SR2400516 - Laserfiche WebLink

Home Browse Search

contaminated soils. Warning signs would also be mounted directly on the fencing to deter the general public from entering Site 47. Future land use and activities within the area requiring institutional controls (ARIC, Figure 11) would be restricted by a LUC. In addition, the existing covers would be retained near the eastern boundary of Site 47 and within the paved warehouse area west of Site 47. The existing covers and fencing would be inspected and maintained regularly, and ICs would be implemented as discussed in Sections 6 and 7. 4.2.3 Alternative 3—Excavation with On-Site Consolidation, Existing and New Durable Cover, and Institutional Controls In Alternative 3, new soil or asphalt covers would be installed over the majority of Site 47, and the existing covers (i.e., building foundations and paved areas) would be repaired, as needed, to serve as a physical barrier(Figure 13). The new soil cover would consist of a demarcation layer and a minimum of 2 feet of cleans soil (borrow fill) at the ground surface. Prior to installing the new soil cover, two areas south of Site 47 (Figure 13) would be excavated and consolidated under the cover. Following excavation, these two areas would be backfilled with clean, imported soil. The existing and new covers would be inspected and maintained regularly, and future land use and activities within the ARIC (Figure 11) would be restricted by a LUC. 4.2.4 Alternative 4—Excavation (to 2 feet)with Off-Site Disposal (Backfilled with Clean Fill),Existing Durable Cover, and Institutional Controls In Alternative 4, soil over the majority of Site 47 would be excavated to a depth of 2 feet and disposed of at a permitted off-site landfill following the appropriate waste characterization. The excavation would be backfilled with clean soil that meets the remediation goals and graded to match the surrounding topography. Similar to Alternative 3, the existing covers (i.e., building foundations and paved areas)would be repaired, as needed, to serve as a physical barrier, and new asphalt covers would be installed in select areas (Figure 14). The existing and new covers would be inspected and maintained regularly, and future land use and activities within the ARIC (Figure 11)would be restricted by a LUC. 4.2.5 Alternative 5—Expanded Excavation with On-Site Consolidation,Existing Durable Cover, Expanded New Durable Cover, and Institutional Controls Alternative 5 involves installation of a durable cover that is integrated with and supports the Project Sierra development. The elements of the durable cover within the Project Sierra development would consist of a demarcation layer4, cleans imported fill, and the finished surfaces depicted on Figure 15 (e.g., concrete foundation at Warehouse and Outdoor Storage 4 The demarcation layer is assumed to consist of a thin geosynthetic material placed between the existing soil and the new soil cover.Alternate materials for the demarcation layer,if preferred by the developer,would be proposed in the RDIPs for specific approval by the State. 5"Clean"is defined as soil meeting the remediation goals or other risk-based screening levels for commercial and industrial exposure(see Appendix F,Table F-1 of Final RI/FFS). Chemical acceptance criteria may be updated in the RDIPs to reflect current DTSC or USEPA guidance.For excavations below the groundwater table(e.g.,bottom of drainage channels),clean soil may be replaced with rock(e.g.,3-inch minus aggregate mined from a quarry)to bridge the saturated soil;rock mined from a quarry would not be subject to chemical testing. Site 47 RAP for Soil 12 October 2023