FY2003 ANNUAL SUMMARY REPORT FOR THE IN SITU REDOX MANIPULATION OPERATIONS

This annual progress and performance report discusses the In Situ Redox (reduction-oxidation) Manipulation (ISRM) interim medial action at the 100-HR-3 Operable Unit (OU) from October 1, 2002, through September 30, 2003 (FY 2003). This report specifically addresses remedial actions performed at the hexavalent chromium plume in the southwest portion of the 100-D Area. Interim pump-and-treat remedial actions performed at the northeast portion of the 100-D and 100-H Area will be discussed in a separate annual summary report. This is the fourth annual summary report that specifically addresses the ISRM remediation technology presently being installed in this portion of the 100-D Area, as specified in Remedial Design Report and Remedial Action Work Plan for the 100-HR-3 Groundwater Operable Unit In Situ Redox Manipulation (RDR/RAWP) (DOE-RL 2000). The ISRM technology involves creating a permeable subsurface treatment zone by injecting sodium dithionite into the aquifer, which creates a chemically reduced environment. Hexavalent chromium passing through the treatment zone is reduced to less toxic and less mobile trivalent chromium.