Performed at the site after a site is listed on the National Priorities List (NPL). The RI serves as the mechanism for collecting data. The FS is the mechanism for the development, screening and detailed evaluation of alternative remedial actions. The RI and FS are conducted concurrently; data collected in the RI influence the development of remedial alternatives in the FS, which in turn affects the data needs and scope of treatability studies and additional field investigations.