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M CDIM Standard Operating Procedure 4.1 Soil Vapor Sampling '"°'"""'"' Rev.1 6/30/2022 3.3.3 Sampling Train Setup The soil vapor sampling train setup includes the following steps: 1. Assemble sample canister (Summa) and dedicated flow controller manifold using a compression fitting cap (e.g., Swagelok fitting). 2. Attach the sample port tubing, typically '/4-inch outer-diameter(OD) Teflon, to the Summa canister and flow controller manifold using compression fitting nut and ferrules (e.g., Swagelok or equivalent). 3. Ensure Summa canister valve remains shut until sample collection. 3.3.4 Shroud Setup Shrouds used for soil vapor sampling are available in either a hard-body or plastic bag form. Both are similar in function and setup, and each can offer an atmosphere for a real-time leak check of the sampling train and retroactive leak detection during sample analysis. Rationale for selecting one type over the other can include the sampling canister volume, volume of tracer gas available, and personal preference. Setup procedures found in this SOP apply to both hard- body and bag shrouds. The shroud is placed directly over the entire vapor well, such that sampling train and the sample port (Vapor Pin TM or well probe) are contained within the shroud's footprint. 3.3.5 Vapor Well Purge and Leak Test The purpose of purging is to remove stagnant air from the well so that representative samples can be collected from the subsurface. A well purge for vapor wells is performed once the sampling system has been assembled. An example of a typical shut-in test / purge manifold assembly is included as Attachment 3.2 and is conducted as follows. 1. Assemble sampling train per Section 3.3.3. 2. Remove the remaining brass cap from the flow controller gauge and replace with an appropriate length of/4-inch OD tubing. Connect the free end of the tubing to the soil vapor well sampling port. 3. Confirm that the Summa valve is shut, but vapor can be purged from the well through the flow controller manifold. 4. Tighten connections. 5. Close shroud. 6. Via tubing connected to a flow regulator, apply the tracer gas (helium) to the shroud. 7. Insert the tracer gas detector into the shroud. 8. Once the detector reads 20% trace gas (helium), the gas can be shut off2. 9. Outside of the shroud, connect the syringe / air pump to the manifold via tubing and begin purging the vapor well. Remove an appropriate volume, such that the stagnant air is cleared while subsurface soil vapor removal is minimized. 2 If helium conservation is a concern, the shroud may be filled with 10% helium instead. 6