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' 19 January 2004 AGE-NC Project No 95-0173 ' Page 5 of 10 ' In order to monitor efficiency of the SVE system 1) a Magnehelic vacuum gauge (Dwyer DS-200 flow sensor) was installed prior to the inlet of the ' SVE unit to monitor air flow,the flow rate was determined from the measured differential pressure and the piping diameter using a nomograph (Appendix D), ' 2) SVE air flow of the influent and effluent streams was monitored routinely for the presence of organic vapor using an organic vapor analyzer (OVA) equipped with a photo-ionization detector (PID Thermo Environmental 580B, 10 0 eV, calibrated to isobutylene), and 3)Influent and effluent air flow vapor stream samples were collected from sampling ports installed upstream (influent) of the vacuum blower and downstream (effluent) of the carbon canisters, and submitted for laboratory analysis Field measurements were recorded at regular intervals and are summarized in Table 6 Between 22 June and 25 August 2004, an induced vacuum was applied to SVE wells VW-1 through VW-4 to extract hydrocarbon vapor from the subsurface, between 25 August and 23 September ' 2004, the SVE remediation network was reconfigured so that SVE wells VW-1, VW-2 and VW-5 were `open' Wells VW-3,VW-4,VW-6 through VW-7 were `closed' at the well-heads due to only trace levels ofpetroleum hydrocarbons previously observed from PID field measurements(Table 6) 32 IN-SITU AIR SPARGING SYSTEM PROCEDURES The IAS system utilizes a 5-horsepower, Speedaire (model no 5F229B) electric air compressor to inject air beneath the water table From the outlet of the air compressor, a manifold network of ' 1-inch diameter, schedule 80 PVC piping was installed underground to the well heads at IAS wells -i AW-1 through AW-7, and ground water monitoring wells MW-1 through MW-3 A Wilkerson oil filter (model no M18) and Wilkerson air pressure regulator (model no R28) are installed at the ' outlet of the air compressor for added controls The injected air should volatilize dissolved hydrocarbons in the ground water and force hydrocarbon vapors into the vadose zone, where they can be withdrawn by the SVE system described above Between 22 June and 06 July 2004, air pressure was continuously discharged from the air compressor to well AW-2B at 14 pounds per square inch (psi) However, between 06 July and 23 September 2004, air pressure was continuously discharged from the air compressor to well AW-1B between 12 and 13 5 psi Utilizing a Solinst water level indicator and a YSI-50 dissolved oxygen meter, measurements of ground water depth and dissolved oxygen from ground water monitoring wells MW-1, MW-2, and MW-3 were performed to determine if ground water mounding was occurring as a result of the above IAS activities ' Advanced Geo Environmental,inc