of the Mississippi Alluvial Plain province. 

These alluvial sequences are very thick and yield significant amounts of high-quality 

groundwater. Several municipalities outside of a 4-mile radius and east of RMTC use these for 

potable water. However, these wells are drilled into the Sparta aquifer, which is a very deep (600

to 1,000 ft bgs) confined aquifer not hydraulically connected to geologic formations underlying 

the Facility (URS Group, Inc. and Arcadis, 2013). 
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2.2.4 Hydrology

There are several streams, both perennial and intermittent, that drain surface water at RMTC

(Figure 2-7). Because of the anticline-syncline structures, surface drainage is circuitous at 

RMTC. In the northern half of the Facility, Clifton Mountain acts as a barrier and directs surface

water flow into Jim Creek and Mile Creek (and an unnamed smaller tributary), which merge and 

drain into the wetlands surrounding the 1.5-square-mile Grassy Lake (also known as Clear Lake)

(RMTA 2001). These streams may flow intermittently during drier periods (AECOM 2020).

South of Clifton Mountain, Leopard Creek drains the eastern half of the Facility, and an 

unnamed stream drains west to Tupelo Gum Pond and a wetland area. White Oak Bayou flows 

westward and eventually drains into the Arkansas River after passing through several low 

wetland areas and Devoe Lake. The cantonment area is drained by several small unnamed 

streams and drainage ditches into Engineers Lake. This lake is drained by Five Mile Creek, 

which then flows easterly toward Trammel Lake (RMTA 2001).

Drainage swales and Outfalls 001 through 005 surround the outer perimeter of the Robinson 

Army Airfield, leading to neighboring tributary creeks of the Arkansas River. Swales 

surrounding the Echo Pad (AOI 1) are connected to Outfalls 004 and 005. Swales and 

stormwater collector pipes surrounding Building 28001 (AOI 3) discharge primarily to Outfall 

001 (draining the paved areas surrounding the building) and to a lesser extent Outfall 002

(draining northwest of the building). Building 28002 (AOI 4) and the Wash Bay (AOI 5) are also 

connected to Outfall 001. Outfalls 001, 002, and 004 drain to Newton Creek and White Oak

Bayou before intersecting with the Arkansas River, located 14 miles away. Outfall 005 drains to 

Spring Creek, Miles Creek, Kellogg Creek, and Bayou Meto before intersecting with the 

Arkansas River.

Surface runoff near the All American Landing/Drop Zone (AOI 2) drains southeasterly, 

eventually discharging to the Arkansas River. Surface runoff at the Fire Station (AOI 6) drains 

by sheet flow into nearby swales, diverting the water south to an unnamed ephemeral stream and 

eventually discharging to Shilcotts Bayou and the Arkansas River at Greathouse Bend.

Runoff is relatively rapid and excessive when there is heavy rainfall because of shallow bedrock

and relatively impermeable clay soils. Shallow groundwater levels are influenced by surface 

water leakage; however, when compared to the volume of surface water runoff, the shallow clays 

restrict the infiltration of water. Locally, the streams and creeks exiting RMTC are small, muddy, 

and slow flowing. Several streams exiting RMTC, observed during a 2013 Operational Range 

Phase I site visit (URS Group, Inc. and Arcadis 2013), were slow flowing, likely due to the dry 

weather, and could conceivably stop flowing during drought and near-drought conditions. Offfacility wetland geographic information system data were unavailable from the U.S. Fish and 

Wildlife Service; however, wetlands data were available from the Arkansas State Transportation 

Department. There are wetlands in and around RMTC in localized areas near surface water (such 

as Five Mile Creek) and to the east where Kellogg, Miles, and Spring Creeks discharge on the 

Arkansas River floodplain. Several sewage disposal ponds are located in the wetlands 

approximately 4 miles southeast of the Facility. Kellogg and Woodruff creeks pass near sewage 

disposal areas before eventually entering the Arkansas River. Surface water features, including 
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streams and their flow direction, lakes, watersheds, ponds, and wetlands, are shown in 

Figure 2-7 (AECOM 2020). 

2.2.5 Climate

The climate of the RMTC area is characterized by hot summers and moderately cool winters.

The average high temperature for the summer is 91 degrees Fahrenheit, and the average winter 

low temperature is 35 degrees Fahrenheit. The area receives an average of 50 inches of 

precipitation throughout the year. Generally, the heaviest rains are in the spring, and the driest 

months are from July to September, during which minor droughts occasionally occur. Severe

thunderstorms and tornadoes can occur during the late spring and early summer months. RMTC 

receives an average of 4.4 inches of snowfall per year (National Weather Service 2019). 

2.2.6 Current and Future Land Use

The Facility is used by the ARARNG for professional military education and infantry training on 

its three primary range areas. There are 26 areas used for non-live-fire maneuver training. The 

maneuver and training ranges are north of the cantonment area and cover most of the Facility. 

The Robinson Army Airfield is the military airfield within RMTC, where AOIs 1, 3, 4, and 5 

were identified. The airfield is located west of the cantonment area and south of the mountain 

biking trail system (Little Rock Convention and Visitors Bureau 2022), and it contains an Army 

Aviation Support Facility (AASF). RMTC is also used for Arkansas National Guard 

administrative, logistical, and maintenance directorates. Reasonably anticipated future land use is 

not anticipated to change from the current land use (AECOM 2020). The Facility is enclosed 

within fencing and access is restricted, however recreational users can access mountain biking 

trails and hunting areas.

2.2.7 Sensitive Habitat and Threatened/Endangered Species

Wildlife surveys have been conducted at RMTC; one was completed from 19 April – 30 July 

1999 (George Miksch Sutton Avian Research Center 2022). The Facility has significant areas of 

habitat; however, none are considered critical habitats. 

The following species are listed as federally endangered, threatened, proposed, and/or candidate 

species in Pulaski and Faulkner counties, Arkansas (U.S. Fish and Wildlife Service 2022), 

although these species have not been observed at RMTC:

• Birds: Eastern Black Rail (Laterallus jamaicensis ssp. jamaicensis) – Federally 

Threatened; Piping Plover (Charadrius melodus) – Federally Threatened; and Red Knot 

(Calidris canutus rufa) – Federally threatened

• Clams: Arkansas Fatmucket (Lampsilis powellii) – Federally Threatened; Pink Mucket 

(pearlymussel, Lampsilis abrupta) – Federally Endangered; Rabbitsfoot (Quadrula 

cylindrica cylindrica) – Federally Threatened; and Winged Mapleleaf (Quadrula 

fragosa) – Federally Endangered

• Insects: Monarch Butterfly (Danaus plexippus) – Federal Candidate
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• Mammal: Indiana Bat (Myotis sodalist) – Federally Endangered; and Northern Longeared Bat (Myotis septentrionalis) – Federally Threatened.

2.3 HISTORY OF PFAS USE

Two potential PFAS release areas were identified at RMTC during the PA at locations where 

aqueous film-forming foam (AFFF) may have been used or released historically (AECOM 

2020). Four additional potential release areas/storage areas were identified and added during the 

scoping of the SI. Interviews and records obtained during the PA indicate that fire training 

activities were conducted, from as early as 2006 until 2018, with AFFF at the Echo Pad located 

in the Robinson Army Airfield. Additionally, three separate facilities located within the 

Robinson Army Airfield (Building 28001, Building 28002, and the Wash Bay) have historically 

stored AFFF within their fire suppression systems and two have had known releases of their 

contents. In addition to these areas, firetrucks capable of holding AFFF have also been staged 

within the RMTC at two additional locations, the All American Landing/Drop Zone and 

Buildings 70200/70201 (Fire Station). Due to the corrosive nature of AFFF and the potential for 

leaks, these locations are also considered potential release areas. 

A description of each AOI is presented in Section 3.
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Figure 2-1

Facility Location

Robinson Maneuver

Training Center

3

0 5

Miles

Facility Data

Facility Boundary

AR

^_

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Figure 2-2

Facility Topography

Robinson Maneuver

Training Center

3

0 2

Miles

Facility Data

Facility Boundary

AR

^_

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Figure 2-3

Groundwater Features

<!

<! <!

<! <!

<!

<! <!

<! <! <!

<!

<!

<!

<!

<!

<!

<! <!

<!

<!

<!

<!

<!

<!

<!

<!

<!

Jim Creek

White Oak Bayou

Leopard Creek

Bridge Creek

Newton Creek

Mile Creek

Kellogg Creek

Miles Creek

Little 

Creek

Spring Creek

Pierce Creek

Palarm Creek

Gap Creek

Arkansas River

Winifree Creek

3

0 2

Miles

Facility Data

Facility Boundary

Well Type

<!

Monitoring Well

Hydrology/Hydrogeology

Inferred Groundwater Flow Direction

Perennial Creek/Stream

Intermittent Creek/Stream

Wetlands

AR

^_

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Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Figure 2-4

AOI 1, AOI 3, AOI 4 and AOI 5

Groundwater Elevations

<!

<!

<!

<!

<!

<!

<! <!

<!

<!

<!

<!

<!

<!

<!

<!

<!

RMTC-03

580.18

RMTC-02

574.17

RMTC-01

564.34

AOI05-03

566.18

AOI05-02

570.54

AOI04-02

590.29

AOI04-01*

582.61

AOI03-03

586.60

AOI03-02

581.90

AOI03-01

580.80

AOI01-07

585.31

AOI01-06

585.38

AOI01-05

587.95

AOI01-04*

569.45

AOI01-03

580.88

AOI01-02

579.44

AOI01-01

559.43

AOI 1

Echo Pad

AOI 3

Building

28001

AOI 5

Wash Bay

AOI 4

Building

28002

Outfall 004

Outfall 003

Outfall 002

Outfall 001

Outfall 005

575

580

585

565

570

590

585

580

575

565 570

3

0 500

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

<! Well Location

Groundwater Flow Direction

Groundwater Elevation

Contour (5 foot interval)

Dashed where inferred

Map Extent

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Data Sources:

ESRI 2022

AECOM 2019

AOI03-01 = Sample ID

580.98 = Groundwater Elevation (in feet)

Note:

* Well location not used for contouring.

Date:..............................May 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Figure 2-5

AOI 2

Groundwater Elevations

<!

<!

<!

<!

AOI02-04

368.05

AOI02-03

360.61

AOI02-02

357.13

AOI02-01

360.15

AOI 2

All American

Landing/Drop Zone

360

362

364

366

368

358

3

0 100

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

<! Well Location

Groundwater Flow Direction

Groundwater Elevation

Contour (2 foot interval)

Map Extent

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Data Sources:

ESRI 2022

AECOM 2019

AOI02-01 = Sample ID

360.25 = Groundwater Elevation (in feet)

Date:..............................May 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Figure 2-6

AOI 6

Groundwater Elevations

<!

<!

<!

<!

AOI06-04-Off

510.94

AOI06-03

510.77

AOI06-02*

508.67

AOI06-01-Off

516.57

AOI 6

Buildings

70200/70201

Fire Station

512

514

516

3

0 100

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

<! Well Location

Groundwater Flow Direction

Groundwater Elevation

Contour (2 foot interval)

Map Extent

Army National Guard Site Inspections

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Data Sources:

ESRI 2022

AECOM 2019

AOI06-02 = Sample ID

508.77 = Groundwater Elevation (in feet)

Note:

* Well location not used for contouring.

Date:..............................May 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Figure 2-7

Surface Water Features

Jim Creek

White Oak Bayou

Leopard Creek

Bridge Creek

Newton Creek

Mile Creek

Kellogg Creek

Miles Creek

Little 

Creek

Spring Creek

Pierce Creek

Palarm Creek

Gap Creek

Arkansas River

Winifree Creek

File Mile Creek

Upper Bayou

Meto Watershed

Palarm Creek

Watershed

Fourche Creek-Arkansas

River Watershed

3

0 2

Miles

Facility Data

Facility Boundary

Hydrology

Surface Water Flow Direction

Perennial Creek/Stream

Intermittent Creek/Stream

Waterbody

Wetlands

Watershed Boundary

AR

^_

Army National Guard Site Inspections

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Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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3. SUMMARY OF AREAS OF INTEREST

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

or released historically. AFFF storage areas, and areas of compliance demonstrations. Six AOIs 

were identified at the Facility: AOI 1 − Echo Pad, AOI 2 − All American Landing/Drop Zone, 

AOI 3 − Building 28001, AOI 4 − Building 28002, AOI 5 − Wash Pad, and AOI 6 − Building 

70200/70201. Two of the AOIs were designated as AOIs in the PA and four more AOIs were 

added based on either a recorded PFAS release or storage. The potential AOIs are shown on 

Figure 3-1. 

3.1 AOI 1 – ECHO PAD

AOI 1 consists of the Echo Pad, an approximately 4-acre aircraft, asphalt ramp/pad located at the 

Robinson Army Airfield. The pad was historically used for aircraft parking and fire training 

activities but is currently unused. The AASF Fire Chief reported that 3% AFFF of varying 

brands was used during the fire training activities. Activities at the Echo Pad involved 

extinguishing live burns, pump and roll exercises, and nozzle testing on mock vehicles at an 

approximately annual frequency. The most recent event using AFFF was a nozzle testing 

exercise that occurred in November 2018. Prior to that event, fire training did not occur in the 

past 5 years, and the last large-scale fire training event occurred approximately 13 years ago, 

when the AASF Fire Chief started his tenure at the Facility. It is unknown when fire training 

activities began and what might have occurred prior to the tenure of the current AASF Fire Chief 

(AECOM 2020).

During a large-scale fire training event, personnel would spray the entire pad with AFFF. An 

estimated 45 gal of AFFF would be discharged from an old firetruck with a 60-gal foam tank 

capacity. Typically, smaller-scale fire training events involved discharging AFFF in short bursts 

from the nozzle. All AFFF discharged on the Echo Pad was typically hosed down afterwards 

with water, and the runoff would drain radially from the pad (AECOM 2020).

During the visual site inspection (VSI) of the Echo Pad, conducted as part of the PA, multiple 

cracks were observed throughout the pavement. A mock vehicle and Conex box were also 

observed stationed at the northern corner of the Echo Pad, where it was indicated that personnel 

would practice target spraying of the firehose. Drainage swales surround most of the Echo Pad 

and connect to Outfalls 004 and 005, which drain to the north and to the southeast, respectively, 

to tributary creeks of the Arkansas River (AECOM 2020). The outfall locations are shown on 

Figure 2-4.

3.2 AOI 2 – ALL AMERICAN LANDING/DROP ZONE

AOI 2 consists of the All American Landing/Drop Zone, an approximately 471-acre property 

leased to the Department of the Air Force since 1996. The property contains two adjacent 

runways and is used by the Little Rock AFB for touch-and-go landing exercises. One Little Rock 

AFB firetruck with a 210-gal AFFF capacity and one water tender are typically stationed in a 

gravel parking area along the northern runway during touch-and-go exercises. Both the Camp 

Robinson Fire Department (CRFD) Fire Chief and Little Rock AFB Fire Chief stated that no 

activities or emergency responses involving AFFF discharge by either the Little Rock AFB or 
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CRFD have occurred within the area. The Little Rock AFB Fire Chief additionally stated he has 

not observed any AFFF leakage from the firetruck during his tenure of 32 years. However, 

according to the 2015 PFAS PA report for Little Rock AFB, the Little Rock AFB firetrucks have 

been known to occasionally leak AFFF due to the corrosive nature of the material (AECOM 

2020). 

3.3 AOI 3 – BUILDING 28001

AOI 3 consists of Building 28001, the current AASF operational building located at the 

Robinson Army Airfield. The building serves as a hangar and fire station and is equipped with an 

AFFF fire suppression system. The fire suppression system is connected to a 1,400-gal tank that 

currently contains Ansulite 3% AFFF Mil Spec C6 foam (AECOM 2020).

According to the AASF Fire Chief, two aircraft rescue and firefighting (ARFF) vehicles contain 

3% AFFF of varying brands and remain parked at the AASF fire station. Vehicles ARFF-1 and 

ARFF-2 have foam capacity tanks of 100 gal and 30 gal, respectively. These vehicles were 

reportedly filled with AFFF in front of the fire station. Minimal spills occasionally occurred in 

the process of refilling the ARFF vehicles; however, the AASF Fire Chief stated that spill pads 

were always placed underneath the vehicles when being serviced. The spill pads were doublebagged and then disposed of into a dumpster (AECOM 2020).

Annual testing on the fire suppression system is performed by a contractor and involves 

equipment checks of pressure gauges. No false trips have occurred since the building 

construction and installment of the system in 2006. The AFFF tank was serviced most recently in 

January 2019, when the contractor changed out the original contents of the tank from Chemguard 

6% AFFF C-601MS foam to Ansulite 3% AFFF Mil Spec C6 foam (AECOM 2020). 

During the PA VSI, rust staining with white residue was observed on the concrete floor of the 

fire suppression system tank room, leading into a floor drain. RMTC personnel stated that the 

staining was most likely from water leaks, but an AFFF leak was possible. The floor drain is 

connected to the Facility wastewater treatment plant. All fire extinguishers observed within the 

building and in the immediate vicinity of the building were dry chemical fire extinguishers 

(non-AFFF) (AECOM 2020).

During a teleconference conducted on 19 February 2021 for the scoping of the SI, ARARNG 

personnel indicated that, in 2018, the AFFF tank was discovered to be only 15−20% full due to a 

leak in the tank bladder system. This leak allowed AFFF to enter the pressurized water source for 

the fire hydrants. As a result, when a nearby fire hydrant was opened in 2018, AFFF foam 

(Chemguard 6% AFFF) was released into the environment. A company was then contracted to 

drain the AFFF tanks, dispose of the foam (off-site), repair the leak, and retrofit the tanks with 

the Ansulite 3% AFFF Mil Spec C6 foam the tank is currently equipped with. A release located 

near the fire hydrant (located west of Building 28001) would discharge to Outfall 002 via 

stormwater collector pipes. ARARNG staff verified that the hydrant water supply is isolated 

from potable water lines via backflow preventors.
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3.4 AOI 4 – BUILDING 28002

AOI 4 consists of Building 28002, an aircraft hangar located at the Robinson Army Airfield. The 

building has a fire suppression system connected to one 1,100-gal tank containing 3% AFFF of 

the brand Ansulite (AECOM 2020). 

