 |
Details of the Rocky Flats Site
Rocky Flats was similar to a small city. It comprised more than 800 structures on a 385-acre industrial area surrounded by nearly 6,000 acres of controlled open space. The open space serves as a buffer between Rocky Flats and the nearby growing communities and is home to many species of animals and plants. In addition to the industrial facilities, Rocky Flats had its own fire department, medical offices, cafeterias, garage, gas pumps, steam plant, and water- and sewage treatment plants.
Water at RFETS and the surrounding area is distributed among surface water, shallow groundwater, and deep groundwater. Surface-water flow across RFETS is primarily from west to east, with three major drainages: North and South Walnut Creeks and Woman Creek in the Industrial Area. Walnut Creek flowed into the Great Western Reservoir about a mile and a half from the plant. In 1989, Broomfield built a diversion ditch around the reservoir to prevent surface drainage and runoff from Rocky Flats from entering the reservoir via Walnut Creek. In 1997, the city secured a new drinking-water supply; Great Western Reservoir is no longer used as a drinking-water source. Woman Creek drains the south portion of the site and before 1996 flowed into Standley Lake, which was a source of irrigation water for the area and supplies water for Westminster, Thornton, and Northglenn. In 1996, a reservoir was constructed upstream from Standley Lake to capture Woman Creek runoff and divert it away from Standley Lake.
Several series of detention ponds were constructed to manage plant wastes and surface-water runoff , including the A- and B-series Ponds along North and South Walnut Creeks and the C-series Ponds along Woman Creek. Past discharge of low-level contaminated wastes to both the A- and B-series Ponds resulted in the accumulation of plutonium and americium in pond sediments. Shallow groundwater refers to water within the alluvium and weathered bedrock geologic units and is found to a depth of 30 meters. Surface water and shallow groundwater are inextricably linked. Water from stream channels infiltrates downward, recharging the shallow groundwater, and the shallow groundwater recharges the stream and channels, depending on the time of year.
Beneath the alluvium is a highly impermeable bedrock layer that inhibits vertical flow. As a result, shallow groundwater flows laterally where it either discharges as baseflow into the streams or as hillslope springs and seeps. Approximately 200 to 300 meters below the surface lies the Fox Hills Sandstone, where the deep regional groundwater flows. Because of the intervening bedrock, this regional groundwater aquifer is hydraulically isolated from the Rocky Flats surface water and shallow groundwater and actinide contaminants.
The climate is temperate and semiarid, characteristic of Colorado’s Front Range. The average annual precipitation is approximately 14.5 inches, with about half occurring as rain and half as snow, and falls primarily as snow from late October through early April and as
|
|
A deer grazes at the edge of the B-4 Pond. One of the goals of remediation efforts at Rocky Flats was to maintain the wetlands and wildlife habitat. Special care had to be taken not to disturb the habitat of the “threatened” Preble’s meadow jumping mouse (inset), a short-grass prairie species that lives near the creeks and streams in the buffer zone around the Site.
|
