[en] This proposed plan identifies the preferred alternative for an interim remedial action plan for the 100-KR-4 Operable Unit at the Hanford Site. The alternative presented is to remove contaminated groundwater from the Unit, treat it by ion exchange, and then dispose of treated groundwater by using upgradient injection wells to return it to the acquifer. This will protect the Columbia River environment from toxic hexavalent chromium. This alternative is the initial recommendation of the EPA, Ecology, and the DOE. Public comment on this plan is invited