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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 points to the nearest shroud wall) for initial Helium charge,which takes less than 5 seconds to is needed to reach a 20% Helium concentration. Briefly kneading the plastic cover post helium"flood"will expedite a 20%Helium equilibrium within the shroud. 5.3 Sampling train volume estimation. 5.3.1 MAI has estimated sampling train volumes for multiple sampling configurations. Volume estimates are calculated from manifold's Valve I to the source of suction. They are listed here for sample convenience: 5.3.2 Single sample configuration: 18.8 mL 5.3.3 Duplicate sample configuration:20.6 mL 5.3.4 Serial TO15 and TO17 with Helium sample canister:20 mL 5.3.5 Serial TO15 and TO17 without Helium canister: 18.8 mL 5.4 Maintaining Helium Concentration in Shroud 5.4.1 After initial "flood" of helium (about 5 sec), turn Valve III to `low purge' position (tapered end of valve—with arrow—will point toward far shroud wall/Port 1). The helium tank is set at 250 mL/min helium flow, used in conjunction with an air pump at the opposing side of the shroud; pulling 1.25 mL/min out of the shroud will roughly maintain a 20%helium concentration within the shroud. Note:Initial helium concentration will be much higher than 20% however it will stabilize in roughly 5 min. 5.4.2 Monitor helium concentration within shroud regularly throughout sampling process to assure it is maintained at 20% helium (f2%). To do this, simply attach the 60mL syringe to the outlet on the meter and quickly pull 60mL,repeat two times(total of three pulls). It is recommended to record the helium concentration within the shroud once every minute(April 2012 DTSC Advisory). 5.4.3 Maintain helium at 20%concentration for five minutes before beginning sampling process. 5.5 Shut In test 5.5.1 The purpose of this test is to detect leaks in the above-ground sampling apparatus. 5.5.2 A six liter evacuated canister is employed as the vacuum source for the Shut-In test and the Leak test. A Rota meter attached to the purge can monitors flow rate, Gauge 1 (left side) on the manifold indicates vacuum level of well in negative inches of mercury(-inHg). 5.5.3 Ensure sampling container(s) and Valve I are closed (Valve I is closed when perpendicular to manifold); open Purge Can valve, then open 2-way Valve 11 (Valve 11 open when in line with manifold). 5.5.4 Once vacuum gauges read -30 inHg (or 100 inH2O) close Purge Can valve. Verify absence of a significant leak by monitoring vacuum gauges on sampling manifold for a loss of vacuum for AT LEAST ONE MINUTE. Note:No movement on either gauge for ONE MINUTE is sufficient to proceed(during this time, see "6. Leak Test"below, and perform the Leak test before proceeding here). If there is a noticeable Page 6 of 9