1. UK510_Scott AFB_Final RI Addendum (RPM needs to add to AR).pdf

DEPARTMENT OF THE AIR FORCE

AIR FORCE CIVIL ENGINEER CENTER

JOINT BASE SAN ANTONIO LACKLAND TEXAS

19 March 2025

MEMORANDUM FOR Illinois Environmental Protection Agency ATTN: Mr. Jordan Simpkins Bureau of Land

Federal Site Remediation Section 1021 North Grand Ave. East Springfield, IL 62794-9276

FROM: Joseph Weber

AFCEC/CZOM

701 Hangar Road, Bldg 531

Scott AFB, IL 62225-5035

SUBJECT: Final Remedial Investigation Addendum, Site UK510, March 2025, Scott Air Force Base (AFB), IL

1. The Air Force submits the Final Remedial Investigation Addendum, Site UK510, March 2025, Scott AFB, IL for your files. Two copies of the document with red-line/strike-out format have been provided to document revisions completed based on comments and responses in the Illinois EPA February 6, 2025, letter.

2. The Air Force believes the Illinois EPA will accept these revisions based on prior correspondence and meetings as summarized in the Illinois EPA February 6, 2025, letter. Two copies of the final version without red-line/strike-out for the Final Remedial Investigation Addendum, Site UK510, March 2025, Scott AFB, IL are also provided.

3. If you have any questions, please contact me at 618-256-2125 or email joseph.weber.16 @us.af.mil.

Joseph Weber Restoration Project Manager cc: Ben Christensen, URS

Patrick Reilley, Plexus Eliud Burgos, AFCEC/CZR

FINAL

REMEDIAL INVESTIGATION ADDENDUM

SITE UK510

Scott Air Force Base

Prepared for:

2261 Hughes Avenue, Suite 155

Lackland AFB, Texas 78236-9853

Contract FA8903-14-C-0009

March 2025

FINAL

Remedial Investigation Addendum Site UK510

Scott Air Force Base

Prepared for:

2261 Hughes Avenue, Suite 155 Lackland AFB, Texas 78236-9853

Contract FA8903-14-C-0009

March 2025

Prepared by:

URS Group, Inc.

12120 Shamrock Plaza, Suite 300 Omaha, Nebraska 68154

In Association With:

TABLE OF CONTENTS

Final Remedial Investigation Addendum, Site UK510 i Scott AFB PBR

FA8903-14-C-0009

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

1.1 Authority .................................................................................................. 1-1

1.2 Purpose and Scope ................................................................................... 1-1

1.3 Report Organization ................................................................................. 1-2

2 Risk Assessment ............................................................................................................ 2-1

2.1 Human Health Risk Assessment .............................................................. 2-1

2.1.1 Revised Risk for Future Construction/Excavation Worker

Scenario........................................................................................ 2-1

2.1.2 Uncertainty Analysis .................................................................... 2-2

3 Summary and Conclusions ........................................................................................... 3-1

3.1 Summary of Key Findings ....................................................................... 3-1

3.2 Conclusions .............................................................................................. 3-1

4 References ...................................................................................................................... 4-1

TABLE OF CONTENTS

Final Remedial Investigation Addendum, Site UK510 ii Scott AFB PBR

FA8903-14-C-0009

List of Tables Table 2-1 Parameters Used to Evaluate Potential Exposure to Non-Mutagenic

Chemicals in Sediment for the Construction/Excavation Worker Table 2-2 Ingestion of Chemicals in Sediment – Maximum Detected Concentrations (Future

Construction/Excavation Worker – Reasonable Maximum Exposure) Table 2-3 Dermal Exposure to Chemicals in Sediment – Maximum Detected Concentrations

(Future Construction/Excavation Worker – Reasonable Maximum Exposure) Table 2-4 Ingestion of Background Concentrations of Chemicals in Sediment (Future Construction/Excavation Worker – Reasonable Maximum Exposure) Table 2-5 Dermal Exposure to Background Concentrations of Chemicals in Sediment (Future Construction/Excavation Worker – Reasonable Maximum Exposure) Table 2-6 Summary of Cancer Risks and Adverse Health Effects for the Future

Construction/Excavation Worker Exposed to Maximum Detected Concentrations

List of Figures Figure 1-1 Site Location Map Figure 1-2 Western Portion of UK510 Figure 1-3 Eastern Portion of UK510

List of Appendix Appendix A Regulatory Correspondence

ACRONYMS AND ABBREVIATIONS

Final Remedial Investigation Addendum, Site UK510 iii Scott AFB PBR

FA8903-14-C-0009

95UCL

AFB

95 percent upper confidence limit Air Force Base

AFCEC Air Force Civil Engineer Center bgs below ground surface BHRA baseline human health risk assessment CERCLA Comprehensive Environmental Response, Compensation, and

Liability Act COPC chemical of potential concern EPC exposure point concentration FS Feasibility Study HI hazard index

IEPA

LUC

Illinois Environmental Protection Agency land use control

PBR performance-based remediation Plexus Plexus Scientific Corporation RI Remedial Investigation RME reasonable maximum exposure UK510 South Ditch, Site UK510 URS URS Group, Inc.

