E6-10105. National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Notice of intent for partial deletion of the Ellsworth Air Force Base Site from the National Priorities List.

SUMMARY:

The Environmental Protection Agency, Region 8 (EPA) announces its intent to delete portions of the Ellsworth Air Force Base (AFB) Site located in Meade and Pennington Counties, South Dakota, from the National Priorities List (NPL) and requests public comment on this action. The NPL constitutes Appendix B to the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 CFR Part 300, which EPA promulgated pursuant to Section 105 of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).

The EPA has determined, with the concurrence of the State of South Dakota through the Department of Environment and Natural Resources (SDDENR) that for the parcels proposed for deletion, all appropriate actions under CERCLA have been implemented to protect human health, welfare and the environment and no further response action by responsible parties is appropriate. This partial deletion pertains to surface soil, unsaturated subsurface soil, surface water, and sediments at Operable Units 2, 3, 4, 5, 6, 7, 8, 9, 10 and 12, and excludes the ground water medium at these parcels. The ground water medium at the Ellsworth AFB Site (OU-11, Basewide Ground Water), and the soil medium (surface and unsaturated subsurface soils) at OU-1, Fire Protection Training Area, will remain on the NPL and response activities will continue for those OUs. Two additional areas not associated with an operable unit, the Gateway Lake Ash Study Area and the Pride Hangar Study Area, are currently under investigation and are also not part of this partial deletion.

DATES:

Comments concerning this proposed partial deletion may be submitted on or before July 28, 2006.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-HQ-SFUND-1990-0011, by one of the following methods:

• http://www.regulations.gov: Follow the on-line instructions for submitting comments.
• E-mail: [e-mail].
• Fax: [phone].
• Mail: Mr. John Dalton, Community Involvement Coordinator (8OC), U.S. EPA, Region 8, 999 18th Street, Suite 300, Denver, CO 80202-2466.
• Hand Delivery: 999 18th Street, Suite 300, Denver, CO 80202-2466.

Instructions: Direct your comments to Docket ID No. EPA-HQ-SFUND-1990-0011. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at http://www.regulations.gov,, including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through http://www.regulations.gov,, your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses.

Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in http://www.regulations.gov or in hard copy at the EAFB Information Repository located at the Rapid City Public Library and at the Ellsworth AFB Holbrook Library. The Rapid City Library is located at 610 Quincy Street, Rapid City, SD 57701. For hours of operation, call [phone]. Holbrook Library is located at 2650 Doolittle Dr. Ellsworth AFB, SD 57706, between the Base commissary and the Base Theater. For hours of operation, call [phone].

All CERCLA and Environmental Restoration Program (ERP) documents, including those not kept at the Information Repositories, and the Docket for this proposed partial deletion are kept in the Administrative Record. The Administrative Record is available for public viewing at the Base Environmental Management Flight, 2103 Scott Drive, Ellsworth AFB, SD 57706. To schedule an appointment or for Base access call [phone].

FOR FURTHER INFORMATION CONTACT:

Mr. John Dalton, Community Involvement Coordinator (8OC), U.S. EPA, Region 8, 999 18th Street, Suite 300, Denver, CO 80202-2466, Phone: [phone].

