Rocky Flats Site Background
The Rocky Flats site was selected in 1951 by the Atomic Energy Commission to serve as part of the nation’s nuclear weapons manufacturing complex. The site is located 16 miles northwest of downtown Denver, Colorado in Jefferson County, on a plateau just east of the Front Range foothills of the Rocky Mountains. Originally, the site was 2,600 acres. Additional parcels of land were acquired subsequently for a maximum size of roughly 6,500 acres, including a small area extending into Boulder County. The site was first operated by Dow Chemical. Operations began at Rocky Flats in 1952, and processing and machining of plutonium into detonators (aka triggers) began at the site in 1953. Components were formed from beryllium, plutonium, stainless steel, uranium, and other metals. The plant also produced military components from depleted uranium and processed plutonium for reuse (Department of Energy [DOE], 2011).
Beginning in the 1970’s, several major protests occurred, some with thousands to tens of thousands of demonstrators. Various incidents and accidental releases occurred at the site during the roughly four decades of production. Key recorded releases of radionuclides affecting offsite areas include the following:
1957 – Fire in Building 771. A fire occurred in a glovebox in plutonium processing Building 771.
1958-1969 – Windblown Contamination from the 903 Pad. Surface soils contaminated by leaking waste-storage drums at the 903 Pad were transported by wind to areas east of the site. More than 3,500 55-gallon drums were stored at the 903 Pad, and many were found to have corroded and leaked contents onto surrounding soils. Drum contents of key concern included plutonium-contaminated lathe coolant. An asphalt pad was placed over the site in 1969.
1969 – Fire in Building 776/777. There was a major fire in a glovebox in Building 776/777.
1970 to 1973 - Release of Detention Pond Sediments to Walnut Creek. Sediments from Walnut Creek A- and B-series detention ponds were released offsite during a re-engineering project. These sediments flowed into Great Western Reservoir.
1973 – Tritium Release to Walnut Creek. Contaminated scrap material from Lawrence Livermore National Laboratory was blamed for release of tritium to Walnut Creek, flowing into Great Western Reservoir, then a water supply for Broomfield.
On June 6, 1989, the FBI and the EPA conducted an armed raid of Rocky Flats, operated at the time by Rockwell International, in search of evidence of environmental crimes. Later in 1989, the site was listed on EPA’s National Priorities List based on investigations indicating release of materials defined as hazardous substances under CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act) and RCRA (Resource Conservation and Recovery Act), and the Colorado Hazardous Waste Act (CHWA).
In 1992, then-President George H. W. Bush cancelled the W-88 Trident Warhead program, terminating Rocky Flats’ production mission. In 1994, nonnuclear production at the site was also terminated. This changed the site mission to one of cleanup and closure. At this time, there were more than 800 structures in the industrial area, including 150 buildings and 90 trailers. By this time, the site was divided into three areas: the Industrial Area (IA), the Protected Area (PA), and the Buffer Zone (BZ). The IA (385 acres at the center of the site) contained buildings and structures. The PA, located within the northern portion of the IA, was even more heavily fenced and guarded than the IA since it contained the complex of plutonium production facilities. The BZ was the land surrounding the IA. It was also fenced and guarded to protect the site from incursion.
In 1996, the Woman Creek Reservoir (WCR) was constructed on Woman Creek using Federal funding as part of the Standley Lake Protection Project (SLPP). The WCR physically separates Standley Lake, the drinking water source for the Cities of Northglenn, Thornton, and Westminster, from surface water leaving Rocky Flats. The WCR captures flow from Woman Creek as it exits the RFS and subsequently pumps that water to Walnut Creek, thereby bypassing Standley Lake. Prior to WCR construction, Woman Creek water from Rocky Flats had been diverted to Church Ditch, thereby bypassing Standley Lake since the late 1980’s (D. Strietelmeier, personal communication, 2014).
In 1997, while clean-up and closure work continued at the site, a Corrective Action Decision/Record of Decision (CAD/ROD) was issued for Offsite Areas at Rocky Flats (DOE, 1997). Based on the investigation results and risk assessment, this CAD/ROD found risks to be below minimum thresholds of concern set by the Environmental Protection Agency (EPA) and the Colorado Department of Public Health and Environment (CDPHE). The CAD/ROD concluded that the appropriate remedial action for Offsite Areas was no action (DOE, 1996 and EPA, 1997). The investigation and findings are discussed in greater detail in Section 2 of this memorandum.
Characterization, clean-up, and closure activities at the site itself continued through 2005. During that time, 21 tons of weapons-grade nuclear material were removed, structures were demolished, storage and waste sites were remediated, some drainages were reconfigured, and more than 1.3 million cubic meters of waste were removed (Kaiser-Hill, 2006). Following completion of cleanup in October 2005, the remedial investigation and comprehensive risk assessment were completed to support selection of the final remedy for the Site (Kaiser-Hill, 2006 and EPA, 2006).
In September 2006, the CAD/ROD for the Site (EPA, 2006) was released. The RFS was regrouped into two operable units: the Central OU and Peripheral OU. The Central OU consisted of 1,300 acres, inclusive of the former PA and IA and site terminal ponds. The remaining, surrounding 4,900 acres were designated as the Peripheral OU. These areas are shown on Figure 1, along with Standley Lake, Great Western Reservoir, and Mower Reservoir. The CAD/ROD indicated no action as the appropriate response action for the Peripheral OU. For the Central OU, the CAD/ROD indicated institutional controls (to limit access and soil disturbance) and continued monitoring as the response action.
In March of 2007, the Rocky Flats Legacy Management Agreement (RFLMA) was signed by DOE, EPA, and CDPHE. The purpose of RFLMA is to define the regulatory framework for implementing the final remedy to ensure that conditions remain protective of human health and the environment. RFLMA includes monitoring, maintenance, and reporting requirements. Long-term care of the Central OU and adherence to RFLMA is the responsibility of the DOE Office of Legacy Management (LM). This includes monitoring and maintenance of two closed landfills and four groundwater treatment systems. The Peripheral OU was transferred to the U.S. Department of Interior for management by the U.S. Fish and Wildlife Service in July 2007.
There are numerous sources of information on the history of Rocky Flats. The following key sources were reviewed in development of this brief history: Buffer (2003), Rocky Flats Stewardship Council (RFSC; 2008), and DOE (2011). Figure 2 presents a timeline of these key releases and regulatory events.