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5 May 30, 2018 Page 3 of 7 Reference: Data Gap Assessment Report, Former Chase Chevrolet, 424 North Van Buren Street, Stockton, California ASSESSMENT ACTIVITIES Soil Boring Advancement - Stantec oversaw Cascade Drilling (a California C-57 licensed driller) during advancement of boreholes SB-1 and SB-2 to a depth of 20 feet below ground surface (ft bgs) using direct push drilling equipment. Borehole logs are included in Attachment B. The upper five feet of each borehole was advanced using a hand auger to confirm the absence of shallow subsurface utilities or obstructions. Following collection of soil and groundwater samples, soil borings were abandoned by introducing neat cement grout into the borehole through a tremie pipe and completing the surface with concrete to match existing grade. Borehole abandonment activities were witnessed by a SJCEHD inspector. Soil Vapor Well Installation - Soil vapor probes SV-1, SV-2, and SV-3 were installed using a nominal 3-inch- diameter hand auger in accordance with procedures described in the Work Plan. Hand auger boreholes were advanced within the unoccupied retail space on the north side of the parking garage (see Figure 2). Boreholes were advanced to 5 ft bgs, and a five-inch vapor probe was installed within a one-foot sandpack interval installed between 4 and 5 ft bgs. The vapor probe implant was attached to a 7-foot length of 0.25-inch diameter Nylaflow® tubing and a Swagelok&style valve was attached at the opposite end. A well box was set in concrete on the unpaved surface. Well construction details are illustrated on soil boring logs included in Attachment B. Soil and Grab Groundwater Sample Collection - Soil samples from each boring were collected for examination of soil stratigraphy, qualitative analysis for the presence of residual hydrocarbons (i.e. field screened using a photoionization detector [PID]), and laboratory analysis. Soils encountered within the borehole were described in accordance with the Unified Soil Classification System (USCS). Soil samples from the vapor probe borings were collected into brass sleeves at a depth of 5 ft bgs using an AMS core sampler. Soil samples from soil borings SB-1 and SB-2 were collected at depths of 5, 10, 15, and 20 feet bgs and retained for analyses by cutting the acetate core barrel liner sleeves and capping the ends with Teflon tape and plastic end caps. Upon reaching total depth in SB-1 and SB-2, the direct push tool string was removed and a temporary well screen was inserted into the borehole. Groundwater samples were collected into laboratory- supplied glassware using a new, disposable bailer for each location. Soil and groundwater samples were labeled, placed on ice in an insulated container, and delivered under chain-of-custody (COC) protocol to TestAmerica for chemical analysis. Design with community in mind