HillAFB_OU_15_ZZ113_ROD_Draft_2NOV17.pdf

Hill Air Force Base, Utah

Draft

Operable Unit 15 – Site ZZ113 Record of Decision

NOVEMBER 2017

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1. REPORT DATE (DD-MM-YYYY)

02-11-2017

2. REPORT TYPE

Draft

3. DATES COVERED (From – To)

24 JAN 2017 – 2 NOV 2017

4. TITLE AND SUBTITLE

Operable Unit 15 – Site ZZ113 Record of Decision Hill Air Force Base, Utah

5a. CONTRACT NUMBER

FA8903-09-D-8560

5b. GRANT NUMBER

None 5c. PROGRAM ELEMENT NUMBER

None

6. AUTHOR(S)

EA Engineering, Science, and Technology, Inc., PBC 5d. PROJECT NUMBER

6263906 5e. TASK NUMBER

5f. WORK UNIT NUMBER None

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION

EA Engineering, Science, and Technology, Inc., PBC 2363 N. Hill Field Road, Suite 104 Layton, Utah 84041

REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S

ACRONYM(S)

Air Force Civil Engineer Center 2261 Hughes Avenue, Suite 163 JBSA Lackland Air Force Base, Texas 78236-9853

AFCEC

11. SPONSOR/MONITOR’S REPORT

NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

13. SUPPLEMENTARY NOTES

None

14. ABSTRACT

This Record of Decision presents the selected remedy for Operable Unit (OU) 15 – Site ZZ113 at Hill Air Force Base, Utah. OU 15 focuses on volatile organic compounds (VOCs), primarily chlorinated VOCs, with the potential to volatilize from contaminated groundwater and/or soil and migrate through the vadose zone or preferential pathways (e.g., sewers/drains) into overlying structures, potentially exposing occupants to VOC contamination via the vapor intrusion (VI) pathway. OU 15 addresses off- and on-Base areas or sites with existing subsurface VOC sources, managed under Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, where VI has the potential to occur. The U.S. Air Force evaluated remedial alternatives and selected institutional controls, monitoring, and mitigation as the preferred remedy for mitigating VI in off- and on-Base indoor air.

15. SUBJECT TERMS

Record of Decision, VOC, vapor intrusion, monitoring, mitigation, and Risk-Based Action Levels

16. SECURITY CLASSIFICATION OF: 17. LIMITATION

OF ABSTRACT

18. NUMBER

OF PAGES

19a. NAME OF RESPONSIBLE

PERSON

Sandra Staigerwald

a. REPORT

UNCLASSIFIED

b. ABSTRACT

UNCLASSIFIED

c. THIS PAGE

UNCLASSIFIED

SAR 112 19b. TELEPHONE NUMBER (include area code)

(385) 393-4982

Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18

F I N A L

Hill Air Force Base, Utah

Performance-Based Remediation

Operable Unit 15 Site ZZ113

Record of Decision

Contract No: FA8903-09-D-8560 Task Order 0006

Prepared for:

Air Force Civil Engineer Center 2261 Hughes Avenue, Suite 163

JBSA Lackland Air Force Base, Texas 78326-9853

Prepared by:

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

2363 N. Hill Field Road, Suite 104 Layton, Utah 84041

NOVEMBER 2017

OPERABLE UNIT 15 – SITE ZZ113 RECORD OF DECISION Draft

HILL AIR FORCE BASE, UTAH NOVEMBER 2017

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Contents Page

Tables ........................................................................................................................................................... iii Figure ........................................................................................................................................................... iii Exhibits ........................................................................................................................................................ iii Appendixes .................................................................................................................................................. iii Acronyms and Abbreviations ....................................................................................................................... v

1.0 Declaration .................................................................................................................................... 1-1

1.1 Site Name and Location ................................................................................................... 1-1

1.2 Statement of Basis and Purpose ....................................................................................... 1-1

1.3 Assessment of Site ........................................................................................................... 1-1

1.4 Description of Selected Remedy ...................................................................................... 1-1

1.5 Statutory Determinations ................................................................................................. 1-2

1.6 Data Certification Checklist ............................................................................................. 1-3

1.7 Authorizing Signatures and Support Agency Acceptance of Remedy ............................ 1-5

2.0 Operable Unit 15 Background and History ................................................................................... 2-1

2.1 Historical Indoor Air Sampling and Time-Critical Removal Action ............................... 2-1

2.1.1 Indoor Air Notification and Community Outreach ............................................. 2-1

2.1.2 Summary of Historical Indoor Air Program Results .......................................... 2-3

2.1.3 Current Status of the Indoor Air Program ........................................................... 2-4

2.2 Operable Unit 15 Creation ............................................................................................... 2-4

3.0 The Decision Summary................................................................................................................. 3-1

3.1 Site Name, Location, and Brief Description .................................................................... 3-1

3.2 Site History and Enforcement Activities ......................................................................... 3-1

3.2.1 Federal Facility Agreement ................................................................................ 3-2

3.3 Community Participation ................................................................................................. 3-2

