Record of Decision System (RODS)
HILL AIR FORCE BASE
|Site Name:||HILL AIR FORCE BASE|
|City & State:||HILL AFB UT 84056|
|NPL Status:||Currently on the Final NPL|
|ROD Type:||Record of Decision|
|Media:||Surface water, groundwater|
Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.
The 6,700-acre Hill Air Force Base is located in northern Utah, about 25 miles north of Salt Lake City and about five miles south of Ogden, Utah. Hill AFB is located on the Weber Delta, a terrace approximately 300 feet above the surrounding valley floors in Weber and Davis Counties. OU4 overlies three aquifers. The shallow lies within about 30 feet of ground surface. The Sunset and Delta Aquifers are approximately 300 and 600 feet below the OU4 landfills, respectively. The Weber River and the Davis-Weber Canal are the primary surface water bodies near OU4. There are no wetlands on the base. The areas adjacent to OU4 are primarily residential, with some unimproved areas and waste disposal sites to the south and west. Hill AFB has been the site of military activities since 1920 and is still in operation today.
On-base industrial processes associated with aircraft, missile, vehicle, and railroad engine maintenance and repair, include: metal plating, degreasing, paint stripping, and painting. These processes use numerous chemicals, including chlorinated and non-chlorinated solvents and degreasers, petroleum hydrocarbons, acids, bases, and metals. Past disposal activities included disposal pits and landfills, as well as the Industrial Waste Treatment Plant.
In July 1987, Hill Air Force Base (AFB) was placed on the National Priorities List (NPL). In 1991, Hill AFB entered into a Federal Facilities Agreement (FFA) between the U.S. Air Force, the Utah Department of Environmental Quality, and the U.S. EPA. There have been no removal actions, remedial actions, notices of violation, or other enforcement actions taken at operable unit 4 (OU4) prior to this ROD.
Landfills 1 and 2 were identified in the Phase 1 Installation Restoration Program (IRP) investigation in 1982. A Phase II IRP (1988) and initial Remedial Investigation (RI) conducted from 1987 to 1990 indicated volatile organic compounds (VOCs) and metals present in ground water and seeps. The North Gate Dump Area was identified as part of OU 4 during the initial RI. The Munitions Dump was included as part of the Phase II RI. The Spoils Pit was designated as part of OU 4 under the FFA in 1991. An addendum to the RI was prepared in 1992 identifying the extent and quantity of ground water contamination and the primary source.
Operable unit 4 (OU 4) is comprised of Landfills 1 and 2, the Spoils Pit, the North Gate Dump Area, and the Munitions Dump.
Solid wastes were dumped and burned daily in Landfill 1 from 1955 to 1967. Landfill 1 is the source of TCE contamination observed in ground water and seeps at OU4.
Solid waste disposal took place at Landfill 2 from 1963 to 1965, where wastes were burned periodically. Based on investigation results, Landfill 2 is not a source of contamination at OU4.
Construction debris and yard waste from the Base were disposed of in the Spoil Pit from 1971 to 1987. The Spoil Pit is not a source of subsurface contamination at OU4.
The Munitions Dump was operated as an above ground munitions storage area during WWII. Investigations have shown that the Munitions Dump is not a source of contamination.
Several drums of waste solvent were reportedly dumped from trucks in the North Gate Dump Area. No drums have been found in this area, and investigations reveal that this area is not a source of contamination.
This ROD addresses operable unit 4 (OU4) which consists of contaminated ground water, surface water, and air. Operable unit 4 is one of eight OUs at Hill Air Force Base. This action also addresses the landfill which is the source of contamination. The purpose of this remedy is to prevent exposure to contaminated ground water, surface water, landfill contents, and air; reduce contaminant migration from the landfill; and reduce the volume of contaminants in the source area. This is the final response action for OU 4.
|Remedy:||Extracting contaminated ground water using horizontal drains or vertical wells, treating the ground water by air stripping, and discharging the treated ground water to the local publicly-owned treatment works; treating ground water for metals as necessary to meet discharge requirements; treating emissions from the air stripper system to meet state emission limits; collecting surface water and treating it with carbon adsorption when a sufficient volume of water is produced to operate the treatment system; discharging treated surface water through infiltration trenches; capping the contents of Landfill 1 and treating the source of contamination by soil vapor extraction; semi-annual air monitoring in the basements of residences overlying the contaminated ground water; institutional controls on well use and well drilling; and ground water monitoring.|
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