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Langston's Market <br /> I I SOS Seventh Street, Lathrop, California December 12, 1997 <br /> Quarterly Groundwater Sampling Report, November, 1997 Page. 2 <br /> (Revised 1/12/98) <br /> I <br /> Conclusions and Recommendations <br /> An evaluation of the groundwater gradient at this site indicates a gradient swing from the <br /> I southwest to the northeast of approximately 172 over the past 3 1/2 years This seasonal <br /> swing is influenced primarily by open land irrigation, <br /> The groundwater contamination across the site has diminished since December 1995 when <br /> contaminates were identified in EW-1, MW-2 and MW4 September and November 1997 <br /> finds only EW-1 with elevated levels of petroleum hydrocarbons In December 1995, Benzene <br /> I was detected at 5,900 ug/1, Toluene at 2,500 ug/l, Ethyl Benzene at 330 ug/l, Xylene at 2,200 <br /> ug/l and Gasoline at 14,000 ug/l November 1997, data indicates Benzene at 3,900 ug/l, <br /> Toluene at 2,300 ug/l, Ethyl Benzene at 480 uA Xylene at 2,800 ug/l and Gasoline at 9,200 <br /> ug/l Taus small decrease in contaminates is indication possible stabilization of the Petroleum <br /> Hydrocarbon plume Further quarterly monitoring will provide the data to complete this <br /> evaluation. <br /> i <br /> Therefore,AW recommends the following <br /> 1 Continue quarterly groundwater monitoring for 1998 <br /> 2 Conduct a receptor survey with a 2,000'rade to identify any sensitive receptors <br /> 3 Evaluate data from the first and second Quarterly Monitonng events of 1998 and <br /> construct a Mass Balance Calculation and determine the transport and fate of the <br /> plume <br /> IPrepared by <br /> co a V NO <br /> Lee Delano, P E # 22339 22 339 m <br /> California Registered Civil Engineer � exp <br /> `nJy <br /> SOF CAl.1� <br /> W ff Fox, II, REA '��sk: ,�4"` H F0 <br /> a <br /> Registered Environmental Assessor# 00620 , <br /> I No Com � <br /> DP,M&!urnms v,19� <br />