3.4 Scope and Role of Operable Unit or Response Action .................................................... 3-3

3.5 Conceptual Site Model and Site Characteristics .............................................................. 3-4

3.5.1 General Vapor Intrusion Conceptual Site Model ................................................ 3-4

3.5.2 Hill Air Force Base-Specific Vapor Intrusion Conceptual Site Model............... 3-4

3.5.3 Operable Unit-Specific Data Evaluation – Off-Base .......................................... 3-9

3.5.4 Operable Unit-Specific Data Evaluation – On-Base......................................... 3-10

3.5.5 Remedial Action Target Areas ......................................................................... 3-11

3.5.6 Chemicals of Concern ....................................................................................... 3-12

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Page

3.6 Current and Potential Future Site and Resource Uses ................................................... 3-12

3.6.1 Off-Base Land Use ........................................................................................... 3-12

3.6.2 On-Base Land Use ............................................................................................ 3-13

3.6.3 Land Use Controls ............................................................................................ 3-13

3.7 Summary of Site Risks .................................................................................................. 3-14

3.7.1 Off-Base Baseline Risk Assessment ................................................................. 3-15

3.7.2 On-Base Baseline Risk Assessment.................................................................. 3-16

3.7.3 Basis for Response Action ................................................................................ 3-16

3.8 Remedial Action Objectives .......................................................................................... 3-16

3.9 Description of Alternatives ............................................................................................ 3-17

3.9.1 Description ........................................................................................................ 3-17

3.9.2 Common Elements, Distinguishing Features, and Expected

Outcomes of Each Alternative .......................................................................... 3-18

3.10 Comparative Analysis of Alternatives ........................................................................... 3-19

3.10.1 Overall Protection of Human Health and the Environment .............................. 3-19

3.10.2 Compliance with Applicable or Relevant and Appropriate Requirements ....... 3-20

3.10.3 Long-Term Effectiveness and Permanence ...................................................... 3-20

3.10.4 Reduction of Toxicity, Mobility, or Volume through Treatment ..................... 3-20

3.10.5 Short-Term Effectiveness ................................................................................. 3-20

3.10.6 Implementability ............................................................................................... 3-21

3.10.7 Cost ................................................................................................................... 3-21

3.10.8 State/Support Agency Acceptance .................................................................... 3-22

3.10.9 Community Acceptance .................................................................................... 3-22

3.11 Principal Threat Wastes ................................................................................................. 3-22

3.12 Selected Remedy ............................................................................................................ 3-22

3.12.1 Summary of the Rationale for the Selected Remedy ........................................ 3-23

3.12.2 Description of the Selected Remedy ................................................................. 3-23

3.12.3 Summary of Estimated Remedy Costs ............................................................. 3-25

3.12.4 Expected Outcomes of Selected Remedy ......................................................... 3-25

3.13 Statutory Determinations ............................................................................................... 3-25

3.13.1 Protection of Human Health and the Environment ........................................... 3-26

3.13.2 Compliance with ARARs ................................................................................. 3-26

3.13.3 Cost Effectiveness ............................................................................................. 3-27

3.13.4 Utilization of Permanent Solutions and Alternative Treatment Technologies . 3-27

3.13.5 Preference for Treatment as a Principal Element.............................................. 3-27

3.13.6 Five-Year Review Requirements ...................................................................... 3-27

3.14 Documentation of Significant Changes ......................................................................... 3-28

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Page

4.0 Responsiveness Summary ............................................................................................................. 4-1

5.0 References ..................................................................................................................................... 5-1

Tables

2-1 Hill Air Force Base Indoor Air Program Summary Statistics 3-1 Summary of On-Base High-Priority Buildings 3-2 Chemicals of Concern and Chemicals of Potential Concern 3-3 Other Operable Unit Record of Decision Documents 3-4 Summary of Carcinogenic Risk and Non-Cancer Hazard Estimates; Off-Base 3-5 Summary of Carcinogenic Risk and Non-Cancer Hazard Estimates; On-Base 3-6 Indoor Air Action Levels 3-7 Distinguishing Features of Remedial Alternatives 3-8 Comparative Analysis of Alternatives 3-9 Summary of Applicable or Relevant and Appropriate Requirements for Selected Remedy 3-10 Selected Remedy – Present Worth Cost Estimate 3-11 Selected Remedy – Retained Technologies

Figure

2-1 Boundaries of Land Use Controls

Exhibits

2-1 Summary of Indoor Air Sampling Results 2-2 Current Affected Areas 3-1 Key Vapor Intrusion Concepts

Appendixes

A Information Related to Indoor Air Program History B Information Related to Public Comment Period

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Acronyms and Abbreviations µg/L Microgram(s) per liter

AFB Air Force Base AFCEC Air Force Civil Engineer Center ARAR Applicable or Relevant and Appropriate Requirement

BASAP Basewide Air Sampling and Analysis Plan BRA Baseline Risk Assessment

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CERCLIS Comprehensive Environmental Response, Compensation, and Liability Information System CFR Code of Federal Regulations COC Chemical of concern COPC Chemical of potential concern

DCA Dichloroethane DCE Dichloroethene DCB Dichlorobenzene

EA EA Engineering, Science, and Technology, Inc. (prior to 12 December 2014) or EA Engineering, Science, and Technology, Inc., PBC (12 December 2014 and thereafter)

ELCR Excess lifetime cancer risk EPA U.S. Environmental Protection Agency ESD Explanation of Significant Differences