USEPA United States Environmental Protection Agency

SECTIONONE Introduction

Final Remedial Investigation Addendum, Site UK510 1-1 Scott AFB PBR

FA8903-14-C-0009

This document presents an addendum to the Remedial Investigation (RI) portion of the Final UK510 RI / Feasibility Study (FS) (Final UK510 RI/FS; URS Group, Inc. [URS] 2022) for the South Ditch, Site UK510 (UK510) at Scott Air Force Base (AFB), St. Clair County, Illinois. The location of Scott AFB and UK510 are shown on Figure 1-1.

1.1 AUTHORITY

The Air Force Civil Engineer Center (AFCEC) contracted Plexus Scientific Corporation (Plexus) under Contract Number FA8903-14-C-0009 to complete performance-based remediation (PBR) at Scott AFB under the Environmental Restoration Program. URS is subcontracted to Plexus to complete the contract performance objective for UK510. Remedial action at UK510 and Scott AFB are being conducted under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended by the Superfund Amendments and Reauthorization Act requirements, and the National Oil and Hazardous Substances Pollution Contingency Plan.

Regulatory oversight is led by the Illinois Environmental Protection Agency (IEPA). There is not a Federal Facility Agreement for Scott AFB.

1.2 PURPOSE AND SCOPE

URS prepared this RI Addendum on behalf of AFCEC to document a revision to the baseline human health risk assessment (BHRA) presented in the Final UK510 RI/FS (URS 2022) for the future construction/excavation worker exposure scenario. The BHRA concluded there was an unacceptable risk under a future construction/excavation worker scenario when risk for this receptor was evaluated using maximum detected concentrations in sediment (0 to 0.5 feet below ground surface [bgs]) and subsurface soil (0.5 to 3 feet bgs) and United States Environmental Protection Agency (USEPA) default exposure parameters for a construction worker (e.g., 250 days per year for 1 year) (URS 2022). The maximum detected concentrations were used as the exposure point concentrations (EPCs) in accordance with IEPA guidance. Using these EPCs and the USEPA default exposure parameters resulted in a cancer risk of 6E-06 and noncancer hazard index (HI) of

2. The HI exceeded the threshold of 1 with manganese and aroclors as the primary chemicals of potential concern (COPCs) contributing to the HI of 2. Based on a target organ evaluation, the manganese HI of 0.83 estimated for the central nervous system was below the threshold of 1. For aroclors, a target organ HI of 1.6 estimated for the skin and eye exceeded the threshold of 1.

However, when evaluating a short-term construction worker scenario, although IEPA recommends use of the maximum detected concentration, the IEPA scenario incorporates an exposure frequency of 30 days and exposure duration of 6 weeks (42 days/year or 0.115 year). Therefore, use of maximum detected concentrations as the EPCs over a 1-year exposure duration overestimates risk for the IEPA short-term construction worker scenario. During a meeting on January 17, 2024, the United States Air Force and IEPA agreed to a revision of the BHRA to address the IEPA short-term construction worker scenario using the correct exposure parameters.

Site UK510 is a nonpoint source drainage ditch that flows along the southern border of Scott AFB (Figures 1-2 and 1-3). It is unlikely any receptor, to include a construction/excavation worker, 1 Introduction

SECTIONONE Introduction

Final Remedial Investigation Addendum, Site UK510 1-2 Scott AFB PBR

FA8903-14-C-0009

would spend the majority of their time (e.g., 250 days/year for 1 year) at the site at the individual sample locations where the maximum detected concentrations were identified. Therefore, the BHRA also evaluated a future construction/excavation worker scenario using 95 percent upper confidence limit (95UCL) concentrations along with the default USEPA exposure parameters for a construction worker (URS 2022). No unacceptable risk was identified for the future construction/excavation worker using the 95UCL and the default USEPA exposure parameters.

The revision to the BHRA addressed in this RI Addendum is discussed in Section 2. No new data were collected for this RI Addendum. Sediment (0 to 0.5 feet bgs) and subsurface soil (0.5 to 3 feet bgs) sampling at UK510 was completed in two phases in 2012 by Shaw Environmental & Infrastructure, Inc. In accordance with the Final UK510 Supplemental RI Work Plan (URS 2019), additional sediment and subsurface soil sampling was completed in 2017 by URS at select locations to define the extent (i.e., upgradient and downgradient) of contamination within the South Ditch. Supplemental RI sample locations also included the inlet and outlet of drainage culverts within the South Ditch, which were not sampled in 2012, and storm water conduits (via inlets and manholes) that convey storm water from upgradient industrial and residential areas into the South Ditch, which were not sampled in 2012. In accordance with the Final UK510 Supplemental RI Work Plan (URS 2019), analytical data collected during the 2012 and 2017 sampling events were combined to form a comprehensive data set for sediment and subsurface soil for use in the Final UK510 RI/FS BHRA and the revised BHRA for this RI Addendum. Future construction/excavation workers have no exposure to surface water.

1.3 REPORT ORGANIZATION

This RI Addendum only includes the revised sections from the BHRA of the Final UK510 RI/FS, as shown below. The Final UK510 RI/FS (URS 2022) should be referenced for any needed supporting information.

Section 1 presents the introduction, including authority, purpose and scope, and report organization.

Section 2 presents the revised BHRA.

Section 3 presents the RI Addendum conclusions.

Section 4 presents a list of references cited in this RI Addendum.

Site Location Map Scott AFB, Ill inois

Figure 1-1 Drawn By:

DPG

Checked By:

NEL

Date:

Project No.

