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aecom.com Our Reference 60632236 5/10 Table 1 Sample Container and Holding Time Requirements for Soil Samples Parameter Method Sample Container Sample Volume Preservative Holding Time TPH-g EPA Method SW8260B Terracore sampler into 40-ml glass vials with Teflon-lined septum caps (3) 40-ml volatile organic analysis vials Methanol (1) and water (2) 14 days until extraction BTEX and Naphthalene TPH-d EPA Method SW8015B Glass jar, with Teflon- lined cap (hand-auger samples) or acetate liner with end caps (direct-push samples) 8 ounces 4°C 14 days until extraction Notes: ml = milliliter °C = degrees Celsius Soil Vapor Sampling Procedure Soil vapor samples will be collected at 5 feet bgs from each boring. Sample containers will be labeled with the sample name, location, depth, date, and time of collection; analysis requested; and the sampler's initials. All sample names will follow the naming convention: B#-SV-X-Y-Z, where: B# = Location (B1 to B4), SV= matrix (soil vapor), X = sample collection depth, Y = sample collection month, and Z = sample collection calendar day. Temporary soil vapor wells will be installed at 5 feet bgs in each boring in accordance with the DTSC Advisory (DTSC et al. 2015). New materials will be used for the construction of each well. Following installation, the soil vapor wells will be allowed to equilibrate for a minimum of 48 hours before samples are collected. Prior to sampling, a shut-in test will be completed to test the hermetic integrity of the well, tubing, and connections by applying vacuum and verifying that no pressure was lost for a full minute. A leak test will then be completed by placing a shroud over the entire sample train (pump, Sample T, flow controller, and 1-liter [1L] Summa sample canister) and the top of the sealed borehole and introducing a tracer compound (helium). The helium concentration in the shroud will be measured and recorded periodically on the soil vapor sampling data sheet throughout the duration of purging and sampling activities. Helium concentrations will be maintained at a concentration of 11 percent plus or minus 10 percent while purging and sampling (i.e., two orders of magnitude higher than the reporting limit of the laboratory analytical method [0.11 percent]) in accordance with the DTSC Advisory. After a minimum of 5 minutes following the introduction of the tracer compound, soil vapor will be purged from the well by operating the vacuum pump for the time needed to remove three times the calculated volume of air in the sampling system (i.e., tube, probe tip, and the void space in the sand pack and dry bentonite annular space). If the concentration of helium in the purge sample is greater than or equal to 5 percent of the helium concentration in the shroud, corrective action will be taken to remedy the leak prior to collecting the sample.