FINAL

Site Inspection Report 

Ellington Field Army Aviation 

Support Facility

Houston, Texas

Site Inspection for Perfluorooctanoic acid (PFOA), 

Perfluorooctanesulfonic acid (PFOS), Perfluorohexanesulfonic 

acid (PFHxS), Perfluorononanoic acid (PFNA), 

Hexafluoropropylene oxide dimer acid (HFPO-DA), and 

Perfluorobutanesulfonic acid (PFBS) at ARNG Installations, 

Nationwide 

September 2023 

Prepared for:

Army National Guard Bureau

111 S. George Mason Drive

Arlington, VA 22204

UNCLASSIFIED

Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM i

Table of Contents

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

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

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

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

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

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

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

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

2.2.2 Hydrogeology ............................................................................................... 2-1

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

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

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

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

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

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

3.1 AOI 1 Wash Rack ................................................................................................... 3-1

3.2 AOI 2 Flight Line ..................................................................................................... 3-1

3.3 Adjacent Sources.................................................................................................... 3-2

3.3.1 TXANG Old Fire Station ............................................................................... 3-2

3.3.2 TXANG New Fire Station.............................................................................. 3-2

3.3.3 TXANG Aircraft Parking Apron ..................................................................... 3-2

3.3.4 TXANG Hangars 1382 and 1394.................................................................. 3-3

3.3.5 Stormwater Discharge Outfalls..................................................................... 3-3

3.3.6 NASA ............................................................................................................ 3-3

3.3.7 Brio Superfund Site ...................................................................................... 3-3

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

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

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

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

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

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

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

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

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

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

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

5.2 Soil Borings and Soil Sampling............................................................................... 5-2

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

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

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

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

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

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

6. Site Inspection Results................................................................................................... 6-1
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6.1 Screening Levels .................................................................................................... 6-1

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

7.3 Surface Water and Sediment Exposure Pathway................................................... 7-3

7.3.1 AOI 1 ............................................................................................................ 7-3

7.3.2 AOI 2 ............................................................................................................ 7-3

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

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

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

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

Appendix A Data Usability Assessment and Validation Reports

Appendix B Field Documentation

B1. Log of Daily Notice of Field Activities

B2. Sampling Forms

B3. Survey Data

B4. Nonconformance and Corrective Action Report

Appendix C Photographic Log

Appendix D TPP Meeting Minutes

Appendix E Boring Logs

Appendix F Analytical Results

Appendix G Laboratory Reports

Figures

Figure 2-1 Facility Location

Figure 2-2 Facility Topography

Figure 2-3 Groundwater Features

Figure 2-4 Groundwater Elevations, June 2022

Figure 2-5 Surface Water Features

Figure 3-1 Areas of Interest

Figure 5-1 Site Inspection Sample Locations 

Figure 6-1 PFOA Detections in Soil

Figure 6-2 PFOS Detections in Soil

Figure 6-3 PFBS Detections in Soil

Figure 6-4 PFHxS Detections in Soil

Figure 6-5 PFNA Detections in Soil

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

Figure 6-7 PFHxS and PFNA Detections in Groundwater

Figure 7-1 Conceptual Site Model, AOI 1 and AOI 2

Tables

Table ES-1 Screening Levels (Soil and Groundwater)

Table ES-2 Summary of Site Inspection Findings and Recommendations

Table 5-1 Site Inspection Samples by Medium

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

Elevations

Table 6-1 Screening Levels (Soil and Groundwater)

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

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

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

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

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

% percent

°C degrees Celsius

°F degrees Fahrenheit

μg/kg micrograms per kilogram

AASF Army Aviation Support Facility

AECOM AECOM Technical Services, Inc.

AFFF aqueous film-forming foam

AOI Area of Interest

ARNG Army National Guard

ASTM American Society for Testing and Materials

bgs below ground surface 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CoC chain of custody

CSM conceptual site model

DA Department of the Army

DoD Department of Defense

DOT Department of Transportation

DPT direct push technology

DQO data quality objective 

DUA data usability assessment

ELAP Environmental Laboratory Accreditation Program

EM Engineer Manual

ERB equipment rinsate blank

FedEx Federal Express

GCAS Gulf Coast Aquifer System

GPRS Ground Penetrating Radar Systems, LLC

HDPE high-density polyethylene 

HFPO-DA hexafluoropropylene oxide dimer acid

IDW investigation-derived waste

ITRC Interstate Technology Regulatory Council

JRB Joint Reserve Base

LC/MS/MS liquid chromatography with tandem mass spectrometry

MIL-SPEC military specification

NASA National Aeronautics and Space Administration

NELAP National Environmental Laboratory Accreditation Program

ng/L nanograms per liter

OSD Office of the Secretary of Defense

OWS oil/water separator

PA Preliminary Assessment

PFAS per- and polyfluoroalkyl substances

PFBS perfluorobutanesulfonic acid

PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid
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PFOA perfluorooctanoic acid

PFOS perfluorooctanesulfonic acid

PID photoionization detector

PQAPP Programmatic UFP-QAPP

PVC polyvinyl chloride

QA quality assurance

QAPP Quality Assurance Project Plan

QC quality control

QSM Quality Systems Manual

SI Site Inspection

SL screening level

SOP standard operating procedure

TOC total organic carbon

TPP Technical Project Planning

TXANG Texas Air National Guard

TXARNG Texas Army National Guard

UFP Uniform Federal Policy

US United States

USACE United States Army Corps of Engineers

USCS Unified Soil Classification System

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service
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Executive Summary

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

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

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

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

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

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

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

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

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

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

used, stored, disposed, or released historically (see Table ES-2). The objective of the SI is to 

identify whether there has been a release to the environment from the AOIs identified in the PA 

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

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

was completed at the Ellington Field Army Aviation Support Facility (AASF) in Houston, Texas and 

determined further evaluation under the Comprehensive Environmental Response, 

Compensation, and Liability Act (CERCLA) is warranted for AOI 1 and AOI 2. The Ellington Field

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

Ellington Field AASF occupies the northwest corner of the Ellington Field Joint Reserve Base in 

Houston, Texas. In 1976, Ellington Field Joint Reserve Base was officially inactivated, however, 

Texas ARNG and other military branches still maintain a military presence at the base. The 

Ellington Field airfield is jointly used by the Department of Defense and private parties (AECOM 

Technical Services, Inc., 2020). 

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

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

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

(RI) for AOI 1 and AOI 2. 

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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Ellington Field Army Aviation Support Facility, Houston, Texas

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

Analyteb

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ Commercial 

Composite Worker

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater) 

(ng/L)a

PFOA 19 250 6 

PFOS 13 160 4 

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6 

Notes:

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

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

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

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

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

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

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

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

AOI

Potential 

Release 

Area

Soil – 

Source Area

Groundwater – 

Source Area

Groundwater –

Facility 

Boundary

Future Action

1 Wash Rack Proceed to RI 

2 Flight Line N/A Proceed to RI

Legend:

N/A = not applicable

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected

1 
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Ellington Field Army Aviation Support Facility, Houston, Texas

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1. Introduction

1.1 Project Authorization 

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

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

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

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

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

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

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

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

acid (PFBS) at ARNG facilities nationwide. The ARNG performed this SI at the Ellington Field

Army Aviation Support Facility (AASF) in Houston, Texas. The Ellington Field AASF is also

referred to as the “facility” throughout this document. 

The SI project elements were performed in compliance with Comprehensive Environmental 

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

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

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

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

investigations. 

1.2 SI Purpose

A PA was performed at Ellington Field AASF (AECOM Technical Services, Inc. [AECOM], 2020) 

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

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

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

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

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

1

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

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

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

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

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

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

2.1 Facility Location and Description 

Ellington Field AASF occupies 17.6 acres of the northwest corner of the Ellington Field Joint 

Reserve Base (JRB), which was built in the 1970s. Ellington Field AASF is located in Harris 

County, Texas, approximately 16 miles southeast of downtown Houston and 11 miles west of 

Trinity Bay (Figure 2-1). Ellington Field AASF is home to the 149th Attack Reconnaissance 

Battalion of the Texas ARNG (TXARNG). The southern portion of Ellington Field JRB has been 

leased to the National Aeronautics and Space Administration (NASA) by the City of Houston. The 

Ellington Field JRB airfield is jointly used by Department of Defense (DoD) and private parties 

(147 CES/CEV, 2013). Ellington Field JRB was officially deactivated by the Air Force in 1976, and 

all Air Force Reserve squadrons were transferred to other military facilities; however, the 

TXARNG, Texas Air National Guard (TXANG), US Army Reserve, US Navy Reserve, US Marine 

Corps Reserve, US Coast Guard, and the Civil Air Patrol still maintain a military presence at the 

JRB. In 2009, the Air Force issued a permit with a term expiring in 2039 for the TXARNG’s use of 

land and facilities at Ellington Field Air National Guard Base. 

2.2 Facility Environmental Setting

Ellington Field AASF is located in south-eastern Texas, approximately 32 miles northwest of the 

Gulf of Mexico. The facility is situated near Horsepen Bayou, which feeds into Clear Lake, which 

then flows into Trinity Bay and Galveston Bay. The topography of the facility is relatively flat with 

an elevation of approximately 35 feet above mean sea level (Figure 2-2). There are no significant 

natural topographic features surrounding the facility. 

