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• AdvancedGeo Environmental 05 January 2018 AGE Project No. 18-4265 Page 4 of 6 vapor sample collection. Once the tubing and vapor-tip are in place, a filter pack of #3 sand will be placed from the bottom of the borehole to one-foot above the vapor tip. Following placement of the filter pack, dry bentonite crumbles will be placed atop the filter pack. Thereafter, bentonite chips will be placed and hydrated to near surface grade to seal the vapor well from ambient air intrusion. Following soil-vapor well installations, a minimum of one hour stabilization period will be observed prior to sample collection at each of the vapor point well locations. A one-liter Summa canister and a 6-liter purge canister will be connected together with a dedicated and serialized sampling inlet manifold. The sampling inlet manifold will consist of an air/vapor-tight valve; a particulate filter; a calibrated flow restrictor calibrated to 200 milliliters per minute (ml/min), a stainless steel tee-fitting, two vacuum gauges at either end of the controller and connections for both purge and sampling canisters (manifold assembly). The manifold assembly will be attached to the 1/4-inch Teflon® tubing from the vapor sampling locations. The purge canister will be attached to the end of the sampling manifold while the sample canisters will be attached to the tee-fitting between the tubing and purge container. Leak tests will be performed on each 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 3 to 5 minutes on each 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. The purge volume will be determined by calculating the internal volume of the tubing and open borehole area. Upon achieving the targeted purge volume, the purge canister valve will be closed and the sample canister valve will be opened. The initial pressure 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. All soil-vapor samples will be labeled with sample ID, project name, date, time, and samplers' initials. The samples will be logged on a chain-of-custody form, and placed into dry containers. Subsequently, all collected soil-vapor samples will be delivered to a California Department of Public Health (CDPH)-certified analytical laboratory, for analysis.