10/9/2018

60442717

Legend

Installation Boundary

UK510

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Figure 1-2

Western Portion of UK510 Scott AFB, Illinois

Final Remedial Investigation Addendum, Site UK510

Coordinate System: NAD 1983 StatePlane Illinois West FIPS 1202 Feet, Projection: Transverse Mercator, Datum: North American 1983

BL

UK510

3165A

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Storm Water Conveyance and Discharge Structures Lined

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Site Locations

Installation Area

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60442717

Figure 1-3

Eastern Portion of UK510 Scott AFB, Illinois

Final Remedial Investigation Addendum, Site UK510

Coordinate System: NAD 1983 StatePlane Illinois West FIPS 1202 Feet, Projection: Transverse Mercator, Datum: North American 1983

BL

SECTIONTWO Risk Assessment

Final Remedial Investigation Addendum, Site UK510 2-1 Scott AFB PBR

FA8903-14-C-0009

The BHRA in the Final UK510 RI/FS (URS 2022) was summarized in Sections 8.1 and 9 and discussed in greater detail in Appendix E. This section discusses the revised BHRA to address the IEPA future construction/excavation worker scenario where the maximum detected COPC concentrations in sediment and subsurface soil were used as the EPCs along with the IEPA exposure frequency and duration for a short-term construction worker scenario.

2.1 HUMAN HEALTH RISK ASSESSMENT

The revised BHRA in this RI Addendum follows the methodologies presented in Appendix E of the Final UK510 RI/FS (URS 2022) with the following exceptions:

• Evaluates the applicable exposure routes for the future construction/excavation worker scenario only.

• Uses only maximum detected COPC concentrations in sediment and subsurface soil for exposure point concentrations.

• Uses IEPA exposure parameters of 30 days per year for exposure frequency and 6 weeks (42 days or 0.115 year) for exposure duration for the short-term construction worker scenario.

The risk assessment elements identified in the preceding bullets were agreed upon during a meeting between the United States Air Force and IEPA on January 17, 2024. No new data were collected for revision of the BHRA.

Table 2-1 shows the exposure parameters used in the revised risk assessment.

Tables 2-2 and 2-3 show the estimated risks for ingestion and dermal exposures under the reasonable maximum exposure (RME) scenario using maximum detected COPC concentrations in sediment and subsurface soil and IEPA exposure parameters for short-term construction worker scenario.

Tables 2-4 and 2-5 show the estimated risks for ingestion and dermal exposures under the RME scenario using background concentrations. Background risks were also estimated using the IEPA exposure values of 30 days per year for exposure frequency and 6 weeks (42 days or 0.115 year) for exposure duration.

Table 2-6 summarizes the revised future construction/excavation worker site risks and background risks.

2.1.1 Revised Risk for Future Construction/Excavation Worker Scenario

Site UK510 is expected to continue to receive runoff from the upgradient industrial and residential areas of Scott AFB (Figures 1-2 and 1-3). Planned future use of the site is anticipated to be commercial/industrial. In the Final UK510 RI/FS (URS 2022), the only receptor scenario where an unacceptable risk was identified was for the future construction/excavation worker scenario assuming exposure to the maximum detected COPC concentrations in sediment and subsurface

2 Risk Assessment

SECTIONTWO Risk Assessment

Final Remedial Investigation Addendum, Site UK510 2-2 Scott AFB PBR

FA8903-14-C-0009

soil, exposure frequency of 250 days per year, and exposure duration of 1 year. The results of the revised BHRA for the IEPA short-term construction worker scenario are as follows:

• Revised Future Construction/Excavation Worker Risks – Maximum Detected Concentrations: The cumulative cancer risk for ingestion and dermal exposures to maximum detected COPC concentrations in sediment and subsurface soil was 9E-08, which is below the USEPA risk management range of 1E-06 to 1E-04. No individual COPC had an estimated cancer risk greater than 1E-06. The noncancer HI was 0.3, which is below the threshold of 1. Therefore, maximum detected COPC concentrations in sediment and subsurface soil at UK510 are unlikely to pose unacceptable cancer risks or adverse health effects for future construction/excavation workers under the IEPA short-term construction worker scenario. Site risk and hazards calculations are summarized in Table 2-6.

• Similar to the BHRA of the Final UK510 RI/FS (URS 2022), background risk and hazard calculations were completed for aroclors and metal COPCs to distinguish naturally occurring constituents (metals) and anthropogenic background concentrations (aroclors) from those that are site related. All other constituents (i.e., organics) were assumed to be site-related if detected; therefore, no background comparison was completed. Part of the site risks can be attributed to background concentrations of these inorganic chemicals resulting in a potential overestimation of site risks. The background sediment data was obtained from IEPA unsieved stream data (Short 1997). Methodologies related to the calculation of background risks are provided in Appendix E of the Final UK510 RI/FS (URS 2022). Background risk and hazards calculations are summarized in Table 2-6.

Background COPC concentrations are unlikely to pose unacceptable cancer risks or adverse health effects for future construction/excavation workers under the IEPA short-term construction worker scenario.

Construction/excavation workers have no exposure to surface water. Occupational Safety and Health Administration requirements for excavation activities prevent construction workers from working inside an excavation with standing water.