2.2.1 Geology

The Houston area is located in the Gulf Coast Plain physiographic province, which includes fluvial, 

fluvial-deltaic, barrier-strand plain, and bay-estuary lagoon depositional environments. The 

geology directly underlying the City of Houston and Harris County consist primarily of the 

Pleistocene-aged Beaumont Formation and more recent Quaternary alluvium along surface water 

channels (Figure 2-3). The Beaumont Formation is a poorly bedded, calcareous clay that 

contains discontinuous stringers and beds of silt and fine-grained sand. The Beaumont Formation 

ranges in total thickness from about 500 feet in Harris County to about 700 feet near Galveston 

(Leidos, 2018). 

During the SI, low to medium plasticity clay was observed as the dominant lithology of the 

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

between 15 and 25 feet below ground surface (bgs). Varying quantities of silt were noted in the 

clay layers, ranging from zero percent (%) to 40% silt. Isolated layers of silty sand and sandy silt 

were also observed with thicknesses ranging from 2 to 3.5 feet. Samples for grain size analysis 

were collected at two locations, AOI01-01 and AOI02-01, from 0 to 2 feet bgs 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 (50.11% to 54.20%), clay (21.37% to 21.51%), and 

fine sand (21.59% to 23.88%). These results and facility observations are consistent with the 

Beaumont Formation. Boring logs are presented in Appendix E and grain size results are 

presented in Appendix F. 

2.2.2 Hydrogeology

The Gulf Coast Aquifer System (GCAS) is the primary hydrogeologic unit in the Gulf Coast Plain 

physiographic province. The GCAS consists of interbedded clays, silts, sands, and gravels of 
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Cenozoic age, which are hydrologically connected to form a large, leaky, artesian aquifer system. 

This system comprises four units separated by different sedimentary, water-producing formations. 

The deepest formation is the Catahoula confining system, which contains groundwater near the 

outcrop in relatively restricted sand layers. Above the Catahoula is the Jasper aquifer, which is 

primarily contained within the Oakville Sandstone and the Fleming Formation. The Burkeville 

confining layer separates the Jasper aquifer from the overlying Evangeline aquifer, which is 

contained within the Goliad Sand. The Chicot aquifer is the uppermost unit of the GCAS and is 

composed of (from stratigraphically youngest to oldest) alluvial deposits, the Beaumont 

Formation, the Bentley and Montgomery formations (often grouped together as the Lissie 

Formation), and the Willis Sand. Not all formations are present throughout the system, and 

nomenclature often differs from one end of the system to the other. Maximum total sand thickness 

ranges from 700 feet in the south to 1,300 feet in the northern extent. 

The facility’s drinking water is supplied by the City of Houston. A query of the Texas Water 

Development Board Submitted Driller’s Reports and Groundwater Database identified 4 industrial 

wells, 32 monitoring wells, 4 public supply wells, and 1 domestic well within a 1-mile radius of the 

facility. The industrial water supply wells range in depth from 376 to 555 feet bgs. The monitoring 

wells range in depth from 15 to 90 feet bgs. The public supply wells range in depth from 391 to 

583 feet bgs, and the depth of the domestic well is 548 feet bgs. Using additional online resources, 

such as state and local Geographic Information System databases, wells were researched to a 

4-mile radius of the facility. In the 1 to 4-mile radius, an additional public supply well, 10 domestic

wells, 4 irrigation wells, 1 industrial well, 16 injection wells, and 373 monitoring wells were

identified. Wells surrounding the facility are shown on Figure 2-3.

Depths to water measured in June 2022 during the SI ranged from 4.14 to 8.67 feet bgs. 

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

groundwater flow direction at Ellington Field AASF is to the southeast. 

2.2.3 Hydrology

No natural or significant surface water bodies, navigable waterways, or wetlands are present at 

the facility (Leidos, 2018). Armand Bayou is located approximately 4.5 miles east of the facility, 

and the Houston Ship Channel is located approximately 9 miles north of the facility. Surface water 

flow at the facility is dictated by the facility’s constructed surface drainage system, which is shared 

by TXARNG and TXANG, as well as other occupants located at Ellington Field JRB. The system 

contains multiple ditches/channels for surface flow. The stormwater pollution prevention plan for 

TXANG 147 RW Ellington Field details six surface water drainage areas that drain to their 

respective stormwater discharge outfalls. Most of Ellington Field AASF is located within Drainage 

Basin 001; however, the Flight Line is within Drainage Basin 005. Surface water within Drainage 

Basin 001 flows through ditches/channels and underground pipes, ultimately to two box culverts 

via Stormwater Discharge Outfall 001. Surface water within Drainage Basin 005 flows through a 

series of catch basins and underground pipes which convey south through Stormwater Discharge 

Outfall 005 (a drop inlet structure beneath the aircraft parking apron; Cardno TEC, 2015). From 

the stormwater discharge outfalls stormwater moves by open channel flow and underground 

drainage pipes until the runoff reaches Horsepen Bayou, located approximately 2 miles southeast 

of the facility. Horsepen Bayou flows to the east and eventually combines with Armand Bayou 

(Figure 2-5) (Leidos, 2018). 

2.2.4 Climate

Houston has a humid subtropical climate, with long, hot, and humid summers and short, mild 

winters. Houston’s proximity to large water bodies brings in warm air for much of the year. Houston 

occasionally faces severe tornadoes, thunderstorms, hurricanes, and tropical storms. The 

average high temperature in Houston reaches 95 degrees Fahrenheit (°F) at the peak of August. 
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Winters are mild to cool with the average daily high temperature above 60°F. Average annual 

precipitation is 51 inches, with even distribution over the year (National Weather Service, 2023). 

2.2.5 Current and Future Land Use

The facility currently includes a hangar, wash rack, paved vehicle parking areas, aircraft and 

equipment parking areas, and supporting facilities such as sidewalks and administrative buildings. 

The hangar (Building 1183) is used to service army aviation vehicles such as helicopters. East of 

the hangar is the TXARNG aircraft parking area, where aircraft are parked and minor maintenance 

is performed, and further east of the aircraft parking area is the flight line. South of the hangar is 

a wash rack. The facility shares its northern boundary with the Ellington JRB fire station which is 

operated by TXANG. During the SI, the northern property boundary was corrected as shown in 

Figure 2-1 through Figure 6-7. 

Current land use directly adjacent to Ellington Field AASF is comprised of Ellington Field JRB 

buildings, airfields, and properties in all directions. Beyond the JRB land use includes industrial 

to the north, residential development to the east, a mixture of undeveloped, commercial, and 

residential areas to the south, and a municipal golf course and an oil & gas company to the west. 

The nearest residence is approximately 0.9 miles northeast of the facility, surrounded by a 

commercial nursery and south of Clean Harbors Environmental. The nearest residential 

development is approximately 1 mile west-southwest of the facility. 

2.2.6 Sensitive Habitat and Threatened/ Endangered Species 

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

or are listed as candidate species in Harris County, Texas (US Fish and Wildlife Service [USFWS], 

2022). 

• Birds: Whooping crane, Grus americana (endangered); Red knot, Calidris canutus rufa

(threatened); Eastern Black rail, Laterallus jamaicensis ssp. jamaicensis (threatened)

• Flowering Plants: Texas prairie dawn-flower, Hymenoxys texana (endangered)

• Mammals: West Indian Manatee, Trichechus manatus (threatened);

2.3 History of PFAS Use 

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

disposed, or released historically at the Ellington Field AASF (AECOM, 2020). AFFF may have 

historically been released at the facility during familiarization training and fire training activities as 

early as 1990. Additionally, Tri-MaxTM fire suppression units were stored along the Flight Line and 

in 2007 were used to extinguish an aircraft fire on the Flight Line. The potential release areas 

were identified as AOI 1 and AOI 2, based on preliminary data, and a description of each AOI is 

presented in Section 3. 
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PROJECT Site Inspection at Ellington Field, TX

1:63,360

12/2/2022 ­ Figure 2-1

PM CM 12/2/2022

12420 Milestone Center Drive

Germantown, MD 20876

Facility Location

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

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

Legend

Approximate Corrected Facility Boundary

Facility Boundary

0 0.5 1 2

Miles

^_

Ellington Field

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PROJECT Site Inspection at Ellington Field, TX

1:6,000

12/2/2022 ­ Figure 2-2 PM CM 12/2/2022

12420 Milestone Center Drive

Germantown, MD 20876

Facility Topography

Base Map: USGS The National Map: National

Boundaries Dataset, 3DEP Elevation Program,

Legend

Approximate Corrected Facility Boundary

Facility Boundary

0 250 500 1,000

Feet

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Ellington Field Army Aviation Support Facility, Houston, Texas

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Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 3-1

3. Summary of Areas of Interest

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

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

identified at Ellington Field AASF and designated as AOI 1 and AOI 2 (AECOM, 2020). The 

potential release areas are shown on Figure 3-1. 

3.1 AOI 1 Wash Rack

Starting in the early 1990s, TXARNG personnel trained with one or two Tri-MaxTM units once a 

year with the TXANG fire department at the Wash Rack (AOI 1) or the Flight Line (AOI 2). The 

fire training consisted of Ellington Field AASF personnel extinguishing flames from a metal burn 

box that was set on fire. The Tri-MaxTM units were disposed of between 2007 and 2009 due to 

deteriorating hoses. Around 2010, AFFF at the facility was donated to the TXANG fire department, 

and Tri-MaxTM units were replaced with Purple K units. TXARNG personnel onsite since 1986 

were not aware of any bulk AFFF stored at the facility. No bulk AFFF was discovered on-site 

during an annual building inspection conducted by the TXANG fire chief in 2010 (AECOM, 2020). 