Annual testing on the fire suppression system is performed by a contractor and involves 

equipment checks of pressure gauges. No false trips have occurred since the building 

construction and installation of the system in 2006. The AFFF tanks were serviced most recently 

in January 2019, when the contractor changed out the contents of the tank from Chemguard 6% 

AFFF C-601MS foam to Ansulite 3% AFFF Mil Spec C6 foam (AECOM 2020). 

During the PA VSI, the fire suppression system tank room was found to have an active drip leak 

of AFFF from an overhead pipe. The AFFF was pooled in the area surrounding the AFFF tank. 

However, the spillage remained contained within the room as there were no floor drains or 

cracks in the concrete floor. Repair services were requested by RMTC and the day following the 

site visit, a contractor used a suction truck to remove all the waste AFFF and capped the leaking 

pipe (AECOM 2020).

3.5 AOI 5 – WASH BAY 

AOI 5 consists of the Wash Bay, located at the Robinson Army Airfield. The building contains a 

wash rack and is reportedly the Site where all the AFFF 5-gal buckets were historically and are 

currently stored for the entire Facility. An AFFF tote weighing 2,150 pounds was also received 

from Little Rock AFB and stored temporarily in the Wash Bay. The tote was turned in unused 

shortly afterwards in August 2017 to the Defense Reutilization and Marketing Office (AECOM 

2020). 

The AASF Fire Chief estimated that approximately 210 gal of 3% AFFF have been acquired 

over time and stored either in 5-gal buckets or in ARFF vehicles. Miscellaneous 3% AFFF 

brands in small quantities were often turned into the Defense Reutilization and Marketing Office 

unused to avoid mixing different brands of AFFF together. The AFFF buckets were not known to 

have leaked or spilled in the Wash Bay and were only used to refill the ARFF vehicles at 

Building 28001 (AECOM 2020).

During the VSI, eight 5-gal buckets of Class A foam were observed in storage at the Wash Bay

building. There was no evidence of AFFF storage despite reports of current storage (AECOM 

2020).

During the teleconference conducted for the scoping of this SI on 19 February 2021, ARARNG 

personnel indicated that the building containing the Wash Bay also contains a fire suppression 

system connected to one 1,100-gal AFFF tank. The foam in this tank was replaced with Ansulite 

3% AFFF Mil Spec C6 foam in 2019 (at the same time as the other associated AASF tanks). 

On 24 January 2022, ARNG reported that a release of AFFF was discovered at AOI 5, which had 

resulted from a compressor malfunction with the 1,100-gal AFFF tank. The quantity of AFFF 

released is unknown. The release filled the tank room and leaked into the adjoining 
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warehouse/hangar, where the spill was released into the environment via the overflow pipe. The 

release extended to the northwest and northeast of AOI 5, reaching northeast and downhill across 

the adjacent dirt road. The area affected was roughly from SI sample location AOI05-01 down to 

approximately 50 yards from SI sample location RMTC-01. The release was the result of a 

compressor malfunction with the tank, as such the quantity of AFFF released is unknown since 

the contents remaining in the tank cannot be verified. A clean-up occurred 25 through 26 

January 2022, where approximately 200 cubic yards of contaminated soil were removed and 

placed into ten 20-yard environmental dumpsters (Appendix A). The soil has been accepted for 

disposal at a Subtitle C landfill. 

3.6 AOI 6 – BUILDING 70200/70201

AOI 6 consists of Building 70200/70201, the Fire Station. The CRFD occupies two buildings 

(Buildings 70200 and 70201) within the cantonment area. Various fire response vehicles are 

housed within the two buildings. According to the CRFD Fire Chief, whose tenure extends 

13 years, AFFF has never been stored within Buildings 70200 and 70201, and only Class A foam 

of the brand Chemguard was observed during the VSI. The CRFD Fire Chief stated that only 

Fire Engine 500, stationed at Building 70200, may contain AFFF within its 5-gal capacity foam 

tank, and it has not been known to leak AFFF. Neither fire training activities nor nozzle testing 

have occurred with any fire response vehicles stationed in Buildings 70200 and 70201 (AECOM 

2020).

3.7 ADJACENT SOURCES

Two potential off-facility sources of PFAS are adjacent to the Facility and are not under the 

control of the ARARNG. A description of each off-facility source is presented below and shown 

on Figure 3-1. 

3.7.1 Little Rock Air Force Base

Little Rock AFB is located approximately 4 miles east of RMTC and occupies 6,128 acres in 

Pulaski County. Operations related to the use and/or storage of AFFF have historically occurred 

at various locations in Little Rock AFB. A 2015 PFAS PA report for Little Rock AFB 

recommended 13 locations for additional PFAS investigation based on the findings of the PA 

(AECOM 2020).

The Little Rock AFB SI was conducted in 2019 (Amec Foster Wheeler Programs, Inc. 2019) and 

recommended 12 locations to undergo RIs due to exceedances of PFOS and PFOA (separately or 

combined) in groundwater or surface water. Due to the distance, groundwater flow patterns, and

the variable topography characterized by steep ridges and river valleys, it is unlikely that 

groundwater at RMTC is impacted by the storage or use of AFFF at Little Rock AFB. 

3.7.2 North Little Rock Municipal Airport

The North Little Rock Municipal Airport is located immediately east of the RMTC cantonment 

area. North Little Rock Municipal Airport personnel were not interviewed during the PA because 

the focus of the assessment was to evaluate potential PFAS-related activities and sources at 
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ARARNG properties. Therefore, it is not known if AFFF is used or stored at the airport currently 

or historically. However, because AFFF is commonly used at airports, the North Little Rock 

Municipal Airport has been identified as a potential off-site PFAS source area (AECOM 2020).

North Little Rock Municipal Airport is considered cross-gradient of RMTC. 
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Figure 3-1

Areas of Interest

<!

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<! <!<!

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Little Rock Air Force Base

North Little Rock

Municipal Airport

Range Area

1998 Airplane

Crash Area

Jim Creek

Bridge Creek

White Oak Bayou

Leopard Creek

Kellogg Creek

Little Creek

Pierce Creek

Newton Creek

Mile Creek

Miles Creek

Gap Creek

Palarm Creek

Chadwick Creek

Kellogg Creek

Spring

Creek

Arkansas River

3

0 2

Miles

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

No Suspected Release

Well Type

<!

Monitoring Well

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Perennial Creek/Stream

Intermittent Creek/Stream

Waterbody

Wetlands

AR

^_

AOI 2

All American

Landing/Drop Zone

AOI 1

Echo Pad

AOI 3

Building

28001

AOI 5

Wash Bay

AOI 4

Building

28002

0 500

Feet

0 100

Feet

AOI 6

Buildings

70200/70201

Fire Station

0 100

Feet

Army National Guard Site Inspections

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Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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4. PROJECT DATA QUALITY OBJECTIVES

As identified during the data quality objective (DQO) process and outlined in the SI Uniform 

Federal Policy- (UFP) Quality Assurance Project Plan (QAPP) Addendum (EA Engineering, 

Science, and Technology, Inc., PBC [EA] 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 AOIs for remedial investigation (RI) if site-related soil and groundwater 

samples have concentrations of the relevant compounds above the OSD risk-based screening 

levels. The SLs are presented in Section 6.1 of this report.

4.2 INFORMATION INPUTS

Primary information inputs for the SI include the following:

• The PA Report for RMTC (AECOM 2020)

• Analytical data collected during other environmental sampling efforts at RMTC

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

accordance with the site-specific UFP-QAPP Addendum (EA 2021a)

• Field data collected including groundwater elevation and water quality parameters 

measured at the time of sampling.

4.3 STUDY BOUNDARIES

The scope of the SI was bounded horizontally by the property limits of the Facility (Figures 2-1 

and 2-2). The scope of this SI was bounded vertically by the occurrence of the shallow 

groundwater, approximately 10 ft bgs. 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). Temporal 

boundaries were limited to the earliest available time field resources were available to complete 

the study.

4.4 ANALYTICAL APPROACH

Samples were analyzed by Eurofins Lancaster Laboratories Environmental, LLC, accredited 

under the Department of Defense (DoD) Environmental Laboratory Accreditation Program 

(ELAP); Accreditation No. 1.01). PFAS data underwent 100% Stage 2B validation in accordance 

with the DoD General Data Validation Guidelines (2019) and DoD Data Validation Guidelines 
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Module 3: Data Validation Procedure of Per- and Polyfluoroalkyl Substances Analysis by 

Quality Systems Manual (QSM) Table B-15 (2020).

Data were compared to applicable SLs and decision rules as defined in the UFP-QAPP 

Addendum (EA 2021a). 

4.5 DATA USABILITY ASSESSMENT

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

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

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

and qualitative methods, the assessment determines whether project execution and the resulting 

data have met installation-specific DQOs. Both sampling and analytical activities are considered 

to assess whether the collected data are of the right type, quality, and quantity to support the 

decision-making (DoD 2019a, 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 UFP-QAPP Addendum (EA2021a). 
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5. SITE INSPECTION ACTIVITIES 

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

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

implemented in accordance with the following approved documents:

• Final Preliminary Assessment Report, Robinson Maneuver Training Center, North Little 

Rock, Arkansas, dated March 2020 (AECOM 2020)

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

Inspections for Per- and Polyfluoroalkyl Substances Impacted Sites, ARNG Installations, 

Nationwide, dated December 2020 (EA 2020a)

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

Addendum, Robinson Maneuver Training Center, North little Rock, Arkansas, dated 

October 2021 (EA 2021a)

• Final Programmatic Accident Prevention Plan, Revision 1, dated November 2020 (EA 

2020b)

• Final Accident Prevention Plan / Site Safety and Health Plan Addendum, Robinson 

Maneuver Training Center, North Little Rock, Arkansas, dated August 2021 (EA 2021b). 

The SI field activities were conducted from 18 to 29 October 2021 and consisted of utility 

clearance, sonic boring soil sample collection, temporary monitoring well installation, grab 

groundwater sample collection, water level measurement, and survey. Field activities were 

conducted in accordance with the UFP-QAPP Addendum (EA 2021a), except as noted in 

Section 5.8.

The following samples were collected during the SI and analyzed for a subset of 24 compounds 

via liquid chromatography with tandem mass spectrometry (LC/MS/MS) compliant with QSM 

Version 5.3 Table B-15 to fulfill the project DQOs:

• Sixty-seven (67) soil samples from 28 locations (soil borings locations)

• Twenty-five (25) grab groundwater samples from 26 temporary well locations (one 

location was dry)

• Seven (7) field blanks (FBs)

• Fifteen (15) equipment rinsate samples

• Nine (9) field duplicate (FD) samples.

Figures 5-1 through 5-3 provide 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 
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in Appendix C. A log of Daily Notice of Field Activity was completed throughout the SI field 

activities, which is provided in Appendix C1. Completed sample forms, survey data, and a field 

change request form are included as Appendices C2 through C4, respectively. Additionally, a 

photographic log of field activities is provided in Appendix D. 

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 of these activities are presented below. 

5.1.1 Technical Project Planning

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

(Department of Army 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 26 August 2021, prior to SI field activities. 

Meeting minutes are provided in Appendix E. The combined TPP Meeting 1 and 2 was 

conducted in general accordance with EM 200-1-2. 

The stakeholders for this SI include ARARNG, ARNG, USACE, and Arkansas Division of 

Environmental Quality representatives familiar with the Facility, the regulations, and the 

community. Stakeholders were provided the opportunity to make comments on the technical 

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

combined TPP Meeting 1 and 2 was memorialized in the UFP-QAPP Addendum (EA 2021a). 

Future TPP meetings will provide an opportunity to discuss results and findings, and future 

actions, where warranted. 

5.1.2 Utility Clearance

On 30 September 2021, a dig permit request was made to RMTC. Proposed drilling locations 

were provided in a coordinate table and on maps. The proposed work areas were delineated with 

white pin flags. Utility locations within the proposed work areas were marked by utility 

providers and RMTC personnel.

On 18 October 2021, RMTC personnel met with members of the EA field team to identify 

marked utility locations where some uncertainty existed and to ensure that markings were still in 

place. On the east side of the Fire Station at AOI 2, some locations were adjusted based on 

RMTC personnel recommendations in order to avoid a high voltage power line that was installed 

by directional drilling at a depth greater than 5 ft. Based on the utility locate results, and refusal 

during drilling, some of the proposed sample locations were moved. When samples were moved, 

RMTC personnel were notified, and they supported clearance for sample relocation activities.

Additionally, during the SI the first 5 ft of each boring were pre-cleared by EA’s drilling 
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subcontractor, using a hand auger, to verify utility clearance in shallow subsurface where utilities 

were expected to be encountered. 

5.1.3 Source Water and PFAS Sampling Equipment Acceptability

Samples collected from the potable water sources used for drilling equipment decontamination 

were analyzed and it was confirmed that PFAS concentrations were below the limit of 

quantitation (LOQ) and deemed acceptable prior to the start of field activities. Samples collected

from the potable water sources at the Fire Station (FH-02) and Building 28002 (EP-01) on 

16 September 2021, prior to mobilization, were analyzed for PFAS by LC/MS/MS compliant

with QSM 5.3 Table B-15. The sample data met acceptance criteria presented in the UFP-QAPP 

Addendum for the water source to be used for decontamination of drilling equipment (EA 

2021a). A discussion of the results is presented in Appendix B. The analytical results are 

presented in Appendix F.

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

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

environment was provided in the Standard Operating Procedures, Appendix B, to the

Programmatic UFP-QAPP (EA 2020a). 

5.2 SOIL BORINGS AND SOIL SAMPLING

All soil sample locations are shown on Figures 5-1 through 5-3, and boring sample depths are 

provided in Table 5-1. The boring locations were selected based on information provided in the 

PA (AECOM 2020) and as agreed upon by stakeholders during the TPP and review of the UFPQAPP Addendum (EA 2021a). Non-dedicated sampling equipment (e.g., hand auger) was 

decontaminated between sampling locations. 

Soil borings were drilled with a Geoprobe® 8150LS sonic drilling rig. A dual-tube sampling 

system was used to collect continuous soil cores to target depths. A hand auger was used to 

collect soil from the top 0 to 5 ft of the boring in compliance with utility clearance procedures.

Due to refusal at some locations hand auguring stopped before the 5-ft mark.

Given the expected shallow groundwater depth, two discrete soil samples were planned to be 

collected for chemical analysis from each soil boring: one sample from the surface interval (0 to 

2 ft bgs) and one subsurface soil sample from approximately 1 ft above the groundwater table in 

accordance with the UFP-QAPP Addendum (EA 2021a). Only one soil sample was collected 

from one location, AOI06-01, due to shallow rock being encountered at less than 6 ft bgs. 

Additionally, three soil samples were collected from 12 locations where groundwater was 

encountered deeper than expected. At locations where three samples were collected one surface 

soil and two subsurface soil samples were collected. Subsurface soil samples were collected at 

the mid-point between the surface and the groundwater table (not to exceed 15 ft bgs) and 

approximately 1 ft above the groundwater table.
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Groundwater was encountered at depths ranging from 0.2 to 18.8 ft bgs during drilling. Total 

boring completion depths, to accommodate temporary well installation, ranged from 4.5 to 

20.0 ft bgs. One surface soil sample (0 to 2 ft bgs) was collected at each boring location. 

After submittal of the Final UFP-QAPP Addendum, during utility clearance and sampling, some 

locations were moved due to utilities 

or refusals. Changes were detailed in a Field Change Request Form that was executed on 

22 October 2021 (Appendix C4). The changes are discussed in Section 5.8 as deviations from 

the UFP-QAPP Addendum.

During the drilling, the soil cores were continuously logged for lithological descriptions by a 

field geologist using the Unified Soil Classification System. A photoionization detector (PID) 

was used to screen the breathing zone during boring activities as a part of personal safety 

requirements and to screen the continuous cores. Observations and measurements were recorded 

on sampling forms (Appendix C2) and in a non-treated field logbook. Depth interval, recovery 

thickness, PID concentrations, moisture, relative density, Munsell color, and Unified Soil 

Classification System texture were recorded. The boring logs are provided in Appendix G. 

Each sample was placed into a laboratory-supplied PFAS-free HDPE bottle and labeled using a 

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

standard chain-of-custody procedures to the laboratory and analyzed for PFAS (LC/MS/MS 

compliant with QSM Version 5.3 Table B-15), total organic compound (TOC) (USEPA Method 

9060A) and pH (USEPA Method 9045D) in accordance with the UFP-QAPP Addendum (EA 

2021a). 

FD samples were collected at a rate of 10% and analyzed for the same parameters as the 

accompanying samples. Matrix spike (MS)/matrix spike 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 blanks (EBs) were collected at a rate of one per day per medium and 

analyzed for the same parameters as the samples. A temperature blank was placed in each cooler 

to ensure that samples were preserved at or below 6 degrees Celsius (°C) during shipment. 

Borings were converted to temporary wells, which were subsequently abandoned after sampling, 

water level measuring, and surveying in accordance with the UFP-QAPP Addendum (EA 

2021a). After removal of the casings, boreholes were abandoned using bentonite chips. Borings 

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

5.3 TEMPORARY WELL INSTALLATION AND GROUNDWATER GRAB 

SAMPLING

Temporary wells were bored using a GeoProbe® 8150LS sonic drill rig. Once the borehole was 

advanced to the desired depth, a temporary well was constructed with 5- and/or 10-ft sections of 

1-inch Schedule 40 polyvinyl chloride (PVC) screen and casing. New PVC pipe and screen were 

used at each location to avoid cross-contamination between locations. The screened intervals for 

the temporary wells are provided in Table 5-2.
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Groundwater samples were collected using a peristaltic pump with PFAS-free HDPE tubing. 

Samples were collected after a period of time following well installation to allow groundwater to 

infiltrate and recharge the temporary well intervals. Each sample was collected in laboratorysupplied PFAS-free HDPE bottles and labeled using a PFAS-free marker or pen. 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, and oxidation-reduction potential) were measured using a water quality meter and 

recorded on the field sampling form (Appendix C2) before each grab sample was collected in a 

separate container. Samples were packaged on ice and transported via FedEx under standard 

chain-of-custody procedures to the laboratory and analyzed by LC/MS/MS compliant with QSM 

Version 5.3 Table B-15 in accordance with the UFP-QAPP Addendum (EA 2021a).