Table of Contents

I. Introduction

II. NPL Deletion Criteria

III. Deletion Procedures

IV. Basis for Intended Partial Site Deletion

V. Deletion Action

I. Introduction

The EPA announces its intent to delete portions of the Ellsworth AFB Site (CERCLIS ID #SD2571924644), from the NPL and requests comments on this proposed action. The NPL constitutes Appendix B to the NCP, 40 CFR part 300, which EPA promulgated pursuant to Section 105 of CERCLA as amended, 42 U.S.C. 9605. The NPL is a list of facilities which EPA determined may pose a significant threat to public health, welfare, or the environment. 40 CFR 300.425(e) authorizes deletion of facilities, or portions of facilities, from the NPL provided that facility meets certain criteria. Deletion from the NPL does not necessarily preclude further remedial action. If a significant release occurs at a facility deleted from the NPL, that facility is restored to the NPL without application of the Hazard Ranking System. Federal facilities are not eligible for Superfund-financed remedial action. However, all Federal facilities, whether listed on the NPL or not, have a continuing statutory duty to conduct further remediation, if required, even after the Federal property is transferred to non-Federal owners. When a release attributable to a Federal facility's historical activities is discovered after a property transfer, CERCLA section 120(b)(3)(A)(i) requires the federal entity to conduct further remediation if necessary for the protection of human health and the environment.

An environmental assessment was conducted at Ellsworth AFB on the parcels proposed for deletion. All media were sampled. Results of the sampling were reported in Remedial Investigation (RI) reports which were used to conduct Risk Assessments. Feasibility Studies (FS) were generated which evaluated potential remedies required to address the contamination. The remedies were summarized in a public notice soliciting comments on the remedies. All public comments received during the public comment periods were considered by the Air Force and EPA before the final remedy was selected.

The parcels proposed for deletion are described in more detail later in this document. EPA proposes deleting these parcels from the NPL because no further CERCLA response is appropriate. The remaining portions of the property comprising the Ellsworth AFB Site will remain on the NPL. This notice will be published in the Federal Register to solicit public comments on the proposed partial deletion. The public comment period is thirty (30) days beginning on the date of publication.

Section II of this action explains the criteria for the partial deletion of sites from the NPL. Section III discusses the procedures that EPA is using for this action. Section IV discusses the history of the Ellsworth AFB Site and explains how the portions of the Site proposed for deletion meet deletion criteria. Section V states EPA's intention to delete the portions of the Site from the NPL unless dissenting comments are received during the comment period.

II. NPL Deletion Criteria

The NCP establishes the criteria that are used to delete sites from the NPL. In accordance with 40 CFR 300.425(e), sites may be deleted from the NPL where no further response is appropriate to protect human health or the environment. In making such a determination pursuant to 40 CFR 300.425(e), EPA will consider, in consultation with the State, whether any of the following have been met:

(1) Section 300.425(e)(1)(i). Responsible parties or other persons have implemented all appropriate response actions required; or

(2) Section 300.425(e)(1)(ii). All appropriate Fund-financed response under CERCLA has been implemented, and no further response action by responsible parties is appropriate; or

(3) Section 300.425(e)(1)(iii). The remedial investigation has shown that the release poses no significant threat to human health or the environment and, therefore, taking of remedial measures is not appropriate.

As explained below, portions of the Ellsworth AFB Site meet the NCP's deletion criteria listed above. Therefore, partial deletion is being proposed.

III. Deletion Procedures

Upon determination that at least one of the criteria described in 40 CFR 300.425(e) of the NCP has been met, EPA may formally begin deletion procedures. The following procedures were used for the proposed partial deletion of portions of Ellsworth AFB:

(1) All appropriate responses under CERCLA have been implemented and no further action is appropriate for the identified areas;

(2) The State of South Dakota through the Department of Environment and Natural Resources concurred with this proposed partial deletion decision via a letter dated February 10, 2006;

(3) Concurrent with this Notice of Intent for Partial Deletion, notice has been published in the Rapid City Journal (the newspaper of record) and has been distributed to appropriate Federal, State, and local officials, and other interested parties. These notices announce a thirty (30) day public comment period on the deletion package, which commences on the date of publication of this notice in the Federal Register and the Rapid City Journal; and

(4) All relevant documents have been made available for public review at the local information repositories listed previously.

