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31 May 2023 AdvancedGeo Project No. 23-7208 An Employee-Owned Company Page 3 of 4 connections for both purge syringe and sampling canister (manifold assembly). Prior to sample collection, each soil-vapor well will be purged a total of three purge volumes. The purge volume will be determined by calculating the sum of the internal volume of the Teflon tubing and the volume of the boring trace. Upon achieving the targeted purge volume, the purge syringe will be disconnected, and the sample canister valve will be opened. Each canister's initial vacuum will be measured and recorded between -26 and -30 inches of mercury (in hg). Each soil-vapor well location will be isolated from ambient air by enclosing the borehole, tubing and manifold/canister assembly. Helium will be emitted into the shroud surrounding the well borehole, tubing and manifold/canister assembly and acts as a tracer gas to evaluate if leaks in the sampling apparatus have allowed infiltration of ambient air. Upon reaching at least -5 in hg or less, the sample canister valve will be closed, and final pressure and time recorded. The sampling port on the sampling canister will be capped with a brass end- cap. The soil-vapor sample will be labeled with sample ID, project name, date, time, and samplers' initials. Selected samples will be transported under chain-of-custody procedures to an appropriate laboratory for VOC analysis. Analysis shall be performed at the sole direction of AGI. 2.4. BORING ABANDONMENT All borings will be permanently sealed to prevent vertical migration of potential contaminants by backfilling with cement grout from the total depth to surface grade. The top three to six inches of each boring will be completed flush to surface grade with concrete or native material. The EHD will be notified for grout inspection at least 48 hours prior to conducting grouting procedures. 2.5. EQUIPMENT DECONTAMINATION/WASTE MANAGEMENT All sampling tools used for sample collection will be thoroughly rinsed with clean water after being washed with a solution of Alconox. All probing rods will be cleaned prior to advancement at each probe boring location. Any soil or water waste generated during field activities will be containerized in properly labeled DOT-approved drums and stored on-site in an area generally lacking public access. Disposal alternatives will be evaluated based on results of soil and/or water analysis.