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Langston Is Market <br /> r15615 Seventh S&ee4 Lathrop, California <br /> I Quarterly Groundwater Sampling Report <br /> November, 1997 <br /> (Revised 1/12/98) <br />' Narrative <br /> On November 25, 1997, WHF, Inc , in conjunction with HKM Environmental, Inc , <br /> conducted field measurements, well pumping and groundwater sampling on four (4) <br /> groundwater monitoring wells located at this site (Figures 1 & 2) <br /> Groundwater elevations were taken from f r 4 <br /> efour Owells prior to pumping (Table 1 & <br />' Appendix B) Monitoring wells EW-1, also referred to as MW-1, MW-2 through MW-4 <br /> were evacuated by means of a steam-cleaned, stainless steel bladder type pump During <br /> the three (3) volume pump down samples were collected to measure field pH, electrical <br /> conductivity and temperature (Table 3 & Appendix B) A minimum of three (3) well <br /> volumes were removed and the samples were collected with a steam-cleaned disposable <br /> bailer The samples were then labeled and placed in an ice chest cooled with Blue Ice® <br /> The samples and trip blank were then logged on a Chain of Custody (Appendix A) and <br /> transported to a State-certified laboratory, California Laboratory Services, Inc , in Rancho <br /> Cordova, California The analysis requested for the water samples was EPA method 602 <br /> for BTX&E and EPA method 5030/LUFT for gasoline The analytes and concentrations <br /> detected are listed m Table 2 of this report <br /> Groundwater Gradient <br /> The water level measurements from three (3) of the four (4) monitoring wells, MW-2, 3 <br /> and 4, were used to construct a groundwater gradient map and calculate the gradient <br /> (Figure 3) EW-1 was not used in the gradient calculation nor the construction of the <br /> groundwater gradient map The current gradient is 0 00047 ft/ft to the S 10°W direction <br /> Historical gradient maps are included in Appendix C <br /> ISummary ofAnalytrcal Findings <br /> One well had detectable amounts of contamination this quarter (Table 2) MW-1 (EW-1) <br /> tested 3,900 pg/l Benzene, 2,300 µg/1 Toluene, 480 pg/l E Benzene, 2,800 µg/l Xylene and <br /> 9,200 ug/l Gasoline, MW-2, MW-3 and MW-4 were free of Petroleum Hydrocarbon <br /> contamination Overall contaminant concentrations have increased since the last sampling <br /> event Past analytical data is included in Table 2 for comparison <br /> I <br />