Site Name: US DOE SAVANNAH RIVER SITE (Unit 35)

EPA ID: SC1890008989 EPA Region: 04 Metro Statistical Area: 0600

BETWEEN SC 125 & US 278, AIKEN, SC 29802

Operable Unit: 35

ROD ID: EPA/ROD/R04-95/215 ROD Date: 02/13/95

Contaminant: cesium-137

Keys: plutonium, groundwater, surface water, sediments, reactor

Abstract:

Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

The Savannah River Site (SRS) occupies approximately 300 square miles of land adjacent to the Savannah River, principally in Aiken and Barnwell Counties of South Carolina. SRS is a secured U.S. government facility with no permanent residents. The site is located approximately 25 miles southeast of Augusta, Georgia, and 20 miles south of Aiken, South Carolina. The population within a 50-mile radius of SRS is 635,000 people.

SRS is owned by the U.S. Department of Energy (DOE). Management and operating services are provided by Westinghouse Savannah River Company (WSRC). SRS has historically produced tritium, plutonium, and other special nuclear materials for national defense. SRS has also provided nuclear materials for the space program and for medical, industrial, and research efforts. Chemical and radioactive wastes are by-products of nuclear material production processes. Hazardous substances are currently present in the environment at SRS. The Par Pond Unit consists of the Par Pond Reservoir, the series of pre-cooler ponds and canals, and Lower Three Runs Creek. For the purposes of this interim action, the operable unit addressed consists of the approximately 1,340 acres of sediments at the periphery of the Par Pond Reservoir that were exposed as a result of the drawdown of the reservoir from 200 ft to 191 ft mean sea level (msl).

Par Pond is a 2,640-acre man-made reservoir located northeast of P Area and east of R Area in the eastern portion of SRS. Par Pond was created in 1958 by constructing an earthen dam across Lower Three Runs Creek. The three main arms of the reservoir follow the uppermost portion of Lower Three Runs Creek and its former tributaries. Prior to drawdown, the elevation of Par Pond was 200 ft msl. The current elevation after drawdown is 181 ft msl.

The easternmost shore of Par Pond lies one and a half miles from the eastern SRS boundary. The southern shore of the reservoir lies approximately 200 ft north of Road B. Par Pond discharges through controlled releases into Lower Three Runs Creek, which in turn discharges into the Savannah River. The length of Lower Three Runs Creek from the outfall of Par Pond to the Savannah River is approximately 20 miles.

Par Pond was built to augment the cooling water requirements of both P and R Reactors. R Reactor began operations in 1953. Prior to construction of Par Pond, R Reactor received cooling water directly from the Savannah River and discharged cooling water directly into Lower Three Runs Creek in an area that is now the Hot Arm of Par Pond. P Reactor began operations in 1954. Prior to construction of Par Pond, P Reactor received cooling water directly from the Savannah River and discharged cooling water directly into Steel Creek.

During the late 1950s, an effluent pathway was constructed from R Reactor to Par Pond. The pathway consisted of the R Canal and Pond B. This effluent pathway was used for R Reactor discharge from 1961 until the reactor was shut down in 1964. Since the shutdown of R Reactor in 1964, R Canal and Pond B have remained mostly undisturbed. Par Pond also served as a heat exchange/cooling reservoir for P Reactor until 1988. Heated water from P Reactor was released through a series of manmade canals and smaller impoundments into the pre-cooler Pond C. The effluent from Pond C passed through a concrete culvert below an earthen dam and was funneled by gravity into the Hot Arm of Par Pond.

Releases in the form of process leaks, purges, and makeup cooling water have contaminated Par Pond with cesium-137 and other radioactive and nonradioactive contaminants. Between 1954 and 1964, approximately 222 curies of cesium-137 were released from R Reactor into Par Pond or Lower Three Runs Creek. All radioactive isotope releases ceased following the shutdown of R Reactor in 1964. No measurable cesium-137 was released into Par Pond from P Reactor. Concentrations of radioactive isotopes in Par Pond have decreased due to the cessation of reactor releases, decay of the isotopes, dilution from groundwater seepage, and seepage losses from the basin. Since most of the radionuclide releases to Par Pond (directly or indirectly) occurred during the 1950 to 1960 era, and the half has decayed. The current estimated inventory of cesium-137 associated with all sediments within the Par Pond reservoir is approximately 43 Ci, of which 9 Ci are present in the 1,340 acres of exposed sediments. The remaining 68 Ci of cesium-

Remedy:

The preferred interim alternative consists of refilling and maintaining Par Pond to the original 200-ft level following repair of the Par Pond Dam. Based on comments on the Interim Action Proposed Plan for the operable unit, the preferred alternative has been modified to include maintenance of the reservoir at the 200 can be accomplished of the environmental impacts from reduced flow to Lower Three Runs Creek (the creek below Par Pond Dam), fluctuating reservoir water level, and the discontinuance of providing river water through pumping, to the reservoir.

The preferred alternative is an interim action. A final action will be evaluate following implementation of the preferred interim action alternative according to the FFA schedule. The interim action provides the most timely reduction of risk to human health and the environment through submergence of the sediments with a layer of water upon restoration of the Par Pond water level. The water layer would attenuate gamma radiation emitted from the decay of cesium-137 and minimize the potential for sediments to become airborne. Also, of significance to the environment, the interim action would allow for a gradual recovery of the reservoir to essentially pre-drawdown ecological conditions.