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9 PAHs using EPA Method 8310; TPH as gasoline, diesel and motor oil using EPA Method 8015; and for Title 22 Metals using the EPA Method 6010/7000 Series. 4.4.2 Soil Gas Sampling Volatile organic compound impacts identified in Soil Gas Sample A3-SG1 will be delineated through the installation and sampling of proposed Soil Gas Borings A3-SG2 through A3-SG6. Sampling will be conducted in the warehouse area adjacent to the existing office building and adjacent to the northern boundary of the Site near the electrical substation. The data generated through the installation and sampling of these soil gas borings will assist with the characterization of the Site and the provide information that will assist in the determination of the potential for vapor intrusion into the on-site buildings. Additionally, PCE impacts identified in Soil Gas Boring Al-SGI will be delineated with the installation of Soil Gas Borings Al-SG2 and Al-SG3, located northeast and southwest of Al-SGI, respectively. These soil gas points will assist in the determination of PCE impacts and their potential source. All soil gas samples will be analyzed using EPA Method TO-15 and will include naphthalene. A real-time leak test will be performed at each probe location using either helium or a duster as a tracer compound. The tracer compound will be placed around the probe seal at the surface utilizing a shroud to encompass the sampling train. A sample will then be drawn from the probeltubing into a new Tedlar bag and tested for the tracer compound with a hand-held detector to ensure that ambient air does not dilute or contaminate the soil gas sample. If leakage is confirmed(>10% of the concentration introduced into the shroud), the source of the leak will be identified, repaired and the real-time leak check will be conducted again. This will continue until all leaks have been repaired; thus allowing the collection of the soil gas sample. The following real-time leak check protocols for helium and/or the duster compound have been developed for this Site based on the January 30, 2009 letter from DTSC to PG&E, referencing new leak detection procedures. Soil Gas Ambient Air Leak Detection Protocol using Helium Real-time leak testing procedures using helium as the tracer compound will be accomplished as follows: 1. Introduce the tracer gas around the sample probe and canister by filling a shroud (such as a plastic bucket)positioned over the sample location. 2. Make sure the shroud is suitably sealed to the ground surface. 3. Introduce the tracer gas into the shroud. Helium should be injected into the shroud at 5 psi. The shroud will have tubing at the top of the chamber to introduce the tracer gas into the shroud and a valve fitting at the bottom to let the ambient air out while introducing tracer gas. The helium concentration within the shroud will be monitored with a field helium detector and maintained at 30%. 4. The shroud will have a gas-tight fitting or sealable penetration to allow the soil vapor sample probe tubing to pass through and exit the chamber. 5. Attach the sample probe tubing exiting the shroud to a pump that will be pre- calibrated to extract soil vapor at a rate of no more than 0.2 liters per minute.