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• The first and second areas would be bounded by McCloy Avenue to the north, Hooper Drive to the east,10 and the Project Sierra development area to the west; • The third area would be bounded by the railroad to the north, Port of Stockton Expressway to the east, and Daggett Road to the west; and • The fourth area would encompass the additional unpaved area bounded by McCloy Avenue to the north and the railroad to the south. The new covers would be tied into the existing pavement and structures where necessary. In the eastern end and to the west of the Port of Stockton Expressway, grading activities would also move COC/COEC-impacted soil away from existing paved areas/building foundations to facilitate the placement of 2 feet of clean cover soil in unpaved areas next to these features. The final surface of the new soil covers would be designed to slope at a slight grade to promote surface water drainage. In addition to the new covers, the Project Sierra development will modify existing drainage channels adjacent to Site 47. The existing drainage channel located along the southern boundary of Site 47 (central portion of lease property) will be filled with clean soil'1 during the grading process (Figure 16). Additionally, the drainage channel located outside the remedial boundary (southwestern corner of Project Sierra development area)will be modified to accommodate development, and a new drainage channel will be constructed along the northern boundary of Site 47 (south of McCloy Avenue) and be integrated into the Port's drainage system. The new and modified channels will be constructed in a similar manner as the stormwater detention ponds described previously (i.e., over-excavating COC/COEC-impacted soils and placing a minimum of 2 feet of clean fill within the remedial boundary). Upon completion of the Project Sierra development, the majority of COC/COEC-impacted soils will be located under concrete surfaces that will be less permeable than the existing unpaved surfaces. Outside of the Project Sierra development, COC/COEC-impacted soils will be covered in place with surfaces that have similar permeability to the existing conditions. Although reducing infiltration through COC/COEC-impacted soils is not necessary to achieve the RAOs, it is an important consideration for the future groundwater investigation at Site 47. As described in Section 2.3, a future groundwater monitoring program will evaluate groundwater data collected both prior to and after site development, and this data evaluation will be simpler if hydrologic conditions remain generally consistent. The planned stormwater detention basins within the Project Sierra development are the only areas where hydrologic conditions are expected to significantly change. Existing soil from these "To the east,the new cover would exclude localized areas east of Building 129 and north of Building 219 that are not included in the remedial boundary,and would exclude existing foundations and pavement at Buildings 128, 129, and 219. 11 "Clean soil"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 RUFFS). 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 16 October 2023