Releases at the Wash Rack may have been conveyed to the oil/water separator (OWS), then 

flowed to the sanitary sewer system, and ultimately discharged to the Metro Central Waste 

Treatment Facility, located approximately 1.8 miles south of the facility. Underground 

conveyances to the OWS, as well as the OWS itself, may have leaks that released AFFF to the 

subsurface. It is also possible that releases at the Wash Rack were conveyed directly into the 

stormwater system, due to a malfunctioning diverter valve in the Wash Rack system. It has been 

noted by facility personnel that this diverter valve has malfunctioned historically; therefore, it is 

not certain which direction potential releases may have drained. During training exercises, AFFF 

may have migrated from the paved Wash Rack area to the grassy areas south of the Wash Rack 

and infiltrated into soil. Runoff could also have caused AFFF to migrate to the ditch to the east of 

the Wash Rack, where it would eventually discharge through Stormwater Discharge Outfall 001 

at the southern end of the facility. Once inside the box culverts, the stormwater flow continues 

south, until the runoff reaches Horsepen Bayou (BB&E, Inc., 2016). 

3.2 AOI 2 Flight Line

AOI 2 is the Flight Line and is located on the eastern portion of the facility. TXARNG personnel 

practiced with one or two Tri-MaxTM units once a year with the TXANG fire department at the 

Wash Rack or the Flight Line. During fire training, a metal burn box was set on fire, and Ellington 

Field AASF personnel would practice putting it out. 

Tri-MaxTM units were on-site in the early 1990s and were stationed along the Flight Line. Initially, 

Ellington Field AASF personnel were responsible for maintaining the Tri-MaxTM units, but that 

responsibility was later given to the TXANG fire department, and then to a third-party contractor. 

At peak operation (before 1995), there were between 30 to 40 helicopters on-site. Historically, 

there was one Tri-MaxTM fire extinguisher staged between every two helicopters stored on the 

Flight Line. The PA Report indicated that the Tri-MaxTM units rusted frequently and repairs and 

hydrostatic testing were performed on the units by an outside contractor. These repairs and tests 

occurred off-site (AECOM, 2020). Additionally, in 1997 an aviation ground power unit caught on 

fire on the Ellington Field AASF Flight Line, and Tri-MaxTM units were used to extinguish the flame. 

AFFF released on the Flight Line would likely flow to Stormwater Discharge Outfall 005, which is 

located within the Flight Line. TXANG sampled surface water from Stormwater Discharge Outfall 

005 during their PFAS SI. The sample contained 700 nanograms per liter (ng/L) PFOA and PFOS, 

combined (Leidos, 2018). The outfall conveys flow south to Horsepen Bayou, and then to Armand 
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AECOM 3-2

Bayou (BB&E, 2016). AFFF may have flowed off paved surfaces or through cracks or joints in 

pavement. 

3.3 Adjacent Sources

Seven off-facility, potential sources were identified adjacent to the Ellington Field AASF during the 

PA and are not associated with ARNG activities. The adjacent potential sources are shown on 

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

investigated as part of this SI. Findings noted in Sections 3.3.1 through 3.3.5 are results of a 2018 

SI (Leidos, 2018) conducted at the JRB by the TXANG. 

3.3.1 TXANG Old Fire Station

The Old Fire Station (Building 694) was operated by TXANG from pre-1988 to 2012 and was 

reported to having minor leaks of AFFF from crash response trucks and firetrucks over the years 

(BB&E, Inc., 2016). The old fire station is located approximately 2,600 feet south of the TXARNG 

hangar.

During the 2018 TXANG SI, a monitoring well was installed adjacent to the old fire station in 2018 

to determine PFAS levels in shallow groundwater. Results indicated levels of the individual 

relevant compounds ranging from 110 ng/L to 44,000 J ng/L (Leidos, 2018). This area is crossgradient of the facility and shares the same stormwater network as TXARNG; therefore, it is 

possible the that potential impacts from the AFFF leaks are migrating towards the Ellington Field 

AASF. 

3.3.2 TXANG New Fire Station

Ellington Field AASF currently receives fire protection from the TXANG New Fire Station (Building 

1190), which was constructed in 2012 and is located adjacent to the north of the TXARNG hangar. 

The TXANG Fire Chief (onsite since 1988) reported their department switched from AFFF with 

longer-chain (C8) PFAS to AFFF with short-chain (C6) PFAS in December 2016 (AECOM, 2020). 

The TXANG Fire Chief reported that his department has never trained with the AFFF spray from 

a firetruck. However, TXANG has conducted joint fire training using AFFF-containing mobile carts 

with TXARNG staff at the TXARNG wash rack and flight line from the early 1990s to approximately 

2009. The new fire station currently uses fire/crash response vehicles and firetrucks that are

equipped with AFFF-containing short-chain PFAS but does not currently conduct fire training 

exercises involving AFFF with the TXARNG.

During the 2018 ANG SI at the JRB, groundwater sampling results from a monitoring well installed 

adjacent to the TXANG New Fire Station indicate levels of the individual relevant compounds 

ranging from 33 J ng/L to 6,300 J ng/L (Leidos, 2018). This area is upgradient of AOI 2 and shares 

the same stormwater network as TXARNG; therefore, it is possible the that potential impacts from 

the AFFF leaks are migrating towards the facility.

3.3.3 TXANG Aircraft Parking Apron

Groundwater samples from four monitoring wells installed during the 2018 TXANG SI at the 

aircraft parking apron, north of TXARNG facility, had detections of the individual relevant 

compounds ranging from 0.54 J ng/L to 50,000 J ng/L (Leidos, 2018). This area is cross-gradient 

of the facility and shares the same stormwater network as TXARNG; therefore, it is possible the 

that potential impacts from this area are migrating towards the facility.
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Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 3-3

3.3.4 TXANG Hangars 1382 and 1394

Hangars 1382 and 1394 both previously contained AFFF-equipped fire suppression systems with 

a few minor AFFF leaks reported in the past. During the 2018 TXANG SI, a groundwater sample 

collected just east of Hangar 1382 had detections of the individual relevant compounds ranging 

from 23 ng/L to 50,000 J ng/L. A groundwater sample collected just south of Hangar 1394 had 

detections of the individual relevant compounds ranging from 11 to 1,700 J ng/L (Leidos, 2018). 

These areas are cross-gradient of the facility and share the same stormwater network as 

TXARNG; therefore, it is possible the that potential impacts from the hangars are migrating 

towards the facility.

3.3.5 Stormwater Discharge Outfalls 001 and 005

Stormwater from TXANG that may contain PFAS, as demonstrated in the TXANG SI Report 

(Leidos, 2018), is transported through the TXARNG facility in the shared drainage system, 

eventually reaching Horsepen Bayou. Stormwater discharge outfalls were tested for PFAS in 2018 

during the TXANG SI. Results of a surface water samples taken from Stormwater Discharge 

Outfalls 001 (located south of the facility) and 005 (located in the flight line of TXARNG facility) 

indicated levels of the individual relevant compounds ranging from 2.6 ng/L to 970 J ng/L (Leidos, 

2018).

3.3.6 NASA

NASA leases the southern portion of Ellington Field JRB from the City of Houston and hosts 

various privately held companies on its property. No personnel from NASA were interviewed, and 

AFFF use is unknown but may have been used for firefighting purposes. This area is located 

south and downgradient of the facility and is, therefore, unlikely to impact Ellington Field AASF. 

3.3.7 Brio Superfund Site

The Brio Superfund Site is located at 2501 Dixie Farm Road in Friendswood, Texas, 

approximately 3.5 miles southwest and cross-gradient of Ellington Field AASF. As mentioned in 

the PA, there is no known use of PFAS at the site, and groundwater flow to the southeast is 

unlikely to bring contamination from the Brio Site to Ellington Field AASF. 

3.3.8 Enterprise Echo Terminal

The Enterprise Echo Terminal is located at 6849 East Sam Houston Parkway in Houston, Texas, 

approximately 0.4 miles northwest and upgradient of Ellington Field AASF. The terminal is an 

industrial storage facility for Enterprise Products and Partners L.P., an oil and natural gas 

company. This property may present a potential offsite source as use of PFAS at this terminal is 

unknown. 

3.3.9 Combined Maintenance Facility

A combined maintenance facility, shared between the Marines, Navy, and Army National Guard, 

is located approximately 300 feet upgradient, at the end of Aerospace Avenue near Ashely Street. 

This property may present a potential offsite source as use of PFAS is unknown. 
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Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 3-4

3.3.10 Pasadena Municipal Golf Course

The Pasadena Municipal Golf Course is located at 1000 Duffer Lane in Houston, Texas, 

approximately 625 feet west and upgradient of Ellington Field AASF. This property may present a 

potential offsite source as use of PFAS at this location is unknown. 
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Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 4-1

4. Project Data Quality Objectives

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

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

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

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

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

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

AOIs.

4.1 Problem Statement 

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

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

SLs are presented in Section 6.1 of this report. 

4.2 Information Inputs

Primary information inputs included:

• The PA for Ellington Field AASF (AECOM, 2020);

• The TXANG SI for Ellington Field JRB (Leidos, 2018);

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

with the site-specific Uniform Federal Policy (UFP)-QAPP Addendum (AECOM, 2022b); and

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

parameters measured at the time of sampling.

