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• Isopropyl alcohol should be utilized as a leak detection compound during sampling by <br /> saturating cotton gauze on the down hole side of the vapor-tight valve and at the surface of <br /> the boring. Each sample is collected by closing the purging shut-off valve on one side of <br /> the"T"and opening the sampling summa canister until the gauge indicates approximately <br /> 5 inches of Hg remaining(approximately 30 minutes for a 64iter canister equipped with a <br /> 167 milliliter-per-minute flow regulator). <br /> • The canisters are then delivered to Air Toxics Ltd.,a state-certified laboratory under chain- <br /> of-custody protocol. Requested testing should include the leak detection compound <br /> (2-propanol). <br /> References: <br /> California Department of Toxic Substances Control(DTSC)and Los Angeles Regional Water <br /> Quality Control Board(LARWQCB), 2003,Advisory—Active Soil Gas Investigations,January <br /> 28,2003. <br /> New York State Department of Health,Bureau of Environmental Exposure Investigation, <br /> 2005, Guidance for Evaluating Soil Vapor Intrusion in the State of New York, Public Comment j <br /> Draft,February 2005. <br /> San Mateo County, 2004,Guidelines for Subsurface Vapor Sampling Using a Geoprobe and <br /> Summa Canisters;September 9, 2004. <br /> Page t of t <br />