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Mr. Buehler February 9, 2024 Page 3 of 7 SCOPE OF WORK The scope of work proposed in the following sections was developed to further investigate downgradient groundwater and soil vapor intrusion concerns at the Site and evaluate the Site for closure under the LTCP. Groundwater - The Site currently has seven groundwater monitoring wells, but these wells have not had sufficient water to sample since 2019. This Work Plan proposes installation of monitoring wells at depths sufficient to monitor the current groundwater level beneath the Site. This scope of work includes the following: • Installation and development of three groundwater monitoring wells (MW-1 D, MW-61D, & MW-71D), screened from 100 to 120 feet below ground surface (bgs); and • Collection of groundwater samples from the existing monitoring wells (MW-1 through MW- 7, if sufficient water is present) and the newly installed monitoring wells (MW-1 D, MW-61D, & MW-7D). Soil Vapor Intrusion - The intermediate subsurface soils (--30 to - 80 feet bgs) are currently being treated by the SVE treatment system. To date, shallow soil impacts have not been characterized. Therefore,this Work Plan proposes soil vapor probes installation on-Site to evaluate the risk to vapor intrusion in the vicinity of the former UST and former dispenser island. This scope of work includes the following: • Installation and sampling of three on-Site soil vapor probes (SVP-1 through SVP-3). Figure 2 illustrates the proposed groundwater monitoring well and soil vapor probe locations. PREFIELD ACTIVITIES Prior to initiating field work, Citadel will perform the following pre-field activities: • Approval of this Work Plan will be obtained from the RWQCB; • The Site-specific health and safety plan (HASP) will be updated; • Boring permits will be obtained from the SJCEHD; • Encroachment permits will be obtained from the County and Cal Trans; • The proposed boring locations will be marked with white paint and Underground Service Alert of Northern California (USA) will be notified at least 48 hours prior to drilling to mark underground utilities in the proposed drilling area; • A private utility locator will be retained to clear the proposed drilling locations of underground utilities and other possible subsurface obstructions; and • The SJCEHD, RWQCB, and other necessary parties will be notified of proposed field activities at least three days prior to initiating field work. INSTALLATION AND SAMPLING OF GROUNDWATER MONITORING WELLS Three off-Site groundwater monitoring wells (MW-1 D, MW-61D, and MW-71D) will be installed at the approximate locations shown on Figure 2. The wells will be completed to a depth of approximately 120 feet below ground surface (bgs) by a C-57 licensed drilling contractor using hollow-stem auger drilling techniques. As a precautionary safety measure to prevent damage to subsurface utilities, the borehole will be cleared with a hand auger to approximately 5 feet bgs.