4.3 Study Boundaries

The scope of the SI was bounded by the property limits of the facility (Figure 2-2), except for two 

existing off-facility wells located directly north of AOI 2 within the Ellington Field JRB. These two wells 

were sampled during the SI. The SI scope was bounded vertically by the observed depths of the 

surficial groundwater table. Temporal boundaries were limited to the spring season, which was the 

earliest time field resources were available to complete the study. 

4.4 Analytical Approach

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

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

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

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

Addendum (AECOM, 2022b). 

4.5 Data Usability Assessment 

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

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

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

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

installation-specific DQOs. Both sampling and analytical activities are considered to assess 
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AECOM 4-2

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

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

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

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

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

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 5-1

5. Site Inspection Activities

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

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

in accordance with the following approved documents: 

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

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

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

• Final Preliminary Assessment Report, Ellington Field Army Aviation Support Facility,

Houston, Texas dated July 2020 (AECOM, 2020);

• Final Site Safety and Health Plan, Ellington Field Army Aviation Support Facility, Houston,

Texas dated May 2022 (AECOM, 2022a); and

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

Ellington Field Army Aviation Support Facility, Houston, Texas dated June 2022 (AECOM,

2022b).

The SI field activities were conducted from 1 to 9 June 2022 and consisted of utility clearance, direct 

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

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

Addendum (AECOM, 2022b), except as noted in Section 5.8. 

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

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

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

• Sixteen (16) soil samples from four boring locations and four hand auger locations;

• Four grab groundwater samples from four temporary wells and two groundwater samples

from two existing permanent wells;

• Twelve (12) quality assurance (QA)/quality control (QC) samples.

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

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

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

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

Appendix B3, and a Nonconformance and Corrective Action Report is provided in Appendix B4. 

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

5.1 Pre-Investigation Activities

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

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

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

5.1.1 Technical Project Planning

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

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

determining data needs; 3.) developing data collection strategies; and 4.) finalizing the data 

collection plan. The process encourages stakeholder involvement in the SI, beginning with 
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AECOM 5-2

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 3 May 2022, prior to SI field activities. The 

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

stakeholders for this SI include the ARNG, TXARNG, USACE, TXANG, and Texas Commission 

on Environmental Quality. Stakeholders were provided the opportunity to make comments on the 

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

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

2022b). 

A TPP Meeting 3 was held on 11 July 2023 to discuss the results of the SI. Meeting minutes for 

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

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

5.1.2 Utility Clearance

AECOM placed a ticket with the Texas 811 utility clearance provider to notify them of intrusive 

work on 1 June 2022. Additionally, AECOM contracted Ground Penetrating Radar Systems, LLC

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

clearance of the proposed boring locations on 1 June 2022 with input from the AECOM field team 

and Ellington Field AASF facility staff. General locating services and ground-penetrating radar 

were used to complete the clearance. Additionally, the first 5 feet of each boring were pre-cleared 

using a hand auger to verify utility clearance in shallow subsurface where utilities would typically 

be encountered. 

5.1.3 Source Water and Sampling Equipment Acceptability

The Wash Rack spigot was sampled at Ellington Field AASF on 12 May 2022 to assess the 

usability of the water for decontamination of drilling equipment. Water from the spigot was 

transferred to a tote to allow for decontamination staging in an alternate area. Water from the tote 

was sampled on 8 June 2022. The samples were analyzed by LC/MS/MS compliant with QSM 

5.3 Table B-15. Results of the samples collected at the wash rack spigot (EFF-PW-01) and the 

tote (EF-DECON-01) confirmed this source and container to be acceptable for use in this

investigation; therefore, they were used throughout the field activities. The results of the 

decontamination water sample associated with the Wash Rack spigot source used during the SI 

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

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

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

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

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

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

member regarding the allowable materials within the sampling environment. 

5.2 Soil Borings and Soil Sampling

Soil samples were collected via hand auger at locations designated for surface soil (0 to 2 feet 

bgs) sampling only. Subsurface soil samples were collected via direct push technology (DPT), in 

accordance with the SI QAPP Addendum (AECOM, 2022b). A GeoProbe® 7822DT dual-tube 

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

used to collect soil from the top 5 feet of the boring, in accordance with AECOM utility clearance 

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

5-1.
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 5-3

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

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

subsurface soil sample approximately 2 feet above the groundwater table, and one subsurface 

soil sample at the mid-point between the surface and the groundwater table. 

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

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

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

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

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

(using the USCS) were recorded. 

Soil borings completed during the SI found low to medium plasticity lean clay as the dominant 

lithology of the unconsolidated sediments below the Ellington Field AASF. The borings were 

completed at depths between 15 and 25 feet bgs. Layers of silty sand and sandy silt were also 

observed in the boring logs at thicknesses ranging from 2 to 3.5 feet. These observations are 

consistent with the understood depositional environment of the region.

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

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

and transported via FedEx under standard chain of custody (CoC) procedures to the laboratory 

and analyzed by LC/MS/MS compliant with QSM 5.3 Table B-15, total organic carbon (TOC) 

(USEPA Method 9060A), pH (USEPA Method 9045D), and grain size (ASTM Method D-422) in 

accordance with the SI QAPP Addendum (AECOM, 2022b). 

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

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

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

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

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

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

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

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

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

of sampling activities. Borings were installed in grass areas to avoid disturbing concrete or asphalt 

surfaces.

5.3 Temporary Well Installation and Groundwater Sampling

Temporary wells were installed using a GeoProbe® 7822DT dual-tube sampling system. Once 

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

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

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

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

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

groundwater to infiltrate and recharge the temporary well screen intervals. After the recharge 

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

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

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

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

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

collected. Additionally, a subsample of each groundwater sample was collected in a separate 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 5-4

container, and a shaker test was completed to identify if there were any foaming. No foaming was 

noted in any of the groundwater samples. 

Groundwater samples were also collected from two existing permanent monitoring wells (MWELL02-01 and MW-ELL02-02) located off facility, just north of AOI 2. Samples were collected via 

low-flow sampling methods using a peristaltic pump with PFAS-free HDPE tubing. Water quality 

parameters (e.g., temperature, specific conductance, pH, dissolved oxygen, turbidity, and 

oxidation-reduction potential) were measured using a water quality meter with a flow through cell 

and recorded on the field sampling form (Appendix B2). All non-dedicated sampling materials 

were decontaminated between boring locations. A shaker test was also completed for the 

groundwater samples collected from the permanent wells, and no foaming was noted.

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

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

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

Table B-15 in accordance with the SI QAPP Addendum (AECOM, 2022b). 

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

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

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

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

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

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

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

the hole with bentonite chips. Upon completion of well abandonment, the ground surface at each 

location was patched to match existing surrounding conditions.

5.4 Synoptic Water Level Measurements

A synoptic groundwater gauging event was performed on 9 June 2022. Groundwater elevation 

measurements were collected from the four new temporary monitoring wells and two existing 

permanent monitoring wells. Water level measurements were taken from the northern side of the 

well casing. An accurate stable water level measurement was unable to be obtained from 

temporary monitoring well AOI01-01 due to poor recharge. However, sufficient data were collected 

from the other wells to estimate a local groundwater flow direction at the facility. A groundwater 

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

2. 

5.5 Surveying 

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

guidelines provided in the SOPs provided in the SI QAPP Addendum (AECOM, 2022b). Survey 

data from the newly installed wells on the facility were collected on 9 June 2022 in the applicable 

Universal Transverse Mercator zone projection with North American Datum 1983 (horizontal) and 

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

B3. 

5.6 Investigation-Derived Waste 

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

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

accordance with the SI QAPP Addendum (AECOM, 2022b) and with the DA Guidance for 

Addressing Releases of PFAS, Q18 (DA, 2018). 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 5-5

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

gallon Department of Transportation (DOT)-approved steel drum and left onsite in a designated 

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

associated soil samples collected from that source location. ARNG will coordinate waste profiling, 

transportation, and disposal of the solid IDW. 

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

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

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

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

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

onsite disposal with treatment, as appropriate) under a separate contract in accordance with SOP 

No. 042A (EA, 2021).

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

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

activities were disposed of at a licensed solid waste landfill.

5.7 Laboratory Analytical Methods

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

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

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

5.8 Deviations from SI QAPP Addendum

A deviation from the SI QAPP Addendum was identified during review of the field documentation. 

