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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 leak of the sampling train during the Shut-In test, REPLACE the manifold and REPEAT the Shut-In test of the new manifold. 5.5.5 If no significant leak is detected; Valve I and purge can valve are reopened and soil permeability is noted. Note: Two criteria MUST be met;sample flow of at least 100mL/min AND borehole vacuum of-7.35 inHg are required to proceed. If these conditions are not met, damage to MAI equipment may occur at the expense of the sampler. Please see the "Sampling" section of this document for sampling procedure when the aforementioned criteria are not met. 5.6 Leak Test 5.6.1 The purpose of this test is to determine if ambient air is introduced into the sample during collection 5.6.2 The MAI Helium Shroud design allows for the Leak test to be performed while the Shut-In test is in progress. The Leak test is performed to verify a gas-tight connection between the borehole tubing andthe manifold as well as confirm a good grout"seal"prior to sample collection. 5.6.3 It is used for shallow wells to determine if there is high permeability between the sub-surface sample tubing and the ground surface. This test is useful only if sampling will be aborted if a borehole leak is detected. 5.6.4 While waiting the "one minute" time requirement of the Shut-In test, attach helium meter to end of blue tubing on Port 4. 5.6.5 Using 60mL syringe take a helium reading of the borehole; attach syringe to outlet of meter and give a quick pull on the plunger. (Pulling 60 mL of air through within a second is sufficient.) Repeat 2 times to get an accurate reading. 5.6.6 If shroud is charged to 20%(f2%)helium and meter reads< 1%helium in well,borehole seals pass DTSC<5%leak criteria. 5.7 Purge Volume Test 5.7.1 Note: There are several procedures for determining well volume and purging well volume. Please refer to the April 2012 DTSC Advisory section 4.2.3 — 4.3 for more information. An accepted method is listed below" however, this method may not be appropriate for all wells and may not always apply. 5.7.2 Turn 3-way Valve I so it is perpendicular to the manifold (pointing towards Port 4). Attach 60 mL syringe to end of blue tubing attached to outside of shroud box at Port 4. 5.7.3 Using the supplied 60mL syringe, pull suction on borehole sampling tube until plunger resistance is felt, noting final volume evacuated. The default purge volume is three times that of the well tubing volume(April 2012 DTSC Advisory 5.8 Sampling 5.8.1 After Shut-In test, Leak test, and purge volume procedures have been completed and helium concentration is maintained at 20% (f2%); ensure 3-way Valve I is parallel to manifold (pointing towards the gauges)and therefore allowing sampling from well. Page 7 of 9