Upon completion of the 30-day comment period, EPA will evaluate all comments received before issuing the final decision on partial deletion. If appropriate, EPA will prepare and issue a Responsiveness Summary for comments received during the public comment period and will address concerns presented in the comments. The Responsiveness Summary will be made available to the public at the information repositories. Members of the public are encouraged to contact EPA to obtain a copy of the Responsiveness Summary. If, after review of all public comments, EPA determines that the partial deletion from the NPL is appropriate, EPA will publish a Final Notice of Partial Deletion in the Federal Register. As stated in 40 CFR 300.425, a site, or portion of a site, deleted from the NPL, remains eligible for future response actions if conditions warrant.

IV. Basis for Intended Partial Site Deletion

The following site summary provides EPA's rationale for the proposed partial deletion. It also includes information demonstrating satisfaction of the deletion criteria specified under 40 CFR 300.425(e).

Background

Ellsworth AFB is a U.S. Air Force Air Combat Command (ACC) installation located 12 miles east of Rapid City, South Dakota, and adjacent to the small community of Box Elder. The main Air Base covers approximately 4,858 acres within Meade and Pennington counties and includes runways, airfield operations, industrial areas, housing, and recreational facilities. The site was officially activated in July 1942 as the Rapid City Army Air Base, a training facility for B-17 bomber crews. Ellsworth AFB has been the headquarters of operations for a variety of aircraft, the Titan I Intercontinental Ballistic Missile system and the Minuteman I and Minuteman II Missile systems. The Base has historically provided support, fueling, training, maintenance, and/or testing facilities. Operations at Ellsworth AFB over the years generated a variety of waste materials including municipal solid waste, wastewater treatment plant sludge, industrial wastes including waste oils, solvents, paints, spilled fuels, waste pesticides, shop waste, metal remains from ordnance disposal (shell casings and bomb fragments but not unexploded ordnance) and radiological wastes. Contaminants of concern at Ellsworth AFB include chlorinated solvents, waste fuels and metals.

Ellsworth AFB is located within the following Sections, Townships, and Ranges, in Pennington and Meade Counties, South Dakota:

Sections 35 and 36, Township 3 North, Range 8 East, Meade County;

Section 31, Township 3 North, Range 9 East, Meade County;

Sections 1, 2, 11, 12, 13, Township 2 North, Range 8 East, Pennington and Meade Counties; and

Sections 5, 6, 7, 8, 17, 18, 19, Township 2 North, Range 9 East, Pennington and Meade Counties.

Ellsworth AFB was placed on the NPL August 30, 1990 (55 FR 35509) and is therefore subject to the provisions of Section 120 of CERCLA, 42 U.S.C. 9620. At that time the entire base, approximately 4,858 acres, was included in the listing (“fence line to fence line”). The Department of Defense, EPA and the State of South Dakota entered into a Federal Facilities Agreement (FFA) which formalizes the process for environmental response actions and the relative roles of the Air Force, the EPA and the State of South Dakota under CERCLA and the Installation Restoration Program (IRP). The FFA was signed by the Air Force, the EPA, and the State of South Dakota in January, 1992 and became effective on April 1, 1992.

Upon listing, the facility began identifying sites where activities involving hazardous substances may have occurred. The sites requiring further investigations were grouped into Operable Units (OUs). Twelve OUs have been identified at Ellsworth AFB. The OUs include: OU-1, Fire Protection Training Area; OU-2, Landfills Nos. 1 and 6; OU-3, Landfill No. 2; OU-4, Landfill No. 3; OU-5, Landfill No. 4; OU-6, Landfill No. 5; OU-7, Weapons Storage Area; OU-8, Explosive Ordnance Disposal Area; OU-9, Old Auto Hobby Shop Area; OU-10, North Hangar Complex; OU-11, Basewide Ground Water; and OU-12, Hardfill No. 1. Records of Decision (RODs) have been finalized for all of these OUs. Appropriate response actions for soil media have been completed per ROD decisions at the 10 OUs proposed for deletion. The RI/FS process did not identify any unacceptable risks for surface water and sediment at these OUs. Therefore, remedial actions were not required for surface water and sediment. Remedial activities for areas where there has been a release or disposal of petroleum products have been deferred to action under the SDDENR petroleum release program.