The deviation is noted below and is documented in a Nonconformance and Corrective Action 

Reports (Appendix B4): 

• Per the SI QAPP Addendum, two ERB samples were to be collected from non-dedicated

soil sampling equipment. Due to a misunderstanding of the QAPP, the field team collected

ERB samples from the water level meters used during groundwater sampling. Although no

soil related ERB samples were collected, the same decontamination procedures were

followed for the water level meters and soil sampling equipment. The ERB samples collected

from the water level meters were non-detect for analyzed compounds. Additionally, no data

usability issues were noted in the data usability assessment (Appendix A). This action was

documented in a nonconformance and corrective action report provided in Appendix B4.
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 5-6

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Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Ellington Field AASF, Texas

Sample Identification

Sample

Collection 

Date/Time

Sample Depth 

(feet bgs)

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

Comments

AOI01-01-SB-00-02 6/7/2022 13:53 0 - 2 x x

AOI01-01-SB-05-07 6/7/2022 14:15 5 - 7 x x x

AOI01-01-SB-09-11 6/7/2022 14:20 9 - 11 x

AOI01-02-SB-00-02 6/7/2022 11:20 0 - 2 x x x

AOI01-02-SB-00-02-D 6/7/2022 11:20 0 - 2 x FD

AOI01-02-SB-10-12 6/7/2022 12:20 10 - 12 x

AOI01-02-SB-18-20 6/7/2022 12:25 18 - 20 x

AOI01-03-SB-00-02 6/7/2022 13:05 0 - 2 x

AOI02-01-SB-00-02 6/8/2022 12:05 0 - 2 x x x x

AOI02-01-SB-00-02-D 6/8/2022 12:05 0 - 2 x FD

AOI02-02-SB-00-02 6/7/2022 10:52 0 - 2 x

AOI02-02-SB-00-02-MS 6/7/2022 11:30 0 - 2 x x x MS

AOI02-02-SB-00-02-MSD 6/7/2022 11:30 0 - 2 x x x MSD

AOI02-03-SB-00-02 6/7/2022 10:25 0 - 2 x

EF-01-SB-00-02 6/7/2022 15:17 0 - 2 x

EF-01-SB-05-07 6/7/2022 15:58 5 - 7 x

EF-01-SB-10-12 6/7/2022 16:02 10 - 12 x

EF-02-SB-00-02 6/8/2022 8:30 0 - 2 x

EF-02-SB-05-07 6/8/2022 10:00 5 - 7 x

EF-02-SB-10.5-12 6/8/2022 10:05 10.5 - 12 x

AOI01-01-GW 6/8/2022 15:30 NA x

AOI01-02-GW 6/8/2022 12:45 NA x

AOI01-02-GW-D 6/8/2022 12:45 NA x FD

AOI01-02-GW-MS 6/8/2022 12:45 NA x MS

AOI01-02-GW-MSD 6/8/2022 12:45 NA x MSD

EF-01-GW 6/8/2022 10:55 NA x

EF-02-GW 6/8/2022 14:20 NA x

MW-ELL02-01-060822 6/8/2022 15:10 NA x

MW-ELL02-02-060922 6/9/2022 9:25 NA x

Soil Samples

Groundwater Samples

AECOM 5-7 
Table 5-1

Site Inspection Samples by Medium

Site Inspection Report, Ellington Field AASF, Texas

Sample Identification

Sample

Collection 

Date/Time

Sample Depth 

(feet bgs)

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

Comments

EFF-PW-01 5/12/2022 11:50 NA x wash rack spigot

EF-FRB-01 6/8/2022 14:30 NA x

collected following 

sampling at EF-02-

GW

EF-ERB-01 6/8/2022 11:00 NA x water level probe

EF-ERB-02 6/8/2022 14:25 NA x water level probe

EF-DECON-01 6/8/2022 14:40 NA x decon water tote

Notes:

AOI = area of interest

ASTM = American Society for Testing and Materials

bgs = below ground surface

EF = Ellington Field

ERB = equipment rinsate blank

FD = field duplicate

FRB = field reagent blank

GW = groundwater

LC/MS/MS = Liquid Chromatography Mass Spectrometry

MS/MSD = matrix spike/ matrix spike duplicate

MW = monitoring well

NA = not applicable

QSM = Quality Systems Manual

SB = soil boring

TOC = total organic carbon

USEPA = United States Environmental Protection Agency

Quality Control Samples

AECOM 5-8 
Table 5-2

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

Site Inspection Report, Ellington Field AASF, Texas

Area of 

Interest Location

Soil Boring 

Depth 

(feet bgs)

Well Screen 

Interval 

(feet bgs)

Top of Casing 

Elevation 

(feet NAVD88)

Ground Surface 

Elevation 

(feet NAVD88)

Depth to 

Water

(feet btoc)

Dep

Wa

(feet 

AOI01-01 15 10 - 15 31.97 31.62 9.02 8.AOI01-02 25 20 - 25 31.78 31.43 5.35 5.

EF-01 15 10 - 15 32.40 32.05 5.97 5.

EF-02 15 10 - 15 33.26 32.91 6.31 5.

MW-ELL02-01 NA 2.8 - 12.8 30.69 30.82 4.01 4.

MW-ELL02-02 NA 4.35 - 14.35 30.10 30.33 4.34 4.

Notes:

1. Well screen, top of casing, and ground surface elevation information for exisitng permanent wells MW-ELL002-01 and MW-ELL02-02 obtained from Lei

AOI = area of interest

bgs = below ground surfacebtoc = below top of casingEF = Ellington FieldMW = monitoring wellNA = not applicableNAVD88 = North American Vertical Datum 1988

1

AECOM 
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M 5-10
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A!

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AOI01-01

EF-01

EF-02

AOI01-03

AOI01-02

MWELL02-01

MWELL02-02

AOI02-03

AOI02-02

AOI02-01

CLIENT

REVISED

SCALE

ARNG

GIS BY

CHK BY

MS

SK

5/8/2023

5/8/2023

PROJECT Site Inspection at Ellington Field, TX

1:3,600

5/8/2023 ­ Figure 5-1 PM CM 5/8/2023

12420 Milestone Center Drive

Germantown, MD 20876

Site Inspection Sample Locations

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

and the GIS User Community

0 150 300 600

Feet

Legend

?! Soil Boring/Temporary Monitoring Well

A! Existing Monitoring Well

"S Surface Soil Sample

Approximate Corrected Facility Boundary

Facility Boundary

Surface Water Flow Direction

Groundwater Flow Direction

AECOM 5-11
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 5-12

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Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 6-1

6. Site Inspection Results

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

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

Section 6.4. Table 6-2 through Table 6-5 present results in soil or groundwater for the relevant 

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

are provided in Appendix G. 

6.1 Screening Levels 

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

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

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

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

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

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

6-1 below.

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

Analyteb

Residential

(Soil)

(μg/kg)a 

0-2 feet bgs

Industrial/ 

Commercial 

Composite 

Worker 

(Soil)

(μg/kg)a 

2-15 feet bgs

Tap Water

(Groundwater) 

(ng/L)a

PFOA 19 250 6 

PFOS 13 160 4

PFBS 1,900 25,000 601 

PFHxS 130 1,600 39

PFNA 19 250 6 

Notes:

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

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

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

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

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

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

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

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

for groundwater are based on direct ingestion and have been conservatively applied for 

groundwater at the Ellington Field AASF although it is not used as a drinking water source at the 

facility. The SLs for soil are based on incidental ingestion and are applied to the depth intervals 

reasonably anticipated to be encountered by the receptors identified at the facility: the residential 

scenario is applied to surface soil results (0 to 2 feet bgs) and the industrial/commercial worker 

scenario is applied to shallow subsurface soil results (2 to 15 feet bgs). The SLs are not applied 

to deep subsurface soil results (>15 feet bgs) because 15 feet is the anticipated limit of 

construction activities. 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 6-2

6.2 Soil Physicochemical Analyses

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

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

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

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

appropriate, to assess fate and transport. According to the ITRC, several important partitioning 

mechanisms include hydrophobic and lipophobic effects, electrostatic interactions, and interfacial 

behaviors. At relevant environmental pH values, certain PFAS are present as organic anions and 

are therefore relatively mobile in groundwater (Xiao et al., 2015), but tend to associate with the 

organic carbon fraction that may be present in soil or sediment (Higgins and Luthy, 2006; Guelfo 

and Higgins, 2013). When sufficient organic carbon is present, organic carbon normalized 

distribution coefficients (Koc values) can help in evaluating transport potential, though other 

geochemical factors (for example, pH and presence of polyvalent cations) may also affect PFAS 

sorption to solid phases (ITRC, 2018).

6.3 AOI 1 

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

AOI 1: Wash Rack. The soil and groundwater results are summarized on Table 6-2 through Table 

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

6.3.1 AOI 1 Soil Analytical Results

Surface soil was sampled from 0 to 2 feet bgs at boring locations AOI01-01 through AOI01-03, 

and EF-02 located upgradient of AOI 1. Shallow subsurface soil was sampled at depths of 5 to 7 

feet bgs and between 9 to 12 feet bgs at AOI01-01 and EF-02. Soil was also sampled from shallow 

subsurface soil (10 to 12 feet bgs) and deep subsurface soil intervals (18 to 20 feet bgs) at AOI01-

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

Table 6-4 summarize the soil results.

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected below their SLs in soil as summarized 

below: 

• All five relevant compounds were detected below their SLs in shallow soil with the

following maximum concentrations: PFOA at 0.137 J micrograms per kilogram (μg/kg),

PFOS at 6.92 μg/kg, PFHxS at 3.06 μg/kg, PFNA at 0.082 J μg/kg, and PFBS at

0.272 J μg/kg.

• PFOA, PFOS, PFHxS, and PFBS were detected below their SLs in shallow

subsurface soil with the following maximum concentrations: PFOA at 0.101 J μg/kg,

PFOS at 1.79 μg/kg, PFHxS at 8.10 μg/kg, and PFBS at 1.27 μg/kg. PFNA was not

detected in shallow subsurface soil.

• PFHxS was detected in deep subsurface soil, with a concentration of 0.072 J μg/kg.

PFOA, PFOS, PFNA, and PFBS were not detected in deep subsurface soil.

6.3.2 AOI 1 Groundwater Analytical Results

Figure 6-6 and Figure 6-7 present the ranges of detections in groundwater. Table 6-5 

summarizes the groundwater results. 