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. With the exception of sample 

RMTC-03, no foaming was noted in any of the groundwater samples.

FD 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. Seven FBs were collected in accordance with the 

UFP-QAPP Addendum (EA 2021a). A temperature blank was placed in each cooler to ensure 

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

The temporary wells were surveyed by a licensed surveyor prior to collecting final water levels. 

When each well top of casing was surveyed, the weight of the stadia rod pushed the well casing 

down an estimated 1-3 hundredths of a foot. This resulted in measurements collected during 

sampling being off slightly relative to the final measured water level elevations in some wells.

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

accordance with the SI UFP-QAPP Addendum (EA 2021a) by removing the PVC and 

backfilling the hole with bentonite chips. Upon completion of well abandonment, the ground 

surface at each location was patched to match existing surrounding conditions.

5.4 SYNOPTIC WATER LEVEL MEASUREMENTS

Groundwater levels were used to monitor facility-wide groundwater elevations and assess 

groundwater flow. Synoptic water level elevation measurements were collected from the newly 

installed temporary monitoring wells, taken from the survey mark on the northern side of the 

well casing on 29 October 2021. Groundwater flow contour maps are provided in Figures 2-4, 2-

5 and 2-6. Groundwater elevation data are provided in Table 5-3. 

5.5 SURVEYING

The northern side of each new temporary well casing was surveyed prior to abandonment. 

Horizontal positions of temporary wells at AOIs 2 and 6 were surveyed with a Sokkia Set 30R 

total station (transit) and all other locations were surveyed using a Trimble GNSS R10-2 global 

positioning system receiver. All vertical elevations were found with a Leica DNA03 Level. 

Positions were collected in the applicable Universal Transverse Mercator zone projection with 

World Geodetic System 1984 datum (horizontal) and North American Vertical Datum 1988 
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(vertical). Surveying data for AOIs 2 and 6 were collected on 21 October 2021 and surveying 

data for AOIs 1, 3, 4, and 5 were collected on 28 October 2021. Due to the weight of the stadia 

rod, it was noted that some well casings had settled after sample collection but before final water 

level elevations were measured. There was no effect on final groundwater elevation data, but 

elevations recorded during groundwater sampling may not be of survey accuracy. Surveying data 

are provided in Appendix C3. 

5.6 INVESTIGATION-DERIVED WASTE

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

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

managed in accordance with the UFP-QAPP Addendum (EA 2021a). 

Soil IDW (i.e., soil cuttings) and liquid IDW (i.e., purge water, development water, and 

decontamination fluids) generated during the SI activities were drummed (16 total) and staged in 

an approved area. 

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

monitoring well construction materials, and other disposable material used during the field 

activities were disposed of at a licensed solid waste landfill.

5.7 LABORATORY ANALYTICAL METHODS

Samples were analyzed for relevant compounds by LC/MS/MS compliant with QSM Version 5.3 

Table B-15 at Eurofins Lancaster Laboratories Environmental, LLC, in Lancaster, Pennsylvania, 

a DoD ELAP-certified laboratory. 

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

Method 9045D.

Due to the turbidity many of the samples were centrifuged and decanted prior to analysis.

5.8 DEVIATIONS FROM SITE INVESTIGATION UFP-QAPP ADDENDUM

Deviations from the UFP-QAPP Addendum occurred based on conditions encountered during 

the field investigation activities. These deviations were discussed between EA, ARNG, and 

USACE. Deviations from the UFP-QAPP Addendum are noted below: 

• Sample locations AOI06-01, AOI06-03, AOI06-04, AOI01-05, AOI05-02, AOI05-03, 

and AOI03-03 required relocation due to the presence of subsurface utilities. All sample 

locations were moved to a safe distance from known and marked subsurface utilities, 

downgradient from their original locations (with the exception of AOI06-01, which was 

moved further upgradient from its original location). A Field Change Request Form 

(Appendix C4) was submitted for sample locations AOI06-01 and AOI06-03.
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• In addition to the relocations prior to drilling, locations AOI06-01 and AOI06-04 were 

offset at the time of drilling due to penetrating a confining layer into dry sand at location 

AOI06-01 and in order to avoid penetrating a confining layer at location AOI06-04. As a 

result, a second boring was installed downgradient of the previous sample location: 

AOI06-01-Off and AOI06-04-Off. A surface soil sample was collected from AOI06-01, 

and the subsequent sample (2–3 ft bgs) was taken in the new location AOI06-01-Off. A 

surface soil sample and subsurface soil sample (10 –11 ft bgs) were taken from AOI06-04 

and two additional subsurface samples (7–8 and 17–18 ft bgs) were collected from 

AOI-06-04-Off. Temporary wells were installed at these new locations. 

• Borings from 20 locations (AOI01-01, AOI01-04, AOI01-07, AOI02-01, AOI02-02, 

AOI02-03, AOI02-04, AOI03-01, AOI03-02, AOI04-01, AOI04-02, AOI05-01, AOI05-

02, AOI05-03, AOI06-02, AOI06-03, AOI06-04, AOI06-04-Off, RMTC-01, and RMTC02) were advanced deeper than 10 ft bgs, as written in the UFP-QAPP Addendum 

(EA 2021a) due to the depth groundwater was encountered. Maximum boring depth 

reached 20 ft bgs. Three discrete soil samples were collected from each of these locations 

following ARNG PFAS SI protocols implemented at other PFAS sites, which is a 

deviation from the UFP-QAPP which identified two sampling intervals from each 

location. 

• No groundwater sample was taken from AOI05-01 due to the lack of shallow 

groundwater at the well location. 

• Purging volume/length requirements outlined in the UFP-QAPP Addendum (EA 2021a) 

were not met at well locations AOI03-01, RMTC-01, AOI02-01, AOI02-02, and 

AOI02-03 due to the wells purging dry. Samples at these locations were taken after the 

wells sufficiently recharged. 

• The temporary well riser did not meet or exceed the ground surface at locations AOI01-

01, AOI01-02, AOI01-05, AOI01-07, AOI02-01, AOI03-01, AOI03-02, AOI03 03, 

AOI04-01, AOI04-02, AOI06-02, AOI06-03, RMTC-01, RMTC-02, and RMTC-03 due 

to settling that occurred after each well was installed, but prior to measuring final 

groundwater levels. Temporary well riser was cut to be roughly level with the surface at 

each location during installation to reduce hazards to aircraft. In accordance with the 

UFP-QAPP, temporary wells within boreholes were not fully immobilized. During 

surveying, when the stadia rod was placed on each riser, field staff noticed that the 

weight displaced some of the temporary well risers slightly. The maximum vertical 

separation between the ground surface and top of casing was 0.28 ft, measured in 

AOI04-01. Final water levels used for potentiometric surface maps were measured after 

surveying was complete in order to ensure accurate water level measurements. 

• In order to increase the likelihood of being able to collect water samples a 10-ft screen 

was used at some locations. Ten (10) ft of screen was installed at locations AOI01-01, 

AOI01-04, AOI01-07, AOI02-02, AOI02-03, AOI02-04, AOI03-02, RMTC-01, and 

RMTC-02. Due to the low yielding aquifer, determining the water level during drilling

was difficult. 
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• The UFP-QAPP Addendum (EA 2021a) outlined that one pH/TOC sample would be 

collected from each AOI; however, the chain-of-custody submitted at the time of 

sampling did not clearly specify pH/TOC for all six samples. Only one sample, from AOI 

6, was initially analyzed for pH/TOC. This inconsistency was noted after receipt of the 

initial data package and was resolved by having the laboratory run the pH/TOC analysis 

on the remaining soil sample material from AOIs 1, 2, 3, and 5.3 This analysis occurred 

after the pH/TOC prep/analysis holding time outlined in the UFP-QAPP Addendum were 

exceeded; however, the data as reported is still considered usable and does not affect the 

conclusions of the SI.

Table 5-1. Samples by Medium

RMTC, North Little Rock, Arkansas

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Sample Identification

Sample 

Collection 

Date

Sample 

Depth

(ft bgs)

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

Comments

Soil Samples

AOI01-01-SB-0-2 10/27/2021 0-2 X

AOI01-01-SB-0-2-DUP 10/27/2021 0-2 X FD

AOI01-01-SB-5-6 10/27/2021 5-6 X

AOI01-01-SB-7-8 10/27/2021 7-8 Grain Size 

AOI01-01-SB-10-11 10/27/2021 10-11 X

AOI01-02-SB-0-2 10/27/2021 0-2 X

AOI01-02-SB-3-4 10/27/2021 3-4 X X X

AOI01-03-SB-0-2 10/28/2021 0-2 X

AOI01-03-SB-2-3 10/28/2021 2-3 X

AOI01-03-SB-2-3-DUP 10/28/2021 2-3 X FD

AOI01-04-SB-0-2 10/28/2021 0-2 X

AOI01-04-SB-3-4 10/28/2021 3-4 X

AOI01-04-SB-8-9 10/28/2021 8-9 X

AOI01-05-SB-0-2 10/28/2021 0-2 X

AOI01-05-SB-2-3 10/28/2021 2-3 X

AOI01-06-SB-0-2 10/28/2021 0-2 X

AOI01-06-SB-0-2-DUP 10/28/2021 0-2 X FD

AOI01-06-SB-2-3 10/28/2021 2-3 X

AOI01-07-SB-0-2 10/27/2021 0-2 X

3 For four of the five AOIs, adequate material was available. At AOI 4, there was not enough material to run pH or 

TOC analysis. AOIs 3, 4, and 5 are all essentially different buildings in the same area/geology; therefore, soil pH 

and TOC samples collected at AOIs 3 and 5 are assumed to be representative of conditions at AOI 4.
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Table 5-1. Samples by Medium

RMTC, North Little Rock, Arkansas

Site Inspection Report

Sample Identification

Sample 

Collection 

Date

Sample 

Depth

(ft bgs)

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

Comments

AOI01-07-SB-4.5-5.5 10/27/2021 4.5-5.5 X

AOI01-07-SB-9-10 10/27/2021 9-10 X

AOI02-01-SB-0-2 10/19/2021 0-2 X

AOI02-01-SB-6-7 10/19/2021 6-7 X

AOI02-02-SB-0-2 10/18/2021 0-2 X

AOI02-02-SB-8-9 10/19/2021 8-9 X

AOI02-02-SB-13-14 10/19/2021 13-14 X

AOI02-03-SB-0-2 10/19/2021 0-2 X

AOI02-03-SB-3-4 10/19/2021 3-4 X

AOI02-03-SB-5-6 10/21/2021 5-6 X

AOI02-03-SB-10-11 10/19/2021 10-11 X

AOI02-04-SB-0-2 10/18/2021 0-2 X X X

AOI02-04-SB-6-7 10/18/2021 6-7 X

AOI02-04-SB-6-7-DUP 10/18/2021 6-7 X FD

AOI02-04-SB-10-12 10/18/2021 10-12 Grain Size

AOI03-01-SB-02 10/21/2021 0-2 X

AOI03-01-SB-8-9 10/21/2021 8-9 X

AOI03-02-SB-0-2 10/21/2021 0-2 X

AOI03-02-SB-5-6 10/21/2021 5-6 Grain Size

AOI03-03-SB-0-2 10/21/2021 0-2 X

AOI03-03-SB-2-3 10/21/2021 2-3 X X X

AOI04-01-SB-0-2 10/21/2021 0-2 X

AOI04-01-SB-7-8 10/21/2021 7-8 X

AOI04-01-SB-15-16 10/21/2021 15-16 X

AOI04-02-SB-0-2 10/21/2021 0-2 X

AOI04-02-SB-7-8 10/21/2021 7-8 X

AOI05-01-SB-0-2 10/22/2021 0-2 X

AOI05-01-SB-13 10/22/2021 12.5-13.5 X

AOI05-02-SB-0-2 10/26/2021 0-2 X X X

AOI05-02-SB-6-7 10/26/2021 6-7 X

AOI05-02-SB-7-8 10/26/2021 7-8 Grain Size

AOI05-02-SB-11-12 10/26/2021 11-12 X

AOI05-02-SB-18-18.5 10/28/2021 18-18.5 X
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Table 5-1. Samples by Medium

RMTC, North Little Rock, Arkansas

Site Inspection Report

Sample Identification

Sample 

Collection 

Date

Sample 

Depth

(ft bgs)

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

Comments

AOI05-03-SB-0-2 10/26/2021 0-2 X

AOI05-03-SB-0-2-DUP 10/26/2021 0-2 X FD

AOI05-03-SB-7-8 10/26/2021 7-8 X

AOI05-03-SB-15-16 10/26/2021 15-16 X

AOI06-01-SB-0-2 10/20/2021 0-2 X

AOI06-01-OFF-SB-2-3 10/20/2021 2-3 X

AOI06-01-OFF-SB-2-3-DUP 10/20/2021 2-3 X FD

AOI06-02-SB-0-2 10/20/2021 0-2 X

AOI06-02-SB-7-8 10/20/2021 7-8 X

AOI06-02-SB-16-17 10/20/2021 16-17 X

AOI06-03-SB-0-2 10/20/2021 0-2 X

AOI06-03-SB-7.5-8.5 10/20/2021 7.5-8.5 X

AOI06-03-SB-17.5-18.5 10/20/2021 17.5-18.5 X

AOI06-04-SB-0-2 10/20/2021 0-2 X X X

AOI06-04-SB-10-11 10/20/2021 10-11 X

AOI06-04-OFF-SB-7-8 10/20/2021 7-8 X

AOI06-04-OFF-SB-17-18 10/20/2021 17-18 X

RMTC-01-OFF-SB-0-2 10/25/2021 0-2 X

RMTC-01-OFF-SB-6-7 10/26/2021 6-7 X

RMTC-01-OFF-SB-12-13 10/26/2021 12-13 X

RMTC-02-SB-0-2 10/27/2021 0-2 X

RMTC-02-SB-4-5 10/27/2021 4-5 X

RMTC-02-SB-9-10 10/27/2021 9-10 X

RMTC-03-SB-0-2 10/22/2021 0-2 X

RMTC-03-SB-4-5 10/22/2021 4-5 X

Groundwater Samples

AOI01-01-GW 10/28/2021 - X

AOI01-01-GW-DUP 10/28/2021 - X FD

AOI01-02-GW 10/28/2021 - X

AOI01-03-GW 10/28/2021 - X

AOI01-04-GW 10/29/2021 - X

AOI01-05-GW 10/28/2021 - X

AOI01-06-GW 10/28/2021 - X
Site Inspection Report

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Table 5-1. Samples by Medium

RMTC, North Little Rock, Arkansas

Site Inspection Report

Sample Identification

Sample 

Collection 

Date

Sample 

Depth

(ft bgs)

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

Comments

AOI01-07-GW 10/28/2021 - X

AOI02-01-GW 10/26/2021 - X

AOI02-02-GW 10/26/2021 - X

AOI02-03-GW 10/29/2021 - X

AOI02-04-GW 10/19/2021 - X

AOI03-01-GW 10/25/2021 - X

AOI03-02-GW 10/25/2021 - X

AOI03-02-GW-DUP 10/25/2021 - X FD

AOI03-03-GW 10/25/2021 - X

AOI04-01-GW 10/25/2021 - X

AOI04-02-GW 1025/2021 - X

AOI05-02-GW 10/29/2021 - X

AOI05-03-GW 10/27/2021 - X

AOI06-01-GW 10/22/2021 - X

AOI06-02-GW 10/22/2021 - X

AOI06-03-GW 10/21/2021 - X

AOI06-03-GW-DUP 10/21/2021 - X FD

AOI06-04-GW 10/22/2021 - X

RMTC-01-GW 10/27/2021 - X

RMTC-02-GW 10/27/2021 - X

RMTC-03-GW 10/26/2021 - X

Blank Samples

FB-01-102121 10/21/2021 - X FB

FB-2-102221 10/22/2021 - X FB

FB-3-GW-102521 10/25/2021 - X FB

FB-4-GW-102621 10/26/2021 - X FB

FB-5-GW-102721 10/27/2021 - X FB

FB-6-GW-102821 10/28/2021 - X FB

FB-7-GW102921 10/29/2021 - X FB

EB-1-GW-101821 10/19/2021 - X EB

EB-1-Soil-101821 10/19/2021 - X EB

EB-2-GW-101921 10/20/2021 - X EB

EB-2-Soil-101921 10/20/2021 - X EB
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Table 5-1. Samples by Medium

RMTC, North Little Rock, Arkansas

Site Inspection Report

Sample Identification

Sample 

Collection 

Date

Sample 

Depth

(ft bgs)

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

Comments

EB-3-GW-10202021 10/20/2021 - X EB

EB-3-Soil-10202021 10/20/2021 - X EB

EB-04-GW-102121 10/21/2021 - X EB

EB-4-Soil-102121 10/21/2021 - X EB

EB-5-GW-102221 10/22/2021 - X EB

EB-5-Soil-102221 10/22/2021 - X EB

EB-6-GW-102521 10/25/2021 - X EB

EB-6-Soil-102721 10/27/2021 - X EB

EB-7-GW-102621 10/26/2021 - X EB

EB-8-GW-102721 10/27/2021 - X EB

EB-9-GW-102921 10/29/2021 - X EB

Source Water Samples

EP-01 9/16/2021 - X

FH-02 9/16/2021 - X
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Table 5-2. Soil Boring Depths and Temporary Well Screen Intervals

RMTC, North Little Rock, Arkansas

Site Inspection Report

Areas of Interest Boring ID

Soil Boring Depth

(ft bgs)

Temporary Well 

Screen Interval

(ft bgs)

1

AOI01-01 20.0 10-20

AOI01-02 7.0 2-7

AOI01-03 9.0 4-9

AOI01-04 20.0 10-20

AOI01-05 7.5 2.5-7.5

AOI01-06 10.0 5-10

AOI01-07 14.5 4.5-14.5

2

AOI02-01 13.0 7-12

AOI02-02 19.0 9-19

AOI02-03 12.0 2-12

AOI02-04 15.0 5-15

3

AOI03-01 11.25 6.25-11.25

AOI03-02 15.0 5-15

AOI03-03 6.5 1.5-6.5

4

AOI04-01 18.0 13-18

AOI04-02 13.0 8-13

5

AOI05-01 20.0 15-20

AOI05-02 20.0 15-20

AOI05-03 20.0 15-20

6

AOI06-01* 7.0 NA

AOI06-01-Off 4.5 1-4.5

AOI06-02 20.0 15-20

AOI06-03 19.0 14-19

AOI06-04* 11.5 NA

AOI06-04-Off 20.0 15-20

Robinson Army Airfield

RMTC-01 18.5 8.5-18.5

RMTC-02 14.0 4-14

RMTC-03 10.0 5-10

Notes:

*Hit refusal prior to groundwater, boring was offset.