2.1.2 Uncertainty Analysis

The uncertainties and limitations of this revised BHRA for the future construction/excavation worker scenario are the same as those discussed in Section 8.1 and Appendix E of the Final UK510 RI/FS (URS 2022) and are not repeated here.

TABLE 2-1

PARAMETERS USED TO EVALUATE POTENTIAL EXPOSURE TO

NON-MUTAGENIC CHEMICALS IN SEDIMENT FOR THE CONSTRUCTION/EXCAVATION WORKER

SITE UK510

SCOTT AIR FORCE BASE, ILLINOIS

Sediment Ingestion Rate [IRsed] (mg/day)

Exposed Dermal Surface Area - Sediment [SA] (cm2/event)

Sediment Adherence Factor [AF] (mg/cm2) Dermal Absorption Fraction [ABS] (unitless)

Exposure Frequency for sediment [EF] (days per year)

Exposure Duration [ED] (years)

Body Weight [BW] (kg)

Averaging Time - Non-carcinogens [ATnc] (days)

Averaging Time - Carcinogens [ATc] (days)

Notes:

Replaces Table E-12 in Appendix E of the Final Remedial Investigation/Feasibility Study (URS Group, Inc. 2022).

a Based on high end value for adult soil intake rates (USEPA 2002).

d Dermal absorption fraction of 13 percent for PAHs, 14 percent for PCBs, and chemical-specific values (USEPA 2004).

g Standard default body weight for an adult (USEPA 2014).

i The Averaging Time for carcinogenic effects is based on total lifespan of 70 years (USEPA 2014).

Acronyms and Abbreviations: Units:

HGL = HydroGeoLogic, Inc. cm2/event = square centimeters per event

IEPA = Illinois Environmental Protection Agency kg = kilograms

PAH = polynuclear aromatic hydrocarbon mg/cm2 = milligrams per square centimeter

PCB = polychlorinated biphenyl mg/day = milligrams per day

RME = Reasonable Maximum Exposure

USEPA = United States Environmental Protection Agency.

0.3c

30e

0.115f

80g

42h

Exposure Parameters Construction/Excavation Worker

RME

330a

3,300b c Soil adherence factors for construction/excavation workers are from Exhibit 3-3 (USEPA 2004). RME value is also recommended by the Final Risk Assessment Approach Technical Memorandum (HGL 2009).

f The exposure duration was determined by 42 days divided by 365 days per year based on the IEPA short-term construction worker scenario discussed by the United States Air Force and IEPA during a meeting on January 17, 2024.

e The exposure frequency was determined by 5 days per week for 6 weeks based on the IEPA short-term construction worker scenario discussed by the United States Air Force and IEPA during a meeting on January 17, 2024.

h The Averaging Time for non-carcinogenic effects was determined by 7 days per week for 6 weeks (42 days) based on the IEPA short-term construction worker scenario discussed by the United States Air Force and IEPA during a meeting on January 17, 2024.

Chemical-specificd

25,550i b Construction/excavation worker surface area values are the central tendency industrial value (USEPA 2004) and recommended by Final Risk Assessment Approach Technical Memorandum (HGL 2009) for exposure to sediments.

Final Remedial Investigation Addendum, Site UK510 Scott AFB PBR

FA8903-14-C-0009

TABLE 2-2

INGESTION OF CHEMICALS IN SEDIMENT - MAXIMUM DETECTED CONCENTRATIONS

(FUTURE CONSTRUCTION/EXCAVATION WORKER - REASONABLE MAXIMUM EXPOSURE)

SITE UK510

SCOTT AIR FORCE BASE, ILLINOIS

Chemical CS IRs EF ED CF BW ATnc ATc CDInc Subchronic RfD HQ CDIc SF CR

(mg/kg) (mg/day) (days/year) (years) (kg/mg) (kg) (days) (days) (mg/kg-day) (mg/kg-day) (unitless) (mg/kg-day) (mg/kg-day)-1 (unitless)

PAHs

1-Methylnaphthalene 4.30E-01 330 30 0.115 1.00E-06 80 42 25,550 1.46E-07 7.00E-02 0.000002 2.40E-10 2.90E-02 6.95E-12

2-Methylnaphthalene 5.40E-01 330 30 0.115 1.00E-06 80 42 25,550 1.83E-07 4.00E-03 0.00005 3.01E-10 N/A N/A

Benzo(a)anthracene 5.92E+01 330 30 0.115 1.00E-06 80 42 25,550 2.01E-05 N/A N/A 3.30E-08 1.00E-01 3.30E-09

Benzo(a)pyrene 6.27E+01 330 30 0.115 1.00E-06 80 42 25,550 2.12E-05 4.00E-03 0.005 3.49E-08 1.00E+00 3.49E-08

Benzo(b)fluoranthene 9.31E+01 330 30 0.115 1.00E-06 80 42 25,550 3.15E-05 N/A N/A 5.19E-08 1.00E-01 5.19E-09

Benzo(k)fluoranthene 2.94E+01 330 30 0.115 1.00E-06 80 42 25,550 9.96E-06 N/A N/A 1.64E-08 1.00E-02 1.64E-10

Chrysene 6.88E+01 330 30 0.115 1.00E-06 80 42 25,550 2.33E-05 N/A N/A 3.83E-08 1.00E-03 3.83E-11

Dibenz(a,h)anthracene 9.85E+00 330 30 0.115 1.00E-06 80 42 25,550 3.34E-06 N/A N/A 5.49E-09 1.00E+00 5.49E-09