Groundwater was sampled from upgradient temporary well EF-02 which was intended to 

determine presence of impacts on the facility from potential adjacent sources. PFOS was detected 
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Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 6-3

above the SL of 4 ng/L, with a concentration of 6.62 J ng/L. PFHxS and PFBS were detected 

below their SLs, with concentrations of 30.6 J ng/L and 6.28 J ng/L, respectively. PFOA and PFNA 

were not detected.

At the AOI 1 source area, groundwater was sampled from temporary monitoring wells AOI01-01

and AOI01-02. The following concentrations with respect to the SLs were measured:

• PFOA was detected above the SL of 6 ng/L at both wells, with concentrations of 151 J

ng/L at AOI01-01 and 14.0 J ng/L at AOI01-02.

• PFOS was detected above the SL of 4 ng/L at both wells, with concentrations of 2,150

J ng/L at AOI01-01 and 127 ng/L J at AOI01-02.

• PFHxS was detected above the SL of 39 ng/L at both wells, with concentrations of

17,700 J ng/L at AOI01-01 and 376 J ng/L at AOI01-02.

• PFBS was detected above the SL of 601 ng/L, with a concentration of 2,750 J ng/L at

AOI01-01. PFBS was detected below the SL at AOI01-02 with a concentration of 72.2

J ng/L.

• PFNA was detected below the SL of 6 ng/L, with a concentration of 1.54 J ng/L at

AOI01-02. PFNA was not detected at AOI01-01.

6.3.3 AOI 1 Conclusions

Based on the results of the SI, none of the detected relevant compounds in any soil sample were 

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

concentrations above their SLs. Based on the exceedances of the SLs in groundwater, further 

evaluation at AOI 1 is warranted. 

6.4 AOI 2 

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

AOI 2: Flight Line. The results in soil are summarized on Table 6-2. Soil results are presented on 

Figure 6-1 through Figure 6-5. 

6.4.1 AOI 2 Soil Analytical Results

Soil was sampled from surface soil (0 to 2 feet bgs) from boring locations AOI02-01 through 

AOI02-03. Figure 6-1 through Figure 6-5 present the ranges of detections in soil. Table 6-2 

summarizes the soil results. 

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected below their SLs in surface soil with the 

following maximum concentrations: PFOA at 0.388 J μg/kg, PFOS at 12.7 J μg/kg, PFHxS at 

0.813 J μg/kg, PFNA at 0.253 J μg/kg, and PFBS at 0.047 J μg/kg. 

6.4.2 AOI 2 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 was sampled from temporary monitoring wells EF-01 and EF-02, as well as

permanent monitoring well MW-ELL02-01, all of which are located upgradient of AOI 2. 

Groundwater was also sampled from permanent monitoring well MW-ELL02-02 located crossgradient of AOI 2. No groundwater was sampled downgradient of the AOI 2 source area as drilling 

in this area would impact the flight line. Detections in samples collected upgradient of AOI 2 may 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 6-4

indicate a potential unknown off-facility source. The following concentrations with respect to the 

SLs were measured:

• PFOA was detected above the SL of 6 ng/L at MW-ELL02-01, with a concentration of

206 J ng/L. PFOA was detected below the SL at MW-ELL02-02 and EF-01. PFOA was

not detected at EF-02.

• PFOS was detected above the SL of 4 ng/L at three of the four wells, with concentrations

ranging from 6.62 J ng/L to 4,010 J ng/L. PFOS was detected below the SL at EF-01.

• PFHxS was detected above the SL of 39 ng/L at three of the four wells, with

concentrations ranging from 42.6 J ng/L to 3,260 J ng/L. PFHxS was detected below

the SL at EF-02.

• PFNA was detected above the SL of 6 ng/L at MW-ELL02-01, with a concentration of

30.3 J ng/L ng/L. PFNA was not detected at EF-01, EF-02, or MW-ELL02-02.

• PFBS was detected below the SL of 601 ng/L at all four wells, with a maximum

concentration of 250 J ng/L at MW-ELL02-01.

6.4.3 AOI 2 Conclusions

Based on the results of the SI, none of the relevant compounds were detected in any surface soil 

sample above their respective SLs. Though no groundwater was sampled within AOI 2 (the entire 

area is covered by flight line concrete), PFOA, PFOS, PFHxS, and PFNA were detected at 

concentrations above their SLs in groundwater in nearby wells upgradient and cross-gradient of 

AOI 2. Based on the exceedances of the SLs in groundwater surrounding AOI 2 in combination 

with the detections in soil at AOI 2, further evaluation at AOI 2 is warranted. 
Table 6-2

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

Site Inspection Report, Ellington Field AASF

Analyte OSD Screening 

Level a

Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Result Qual Resu

PFBS 1900 0.052 J 0.265 J 0.272 J ND U 0.028 J 0.047 J 0.026 J 0.038 J ND PFHxS 130 3.06 0.587 J 0.799 J 0.186 J 0.507 J 0.528 J 0.453 J 0.813 J 0.768 PFNA 19 ND U ND U ND U 0.082 J 0.161 J 0.090 J 0.079 J 0.253 J 0.024 PFOA 19 0.137 J ND U ND U ND U 0.174 J 0.123 J 0.121 J 0.388 J 0.157 PFOS 13 1.37 ND U ND U 6.92 12.7 J 4.88 J 2.37 6.21 0.694 

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

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

DL detection limit

Notes EF Ellington Field

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. ft feet

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

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

AOI01 AOI02 

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

AOI02-03-SB-00-02

06/07/2022

0-2 ft

EF-0

0

AOI02-01-SB-00-02-D

06/08/2022

0-2 ft

AOI02-02-SB-00-02

06/07/2022

0-2 ft

AOI01-03-SB-00-02

06/07/2022

0-2 ft

AOI02-01-SB-00-02

06/08/2022

0-2 ft

AOI01-02-SB-00-02

06/07/2022

0-2 ft

AOI01-02-SB-00-02-D

06/07/2022

0-2 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-00-02

06/07/2022

0-2 ft

AECOM 
Table 6-3

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

Site Inspection Report, Ellington Field AASF

Analyte OSD Screening 

Level a

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

PFBS 25000 0.153 J 1.27 0.066 J ND U ND UJ ND UJ ND UJPFHxS 1600 2.57 8.10 0.504 J 0.409 J ND UJ ND UJ ND UJPFNA 250 ND U ND U ND U ND U ND UJ ND UJ ND UJPFOA 250 ND U 0.101 J ND U ND U ND UJ ND UJ ND UJPFOS 160 1.23 1.79 0.172 J 0.109 J ND UJ ND UJ ND UJ

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityU = The analyte was not detected at a level greater than or equal to the adjusted DL AOI Area of Interest

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

DL detection limit

Notes EF Ellington Field

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. ft feet

HQ hazard quotientID identificationLCMSMS liquid chromatography with tandem mLOD limit of detectionND analyte not detected above the LODOSD Office of the Secretary of DefenseQSM Quality Systems ManualQual interpreted qualifierSB soil boringUSEPA United States Environmental Protectioμg/kg micrograms per kilogram

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

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

AOI01 EF-01 EF-02

EF-02-SB-05-07

06/08/2022

5-7 ft

EF-02-SB-10.5-12

06/08/2022

10.5-12 ft

EF-01-SB-05-07

06/07/2022

5-7 ft

EF-01-SB-10-12

06/07/2022

10-12 ft

AOI01-01-SB-09-11

06/07/2022

9-11 ft

AOI01-02-SB-10-12

06/07/2022

10-12 ft

Area of Interest

Sample ID

Sample Date

Depth

AOI01-01-SB-05-07

06/07/2022

5-7 ft

AECOM 
Table 6-4

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

Site Inspection Report, Ellington Field AASF

Area of Interest

Sample ID

Sample Date

Depth

Analyte Result Qual

PFBS ND UPFHxS 0.072 JPFNA ND UPFOA ND UPFOS ND U

Interpreted Qualifiers Chemical AbbreviationsJ = Estimated concentration PFBS perfluorobutanesulfonic acidU = The analyte was not detected at a level greater than or equal to the adjusted DL PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acid

Notes PFOA perfluorooctanoic acid

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. PFOS perfluorooctanesulfonic acid

Acronyms and AbbreviationsAASF Army Aviation Support FacilityAOI Area of InterestD duplicateDL detection limitft feetID identificationLCMSMS liquid chromatography with tandem mass LOD limit of detectionND analyte not detected above the LODQSM Quality Systems ManualQual interpreted qualifierSB soil boringμg/kg micrograms per kilogram

AOI01

AOI01-02-SB-18-20

06/07/2022

18-20 ft

Soil, LCMSMS compliant with QSM 5.3 Table B

AECOM 
Table 6-5

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

Site Inspection Report, Ellington Field AASF

Analyte OSD Screening 

Level a

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

PFBS 601 2750 J 72.2 J 59.2 J 17.4 J 6.28 J 250 J 7.35 JPFHxS 39 17700 J 376 J 307 J 59.8 J 30.6 J 3260 J 42.6 JPFNA 6 ND UJ 1.54 J 1.24 J ND UJ ND UJ 30.3 J ND UJPFOA 6 151 J 14.0 J 11.6 J ND UJ ND UJ 206 J 3.07 JPFOS 4 2150 J 127 J 106 J 3.23 J 6.62 J 4010 J 14.2 J