The portions of the Ellsworth AFB Site to be deleted from the NPL include surface soil, unsaturated subsurface soil, surface water and sediment media at OU-2, OU-3, OU-4, OU-5, OU-6, OU-7, OU-8, OU-9, OU-10 and OU-12 (approximately 542 acres) and the surface soil, unsaturated subsurface soil, surface water and sediment media of an additional 4,300 acres which are not associated with an operable unit and are not identified as posing a risk to human health or the environment.

Of the approximately 4,858 acres originally included in the Ellsworth AFB site NPL listing in 1990, there are four areas that are not being deleted. These areas are:

• OU-1 (all media) [generally described by the following coordinates: N667749.88/E1242611.11; N667496.84/E1242812.29; N667330.75/E1242852.01; N666933.49/E1242558.40; N667158.53/E1242265.75; N667787.47/E1242276.80; N667749.88/E1242611.11]
• OU-11 (Basewide Ground Water) [including all ground water plumes located within the Base boundary (described earlier) and those described as emanating from the Base]
• Gateway Lake Ash Study Area [generally described by the following coordinates: N667944.01/E1248056.74; N667694.15/E1248058.87; N667695.57/E1247811.84; N667947.55/E1247834.49; N667944.01/E1248056.74]
• Pride Hanger Study Area [generally described by the following coordinates: N673538.32/E1243066.96; N673267.45 /E1243270.27; N673228.21/E1243223.95; N673113.04/E1243308.87; N673021.04/E1243204.65; N673409.00/E1242911.91; N673538.32/E1243066.96]

Maps identifying all areas are available for review in the partial deletion docket.

Operable Unit 2

The OU-2 study area consists of Landfill No. 1, Landfill No. 6, the drainage channel in the western portion of Landfill No. 1, and the drainage channel near Landfill No. 6, which includes Pond 002.

Landfill No. 1 is approximately 21.5 acres in size and is located at the southern boundary of Ellsworth AFB. The landfill was active from the early 1940s to 1964 and was used to dispose of a variety of wastes including Base refuse, incinerator ash, sludge, oil, and possibly liquid industrial wastes. Hardfill debris was also disposed of at Landfill No. 1.

Landfill No. 6 is approximately 0.5 acres in size and is located northeast of Landfill No. 1 on the north side of Kenney Road. Landfill No. 6 was used from 1962 to 1965 and primarily received general Base refuse. Waste oil, fuel, and solvents may also have been disposed of at this location. However, no direct physical evidence of these chemicals was found at Landfill No. 6 during the 1993/1994 remedial investigation field activities.

Within OU-2, soils contained chlorinated volatile organic compounds (VOCs), benzene, toluene, ethyl benzene, xylenes (BTEX), pesticides, inorganic compounds, and polynuclear aromatic hydrocarbons (PAHs). The concentrations of several inorganic compounds exceed background concentrations. This is believed to be a combination of landfill activities and variations in the concentrations of naturally-occurring compounds in the soil. Jet fuel contamination caused by a leak in a fuel line was identified along the southern boundary of OU-2. This jet fuel contamination has been remediated under the SDDENR petroleum release program. Sediment samples collected at OU-2 contained semi-volatile organic compounds (SVOCs), primarily PAHs, pesticides and inorganic compounds. Low concentrations of three SVOCs were detected in surface water samples at OU-2, as well as numerous inorganic compounds. The concentrations of several inorganic compounds exceeded State and Federal water quality standards. However, the results of the risk assessment indicated that risk due to exposure to contaminants in sediments at OU-2 was within the acceptable risk range, and that surface water was not a media of current concern. Therefore, it was determined that remedial action was not warranted for surface water or sediment.

