NGWA Event and Education Recordings Archive

The Hanford Site encompasses approximately 586 square miles in southeast Washington State.  It is located in the Lower Columbia Basin with the Columbia River forming the northern and eastern boundaries. Waste management associated with plutonium production had been a major activity from 1943 throughout the 1980s, with the most hazardous waste associated with underground storage tanks. During operations, irradiated fuel reprocessing, isotope recovery, and associated waste management activities occurred on the Central Plateau. From unlined cribs, trenches, and ponds, and leakage from underground storage tanks, groundwater contaminant plumes of tritium, iodine-129, and nitrate formed when the waste discharged to ponds and cribs reached the aquifer. These contaminants form regional plumes originating on the Central Plateau. Although some of these plumes have shrunk in size over the years, these plumes still cover 75 percent of the Central Plateau.  One of these plumes is expanding at the edges, but the high-concentration core is contained by a pump-and-treat system. The remediation system was being enlarged in 2012 to capture more of the contamination. Other groundwater contaminants in the Central Plateau include technetium-99, uranium, strontium-90, trichloroethene, chromium and cyanide. Groundwater flows from upland areas in the west eastward to the Columbia River. Some contaminants (inorganics and radionuclides) have reached the Columbia River by moving downward through the vadose zone, into the groundwater, and then laterally to the Columbia River.

To manage the Hanford Site groundwater cleanup and protect the Columbia River, waste sites are grouped within geographic areas known as operable units.  With 11 operable units at the Hanford site, the primary focus of this presentation is the four major groundwater operable units on the Central Plateau.  The groundwater strategy for the Central Plateau focuses on groundwater protection, monitoring and remediation using innovative pump-and-treat systems and deep vadose zone remediation through desiccation.