Grey Fill Detected concentration exceeded OSD Screening Levels Chemical Abbreviations

PFBS perfluorobutanesulfonic acid

References PFHxS perfluorohexanesulfonic acid

PFNA perfluorononanoic acidPFOA perfluorooctanoic acidPFOS perfluorooctanesulfonic acid

Interpreted Qualifiers Acronyms and Abbreviations

J = Estimated concentration AASF Army Aviation Support FacilityUJ = The analyte was not detected at a level greater than or equal to the adjusted DL. However, the reported adjusted DL is approximate and may be inaccurate or imprecise. AOI Area of Interest

D duplicate

Notes DL detection limit

ND = Analyte not detected above the LOD. LOD values are presented in Appendix F. EF Ellington Field

ELL EllingtonGW groundwaterHQ hazard quotientID identificationLCMSMS liquid chromatography with tandem LOD limit of detectionLOQ limit of quantitationMW Monitoring WellOSD Office of the Secretary of DefensePFAS per- and polyfluoroalkyl substanceQSM Quality Systems ManualQual interpreted qualifierUSEPA United States Environmental Proteng/l nanogram per liter- not applicable< analyte not detected above the LO

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

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

AOI01 Sitewide

MW-ELL02-01-060822

06/08/2022

MW-ELL02-02-060922

06/09/2022

EF-01-GW

06/08/2022

EF-02-GW

06/08/2022

AOI01-02-GW

06/08/2022

AOI01-02-GW-D

06/08/2022

Area of Interest

Sample ID

Sample Date

AOI01-01-GW

06/08/2022

AECOM 
AOI01-01

EF-01

EF-02

AOI01-03

AOI01-02

AOI02-03

AOI02-02

AOI02-01

Legend

Approximate Corrected Facility

Boundary

Facility Boundary

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-1

PFOA Detections in Soil

2/14/2023

2/14/2023

MS 2/14/2023

SW

CM

GIS BY

CHK BY

PM

2/14/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:3,000

AOI01-01

EF-01

EF-02

AOI01-02

AOI01-01

EF-01

EF-02

AOI01-02

0 125

­

250 500

Feet

Shallow

Intermediate

Deep

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

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

PFOA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-9 
AOI01-01

EF-01

EF-02

AOI01-03

AOI01-02

AOI02-03

AOI02-02

AOI02-01

Legend

Approximate Corrected Facility

Boundary

Facility Boundary

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-2

PFOS Detections in Soil

2/14/2023

2/14/2023

MS 2/14/2023

SK

CM

GIS BY

CHK BY

PM

2/14/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:3,000

AOI01-01

EF-01

EF-02

AOI01-02

AOI01-01

EF-01

EF-02

AOI01-02

Shallow

Intermediate

Deep

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

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

PFOS Results (μg/Kg)

ND

>ND - 13

>13 - 160

>160 - 1,600

>1,600

0 125

­

250 500

Feet

AECOM 6-10
AOI01-01

EF-01

EF-02

AOI01-03

AOI01-02

AOI02-03

AOI02-02

AOI02-01

Legend

Approximate Corrected Facility

Boundary

Facility Boundary

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-3

PFBS Detections in Soil

2/14/2023

2/14/2023

MS 2/14/2023

SK

CM

GIS BY

CHK BY

PM

2/14/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:3,000

AOI01-01

EF-01

EF-02

AOI01-02

AOI01-01

EF-01

EF-02

AOI01-02

Shallow

Intermediate

Deep

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

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

0 125

­

250 500

Feet

PFBS Results (μg/Kg)

ND

>ND - 10

>10 - 1,900

>1,900 - 25,000

>25,000

AECOM 6-11
AOI01-01

EF-01

EF-02

AOI01-03

AOI01-02

AOI02-03

AOI02-02

AOI02-01

Legend

Approximate Corrected Facility

Boundary

Facility Boundary

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-4

PFHxS Detections in Soil

2/14/2023

2/14/2023

MS 2/14/2023

SK

CM

GIS BY

CHK BY

PM

2/14/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:3,000

AOI01-01

EF-01

EF-02

AOI01-02

AOI01-01

EF-01

EF-02

AOI01-02

Shallow

Intermediate

Deep

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

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

0 125

­

250 500

Feet

PFHxS Results (μg/Kg)

ND

>ND - 10

>10 - 130

>130 - 1,600

>1,600

AECOM 6-12
AOI01-01

EF-01

EF-02

AOI01-03

AOI01-02

AOI02-03

AOI02-02

AOI02-01

Legend

Approximate Corrected Facility

Boundary

Facility Boundary

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-5

PFNA Detections in Soil

2/14/2023

2/14/2023

MS 2/14/2023

SK

CM

GIS BY

CHK BY

PM

2/14/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:3,000

AOI01-01

EF-01

EF-02

AOI01-02

AOI01-01

EF-01

EF-02

AOI01-02

Shallow

Intermediate

Deep

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

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

0 125

­

250 500

Feet

PFNA Results (μg/Kg)

ND

>ND - 19

>19 - 250

>250 - 2,500

>2,500

AECOM 6-13
AOI01-01

EF-01

EF-02

AOI01-02

MWELL02-01

MWELL02-02

Legend

Approximate Corrected Facility Boundary

Facility Boundary

Groundwater Flow Direction

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-6

PFOA, PFOS, and PFBS Detections

 in Groundwater

5/8/2023

5/8/2023

MS 5/8/2023

SW

CM

GIS BY

CHK BY

PM

5/8/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:3,000

AOI01-01

EF-01

EF-02

AOI01-02

MWELL02-01

MWELL02-02

AOI01-01

EF-01

EF-02

AOI01-02

MWELL02-01

MWELL02-02

PFOA

PFOS

PFBS

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

0 125

­

250 500

Feet

PFOA Results (ng/L)

ND

>ND - 6

>6 - 40

>40 - 70

>70

PFOS Results (ng/L)

ND

>ND - 4

>4 - 40

>40 - 70

>70

PFBS Results (ng/L)

ND

>ND - 100

>100 - 601

>601 - 2,000

>2,000

AECOM 6-14
AOI01-01

EF-01

EF-02

AOI01-02

MWELL02-01

MWELL02-02

Legend

Approximate Corrected Facility Boundary

Facility Boundary

Groundwater Flow Direction

12420 Milestone Center Drive

Germantown, MD 20876 Figure 6-7

PFHxS and PFNA Detections

 in Groundwater

5/8/2023

5/8/2023

MS 5/8/2023

SW

CM

GIS BY

CHK BY

PM

5/8/2023

CLIENT

REVISED

SCALE

PROJECT

ARNG

Site Inspection at Ellington Field, TX

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

the GIS User Community

1:2,640

AOI01-01

EF-01

EF-02

AOI01-02

MWELL02-01

MWELL02-02

PFHxS

PFNA

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

0 110

­

220 440

Feet

PFHxS Results (ng/L)

ND

>ND - 39

>39 - 100

>100 - 1,000

>1,000

PFNA Results (ng/L)

ND

>ND - 6

>6 - 100

>100 - 1,000

>1,000

AECOM 6-15
spection Report

on Field Army Aviation Support Facility, Houston, Texas

THIS PAGE INTENTIONALLY BLANK
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 7-1

7. Exposure Pathways

The CSMs for each AOI, revised based on the SI findings, are presented on Figure 7-1. Please 

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

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

SLs for the relevant compounds and whether the release is more than likely attributable to the 

DoD. A CSM presents the current understanding of the site conditions with respect to known and 

suspected sources, potential transport mechanisms and migration pathways, and potentially 

exposed human receptors. A human exposure pathway is considered potentially complete when 

the following conditions are present:

1. Contaminant source;

2. Environmental fate and transport;

3. Exposure point;

4. Exposure route; and

5. Potentially exposed populations.

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

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

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

relevant compounds are detected and the other four elements are satisfied, in which case the CSM 

figure uses a half-filled circle symbol to represent a potentially complete exposure pathway. 

Additionally, a completely filled circle symbol is used to indicate when a potentially complete 

exposure pathway has detections of relevant compounds above the SLs. Areas with an identified 

potentially complete pathway that have detections of the relevant compounds above the SLs may 

warrant further investigation. Although the CSMs indicate whether potentially complete exposure 

pathways may exist, the recommendation for future study in an RI or no action at this time is 

based on the comparison of the SI analytical results for the relevant compounds to the SLs. 

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

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

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

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

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

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

workers, trespassers, residents outside the facility boundary, and recreational users outside of 

the facility boundary. 

7.1 Soil Exposure Pathway 

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

between the source and potential receptors at AOI 1 and AOI 2 based on the aforementioned 

criteria. 

7.1.1 AOI 1

AOI 1 is the Wash Rack, where TXARNG and TXANG personnel trained with Tri-MaxTM units 

once a year from the early 1990s until around 2010 when AFFF at the facility was donated to the 

TXANG fire department, and Tri-MaxTM units were replaced with Purple K units. 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 7-2

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in surface soil at AOI 1. Site workers, 

future construction workers (no current construction on the facility), and trespassers could contact 

constituents in surface soil via incidental ingestion and inhalation of dust. Therefore, the surface

soil exposure pathways for these receptors are potentially complete. The nearest recreational 

area, Pasadena Municipal Golf Course is located approximately 620 feet west of the facility. The 

nearest residence is approximately 0.9 miles northeast of the facility. Therefore, the surface soil 

exposure pathways for off-facility residents and recreational users are considered incomplete. 

