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1 F N <br /> 24 August 1998 j <br /> AGE-NC Project No 96-0232 <br /> t Page 7 of 8 f <br /> shallow ground water monitoring wells MW-1, MW-2, MW-5,, MW-6A, TPH-d was <br /> detected at a concentration of 280 ppb from the deep screened interval at MW-6B <br />' ' MTBE was detected at concentrations up to 810,ppb in samples collected from monitoring <br /> wells MW-1, MW-2, MW-4, MW-6A and MW-7 „ <br /> • MTBE was'detected at 14 ppb in the sample collected from MW-6B, screened between 43 <br /> - and 48 feet bsg - <br /> ' • MTBE concentrations have steadily increased in ground water samples collected from MW-1 <br /> _ between July 1996 to July 1998, <br /> • MTBE concentrations in samples collected from well MW-2,have-sub stantially decreased <br /> between February and July 1998 (Table 2) The decrease in MTBE concentrations reported <br /> from MW-2 may be related to the recent decrease of ground water elevation <br /> " • Field observations and laboratory data indicate that TPH-d and MTBE-impacted soil is <br /> limited to the area near P-1 (Quarterly Report - September 1997, dated 16 October 1997, <br /> concentrations of MTBE detected at 140 ppm from P-1 at 35 feet bsg) <br /> 4 i <br /> MTBE-impacted ground water has migrated to the area of the domestic water well located <br /> west-southwest of the subject site, at a concentration of 8 1 ppb in shallow ground water <br /> 5.0. RECOMMENDATIONS _ <br /> Based upon data collected during June and July 1998, AGE recommends <br /> !} Continued quarterly ground water monitoring and sampling should be performed at the site ` <br /> Sat least through January 1999 to achieve a better u:nderstanding of dissolved TPH-d•and <br /> A MTBE concentrations at the site <br /> Collection of a water sample from the domestic water well located on the Rocky's Restaurant ' <br /> site The samples should be analyzed for MTBE using EPA Method 8260 , <br /> IDetermination of the screened,interval of the Rocky's domestic water well However, If well + , <br /> construction `specifications are unavailable, a submersible camera should be utilized to <br /> investigate the screen interval <br /> • No fiarther subsurface investigation at this time <br /> a , <br /> S <br /> Advanced GcoEmironmental,Inc <br /> y z F t y <br />