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Geosyntec° <br /> consultants <br /> 3. INVESTIGATION WORK PLAN <br /> 3.1 Pre-field Activities <br /> Geosyntec will follow the same pre-field activities described in the Final UST Work Plan, <br /> including making appropriate notifications, obtaining Site access, and obtaining the required <br /> drilling permits. A task hazard analysis has been included in Appendix D. <br /> 3.2 Field Activities <br /> As described in the Final UST Work Plan, prior to drilling, Geosyntec will locate boring <br /> locations with a handheld differential global positioning system, mark locations with white paint, <br /> contact Underground Service Alert(USA), and perform a private utility survey in the vicinity. <br /> 3.2.1 Drilling and Sampling <br /> Geosyntec will contract with a California-licensed C-57 drilling contractor to perform drilling <br /> activities using a Geoprobe® drill rig or hand auger at the two proposed soil and grab <br /> groundwater sampling locations shown in Figure 3. <br /> If there is any indication of sub-surface utilities based on the USA markings or private utility <br /> survey, the borings will be advanced using a hand auger. If USA and the private utility survey do <br /> not indicate the presence of subsurface utilities, borings will be advanced with the drill rig. <br /> If a hand auger is utilized, the hand auger will be advanced to the target sampling depths oft feet, <br /> 4 feet, and 6 feet bgs. Once each of the target sampling depths is reached, an undisturbed core <br /> sample will be collected at the target sampling depths in a 6-inch-long stainless-steel sleeve <br /> using a split-spoon sampler equipped with a slide hammer. The sampler will be driven into the <br /> soil using a slide hammer. The sampler will be retrieved and the undisturbed stainless-steel <br /> sleeve exposed. Immediately after exposing the stainless-steel liner containing the soil core, the <br /> soil will be field-screened for VOCs using a photoionization detector(PID) and visually logged <br /> using the Unified Soil Classification System(USCS) by a Geosyntec field geologist or engineer, <br /> under the supervision of a California-licensed Professional Geologist. A new, clean stainless- <br /> steel sleeve will be used for each sampling station. <br /> If a drill rig is utilized, soil cores will be collected from the borings using dual-tube direct-push <br /> technology. The dual-tube sampling involves advancing a 2-inch-diameter, hollow steel <br /> direct-push rods fitted with an acetate liner within larger diameter direct-push rods. The rods will <br /> be advanced to the top of the concrete slab (anticipated at 7 feet bgs) without penetrating or <br /> disturbing the slab. Immediately after exposing the acetate liner containing the soil core, the soil <br /> will be field-screened for VOCs using a PID and visually logged using the USCS by a Geosyntec <br /> field geologist or engineer under the supervision of a California-licensed Professional Geologist. <br /> Soil samples for analysis of VOCs and TPH-g will be collected directly from the soil core at <br /> depths of 2 feet, 4 feet, and 6 feet bgs using disposable, laboratory-supplied Terra-CoreTM <br /> samplers and placed into 40-milliliter vials in accordance with the United States Environmental <br /> Protection Agency (USEPA) Method 5035A. A new Terra-CoreTM plunger will be used to <br /> collect each soil sample. <br /> Final Investigation Work Plan Addendum—UST 817B 5 June 24,2022 <br />