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08 November 1996 <br /> AGE-NC Project No 95-0137 <br /> ' Page 2 of 3 <br /> stored in a chilled container and transported under chain-of-custody to Alpha Analytical Laboratories <br /> (AAL) in Ukiah, California Each sample was analyzed for TPH-g, TPH-d, and BTE&X with <br /> methyl-tert-butyl ether(MTBE)in accordance with EPA methods 503018015, 503018015m and 602, <br /> respectively <br /> ' 3.0. FINDINGS <br /> 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION <br /> Figure 3 illustrates the relative ground water elevation on 20 August 1996 Depth to ground water <br /> I at the site ranged from 18 54 to 19 35 feet bsg The data indicates an average decrease in ground <br /> water elevation at the site of 0 31 feet since April 1996 <br /> Historically, ground water flow direction at the site has varied from northwest to southeast with a <br /> consistently shallow gradient During August 1996, the ground water gradient was calculated to be <br /> 0 0013 ft/ft, with a north-northwesterly flow direction <br /> 3 2 PETROLEUM HYDROCARBON-IMPACTED GROUND WATER - <br /> ' Overall, concentration of hydrocarbons increased at the site between April and August 1996 TPH-g <br /> was detected in wells MWA through MW-4 at concentrations up to 11,000 4gll (micrograms per <br /> { liter or parts per billion ppb), TPH-d was detected each well at concentrations as high as 2,300 ppb <br /> (MW-3) <br /> ' Benzene was detected in samples from MW-1 and MW-2 at concentrations of 1 3 and 1,400 ppb, <br /> respectively, toluene, ethylbenzene and xylenes were also detected in samples collected from wells <br /> ' at the site at concentrations up to 490 ppb (xylenes, MW-2) MTBE was not detected during the _ <br /> August 1996 sampling Analytical results of ground water samples are summai ized in Table 2 The <br /> laboratory report(AAL Batch No 96-0821-007) and chain-of custody are included in Appendix B <br /> 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> ' 41 CONCLUSIONS <br /> Based upon data collected during the August 1996 monitoring,AGE has the following conclusions <br /> • Between April and August 1996, concentrations of most dissolved petroleum hydrocarbons <br />