Indeno(1,2,3-cd)pyrene 4.87E+01 330 30 0.115 1.00E-06 80 42 25,550 1.65E-05 N/A N/A 2.71E-08 1.00E-01 2.71E-09

PCBs

Aroclor 1248 1.94E+00 330 30 0.115 1.00E-06 80 42 25,550 6.57E-07 3.00E-05 0.022 1.08E-09 2.00E+00 2.16E-09

Aroclor 1254 7.33E+00 330 30 0.115 1.00E-06 80 42 25,550 2.48E-06 3.00E-05 0.083 4.08E-09 2.00E+00 8.17E-09

Aroclor 1260 2.52E+00 330 30 0.115 1.00E-06 80 42 25,550 8.54E-07 3.00E-05 0.028 1.40E-09 2.00E+00 2.81E-09

Metals

Manganese 5.91E+03 330 30 0.115 1.00E-06 80 42 25,550 2.00E-03 2.00E-02 0.100 3.29E-06 N/A N/A

TOTAL HAZARD INDEX = 0.2 TOTAL CANCER RISK = 6.49E-08

Notes:

Replaces Table E2-17 in Appendix E, Attachment E-2 of the Final Remedial Investigation/Feasibility Study (URS Group, Inc. 2022).

Equations:

CDI = (CS x IRs x EF x ED x CF)/(BW x ATnc or ATc)

HQ = CDI / RfD

CR = SF x CDI

Acronyms and Abbreviations: Units:

ATc = Averaging Time for Carcinogenic Effects, Based on Lifetime (days) EF = Exposure Frequency (days/year) kg = kilograms

ATnc = Averaging Time for Non-carcinogenic Effects (days) HQ = Hazard Quotient (unitless) kg/mg = kilograms per milligram

BW = Body Weight (kg) IRs = Soil Ingestion Rate (mg/day) mg/day = milligrams per day

CDIc = Chronic Daily Intake for Cancer Effects (mg/kg-day) N/A = not applicable mg/kg = milligrams per kilogram

CDInc = Chronic Daily Intake for Non-Cancer Effects (mg/kg-day) PAH = polynuclear aromatic hydrocarbon mg/kg-day = milligrams per kilogram-day

CF = Conversion Factor (kg/mg) PCB = polychlorinated biphenyl

CR = Cancer Risk (unitless) RfD = Reference Dose (mg/kg-day)

CS = Chemical Concentration in Soil (mg/kg) - maximum detected concentration SF = Slope Factor (mg/kg-day)-1

ED = Exposure Duration (years)

The exposure frequency (EF) was revised from 250 days/year to 30 days/year and the exposure duration (ED) was revised to 0.115 year based on meeting between United States Air Force and Illinois Environmental Protection Agency (IEPA) on January 17, 2024. The change in ED resulted in change of averaging time for non-carcinogenic effects (ATnc) to 42 days (7 days per week for 6 weeks). The ED value (0.115 years) was calculated (42 days divided by 365 days per year). These changes are based on the IEPA short-term construction worker scenario.

Final Remedial Investigation Addendum, Site UK510

TABLE 2-3

DERMAL EXPOSURE TO CHEMICALS IN SEDIMENT - MAXIMUM DETECTED CONCENTRATIONS

(FUTURE CONSTRUCTION/EXCAVATION WORKER - REASONABLE MAXIMUM EXPOSURE)

SITE UK510

SCOTT AIR FORCE BASE, ILLINOIS

Chemical CS SA AF ABS EF ED CF BW ATnc ATc CDInc Subchronic RfD HQ CDIc SF CR

(mg/kg) (cm2/event) (mg/cm2) (unitless) (days/year) (years) (kg/mg) (kg) (day) (days) (mg/kg-day) (mg/kg-day) (unitless) (mg/kg-day) (mg/kg-day)-1 (unitless)

PAHs

1-Methylnaphthalene 4.30E-01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 5.68E-08 7.00E-02 0.0000008 9.34E-11 2.90E-02 2.71E-12

2-Methylnaphthalene 5.40E-01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 7.14E-08 4.00E-03 0.000018 1.17E-10 N/A N/A

Benzo(a)anthracene 5.92E+01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 7.82E-06 N/A N/A 1.29E-08 1.00E-01 1.29E-09

Benzo(a)pyrene 6.27E+01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 8.29E-06 4.00E-03 0.0021 1.36E-08 1.00E+00 1.36E-08

Benzo(b)fluoranthene 9.31E+01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 1.23E-05 N/A N/A 2.02E-08 1.00E-01 2.02E-09

Benzo(k)fluoranthene 2.94E+01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 3.89E-06 N/A N/A 6.39E-09 1.00E-02 6.39E-11

Chrysene 6.88E+01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 9.09E-06 N/A N/A 1.49E-08 1.00E-03 1.49E-11

Dibenz(a,h)anthracene 9.85E+00 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 1.30E-06 N/A N/A 2.14E-09 1.00E+00 2.14E-09

Indeno(1,2,3-cd)pyrene 4.87E+01 3,300 0.3 0.13 30 0.115 1E-06 80 42 25,550 6.44E-06 N/A N/A 1.06E-08 1.00E-01 1.06E-09

