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Phase II Subsurface Investigation <br /> Tracy Corners Shopping Center <br /> 3225 North Tracy Boulevard <br /> Tracy,California 95376 <br /> Partner Project Number P14-129814.2 <br /> December 19,2014 <br /> Page 14 <br /> sand pack. The annulus was backfilled with hydrated bentonite to the ground surface to form a seal and <br /> the barbed sampling end of the probe was fitted with a cap prior to sampling. <br /> Soil Gas Sampling Methodology <br /> Soil gas samples were collected using 1-liter, stainless-steel, cylindrical SUMMAI canisters. The sampling <br /> containers were provided by SunStar Laboratories (SunStar), which subjected each canister to a rigorous <br /> cleaning process using a combination of dilution, heat, and high vacuum. After cleaning, the canisters <br /> were batch certified to be free of target contaminants to a specified reporting limit via gas <br /> chromatography/mass spectroscopy prior to delivery. <br /> Partner received the SUMMA canisters evacuated to approximately 30 inches of mercury. The SUMMA <br /> canisters were fitted with stainless-steel flow controllers, which Sunstar calibrated to maintain constant <br /> flow(approximately 150 ml/min)for approximately 5-10 minutes of sampling time. <br /> Each probe was allowed to equilibrate for a minimum of 2 hours after installation prior to sampling. After <br /> equilibration, the sample tubing and sampler screen were purged of ambient air using a separate 1-liter <br /> SUMMA purge volume canister evacuated to approximately 30 inches of mercury. Each probe was <br /> purged for a volume of approximately 375 ml and 600 ml, respectively. Once the purge volume was <br /> reached, the sampling end of the tubing was fitted to the sampling canister and the port valve was <br /> opened, causing air to enter the sample container due to the pressure differential. Partner closed the <br /> valves after the canister was evacuated to approximately 1-2 inches of mercury, with pertinent data (e.g., <br /> time, canister vacuum) recorded at the start and end of sampling. <br /> A tracer gas mixture of isopropyl alcohol (IPA)was placed around each probe at the ground surface while <br /> sampling to detect ambient air intrusion. The tracer gas was not detected in the samples, indicating that <br /> the integrity of the bentonite seal was maintained. In addition, recovery of surrogate compounds <br /> included with each analysis was within acceptable limits, indicating that the sampling containers and <br /> analysis equipment did not leak. <br /> Partner successfully connected individual 1-liter SUMMA canister to each sampling point. <br /> The SUMMA canisters were labeled for identification and stored away from direct sunlight prior to <br /> analysis. <br /> Probes were removed from the subsurface and the boreholes were backfilled with neat cement following <br /> sampling activities. <br /> No significant amounts of derived wastes were generated during this investigation. <br /> Laboratory Analysis <br /> Partner collected five sub-slab soil gas samples (including one duplicate) on December 9, 2014, which <br /> were transported in an iced cooler under proper chain-of-custody protocol to SunStar, a state-certified <br /> laboratory (California Department of Health Services Environmental Laboratory Accreditation Program <br /> certificate number 2250) in Lake Forest, California, for analysis on December 9, 2014. Soil gas samples <br /> were analyzed for CVOCs, specifically PCE, trichloroethene (TCE), cis-and trans-1,2-dichloroethene (DCE), <br /> .._PARTNER <br />