This Annual Site Environmental Report for 1998 describes the environmental conditions related to work performed for the Department of Energy (DOE) at Area IV of the Rocketdyne Santa Susana Field Laboratory (SSFL) and De Soto facilities. In the past, these operations included development, fabrication, and disassembly of nuclear reactors, reactor fuel, and other radioactive materials, under the Atomics International (AI) Division. Other activities included the operation of large-scale liquid metal facilities for testing of liquid metal fast breeder components at the Energy Technology Engineering Center (ETEC), a government-owned company-operated, test facility within Area IV. AI was merged into Rocketdyne in 1984 and many of the AI functions ...