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Drilling Work Plan Project No.: 1086 August 29,2019 Plan (Addendum Work Plan) were submitted to the RWQCB to address their request for further site assessment. Note: Both Work Plans are available on Geotracker or Ground Zero can email a copy, if desired. On June 28, 2019, the RWQCB issued an approval letter of the May 1, 2019 Addendum Work Plan; a copy is provided in Attachment A. In order to determine the presence of shallow soil and soil vapor contamination at the Site and collect groundwater samples to the north and east of the Site, Ground Zero will perform the following work. Pre field Work and Permitting Activities All fieldwork will be conducted in accordance with the attached Quality Assurance/Quality Control Plan (Attachment B) and Health & Safety Plan (Attachment C). Investigation derived wastes (drill cuttings and decon/purge water) will be drummed and properly disposed of. Drilling permits will be obtained from San Joaquin County Environmental Health Department (SJCEHD) and the City of Stockton Public Work Department for the encroachment of right-of- way drilling. Underground utilities will be checked by clearly marking the boring locations in white paint and calling the location in for a clearance ticket by Underground Services Alert (USA). Refer to Figure 3 for location of borings. A. Work Plan Activities-Soil Vapor Sampling In order to determine the extent and magnitude of the current vapor content in the shallow vadose zone beneath the Site, Ground Zero will install five (5) permanent soil vapor monitoring wells in the following locations: • One in between the current building and the former dispenser island, as requested by RWQCB. • One in the vicinity of the former fuel USTs along the north side of the current building; • One between the former waste oil UST and the east wall of the current building; • One near the leading edge of the shallow groundwater plume near MW-9 and; • One near the down-gradient edge of the plume near MW-5 and the eastern boundary of the Olivarez property. The vapor sampling locations address the potential vapor intrusion risk of the existing building, in the vicinity of the groundwater contaminant plume core and along the eastern property boundary. The source of the shallow soil contamination (former USTs), the fuel dispenser and the vapor sampling locations are shown in Figure 3. The soil vapor sampling points will be installed in general accordance with the DTSC and RWQCB guidelines set forth in the California Environmental Protection Agency's Advisory —Active Soil Gas Investigations (CalEPA Advisory) dated July 2015. A C-57 licensed contractor will advance direct-push sample rods to a depth of 6 feet, which is approximately 5 feet below the building foundation. A vapor flow test will be performed to determine if the soil can yield vapor flow at a rate of 100— 200 milliliters per minute at a