DOE/RL-2017-30, 52 pp, 2018

Cr(VI), a primary contaminant of concern at specific locations directly above the 100-KR-4 Groundwater Operable Unit on the Hanford Site, has affected groundwater in this operable unit as indicated by the presence of persistent plumes in groundwater associated with apparent historical release areas. To facilitate cleanup of this contamination, soil flushing is being evaluated to determine its feasibility as a remedial alternative component of ongoing and future remedial actions. This treatability test plan outlines the technical approach for conducting a soil flushing/infiltration study with the intent of accelerating groundwater cleanup of Cr(VI) at the 100-K West Area pump-and-treat (P&T) system. Within weeks following shutdown of the P&T system during a rebound study conducted between May 2016 and March 2017, Cr(VI) concentrations nearly tripled in several wells in the study area and later peaked at about 180 µg/L in the upper portion of the unconfined aquifer. This plan identifies an area of ~4,645 m² where the soil flushing/infiltration test will be conducted and details the planned test process. Results will be used to evaluate the feasibility of soil flushing/infiltration as a means of removing Cr(VI) mass from the vadose zone and capturing that mass by groundwater extraction. https://pdw.hanford.gov/arpir/index.cfm/viewDoc?accession=0065970H