NA = Not applicable
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Table 5-3. Groundwater Elevation

RMTC, North Little Rock, Arkansas

Site Inspection Report

Monitoring 

Well ID

Top of Casing 

Elevation (ft amsl)

Ground Surface 

Elevation (ft amsl)

Depth to Water

(ft btoc)

Groundwater Elevation

(ft amsl)

AOI01-01 570.71 570.87 11.28 559.43

AOI01-02 580.85 581.12 1.41 579.44

AOI01-03 581.90 581.79 1.02 580.88

AOI01-04 586.56 586.28 17.11 569.45

AOI01-05 588.15 588.16 0.20 587.95

AOI01-06 586.18 586.05 0.80 585.38

AOI01-07 585.71 585.72 0.40 585.31

AOI02-01 371.15 371.25 11.00 360.15

AOI02-02 371.72 371.62 14.59 357.13

AOI02-03 371.80 371.65 11.19 360.61

AOI02-04 374.09 373.96 6.04 368.05

AOI03-01 589.67 589.85 8.87 580.80

AOI03-02 589.82 590.23 7.92 581.90

AOI03-03 587.88 587.97 1.28 586.60

AOI04-01 588.88 589.16 6.27 582.61

AOI04-02 591.78 591.84 1.49 590.29

AOI05-01 588.68 588.55 DRY NA

AOI05-02 589.34 589.23 18.80 570.54

AOI05-03 583.80 583.74 17.62 566.18

AOI06-01-Off 518.54 518.48 1.97 516.57

AOI06-02 522.16 522.26 13.49 508.67

AOI06-03 514.01 514.03 3.24 510.77

AOI06-04-Off 516.73 516.54 5.79 510.94

RMTC-01 576.06 576.31 11.72 564.34

RMTC-02 580.44 580.64 6.27 574.17

RMTC-03 584.74 584.80 4.56 580.18

Notes: 

btoc = Below top of casing

NA = Not applicable
Figure 5-1

AOI 1, AOI 3, AOI 4 and AOI 5

Site Inspection Sample Locations

!(

!(

!(

!(

!(

!(

!( !(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

*#

*#

*#

*#

*#

Outfall 004

Outfall 003

Outfall 002

Outfall 001

Outfall 005

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

AOI05-01

AOI 1

AOI 3 Echo Pad

Building

28001

AOI 5

Wash Bay

AOI 4

Building

28002

3

0 500

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Sample Locations

!( Sonic Boring

Hydrology/Hydrogeology

*# Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

Map Extent

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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This page intentionally left blank
Figure 5-2

AOI 2

Site Inspection Sample Locations

!(

!(

!(

!(

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI 2

All American

Landing/Drop Zone

3

0 200

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Sample Locations

!( Sonic Boring

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

Map Extent

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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This page intentionally left blank
Figure 5-3

AOI 6

Site Inspection Sample Locations

!(

!(

!(

!(

!(

!(

AOI06-04

AOI06-03

AOI06-02

AOI06-01

AOI06-01-Off

AOI06-04-Off

AOI 6

Buildings

70200/70201

Fire Station

3

0 100

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Sample Locations

!( Sonic Boring

Hydrogeology

Groundwater Flow Direction

Map Extent

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
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Site Inspection Report

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6. SITE INSPECTION RESULTS

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

presented in Section 6.1. A discussion of the results for the AOIs is provided in Sections 6.3 

through 6.8. Tables 6-2 through 6-5 present results for 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 H.

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 AOI concentration for sampled media exceed the 

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

CERCLA. The SLs established in the OSD memorandum apply to the five compounds presented 

on Table 6-1. 

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

Analyte1,2

Residential

(Soil)

(μg/kg)1

0 to 2 ft bgs

Industrial/Commercial

Composite Worker

(Soil)

(μg/kg) 1

2 to 15 ft bgs

Tap Water

(Groundwater)

(ng/L) 1

PFOA 19 250 6

PFOS 13 160 4

PFBS 1,900 25,000 601

PFHxS 130 1,600 39

PFNA 19 250 6

Notes:

1. Assistant Secretary of Defense. 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’s 

Regional Screening Level Calculator. Hazard Quotient=0.1. 6 July 2022. 

2. 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.

g/kg = Microgram(s) per kilogram

ng/L = Nanogram(s) per liter

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

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

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

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

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

results (2 to 15 ft bgs). The SLs are not applied to deep subsurface soil results (greater than 15 ft 

bgs) because 15 ft is the anticipated limit of construction activities.
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6.2 SOIL PHYSICOCHEMICAL ANALYSES

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

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

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

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

appropriate, to assess fate and transport of PFAS contaminants. According to the Interstate 

Technology Regulatory Council (ITRC), several important PFAS partitioning mechanisms 

include hydrophobic and lipophobic effects, electrostatic interactions, and interfacial behaviors. 

At relevant environmental pH values, certain PFAS are present as organic anions’ and are 

therefore, relatively mobile in groundwater (Xiao et al. 2015) but tend to associate with the 

organic carbon fraction that may be present in soil or sediment (Higgins and Luthy 2006; Guelfo 

and Higgins 2013). When sufficient organic carbon is present, organic carbon normalized 

distribution coefficients (Koc values) can help in evaluating transport potential, though other 

geochemical factors (i.e., pH and presence of polyvalent cations) may also affect PFAS sorption 

to solid phases (ITRC 2018).

Soil pH was measured as 5.6 in samples collected from AOIs 1, 2, 5, and 6. Soil pH was 

measured as 7.7 in a sample collected from AOI 3. TOC ranged from a low of 730 H milligrams 

per kilogram (mg/kg) in the sample collected from AOI 1 to a high of 14,000 mg/kg in the 

sample collected from AOI 6. 

Grain sizes were analyzed from samples collected from AOI01-01, AOI02-04, AOI03-02, and 

AOI05-02 and compared with United Soil Classification grain size ranges. The combined silt 

and clay content ranged from 43.5% to 78.6% in samples AOI01-01 and AOI05-02, respectively. 

The content of sand grain size ranged from 19.8% to 42.6% in samples AOI05-02 and AOI02-

04, respectively. Gravel sized grain size ranged from 0% to 25.6% in samples collected from 

AOI03-02 and AOI01-01, respectively.

6.3 AOI 1 

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

AOI 1 - Echo Pad. The soil and groundwater results are summarized on Tables 6-2 through 6-5. 

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

6.3.1 AOI 1 – Soil Analytical Results

Figure 6-1 through 6-5 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the detected compounds in soil.

Soil was sampled in 7 boring locations in AOI 1. Soil was sampled from three intervals at 

locations AOI01-01, AOI01-04, and AOI01-07 and from two intervals at locations AOI01-02, 

AOI01-03, AOI01-05, and AOI01-06.
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Soil was sampled from surface soil (0 to 2 ft bgs) from AOI01-01 through AOI01-07. There 

were no detections of PFOA, PFOS, PFHxS, PFNA, or PFBS at boring location AOI01-01. 

PFOA was detected below the SL in AOI01-02 through AOI01-07 and ranged from 0.22 J g/kg 

to 6.2 g/kg at boring locations AOI01-05 and AOI01-02, respectively. PFOS was detected 

above the SL in samples collected from boring locations AOI01-02 and AOI01-07 at 

concentrations of 44 g/kg and 190 g/kg, respectively. PFHxS was detected below the SL in 

samples collected from boring locations AOI01-02 through AOI01-07 at concentrations ranging 

from 0.25 J g/kg to 12 g/kg at boring locations AOI01-04 and AOI01-07, respectively. PFHxS 

was only detected in the duplicate sample for AOI01-06 and not the primary surface soil sample 

from location AOI01-06. PFNA was detected in excess of the SL at a concentration of 20 g/kg 

from soil boring location AOI01-02. PFNA was detected at concentrations below the SL in 

samples collected from boring locations AOI01-03, AOI01-04, AOI01-06, and AOI01-07. 

PFNA was not detected at locations AOI01-01 or AOI01-05. PFBS was detected at boring 

location AOI01-07, with a concentration of 1.1 J g/kg, which is below the SL. PFBS was not 

detected in samples collected at the remaining surface soil locations.

Shallow subsurface soils were collected from soil boring locations AOI01-01 through AOI01-07

at depths ranging from 2 to 6 ft bgs. PFOA was detected below the SL in samples collected from 

four soil boring locations ranging from 0.24 J g/kg at AOI01-06 to 3.1 g/kg at location 

AOI01-02. PFOS was detected at concentrations below the SL in samples collected from 5 of 7 

soil boring locations, ranging from 0.49 J g/kg at soil boring location AOI01-03 to 7.1 g/kg at 

soil boring location AOI01-02. PFHxS was detected below the SL in samples collected from 

three locations and ranged from 0.22 J to 1.4 g/kg at AOI01-04 and AOI01-02, respectively. 

PFNA was only detected in the sample collected from AOI01-02 at a concentration of 2.5 g/kg, 

but the concentration was below the SL. PFBS was not detected in samples collected from any of 

the soil boring locations.

PFOS, PFOA, PFNA, and PFBS were not detected in samples collected from deep subsurface 

soils, ranging from 8 to 18.5 ft bgs. PFHxS was detected below the SL at 0.84 g/kg in the 

sample collected from AOI01-07. PFHxS was not detected in the other deep subsurface samples.

6.3.2 AOI 1 – Groundwater Analytical Results 

Figures 6-6 and 6-7 present the ranges of detections in groundwater. Table 6-5 summarizes the 

groundwater results.

Groundwater samples were collected from 7 temporary wells at AOI 1 during the SI activities. A 

duplicate sample was also collected from one of the wells for a total of eight groundwater 

samples. PFOS, PFOA, PFHxS, PFNA, and PFBS were detected in groundwater samples 

collected from all of the locations in AOI 1. PFOS concentrations in all samples collected from 

AOI 1 exceeded the SL and ranged from a low of 14 ng/L in the sample collected from AOI01-

04 to a high of 3,000 J+ ng/L in the sample collected from AOI01-02. PFOA concentrations 

from 7 samples collected from AOI 1 exceeded the SL and ranged from 6.4 ng/L to 540 ng/L in 

samples collected from AOI01-01 and AOI01-02, respectively. PFOA concentrations in the 

AOI01-01 primary sample (5.2 ng/L) did not exceed the SL; however, the duplicate sample 

collected from this location exceeded the SL with a value of 6.4 ng/L. PFHxS was detected in all 
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samples collected from AOI 1 and PFHxS exceeded the SL in samples collected from six 

locations AOI01-02 through AOI01-07. Concentrations exceeding the SL ranged from a low of 

55 ng/L in AOI01-05 to a maximum concentration of 1,000 ng/L in AOI01-07. PFNA was 

detected in all groundwater samples collected from AOI 1 and exceeded the SL in samples 

collected from five locations AOI01-02 through AOI01-04, AOI01-06, and AOI01-07. 

Concentrations exceeding the SL ranged from a low of 11 ng/L in AOI01-04 to a maximum of 

770 J+ ng/L in AOI01-02. PFBS concentrations did not exceed the SL in any samples collected

from AOI 1. PFBS concentrations ranged from 3.3 ng/L in a sample collected from temporary 

well AOI01-01 to 190 ng/L in the sample collected from temporary well AOI01-07.

6.3.3 AOI 1 – Conclusions

Based on the results of the SI, PFOS and PFNA were detected in soil at concentration above their 

respective SLs. PFOA, PFOS, PFNA, and PFHxS were detected in groundwater at 

concentrations above their respective SLs. Based on the exceedances of the SLs in soils and 

groundwater, further evaluation at AOI 1 is warranted.

6.4 AOI 2 

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

AOI 2 - All American Landing/Drop Zone. The detected compounds are summarized in Tables

6-2 through 6-5. Soil and groundwater results are presented on Figures 6-8 through 6-14.

6.4.1 AOI 2 – Soil Analytical Results

Figures 6-8 through 6-12 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the detected compounds in soil.

Soil was sampled in four boring locations at AOI 2. Soil was sampled from three intervals at 

locations AOI02-02 and AOI02-03 and from two intervals at locations AOI02-01 and AOI02-04.

PFOS and PFHxS were detected in surface soil at concentrations below their respective SLs.

PFHxS was detected in three surface soil samples at concentrations ranging from 0.26 J g/kg to 

0.38 J g/kg in samples collected from AOI02-04 and AOI02-03, respectively. PFOS was 

detected in one sample collected from AOI02-03 at a concentration of 0.32 J ug/kg. PFNA, 

PFOA, and PFBS were not detected in surface soil from AOI02.

PFOA, PFHxS, PFNA, and PFBS were not detected in any of the shallow subsurface soil (3 to 

9 ft bgs) samples collected from AOI 2. PFOS was detected in the sample collected from 

AOI02-02 at a concentration below the SL, 0.26 J g/kg.

Deep subsurface soil samples (10 to 14 ft bgs) were collected from boring locations AOI02-02 

and AOI02-03. PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in deep subsurface 

soils collected at AOI 2.
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6.4.2 AOI 2 – Groundwater Analytical Results 

Figures 6-13 and 6-14 present the ranges of detections in groundwater. Table 6-5 summarizes 

the groundwater results.

Groundwater samples were collected from four temporary wells associated with AOI 2 during 

the SI. PFOA, PFOS, PFHxS, PFNA, or PFBS when detected, did not exceed their respective 

SLs. PFOA was detected at low levels in groundwater collected from temporary well locations 

AOI02-03 and AOI02-04 with concentrations of 0.63 J ng/L and 0.74 J ng/L, respectively. PFOS 

detections in groundwater ranged from 0.48 J ng/L (AOI02-02) to 1.8 J ng/L (AOI02-01). 

PFHxS detections in groundwater ranged from 0.76 J ng/L (AOI02-01) to 2.8 ng/L (AOI02-04). 

PFNA was not detected in any of the groundwater samples collected from AOI 2. PFBS was 

only detected in groundwater collected from temporary well location AOI02-04, with a 

concentration of 1.1 J ng/L. 

6.4.3 AOI 2 – Conclusions

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

and PFBS were detected in groundwater at concentrations below their respective SLs. Therefore, 

further evaluation at AOI 2 is not warranted.

6.5 AOI 3 

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

AOI 3 - Building 28001. The detected compounds are summarized in Tables 6-2 through 6-5. 

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

6.5.1 AOI 3 – Soil Analytical Results

Figures 6-1 and 6-5 present the ranges of detections in soil. Tables 6-2 through 6-4 summarize 

the detected compounds in soil. 

Soil was sampled in three boring locations at AOI 3. Soil was sampled from two intervals 

(shallow and intermediate) at all three boring locations. 

PFOA, PFOS, and PFNA were detected in the surface interval at boring location AOI03-01, with 

concentrations of 0.5 J g/kg, 0.21 J g/kg, and 0.48 J g/kg, respectively and below their 

respective SLs. PFOA, PFOS, and PFNA were not detected in any other soil samples collected 

from AOI 3. PFHxS and PFBS were not detected in any of the soil samples collected from 

AOI 3.

6.5.2 AOI 3 – Groundwater Analytical Results 

Figures 6-6 and 6-7 present the ranges of detections in groundwater. Table 6-5 summarizes the 

groundwater results.
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Groundwater samples were collected from three temporary well locations associated with AOI 3 

during the SI activities. PFHxS, PFNA, and PFBS were not detected in groundwater at 

concentrations exceeding their respective SLs. PFOA was detected in two temporary well 

locations. PFOA was detected in AOI03-01 at a concentration of 3.4 ng/L below the SL of 6 

ng/L and at AOI03-03 with a concentration of 8.4 ng/L which exceeds the SL. PFOS was 

detected in all three temporary well locations, with detections ranging from 0.78 J ng/L (AOI03-

01) below the SL of 4 ng/L up to 5.3 ng/L (AOI03-03) which exceeds the SL. PFHxS was 

detected in samples collected from temporary wells AOI03-01 and AOI03-02 at concentrations 

of 2.8 ng/L and 5.5 ng/L, respectively. PFNA was detected in samples collected from temporary 

wells AOI03-01 and AOI03-03 at concentrations of 0.57 J ng/L and 5.7 ng/L, respectively. PFBS 

was detected in three temporary well locations, with detections ranging from 0.5 J ng/L (AOI03-

03) to 16 ng/L (AOI03-01).

6.5.3 AOI 3 – Conclusions

Based on the results of the SI, PFOA, PFOS, and PFNA were detected in soil at concentrations 

below their respective SLs. PFOA and PFOS were detected in groundwater at concentrations 

above their respective SLs. Based on the exceedances of the SLs in groundwater, further 

evaluation of AOI 3 is warranted.

6.6 AOI 4 

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

AOI 4 - Building 28002. The detected compounds are summarized in Tables 6-2 through 6-5. 

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

6.6.1 AOI 4 – Soil Analytical Results

Figures 6-1 through 6-5 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the detected compounds in soil. 

Soil was sampled in two boring locations at AOI 4. Soil was sampled from three intervals at 

boring location AOI04-01 and two intervals (shallow and intermediate) at boring location 

AOI04-02.

PFOA was detected in soil within the surface interval (0–2 ft) at boring location AOI04-01, with 

a concentration of 0.48 J g/kg. PFOS was detected in soil within the surface interval at both 

boring locations AOI04-01 and AOI04-02, with a maximum concentration of 1.3 g/kg, which is 

below the SL (19 g/kg). PFOS was also detected in intermediate (shallow subsurface) soil at 

boring location AOI04-02, at a concentration of 0.47 J g/kg, which is below the SL (13 g/kg).