PCBs

Aroclor 1248 1.94E+00 3,300 0.3 0.14 30 0.115 1E-06 80 42 25,550 2.76E-07 3.00E-05 0.009 4.54E-10 2.00E+00 9.08E-10

Aroclor 1254 7.33E+00 3,300 0.3 0.14 30 0.115 1E-06 80 42 25,550 1.04E-06 3.00E-05 0.035 1.71E-09 2.00E+00 3.43E-09

Aroclor 1260 2.52E+00 3,300 0.3 0.14 30 0.115 1E-06 80 42 25,550 3.59E-07 3.00E-05 0.012 5.90E-10 2.00E+00 1.18E-09

Metals

Manganese 5.91E+03 3,300 0.3 N/A 30 0.115 1E-06 80 42 25,550 N/A N/A N/A N/A N/A N/A

TOTAL HAZARD INDEX = 0.06 TOTAL CANCER RISK = 2.57E-08

Notes:

Replaces Table E2-19 in Appendix E, Attachment E-2 of the Final Remedial Investigation/Feasibility Study (URS Group, Inc. 2022).

Equations:

CDI = (CS x SA x AF x ABS x EF x ED x CF)/(BW x ATnc or ATc)

HQ = CDI / RfD

CR = SF x CDI

Acronyms and Abbreviations: Units:

ABS = Percent Chemical Absorption Across Skin (unitless) ED = Exposure Duration (years) cm2/event = square centimeters per event

AF = Soil Adherence to Skin (mg/cm2) EF = Exposure Frequency (days/year) kg = kilograms

ATc = Averaging Time for Carcinogenic Effects, Based on Lifetime (days) HQ = Hazard Quotient (unitless) kg/mg = kilograms per milligram

ATnc = Averaging Time for Non-carcinogenic Effects (days) N/A = not applicable mg/cm2 = milligrams per square centimeter

BW = Body Weight (kg) PAH = polynuclear aromatic hydrocarbon mg/kg = milligrams per kilogram

CDIc = Chronic Daily Intake for Cancer Effects (mg/kg-day) PCB = polychlorinated biphenyl mg/kg-day = milligrams per kilogram-day

CDInc = Chronic Daily Intake for Non-Cancer Effects (mg/kg-day) RfD = Reference Dose (mg/kg-day)

CF = Conversion Factor (kg/mg) SA = Exposed Body Surface Area (cm2/event)

CR = Cancer Risk (unitless) SF = Slope Factor (mg/kg-day)-1

CS = Chemical Concentration in Soil (mg/kg) - maximum detected concentration

The exposure frequency (EF) was revised from 250 days/year to 30 days/year and the exposure duration (ED) was revised to 0.115 year based on meeting between United States Air Force and Illinois Environmental Protection Agency (IEPA) on January 17, 2024. The change in ED resulted in change of averaging time for non-carcinogenic effects (ATnc) to 42 days (7 days per week for 6 weeks). The ED value (0.115 years) was calculated (42 days divided by 365 days per year). These changes are based on the IEPA short-term construction worker scenario.

Final Remedial Investigation Addendum, Site UK510

TABLE 2-4

INGESTION OF BACKGROUND CONCENTRATIONS OF CHEMICALS IN SEDIMENT

(FUTURE CONSTRUCTION/EXCAVATION WORKER - REASONABLE MAXIMUM EXPOSURE)

SITE UK510

SCOTT AIR FORCE BASE, ILLINOIS

Chemical CS IRs EF ED CF BW ATnc ATc CDInc Subchronic RfD HQ CDIc SF CR

(mg/kg) (mg/day) (days/year) (years) (kg/mg) (kg) (days) (days) (mg/kg-day) (mg/kg-day) (unitless) (mg/kg-day) (mg/kg-day)-1 (unitless)

PCBs

Aroclor 1248 0.010 330 30 0.115 1.00E-06 80 42 25,550 3.39E-09 3.00E-05 0.000113 5.57E-12 2.00E+00 1.11E-11

Aroclor 1254 0.010 330 30 0.115 1.00E-06 80 42 25,550 3.39E-09 3.00E-05 0.000113 5.57E-12 2.00E+00 1.11E-11

Aroclor 1260 0.010 330 30 0.115 1.00E-06 80 42 25,550 3.39E-09 3.00E-05 0.000113 5.57E-12 2.00E+00 1.11E-11

Metals

Manganese 1100 330 30 0.115 1.00E-06 80 42 25,550 3.73E-04 2.00E-02 0.019 6.13E-07 N/A N/A

TOTAL HAZARD INDEX = 0.02 TOTAL CANCER RISK = 3.34E-11

Notes:

Background concentration (CS) is unsieved stream data (Short 1997).

Replaces Table E2-90 in Appendix E, Attachment E-2 of the Final Remedial Investigation/Feasibility Study (URS Group, Inc. 2022).

