Atlas E Site 566-6 Missile Silo, Briggsdale Colorado

Atlas E Site 566-6 was a single-missile SM-65E Atlas intercontinental ballistic missile launch complex associated with the 566th Strategic Missile Squadron and the F.E. Warren Air Force Base missile field. It was one of the nine Atlas E sites operated by the 566th SMS under the 389th Strategic Missile Wing. The site is commonly identified as Site 6, Briggsdale, Colorado, and federal environmental records identify the cleanup property as Warren F.E. AFB Atlas "E" Missile Site #10, 3 1/2 miles northwest of Briggsdale, Weld County, Colorado.

The site is no longer an active missile installation. The Atlas E mission ended during the 1964-1965 phaseout of the Atlas force, and the site was decommissioned in 1965. Colorado environmental records describe the former Atlas 10 property as covered with soil and owned by the U.S. Forest Service. EPA identifies the site as not on the National Priorities List and states that no further federal action will be taken.

Location, Landscape, and Site Description

Site 566-6 lies in the shortgrass plains of northeastern Colorado near Briggsdale, in Weld County. The setting is open, rural, and sparsely developed, matching the Atlas E deployment logic of spreading individual missiles away from one another while still keeping them within the support reach of F.E. Warren AFB at Cheyenne. The surrounding landscape is part of the northern Colorado plains, an area of rangeland, agricultural use, and federal grassland holdings.

The site was an Atlas E individual coffin-launcher complex. Unlike the earlier Atlas D complexes that grouped three missiles together, each Atlas E operational site housed one missile and its own control, service, power, fueling, access, and security functions. The missile itself was stored horizontally in a below-ground or semi-buried "coffin" structure. In a launch sequence, the coffin roof opened, the missile was raised to vertical, and the weapon was fueled and prepared for launch.

EPA places the former site 3 1/2 miles northwest of Briggsdale in Township 8 North, Range 63 West, Section 24. Site photographs and aerial views show the road loop and disturbed launch-complex footprint remaining recognizable in the open plains landscape.

Strategic and Cold War Context

The Atlas E sites around F.E. Warren belonged to the first generation of American operational ICBM deployment. Atlas made it possible for Strategic Air Command to place nuclear-armed missiles on alert within the continental United States rather than relying only on bomber forces or forward-deployed systems. The early Atlas force was strategically important, but it was also a transitional system: it provided an operational ICBM capability while the Air Force moved toward more survivable and easier-to-maintain Titan and Minuteman systems.

F.E. Warren's Atlas E field was known as Warren III. The base history explains that Warren III was designed for nine SM-65E Atlas missiles scattered at single coffin-launcher sites. The coffin design offered limited protection by placing the missile below ground rather than in an exposed gantry, and Atlas E's inertial guidance allowed each missile to be deployed singly rather than tied to a shared radio-guidance arrangement.

Construction and Activation

Site 566-6 was constructed as part of the Warren III Atlas E program. Construction began in 1960 and turnover to the Air Force in 1961. The official 566th SMS unit summary records turnover to Strategic Air Command and operational status for the squadron on 1961-03-30. The site therefore belongs to the 1960-1961 construction and activation period for the 566th SMS Atlas E field.

Construction of a remote Atlas E site required far more than the missile shelter itself. The site had to support a launch crew, a control function, power generation, missile servicing, propellant handling, utilities, security, access roads, communications, and specialized maintenance. The semi-hardened coffin launcher reflected the Air Force's attempt to improve survivability while still working within the limits of the liquid-fueled Atlas missile and its launch-preparation sequence.

Missile System and Technical Role

Site 566-6 housed one SM-65E Atlas missile. Atlas E used inertial guidance and was deployed at individual coffin-launcher complexes. The Association of Air Force Missileers describes Atlas E as a singly deployed missile with one control center per missile, and describes the coffin roof as being at ground level with limited overpressure protection. Combat crews included two officers and three enlisted members, and crews stood 24-hour alerts before being relieved by a new crew sent from the main base.

The Atlas E was a liquid-fueled ICBM using RP-1 kerosene and liquid oxygen. Because liquid oxygen was cryogenic, Atlas missiles did not sit fully fueled for long periods in the way later solid-fueled missiles could remain on alert. During a launch sequence, the crew opened the coffin, raised the missile, loaded propellants, completed checks, and then launched if ordered. Public missile-history sources describe Atlas E as having an approximately fifteen-minute launch response time.