Two removal actions were completed at this OU. A site in the southwest corner of Landfill 1 identified during RI geophysical investigations was excavated in 1997. This location contained low-level radioactive waste material. A second removal action was completed for remnants of chemical weapons training materials located in the same general area. The identified materials were excavated and moved off Site for disposal at a licensed waste disposal facility.

The ROD was signed in May of 1996. The selected alternative for Landfill No. 1 was a vegetated soil cover and institutional controls. This alternative includes institutional controls, storm-water channel realignment and lining, in conjunction with physical modification of the OU to reduce potential risk. The selected alternative for Landfill No. 6 was institutional controls. This alternative uses access restriction, monitoring, and other controls to reduce potential risk. Construction for the storm-water channel was completed in October 1996. The landfill cover was completed in May 1997. Ground water remediation and monitoring are part of OU-11.

Operable Unit 3

OU-3, located in the northeast portion of Ellsworth AFB, consists of Landfill 2, (approximately one acre), the four identified trenches to the north and two disturbed soil areas in the southeast and southwest corners. The landfill was active for approximately one year (1964-1965). Combustible trash, described as shop wastes, was burned daily in a burn pit. Four trenches located north of the fill area were used for the disposal of metal and industrial and household refuse. A sign located within the boundary of OU-3 indicates a missile disposal/burial site. The missile disposal site contains scrap metal salvaged from a test flight. Contaminants identified in soil at this OU include, VOCs, jet fuel, numerous SVOCs, pesticides and inorganic compounds. The concentrations of several inorganic compounds exceed background concentrations.

The ROD was signed in June of 1996. The selected remedial action was a vegetated soil cover. This alternative includes institutional controls in conjunction with physical modification of the OU to reduce potential risk. The landfill cover was completed in May 1997. Ground water monitoring is part of OU-11.

Operable Unit 4

OU-4 (Landfill No. 3) is approximately 40 acres in size and is located in the southwestern corner of Ellsworth AFB. The landfill was active between 1965 and 1976 as a trench and fill operation. The landfill was also used for disposal of construction demolition debris during the mid-1980s, digested wastewater treatment plant biomass, shop wastes (liquids and paints), industrial sewer sludge and oils, soil containing Pramitol and sodium chromate, and miscellaneous refuse. The contents of approximately 100 55-gallon drums containing waste oil and fuel were placed in a waste-oil pit on site. OU-4 was also used as a staging area for 55-gallon drums containing waste oil and fuel. In addition, the southwest corner of OU-4 was used to stage asphalt rubble. Contaminants in soil at the OU include VOCs, PAHs, jet fuel, pesticides, polychlorinated biphenyls (PCBs), inorganic compounds, dioxins and furans. The concentrations of several inorganic compounds exceed background concentrations. Contaminants in sediment include acetone, PAHs, pesticides, and inorganic compounds. However, it was determined in the risk assessment that those levels of contaminants fell within the acceptable risk range and therefore, no remedial action was warranted for sediment.

The ROD was signed in May of 1996. The selected remedial action was a vegetated soil cover for the landfill, and extraction and treatment for ground water. This alternative includes institutional controls in conjunction with physical modification of the OU to reduce potential risk. The landfill cover was completed in December 1996. Ground water remediation and monitoring are part of OU-11.

Operable Unit 5

OU-5 (Landfill No. 4) is a 10-acre site located adjacent to the north perimeter of Ellsworth AFB. From the 1940s through 1990, the landfill was used primarily for the disposal of construction demolition and hardfill materials, general refuse and drums. Contaminants in soil at OU-5 include PAHs, pesticides, inorganic compounds, and jet fuel. The concentrations of several inorganic compounds exceed background concentrations. One surface water and one sediment sample were collected at OU-5 from an ephemeral surface water source. These samples contained VOCs, SVOCs, and inorganic compounds. However, it was determined in the risk assessment that those levels of contaminants fell within the acceptable risk range and therefore, no remedial action was warranted for surface water or sediment.

