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Record of Decision System (RODS)

HANFORD 200-AREA (USDOE)

Abstract

Site Name:  HANFORD 200-AREA (USDOE)
Address:  200 AREA 
City & State:  BENTON COUNTY  WA  99352
County:  BENTON
 
EPA ID:  WA1890090078
EPA Region:  10
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Amendment
ROD ID:  EPA/541/R-97/101
ROD Date:  09/25/1997
Operable Unit(s):  14
 
Media:  Air,Groundwater,Soil
 
Contaminant:  Radioactive, hazardous waste, asbestos, polychlorinated biphenyls (PCBs), heavy metals, volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), pesticides, inorganics.
 
Abstract:  The Hanford Site is a 560 square-mile area located along the Columbia River in southwestern Washington, situated north and west of the cities of Richland, Kennewick, and Pasco, an area commonly known as the Tri-Cities. The site currently known as the Hanford 200-Area is located near Richland, Washington. The land surround the Hanford Site is used primarily for agriculture and livestock grazing.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 the U.S. Department of Energy's (DOE's) facilities are located throughout the Site and the City of Richland. The land that Hanford now occupies was ceded to the U.S. Government in treaties with the Confederated Bands and Tribes of the Yakama Indian Nation and the Confederated Tribes of the Umatilla Indian Reservation in 1855. Certain portions of the Hanford Site are known to have cultural significance and may be eligible for listing in the National Register of Historic Places. Past activities released hazardous and radioactive substances to the environment that contaminated soil, air, and groundwater.The Hanford Site was listed on the National Priorities List (NPL) in July 1989.
 
Remedy:  The original remedy is comprised of the following major components: Initial construction and operation of two disposal cells that are expected to provide an approximate waste disposal capacity of 1.2 million square yards on the Central Plateau, southeast of the 200 West Area and southwest of the 200 East Area. The initial construction of the facility will require 165 acres of this area.The Environmental Restoration Disposal Facility (ERDF) will provide sufficient leachate storage capacity to ensure uninterrupted operations. Leachate collected at the landfill will be managed at the 200 Area Effluent Treatment Facility.Surface water run-on/run-off will be controlled at the landfill and other areas of the facility that are potentially contaminated. Best management practices to control runoff shall be employed.During excavation, suitable soils will be stockpiled at the ERDF site to provide materials for liner systems and for daily interim and closure covers for the landfill. Materials not suitable for construction of the liner and covers will be used for other construction purposes at the Hanford Site to the extent practicable.Air monitoring will be accomplished by placement at ERDF of real-time air monitors for radioactive contaminants and air samplers for hazardous and radioactive constituents to detect any off site migration of contaminants. Groundwater monitoring will also occur.The ERDF landfill will be closed by placing a modified closure cover over the waste. The cover will prevent direct exposure to the waste and includes a vegetated surface layer of fine-grained soils to retain moisture and encourage evapotranspiration, thereby mining infiltration and vadose zone transport of contaminants to groundwater. The upper 50 cm (20 in.) of the soil cover system is composed of an admixture of silt and gravels. This layer is intended to both reduce infiltration through the cover and enhance the resistance of the cover to burrowing animals and long-term wind erosion. The cover will be modified by providing a total of approximately 15 feet of soil to deter intrusion. It is anticipated that additional research into closure covers may result in site specific enhancements to designs. Prior to cover construction, closure cover designs will be evaluated and the most appropriate closure cover design will be selected for construction. Construction of the cover will occur on an incremental basis, as the trench is expanded. Basalt from Hanford Site borrow pits will not be required for construction of the ERDF closure cover.A decontamination facility will be constructed consisting of, at a minimum, an impervious pad with sump, wash water storage, and secondary containment. Washwater used to decontaminate site equipment shall be managed in compliance with appropriate requirements.The amended remedy authorizes the following: ERDF Expansion - two additional ERDF cells to be constructed and operated for disposal of Hanford Site remediation waste and the design phase shall also include an evaluation of vadose zone monitoring.Treatment at ERDF - the option of conducting remediation waste treatment in containers at ERDF instead of the operable unit, prior to disposal; this option does not preclude treatment at the operable units.
 
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