Missile capability, warhead, and reentry vehicle: Atlas E was an early liquid-fueled ICBM designed to deliver a single nuclear warhead at intercontinental range. National Park Service material describes Atlas E as an individual-complex, inertially guided missile deployed in below-ground coffins. The 566th SMS source identifies the Atlas E as using a Mark IV reentry vehicle and W-38 nuclear warhead with an approximately 3.8-megaton yield. The Smithsonian's National Air and Space Museum identifies the Mark 4 reentry vehicle as carrying a W-38 nuclear warhead with a yield of about 3.75 megatons.

Operational History

Site 566-6 served as one of the nine dispersed Atlas E launch complexes assigned to the 566th Strategic Missile Squadron at F.E. Warren AFB. The squadron had a short operational life in the Atlas mission. It was activated as a missile squadron in 1959, moved into the F.E. Warren Atlas E role in 1961, and operated until the Atlas E force was phased out in the mid-1960s.

The normal operational life of Site 566-6 centered on alert duty. The missile crew at the remote site was responsible for keeping the Atlas E weapon system ready, while maintenance and support personnel kept the launcher, missile systems, electrical equipment, environmental systems, propellant-handling equipment, guidance equipment, and communications functioning. The need to keep the Atlas missile pressurized added to the constant maintenance burden. National Park Service material explains that Atlas missiles required pressurization while on alert because the thin stainless-steel shell depended on internal pressure to maintain its structure on the ground.

The site's operational period included the Cuban Missile Crisis. F.E. Warren's official base history states that, during the crisis, the 389th Strategic Missile Wing placed all of its Atlas missiles in launch configuration and maintained a ready posture until 1962-11-27. That statement is a wing-level record rather than a separate site-specific incident report, but it directly describes the alert posture of the Atlas force to which Site 566-6 belonged.

Deactivation and Disposal

Atlas E had a short service life because the system was overtaken by more survivable and operationally efficient missiles. The official 566th SMS summary records the first squadron ICBM off alert on 1964-10-01 and the last ICBM shipped on 1964-10-22. It lists the squadron as inactivated on 1964-12-15, while the station entry runs to 1965-03-25.

Colorado's Department of Public Health and Environment states that the five former Colorado Atlas E sites were decommissioned, had their missiles removed in 1965, and were then sold to public and private owners. For Site 566-6, CDPHE identifies the corresponding Colorado cleanup property as Atlas 10. It states that Atlas 10 is covered with soil and owned by the U.S. Forest Service.

CDPHE's environmental summary provides important detail about what happened after military use ended. It states that the Colorado Atlas sites are FUDS cleanup sites under the U.S. Army Corps of Engineers, Omaha District, and that they are investigated under the federal CERCLA/Superfund process even though they are not on the Superfund National Priorities List. CDPHE states that soil contamination from petroleum chemicals and/or PCBs was found at all five Colorado Atlas sites, but identifies groundwater trichloroethylene contamination specifically at Atlas 11, 12, and 13. It also states that there is no evidence of radioactive contamination at the Atlas sites, and explains that warhead maintenance occurred at warhead manufacturing facilities rather than at the missile sites themselves.

For Atlas 10 specifically, CDPHE says investigations were completed, a soil removal action was conducted in 2007, site closure was completed in April 2008, and no further cleanup actions were planned. EPA's CERCLA record identifies the site as Warren F.E. AFB Atlas "E" Missile Site #10, EPA ID CO0009138998, not on the National Priorities List, with a no-further-federal-action determination.

Chronology

• 1959-08-15 The 566th Strategic Missile Squadron was activated.
• 1960 Construction began at Site 566-6.
• 1961 Site 566-6 was turned over to the Air Force.
• 1961-03-30 The 566th SMS was turned over to Strategic Air Command and recorded as operational in the official unit summary.
• 1961-07-01 The 566th SMS was assigned to F.E. Warren AFB under the 389th Strategic Missile Wing.
• 1962-03-02 The Atlas-era 566th SMS emblem with nine stars representing the nine dispersed launch sites was approved.
• 1962-10 During the Cuban Missile Crisis, the 389th Strategic Missile Wing placed its Atlas missiles in launch configuration.
• 1962-11-27 F.E. Warren's Atlas crisis posture ended after the Cuban Missile Crisis abated.
• 1964-10-01 The first 566th SMS ICBM was removed from alert.
• 1964-10-22 The last 566th SMS ICBM was shipped.
• 1964-12-15 The 566th Strategic Missile Squadron was inactivated.
• 1965 CDPHE states that the former Colorado Atlas E sites were decommissioned and their missiles removed.
• 1965-03-25 Site 566-6 is listed as decommissioned.
• 2007 CDPHE states that a soil removal action was conducted at Atlas 10.
• 2008-04 CDPHE states that site closure was completed at Atlas 10 and no further cleanup actions were planned.

Read about the Atlas at F.E. Warren AFB

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