F Future worth FFA Federal Facility Agreement FS Feasibility study ft2 Square feet (square foot)

GAC Granular activated carbon

HI Hazard index HQ Hazard quotient HVAC Heating, ventilation, and air conditioning

IAP Indoor Air Program IC Institutional control ID Identification IRP Installation Restoration Program

JBSA Joint Base San Antonio

LUC Land use control

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NA Not applicable NCOA National Change of Address NCP National Oil and Hazardous Substances Pollution Contingency Plan

O&M Operation and maintenance OU Operable Unit

P Present worth PCE Tetrachloroethene POTW Publicly owned treatment works ppbv Part(s) per billion by volume

RAO Remedial action objective RBAL Risk-Based Action Level RCRA Resource Conservation and Recovery Act RD/RAWP Remedial Design/Remedial Action Work Plan RI Remedial investigation ROD Record of Decision

SAR Same as Report SARA Superfund Amendments and Reauthorization Act SMD Submembrane depressurization SSD Subslab depressurization

TCA Trichloroethane TCE Trichloroethene TCRA Time-Critical Removal Action TMV Toxicity, mobility, or volume

UAC Utah Administrative Code UDEQ Utah Department of Environmental Quality USAF U.S. Air Force USC United States Code UU/UE Unlimited use/unrestricted exposure

VC Vinyl chloride VI Vapor intrusion VIMS Vapor intrusion mitigation system VOC Volatile organic compound VRS Vapor removal system

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1.0 Declaration

1.1 Site Name and Location

Facility Name: Hill Air Force Base Site Location: Davis and Weber Counties, Utah CERCLIS ID Number: UT0571724350 Operable Unit/Site: Operable Unit 15 – Site ZZ113

1.2 Statement of Basis and Purpose

This decision document or Record of Decision (ROD) presents the selected remedy for Operable Unit (OU) 15 at Hill Air Force Base (AFB), in Davis and Weber Counties, Utah. OU 15 is also identified as Site ZZ113 by the U.S. Air Force (USAF) Installation Restoration Program (IRP). The selected remedy was chosen in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986, and to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision is based on the Administrative Record file for this site.

The USAF is managing OU 15 in accordance with CERCLA as required by the Defense Environmental Restoration Program. Because Hill AFB is on the National Priorities List, and pursuant to CERCLA, the U.S. Environmental Protection Agency (EPA) Region 8, the Utah Department of Environmental Quality (UDEQ), and the USAF entered into a Federal Facility Agreement (FFA) in April 1991. The purpose of the agreement was to establish a framework and schedule for developing, implementing, and monitoring appropriate remedial actions to address contamination at Hill AFB. The IRP is responsible for ensuring that appropriate CERCLA response alternatives are developed and implemented as necessary to protect public health, welfare, and the environment.

This ROD is issued by the USAF, which is the lead agency for cleanup actions at Hill AFB, and by EPA Region 8, which is the lead regulatory agency for CERCLA response actions at Hill AFB. This document was compiled and evaluated by the Air Force Civil Engineer Center (AFCEC)/ Environmental Operations Midwest Region Branch. Under CERCLA §120(e)(4)(A) and the NCP, the USAF and EPA jointly select the remedy. The State of Utah concurs with the selected remedy.

1.3 Assessment of Site

The response action selected in this ROD is necessary to protect the public health or welfare from actual or threatened releases of hazardous substances, pollutants, or contaminants into the environment.

1.4 Description of Selected Remedy

Remedial alternatives for mitigating vapor intrusion (VI) in OU 15 were developed and evaluated as part of the Feasibility Study (FS) (EA Engineering, Science, and Technology, Inc., PBC [EA] 2017a). The following remedy for mitigating VI in OU 15 has been selected on the basis of this evaluation:

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Institutional Controls (ICs), Monitoring, and Mitigation – Under this remedy, ICs will consist of an annual mailing sent to owners and occupants of residences and commercial/industrial building owners by Certified Mail within areas with the potential for VI in order to solicit indoor air sampling participation.

Indoor air monitoring will be performed to assess if VI is complete and significant at occupied commercial/industrial buildings or residences (collectively referred to as “occupied buildings” hereafter).

In the context of OU 15, “complete” and “significant” are defined as follows:

• Complete means that volatile organic compounds (VOCs) detected in a building or residence came from soil or groundwater contaminated with VOCs that originated at Hill AFB.

• Significant means that detected indoor air concentrations were above the Risk-Based Action Levels (RBALs).

Mitigation will be undertaken for occupied buildings with indoor air concentrations (attributable to VI) that exceed RBALs to reduce those concentrations to below the RBALs. In regard to future structures, while no pre-emptive mitigation of new construction would occur under OU 15, indoor air monitoring and, if necessary, mitigation of new buildings could occur after they are constructed.

