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' 14 February 2006 AGE-NC Project No 98-0448 ' Page 4 of 9 ' ionization detector (PID Thermo Environmental 580B, 10 0 eV, calibrated to isobutylene), and 2) influent air flow vapor stream sample was collected from sampling ports installed upstream (influent)of the vacuum blower and analyzed Field measurements were recorded at regular intervals and are summarized in Table 6 ' 32 IN-SITU AIR SPARGING SYSTEM PROCEDURES Between September 2005 and November 2005,the IAS system utilized a 7'/z horsepower,Westward ' (model no 5Z639)electric air compressor to infect air beneath the water table, ideally, the infected air should volatilize dissolved hydrocarbons in ground water,and force hydrocarbon vapors into the vadose zone, where they can be extracted by the above SVE system From the outlet of the air ' compressor, a manifold network of one-inch diameter, schedule 80 PVC piping was installed underground to the well heads at 1AS wells AW-I through AW-4 (screened 25-30 feet), AW-5 (30- 35 feet) and deep monitoring well MW-4B (screened 45-50 feet) 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, Wilkerson air pressure regulators (model no R18) are installed at each IAS well head to enable independent control over the varying pressures required to displace water within each air sparge well casing, resulting in continuous air spargmg in the IAS network system Generally, air pressure was discharged at shallow screened IAS wells AW-4 and AW-5 between 4 and 8 pounds per square inch (psi), and to deeper screened well MW-413 between 8 and 10 psi A liquid-filled, air-gauge was installed at each of the above well heads to monitor air pressure 33 COLLECTION AND ANALYSIS OF VAPOR EXTRACTION AIR FLOW SAMPLES A total of two extracted air flow vapor samples were collected on 18 October and 22 November 2005 ' from the influent stream of the regenerative vacuum blower unit to measure concentrations of hydrocarbon vapor The samples were collected in Tedlar bags utilizing an electric air-vacuum PUMP Following sample collection,the samples were properly labeled, placed in a covered container and transported under chain of custody to a DHS-certified laboratory for analysis Each sample was ' analyzed within 72 hours of collection for TPH-g and BTEX/MTBE in accordance with EPA Methods 8015M Modified and 8260B, respectively Advanced GeoEnvironmental,Inc