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t Stockton City Taxi Company 2085 E. Fremont Street Stockton, California 1 Quarterly Groundwater Sampling Report ' January, 2004 1 Narrative 1 On January 29, 2004, GeoAnalytical Laboratories, Inc., conducted field measurements, ' well pumping and groundwater sampling on four (4) groundwater monitoring wells located at this site (Figures 1 and 2). ' Groundwater elevations were taken from,four (4) wells prior to pumping (Table 1 & Appendix B). Monitoring wells MW-1 through MW-4 were evacuated by means of a steam-cleaned, stainless steel bladder type pump. During the three (3) volume pump ' down of each well, samples were collected to measure field pH, electrical conductivity and temperature (Table 3 & Appendix B). Once stability was achieved, a minimum of three (3) well volumes were removed and samples were collected with a disposable bailer. The samples were then labeled and placed in an ice chest cooled with Ice®. The samples were then logged on a Chain of Custody (Appendix A) and transported to ' the State-certified laboratory, GeoAnalytical Laboratory Inc., in Modesto, California. The analysis requested for the four (4) water samples were EPA method 8260B for BTX&E (Benzene, Toluene, Xylene, and Ethyl-Benzene), MTBE, ethanol, tert-Butanol, DIPE, ' ETBE, TAME, EDB, and 1,2-DCA, and EPA method GCFID (5030/Luft) for gasoline. The analytes and concentrations detected are listed in Table 2 of this report. Groundwater Gradient ' The water level measurements from three (3) monitoring wells were used to construct a' groundwater gradient map (Figure 3). MW-4 was not used in the gradient calculation ' since it is a deep well. This quarter, the groundwater gradient trend is South 510 East with a downward slope of 0.0028 ft/ft. Historical groundwater gradient maps are provided for reference in Appendix C.