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,• 47 March 2000 <br /> AGE-NC Project No. 98-0432 <br /> '• Page 5 of 6 <br /> Analytical results from ground water samples are summarized in Table 3. The laboratory reports <br /> (PET Laboratory ID PE6975-01 to -04), quality assurance and quality control (QA/QC) reports and <br /> chain-of-custody forms are included in Appendix F. <br /> Figure 3 depicts the <br /> gur p approximate areal distribution of impacted ground water containing MTBE at <br /> concentrations exceeding 500 4g11. The vertical and horizontal extent of all MTBE-impacted ground <br /> water is not known.The horizontal extent of all MTBE-impacted ground water is not known except <br /> toward the north where the compound was not detected in the sample from MW-4. <br /> 3.5. GROUND WATER ELEVATION, FLOW DIRECTION AND GRADIENT <br /> Depth to ground water at the site ranged from 14.11 to 14.79 feet below well casing top. The ground <br /> water elevation in each-well were calculated from these data. The ground water elevations at the site r <br /> ranged from 21.96 feet to 22.95 feet above mean sea level (ms]). The ground water flow direction <br /> and gradient were calculated from the well elevation data. <br /> Contours of the ground water elevation data suggest that the ground water flow was directed toward <br /> the northwest. Figure 4 illustrates the contoured ground water elevations. <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> ' The following conclusions were drawn from the results of this investigation: <br /> The prevailing g mnclAAter flow direction at the site is generally northwest. <br />' • . Only MTBE was detected in soil samples at the site during this investigation. MTBE- <br /> impacted soil extends to a depth of at least 30 feet.bsg, the deepest samples collected. <br />' Only MTBE was detected in ground water samples at the site during.this investigation. <br /> MTBE was detected in three well on the site. The detected MTBE concentrations exceed the <br />' State of California maximum contaminant level (MCL) of 14•µg/l. <br />' 5.0. RECOMMENDATIONS <br />' Based on the results of this investigation, AGE recommends: <br /> i • A quarterly monitoring event should be scheduled for March'2000. <br />' • A work plan for installation of additional assessment of MTBE in soil and ground water and <br /> procedures to assess feasibility of various corrective action alternatives for MTBE in soil and <br /> 1 <br />