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Langston Is Market ' 156.15 Seventh Stree4 Lathrop, California IQuarterly Groundwater Sampling Report Augus4 1996 I I Narrative ' On August 1, 1996, WHF Inc , in conjunction with HKM Groundwater Monitonng, conducted field measurements, well pumping and groundwater sampling on four (4) ' groundwater monitoring wells located at this site (Figures 1 & 2) Sampling was conducted on a later date due to scheduling complications with I KM Environmental, Inc ' Groundwater elevations were taken from four (4) wells prior to pumping (Table 1 & Appendix B) Monitoring wells EW-1 (also referred to as MW-1), MW-2 through MW-4 were evacuated by means of a steam-cleaned, stainless steel bladder type pump During the three (3) volume pump down samples were collected to measure field pH, electrical conductivity and temperature (Table 3 & Appendix B) A minimum of three (3) well volumes were removed and the samples were collected with a steam-cleaned disposable ' bailer The samples were then labeled and placed 1n an ice chest cooled with Blue Ice® The samples and trip blank were then logged on a Cham of Custody (Appendix A) and ' transported to a State-certified laboratory, California Laboratory Services, Inc , in Rancho Cordova, California The analysis requested for the water samples was EPA method 602 for BTX&E/MTBE (Benzene, Toluene, Xylene, and Ethylbenzene / Methyl t-butyl ether) ' and EPA method 5030/LUFT for Gasoline The analytes and concentrations detected are listed in Table 2 of this report Groundwater Gradient ' The water level measurements from monitoring wells EW-1, MW-2 through MW4 were used to construct a groundwater gradient map and calculate the gradient (Figure 3) The ' current gradient is 0 0010 ft/ft at S21°E Static water levels have risen an average of 2 06 feet across the site Historical gradient maps are included in Appendix C 1 1 1