Because a variety of building types and site conditions exist at OU 15, no single VI mitigation technology can be effectively applied to all buildings with RBAL exceedances. Instead, the most appropriate technology or technologies among those retained in the FS will be implemented and maintained to break the VI pathway based on conditions specific to each building. Technologies retained in the FS include sealing or venting buildings, modifying building environmental system controls, drain removal/ modification, and dewatering. This remedy allows flexibility in selecting an appropriate mitigation technology(ies) for a specific building while controlling cost(s) to the extent practical. At buildings or residences where VI mitigation systems are installed, monitoring would occur to assess system performance. The USAF will work with EPA and UDEQ to determine the type and frequency of indoor air monitoring and when monitoring/mitigation would no longer be required. Those details would be provided in the Remedial Design/Remedial Action Work Plan (RD/RAWP) scheduled to be prepared and submitted to EPA and UDEQ within the 2017 calendar year.

1.5 Statutory Determinations

The selected remedy satisfies the applicable statutory requirements of CERCLA §121(b), which states that the remedy must: (1) be protective of human health and the environment, (2) comply with Applicable or Relevant and Appropriate Requirements (ARARs) (or justify a waiver), (3) be cost effective, and

(4) use long-term solutions and alternative treatment technologies to the maximum extent practicable.

Although most components of this remedy (e.g., sealing and venting) do not attain the statutory preference for treatment, the remedy would reduce the amount of vapors entering a structure, thus reducing or eliminating indoor air contamination.

Because the remedy will result in hazardous substances, pollutants, or contaminants remaining above levels that allow for unlimited use/unrestricted exposure (UU/UE), a statutory review will be conducted within 5 years after initiation of remedial action, and every 5 years following, to ensure that the remedy is, or will be, protective of human health and the environment. These Five-Year Reviews will continue until UU/UE conditions are attained.

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1.6 Data Certification Checklist

The following information is included in the decision summary section of this ROD:

• Chemicals of concern (COCs) (Sections 3.5.5 and 3.5.6)

• Current and reasonably anticipated future land use assumptions used in the Baseline Risk Assessment (BRA) and ROD (Sections 3.6.1 for off-Base and 3.6.2 for on-Base)

• Baseline risk represented by COCs (Section 3.7)

• Cleanup levels established for COCs and the basis for these levels (Section 3.8)

• Key factor(s) that led to selecting the remedy (i.e., description of how the selected remedy provides the best balance of tradeoffs with respect to the balancing and modifying criteria, highlighting criteria key to the decision) (Section 3.10)

• Estimated capital; annual operation and maintenance (O&M); and total present worth costs, discount rate, and the number of years over which the remedy cost estimates are projected (Sections 3.10.7 and 3.12.3).

• How source materials constituting principal threats are addressed (Section 3.11).

Typically, the potential groundwater use available at the site as a result of the selected remedy is included in a ROD. However, because the purpose of OU 15 response actions are to address the VI pathway separately from the ongoing remedies in the underlying source area and groundwater at the associated OUs, groundwater uses are not relevant to OU 15.

Additional information can be found in the Administrative Record file available both at AFCEC Environmental Restoration, 7290 Weiner Street, Building 383, Hill AFB, Utah 84056-5003, and online at the AFCEC Administrative Record, http://afcec.publicadmin-record.us.af.mil/.

http://afcec.publicadmin-record.us.af.mil/

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1.7 Authorizing Signatures and Support Agency Acceptance

of Remedy

The USAF and EPA jointly select the remedy. The State of Utah concurs with the selected remedy.

Authorizing and support agency signatures are included on the following pages.

U.S. ENVIRONMENTAL PROTECTION AGENCY

Betsy Smidinger Assistant Regional Administrator Office of Ecosystems Protection and Remediation U.S. Environmental Protection Agency Region 8

Date

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STATE OF UTAH DEPARTMENT OF ENVIRONMENTAL QUALITY

Alan Matheson Executive Director State of Utah Department of Environmental Quality

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AIR FORCE CIVIL ENGINEER CENTER

Suzanne W. Bilbrey, P.E., GS-15 Director, Environmental Management Directorate Air Force Civil Engineer Center

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2.0 Operable Unit 15 Background and History

OU 15 focuses on VOCs, primarily chlorinated VOCs, with the potential to volatilize from contaminated groundwater and/or soil and migrate through the vadose zone or preferential pathways (e.g., sewers/ drains) into overlying structures, potentially exposing occupants to VOC contamination via the VI pathway. OU 15 addresses off- and on-Base areas or sites with existing subsurface VOC sources, managed under CERCLA, where VI has the potential to occur. This section presents a summary of the background and history of OU 15.

2.1 Historical Indoor Air Sampling and Time-Critical Removal

Action

Hill AFB has performed multiple phases of VI investigation in both on- and off-Base areas of OU 15.

Indoor air samples have been collected from off-Base residences since 1992 as part of OU- or site-specific RIs. Development of consistent data collection and sampling protocols for indoor air began in May 2000. Subsequently, Hill AFB initiated a Time-Critical Removal Action (TCRA) that included indoor air sampling and installation of VI mitigation systems (VIMSs) (also referred to as vapor removal systems [VRSs]) in residences with elevated indoor air concentrations of site-related VOCs (MWH 2003).

The first VIMSs were installed in residences in OU 12 between late 2002 and early 2003. To date, a total of 126 VIMSs have been installed. In 2003, Hill AFB established the Indoor Air Program (IAP), with the Basewide Air Sampling and Analysis Plan (BASAP), Indoor Residential Air Sampling (MWH 2004) as the primary governing document for IAP sampling and mitigation activities for the interim remedy established as part of the TCRA. The BASAP has been periodically revised since 2004, and is currently in its fourth iteration (EA 2016a).

