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Langston's Market <br /> 15615 Seventh Street, Lathrop, California April 1.3, 1998 <br /> Quarterly Groundwater Sampling Repor4 March, 1998 Page: 2 <br /> Conclusions and Recommendations <br /> An evaluation of the groundwater gradient at this site indicates a gradient swing from the <br /> southwest to the northeast of approximately 172° over the past 3 112 years This seasonal <br /> swing is influenced primarily by open land irrigation and seasonal rainfall <br /> fThe groundwater contamination across the site has diminished since December 1995 when <br /> contaminates were identified m EW-1, MW-2 and MW-4 September and November 1997 <br /> and March, 1998 finds only EW-1 with elevated levels of petroleum hydrocarbons In <br /> December 1995, Benzene was detected at 5,900 ug/l, Toluene at 2,500 ug/l, Ethyl Benzene at <br /> 330 ug/1, Xylene at 2,200 ug/1 and Gasoline at 14,000 ug/l March, 1998, data indicates <br /> Benzene at 770 ug/l, Toluene at 440 ugh,Ethyl Benzene at 97 ug/l, Xylene at 510 ug/l,MTBE <br /> at 37 0 ug/I and Gasoline at 2,400 ug/l This decrease in contaminates is indication possible <br /> stabilization of the Petroleum Hydrocarbon plume Further quarterly monitoring will provide <br /> the data to complete this evaluation <br /> Therefore, WHF recommends the following <br /> 1 Continueuarterl groundwater monitoring for 1998 <br /> q Y <br /> 2 A receptor survey with a 2,000'rade to identify any sensitive receptors ism <br /> progress <br /> 3 Evaluate data from the first and second Quarterly Monitoring events of 1998, <br /> construct a Mass Balance Calculation and determine the transport and fate of the <br /> plume <br /> IPrepared by QROFESSIpy <br /> CID N0 <br /> I 22 339 O m <br /> �} F-XP 9,30-d/ a <br /> Lee DeLano, P E # 22339 CfV14 <br /> qj� <br /> California Registered Civil Engineer Or V1R01V.1� <br /> Q <br /> NO 0052O � <br /> I W H Fo , II REA Expires Junta 30,ig ' <br /> x, , <br /> Registered Environmental Assessor# 00620 'r1P <br /> Uri140 <br />