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Record of Decision System (RODS)

F.E. WARREN AIR FORCE BASE

Abstract

Site Name:  F.E. WARREN AIR FORCE BASE
Address:  I-25 AND RANDALL AVENUE
90TH SUPPORT GROUP/DEV BLD 320 
City & State:  CHEYENNE  WY  82005
County:  LARAMIE
 
EPA ID:  WY5571924179
EPA Region:  08
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/541/R-97/194
ROD Date:  09/30/1997
Operable Unit(s):  02
 
Media:  Groundwater. soils,surface water
 
Contaminant:  TCE, cis-1,2-DCE, VOCs, semivolatile organic compounds (SVOCs), metals
 
Abstract:  F.E. Warren Air Force Base (FEW) occupies 5,866 acres immediately adjacent to and hydrogeologically upgradient of the west side of the City of Cheyenne, Wyoming. FEW was placed on the NPL on February 21, 1990. Historically, FEW has served a number of military functions, including cavalry outpost, quartermaster depot, and intercontinental ballistic missile (ICBM) operations base. FEW underwent extensive renovation after World War II. The majority of the Army training facilities were torn down and not replaced. Construction since that time has centered on facilities for U.S. Air Force (USAF) operations. Beginning in 1958, FEW became a Strategic Air Command base. Since then, FEW has served as an operations center for the Atlas ICBM, the Minuteman I and III, and the Peacemaker (MX) ICBMs. FEW was part of Air Combat Command from 1992 to 1993, and in July 1993, became part of Space Command.In April 1995, USAF implemented a treatability study. The treatability study was designed to remove trichloroethene (TCE) and its degradation products from groundwater through the use of a collection and treatment system. The collection system consisted of horizontal drains installed below the ground surface; air stripping towers to remove TCE and it degradation products from the groundwater; and a granular activated-carbon filter to treat the gases from the air stripping towers. The treated groundwater was reinjected into the aquifer upgradient of the collection drains. The treatability study was operated for a period of 12 months. Although TCE concentrations in some monitor wells within the influence of the treatability study showed decreases, TCE concentrations between the collector drains and Diamond Creek remained elevated and actually increased. Additionally, contaminated groundwater was bypassing the collector drains and reaching Diamond Creek. Operable Unit 2 (OU 2) groundwater beneath and downgradient of the study area contains significant concentrations of TCE and its degradation products. Through the results of the completed remedial investigation (RI) activities, USAF has determined the grease trap at the area was a source of TCE groundwater contamination. To control TCE contamination in shallow groundwater beneath and downgradient of the area, an interim remedial action (IRA) has been selected. As remedial investigations are completed, remedies will be selected for contaminated groundwater at F.E. Warren Air Force Base.
 
Remedy:  The selected IRA for the top 15 feet of groundwater is an in situ passive treatment wall. OU 2 is one of ten OUs that will be investigated under terms of the Federal Facility Agreement (FFA). The in situ passive treatment wall will address contaminants in groundwater at and downgradient of using an iron filings passive treatment wall technology. Groundwater beneath the area is only a portion of the groundwater identified for OU 2. The function of the IRA is to reduce the groundwater contamination in the top 15 feet of the aquifer beneath the site, and thereby, reduce the risks associated with exposure to contaminated groundwater. Groundwater contaminants addressed by the IRA include TCE, vinyl chloride, 1,2-dichloroethene (1,2-DCE), trans 1,2-DCE an cis-1,2-DCE. While the IRA addresses one of the principal threats at the site (i.e., indicator contaminants of concern (ICOCs) in the top 15 feet of groundwater) the final remedial alternative will address remediation of other environmental media, in addition to the remainder of groundwater, and other types of contaminants that pose an unacceptable risk at the site. The selected IRA will meet the remedial action objectives by directing the groundwater through the in-situ passive treatment wall. Although the selected IRA is an innovative technology, it is expected to degrade the target contaminants to acceptable levels.
 
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