The Santa Susana Field Laboratory (SSFL) is located 30 miles northwest of downtown Los Angeles in southeastern Ventura County, near the crest of the Simi Hills at the western border of the San Fernando Valley. A former rocket engine test and nuclear research facility, the 2,849-acre field laboratory is currently the focus of a comprehensive environmental investigation and cleanup program, conducted by Boeing, the United States Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA), and overseen by the Department of Toxic Substances Control.