The ROD was signed in June of 1996. The selected remedial action was a vegetated soil cover. This alternative includes institutional controls in conjunction with physical modification of the OU to reduce potential risk. The landfill cover was completed in May 1997. Ground water monitoring is part of OU-11.

Operable Unit 6

OU-6 (Landfill No. 5) is a 7-acre site located in the southeastern corner of Ellsworth AFB. From 1960 to 1980, demolition debris and hardfill materials were placed in the landfill along with miscellaneous refuse, dried sewage sludge, and possibly shop wastes. Construction and demolition debris was initially placed along the rail line to stabilize erosion, and was later expanded to the east. OU-6 was used for stockpiling wastewater treatment plant sludge. Contaminants in soil at OU-6 include PAHs, pesticides, and inorganic compounds. The concentrations of several inorganic compounds exceed background concentrations. Contaminants in surface water and sediment include VOCs, SVOCs, pesticides and inorganic compounds. However, it was determined in the risk assessment that those levels of contaminants fell within the acceptable risk range and therefore, no remedial action was warranted for surface water or sediment.

The ROD was signed in October of 1995. The selected remedial action was a vegetated soil cover, and long-term surface water and sediment sampling. This alternative includes institutional controls in conjunction with physical modification of the OU to reduce potential risk. The landfill cover was completed in July 1996. Ground water monitoring is part of OU-11.

Operable Unit 7

OU-7 (Low-Level Radioactive Waste Burial Site) is located in the Munitions Storage Area (MSA), formerly identified as the Weapons Storage Area (WSA), at the northernmost end of Ellsworth AFB. The MSA covers approximately 65 acres. Radioactive wastes were generated at Ellsworth AFB between 1952 and 1962. During that time the WSA was under the control of the Atomic Energy Commission (AEC). After 1962, control of the WSA was transferred to the Air Force. Contaminants in soil at OU-7 include VOCs and inorganic compounds. Contaminants in surface water and sediment include VOCs and inorganic compounds. The concentrations of several inorganic compounds in soil and sediment exceed background concentrations. Radionuclides detected in all media were within the normal background range due to natural variations in soil types and geological characteristics. The results of the risk assessment indicated that risk due to exposure to contaminants in surface water and sediments at OU-7 was within the acceptable risk range. Therefore, it was determined that remedial action was not warranted for surface water or sediment.

The ROD was signed in June of 1996. The selected remedial action was application of institutional controls for soil and ground water, completion of detailed records searches and long term ground water monitoring. Ground water monitoring is part of OU-11.

Operable Unit 8

OU-8 (Explosive Ordnance Disposal Area) is located in the northeastern portion of Ellsworth AFB. OU-8 consists of two distinct areas, the Explosive Ordnance Disposal (EOD) Area and the Debris Burial Area. The EOD Area is approximately 600 feet by 1,350 feet, and the Debris Burial Area is approximately 300 feet by 150 feet. The EOD Area includes: A Pramitol (an herbicide) spill area, a burn pit area, a burn furnace area, and a detonation site. This detonation area was formerly used for the detonation of active explosives. The Debris Burial Area was used for the burial of debris generated from detonation of explosives at the demolition area. Contamination in soil at this OU includes VOCs, SVOCs (primarily PAHs), jet fuel, pesticides, dioxins/furans, and inorganic compounds. The concentrations of several inorganic compounds in soil and sediment exceed background concentrations. One pesticide was detected in sediment samples. However, it was determined in the risk assessment that those levels of contaminants fell within the acceptable risk range and therefore, no remedial action was warranted for sediment.

The ROD was signed in June of 1996. The selected remedial action was installation of vegetated soil covers, application of institutional controls and long term sediment sampling. The soil covers over the EOD Area and the Debris Burial Area were completed in June 1997. Ground water monitoring is part of OU-11.

