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1534 Willow Pass Road,Pittsburg,CA 94565-1701 0 MCCAM PBELL ANALYTICAL INC. Telephone:925-252-9262 Fax:925-252-9269 W "When Quality Counts" O www.mccampbell.com:main@mccampbell.com Standard Operating Procedure: MAI Helium Shroud during Soil Gas Sampling for Quantitative Leak Detection 1. Scope and Application 1.1 The purpose of the Helium shroud technique is to detect leaks during the soil gas sampling procedure. 2. Summary 2.1 The shroud is placed over the borehole to be tested&infused with helium at low pressure. The shroud does NOT need to be gas tight,just rich with Helium vapor. Compared to other liquid leak check compounds such as propanol(s) or Freons, Helium does not interfere with the target compound measurements and hence eliminates the need for sample dilutions,which results in better reporting limits. If there is a leak that comprises less than 5% of the sample, Helium content can be quantitatively analyzed, and the leak dilution factor can be determined during the laboratory analysis after soil gas sampling. A leak of less than 5% is considered an acceptable leak as specified in March 2010 DTSC soil gas sampling guidelines. 2.2 Use of the Helium shroud with an MAI designed soil gas manifold has the following capabilities. 2.2.1 Borehole seal integrity. Surface air intrusion can be checked in real-time, so that sampling can be aborted as wanted. 2.2.2 The Helium shroud can be used with MAI supplied purge can, user-supplied vacuum pump, or a manual syringe. 2.2.3 Allows shut-in-test for verification of leak free manifold. 2.2.4 Quantitative measurement of Helium content within shroud, which combined with lab analysis of Helium content in sample can, allows quantitative evaluation of leak and assessment of<5%DTSC criteria. 2.2.5 Rotameter and vacuum gauges allow assessment of DTSC defined low permeability soils and provide the needed flow/vacuum measurements required for compliant sampling. 2.2.6 MAI's specially designed sampling manifolds offer the option for split sampling upon request. Simultaneous duplicate TO15 and sequential TO15 followed by TO 17 sorbent tube(ST). 2.2.7 MAI's special design optionally allows for simultaneous sampling of a borehole at 2 different depths. 2.2.8 Allows visual monitoring of shroud helium content via helium meter. 2.2.9 Sample technician friendly: allows flood or trickle/maintenance helium input. 2.3 MAI's helium shroud is covered with a secured flexible plastic sheet that functions as the lid. Handling of the equipment inside the shroud is done through the sheet. Practice before field sampling is encouraged for a successful sampling experience. Page 2 of 9