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1 v <br /> A S S O C I A T E S I N C <br /> petroleum hydrocarbons as diesel (TPHd), and benzene are shown on Figures 4, 5, and 6, <br /> respectively The highest concentrations of petroleum hydrocarbons are present in wells MW-1, <br />' VW-1, VW-2 and VW-4 The contamination beneath the site appears to generally be limited to <br /> the vicinity of tanks T-1 through T-4, although low concentrations of TPHd have been detected in <br /> perimeter wells MW-3 and N 4W-5 <br /> ' <br /> 4.0 PILOT TESTING PROCEDURES AND RESULTS <br /> 4_1 Vaipor Extraction/Air SBarge Testing- November, 23 and 24 1998 <br /> 4.1.1 Methods and Procedures <br /> On November 23 and 24, 1998, ATC performed a short-term vapor extraction test and attempted <br /> to perform a short-term air sparge test followed by a combination air sparge/vapor extraction test <br /> ' The purpose of these tests was to determine whether vapor extraction could sufficiently capture <br /> air sparge off-gas, to determine short-term volatile organic compound (VOC) flux rates, and to <br /> ' collect data to design an air sparge/vapor extraction system <br /> On the first day, a vapor extraction test was performed by ATC using vapor well VW-1 as the <br /> vapor extraction point while monitoring vacuum response in the surrounding wells, MW-1, MW- <br /> 3, RW-1, PZ-1, VW-2d, VW-2s, VW-3, VW-4, VW-5d, and VW-5s (Figure 2) The test was <br /> approximately 1 5 hours in length Flowrates, applied vacuums, influent and effluent VOC <br /> ' concentrations, and temperatures were also monitored during the test Vapors were extracted <br /> using an internal combustion (IC) engine equipped with a 5-hp blower and a moisture knockout <br /> chamber Two influent vapor samples were collected during the test, one after 15 minutes of <br /> operation and one after 70 minutes of operation An effluent vapor sample was collected after 75 <br /> minutes of operation Samples were submitted under chain-of-custody to Sequoia Analytical <br /> (ELAP #1210) and analyzed for TPHg and benzene, toluene, ethyl benzene, and xylenes (BTEX) <br /> On the B, <br /> he second da of testing, a short-term air sparge test was Initiated by ATC using vapor well <br /> VW-5d as the air infection point while monitoring response in the surrounding wells The <br /> groundwater elevation at the site had risen significantly since the installation of VW-5d and at the <br /> time of the test, the top of the screen in this well was 11 feet below the groundwater table Upon <br /> startup of the test, an air leak was observed in nearby vapor well VW-2s from an apparent crack <br /> in the well seal Vapor well VW-2s was nested with VW-2d Mr Jeff Wong of PHS/EBD <br /> directed ATC to terminate the test and make provisions to abandon well VW-2s <br /> 4.1.2 Results <br /> Results and field readings from the short-term vapor extraction and air sparge tests performed on <br /> November 23 and 24, 1998 are summarized in Tables 4 and b and contained in Appendix B <br /> During the vapor extraction test, extraction flowrates ranging from 47 to 57 cubic feet per minute <br /> (cfin) resulted in vacuums of up to 0 8 inches of water in vadose wells VW-5s and VW-2d located <br /> 17 feet from the extraction well Vacuums of up to 0 5 inches of water were observed in well <br /> W 162574 011pdot-fe report doe 4 <br />