Equations:

CDI = (CS x IRs x EF x ED x CF)/(BW x ATnc or ATc)

HQ = CDI / RfD

CR = SF x CDI

Acronyms and Abbreviations: Units:

ATc = Averaging Time for Carcinogenic Effects, Based on Lifetime (days) ED = Exposure Duration (years) kg = kilograms

ATnc = Averaging Time for Non-carcinogenic Effects (days) EF = Exposure Frequency (days/year) kg/mg = kilograms per milligram

BW = Body Weight (kg) HQ = Hazard Quotient (unitless) mg/day = milligrams per day

CDIc = Chronic Daily Intake for Cancer Effects (mg/kg-day) IRs = Soil Ingestion Rate (mg/day) mg/kg = milligrams per kilogram

CDInc = Chronic Daily Intake for Non-Cancer Effects (mg/kg-day) N/A = not applicable mg/kg-day = milligrams per kilogram-day

CF = Conversion Factor (kg/mg) PCB = polychlorinated biphenyl

CR = Cancer Risk (unitless) RfD = Reference Dose (mg/kg-day)

CS = Chemical Concentration in Soil (mg/kg) SF = Slope Factor (mg/kg-day)-1

The exposure frequency (EF) was revised from 250 days/year to 30 days/year and the exposure duration (ED) was revised to 0.115 year based on meeting between United States Air Force and Illinois Environmental Protection Agency (IEPA) on January 17, 2024. The change in ED resulted in change of averaging time for non-carcinogenic effects (ATnc) to 42 days (7 days per week for 6 weeks). The ED value (0.115 years) was calculated (42 days divided by 365 days per year). These changes are based on the IEPA short-term construction worker scenario.

Final Remedial Investigation Addendum, Site UK510

TABLE 2-5

DERMAL EXPOSURE TO BACKGROUND CONCENTRATIONS OF CHEMICALS IN SEDIMENT

(FUTURE CONSTRUCTION/EXCAVATION WORKER - REASONABLE MAXIMUM EXPOSURE)

SITE UK510

SCOTT AIR FORCE BASE, ILLINOIS

Chemical CS SA AF ABS EF ED CF BW ATnc ATc CDInc Subchronic RfD HQ CDIc SF CR

(mg/kg) (cm2/event) (mg/cm2) (unitless) (days/year) (years) (kg/mg) (kg) (days) (days) (mg/kg-day) (mg/kg-day) (unitless) (mg/kg-day) (mg/kg-day)-1 (unitless)

PCBs

Aroclor 1248 1.00E-02 3,300 0.3 0.14 30 0.115 1E-06 80 42 25,550 1.42E-09 3.00E-05 0.000047 2.34E-12 2.00E+00 4.68E-12

Aroclor 1254 1.00E-02 3,300 0.3 0.14 30 0.115 1E-06 80 42 25,550 1.42E-09 3.00E-05 0.000047 2.34E-12 2.00E+00 4.68E-12

Aroclor 1260 1.00E-02 3,300 0.3 0.14 30 0.115 1E-06 80 42 25,550 1.42E-09 3.00E-05 0.000047 2.34E-12 2.00E+00 4.68E-12

Metals

Manganese 1.10E+03 3,300 0.3 N/A 30 0.115 1E-06 80 42 25,550 N/A N/A N/A N/A N/A N/A

TOTAL HAZARD INDEX = 0.0001 TOTAL CANCER RISK = 1.40E-11

Notes:

Background concentration (CS) is unsieved stream data (Short 1997).

Replaces Table E2-92 in Appendix E, Attachment E-2 of the Final Remedial Investigation/Feasibility Study (URS Group, Inc. 2022).

Equations:

CDI = (CS x SA x AF x ABS x EF x ED x CF)/(BW x ATnc or ATc)

HQ = CDI / RfD

CR = SF x CDI

Acronyms and Abbreviations: Units:

ABS = Percent Chemical Absorption Across Skin (unitless) CS = Chemical Concentration in Soil (mg/kg) cm2/event = square centimeters per event

AF = Soil Adherence to Skin (mg/cm2) ED = Exposure Duration (years) kg = kilograms

ATc = Averaging Time for Carcinogenic Effects, Based on Lifetime (days) EF = Exposure Frequency (days/year) kg/mg = kilograms per milligram

ATnc = Averaging Time for Non-carcinogenic Effects (days) HQ = Hazard Quotient (unitless) mg/cm2 = milligrams per square centimeter

BW = Body Weight (kg) N/A = not applicable mg/kg = milligrams per kilogram

CDIc = Chronic Daily Intake for Cancer Effects (mg/kg-day) PCB = polychlorinated biphenyl mg/kg-day = milligrams per kilogram-day

CDInc = Chronic Daily Intake for Non-Cancer Effects (mg/kg-day) RfD = Reference Dose (mg/kg-day)

CF = Conversion Factor (kg/mg) SA = Exposed Body Surface Area (cm2/event)

CR = Cancer Risk (unitless) SF = Slope Factor (mg/kg-day)-1

The exposure frequency (EF) was revised from 250 days/year to 30 days/year and the exposure duration (ED) was revised to 0.115 year based on meeting between United States Air Force and Illinois Environmental Protection Agency (IEPA) on January 17, 2024. The change in ED resulted in change of averaging time for non-carcinogenic effects (ATnc) to 42 days (7 days per week for 6 weeks). The ED value (0.115 years) was calculated (42 days divided by 365 days per year). These changes are based on the IEPA short-term construction worker scenario.

