Record of Decision System (RODS)
HANFORD 200-AREA (USDOE)
|Site Name:||HANFORD 200-AREA (USDOE)|
|City & State:||BENTON COUNTY WA 99352|
|NPL Status:||Currently on the Final NPL|
|ROD Type:||Record of Decision|
|Contaminant:||Carbon tetrachloride, plutonium, chloroform, TCE|
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 Hanford 200-Area is a 1,450-square kilometer (560 square miles) federal facility located along the Columbia River in southeastern Washington. The 200-Area is situated north and west of the cities of Richland, Kennewick, and Pasco, an area commonly known as the Tri-Cities. The 200-Area is located in the central portion of the Hanford Site, and covers less than 40-square kilometers (15 square miles). The 200-ZP-1 Operable Unit (OU) is located in the 200 West Area of the 200-Area NPL site. Contamination to the groundwater in the 200-ZP-1 Area resulted from historic discharges from the Plutonium Finishing Plant.
The land surrounding the Hanford Site is used primarily for agriculture and livestock grazing. The major population center near the Hanford Site is the Tri-Cities, with a combined population of approximately 100,000.
The land is semi-arid with a sparse covering of cold desert shrubs and drought resistant grasses. Forty percent of the area's annual six and one quarter inches of rain occurs between November and January. In part due to the semi-arid conditions, no wetlands are contained within the boundary of 200-ZP-1.
The Columbia River is located approximately ten miles east of the 200 West Area. The 200 West Area is not within the 100 year floodplain of the river.
The Hanford Site was established during World War II as part of the Army's "Manhattan Project" to produce plutonium for nuclear weapons. Hanford Site operations began in 1943, and DOE facilities are located throughout the Site and the City of Richland. The land occupied by the Hanford Site was ceded to the United States by various Native American tribes in treaties signed in 1855. The treaties reserve certain rights to fisheries and to the use of open and unclaimed land. Certain portions of the Site are known to have cultural significance and may be eligible for listing in the National Register of Historical Places.
In 1988, the Hanford Site was added to the National Priorities List (NPL) in July 1989 as four sites (the 1100 Area, the 200 Area, the 300 Area, and the 100 Area). Each of these areas was further divided into operable units (a grouping of individual waste units based primarily on geographic area and common waste sources).
In anticipation of the NPL listing, DOE, and EPA entered into a Federal Facility Agreement in May 1989. This agreement established a procedural framework and schedule for developing, implementing, and monitoring remedial response actions at the Hanford Site. The agreement also addresses Resource Conservation and Recovery Act (RCRA) compliance and permitting.
The 200-ZP-1 operable unit is one of two groundwater operable units located in the 200 West Area. Contamination in the 200-ZP-1 operable unit resulted from historic discharges to three primary liquid waste disposal sites. These sites are the 216-Z-9 trench, the 216-Z-1A tile field, and the 216-Z-18 crib. The predominant contaminants in the waste stream were carbon tetrachloride and plutonium. Monitoring data indicates that almost all of the plutonium has bound to the soil column and little has reached the groundwater. It is estimated that 600 to 1,000 metric tons of carbon tetrachloride was discharged to the soil from 1955 to 1973.
In 1991 a CERCLA removal action was initiated utilizing vapor extraction systems to remove the carbon tetrachloride from the vadose zone and prevent further migration to the groundwater. To date, over 45,360 kilograms (100,000 pounds) of carbon tetrachloride have been removed from the soil column. It is anticipated that the removal action and this groundwater interim remedial action will continue until at least the year 2000.
This Interim Remedial Measure addresses the carbon tetrachloride dissolved in the groundwater, and assists in identifying the location of the unaccounted carbon tetrachloride disposed in the 200 West Area.
The selected remedy uses groundwater pump and treat and is intended to minimize further migration of carbon tetrachloride, chloroform, and trichloroethylene (TCE) into the groundwater of the 200 West Area. To do this, the IRM is designed to stabilize and reduce contaminant mass in the high concentration portion of the plume. The high concentration portion of the plume corresponds to the area within the 2000 - 3000 parts per billion (ppb) contour of carbon tetrachloride. Pilot scale operations are underway to determine the effectiveness of the system. Initial results indicate that expansion of the system is warranted. The degree of expansion will be based on the amount of groundwater extraction and treated water reinjection that is deemed feasible and necessary to contain the high concentration area. It is estimated that the initial expansion (Phase II) will upgrade the total pump and treat capacity to about 570 liters per minute (150 gallons per minute). Up to three new wells may need to be installed to support scale-up to 570 liters per minute (150 gallons per minute). This system will be operated to continue gathering data on the effects of pump and treat on plume containment and mass removal. A final expansion (Phase III) will be initiated in fiscal year 1998, resulting in a pumping rate in the range of 570 to 1900 liters per minutes (150 to 500 gallons per minute) in order to meet the objectives of mass removal and plume containment. Initial estimates show that up to 19 new wells may need to be installed to support full-scale pumping operations. Pump-and-treat operations would continue until selection of a final remedy, or until such time that DOE demonstrates to EPA that no further interim pump and treatment operations would be required to protect human health and the environment. The actual time required will be determined as the interim action progresses. It is anticipated that this action, if successful, would continue until at least the year 2000.
Monitoring will be performed throughout the interim action activities. Additional information will be collected to support the expansion on an as-needed basis.
The treatment train for the Phase II (treatment system upgraded to 570 liters per minute (150 gallons per minute)) and Phase III (treatment system upgraded up to 1,900 liters per minute (500 gallons per minute)) of this interim remedial measure is air stripping with vapor phase activated carbon used to capture stripped contaminants. The treated groundwater will be reinjected into the aquifer through wells located within the area of contamination.
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