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leaving an open boring. Using a 1/2-inch diameter PVC pipe, inert disposable NylaflowT" tubing with a diameter of 1/4-inches and an attached microfilter sampling tip (implant) will be installed in the boring at the target depth. Following installation of the sampling tubing, a one-foot thick annular sand-pack will be installed. The sand-pack will be centered around the sampling tip. One foot of dry granular bentonite will then be added to the boring, followed by an additional 3 feet of hydrated granular bentonite up to the ground surface. Each sampling tubing will be labeled and finished at the surface with an in-line clamp and two way valve. The in-line valve or clamp will be kept in place at all times while not sampling to prevent the backflow of ambient air into the sampling line between purges and prior to sampling. To allow subsurface conditions to equilibrate, no further procedures will be conducted for approximately two hours, or in the case of augered borings, 48 hours. Soil gas sampling will not be conducted during or immediately after any significant rain event (e.g., 1/2 inch or greater) or any onsite watering which may cause no-flow or low-flow conditions. During sampling, a leak detection gas (1,1-difluorethane or 1,1-DFA), as found in standard keyboard cleaner, will be used to saturate the air space inside an overturned bucket, which is then placed over the ground surface at the borehole and over the sample train to confirm that the sample train and tubing surface seal is tight and leak free. The leak test will be conducted in accordance with DTSC guidance documents, and will be conducted at each individual soil gas sampling location. The detection limit for analyses for the leak check compound will be no greater than 10 times the reporting limits of the target analytes. Following completion of the soil gas sampling, and after the laboratory has confirmed a successful analysis of the sample, sampling implants will be abandoned by removing the tubing from the boring, and abandoning the boring in-place. The hydrated bentonite seal will continue to swell, sealing the tubing void. Ultimate closure of the sealed borehole will be performed in accordance with SJCEHD requirements. Purge Volume Soil gas samples collected for testing at an onsite mobile laboratory or for analysis at a fixed laboratory will be purged of three purge volumes prior to sample collection. The volume of each sampling train, including the annular space of the dry, granular bentonite layer and sand-pack, will be calculated to determine the purge volume. Following equilibration, a syringe or a Summa canister will be used to purge each sampling train. Mobile Laboratory Testing For soil vapor sample collection and associated VOC analyses performed onsite, the work will be conducted by a California certified mobile laboratory using USEPA Method 8260B. Samples will be collected in an air-tight glass syringe. The flow rate during purging and sampling will be moderated to between 100 and 200 milliliters per minute (mL/min) by the sampler to limit stripping of chemical compounds, to prevent ambient air from diluting the soil vapor samples, and to reduce the variability of sampling rates. Glass syringe samples will be injected into the gas chromatograph within 15 minutes of sample collection. Sampling and Analysis Plan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 24