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SUPPLEMENTAL SITE INVESTIGATION WORK PLAN South Pointe Property Stockton, California Conceptual Site Model place. This position is supported by historical sampling at the site that has documented extensive, dispersed concentrations of site COCs in soils, generally not indicative of chemicals source areas. Two additional features of note were identified northeast of the site. This area was historically part of the South Pointe property but was separated from the site during remedial operations associated with development of the Promenade public walkway feature that now encircles the South Pointe property. A 'natural gas well and holder' (1895), 'chemical cart' (1950), and 'gas and oil' structure (1950) were identified within close proximity to each other. A 'fertilizer mixing area' was identified on the 1950 Sanborn map, located immediately east of the current site. The historical locations of these features are illustrated on Figure 2. 3.2 GROUNDWATER CONDITIONS As documented in the Phase I ESA, the site and surrounding vicinity have been subject to a variety of industrial uses dating to the late 1800s. Adjacent properties to the south were historically used for bulk storage of petroleum hydrocarbons which were pumped to and from vessels in the Stockton channel via a network of pipelines historically located east of the site. Fuel hydrocarbons and related compounds are documented to have impacted groundwater in the area, and groundwater remediation and/or monitoring activities are ongoing at several nearby sites. Two groundwater monitoring wells (MW-34 and MW-35) are currently present in the northeast corner of the site, part of the well network associated with the L&M Operable Unit Project at Parcel 2A, located immediately across Weber Avenue to the southeast. The well locations are illustrated on Figure 2. Chevron Environmental Management Company and Phillips 66 Company are the responsible parties associated with the L&M site. MW-34 is an 'A' zone well screened between 15 and 30 feet below grade, and well MW-35 is a 'B' zone well screened between 48 and 53 feet below grade. According to the Semiannual Groundwater Monitoring Report, First Half 2022 (Trihydro, 2022), these wells are sampled annually for petroleum hydrocarbons. MW-34 was 'non detect' in July 2021 and reported 330 micrograms per liter (pg/1) motor oil in July 2020. Similarly, well MW-35 was 'non detect' in July 2021 and reported 460 pg/I motor oil in July 2020. Based on these data, wells MW-34 and -35 appear to monitor the western edge of the Parcel 2A plume, and document minimal impacts to groundwater from petroleum hydrocarbons in this portion of the site. The L&M site's regulatory case can be reviewed on the Geotracker website (httl2s://aeotracker.waterboards.ca.aov/12rofile report.asp?global id=SL0002050099). 3.3 SOIL VAPOR CONDITIONS The December 2021 Phase II Environmental Assessment Report (Stantec, 2022) included assessment of soil vapor using passive and active methods to 1) identify areas of accumulated chemical mass in soil vapor representative of historical source areas, and 2) to quantify concentrations of VOCs in soil vapor to assess potential human health risk posed to future site occupants from vapor intrusion.The passive assessment, using sorbent sampling modules, 3.2