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Ms. Vera Fischer Page 3 of 5 Prior to collecting groundwater samples, a Ground Zero technician will measure and record the static water level and develop the new well by pumping and surging until turbidity is minimized. At least 48 hours following well development the well will be purged and sampled. Groundwater samples will be collected from the well after a minimum of three casing volumes have been purged, pH, temperature, and electrical conductivity parameters have stabilized, and water has recharged to at least 80% of the static level. The samples will be dispensed into the appropriate containers, sealed, labeled, and placed in an ice chest chilled to a temperature of approximately 4°C for shipment to a state-certified laboratory under chain of custody protocol. Groundwater will be analyzed for TPHg, TPHd, BTEX, fuel oxygenates and lead scavengers by EPA Methods 8015 and 8260. Soil Gas Sampling Three (3) temporary soil gas sampling probes will be installed onsite at the approximate locations shown on Figure 2. The temporary soil gas 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 (DTSC and RWQCB, July 2015). Prior to drilling, the appropriate drilling permits will be obtained from the San Joaquin County EHD. The proposed drilling locations will be marked and cleared for underground utilities by Underground Service Alert and a private utility location service. At each of the locations, C-57 licensed TEG Northern California (TEG) of Rancho Cordova, California will advance direct-push sample rods to depths of 5 or 6 feet below ground surface (bgs). TEG will construct temporary soil gas probes in the borings using Nylaflow tubing and nylon screen. The screens will be placed at depths of approximately 5 feet in the middle of a one-foot thick sand filter pack. The filter pack will be overlain with six inches - one foot of bentonite chips followed by hydrated bentonite to the ground surface. Prior to purging and sampling, the wells will be allowed to sit for at least two hours to equilibrate. Shut-in tests will be performed to ensure that no leaks are present in the sample train. The wells will then be purged of three void volumes (tubing and sandpack) and sampled using 400 milliliter Summa canisters at a flow rate between 100 — 200 ml/minute and at a vacuum of less than 100 inches of water column. During the collection of each soil vapor sample a leak detection test will be conducted to ensure there is no intrusion of ambient air into each respective vapor sample. During the collection of each vapor sample 1,1-difluoroethane (DFA) will be applied within a shroud placed directly around the rod/surface interface and all associated connections. Following the completion of sample collection, the borings will be destroyed according to EHD standards and the paved surfaces restored. Stallworth Workplan Text