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4 <br /> BENZENE TOLUENE E .BENZENE XYLENE TPHg TPHd <br /> SB-1 <br /> 66 ' (ppm) < . 51 < .51 < . 51 < . 51 72 . 7 3480 <br /> 711 (ppm) <1 . 3 <1 . 3 <1 . 3 1 . 6 14 . 1 18000 <br /> MW-1 @ 68 ' <br /> w. (ppb) ND< .3 ND< . 3 ND< . 3 0 . 8 222 ND<50 . <br /> (ppm) ND< . 003 ND< . 003 ND< . 003 0 . 008 0 .222 ND< . 05 <br /> SUMMARY AND CONCLUSIONS : <br /> Based upon an analysis of all of the data obtained to date, the <br /> following summary & conclusions appear warranted; <br /> 1 . The hydraulic gradient is highly divergent, indicating a very <br /> restricted aquifer that is not influenced by regional flow. <br /> 4 <br /> 2 . The maximum change in the potentiometric surface since <br /> monitoring began in April, 1992 is 6 .311 , supporting the evidence <br /> of a very restricted aquifer. <br /> 3 . As the table above shows, the permeability of the soil is <br /> extremely low. The level of xylene measured in the water is <br /> �.. 1/200th of the amount in the soil 20 ' away. TPHg measured in the <br /> water is about 1/63rd the amount in the soil . TPHd in the soil <br /> was measured at 18, 000 ppm; it is below detection levels in the <br /> ` water. <br /> 4 . The large volume of data collected to date at this site <br /> indicates that the minor amounts of contamination measured in the <br /> groundwater from MW-1 has remained at very low levels since <br /> monitoring began. Benzene has not been detected in the last <br /> seven (7) monitoring events, and Toluene has never been found. <br /> L, Ethylbenzene has been measured only once, at 0 .4 ug/L. Xylene <br /> has been detected three times; at 27 ug/L in June, 1993, 1 . 3 ug/L <br /> in October, 1996, & 0 . 8 ug/L in November, 1996 . TEPH as diesel <br /> was found only three times; in September, 1992 (0 . 11 ug/L, ) June, <br /> 1993 (3 . 0 ug/L, ) and November, 1994 0 .34 ug/L. TPH as gasoline <br /> was ND in April & May, 1992 , and was not tested until the latest <br /> sampling. <br /> RECOMMENDATION: <br /> r. Based upon an analysis of all of the extensive data collected at <br /> this site, we believe that the site has been fully and thoroughly <br /> characterized, and that continued monitoring is not justified. <br /> Therefore, we recommend that the three wells on the property be <br /> 6— destroyed, all remaining stored soil & water be properly disposed <br /> �. 2 <br />