Under a proposed fourth amended consent decree concerning the Asarco Tacoma Smelter and Sediments/Groundwater Operable Units of the Commencement Bay Nearshore/Tideflats Superfund site in Tacoma, Washington, certain remedial action deadlines set forth in construction management plans are extended for six months and certain payments due under the third amended consent decree are extinguished in exchange for the disposition of contaminated soil from an adjacent parcel.