2.1.1 Indoor Air Notification and Community Outreach

2.1.1.1 Indoor Air Program Annual Notifications

Owners and occupants of every building over and within a 100-foot boundary of the groundwater plumes originating from Hill AFB and within areas of suspected preferential vapor migration pathways (collectively known as the “Affected Areas”) have been contacted either by person, phone, or mailer (or combination) informing them of the potential for VI into indoor air and requesting entry for indoor air sampling. The vast majority of locations have been contacted multiple times—on an annual basis since 2004. Table 2-1 presents a summary of statistics for the notification process, including the number of locations contacted, locations sampled, those that declined sampling, and the number of non-responses for each year of the IAP.

The first year of the IAP (2003), 975 letters were mailed to off-Base residents. From 2004 through 2013, approximately 2,400 to 2,700 mailings were sent each year. Because the groundwater plume footprints or knowledge of potential preferential pathways changed from year to year, the number of homes in the Affected Areas varied on an annual basis. However, every year, every residence in the defined Affected Areas (regardless of previous sample results or whether a VIMSs had been installed) was sent a mailer packet or was contacted by phone, including residents who had declined sampling the previous year.

While residential locations were the focus of the mailers, schools, daycares, and commercial buildings were contacted via other means (e.g., phone) and sampled.

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Between 2003 and 2013, the procedure for the mailings was to obtain a mailing list of all residential addresses in the Affected Areas either by purchasing it from a mailing service or generating it from available geographic information system data. Every address on the annual list, including residents that refused in a previous year, was sent a mailer packet. The packet included a letter on USAF letterhead explaining the purpose of the mailing, an invitation to participate in the IAP, information about the program, and a postage-paid return postcard. Beginning in 2007, instructions to receive program information in Spanish were included in the mailers. If Hill AFB had not received the return postcard after 6 weeks, a reminder postcard was sent to those who had not responded.

No mailings were sent in 2014 through 2016. Instead, phone calls were made to residents and businesses that participated in the program in previous years. A minimum of three attempts were made to directly contact those residents and businesses. In 2016, an advertisement was run in the local newspaper (the Standard-Examiner), soliciting participation in the IAP. As a result of the advertisement, separate stories about the IAP were run by the newspaper and a local television news channel (Fox 13 News).

In 2017, the USAF sent mailers to the owners and occupants of residences and commercial buildings within the Affected Areas. Beyond sending mailers to the physical locations within the Affected Areas, mailers were also sent to landlords and property owners. Beginning in 2017, mailings were sent using Certified Mail and Signature Confirmation (via U.S. Postal Service) to verify that mailers have been delivered and received. If there is no response to the mailer or follow up notices of its availability by the post office, it will be assumed that the owner/occupant has declined air sample collection for the sampling season. Locations with VIMS (126) did not receive letters and will be contacted directly by phone for VIMS inspection and performance sampling. In addition, locations in the current Affected Areas where previous sampling/investigation has confirmed that VI is not occurring (341) did not receive letters.

2.1.1.2 Communication Tracking

Every address within the Affected Areas (current and historical) is maintained in a database housed at Hill AFB. Every contact (whether via phone, in-person, or mail) made to the occupant or owner of each address is documented in the database. The database contains all communications, including letters, phone calls made and received, conversations, postcards, newsletters, and InfoFair invitations. Every address within the Affected Areas can be queried to determine what type and frequency of contact was made, and whether there was a response to the outreach. The database also tracks refusals to allow sampling, follow-up investigations, and installation of VIMSs, as well as non-responses to outreach.

Documentation of Certified Mail delivery and Signature Confirmation received (including scanned images of tracking receipts) are also included in the database. Since the beginning of the IAP, more than 200,000 communications with more than 9,000 individuals have been tracked in the database.

2.1.1.3 Community Outreach

Restoration Advisory Board Meetings. The USAF generally meets quarterly with members of the Hill AFB Restoration Advisory Board, which consists of approximately 25 people representing the local communities; federal, state, county, and city governments; local sewer and water districts; civic, business, and environmental groups; the USAF; and other interested parties. Restoration Advisory Board meetings are advertised in local newspapers and open to the public. From February 1995 through April 2017, a total of 42 presentations with updates regarding Hill AFB indoor air sampling activities have been delivered at Restoration Advisory Board meetings. A summary of the dates and topics for these presentations is provided in Table A-1 in Appendix A.

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InfoFairs. Hill AFB officials regularly host InfoFairs, or informational meetings, with community stakeholders. These meetings are open to the public and used as a forum to communicate with the public on a variety of Base-related topics, including environmental cleanup. From April 2004 through June 2017, a total of 14 InfoFairs were hosted in various cities around the Base specifically to provide updates regarding the Hill AFB IAP and indoor air sampling results. A summary of the dates, cities, topics, meeting locations, and number of people in attendance is provided in Table A-2 in Appendix A.

Direct Coordination with Affected Communities. The USAF has presented at city council meetings, provided city leaders with regular updates on changes to areas in their communities with a potential for VI, and worked directly with cities to notify residents of the sampling program in their city newsletters.

