Soil washing: A preliminary assessment of its applicability to Hanford

Soil washing is being considered for treating soils at the US Department of Energy's (DOE) Hanford Site. As a result of over 50 years of operations to produce plutonium for the US Department of Defense and research for DOE, soils in areas within the Site are contaminated with hazardous wastes and radionuclides. In the soil washing process, contaminated soil is mixed with a liquid and then physically and/or chemically treated to dissolve the contaminants into solution and/or concentrate them in a small fraction of the soil. The purpose of this procedure is to separate the contaminants from the bulk of the soil. The key to successful application is to match the types of contaminants and soil characteristics with physical-chemical methods that perform well under the existing conditions. The applicability of soil washing to Hanford Site contaminated soils must take into account both the characteristics of the oil and the type of contamination. Hanford soils typically contain up to 90% sand, gravel, and cobbles, which generally are favorable characteristics for soil washing. For example, in soil samples from the north pond in the 300 Area, 80% to 90% of the soil particles were larger than 250 {mu}m. The principal contaminants in the soil are radionuclides, heavy metals, and nitrate and sulfate salts. For most of the sites, organic contaminants are either not present or are found in very low concentration. 28 refs., 5 figs., 10 tabs