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A Z NA FAN <br /> _.......... <br /> Working to Restore Nature <br /> June 1993 Quarterly Groundwater Sampling & Analysis August 16, 1993 <br /> Quik Stop Market No. 132, Stockton, California F7132.93 <br /> approximately 0.016. The flow direction is similar to the December 1992 southerly flow <br /> Idirection (RESNA, January 1993) but different from the March 1993 easterly flow direction <br /> (RESNA, June 1993). Continued monitoring will allow trends to develop. In the local <br /> lower aquifer the flow direction is easterly at a gradient of approximately 0.004. This flow <br /> direction is similar to the easterly flow direction of March 1993 (RESNA, June 1993). <br /> Analysis of the samples collected before and after the May 18, 1993 pumping of MW-5 <br /> found that TPHG and BTEX were not detected in either sampling (see Table 1). Results <br /> of the June 18, 1993 groundwater sampling found that TPHG and BTEX were not detected <br /> in groundwater samples from monitoring wells MW-1R, MW-2, MW-6, and MW-7. Wells <br /> MW-3 and MW-4 were not sampled due to historical nondetectable results. BMW <br /> contain-d -deti�ctable-'levels of'TPHG at=504_ppb,_and, benzene at 1:0'ppb:i _ <br /> In the June 18, 1993 analysis, the presence of a discrete peak was reported by the laboratory <br /> for groundwater samples from MW-5. From previous experience we have found that such <br /> a peak can be caused by the presence of methyl-tert-butyl-ether (MTBE). MTBE is a non- <br /> metallic (lead-free) anti-knock compound used in lead-free gasoline. In addition, in our <br /> sampling and analysis of September 22, 1992, samples from MW-5 were analyzed for MTBE. <br /> 1 MTBE was detected in the groundwater samples from MW-5 at 920 ppb, (see Table 1). In <br /> light of the detection of gasoline related compounds in MW-5, the presence of such a <br /> compound is not unexpected. The next quarterly groundwater sampling will be conducted <br /> in September 1993. <br /> Reporting Requirements <br /> A copy of this report should be forwarded by Quik Stop Markets, Inc., to the following <br /> agencies in a timely manner. <br /> • San Joaquin County <br /> Public Health Services <br /> Environmental Health Division <br /> P.O. Box 2009 <br /> Stockton, California 95201 <br /> Attention: Mr. Michael Collins, R.E.H.S. <br /> Environmental Health Specialist <br /> • California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road <br /> Sacramento, California 95827-3098 <br /> Attention: Ms. Elizabeth Thayer <br /> 3 <br />