In turn, cities have used the information provided by the USAF for their planning purposes. City council updates usually occurred annually, or when the city would request them.

OU 15 Website. The USAF maintains a website with information about OU 15 (http://www.hill.af.mil/IAP/), including notice of upcoming sampling events, up-to-date maps showing areas with the potential for VI, and contact information to inquire about indoor air sampling. Notice of the availability of this website is included in the annual mailers and city newsletters.

2.1.2 Summary of Historical Indoor Air Program Results

Through the 2016 sampling year, 9,827 indoor air samples have been collected from 2,030 off-Base locations as part of the IAP. Of the 2,030 locations that have been sampled, 1,221 locations are within the current Affected Areas and 809 are outside the current Affected Areas. Each of the off-Base groundwater plumes with the potential to create VI is stable or shrinking (Section 3.5.2.1). The Affected Areas have generally decreased in size over time as the groundwater plumes associated with other Hill AFB OUs have been remediated. As a result, VIMSs were installed in some buildings that are no longer located within the current Affected Areas. A summary of these locations is presented in Exhibit 2-1. Indoor air sampling at these locations will be discontinued and VIMSs will be decommissioned or ownership transferred to property owners/occupants. The remainder of this discussion will be focused on locations within the current Affected Areas.

Of the 1,221 locations within the current Affected Areas that have been sampled, 145 exhibited COC concentrations in exceedance of the RBAL potentially attributed to VI into indoor air (compound-specific RBALs and their derivation are discussed in Section 3.8). VIMSs were installed in 88 of the 145 locations with potentially VI-related detections of COCs exceeding the RBAL; VIMSs have not been installed in 57 of these locations. Of the 1,076 locations that did not have a RBAL exceedance, VIMSs were installed in 27 of these locations; VIMSs were not installed in the remaining 1,049 locations (Exhibit 2-1).

Fifty-seven of the 145 residences that have had detections greater than the RBAL do not have a VIMS and a background indoor source (e.g., a household spray degreaser) has not been positively confirmed (note that an indoor source is still a possibility). Thirty-two of those 57 locations have since been sampled and have not had another detection greater than the RBAL (note that, at some of these locations, the USAF offered a VIMS after the initial RBAL exceedance but the resident refused the VIMS in favor of additional sampling). Of the remaining 25 locations, 5 refused the USAF’s recommendation/ offer to install a VIMS. The remaining 20 did not respond to multiple communications made by the USAF. Each of those 20 residences were contacted a minimum of 3 times to attempt to schedule a follow-up investigation or VIMS installation; Table A-3 in Appendix A summarizes the number of contacts that were made to each of these 57 residences.

http://www.hill.af.mil/IAP/

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2.1.3 Current Status of the Indoor Air Program

Of the 2,246 locations currently within the Affected Areas, 1,221 have been sampled. Of the 1,221 locations that have been sampled, sample results indicated VI was not occurring at 341 locations.

Potential VI was occurring at 145 locations, and a VIMS was installed in 88 of those locations. The remaining 735 locations were sampled in the past but additional sampling necessary for a definitive evaluation has not been accepted by the building owners/occupants. Of the 1,025 locations in the current Affected Areas that have not been sampled, 866 were contacted annually from 2003-2013 and in 2017.

The remaining 159 locations include 35 newly constructed residences and 124 commercial properties added to the program and contacted for the first time in 2017. Exhibit 2-2 presents a summary of the number of locations within the current Affected Areas, number of locations sampled, new notifications in 2017, and locations that have not been sampled.

2.2 Operable Unit 15 Creation

In March 2013, OU 15 was created to evaluate VI at on- and off-Base portions of existing Hill AFB OUs 1, 2, 4, 5, 6, 8, 9, 10, and 12. The five OUs not included in OU 15 either: (1) do not have VOC contamination (OUs 13 and 14); (2) have contamination associated with or evaluated as part of another OU (groundwater plumes in OUs 3 and 7 are part of OU 8); or (3) VI investigations have been completed during the OU-specific RI/FS process and no further evaluation of future VI pathways was required (OU 11 [Hill AFB 2015a]).

The RI and associated BRA did not identify significant VI occurring in the off-Base portions of OUs 4, 9, and 10. The term “significant” in this context refers to the potential for VI-related exposures that correspond to excess lifetime cancer risks (ELCRs) above 1 × 10-5, hazard indexes (HIs) above 1, or both (refer to Section 3.7 for more information). The RBALs are based on this risk level. Therefore, the FS and remedy evaluation focused on off-Base structures located within the six OUs identified with the potential for significant VI (OUs 1, 2, 5, 6, 8, and 12).

On Base, the RI and BRA did not identify OUs where significant VI was occurring based on evaluation of current buildings. However, due to uncertainties in results of the investigation performed at Building 265, further monitoring of trichloroethene (TCE) in indoor air is warranted at Building 265 to determine whether mitigation is necessary. It is also possible that the use of existing buildings in areas with the potential for VI could change, or buildings could be constructed in the future in areas with the potential to create VI. Because such buildings may have different characteristics and could be located in areas with elevated VOCs in soil gas, a VI evaluation and, if necessary, mitigation could be required after buildings are constructed in these areas.