There were no detections of PFOA in soils taken from the intermediate or deep interval at either 

boring location. Additionally, PFHxS, PFNA, and PFBS were not detected in any soil sample 

associated with AOI 4. 
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6.6.2 AOI 4 – Groundwater Analytical Results 

Figures 6-6 and 6-7 present the ranges of detections in groundwater. Table 6-5 summarizes the 

groundwater results.

Groundwater samples were collected from two temporary wells associated with AOI 4 during the 

SI activities. PFOA was detected in groundwater from temporary well location AOI04-01 with a 

concentration of 41 ng/L, exceeding the SL of 6 ng/L. PFOA was also detected below the SL in 

groundwater from temporary well location AOI04-02 with a concentration of 3 ng/L. PFOS was 

detected in excess of the SL at both wells with a maximum detection of 36 ng/L at temporary 

well location AOI04-02. PFNA was detected below the SL and ranged from 4.5 ng/L to 0.88 J 

ng/L in samples collected from temporary wells AOI04-01 and AOI04-02, respectively. PFHxS 

was detected at the SL (39 ng/L) in the sample collected from temporary well AOI04-01. PFHxS 

was detected below the SL in the groundwater sample collected from AOI04-02 at a 

concentration of 13 ng/L. PFBS was also detected in both wells below the SL with a maximum 

concentration of 9 ng/L at temporary well location AOI04-01. 

6.6.3 AOI 4 – Conclusions

Based on the results of the SI, PFOA and PFOS were detected in soil below their respective SL. 

PFOA, PFOS, PFHxS, PFNA and PFBS were detected in groundwater. PFOA exceeded its SL 

in one of the two temporary well locations and PFOS exceeded the SL in both temporary well 

locations. Based on the exceedances of the SLs in groundwater, further evaluation at AOI 4 is 

warranted.

6.7 AOI 5 

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

AOI 5 - Wash Bay. The detected compounds are summarized in Tables 6-2 through 6-5. Soil 

and groundwater results are presented on Figures 6-1 through 6-7.

6.7.1 AOI 5 – Soil Analytical Results

Figures 6-1 through 6-5 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the detected compounds in soil. 

Soil was sampled in three boring locations at AOI 5. Soil was sampled from four intervals at 

location AOI05-02, three intervals at location AOI05-03 and two intervals at location AOI05-01. 

PFOA was detected in surface soil (0–2 ft) in all three boring locations, with a maximum 

concentration of 2.4 g/kg in boring location AOI05-02, which is below the SL (19 g/kg). 

PFOS was detected in surface soil in two boring locations AOI05-01 (below the SL) and 

AOI05-02. PFOS with a reported concentration of 23 g/kg in surface soil at AOI05-02

exceeded the SL (13 g/kg). PFHxS was detected below the SL in one sample collected from 

AOI05-02 at a concentration of 6.7 g/kg. PFNA was detected below the SL (19 g/kg) in one

sample collected from boring AOI05-02 (0.4 J g/kg). PFBS was not detected in any surface soil 

samples.
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Shallow subsurface soil samples (6 to 13 ft bgs) were collected from three locations in AOI 5

(one location AOI05-02 had two shallow subsurface samples). PFOA, PFOS, PFHxS, PFNA, 

and PFBS were not detected in samples collected from borings AOI05-01 and AOI05-03. 

PFOA, PFHxS, and PFBS were all detected below the SLs in the soil collected from the shallow 

subsurface intervals (6–7 ft bgs) of boring location AOI05-02 with concentrations of 0.29 J

g/kg, 5.5 g/kg, and 0.7 J g/kg, respectively. PFOA, PFOS, PFHxS, and PFBS were also 

detected below SLs in the soil collected from the shallow subsurface sample (11–12 ft bgs) of 

boring location AOI05-02 with concentrations of 0.31 J g/kg, 0.29 J g/kg, 2.9 g/kg and 0.55 

J g/kg, respectively. 

There were no detections of PFOA, PFOS, PFHxS, PFNA, and PFBS in soil collected from the 

capillary zone/groundwater interface (deep subsurface interval) at AOI 5. 

6.7.2 AOI 5 – Groundwater Analytical Results 

Figures 6-6 and 6-7 present the ranges of detections in groundwater. Table 6-5 summarizes the 

groundwater results.

Groundwater samples were collected from two temporary well locations associated with AOI 5 

during the SI activities. Temporary well location AOI05-01 did not produce water and was not 

sampled. PFOA (12 ng/L), PFOS (23 ng/L), and PFHxS (110 ng/L) were detected in 

groundwater at concentrations exceeding their associated SLs at temporary well AOI05-02. 

PFNA (0.55 ng/L) and PFBS (130 ng/L) were detected below the SLs in the sample collected 

from temporary well AOI05-02. PFOA (1.2 J ng/L), PFHxS (0.69 J ng/L), and PFBS (0.99 J 

ng/L) were detected below their respective SLs in temporary well location AOI05-03.

6.7.3 AOI 5 – Conclusions

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

PFOS was detected in soil above the SL in one location. PFNA and PFBS were detected in 

groundwater below their respective SLs and PFOA, PFOS, and PFHxS were detected in 

groundwater at concentrations exceeding their associated SLs. RMTC personnel reported a 

release of AFFF water mixture at AOI 5 after SI sampling had been completed (January 2022); 

this resulted in the removal of approximately 200 tons of soil from the northern portion of the 

building at AOI 5. Based on the exceedances of the SLs in soils and groundwater and the recent 

reported release, further evaluation at AOI 5 is warranted.

6.8 AOI 6 

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

AOI 6 - Building 70200/70201, or the Fire Station. The detected compounds are summarized in 

Table 6-2 through Table 6-5. Soil and groundwater results are presented on Figures 6-15 

through 6-21.
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6.8.1 AOI 6 – Soil Analytical Results

Figures 6-15 through 6-19 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the detected compounds in soil. 

Soil was sampled in six boring locations4at AOI 6. Soil was sampled from three intervals at 

boring locations AOI06-02 and AOI06-03, two intervals at locations AOI06-04 and AOI06-04-

Off, and one interval at locations AOI06-01 and AOI06-01-Off.

PFOA, PFOS, PFHxS, and PFNA were detected in the shallow interval (0 to 2 ft bgs). PFOA 

concentrations were detected below the SL in samples collected from borings AOI06-01 (0.29 J 

g/kg), AOI06-03 (0.48 g/kg), and AOI06-04 (0.84 g/kg). PFOS was detected above the SL

(13 g/kg) in soil boring AOI06-04 (410 g/kg) and below the SL in AOI06-01 (0.25 g/kg) 

through AOI06-03 (11 g/kg). PFHxS was detected at concentrations below the SL (ranging from 

0.73 to 4.2 g/kg) in three of the foursamples collected from borings at AOI 6. PFNA was detected 

at a concentration (0.29 J g/kg) below the SL from one boring AOI06-04.

Shallow subsurface samples were collected from six boring locations at depths ranging from 2 to 

11 ft bgs. PFOA, PFNA, and PFBS were not detected in any of the shallow subsurface soil samples 

collected in AOI 6. PFOS was detected below the SL (160 g/kg) in samples from five of the six

boring locations and ranged from 0.24 J g/kg at AOI06-01 offset to 1.1 g/kg at AOI06-04. 

PFHxS was detected below the SL (1,600 g/kg) in two of the six samples collected from soil 

borings at AOI 6 at AOI06-03 (1.6 g/kg) and AOI06-04-off (0.45 J g/kg).

PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in deep (16–18.5 ft bgs) subsurface 

samples collected from AOI 6.

6.8.2 AOI 6 – Groundwater Analytical Results 

Figures 6-20 and 6-21 present the ranges of detections in groundwater. Table 6-5 summarizes 

the groundwater results.

Groundwater samples were collected from four temporary wells associated with AOI 6 during 

the SI activities. PFOA, PFOS, and PFHxS were detected in excess of their SLs in groundwater 

samples collected at AOI 6. PFOA, PFOS, PFHxS, PFNA, and PFBS were all detected in at 

least one sample at AOI 6. PFOA concentrations ranged from 0.88 J ng/L from the sample 

collected from temporary well AOI06-02 to 14 ng/L in the sample collected from temporary well 

AOI06-03. PFOA concentrations from samples in the remaining temporary wells were all below 

the SL (6 ng/L). PFOS concentrations from samples collected from temporary wells at AOI 6 

were in excess of the SL (4 ng/L) in three of the four temporary wells. PFOS concentrations 

ranged from 1.6 J ng/L to 120 ng/L in samples collected from temporary wells AOI06-02 and 

AOI06-3, respectively. PFHxS was detected in samples collected from all four temporary wells 

at AOI06. The PFHxS concentration from the sample collected from temporary well AOI06-03

(310 ng/L) exceeded the SL (39 ng/L). PFNA was detected below the SL (6 ng/L) in one sample 

4 Two borings, AOI06-01 and AOI06-04, were offset due to potentially penetrating a confining layer. Samples were 

collected from the original locations as well as the offset locations. 
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collected at AOI 6, from temporary well AOI06-01 (0.72 J ng/L). PFBS was detected below the 

SL (601 ng/L) in samples collected from all four temporary wells in AOI 6 ranging from 1.7 

ng/L from temporary well AOI06-02 to 48 ng/L from temporary well AOI06-01.

6.8.3 AOI 6 – Conclusions

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

was detected in shallow surface soil above the SL in one location. PFNA and PFBS were 

detected in groundwater below their respective SLs. PFOA, PFOS, and PFHxS were detected in 

groundwater at concentrations exceeding their associated SLs. Based on the exceedances of the 

SLs in soils and groundwater, further evaluation at AOI 6 is warranted.

6.9 ADDITIONAL FACILITY SAMPLING LOCATIONS – DRAINAGE PATHWAYS

This section presents the analytical results for soil and groundwater in comparison to SLs for 3 

additional borings/temporary wells located within the surface water drainage pathways located 

within the Robinson Army Airfield, leading from AOIs 1, 3, 4, and 5. The detected compounds 

are summarized in Tables 6-2 through 6-5. Soil and groundwater results are presented on 

Figures 6-1 through 6-7.

6.9.1 Additional Facility Sampling Locations – Drainage Pathways – Soil Analytical 

Results

Figures 6-1 through 6-5 present the ranges of detections in soil. Tables 6-2 through 6-4

summarize the detected compounds in soil.

Soil was sampled in three boring locations associated with drainage pathways leading from the 

AOIs within the Robinson Army Airfield. Soil was sampled from three intervals at boring 

locations RMTC-01 and RMTC-02 and two intervals at location RMTC-03. 

PFOA was detected below the SL in the soil samples taken from the shallow interval (0 to 2 ft) 

of all three boring locations, ranging from 0.23 J g/kg (RMTC-02) to 5.9 g/kg (RMTC-03). 

PFOS was detected below the SL in soil collected from the shallow interval of boring location 

RMTC-01 with a concentration of 11 g/kg. PFHxS was detected below the SL in two of the 

three boring locations in the shallow zone, RMTC-01 and RMTC-03 at concentrations of 1 g/kg 

and 0.72 g/kg, respectively. PFNA was detected below the SL in the shallow interval at one 

boring location, RMTC-01, at a concentration of 1.2 g/kg. 

PFOA, PFOS, PFHxS, and PFNA were detected at concentrations below their respective SLs in 

one of three shallow subsurface samples (depths ranging from 4 to 7 ft bgs) from soil boring 

RMTC-03.

PFOA, PFOS, PFHxS, PFNA, and PFBS were not detected in either of the two deep subsurface 

soil samples, depths ranging from 9 to 13 ft bgs.

PFBS was not detected in any soil sample associated with the drainage pathways exiting the 

Robinson Army Airfield. 
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6.9.2 Additional Facility Sampling Locations – Drainage Pathways – Groundwater 

Analytical Results 

Figure 6-6 and Figure 6-7 present the ranges of detections in groundwater. Table 6-5 

summarizes the groundwater results.

Groundwater samples were collected from three temporary wells associated with the drainage 

pathways exiting the Robinson Army Airfield. PFOA, PFOS, PFHxS, PFNA, and PFBS were 

detected in all three groundwater samples associated with drainage pathways exiting the 

Robinson Army Airfield. PFOA was detected in groundwater samples collected from all three

temporary wells, one of which exceeded the SL of 6 ng/L. Concentrations ranged from 3.7 ng/L

to 190 ng/L at temporary well locations RMTC-02 and RMTC-03, respectively. PFOS was 

detected at concentrations in excess of the SL (4 ng/L) at all three temporary wells and ranged 

from 4.2 ng/L to 1,000 ng/L at temporary well locations RMTC-01 and RMTC-03, respectively. 

PFHxS was detected in groundwater from all three temporary wells, one of which exceeded the 

SL of 39 ng/L. Concentrations ranged from 12 ng/L to 230 ng/L at temporary well locations 

RMTC-01 and RMTC-03, respectively. PFNA was detected in groundwater from all three

temporary wells, one of which exceeded the SL of 6 ng/L. Concentrations ranged from 0.5 J 

ng/L to 31 ng/L at temporary well locations RMTC-01 and RMTC-03, respectively. PFBS was 

detected below the SL in all three groundwater samples with concentrations ranging from 2.8 

ng/L to 54 ng/L at temporary well locations RMTC-02 and RMTC-03, respectively.

6.9.3 Additional Facility Sampling Locations – Drainage Pathways – Conclusions

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

their respective SLs. PFBS was detected in groundwater below the SL and PFOA, PFOS, 

PFHxS, PFNA were detected in one or more groundwater samples at concentrations exceeding 

their associated SLs. These results also indicate that relevant compounds from AOIs 1, 3, 4, and 

5 are migrating away from source areas at concentrations exceeding respective SLs. Based on the 

exceedances of the SLs in groundwater further evaluation of the Drainage Pathways is 

warranted.
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Table 6-2. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil, Site Inspection Rep

Analyte Screening Level1, 2 Unit Result Qual Result Qual Result Qual 

Perfluorobutanesulfonic acid (PFBS) 1900 μg/kg ND U ND U ND U Perfluorohexanesulfonic acid (PFHxS) 130 μg/kg ND U ND U 4.5 Perfluorononanoic acid (PFNA) 19 μg/kg ND U ND U 20 Perfluorooctanesulfonic acid (PFOS) 13 μg/kg ND U ND U 44 

Perfluorooctanoic acid (PFOA) 19 μg/kg ND U ND U 6.2 Notes:

AOI01-01 AOI01-01 AOI01-02 

AOI01-02-SB-0-2 

AOI01-01-SB-0-2

AOI01-01-SB-0-2 AOI01-01-SB-0-2-DUP 

0-2 0-2 0-2 

Location ID

Sample Name

Parent Sample ID

Sample Date

Depth (ft bgs)

10/27/2021 10/27/2021 10/27/2021 

(1) The Screening Levels for soil are based on a residential scenario for incidental ingestion of contaminated soil.(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’sRegional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limit of Detection.Associated numerical value is approximate.ft bgs = feet below ground surfaceμg/kg = Microgram(s) per kilogramQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

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PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
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Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 1900 μg/kgPerfluorohexanesulfonic acid (PFHxS) 130 μg/kgPerfluorononanoic acid (PFNA) 19 μg/kgPerfluorooctanesulfonic acid (PFOS) 13 μg/kgPerfluorooctanoic acid (PFOA) 19 μg/kgNotes:

Location ID

Sample Name

Parent Sample ID

Sample Date

Depth (ft bgs)

(1) The Screening Levels for soil are based on a residential scenario for incidental ingestion of contaminated soil.(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’sRegional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limit of Detection.Associated numerical value is approximate.ft bgs = feet below ground surfaceμg/kg = Microgram(s) per kilogramQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Result Qual Result Qual Result Qual 

ND U 1.1 J ND U 

0.36 J 12 ND U 0.41 J 9.3 ND U 

2.2 J 190 ND U 

0.61 3.9 ND U 

AOI01-06 AOI01-07 AOI02-01 

AOI01-06-SB-0-2-DUP AOI01-07-SB-0-2 AOI02-01-SB-0-2 

AOI01-06-SB-0-2

10/27/2021 10/19/2021 

0-2 

10/28/2021 

0-2 0-2 

EA Engineering, Science, and Technology, Inc., PBC

Table 6-2. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil, Site Inspection Rep

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 1900 μg/kgPerfluorohexanesulfonic acid (PFHxS) 130 μg/kgPerfluorononanoic acid (PFNA) 19 μg/kgPerfluorooctanesulfonic acid (PFOS) 13 μg/kgPerfluorooctanoic acid (PFOA) 19 μg/kgNotes:

Location ID

Sample Name

Parent Sample ID

Sample Date

Depth (ft bgs)

(1) The Screening Levels for soil are based on a residential scenario for incidental ingestion of contaminated soil.(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’sRegional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limit of Detection.Associated numerical value is approximate.ft bgs= feet below ground surfaceμg/kg = Microgram(s) per kilogramQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Result Qual Result Qual Result Qual R

ND U ND U ND U ND U ND U ND U ND U ND U ND U 

ND U ND U 1.3 ND U ND U 0.48 J 

AOI03-02 AOI03-03 AOI04-01 

AOI03-02-SB-0-2 AOI03-03-SB-0-2 AOI04-01-SB-0-2 A

10/21/2021 10/21/2021 10/21/2021 

0-2 0-2 0-2 

EA Engineering, Science, and Technology, Inc., PBC

Table 6-2. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil, Site Inspection Rep

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 1900 μg/kgPerfluorohexanesulfonic acid (PFHxS) 130 μg/kgPerfluorononanoic acid (PFNA) 19 μg/kgPerfluorooctanesulfonic acid (PFOS) 13 μg/kgPerfluorooctanoic acid (PFOA) 19 μg/kgNotes:

Location ID

Sample Name

Parent Sample ID

Sample Date

Depth (ft bgs)

(1) The Screening Levels for soil are based on a residential scenario for incidental ingestion of contaminated soil.(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and Soil using EPA’sRegional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit of Detection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limit of Detection.Associated numerical value is approximate.ft bgs = feet below ground surfaceμg/kg = Microgram(s) per kilogramQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Result Qual Result Qual Result Qual Result 

ND U ND U ND U ND ND U ND U 0.75 0.73 

ND UJ ND UJ ND U ND ND U 0.25 J 0.41 J 11 

0.27 J+ 0.29 J ND U 0.48 

AOI05-03 AOI06-01 AOI06-02 AOI0

AOI05-03-SB-0-2-DUP AOI06-01-SB-0-2 AOI06-02-SB-0-2 AOI06-03

AOI05-03-SB-0-2

10/26/2021 10/20/2021 10/20/2021 10/20/

0-2 0-2 0-2 0-

EA Engineering, Science, and Technology, Inc., PBC

Table 6-2. PFOA, PFOS, PFBS, PFNA, and PFHxS Results in Surface Soil, Site Inspection Rep

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

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

Analyte Screening Level1, 2 Unit Result Qual Result Qual Result Qual Res

Perfluorobutanesulfonic acid (PFBS) 25000 ug/kg ND U ND U ND U ND Perfluorohexanesulfonic acid (PFHxS) 1600 ug/kg ND U 1.4 ND U ND 

Perfluorononanoic acid (PFNA) 250 ug/kg ND U 2.5 ND U ND Perfluorooctanesulfonic acid (PFOS) 160 ug/kg ND U 7.1 ND U 0.4

Perfluorooctanoic acid (PFOA) 250 ug/kg ND U 3.1 ND U 0.2

Notes:

(1) The Screening Levels for soil are based on incidental ingestion of soil in a industrial/

commercial worker scenario.

