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C <br /> • Isopropyl alcohol should be utilized as a leak detection compound during sampling by <br /> saturating cotton gauze on the downhole side of the vapor-tight valve and at the surface <br /> of the boring. Each sample is collected by closing the purging shut-off valve on one side <br /> of the "T" and opening the sampling.summa canister until the gauge indicates <br /> approximately 5 inches of Hg remaining (approximately 30 minutes for a 6-liter canister <br /> equipped with a 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 /> Selected Appendix References: <br /> California Department of Toxic Substances Control (DTSC) and Los Angeles Regional <br /> Water Quality Control Board(LARWQCB),2003,Advisory—Active Soil Gas Investigations, <br /> January 28,2003. <br /> New York State Department of Health; Bureau of Erivironmbntal Exposure Investigation, <br /> 2005, Guidance for Evaluating Soil Vapor Intrusion, in the State of New York, Public <br /> Comment Draft,February 2005. ` <br /> San Mateo County, 2004, Guidelines for Subsurface Vapor Sampling Using a Geoprobe and <br /> Summa Canisters, September 9,2004. -'�• r <br /> Page 8 of 8 <br />