Final Remedial Investigation Addendum, Site UK510

TABLE 2-6

SUMMARY OF CANCER RISKS AND ADVERSE HEALTH

EFFECTS FOR THE FUTURE CONSTRUCTION/EXCAVATION WORKER

EXPOSED TO MAXIMUM DETECTED CONCENTRATIONS

SITE UK510

SCOTT AIR FORCE BASE, ILLINOIS

RME

CANCER

RISK

HAZARD

INDEX

SEDIMENTa

INGESTION 6.49E-08 0.2

DERMAL 2.57E-08 0.06

SEDIMENT TOTAL RISKS 9E-08 0.3

BACKGROUND SEDIMENTb

INGESTION 3.34E-11 0.02

DERMAL 1.40E-11 0.0001

BACKGROUND SEDIMENT TOTAL 5E-11 0.02

Notes:

Replaces Table E2-123 in Appendix E, Attachment E-2 of the Final Remedial Investigation/Feasibility Study (URS Group, Inc. 2022).

a Estimated risk values from Tables 2-2 and 2-3.

b Estimated background risk values from Tables 2-4 and 2-5.

Acronyms and Abbreviations:

RME = reasonable maximum exposure

Final Remedial Investigation Addendum, Site UK510

SECTIONTHREE Summary and Conclusions

Final Remedial Investigation Addendum, Site UK510 3-1 Scott AFB PBR

FA8903-14-C-0009

The following discussion presents a summary of the key findings and conclusions of this RI Addendum for UK510.

3.1 SUMMARY OF KEY FINDINGS

The BHRA was revised to update the future construction/excavation worker scenario to evaluate risk based on maximum detected concentrations in sediment and subsurface soil at UK510, and IEPA exposure parameters for a short-term construction worker. No unacceptable risk was identified for a future construction/excavation worker using the maximum detected concentrations and IEPA exposure parameters. Construction/excavation workers have no exposure to surface water.

3.2 CONCLUSIONS

The findings of the revised BHRA addressed in this RI Addendum and the Final UK510 RI/FS (URS 2022) resulted in the following conclusions:

• No unacceptable risk was identified for a future construction/excavation worker when the maximum detected concentrations were used as the EPCs and the IEPA exposure parameters for the short-term construction workers were incorporated.

• No unacceptable human health risks were identified for the future construction worker/ excavation worker using the 95UCL EPCs, exposure frequency of 250 days/year, and exposure duration of 1 year.

• No unacceptable human health risks were identified for the other receptor scenarios evaluated for UK510, to include the future hypothetical residential scenario. Risks to ecological receptors are negligible (URS 2022).

• Because no unacceptable human health or ecological risks were identified in the RI, further consideration of the “Identification and Screening of Technologies and Process Options” presented in the FS portion of the Final UK510 RI/FS (URS 2022) is no longer required with the following exception.

In the FS portion of the Final UK510 RI/FS (URS 2022), Section 10.9.3.1 stated “…there is a potential for future risk to human health due to the continual discharge from upgradient industrial areas via drainage ditches and storm water culverts that feed into UK510. These discharges have the potential to impact sediment, subsurface soil, and surface water quality at UK510. These risks would be mitigated by LUCs.”

This statement is amended as follows: “…there is continual discharge from upgradient industrial areas via drainage ditches and storm water culverts that feed into UK510. These discharges have the potential to impact sediment, subsurface soil, and surface water quality at UK510. Potential future risks would be mitigated by future compliance monitoring under the purview of the Scott AFB Environmental Compliance Office.” This revision has been discussed between the United States Air Force and IEPA in written correspondence and meetings as summarized in the IEPA February 6, 2025, correspondence in Appendix A (IEPA 2025).

3 Summary and Conclusions

SECTIONTHREE Summary and Conclusions

Final Remedial Investigation Addendum, Site UK510 3-2 Scott AFB PBR

FA8903-14-C-0009

• Upon concurrence of this RI Addendum, and in accordance with CERCLA, a Proposed Plan for No Further Action and subsequent Record of Decision will be prepared documenting Site Closure for UK510.

SECTIONFOUR References

Final Remedial Investigation Addendum, Site UK510 4-1 Scott AFB PBR

FA8903-14-C-0009

HydroGeoLogic, Inc. 2009. Final Risk Assessment Approach Technical Memorandum. Scott AFB, Illinois. June

Illinois Environmental Protection Agency. 2025. Letter to Mr. Joseph Weber. 6 February 2025.

Air Force Response to Illinois EPA (IEPA) Comments for Draft Final Remedial Investigation Addendum, Site UK510, July 2024, Scott Air Force Base (AFB), IL; Illinois EPA Comments dated 4 December 2024.

Short, M. B., 1997, “Evaluation of Illinois Unsieved Stream Sediment Data, 1982-1995,” IEPA/BOW/97-016, Illinois Environmental Protection Agency, August.

URS Group, Inc. (URS). 2019. Final UK510 Supplemental Remedial Investigation Work Plan, Uniform Federal Policy-Quality Assurance Project Plan. Scott Air Force Base. August.

URS. 2022. Final UK510 Remedial Investigation/Feasibility Study. Scott Air Force Base, Illinois. June.

United States Environmental Protection Agency (USEPA). 2002. Supplemental Guidance for Developing Soil Screening Levels for Superfund Sites (OSWER 9355.4-24).

USEPA. 2004. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part E Supplemental Guidance for Dermal Risk Assessment) Final (OSWER

9285.7-02EP).

USEPA. 2014. Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors (OSWER Directive 9200.1-120). Washington, D.C. February 6.

4 References

APPENDIXA Regulatory Correspondence

Final Remedial Investigation Addendum, Site UK510