Based on the conclusions of an OU 9 site-specific risk assessment presented in the OU 9 ROD (Hill AFB 2015b), there are no unacceptable VI risks on-Base associated with OU 9. It is possible that future VI evaluation may occur for future construction in on-Base portions of OUs 1, 2, 4, 5, 6, 8, 10, and 12, although ICs have been established in those OUs to restrict potential future construction in areas with the potential to cause VI. Figure 2-1 shows the on- and off-Base areas with the potential for VI. These areas are within approximately 100 feet of the VOC soil and groundwater contamination associated with OUs 1, 2, 4, 5, 6, 8, 10, and 12, combined with areas containing known or suspected preferential vapor pathways.

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EXHIBIT 2-1

Summary of Indoor Air Sampling Results Operable Unit 15 – Site ZZ113 Record of Decision, Hill Air Force Base, Utah

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EXHIBIT 2-2

Current Affected Areas

TABLE 2-1

Hill Air Force Base Indoor Air Program Summary Statistics Operable Unit 15 – Site ZZ113 Record of Decision, Hill Air Force Base, Utah

Year(1)

Total Locations

Contacted(2)

Total Locations Sampled

Declined Sampling(3)

No Response Notes

2003 975 405 45 525 Certified mailing to 863 new addresses, with the remainder sent first-class mail because they had been notified the previous year.

2004 2,404 749 122 1,533 First-class mailing sent to every residential address in the defined sampling area.

2005 2,583 552 100 1,931 First-class mailing sent to every residential address in the defined sampling area.

2006 2,547 475 100 1,972 First-class mailing sent to every residential address in the defined sampling area.

2007 2,614 412 90 2,112 First-class mailing sent to every residential address in the defined sampling area.

2008 2,725 438 105 2,182 First-class mailing sent to every residential address in the defined sampling area.

2009 2,712 338 118 2,256 First-class mailing sent to every residential address in the defined sampling area.

2010 2,400 265 96 2,039 First-class mailing sent to every residential address in the defined sampling area.

2011 2,401 216 80 2,105 First-class mailing sent to every residential address in the defined sampling area.

2012 2,401 207 58 2,136 First-class mailing sent to every residential address in the defined sampling area.

2013 2,737 426 NA 2,311 First-class mailing sent to every residential address in the defined sampling area.

2014 394 374 NA 20 No mailing. Phone calls only to those sampled in the previous year and those on periodic sampling.

2015 452 261 NA 191 No mailing. Phone calls only to those sampled in the previous year and those on periodic sampling.

2016 158 141 5 12 No mailing. Newspaper ad published.

Newspaper story and local television news stories run. Phone calls to those sampled in the previous year and those on periodic sampling. No calls to locations where VI was confirmed to not be occurring.

2017 2,246 -- -- -- Certified mailing to every address in Affected Areas. Addresses with known names associated with them were sent mailings with Certified Mail and Signature Confirmation.

First time mailing to businesses (124).

Mailers were sent to 1,790 locations, including 1,666 residences (35 of which were newly constructed) and 124 businesses. An additional 558 mailers were sent to landlords/property owners who own rental properties (both business and residential) in the Affected Areas. Locations with VIMS

(126) did not receive letters and will be contacted directly by phone. In addition, locations in the current Affected Areas where VI was confirmed to not be occurring (341) did not receive letters.

TABLE 2-1

Hill Air Force Base Indoor Air Program Summary Statistics Operable Unit 15 – Site ZZ113 Record of Decision, Hill Air Force Base, Utah

Year(1)

Total Locations

Contacted(2)

Total Locations Sampled

Declined Sampling(3)

No Response Notes

NOTES:

(1) The year mailings were sent. Mailings have typically been sent in the fall prior to a winter sampling event. For example, the mailers sent in 2017 are for the sampling event that begins in October 2017 and continues through March 2018 (i.e., the 2017-2018 event).

(2) Includes locations that had been previously sampled and locations that had never been sampled.

(3) Includes locations that had been sampled previously and did not wish to be sampled again.

-- = Data not available at this time.

NA = Not applicable.

VI = Vapor intrusion.

VIMS = Vapor intrusion mitigation system.

§̈¦15

HILL AIR FORCE BASE

DAVIS COUNTY

WEBER COUNTY §̈¦84

LAYTON

RIVERDALE

CLINTON

SOUTH OGDEN

CLEARFIELD

SUNSET

SOUTH OGDEN

SOUTH OGDEN

ROY CITY

SOUTH

WEBER

SYRACUSE

OPERABLE

UNIT 12 OPERABLE

UNIT 6

OPERABLE

UNIT 4

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UNIT 2

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OPERABLE

UNIT 5

OPERABLE

UNIT 10

OPERABLE

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ANTELO PE DR

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LL

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SLC \\SLCDBP01\gis\pro j\HillAFB_2012\Ma pFiles\O U15\RO D_Z Z 113\Fig02-01_GIS_O U15_RO D_Ta rget.m xd m c o tterb 10/12/2017

HILL

AIR FORCE

BASE

MAP

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FIGURE 2-1

BOUNDARIES OF LAND USE CONTROLS

O PERABLE UNIT 15 – SITE Z Z 113 RECO RD O F DECISIO N

HILL AIR FO RCE BASE, UTAH

O pera b le Unit 15 - Ind o o r Air Pro gra m O pera b le Unit 15 c o nsists o f:

O ff-Ba se resid entia l a rea s o verlying gro und wa ter VO C plum es O n-Ba se ind ustria l a rea s o verlying gro und wa ter VO C plum es a nd kno wn o r po tentia l VO C so urc e a rea s Source(s):

– O U 1 c is-1,2-DCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells fro m 2011-2013.

