Site Overview
Atlas D Missile Site 4 located in Laramie County, Wyoming is a Formerly Used Defense Site (FUDS), previously under the command of F.E. Warren Air Force Base (AFB). The U.S. Army Corps of Engineers (USACE), Omaha District, is managing the environmental cleanup as a result of former activity at the site. The site is located approximately 18 miles west of Cheyenne and one mile south of the town of Granite, Wyoming. The site vicinity is illustrated in 
Figure 1.
The property was one of four Atlas "D" missile sites and nine Atlas "E" missile sites operated in Colorado, Nebraska and Wyoming by F.E. Warren AFB. The sites were operated as part of the 706th Strategic Missile Wing, including the 549th Strategic Missile Squadron training unit and the 389th Strategic Missile Wing, including the 564th and 565th Strategic Missile Squadron operational units. Site 4 was used for the housing, readiness, and potential launch of nuclear missiles. Trichloroethene (TCE) was used as a solvent to clean the rocket fuel tanks, engines, and/or liquid oxygen lines following readiness exercises. Wash water and TCE flowed into unlined waste channels. The amount of TCE that may have been released to the subsurface has been estimated to have ranged from 450 to possibly as much as 16,200 gallons.
Six models of the Atlas missile were built, of which the Atlas A, B, and C were prototypes. The Atlas D was the first fully-operational strategic missile developed by the U.S. and, with a range of 8,700 miles, was designed for the deployment of high-yield nuclear warheads against the Soviet Union. It was a liquid-fueled rocket that used Rocket Propellant-1 (“RP-1”, similar to kerosene) for fuel and liquid oxygen as the oxidizer.
During readiness exercises called Dual Propellant Loads (DPL), the missiles were fueled and defueled, and the RP-1 rocket fuel was pumped back into an underground storage tank. At the beginning of a DPL, a truck carrying TCE arrived at the launcher and filled a 500-gallon tank. TCE was used as a solvent to clean the rocket fuel tanks, engines, and/or liquid oxygen lines through a series of flushing exercises to prevent accidental explosions. Water was used to remove a highly unstable and explosive gel which formed when liquid oxygen and RP-1 combined, which then drained into a flame pit constructed to direct the missile exhaust away from the immediate launch area. Liquid in the flame pit flowed into an unlined waste channel and burnout pit, and was subsequently discharged onto the ground surface. The waste channel and burnout pits are constructed 20 to 30 feet below ground and were over 800 feet in length. A site map, showing key site features and their respective orientation to one another, is provided as Figure 2.
Site 4 consisted of approximately 703 acres acquired by purchase and condemnation between 1959 and 1962, and was developed during that time. By 1964, the liquid fuel Atlas D missiles were being phased out in favor of new solid fuel Minuteman Intercontinental Ballistic Missiles, and the property was excessed to the General Services Administration (GSA) for disposal in 1965.
In early 1967, 338 acres of fee and easements were conveyed by quitclaim deed to Southern Scrap Iron and Metal Company of St. Louis, Missouri. That property was subsequently sold to the Belvoir Grazing Association of Ault, Colorado. The GSA sold the remaining property to Belvoir Grazing and Timnath Farms in January 1976. The site was acquired by the City of Cheyenne and the Cheyenne Board of Public Utilities (CBOPU) in 2003, whereby the property is leased for cattle grazing and stock watering.
The primary contaminant identified at the site is TCE in groundwater. The presence of TCE is attributed to its use to clean rocket engines of impurities after readiness exercises when the site was operational in the early 1960s. The actual number of exercises at Site 4 and quantity of TCE used for each exercise, is not recorded and cannot be definitively determined. Anecdotal estimates (i.e., approximate values) of the number of refueling exercises range from two to six times per year, and TCE quantity estimates range from 25 to 300 gallons of TCE per exercise. Speculative estimates of up to 6,000 gallons of water per exercise were also noted. Based on these estimates, the amounts of TCE used per year were calculated to range between 50 and 1,800 gallons per year. The site was operational for three years; therefore, between 150 and 5,400 gallons of TCE may have been released per launch area. TCE has been detected on-site at the former Atlas Missile Site 4 at a maximum level of 6600 parts per billion (ppb).
Previous environmental investigations and studies completed at Site 4 include:
- Underground Storage Tank Removal, Tank Closure Report (ABT, 1993);
- Preliminary Assessment and Site Investigation (LTE, 2002);
- Interim Response Action (RMC, 2003);
- Final Expanded Site Investigation Report (USACE, 2003);
- Final Expanded Site Investigation Report Addendum (USACE, 2005);
- Final Remedial Investigation Report (USACE, 2006);
- Remedial Action Alternatives Technical Memorandum (RMC, 2006);
- Supplemental Investigation Findings Technical Memorandum (RMC, 2008);
- Final Technical Memorandum for 2008 Supplemental Investigations (RMC, 2009).
Site 4 and the down gradient Belvoir Ranch property and adjoining properties have been segregated into three general areas based on site characteristics, topography, and contaminated media. The three general areas are defined as Area A, Area B, and the Transition Zone. As established previously by USACE and stakeholders, the launch and service building area of Site 4 (Section 20, Township 13 North, Range 69 West [6th Principle Meridian]) is referred to as Area A. Area A comprises the contaminant source area. Numerous monitoring wells have been installed in this area by USACE. The western portion of the Borie Well Field (Sections 7 through 36 in Township 13 North, Range 68 West) is referred to as Area B. The west edge of Area B is located four miles east of Area A. Numerous residential, industrial, municipal, and irrigation wells are located in Area B. Several deep oil wells are also located in the northeastern part of Area B. Areas A and B are connected by a four-mile long segment of Lone Tree Creek and adjacent upland areas; this transition zone area is roughly four miles long and three miles wide (i.e., including Sections 13-17 and 21-27). Several monitoring wells have also been installed in this area by the USACE. Two stock wells are located in the northwest corner of this area (1/2 mile northeast of Area A) and a few residential (domestic) wells are located in the northeast part of this Transition Zone area. These areas are illustrated on Figure 2-1.