(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in

Groundwater and Soil using EPA’s Regional Screening Level Calculator. HazardQuotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit ofDetection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjustedLimit of Detection. Associated numerical value is approximate.ft bgs = feet below ground surfaceug/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Depth (ft bgs)

Sample Date

Parent Sample ID

Sample Name

Location ID AOI01-01 AOI01-02 AOI01-03 

AOI01-01-SB-5-6 AOI01-02-SB-3-4 AOI01-03-SB-2-3 AOI0

AOI01-

10/27/2021 10/27/2021 10/28/2021 

5-6 3-4 2-3 

EA Engineering, Science, and Technology, Inc., PBC.

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 25000 ug/kgPerfluorohexanesulfonic acid (PFHxS) 1600 ug/kgPerfluorononanoic acid (PFNA) 250 ug/kgPerfluorooctanesulfonic acid (PFOS) 160 ug/kgPerfluorooctanoic acid (PFOA) 250 ug/kgNotes:

(1) The Screening Levels for soil are based on incidental ingestion of soil in a industrial/

commercial worker scenario.

(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater

and Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit ofDetection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limit ofDetection. Associated numerical value is approximate.ft bgs = feet below ground surfaceug/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Depth (ft bgs)

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual Result Qual 

ND U ND U ND U 

0.65 ND U ND U 

ND U ND U ND U 

4.2 ND U 0.26 J 

0.35 J ND U ND U 

AOI01-07 AOI02-01 AOI02-02 

AOI01-07-SB-4.5-5.5 AOI02-01-SB-6-7 AOI02-02-SB-8-9 

10/27/2021 10/19/2021 10/19/2021 

4.5-5.5 6-7 8-9 

EA Engineering, Science, and Technology, Inc., PBC.

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 25000 ug/kgPerfluorohexanesulfonic acid (PFHxS) 1600 ug/kgPerfluorononanoic acid (PFNA) 250 ug/kgPerfluorooctanesulfonic acid (PFOS) 160 ug/kgPerfluorooctanoic acid (PFOA) 250 ug/kgNotes:

(1) The Screening Levels for soil are based on incidental ingestion of soil in a industrial/

commercial worker scenario.

(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater

and Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit ofDetection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limitof Detection. Associated numerical value is approximate.ft bgs = feet below ground surfaceug/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Depth (ft bgs)

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual Result Qual Res

ND U ND U ND U ND ND U ND U ND U ND ND U ND UJ ND U ND ND U ND U ND U ND ND U ND UJ ND U ND 

AOI03-01 AOI03-02 AOI03-03 

AOI03-01-SB-8-9 AOI03-02-SB-5-6 AOI03-03-SB-2-3 AOI

10/21/2021 10/21/2021 10/21/2021 1

8-9 5-6 2-3 

EA Engineering, Science, and Technology, Inc., PBC.

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 25000 ug/kgPerfluorohexanesulfonic acid (PFHxS) 1600 ug/kgPerfluorononanoic acid (PFNA) 250 ug/kgPerfluorooctanesulfonic acid (PFOS) 160 ug/kgPerfluorooctanoic acid (PFOA) 250 ug/kgNotes:

(1) The Screening Levels for soil are based on incidental ingestion of soil in a industrial/

commercial worker scenario.

(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in

Groundwater and Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient(HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit ofDetection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjustedLimit of Detection. Associated numerical value is approximate.ft bgs = feet below ground surfaceug/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Depth (ft bgs)

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual Result 

0.70 J ND U ND 

5.5 ND U ND 

ND U ND U ND ND U ND U 0.28 

0.29 J ND U ND 

AOI05-02 AOI05-03 AOI

AOI05-02-SB-6-7 AOI05-03-SB-7-8 AOI06-01-

10/26/2021 10/26/2021 10/2

6-7 7-8 2

EA Engineering, Science, and Technology, Inc., PBC.

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 25000 ug/kgPerfluorohexanesulfonic acid (PFHxS) 1600 ug/kgPerfluorononanoic acid (PFNA) 250 ug/kgPerfluorooctanesulfonic acid (PFOS) 160 ug/kgPerfluorooctanoic acid (PFOA) 250 ug/kgNotes:

(1) The Screening Levels for soil are based on incidental ingestion of soil in a industrial/

commercial worker scenario.

(2) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater

and Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal to the adjusted Limit ofDetection (LOD).UJ = The analyte was not detected and was reported less than or equal to the adjusted Limitof Detection. Associated numerical value is approximate.ft bgs = feet below ground surfaceug/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierND = Analyte not detected above the LOD (LOD values are presented in Appendix F).

Depth (ft bgs)

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual Result 

ND U ND U ND 

1.6 0.45 J ND 

ND U ND U ND 

0.44 J 0.94 1.1 

ND U ND U ND 

AOI06-03 AOI06-04 AOI06-

AOI06-03-SB-7.5-8.5 AOI06-04-OFF-SB-7-8 AOI06-04-SB

10/20/2021 10/20/2021 10/20/20

7.8-8.5 7-8 10-11 

EA Engineering, Science, and Technology, Inc., PBC.

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-22

This page intentionally left blank
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

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

Analyte

Screening 

Level1, 2 Unit Result Qual Result Qual Result Qual Result Qual 

Perfluorobutanesulfonic acid (PFBS) 25,000 μg/kg ND U ND U ND U ND U Perfluorohexanesulfonic acid (PFHxS) 1,600 μg/kg ND U ND U 0.84 ND U Perfluorononanoic acid (PFNA) 250 μg/kg ND U ND U ND U ND U Perfluorooctanesulfonic acid (PFOS) 160 μg/kg ND U ND U ND U ND U 

Perfluorooctanoic acid (PFOA) 250 μg/kg ND U ND U ND U ND U 

Notes:

(1) The Screening Levels for soil are based on incidental ingestion of

soil in a industrial/commercial worker scenario.

(2) Assistant Secretary of Defense. 2022. Risk-Based Screening

Levels in Groundwater and Soil using EPA’s Regional ScreeningLevel Calculator. Hazard Quotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal tothe adjusted Limit of Detection (LOD).UJ = The analyte was not detected and was reported less than orequal to the adjusted Limit of Detection. Associated numerical valueis approximate.ft bgs = feet below ground surfaceμg/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierND = Analyte not detected above the LOD (LOD values arepresented in Appendix F).

Parent Sample ID

Sample Name

Location ID AOI01-01 AOI01-04

Depth (ft bgs) 10-11 8-9 9-10

Sample Date

AOI01-07 AOI02-02 

AOI01-01-SB-10-11 AOI01-04-SB-8-9 AOI01-07-SB-9-10 AOI02-02-SB-13-14 

10/27/2021 10/28/2021 10/27/2021 10/19/2021 

13-14 

EA Engineering, Science, and Technology, Inc., PBC

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte

Screening 

Level1, 2 Unit

Perfluorobutanesulfonic acid (PFBS) 25,000 μg/kgPerfluorohexanesulfonic acid (PFHxS) 1,600 μg/kgPerfluorononanoic acid (PFNA) 250 μg/kgPerfluorooctanesulfonic acid (PFOS) 160 μg/kg

Perfluorooctanoic acid (PFOA) 250 μg/kg

Notes:

(1) The Screening Levels for soil are based on incidental ingestion of

soil in a industrial/commercial worker scenario.

(2) Assistant Secretary of Defense. 2022. Risk-Based Screening

Levels in Groundwater and Soil using EPA’s Regional ScreeningLevel Calculator. Hazard Quotient (HQ)=0.1. May 2022.Values exceeding the Screening Level are shaded gray.J = Estimated concentrationU = The analyte was not detected at a level greater than or equal tothe adjusted Limit of Detection (LOD).UJ = The analyte was not detected and was reported less than orequal to the adjusted Limit of Detection. Associated numerical valueis approximate.ft bgs = feet below ground surfaceμg/kg = Microgram(s) per kilogramLOD = Limit of DetectionLOQ = Limit of QuantitationQual = QualifierNDND = Analyte not detected above the LOD (LOD values arepresented in Appendix F).

Parent Sample ID

Sample Name

Location ID

Depth (ft bgs)

Sample Date

Result Qual Result Qual Result 

ND U ND U ND ND U ND U ND ND U ND U ND ND U ND U ND ND U ND U ND 

AOI06-03 AOI0

AOI06-02-SB-16-17 AOI06-03-SB-17.5-18.5 AOI06-04-O

AOI06-02

10/20/2021 10/20/2021 10/20

16-17 17.5-18.5 17-

EA Engineering, Science, and Technology, Inc., PBC

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (μg/kg)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

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

Analyte Screening Level1 Unit Result Qual Result Qual Result Qual Result Qua

Perfluorobutanesulfonic acid (PFBS) 601 ng/L 3.3 3.5 79 16 

Perfluorohexanesulfonic acid (PFHxS) 39 ng/L 17 19 790 130 

Perfluorononanoic acid (PFNA) 6 ng/L 0.98 J 0.99 J 770 J+ 68 

Perfluorooctanesulfonic acid (PFOS) 4 ng/L 27 29 3000 J+ 130 Perfluorooctanoic acid (PFOA) 6 ng/L 5.2 6.4 540 220 

Notes:

(1) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and

Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.

Values exceeding the Screening Level are shaded gray.

J = Estimated concentrationJ- = Estimated concentration, biased lowJ+ = Estimated concentration, biased highUJ = The analyte was not detected and was reported as less than the LOD.

U = The analyte was not detected and was reported less than or equal to the adjusted Limit ofDetection. Associated numerical value is approximate.ng/L = Nanogram(s) per literQual = QualifierND = Analyte not detected above the LOD (LOD values are presented inAppendix F).

Sample Date 10/28/2021 10/28/2021 10/28/2021 10/28/2021 

Parent Sample ID AOI01-01-GW

Sample Name AOI01-01-GW AOI01-01-GW-DUP AOI01-02-GW AOI01-03-GW 

Location ID AOI01-01 AOI01-01 AOI01-02 AOI01-03 

EA Engineering, Science, and Technology, Inc., PBC

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (ng/L)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1 Unit

Perfluorobutanesulfonic acid (PFBS) 601 ng/LPerfluorohexanesulfonic acid (PFHxS) 39 ng/LPerfluorononanoic acid (PFNA) 6 ng/LPerfluorooctanesulfonic acid (PFOS) 4 ng/LPerfluorooctanoic acid (PFOA) 6 ng/LNotes:

(1) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and

Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.

Values exceeding the Screening Level are shaded gray.J = Estimated concentrationJ- = Estimated concentration, biased lowJ+ = Estimated concentration, biased highUJ = The analyte was not detected and was reported less than or equal to the adjusted Limit ofDetection. Associated numerical value is approximate.U = The analyte was not detected at a level greater than or equal to theadjusted Limit of Detection (LOD).ng/L = Nanogram(s) per literQual = QualifierND = Analyte not detected above the LOD (LOD values are presented inAppendix F).

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual Result Qual Result Qual 

ND U ND U ND U 1.1 J 

0.76 J ND U 2.2 J+ 2.8 

ND U ND U ND U ND U 

1.8 J 0.48 J 0.93 J ND U 

ND U ND U 0.63 J 0.74 J 

10/26/2021 10/26/2021 10/29/2021 10/19/2021 

AOI02-01-GW AOI02-02-GW AOI02-03-GW AOI02-04-GW 

AOI02-01 AOI02-02 AOI02-03 AOI02-04 

EA Engineering, Science, and Technology, Inc., PBC

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (ng/L)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1 Unit

Perfluorobutanesulfonic acid (PFBS) 601 ng/LPerfluorohexanesulfonic acid (PFHxS) 39 ng/LPerfluorononanoic acid (PFNA) 6 ng/LPerfluorooctanesulfonic acid (PFOS) 4 ng/LPerfluorooctanoic acid (PFOA) 6 ng/LNotes:

(1) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and

Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.

Values exceeding the Screening Level are shaded gray.J = Estimated concentrationJ- = Estimated concentration, biased lowJ+ = Estimated concentration, biased highUJ = The analyte was not detected and was reported less than or equal to the adjusted Limit ofDetection. Associated numerical value is approximate.U = The analyte was not detected at a level greater than or equal to theadjusted Limit of Detection (LOD).ng/L = Nanogram(s) per literQual = QualifierND = Analyte not detected above the LOD (LOD values are presented inAppendix F).

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual Result Qual Result Qual 

9.0 0.98 J 130 0.99 J 

39 13 110 0.69 J 

4.5 0.88 J 0.66 J ND U 

32 36 23 ND U 

41 3.0 12 1.2 J 

10/25/2021 10/25/2021 10/29/2021 10/27/2021 

AOI04-01-GW AOI04-02-GW AOI05-02-GW AOI05-03-GW 

AOI04-01 AOI04-02 AOI05-02 AOI05-03 

EA Engineering, Science, and Technology, Inc., PBC

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (ng/L)
Site Inspection Report

Robinson Maneuver Training Center, Arkansas 

Analyte Screening Level1 Unit

Perfluorobutanesulfonic acid (PFBS) 601 ng/LPerfluorohexanesulfonic acid (PFHxS) 39 ng/LPerfluorononanoic acid (PFNA) 6 ng/LPerfluorooctanesulfonic acid (PFOS) 4 ng/LPerfluorooctanoic acid (PFOA) 6 ng/LNotes:

(1) Assistant Secretary of Defense. July 2022. Risk-Based Screening Levels in Groundwater and

Soil using EPA’s Regional Screening Level Calculator. Hazard Quotient (HQ)=0.1. May 2022.

Values exceeding the Screening Level are shaded gray.J = Estimated concentrationJ- = Estimated concentration, biased lowJ+ = Estimated concentration, biased highUJ = The analyte was not detected and was reported less than or equal to the adjusted Limit ofDetection. Associated numerical value is approximate.U = The analyte was not detected at a level greater than or equal to theadjusted Limit of Detection (LOD).ng/L = Nanogram(s) per literQual = QualifierND = Analyte not detected above the LOD (LOD values are presented inAppendix F).

Sample Date

Parent Sample ID

Sample Name

Location ID

Result Qual Result Qual 

8.3 4.6 

19 12 

ND U 0.50 J 

72 4.2 

1.9 4.0 

10/22/2021 10/27/2021 

AOI06-04-GW RMTC-01-GW 

AOI06-04-off RMTC-01 

EA Engineering, Science, and Technology, Inc., PBC

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

PFAS by LC/MS/MS compliant with QSM Version 5.3 Table B-15 (ng/L)
Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Figure 6-1

AOI 1, AOI 3, AOI 4 and AOI 5

PFOS Detections in Soil

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-01

AOI01-07

AOI01-04

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

AR

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

0 500

Feet

0 500

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

^_

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

Notes:

PFOS = Perfluorooctanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-30

This page intentionally left blank
Figure 6-2

AOI 1, AOI 3, AOI 4 and AOI 5

PFOA Detections in Soil

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-01

AOI05-03

AOI05-02

AOI04-01

AOI01-07

AOI01-04

AOI01-01

RMTC-02

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

AR

0 500

Feet

0 500

Feet

Shallow Intermediate Deep

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

^_

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

Notes:

PFOA = Perfluorooctanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-32

This page intentionally left blank
Figure 6-3

AOI 1, AOI 3, AOI 4 and AOI 5

PFBS Detections in Soil

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-01

AOI01-04

AOI01-01

AOI01-07

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

AR

0 500

Feet

0 500

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

Notes:

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-34

This page intentionally left blank
Figure 6-4

AOI 1, AOI 3, AOI 4 and AOI 5

PFNA Detections in Soil

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-02

AOI05-03

AOI05-02

AOI04-01

AOI01-04

AOI01-01

AOI01-07

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

AR

0 500

Feet

0 500

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

Notes:

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-36

This page intentionally left blank
Figure 6-5

AOI 1, AOI 3, AOI 4 and AOI 5

PFHxS Detections in Soil

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI05-01

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-02

AOI05-03

AOI05-02

AOI04-01

AOI01-04

AOI01-01

AOI01-07

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

AR

0 500

Feet

0 500

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

Notes:

PFHxS = Perfluorohexanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-38

This page intentionally left blank
Figure 6-6

AOI 1, AOI 3, AOI 4 and AOI 5

PFOA, PFOS and PFBS Detections in Groundwater

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

AR

0 500

Feet

PFOA PFOS

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

0 500

Feet

PFBS

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Notes:

PFOA = Perfluorooctanesulfonic acid

PFOS = Perfluorooctanoic acid

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo.

