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In order to characterize the concentration of petroleum hydrocarbons in the ' extracted soil vapor, EMCON Associates' field engineer collects a sample of the soil vapor which is then analyzed by a state-certified laboratory. The vapor sample(s) is collected in an evacuated 3-liter stainless steel canister. After the SVET has stabilized at a given extraction vacuum, the canister is connected to the extraction well head assembly and allowed to fill with soil vapor while the SVET system is operating. A description of the SVET ' system is included in the following paragraphs. The SVET system consists of the extraction and monitoring wells and two ' primary components, which are the granular activated carbon (GAC) canisters and the vacuum blower. The blower creates a vacuum which draws soil vapors from the extraction well, through the GAC canisters, to be ' vented to the atmosphere at the blower exhaust. Two GAC canisters are located near the extraction well. The GAC serves as an emissions control device; organic compounds contained in the soil vapors adsorb onto the carbon, rather than being released to the air. Each canister is the size of a 55-gallon drum. A 5-horsepower electric blower provides the vacuum that serves as the driving force for extracting soil vapor. The blower is a regenerative-type with an explosion-proof motor and starter, rated at a maximum vacuum of 93 inches of water column at a flow of 50 cubic feet per minute. A trailer-mounted generator provides the electric power necessary to operate the blower. ' In addition to the primary components described above, the soil-vapor extraction system is equipped with monitoring instruments used for data collection. Bimetallic thermometers measure temperature at the inlet and outlet of the carbon canisters and at the outlet of the blower, as well as ambient conditions. Magnehelic vacuum gauges measure the velocity and ' static pressure of the soil vapors and also indicate the vacuum at each monitoring well. From the velocity and static pressure of the soil vapors, the volumetric flow rate is determined. A sample calculation of flow rate is ' included with this appendix. Finally, several appurtenances provide safety and flexibility to the system. To prevent damage to the individual components from vacuums greater than the system can withstand, a vacuum-relief valve is attached to allow atmospheric air to enter the piping system. The system also has a ball valve to allow the operator to control the amount of vacuum in the system by bleeding ambient air into the system. When ambient air is allowed into the system, it reduces the amount of vacuum exerted on the extraction well, and subsequently reduces the volumetric flow rate of soil vapors from the extraction well. pj010f9010f900020.1 ag F - 2 Rev. 0 December 15, 1992 i