– O U 2 TCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells fro m 2009-2011.

– O U 4 TCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells Spring 2014.

– O U 5 TCE c o nc entra tio ns m ea sured in gro und wa ter wells thro ugh 2013.

– O U 6 TCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells Spring 2013.

– O U 8 1,2-DCA c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells thro ugh 2013.

– O U 8 TCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells thro ugh 2014.

– O U 10 TCE a nd PCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells thro ugh 2015.

– O U 12 TCE c o nc entra tio ns m ea sured in gro und wa ter m o nito ring wells thro ugh 2014.

–Sha pes fo r Po tentia l VI So urc e Area - Va d o se Z o ne a re fro m Figure B-1 o f the Fina l Annua l Assessm ent Repo rt fo r La nd Use Co ntro ls Ca lend a r Y ea r 2015, d a ted August 2016 (Hill Air Fo rc e Ba se 2016).

Acronym(s) and Abbreviation(s):

DCA = Dic hlo ro etha ne DCE = Dic hlo ro ethene O U = O pera b le Unit PCE = Tetra c hlo ro ethene TCE = Tric hlo ro ethene VI = Va po r intrusio n VO C = Vo la tile o rga nic c o m po und Note(s):

Geo gra phic d a ta fo r the stud y a rea were pro jected using c o o rd ina te system Wo rld Geo d etic System 1984 Universa l Tra nsverse Merc a to r Z o ne 12N.

0 25 5012.5 Miles

0 3,000 6,000 Feet

1 inc h equa ls 3,000 feet

LEGEND

Co unty Bo und a ry Munic ipa l Bo und a ry Hill Air Fo rc e Ba se Bo und a ry VO C Gro und wa ter Plum e with Insignific a nt VI Risk Current Po tentia l VI So urc e Area - Va d o se Z o ne Current Po tentia l VI So urc e Area - Gro und wa ter

Eafp\departments\Federal\6236900 AFCEE WERC09\6236906 Hill AFB PBR 3-1

3.0 The Decision Summary

The decision summary identifies the selected remedy, explains how the remedy fulfills statutory and regulatory requirements, and provides a substantive summary of the Administrative Record file that supports the remedy selection decision.

3.1 Site Name, Location, and Brief Description

Hill AFB is located in northern Utah, approximately 30 miles north of Salt Lake City and approximately 7 miles south of Ogden (Figure 2-1). Hill AFB occupies approximately 6,700 acres within portions of Davis and Weber counties. The Base is bounded on the north by the Davis-Weber Canal, a privately owned irrigation canal and on the east by private property. Interstate 15 and State Route 193 form the western and southern boundaries of the Base, respectively.

Hill AFB has been the site of military activities since 1920, including distribution of military equipment, aircraft rehabilitation and maintenance, and missile assembly. A variety of ongoing industrial operations support the missions of Hill AFB, including metal plating, degreasing, paint stripping, painting, sanding, and other operations associated with aircraft, missile, and vehicle repair and maintenance. These industrial operations have generated numerous spent chemicals and wastes, including chlorinated and non-chlorinated solvents and degreasers, petroleum hydrocarbons, acids, bases, metals, and other chemicals.

Historical chemical handling practices resulted in soil (on-Base) and groundwater (on- and off-Base) becoming contaminated with VOCs. Beyond the Hill AFB boundaries, 8 of 14 OUs (OUs 1, 2, 4, 5, 6, 8, 10, and 12) have shallow groundwater contamination plumes that currently underlie residential areas within the off-Base communities of South Weber, Riverdale, Roy, Clinton, Sunset, Clearfield, and Layton, Utah (Figure 2-1). No groundwater plumes associated with OU 9 extend beneath off-Base residences. The potential for VI may exist where occupied buildings overlie or are near VOC-contaminated soil or groundwater, or where vapors can migrate from VOC-contaminated soil or groundwater to occupied buildings through preferential pathways like sewer and drain lines.

As the lead agency, the USAF has conducted environmental restoration at OU 15 in accordance with CERCLA under the Defense Environmental Restoration Program, which was established by Section 211 of SARA. EPA Region 8 is the lead regulatory agency for CERCLA response actions at Hill AFB;

UDEQ is a support agency providing regulatory oversight. The Hill AFB Comprehensive Environmental Response, Compensation, and Liability Information System (CERCLIS) Identification Number is UT0571724350 (EPA 2017). The USAF funds the response action.

3.2 Site History and Enforcement Activities

As far back as the 1970s, compliance with applicable environmental regulations has been a priority in the operation of Hill AFB. Since 1984, the USAF has committed significant resources to assess and remediate environmental contamination identified at Hill AFB. CERCLA established a national program for responding to releases of hazardous substances into the environment. In anticipation of CERCLA, the Department of Defense developed the IRP to respond to releases of toxic or hazardous substances at Department of Defense facilities.