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4. SUMMARY OF FEASIBILITY STUDY The following sections summarize information from Site 47 RUFFS (Geosyntec, 2022) regarding screening of remedial technologies and evaluating a focused set of remedial alternatives in accordance with Remedial Investigation/Feasibility Study(RI/FS) Guidance (United States Environmental Protection Agency [USEPA], 1988). Additionally, the following sections describe the recommended remedial alternative and provide the basis for its selection as the final remedy for soil, and sediment at Site 47. 4.1 Technology Screening During the initial technology screening step, nine remedial technologies known to address COCs or COECs in soil and sediment were identified from DTSC guidance (DTSC, 2008). In accordance with USEPA RI/FS Guidance (USEPA, 1988), these nine technologies were screened based on their effectiveness, implementability, and cost. The results of the technology screening are presented in Table 6. 4.2 Identification of Alternatives for Soil, and Sediment, As shown in Table 6, retained technologies are fencing, land use restrictions, capping, excavation with off-site disposal, and excavation with on-site consolidation. The retained technologies were combined into four remedial alternatives, as well as a baseline"No Action" alternative, for further evaluation: • Alternative 1 —No Action; • Alternative 2—Existing Durable Cover, Fence, and Institutional Controls; • Alternative 3 —Excavation with On-Site Consolidation, Existing and New Durable Cover, and Institutional Controls; • Alternative 4—Excavation(to 2 feet) with Off-Site Disposal (Backfilled with Clean Fill), Existing Durable Cover, and Institutional Controls; and • Alternative 5 —Expanded Excavation with On-Site Consolidation, Existing Durable Cover, Expanded New Durable Cover, and Institutional Controls. The following sections briefly describe the remedial alternatives. 4.2.1 Alternative 1 —No Action The "No Action" alternative is required by the NCP and is used as a baseline for comparison with other alternatives. Under this alternative, Site 47 would remain in its current condition, and no containment, or removal would be implemented. No new institutional controls would be implemented, but the Pre-Decisional LUC would remain in effect. 4.2.2 Alternative 2—Existing Durable Cover, Fence, and Institutional Controls In this alternative, fencing and signs would be installed surrounding Site 47, as shown in Figure 12. The fence would restrict access to Site 47 for the general public and some ecological receptors (e.g., larger mammals), thereby reducing the potential for direct contact with Site 47 RAP for Soil 11 October 2023