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March 29, 1991 Results <br /> r PETROLEUM HYDROCARBONS AS GASOLINE <br /> v - Ground water beneath this site has gasoline range _Contamination. 4 4 <br /> Only monitor wells MW1 and MW5 are above the detection limits for <br /> Total Petroleum Hydrocarbons (TPH) , greater than 0.05 parts per <br /> million (ppm` , with 0.3 ppm (a decline from 2 ppm on November 21, <br /> 1990) and 22 ppm (a decline from 31 ppm on November 21 , 1990) <br /> respectively. Monitor wells MW1 and MW-5 tested above the <br /> detection limits for the Volatile Aromatic Compounds of Benzene, <br /> Toluene, Ethylbenzene, and Xylenes (BTEX) , see Table 1, Figure 5A <br /> and Appendix B. <br /> FECAL COLIFORM <br /> On April 8, 1991, samples from monitor wells MW4 and MW6 were <br /> obtained for analysis of fecal coliform. Both samples were below <br /> detection limits of 2 MPN/100ml, samples obtained from MW3, MW4 <br /> and MW6 on September 5, 1990 showed that only monitor well MW6 <br /> tested above detection limits at 11 MPN/100ml, this analysis was <br /> not run during the most recent sampling. <br /> June 24, 1991 <br /> PETROLEUM HYDROCARBONS AS GASOLINE <br /> Ground water samples were obtained from all six on site monitor <br /> wells on June 24, 1991 (MW-1, MW-2, MW-3, MW-4, MW5, and MW6) . <br /> Prior to obtaining the ground water samples each well was purged <br /> using a hand bailer, until the well was depleted (tne Temperature, <br /> pH, and conductivity meter malfunctioned) , approximately 2-3 <br /> gallons of water. The wells were then allowed to recharge and the <br /> samples obtained, see Appendix C. This purged water is presently <br /> being stored on site in 17E 55 gallon drums. <br /> � This sampling round showed that Total Petroleum Hydrocarbons as <br /> gasoline (TFH) has been drastically reduced in the ground water by <br /> vapor extraction, only MW5 exhibits above detection limits at 0.2 <br /> ppm which haus been decreased from 22 ppm as detected during the <br /> March 29, 19411 sampling. Likewise STEN concentrations have been <br /> reduced in MW1 and MWS. Using benzene as the example; the March <br /> 29, 1991 results showed MW1 at 190 ppb and MW5 at 10400 ppb. This <br /> latest results (June 24 19911 showed benzene decreasing to 4.3 <br /> ppb in MW1 and 2 ppb In MW5. Monitor well MW3 showed minor <br /> amounts of benzene (19 ppb) and toluene (2 ppb) and the resampling <br /> } of monitor well MW2 on July 8, 1991 also showed minor amounts of <br /> benzene (0.7) and toluene (5.9 ppb) , see Figure 58. Monitor well <br /> MW2 was resatmpled due to suspect dirty sample containers (Chemtech <br /> reported peaks which fall outside the range of BTEX in their June <br /> 27, 1991 sample report, see Appendix B. This sample was clean of <br /> page 4 <br />