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AdvancedGeo Environmental "Ogg 13 June 2018 AGE-NC Project No. 04-1239 Page 5 of 6 Above ground, the surface around the soil-vapor tubing will be sealed with bentonite powder and hydrated to prevent ambient air intrusion. To ensure that a reliable soil-vapor sample is collected with no ambient air breakthrough, AGE will apply approximately 6 to 8 ounces of isopropyl alcohol (IPA) as a tracer to adequately wet cotton balls; the wetted cotton balls will be placed next to the sampling tubing, then covering the entire sampling train with a large see-through plastic shroud. Measurements of the organic vapor (IPA) concentrations will be collected from within the shroud during the process and recorded, to determine if sufficient tracer compound is present (detected as the starting values). 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, the soil vapor point and the volume of the boring trace. Leak tests will be performed on the soil-vapor sampling assembly by attaching and securing the sample and purge canisters to the manifold and opening the valve on the purge canister and the manifold. The leak test will be performed for approximately 10 minutes on the assembly. Upon achieving a successful leak test, the purge canister valve will be opened for a calculated period of time to allow for three volumes of air to be purged. The purge canister vacuum gauge will be monitored to ensure a proper decrease of vacuum ensuring flow and purging. Upon achieving the targeted purge volume, the purge canister valve will be closed and the sample canister valve will be opened. The initial pressure (approximately -32 in Hg) and time will be recorded. 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. The sample will be logged on a chain-of-custody form, and placed into a dry container for transportation. Subsequently, the collected soil-vapor samples will be delivered to a California Department of Public Health (CDPH)-certified analytical laboratory, for analysis of the following constituents: TPH-g in accordance with EPA Methods TO-15; VOC's including BTEX, Naphthalene and isopropyl alcohol in accordance with EPA Method TO-15; and Oxygen (as a percentage) in accordance with Modified ASTM D-1946.