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' Lang ston's Market <br /> 15615 Seventh Street; Lathrop, California December 12, 1997 <br /> ' Quarterly Groundwater Sampling Repor4 November, 1997 Page: 2 <br /> ' Conclusions and Reconnmendations <br /> ' An evaluation of the groundwater gradient at this site indicates a gradient swung from the <br /> southwest to the northeast of approximiately 1720 over the past 3 1/2 years This seasonal <br /> swing is influenced primarily by open land ungation_ <br /> ' The8r oundwater contanunatnon across the site has diminished since December 1995 when <br /> contaminates were identified in EW-1, MW-2 and MW-4 September and November 1997 <br /> finds only EW-1 with elevated levels of petroleum hydrocarbons In December 1995, Benzene <br /> was detected at 5,900 ug/l, Toluene at 2,500 ug/l, Ethyl Benzene at 330 ug/l, Xylene at 2,200 <br /> ug/1 and Gasoline at 14 mg/k November 1997, data indicates Benzene at 3,900 ug/!, Toluene <br /> ' at 2,300 ug/l, Ethyl Benzene at 480 ug/l, Xylene at 2,800 ug/l and Gasoline at 9 2 mg/l This <br /> 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 /> ' Therefore,WHF recommends the following <br /> 1 Continue quarterly groundwater monitoring for 1998 <br /> 2 Conduct a receptor survey with a 2,000'radu to identify any sensitive receptors <br /> 3 Evaluate data from the first and second Quarterly Monitoring events of 1998 and <br /> construct a Mass Balance Calculation and determine the transport and fate of the <br /> plume <br /> Prepared by <br /> QROFESsjp <br /> co' NO <br /> v `G 022 339 <br /> Lee eLano, P E # 22339 <br /> �� Exp 9.30,0/ <br /> California Registered Civil Engineer <br /> ' CA <br /> ' ��vjRoN.Ss y�A <br /> W H Fox, II, REAS <br /> ' Registered Environmental Assessor# 00620 <br /> No 00620 <br /> Expires.June 30,199 <br /> Q tY0��1P <br /> F CAL <br />