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M CDIM Standard Operating Procedure 4.1 Soil Vapor Sampling "°'"''°'"` Rev.1 6/30/2022 Dedicated sampling equipment (e.g., the flow controller and tubing) is intended to be single use for one well location, whereas non-dedicated equipment is used for sampling multiple wells and for that reason requires decontamination. If non-dedicated sampling equipment is to be used and the contaminant histories of the wells are known, the sampling order should start with the least contaminated well and progress to the most contaminated well. 3.3.2 Pre-Sample System Testing Relevant to both the Vapor PinTm and single or nested vapor well approaches, the following pre-sample tests described in this section are necessary to ensure the quality of collected samples. The details within this SOP are to be used in conjunction with project work plan procedures. 3.3.2.1 Shut-In Test Prior to purging or sampling, a shut-in test should be performed to confirm that the sample canister and flow controller are leak-tight prior to sample collection. A shut-in test is conducted as follows. 1. Remove the brass cap from the sample canister and attach the dedicated flow controller and gauge. Using a wrench, gently tighten connection. 2. Remove one brass cap from the flow controller and connect appropriate length of '/4-inch OD tubing using a compression fitting nut and ferrules (e.g., Swagelok or equivalent). 3. Connect the free end of the tubing to a two-way valve with additional tubing leading from the other end of the two-way valve. 4. Tighten connections to ensure no expected leaks. 5. With the two-way valve open, attach the syringe to the free end of the tubing leading from the valve and gently draw air into the syringe. A negative pressure will result, and the value can be observed on the flow controller gauge. 6. Draw enough air with the syringe such that a negative pressure of approximately 25 inches of mercury (inHg) is achieved, or as much as the syringe volume allows, and close the two-way valve. 7. Monitor the flow controller gauge for approximately three to five minutes. o If the gauge shows a pressure change of more than one inHg per minute, a connection is loose. To correct, tighten all fittings and continue to monitor the gauge. o If a negative pressure is maintained, the sample canister and flow controller system will be considered leak tight. 8. After concluding the shut-in test, open the two-way valve to relieve the system's pressure. A shut-in test is not a replacement for a leak test. 5