The Chromium Groundwater Plume West of the 100-D/DR Reactors: Summary and Fiscal Year 1999 Update

High concentrations of chromium have been identified west of the 100-D/DR Reactors in the groundwater and in the porewater below the Columbia River. This ''hot spot'' of chromium contamination contains the highest known concentrations of chromium currently in groundwater on the Hanford Site. The contaminated groundwater and porewater are discharging into the Columbia River, where they may pose a risk to aquatic receptors. The purpose of this report is to provide (1) a summary of previous investigations describing the extent and source of the plume; (2) the analytical results of groundwater samples collected from the 12 FY 1999 wells; (3) a conceptual model of the geology, general hydrology, and chromium plume in the area west of the 100-D/DR Reactors; and (4) recommendations for future investigations, data collection, and groundwater sampling.