> 70

> 40 - 70

> 6 - 40

> ND - 6

ND (Non-Detect)

PFOA Results (ng/L)

> 70

> 40 - 70

> 4 - 40

> ND - 4

ND (Non-Detect)

PFOS Results (ng/L)

> 1,000

> 601 - 1,000

> 100 - 601

> ND - 100

ND (Non-Detect)

PFBS Results (ng/L)

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-40

This page intentionally left blank
*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

*#

*#

*#

*#

*#

RMTC-03

RMTC-02

RMTC-01

AOI05-03

AOI05-02

AOI04-02

AOI04-01

AOI03-03

AOI03-02

AOI03-01

AOI01-07

AOI01-06

AOI01-05

AOI01-04

AOI01-03

AOI01-02

AOI01-01

Outfall 005

Outfall 004

Outfall 003

Outfall 002

Outfall 001

3

0 500

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

*# Outfall

Surface Water Flow Direction

Groundwater Flow Direction

Intermittent Creek/Stream

AR

Path: C:\Users\kwheatley\Desktop\PFAS\RMTC\PROJECTS\RMTC_SI.aprx

0 500

Feet

PFHxS PFNA

Notes:

PFHxS = Perfluorohexanesulfonic acid

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo.

> 1,000

> 100 - 1,000

> 39 - 100

> ND - 39

ND (Non-Detect)

PFHxS Result (ng/L)

> 1,000

> 100 - 1,000

> 6 - 100

> ND - 6

ND (Non-Detect)

PFNA Results (ng/L)

Figure 6-7

AOI 1, AOI 3, AOI 4 and AOI 5

PFHxS and PFNA Detections in Groundwater

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

^_
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-42

This page intentionally left blank
Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Figure 6-8

AOI 2

PFOS Detections in Soil

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-03

AOI02-02

3

0 100

Feet

AR

Data Sources:

ESRI 2022

AECOM 2019

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

Notes:

PFOS = Perfluorooctanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-44

This page intentionally left blank
Figure 6-9

AOI 2

PFOA Detections in Soil

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-03

AOI02-02

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

Notes:

PFOA = Perfluorooctanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-46

This page intentionally left blank
Figure 6-10

AOI 2

PFBS Detections in Soil

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-03

AOI02-02

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

Notes:

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-48

This page intentionally left blank
Figure 6-11

AOI 2

PFNA Detections in Soil

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-03

AOI02-02

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

Notes:

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-50

This page intentionally left blank
Figure 6-12

AOI 2

PFHxS Detections in Soil

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-03

AOI02-02

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

Notes:

PFHxS = Perfluorohexanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-52

This page intentionally left blank
Figure 6-13

AOI 2

PFOA, PFOS and PFBS Detections in Groundwater

AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

3

0 100

Feet

AR

0 100

Feet

PFOA PFOS

AOI02-04

AOI02-03

AOI02-02

AOI02-01

0 100

Feet

PFBS

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Notes:

PFOA = Perfluorooctanesulfonic acid

PFOS = Perfluorooctanoic acid

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo.

> 70

> 40 - 70

> 6 - 40

> ND - 6

ND (Non-Detect)

PFOA Results (ng/L)

> 70

> 40 - 70

> 4 - 40

> ND - 4

ND (Non-Detect)

PFOS Results (ng/L)

> 1,000

> 601 - 1,000

> 100 - 601

> ND - 100

ND (Non-Detect)

PFBS Results (ng/L)

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-54

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AOI02-04

AOI02-03

AOI02-02

AOI02-01

AOI02-04

AOI02-03

AOI02-02

AOI02-01

3

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Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Surface Water Flow Direction

Groundwater Flow Direction

AR

Path: C:\Users\kwheatley\Desktop\PFAS\RMTC\PROJECTS\RMTC_SI.aprx

0 100

Feet

PFHxS PFNA

Notes:

PFHxS = Perfluorohexanesulfonic acid

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo.

> 1,000

> 100 - 1,000

> 39 - 100

> ND - 39

ND (Non-Detect)

PFHxS Result (ng/L)

> 1,000

> 100 - 1,000

> 6 - 100

> ND - 6

ND (Non-Detect)

PFNA Results (ng/L)

Figure 6-14

AOI 2

PFHxS and PFNA Detections in Groundwater

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

^_
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-56

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Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Figure 6-15

AOI 6

PFOS Detections in Soil

AOI06-04 AOI06-03

AOI06-02

AOI06-01

AOI06-04 AOI06-03

AOI06-02

AOI06-04-Off

AOI06-01-Off

AOI06-03

AOI06-02

3

0 100

Feet

AR

Data Sources:

ESRI 2022

AECOM 2019

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

Groundwater Flow Direction

^_

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

> 1,600

> 160 - 1,600

> 13 - 160

> ND - 13

ND (Non-Detect)

PFOS Results (μg/Kg)

Notes:

PFOS = Perfluorooctanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

AOI06-04-Off
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-58

This page intentionally left blank
Figure 6-16

AOI 6

PFOA Detections in Soil

AOI06-04 AOI06-03

AOI06-02

AOI06-01

AOI06-04 AOI06-03

AOI06-02

AOI06-04-Off

AOI06-01-Off

AOI06-03

AOI06-02

AOI06-04-Off

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

Groundwater Flow Direction

^_

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

> 2,500

> 250- 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFOA Results (μg/Kg)

Notes:

PFOA = Perfluorooctanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-60

This page intentionally left blank
Figure 6-17

AOI 6

PFBS Detections in Soil

AOI06-04 AOI06-03

AOI06-02

AOI06-01

AOI06-04 AOI06-03

AOI06-02

AOI06-04-Off

AOI06-01-Off

AOI06-03

AOI06-02

AOI06-04-Off

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

> 25,000

> 1,900 - 25,000

> 10 - 1,900

> ND - 10

ND (Non-Detect)

PFBS Results (μg/Kg)

Notes:

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-62

This page intentionally left blank
Figure 6-18

AOI 6

PFNA Detections in Soil

AOI06-04 AOI06-03

AOI06-02

AOI06-01

AOI06-03

AOI06-02

AOI06-04-Off

AOI06-01-Off

AOI06-04 AOI06-03

AOI06-02

AOI06-04-Off

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 2,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

> 2 ,500

> 250 - 2,500

> 19 - 250

> ND - 19

ND (Non-Detect)

PFNA Results (μg/Kg)

Notes:

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-64

This page intentionally left blank
Figure 6-19

AOI 6

PFHxS Detections in Soil

AOI06-04 AOI06-03

AOI06-02

AOI06-01

AOI06-04 AOI06-03

AOI06-02

AOI06-04-Off

AOI06-01-Off

AOI06-03

AOI06-02

3

0 100

Feet

AR

0 100

Feet

0 100

Feet

Shallow Intermediate Deep

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrogeology

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

> 1,600

> 130 - 1,600

> 10 - 130

> ND - 10

ND (Non-Detect)

PFHxS Result (μg/Kg)

Notes:

PFHxS = Perfluorohexanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo. Depth intervals shown

represent respective sampling position

within a given soil boring location.

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

AOI06-04-Off
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-66

This page intentionally left blank
Figure 6-20

AOI 6

PFOA, PFOS and PFBS Detections in Groundwater

AOI06-03

AOI06-02

AOI06-03

AOI06-02

3

0 100

Feet

AR

0 100

Feet

PFOA PFOS

AOI06-03

AOI06-02

0 100

Feet

PFBS

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Groundwater Flow Direction

^_

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Notes:

PFOA = Perfluorooctanesulfonic acid

PFOS = Perfluorooctanoic acid

PFBS = Perfluorobutanesulfonic acid

Exceedances of the OSD SL are depicted

with a yellow halo.

> 70

> 40 - 70

> 6 - 40

> ND - 6

ND (Non-Detect)

PFOA Results (ng/L)

> 70

> 40 - 70

> 4 - 40

> ND - 4

ND (Non-Detect)

PFOS Results (ng/L)

> 1,000

> 601 - 1,000

> 100 - 601

> ND - 100

ND (Non-Detect)

PFBS Results (ng/L)

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

Sample ID AOI06-01

Boring ID AOI06-01-Off

Sample ID AOI06-01

Boring ID AOI06-01-Off

Sample ID AOI06-01

Boring ID AOI06-01-Off

Sample ID AOI06-04

Boring ID AOI06-04-Off Sample ID AOI06-04

Boring ID AOI06-04-Off

Sample ID AOI06-04

Boring ID AOI06-04-Off
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-68

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AOI06-03

AOI06-02

AOI06-03

AOI06-02

3

0 100

Feet

Facility Data

Facility Boundary

Area of Interest

Potential PFAS Release

Hydrology/Hydrogeology

Groundwater Flow Direction

AR

Path: C:\Users\kwheatley\Desktop\PFAS\RMTC\PROJECTS\RMTC_SI.aprx

0 100

Feet

PFHxS PFNA

Notes:

PFHxS = Perfluorohexanesulfonic acid

PFNA = Perfluorononanoic acid

Exceedances of the OSD SL are depicted

with a yellow halo.

> 1,000

> 100 - 1,000

> 39 - 100

> ND - 39

ND (Non-Detect)

PFHxS Result (ng/L)

> 1,000

> 100 - 1,000

> 6 - 100

> ND - 6

ND (Non-Detect)

PFNA Results (ng/L)

Figure 6-21

AOI 6

PFHxS and PFNA Detections in Groundwater

Army National Guard Site Inspections

Site Investigation Report

Robinson Maneuver Training Center, Arkansas

Data Sources:

ESRI 2022

AECOM 2019

Date:..........................August 2022

Prepared By:.............................EA

Prepared For:....................USACE

Projection:........WGS 84 UTM 15N

^_

Sample ID AOI06-04

Boring ID AOI06-04-Off

Sample ID AOI06-04

Boring ID AOI06-04-Off

Sample ID AOI06-01

Boring ID AOI06-01-Off

Sample ID AOI06-01

Boring ID AOI06-01-Off
Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 6-70

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Site Inspection Report

Robinson Maneuver Training Center, Arkansas Version: FINAL

EA Engineering, Science, and Technology, Inc., PBC 7-1

7. EXPOSURE PATHWAYS

The Conceptual Site Models (CSMs) for each AOI, revised based on the SI findings, are 

presented on Figures 7-1 through 7-3. 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 solely 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. SLs are presented in Section 6.1 of this report.

1. Contaminant source

2. Environmental fate and transport

3. Exposure point

4. Exposure route

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 no identified complete 

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

complete if the relevant compounds are detected, in which case the CSM figure uses a half-filled 

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

filled circle symbol is used to indicate when a potentially complete exposure pathway has 

detections of relevant compounds above the SLs. Areas with an identified potentially complete 

pathway that have detections of the relevant compounds above the SLs may warrant further 

investigation. Although the CSMs indicate whether potentially complete exposure pathways may 

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

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

In general, the potential exposure pathways are ingestion and inhalation. Human exposure via the 

dermal contact pathway may occur, and current risk practice suggests it is an insignificant 

pathway compared to ingestion; however, exposure data for dermal pathways are sparse and 

continue to be the subject of PFAS toxicological study. The receptors evaluated are consistent 

with those listed in USEPA guidance for risk screening (USEPA 2001). Receptors at the Facility

include site workers (e.g., facility staff and visiting soldiers), construction workers, off-facility 

residents, trespassers (though unlikely due to restricted access), and recreational users. The 

public have access to portions of the facility for recreational activities like hunting and personnel 

assigned to the facility have access to recreational areas proximal to some of the AOIs, for 

example mountain biking trails are adjacent to AOI 4 (Little Rock Convention and Visitors 

Bureau 2022). The CSM for AOIs 1 through 6, revised based on the SI findings, is presented on 

Figures 7-1 through 7-3.

7.1 SOIL EXPOSURE PATHWAY 

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

between the source and potential receptors at AOI 1 through AOI 6 based on the aforementioned 
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criteria. AOIs 1 (Echo Pad), 3 (Building 28001 – AASF), 4 (Building 28002), and 5 (Wash Bay) 

are co-located within the Robinson Army Airfield. Due to their proximity, the above AOIs have 

been grouped under one CSM.

7.1.1 AOIs 1, 3, 4, and 5

AOIs 1, 3, 4, and 5 are within the Robinson Army Airfield area. Controlled AFFF releases 

through familiarization training have occurred at AOI 1 – Echo Pad from an unknown date. The 

most recent event using AFFF at AOI 1 was a nozzle testing exercise that occurred in November 

2018. AOIs 3, 4, and 5 were historic or current locations where storage of AFFF occurred. 

RMTC personnel reported a release of AFFF water mixture at AOI 5 after SI sampling had been 

completed (January 2022); this resulted in the removal of approximately 200 tons of soil from 

AOI 5.

PFOA, PFOS, PFHxS, PFNA, and/or PFBS were detected in surface soil associated with all four 

AOIs. Several detected concentrations exceeded SLs. Site workers, construction workers, 

trespassers (though unlikely due to restricted access), and recreational users could contact 

constituents in surface soil via incidental ingestion and inhalation of dust. Therefore, the surface 

soil exposure pathway for site workers, construction workers, trespassers, and recreational users 

is potentially complete. Public use recreational mountain biking trails are located adjacent north 

of AOIs 1,3,4, and 5 (Little Rock Convention and Visitors Bureau 2022). Additionally, PFOA, 

PFOS, PFHxS, PFNA, and/or PFBS were detected in subsurface soil associated with three of the 

four co-located AOIs. Ground-disturbing activities to subsurface soil could result in construction 

worker exposure to detected constituents via incidental ingestion. Therefore, the exposure 

pathway for subsurface soil is potentially complete for the construction worker. The CSM for 

these AOIs is presented in Figure 7-1.

7.1.2 AOI 2 

AOI 2 encompasses the gravel parking area located along the northern runway where one Little 

Rock AFB firetruck containing AFFF is typically stationed. Potential leaks from the firetruck 

may have released AFFF onto the ground. 

PFOS and PFHxS were detected in surface soil associated with AOI 2, but there were no 

exceedances of SLs in surface soils at AOI 2. Site workers and construction workers could 

contact constituents in surface soil via incidental ingestion and inhalation of dust. Therefore, the 

surface soil exposure pathway for site workers, construction workers, trespassers (though 

unlikely due to restricted access), and recreational users is potentially complete. PFOS was 

detected in subsurface soil associated with AOI 2 but there were no exceedances of SLs in 

subsurface soils at AOI 2. Ground-disturbing activities to subsurface soil could result in 

construction worker exposure to detected constituents via incidental ingestion. Therefore, the 

exposure pathway for subsurface soil is potentially complete for the construction worker. The 

CSM is presented in Figure 7-2.
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7.1.3 AOI 6 

AOI 6 encompasses Building 70200/70201, or the Fire Station. Potential leaks from the firetruck 

may have released AFFF onto the ground. 

PFOA, PFOS, PFHxS, and PFNA were detected in surface soil associated with AOI 6, with one 

PFOS SL exceedance in surface soils. Site workers, construction workers, trespassers (though 

unlikely due to restricted access), and recreational users could contact constituents in surface soil 

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

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

recreational users is potentially complete. PFOS and PFHxS were detected in subsurface soil 

associated with AOI 6, but there were no exceedances of SLs in subsurface soils at AOI 6. 

Ground-disturbing activities to subsurface soil could result in construction worker exposure to 

detected constituents via incidental ingestion. Therefore, the exposure pathway for subsurface 

soil is potentially complete for the construction worker. The CSM is presented in Figure 7-3.

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 at each AOI based on the aforementioned 

criteria. 

7.2.1 AOIs 1, 3, 4, and 5

PFOA, PFOS, PFHxS, PFNA, and/or PFBS were detected in groundwater in all temporary wells

associated with the Robinson Army Airfield source areas. Additionally, PFOA, PFOS, PFHxS, 

and/or PFNA exceeded the SLs in groundwater in multiple locations. There are no public water 

supply wells located within 5 miles of the Robinson Army Airfield. The installation and the 

majority of Central Arkansas receive potable water from Central Arkansas Water via surface 

water intakes at Lake Maumelle (URS Group, Inc. and Arcadis 2013). Groundwater is not used 

for any purposes at RMTC; however, due to the presence of groundwater at shallow occurrences, 

the exposure pathway for ingestion of groundwater is potentially complete for construction 

workers working in subsurface conditions. The exposure pathway for site workers, off-facility 

residents, and trespassers via the ingestion of groundwater is considered to be incomplete due to 

the absence of an exposure point or route to those receptors. The CSM is presented in 

Figure 7-1.

7.2.2 AOI 2 

PFOA, PFOS, PFHxS, PFNA and PFBS were detected in groundwater from temporary wells at 

the AOI 2 source area; however, there were no exceedances of the SLs for groundwater. There 

are no public water supply wells located within 5 miles of AOI 2 and the Facility and majority of 

central Arkansas receive potable water from Central Arkansas Water via surface water intakes at 

Lake Maumelle (URS Group, Inc. and Arcadis 2013). Groundwater is not used for any purposes 

at RMTC; however, due to the presence of groundwater at shallow occurrences, the exposure 

pathway for ingestion of groundwater is potentially complete for construction workers working 

in subsurface conditions. The exposure pathway for site workers, off-facility residents, and 
Site Inspection Report

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trespassers via the ingestion of groundwater is considered to be incomplete due to the absence of 

an exposure point or route to those receptors. The CSM is presented in Figure 7-2.

7.2.3 AOI 6 

PFOA, PFOS, PFHxS, PFNA and PFBS were detected in groundwater from temporary wells at 

the AOI 6. Additionally, PFOA, PFOS, and/or PFHxS concentration in groundwater exceeded 

the SLs in multiple locations. There are no public water supply wells located within 5 miles of 

AOI 6 and the Facility and majority of central Arkansas receive potable water from Central 

Arkansas Water via surface water intakes at Lake Maumelle (URS Group, Inc. and Arcadis 

2013). Groundwater is not used for any purposes at RMTC; however, due to the presence of 

groundwater at shallow occurrences, the exposure pathway for ingestion of groundwater is 

potentially complete (with an exceedance of SLs) for construction workers working in 

subsurface conditions. The exposure pathway for site workers, off-facility residents, and 

trespassers via the ingestion of groundwater is considered to be incomplete due to the absence of 

an exposure point or route to those receptors. The CSM is presented in Figure 7-3. 

7.3 SURFACE WATER AND SEDIMENT EXPOSURE PATHWAY

No surface water bodies are present within any of the AOIs. Surface water and sediment 

samples were not collected as part of this SI.

