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Date: December 17, 2007 <br />Revised by: Randy Golding <br />Approved by: Randy Golding <br />Praxair Services, Inc. QA <br />Tracer Tighlg <br />Version 6 <br />has displaced the entire volume of the vent piping. The concentration of the tracer in the receiving container is then <br />measured. <br />Leak Simulation <br />Injecting a tracer into the backfill performs a leak simulation. The leak simulation tracer is not one of the tracers used in <br />testing the system. The migration period of the leak simulation tracer is monitored through the sampling probes. The <br />minimum migration time required for the test is equal to the time required for the leak simulation tracer to move an <br />acceptable distance. The minimal acceptable distance is the longest distance that the test tracer would have to travel from <br />any leak location to the location of a sampling probe. <br />Sample Collection <br />Once the leak simulation migration period is determined, the inoculation and waiting period is completed and sampling <br />can begin. Vapor samples are collected from all sampling probes. Additional vapor samples may be collected from sumps <br />containing UST components, under dispenser containers (UDCs) and from the interstitial spaces of double walled <br />components. <br />Sample Analysis <br />Samples are analyzed using an on site laboratory grade gas chromatograph (GC). The GC is calibrated using an external <br />gas standard. Samples are analyzed by direct injection into the GC. The results are evaluated by comparison to the <br />analytical standard. Whenever tracer is detected in the subsurface samples, blanks are run to validate the tracer detection. <br />Spill -Bucket Testing <br />Over -spill -buckets are tested hydro -statically. A decrease in water level indicates a leak. If leaks occur, spill bucket seals <br />should be repaired or replaced. <br />Reporting <br />The findings of the Tracer Tight* ELD test and site evaluation will be summarized in a written report and sent to the client <br />within two weeks of the completion of the fieldwork. All data acquired from probe and sump samples will be reported <br />along with spill bucket hydro -test results. <br />THIS INFORMATION IS THE PROPERTY OF PRAXAIR SERVICES, INC.. <br />3 of 3 <br />