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Drilling Work Plan Project No.: 1086 August 29,2019 vacuum less than 100 inches of water column. If so, then the vapor wells will be screened at that depth. If not, consecutive flow tests will be performed at 1-foot depth intervals until satisfactory yield can be obtained. The driller will ensure that the soil from the boring has been removed to a depth of 6 feet below ground surface (bgs). A 5-inch thick layer of Monterey #3 sand will be placed in the borehole and a stainless-steel vapor probe tip attached to a length of Teflon or Nylaflow® tubing will be lowered to the top of the sand at approximately 5.5 feet bgs and 5 feet below the base of the building foundation. The Teflon or Nylaflow® tubing will be held in place by a section of PVC pipe. Once the probe is centered in the borehole, approximately 7-inches of sand will be placed into the borehole completing a 1-foot filter pack with the probe in the center. A 1.5-foot thick layer of dry granular bentonite will be placed above the filter pack, with a 2- foot thick hydrated bentonite layer above. The remaining annulus will be filled with bentonite grout. The PVC pipe used to center the probe tip and tubing will be slowly removed as the borehole is completed. The well will be completed by connecting a gas tight check valve on the tubing and installing a well box at the surface. A schematic of the soil vapor well is shown on Figure 4. B. Work Plan Activities—Shallow Soil Sampling In order to investigate the current magnitude of shallow soil contamination and the potential risk of direct soil contact and outdoor air exposure, Ground Zero will install eight (8) soil borings. Each boring will be advanced in the vicinity of the former UST pits and the dispenser island(as requested by RWQCB) at the approximate locations shown on Figure 3. Soil Sample Collection The borings will be advanced to a maximum depth of approximately 8 feet below grade using direct-push drill rig operated by C57 licensed driller. Soil samples will be collected at approximately 4 and 8 feet bgs. Soil type will be described in accordance with the Unified Soil Classification System (USCS) and the samples will be field-screened for contamination with a photoionization detector (PID). Soil samples designated for laboratory analysis will be cut from the acetate liner, capped with Teflon tape and immediately placed on ice to be kept below 6 degrees Celcius. After sampling, the boreholes will be backfilled to grade with neat cement and capped with concrete or soil in accordance with SJCEHD requirements. C. Work Plan Activities—Further Groundwater Assessment In order to further assess the lateral and vertical extent of the groundwater contaminant plume to the north and east of the Site, Ground Zero will install sixteen direct-push borings, four at each location, as shown on Figure 3 using a CPT rig equipped for the collection of discrete groundwater samples at various depths per borehole while limiting cross- contamination between zones. The location of the borings is shown on Figure 3 and described below: • Four borings will be installed approximately 100 feet north of the up-gradient edge of the former UST pit (source) and beyond the expected edge of the plume;