7.3.1 AOIs within the Robinson Army Airfield (AOI 1, AOI 3, AOI 4, and AOI 5)

Drainage swales and Outfalls 001 through 005 surround the outer perimeter of the Robinson 

Army Airfield, leading to neighboring tributary creeks of the Arkansas River. Swales 

surrounding the Echo Pad (AOI 1) are connected to Outfalls 004 and 005. Swales and 

stormwater collector pipes surrounding Building 28001 (AOI 3) discharge to Outfall 002 

(draining northwest of the building) and Outfall 001 (draining the paved areas surrounding the 

building). Building 28002 (AOI 4) and the Wash Bay (AOI 5) are also connected to Outfall 001. 

Outfalls 001, 002, and 004 drain to Newton Creek and White Oak Bayou before intersecting with 

the Arkansas River, located 14 miles away. Outfall 005 drains to Spring Creek, Miles Creek, 

Kellogg Creek, and Bayou Meto before intersecting with the Arkansas River. Outfall 003, which 

collects surface water runoff to the south from the surrounding paved areas, drains to Fivemile 

Creek, Brushy Island Creek, and Bayou Meto.

Temporary well location RMTC-01 is located proximal to Outfall 001. The PFOS concentration 

at RMTC-01 was reported above the SL. The PFOS concentration in the sample collected from 

RMTC-02 (upgradient and proximal to Outfall 003) was also in excess of the SL. Sample 

RMTC-03 was collected proximal and up gradient to Outfall 002. PFOA, PFOS, PFHxS, and 

PFNA concentrations were reported in excess of the SL at this location. Outfalls 001 and 002 

drain to Newton Creek and White Oak Bayou before intersecting with the Arkansas River, 

located 14 miles away. Outfall 003 drains to Fivemile Creek, then to Bushy Island Creek, to 

Bayou Meto, and the Arkansas River. Site workers, construction workers, off-facility residents, 

and recreational users of the Arkansas River or its tributaries may be exposed to PFAS in surface 

water and sediment via ingestion. 
Site Inspection Report

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PFOS, PFOA, PFHxS, PFNA, PFBS were detected in surface soils at AOIs 1, 3, 4, and 5, with

three reported exceedances of the residential SL for PFOS in soil and one reported exceedance of 

the residential SL for PFNA in soil. Additionally, soil samples were collected in drainage swales 

leading to Outfalls 001, 002, and 003; PFOS, PFOA, PFHxS, and/or PFNA were detected in 

surface soils at all three locations; therefore, relevant compounds may be captured in surface 

water runoff. Site workers, construction workers, off-facility residents, and onsite recreational 

users, trespassers, and recreational users of the Arkansas River or its tributaries may be exposed 

to PFAS in surface water and sediment via ingestion. Additionally, recreational fishing of these 

waterbodies may potentially present another exposure pathway to PFAS via ingestion of 

contaminated fish. Public mountain biking trails are located adjacent north of AOIs 1,3,4 and 5.

These trails cross drainage pathways located downgradient of outfalls 001, 002, and 004 and 

therefore provide direct exposure to surface water and sediment for trail users. No surface water 

or sediment sampling was conducted at RMTC; however, based on SI sampling, the pathways 

for these receptors are considered potentially complete. 

7.3.2 AOI 2 

PFOS and PFHxS was detected in surface soil at AOI 2. Relevant compounds may be captured 

in surface water runoff. AOI 2 is located within the Upper Bayou Meto Watershed. Surface 

water drains southeasterly, eventually reaching the Arkansas River. No surface water or sediment 

sampling was conducted at RMTC; therefore, the exposure pathways for site workers, 

construction workers, off-facility residents, and recreational users of the Arkansas River and its 

tributaries via ingestion of surface water and sediment are considered potentially complete.

Additionally, recreational fishing of these waterbodies may potentially present another exposure 

pathway to relevant compounds via ingestion of contaminated fish. 

7.3.3 AOI 6 

PFOS was detected in surface soil in excess of the SL. Surface water runoff at AOI 6 drains by 

sheet flow into nearby swales, diverting the water south to an unnamed ephemeral stream and 

eventually discharging into Shilcotts Bayou and the Arkansas River at Greathouse Bend. Site 

workers, construction workers, off-facility residents, and recreational users of the Arkansas River 

or its tributaries may be exposed to PFAS in surface water and sediment via ingestion. 

Additionally, recreational fishing of these waterbodies may potentially present another exposure 

pathway to PFAS via ingestion of contaminated fish. No surface water or sediment sampling was 

conducted at RMTC; therefore, the pathways for these receptors are considered potentially 

complete.
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Notes:

1. The resident and recreational users refer to 

on-site and off-site receptors.

2. Human consumption of fish potentially 

affected by PFAS is possible.

3. Inhalation of dust for off-site receptors is 

likely insignificant.

Figure 7-1

Conceptual Site Model

RMTC AOIs 1, 3, 4, and 5

RECEPTOR

Human Receptors:

Current/Future

Site 

Worker

Construction 

Worker

Resident1

Site 

Worker

Construction 

Worker

Resident1

Robinson 

Army 

Airfield 

AOIs 1, 3, 4, 

and 5

PFAS in 

Surface 

Soil

Human 

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne 

Soil 

Particulate

Surface Soil 

at AOI

Surface 

Water/ 

Sediment

Subsurface 

Soil

Shallow 

Groundwater

Ingestion

Ingestion

Ingestion

Ingestion

Potential AFFF 

Release

SOURCE

Source Release 

Mechanism Media

PATHWAY

Transport

and Migration Media Exposure 

Routes

Inhalation 

of Dust

Potentially Complete Pathway with Exceedance of 

Screening Level

Trespasser/

Recreational User1,2

Trespasser/

Recreational User1,2
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2012 This page intentionally left blank
Notes:

1. The resident and recreational users refer to 

on-site and off-site receptors.

2. Human consumption of fish potentially 

affected by PFAS is possible.

3. Inhalation of dust for off-site receptors is 

likely insignificant.

Figure 7-2

Conceptual Site Model

RMTC AOI 2 –

All American Landing/Drop Zone

RECEPTOR

Human Receptors:

Current/Future

Site 

Worker

Construction 

Worker

Resident1

Site 

Worker

Construction 

Worker

Resident1

AOI 2 –

All 

American 

Landing/

Drop 

Zone

PFAS in 

Surface 

Soil

Human 

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne 

Soil 

Particulate

Surface Soil 

at AOI

Surface 

Water/ 

Sediment

Subsurface 

Soil

Shallow 

Groundwater

Ingestion

Ingestion

Ingestion

Ingestion

Potential AFFF 

Release

SOURCE

Source Release 

Mechanism Media

PATHWAY

Transport

and Migration Media Exposure 

Routes

Inhalation 

of Dust

Potentially Complete Pathway with Exceedance of 

Screening Level

Trespasser/

Recreational User1,2

Trespasser/

Recreational User1,2
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2015 This page intentionally left blank
Notes:

1. The resident and recreational users refer to 

on-site and off-site receptors.

2. Human consumption of fish potentially 

affected by PFAS is possible.

3. Inhalation of dust for off-site receptors is 

likely insignificant.

Figure 7-3

Conceptual Site Model

RMTC AOI 6 – Fire Station

RECEPTOR

Human Receptors:

Current/Future

Site 

Worker

Construction 

Worker

Resident1

Site 

Worker

Construction 

Worker

Resident1

AOI 6 –

Fire 

Station

PFAS in 

Surface 

Soil

Human 

Activities

Precipitation/

Run-Off

Leaching/

Infiltration

Airborne 

Soil 

Particulate

Surface Soil 

at AOI

Surface 

Water/ 

Sediment

Subsurface 

Soil

Shallow 

Groundwater

Ingestion

Ingestion

Ingestion

Ingestion

Potential AFFF 

Release

SOURCE

Source Release 

Mechanism Media

PATHWAY

Transport

and Migration Media Exposure 

Routes

Inhalation 

of Dust

Potentially Complete Pathway with Exceedance of 

Screening Level

Trespasser/

Recreational User1,2

Trespasser/

Recreational User1,2
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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 SITE INSPECTION ACTIVITIES SUMMARY 

The SI field activities at the Facility were conducted from 18 to 29 October 2021. The SI field 

activities included soil and groundwater sampling. Field activities were conducted in accordance 

with the UFP-QAPP Addendum (EA 2021a), except as previously noted in Section 5.8. 

To fulfill the project DQOs set forth in the approved SI UFP-QAPP Addendum (EA 2021a), 

samples were collected and analyzed for a subset of 24 compounds by LC/MS/MS compliant 

with QSM Version 5.3 Table B-15 as follows:

• Sixty-seven (67) soil samples from 28 boring locations

• Twenty-five (25) grab groundwater samples from 26 temporary well locations (one 

location was dry)

• Seven (7) FBs

• Fifteen (15) equipment rinsate samples

• Nine (9) FD 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 in the form of a RI is warranted for AOIs 1 (the 

Echo Pad), 3 (Building 28001), 4 (Building 28002), 5 (the Wash Bay), and 6 (the Fire Station)

and further evaluation is not warranted for AOI 2 (All American Landing/Drop Zone). Sample 

chemical analytical concentrations collected during this SI were compared against the project 

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

• AOI 1:

⎯ PFOS in surface soil exceeded the SL of 13 μg/kg in two locations in AOI 1 with a 

maximum concentration of 190 g/kg. PFNA in surface soil exceeded the SL of 19 

g/kg in one location with a concentration of 20 g/kg. The detected concentrations 

of PFOA, PFHxS, and PFBS in soil at AOI 1 were below their respective SLs.

⎯ PFOA, PFOS, PFHxS, PFNA and PFBS were detected in all seven temporary well

locations at AOI 1. PFOA detections in groundwater exceeded the SL of 6 ng/L in six

temporary well locations associated with AOI 1, with a maximum concentration of 

540 ng/L. At the 7th temporary well location, the primary sample was below the SL 

but the duplicate sample exceeded the SL. PFOS detections in groundwater exceeded 

the SL of 4 ng/L in all seven temporary well locations associated with AOI 1, with a 

maximum concentration of 3,000 J+ ng/L. PFNA detections in groundwater exceeded 

the SL of 6 ng/L in five of the seven temporary well locations with a maximum 

concentration of 770 ng/L. PFHxS detections in groundwater exceeded the SL of 39 

ng/L in six of seven temporary well locations associated with AOI 1, with a 

maximum concentration of 1,000 ng/L. Based on the results of the SI, further 

evaluation of AOI 1 is warranted.

• AOI 2:

⎯ The detected concentrations of PFOS and PFHxS in soil at AOI 2 were below their 

respective SLs.

⎯ PFOA, PFOS, PFHxS, PFNA and PFBS were detected at low levels in groundwater 

at AOI 2; however, there were no exceedances of the SLs in groundwater. Based on 

the results of the SI, no further evaluation of AOI 2 is warranted. 

• AOI 3:

⎯ The detected concentrations of PFOA, PFOS, and PFNA in soil at AOI 3 were below 

their respective SLs.

⎯ PFOA detections in groundwater exceeded the SL of 6 ng/L in one temporary well 

location associated with AOI 3, with a concentration of 8.4 ng/L. PFOS detections in 

groundwater exceeded the SL of 4 ng/L in one temporary well location associated 

with AOI 3, with a concentration of 5.3 ng/L. The detected concentrations of PFHxS, 

PFNA and PFBS in groundwater at AOI 3 were below their respective SLs. Based on 

the results of the SI, further evaluation of AOI 3 is warranted.
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• AOI 4:

⎯ The detected concentrations of PFOA and PFOS in soil at AOI 4 were below their 

respective SLs.

⎯ PFOA, PFOS, PFHxS, PFNA and PFBS were detected in groundwater at AOI 4, with 

PFOA exceeding the SL of 6 ng/L in one of two temporary well locations, and PFOS 

exceeding the SL of 4 ng/L in both temporary well locations. Based on the results of 

the SI, further evaluation of AOI 4 is warranted.

• AOI 5:

⎯ PFOS in surface soil exceeded the SL of 13 μg/kg in one location in AOI 5 with a 

concentration of 23 g/kg. The detected concentrations of PFOA, PFHxS, PFNA and 

PFBS in soil at AOI 5 were below their respective SLs.

⎯ PFOA, PFOS, PFHxS, PFNA and PFBS were detected in groundwater at AOI 5. At 

one location, PFOA, PFOS, and PFHxS detections exceeded their SLs of 6 ng/L, 4 

ng/L, 39 ng/L, respectively. RMTC personnel reported a recent release of AFFF

(January 2022) resulting in the removal of approximately 200 tons of soil from the 

northern portion of the building at AOI 5. Based on the results of the SI, further 

evaluation of AOI 5 is warranted.

• AOI 6:

⎯ The detected concentrations of PFOA, PFHxS, PFNA, and PFBS in soil at AOI 6

were below their respective SLs. PFOS in surface soil exceeded the SL of 13 μg/kg in 

one location in AOI 6 with a concentration of 410 g/kg.

⎯ PFOA, PFOS, PFHxS, PFNA and/or PFBS were detected in all four temporary well 

locations at AOI 6. PFOS detections in groundwater exceeded the SL of 4 ng/L in 

three of the four temporary well locations associated with AOI 6, with a maximum 

concentration of 120 ng/L. PFOA detections in groundwater exceeded the SL of 

6 ng/L in one location with a concentration of 14 ng/L. PFHxS detections in 

groundwater exceeded the SL of 39 ng/L in one location associated with AOI 6, with 

a concentration of 310 ng/L. Based on the results of the SI, further evaluation of AOI 

6 is warranted. 

• Additional Facility Sample Locations:

⎯ PFOA, PFOS, PFHxS, and PFNA were detected in soil at the additional sample 

locations at concentrations below their respective SLs.

⎯ PFOA, PFOS, PFHxS, PFNA and/or PFBS were detected in groundwater associated 

with drainage pathways (swales and stormwater collector pipes) exiting the Robinson 

Army Airfield (RMTC-01, RMTC-02, and RMTC-03). These locations receive 
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runoff from AOIs 1, 3, 4, and 5. PFOA detections in groundwater exceeded the SL of 

6 ng/L in one of the three temporary well locations, with a maximum concentration of 

190 ng/L. PFOS detections in groundwater exceeded the SL of 4 ng/L in all three 

temporary well locations, with a maximum concentration of 1,000 ng/L. PFNA 

detections in groundwater exceeded the SL of 6 ng/L in one of the three temporary 

well locations, with a concentration of 31 ng/L. PFHxS detections in groundwater 

exceeded the SL of 39 ng/L in one of the three temporary well locations, with a 

concentration of 230 ng/L. These results indicate that relevant compounds from AOIs 

1, 3, 4, and 5 are migrating away from source areas at concentrations exceeding 

respective SLs. These results also confirm/support the conclusion that further 

evaluation of AOIs, 1, 3, 4, and 5 are warranted.

Temporary wells were constructed using open boreholes which may allow surficial soil to enter 

the temporary well or annular space and contact groundwater. This has the potential for biasing 

groundwater data high where contaminated soil may have infiltrated the zone sampled.

Consistent correlation between elevated soil values and groundwater results was not observed 

across SI data.

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 Echo Pad NA Proceed to RI

2

All American Landing/Drop 

Zone NA No further action

3 Building 28001 NA Proceed to RI

4 Building 28002 NA Proceed to RI

5 Wash Pad NA Proceed to RI

6 Building 70200/70201 NA Proceed to RI

Legend:

 = Detected; exceedance of SLs

 = Detected; no exceedance of SLs

 = Not detected
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9. REFERENCES

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Robinson Maneuver Training Center, North Little Rock, Arkansas. March.

Amec Foster Wheeler Programs, Inc. 2019. Final Site Inspection Report, Site Inspection of 

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Jacksonville, Arkansas. June.

Arkansas Geological Survey, 2011. 

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Department of the Army. 2016. EM-200-1-2, Environmental Quality, Technical Project 

Planning Process. 29 February.

Department of Defense (DoD). 2019a. Department of Defense (DoD), Department of Energy

(DOE) Consolidated Quality Systems Manual (QSM) for Environmental Laboratories,

Version 5.3. May.

⎯⎯⎯. 2019b. General Data Validation Guidelines. November.

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Polyfluoroalkyl Substances Analysis by QSM Table B-15. May.

EA Engineering, Science, and Technology, Inc., PBC (EA). 2020a. Final Programmatic 

Uniform Federal Policy Quality Assurance Project Plan, Site Inspections for Per- and 

Polyfluoroalkyl Substances Impacted Sites, ARNG Installations, Nationwide. December.

⎯⎯⎯. 2020b. Final Programmatic Accident Prevention Plan, Revision 1. November.

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(UFP-QAPP) Addendum, Robinson Maneuver Training Center, North Little Rock, Arkansas, 

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October.

⎯⎯⎯. 2021b. Final Accident Prevention Plan / Site Safety and Health Plan Addendum, 

Robinson Maneuver Training Center, North Little Rock, Arkansas. August.

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Camp Joseph T. Robinson. September.

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https://suttoncenter.org/research/ok-bird-atlases-surveys/other-site-surveys/camp-robinson/ . 

Accessed on 9 August. 
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EA Engineering, Science, and Technology, Inc., PBC 9-2

Guelfo, J.L. and C.P. Higgins. 2013. Subsurface transport potential of perfluoroalkyl acids and 

aqueous film-forming foam (AFFF)-impacted sites. Environ. Sci. Technol. 47(9):4164-71. 

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

Environ. Sci. Technol. 40(23):7251-7256. 

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McFarland, J.D., 2004. Arkansas Geological Commission. Stratigraphic Summary of Arkansas.

National Weather Service, 2019. Climatological Averages, Statistics and Records for North 

Little Rock, Arkansas. https://www.weather.gov/media/lzk/clilzk.pdf. Accessed August 

2019.

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Polyfluoroalkyl Substances within The Department of Defense Cleanup Program. United 

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Management Plan: FY2002-FY2006. September.

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Response, Compensation, and Liability Act (CERCLA). 11 December.

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

40 Code of Federal Regulations Part 300; 59 Federal Register 47384. September.

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

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

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

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URS Group, Inc. and Arcadis. 2013. Operational Range Assessment Phase II Report, Robinson 

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on 14 February. 
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Xiao, F., M. F. Simcik, T.R. Halbach, and J.S Gulliver. 2015. Perfluorooctane sulfonate (PFOS) 

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

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