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' 20 April 2000 • AGE-NC Project No 95-0143 Page 4 of 6 ' ranged from 0 43 feet to 7 03 feet above the screened interval in the nine monitoring wells Ground water was within the screened intervals of each vapor well The approximate hydraulic gradient was calculated to be 0 002 ft/ft with a northeasterly flow direction on the subject property Ground water ' elevation was higher in wells VW1 through VW4, indicating ground water mounding However, ground water elevation decreased immediately upon disconnecting the SVE blower from these wells The ground water elevation in MW-7 showed little increase, indicating that the majority of the ground water mounding is limited to the immediate vicinity of the extraction wells Ground water elevation contours for the February 2000 momtonng event are illustrated in Figure 4 32 ANALYTICAL RESULTS OF WATER SAMPLES ' During the February 2000 monitoring event, TPH-g was detected in samples collected from all nine monitoring wells at concentrations ranging from 57 parts per billion (ppb, reported as micrograms per liter), to 220,000 ppb (MW-3) BTEX compounds were also detected in all nine wells at concentrations as high as 45,000 ppb (toluene in the sample from MW-3) Fuel oxygenates were not detected in samples collected from the site during the February 2000 sampling event Measurable free product was not encountered in any of the wells on the site Analytical results of ground water samples collected during the February 2000 monitoring event are summarized on Table 2 Analytical results of historical ground water samples are summarized on Tables 3 and 4 The laboratory report(MAI Laboratory I D Nos 31002-31010)and chain-of-custody forms are included in Appendix B High concentrations of dissolved oxygen were observed in water samples from vapor wells VW-1 ' VW-2, VW-3 and VW-5 during the March 2000 monitoring The concentration of dissolved oxygen in ground water remained generally stable at the site relative to previous monitoring events Dissolved oxygen data are summarized on Table 5 3 3 OPERATION OF SVE/IAS UNITS The SVE system operated at a capacity between approximately 260 cubic feet per minute (cfrn) and 278 cfrn The burner temperature was maintained near 1450°F during thermal oxidation operation and near 650°F during catalytic operation The lower explosive limit (LEL) of the intake vapor stream was approximately 4 to 6 percent ' Field measurements of flow, vacuum and organic vapor concentration in the air stream from each • extraction well were measured on a periodic basis Due to the tight soil conditions and limited screen intervat, a vacuum potential near 50 inches of water was maintained on wells VW 1,VW2, VW3 and Advanced CeoEn%iron mental,Inc I