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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 5.8.2 Conventional TO 15 summa sample collection procedures are now used. Generally, sample collection ceases when Gauge 2 (located on the sample canister side) reads approximately -5 inHg. At 150ml/min a 1L summa will fill in approximately six minutes. During sampling monitor helium concentration regularly. 5.8.3 DTSC recommends samples not be collected if down hole vacuum(Gauge 1)registers<-7.35 inHg (-100 inches of water),or flow falls below 100ml/min,indicating soil permeability is too low. 5.8.4 If low permeability is observed,close sampling can from sampling train IMMEDIATELY to prevent excessive moisture from entering into sampling canister,as this will invalidate the sample. 5.8.5 If soil is observed as low permeability soil, special sampling procedures are required as outlined in April 2012 DTSC Advisory App D. 5.8.6 If borehole vacuum reaches < -7.35 inHg, sampling should be suspended by closing valve on sampling can. After a few minutes, soil gas will replenish borehole and vacuum will gradually dissipate (refer to Gauge 1 located on borehole side of manifold for vacuum reading during this time). Sampling may resume after soil gas replenishes. 5.8.7 Once vacuum decreases, and sampling resumes, it is imperative that the sampler closely monitors borehole pressure as it may drop below -7.35 inHg again. If this occurs, repeat the `shut' to `replenish', then `sample' cycle until sampling is completed. Length of replenish time depends on permeability of soil. 5.9 Optional Sampling Step 5.9.1 Sequential TO15 and TO17 sampling: 5.9.1.1 Naphthalene may be required to be sampled using TO17 sorbent tubes and a helium shroud. A modified set up for split sampling can be used, which consists of one TO15 sample can,a sorbent tube (ST), a TO17 purge/sample can, an additional 2-way valve IV and a 75ml/min flow restrictor, the latter two items are both located on the `split sample attachment'. The TO17 ST is located between the 2-way valve IV/flow restrictor and the purge/sample can. This configuration is ideal for the following: 5.9.1.1.1 Restricts flow to the prescribed 50-100ml/minute(DTSC stipulation) 5.9.1.1.2 Allows naphthalene to be collected on the ST 5.9.1.1.3 Helps determine collected air STP volume that has passed thru the ST by lab measurement of the sample can initial and final pressure 5.9.1.1.4 Collects sample for helium leak check analysis in that branch's sample can 5.9.2 Installation of TO17 sorbent tube also requires the sampling flow direction is the same as indicated on the tube body. Naphthalene cannot be desorbed from the tube if collected at the wrong end of the tube. Teflon (TFE) ferrules are used for connections on the ST. Use of metal ferrules are strictly prohibited for connecting TO17 ST as they permanently damage the tube, Such damage will be billed to sampler. Page 8 of 9