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sample depth identified by the DTSC Guidelines. The direct push rod will be driven down to the sample depth of 5 feet bgs, creating a boring for the installation of a temporary soil gas probe. The soil gas probe will be temporarily installed in each of the two proposed locations. To complete the installation, clean, dedicated nylon tubing with an attached new 1-inch porous foam block will be inserted at the bottom of the borehole,with the other end of the tubing extended to the surface.A total of 12-inches of sand will be placed around the porous foam block(6 inches below and 6 inches above). Approximately one foot of dry bentonite chips will be added to the borehole. The remainder of the borehole will be backfilled with hydrated bentonite to the ground surface. 2.6 SOIL GAS SAMPLING AND ANALYSIS The DTSC Guidelines recommend that the soil gas probes be allowed to equilibrate after installation, and before sample collection. To comply with the DTSC Guidelines, 30 minutes of time will be allotted to allow each probe to equilibrate before the soil gas samples are collected. Soff gas sampling will be collected through the dedicated porous foam block and nylon tubing installed at each location. At the surface,the tubing will be connected to a sampling manifold using SwageloV fittings and a Summa canister. The sampling manifold consists of a stainless steel tube with a pressure gauge, a vacuum gauge, and connections for the sample canister and purge device. The dedicated porous foam block and nylon tubing will be isolated from the ambient air using a manifold valve. The soil gas probe will be purged using either a syringe or hand pump and will be purged a minimum of seven (7)purge volumes prior to sample collection. Samples will be collected using laboratory prepared Summa canisters. During the soil gas collection process,a leak check will be performed as part of the sampling quality assurance/quality control (QA/QC). As a leak check compound, 1,1,1,2-Tetraflouroethane will be used at the sample collection point to ensure to verify that no air is leaking mto the manifold during the sample collection Soil gas samples will be analyzed at lower detection limits using United States Environmental Protection Agency(USEPA)Test Method TO-15. Samples will be collected in Summa canisters and delivered to the laboratory within 24-hours of collection under proper chain-of-custody documentation. The laboratory's detection limits are listed in the following table in micrograms per cubic meter(µg/m): Analyte Reporting Limit (Ag/M) TPH-G 2.2 Benzene 0.020 Toluene 1.0 Ethyl benzene 0.20 Xylenes 2.0 MTBE 1.0 TBA 2.0 DIPE 1.0 ETBE 1.0 TAME 1.0 2.7 GROUNDWATER MONITORING WELL SURVEY The top of casing elevation for each of the proposed monitoring wells will be surveyed by a licensed land surveyor to within 0.01-foot vertical elevation relative to mean sea level, and will be 03009-10016-37020 5 WINZLER&KELLY August 2011