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27 June 1996 <br /> AGE-NC Project No. 95-0118 <br /> 3 Page 5 of 23 <br /> -_� 4.2. COLLECTION OF GROUND WATER SAMPLES <br /> Water samples were collected from each well using a new disposable plastic bailer and by <br /> }= transferrin the collected water into 40-m1 EPA vials. The samples were logged on a chain-of- <br /> custody form, placed in a chilled container under ice and transported to MAI. Each sample was <br /> analyzed for TPH-g and BTE&X in accordance with EPA methods 5030/8015m and 602, <br /> respectively. <br /> 4.3. GROUND WATER FLOW DIRECTION AND GRADIENT <br /> The relative elevation of ground water in each well was calculated by subtracting the ground water <br /> depth from the surveyed relative casing elevation(Table 2). The depth to ground water at the site <br /> ranged from 36.68 feet to 39.30 feet bsg in January 1996. Between September 1995 and January <br /> 1996,the average relative ground water elevation decreased approximately 1.5 feet in each well. <br /> During this quarterly sampling event, the dominant hydraulic gradient was directed <br /> southwestwardly, while a conical depression in the ground water surface was observed at the <br /> northwestern portion of the site. The contoured ground water elevation data resembles.a drainage <br /> pattern and the radial depression of the. ground water surface is shaped similar to a draw-down <br /> depression caused by ground water pumping. The relative elevation of ground water is illustrated <br /> on Figure 3. <br /> 4.4. ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> i During the February 1996 monitoring, TPH-g was detected in ground water samples collected from <br /> MW-2 and MW-3 at. concentrations of 1,500 and 1,300 ppb; respectively. BTE&X were also <br /> detected in MW-2 MW-3 and MW-4 at concentrations up to 61 ppb (benzene, MW-2). Petroleum <br /> hydrocarbons were not detected in samples from MW-5 or MW-6.Analytical results of ground water <br /> samples are summarized in Table 3. The laboratory report (MAI Laboratory I. D. Nos. 61075 <br /> through 61080) and chain-of-custody are included in Appendix E. <br /> 5.0. SOIL VAPOR EXTRACTION PILOT TEST <br /> k <br /> 5.1. PROCEDURES <br /> 5.1.1. SOIL VAPOR EXTRACTION SYSTEM <br /> On 15 February 1996, an 8-hour soil vapor extraction(SVE)test was initiated at the site. This pilot <br />