Operable Unit 9

OU-9 encompasses 90 acres surrounding the Old Auto Hobby Shop. The types of potential contaminant source areas at OU-9 include: Building Operations, underground storage tanks, the former Quartermaster Gasoline Dispensing Area, the former fuel transfer line, industrial waste lines, jet engine test facilities and upgradient source areas. There is no known documentation of major spills or releases at OU-9. Small volumes of fuels, oils, and solvents may have been released to the environment over time through incidental spills, leaks, and/or poor waste handling and disposal practices. Contaminants in soil at this OU include VOCs (primarily BTEX), SVOCs (primarily PAHs), jet fuel, and inorganic compounds. Several inorganic compounds were detected in surface water and sediment samples. PAHs were also reported in sediment samples.

It was determined that OU-9 did not pose a threat to human health or the environment. In May 1996, a ROD was signed for no further action. Remediation of soils contaminated by petroleum will be performed under the SDDENR petroleum release program. Ground water remediation was deferred to OU-11.

Operable Unit 10

OU-10 is the North Hangar Complex, a 75-acre site located in the central portion of Ellsworth AFB, northeast of the primary instrument runway. The North Hangar complex was constructed in the 1950s and is composed of five rows of aircraft repair and maintenance hangars. Most of OU-10 is paved with concrete with some grassy areas between the hanger rows. OU-10 contains a system of underground jet fuel hydrant lines that deliver fuel to docked aircraft, and underground industrial waste lines associated with aircraft maintenance. It was reported that waste products used for aircraft maintenance may have been washed down floor drains in the maintenance buildings. Contaminants at this OU included VOCs, SVOCs and jet fuel. The predominant VOCs were BTEX compounds.

It was determined that OU-10 did not pose a threat to human health or the environment. In May 1996, a ROD was signed for no further action. Remediation of soils contaminated by petroleum will be performed under the SDDENR petroleum release program. Ground water remediation was deferred to OU-11.

Operable Unit 12

OU-12 (Hardfill No. 1) is located in the southern half of Ellsworth AFB and is approximately 14 acres in size. OU-12 was identified as a hardfill, rather than a landfill, because disposal records indicated that it only received construction debris such as wood, metal, concrete, and asphalt. The remedial investigation identified the presence of VOCs, SVOCs, jet fuel and pesticides, but through site characterization it was found that these contaminants were related to flightline runoff rather than landfill disposal practices.

The ROD was signed in May of 1996. The selected remedial action was a vegetated soil cover. This alternative includes institutional controls in conjunction with physical modification of the OU to reduce potential risk. The soil cover was completed in May 1997. Ground water monitoring is part of OU-11.

Five-Year Review

The initial five-year review for Ellsworth AFB base was completed in September 2000. The second five-year review was completed in September 2005. The reviews focused on the final remedial activities at each OU. Discussions and recommendations were included for the long-term ground water actions at the OUs and for Operation and Maintenance issues with landfill covers.

V. Deletion Action

EPA, with the State of South Dakota's concurrence, has determined that no additional response is necessary at Ellsworth AFB for surface soil, unsaturated subsurface soil, surface water and sediment media at OU-2, OU-3, OU-4, OU-5, OU-6, OU-7, OU-8, OU-9, OU-10 and OU-12 (approximately 542 acres) and the surface soil, unsaturated subsurface soil, surface water and sediment media of an additional 4,300 acres which are not associated with an operable unit and are not identified as posing a risk to human health or the environment.

No further CERCLA response is appropriate or necessary to provide protection of human health and the environment other than the ongoing inspection, maintenance and monitoring activities. Therefore EPA is deleting these portions of the Ellsworth AFB Site. OU-1, OU-11, the Pride Hanger Study Area and the Gateway Lake Ash Study Area will remain on the NPL.

Dated: June 8, 2006.

Kerrigan G. Clough,

Acting Regional Administrator, U.S. Environmental Protection Agency, Region 8.