PFOA, PFOS, PFHxS, and PFBS were detected in subsurface soil at AOI 1. Construction workers 

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

subsurface soil exposure pathway for future construction workers is potentially complete. The 

CSM for AOI 1 is presented on Figure 7-1. 

7.1.2 AOI 2

AOI 2 is the Flight Line, where TXARNG and TXANG personnel trained with Tri-MaxTM units once 

a year until around 2010 when AFFF at the facility was donated to the TXANG fire department,

and Tri-MaxTM units were replaced with Purple K units.

PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in surface soil at AOI 2. The potential 

receptors and pathways for surface soil are the same as described above for AOI 1. Though no 

subsurface soil samples were collected at AOI 2, the relevant compounds were detected in 

surface soil and these impacts could leach into subsurface soil via precipitation. Construction 

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

subsurface soil exposure pathway for future construction workers is potentially complete. The 

CSM for AOI 2 is presented on Figure 7-1. 

7.2 Groundwater Exposure Pathway

The SI results in groundwater at AOI 1 were used to determine whether a potentially complete 

pathway exists between the source and potential receptors based on the aforementioned criteria.

Though no groundwater samples were collected within AOI 2, the SI result in soil within AOI 2 and 

groundwater upgradient from AOI 2, were used to determine whether a potentially complete 

pathway exists between the source and potential receptors.

7.2.1 AOI 1

PFOA, PFOS, PFHxS, and PFBS were detected above their SLs in groundwater samples 

collected at AOI 1. Five public supply wells and 11 domestic wells were identified within a 4-mile 

radius of the facility; however, none of these wells are located downgradient of the facility. 

Therefore, the pathway for exposure to off-facility residents via ingestion of groundwater is 

considered incomplete. Drinking water at the facility is supplied by the City of Houston; therefore, 

the groundwater exposure pathway for site workers via direct ingestion of groundwater is 

considered incomplete. Depths to water measured at AOI 1 in June 2022 during the SI ranged 

from 5.00 to 8.67 feet bgs. Therefore, the incidental ingestion exposure pathway for future 

construction workers during construction activities is considered potentially complete. The CSM

for AOI 1 is presented on Figure 7-1. 

7.2.2 AOI 2

Though no groundwater samples were collected within AOI 2 (the entire area is covered by 

concrete), PFOA, PFOS, PFHxS, and PFBS were detected above their SLs in groundwater 

samples collected upgradient and cross-gradient of AOI 2. While runoff from the Flight Line 

appears to be primarily directed to Stormwater Discharge Outfall 005, it is uncertain whether some 

runoff around the edges of the Flight Line could flow into nearby unpaved areas, especially in the 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 7-3

vicinity of MW-ELL02-01, potentially impacting groundwater. Five public supply wells and 11 

domestic wells were identified within a 4-mile radius of the facility; however, none of these wells 

are located downgradient of the facility. Therefore, the pathway for exposure to off-facility 

residents via ingestion of groundwater is considered incomplete. Drinking water at the facility is 

supplied by the City of Houston; therefore, the groundwater exposure pathway for site workers 

via direct ingestion of groundwater is considered incomplete. Depths to water measured in wells 

nearby AOI 2 in June 2022 during the SI ranged from 4.14 to 5.62 feet bgs. Therefore, the 

incidental ingestion exposure pathway for future construction workers during construction 

activities is considered potentially complete. The CSM for AOI 2 is presented on Figure 7-1. 

7.3 Surface Water and Sediment Exposure Pathway

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

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

between the source and potential receptors.

7.3.1 AOI 1

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

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

the facility’s surface water drainage system which contains multiple ditches/channels for surface 

flow. Therefore, the surface water and sediment ingestion exposure pathways for site workers, 

future construction workers, and trespassers are considered potentially complete. Stormwater 

moves by open channel flow and underground drainage pipes until the runoff reaches Horsepen 

Bayou, eventually combining with Armand Bayou. Therefore, the surface water and sediment 

ingestion exposure pathway for off-facility recreational users is considered potentially complete. 

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

7.3.2 AOI 2 

Because PFOA, PFOS, PFHxS, PFNA, and PFBS were detected in soil at AOI 2, it is possible 

that those compounds may have migrated from soil and groundwater to the facilities surface water 

drainage system which contains multiple ditches/channels for surface flow. Therefore, the 

receptors and pathways described above for AOI 1 are also possible at AOI 2. The CSM for AOI 

2 is presented on Figure 7-1. 
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 7-4

THIS PAGE INTENTIONALLY BLANK
Media

SOURCE PATHWAY RECEPTOR

AOI 1

AOI 2

Mobile Fire 

Extinguishers 

Discharge

Surface soil

Human 

activities

Precipitation/ 

run-off

Leaching/ 

infiltration

Airborne soil 

particulate

Surface soil 

at AOI

Surface 

water/ 

sediment

Subsurface 

soil

Shallow 

groundwater

Source Release 

Mechanism Media Transport and Migration Media Exposure Routes

Inhalation of 

dust

Ingestion

Ingestion

Ingestion

Ingestion

Human Receptors: 

Current/ Future

Flow-Chart Continues

Partial/ Possible Flow

Flow-Chart Stops

Incomplete Pathway

Potentially Complete Pathway

Potentially Complete Pathway 

with Exceedance of SL

/ / / /

Site Worker Construction Worker3 Resident1,2 Trespasser/ Recreational User1

Site Worker Construction Worker3 Resident1,2

/ / / /

/ / / /

/ / / /

/ / / /

LEGEND

Figure 7-1

Conceptual Site Model, AOI 1 and AOI 2

Ellington Field AASF

Potential 

Off-Facility 

Source Not 

under 

Control of 

ARNG

Trespasser/ Recreational User1

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

2. Inhalation of dust for off-site receptors is likely

insignificant.

3. No current active construction at the facility.

Notes:

AECOM 7-5 
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M 7-6
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 8-1

8. Summary and Outcome

This section summarizes SI activities and findings. The most significant findings are summarized 

in this section and are reproduced directly or abstracted from information contained in this report. 

The outcome provides general and comparative interpretations of the findings relative to the SLs. 

8.1 SI Activities

The SI field activities were conducted from 1 to 9 June 2022 and consisted of utility clearance, direct 

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

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

Addendum (AECOM, 2022b), except as previously noted in Section 5.8. 

To fulfill the project DQOs set forth in the approved SI QAPP Addendum (AECOM, 2022b), samples 

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

Table B-15 as follows. 

• Sixteen (16) soil samples from four boring locations and four hand auger locations;

• Four grab groundwater samples from four temporary wells and two groundwater samples

from two existing permanent wells;

• Twelve (12) quality assurance QA/QC samples.

An SI is conducted when the PA determines an AOI exists based on probable use, storage, and/or 

disposal of PFAS-containing materials. The SI includes multi-media sampling at AOIs to 

determine whether or not a release has occurred. The SI may conclude further investigation is 

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

required. Additionally, the CSMs were refined to assess whether a potentially complete pathway 

exists between the source and potential receptors for potential exposure at the AOIs, which are 

described in Section 7. 

8.2 Outcome 

Based on the results of this SI, further evaluation under CERCLA is warranted in an RI for AOI 1

and AOI 2 (see Table 8-1). Based on the CSMs developed and revised in light of the SI findings, 

there is no potential for exposure to drinking water receptors from AOI 1 and AOI 2 from sources 

on the facility resulting from historical DoD activities. Sample analytical concentrations collected 

during the SI were compared to the project SLs in soil and groundwater, as described in Table 6-

1. A summary of the results of the SI data relative to the SLs is as follows:

• At AOI 1:

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

AOI 1 were below their SLs.

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

following maximum concentrations: PFOA at 151 J ng/L, PFOS at 2,150 J ng/L,

PFHxS at 17,700 J ng/L, and PFBS at 2,750 J ng/L. PFNA was detected below the

SL in groundwater. The PFOS exceedance detected in the sample collected from

upgradient well EF-02 may indicate a potential unknown off-facility source.

• Based on the exceedances of the SLs in groundwater, further evaluation of AOI 1 is

warranted in an RI.
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 8-2

• At AOI 2: 

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

AOI 2 were below their SLs. 

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

following maximum concentrations: PFOA at 206 J ng/L, PFOS at 4,010 J ng/L, 

PFHxS at 3,260 J ng/L, and PFNA at 30.3 J ng/L. PFBS was detected below the SL 

in groundwater. These exceedances were detected in samples collected upgradient 

of AOI 2 and may indicate a potential unknown off-facility source.

• Based on the exceedances of the SLs in groundwater surrounding AOI 2 in 

combination with the detections in soil at AOI 2, further evaluation at AOI 2 is 

warranted. 

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 Wash Rack Proceed 

to RI 

2 Flight Line N/A Proceed 

to RI

Legend:

N/A = not applicable 

= detected; exceedance of the screening levels

= detected; no exceedance of the screening levels

= not detected
Site Inspection Report

Ellington Field Army Aviation Support Facility, Houston, Texas

AECOM 9-1

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Reconnaissance Wing, Ellington Field Joint Reserve Base, Texas Air National Guard, 

Houston, Texas. May

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

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

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Facility, Houston, Texas. July. 

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Impacted Sites ARNG Installations, Nationwide. May. 

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AECOM 9-2

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