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Boyett Petroleum 419 Main Street, Manteca, California Quarterly Groundwater Sampling Report ' December, 1999 Narrative ' On December 10, 1999, GeoAnalytical Laboratories, Inc., conducted field measurements, well pumping and groundwater sampling on four (4) groundwater monitoring wells ' located at this site (Figures I 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 Blue Ice®. lie 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 was EPA method 602 for BTX&E (Benzene, Toluene, Xylene, and Ethyl-Benzene) and MTBE (Methyl Tertiary Butyl Ether) and EPA method GCFID (5030/Luft) for gasoline. MTBE contamination was confirmed ' by EPA method 8260. The analytes and concentrations detected are listed in Table 2 of this report. Groundwater Gradient The water level measurements from three (3) monitoring wells (MW-1, MW-2, MW-3) were used to construct a groundwater gradient map (Figure 3). This quarter, the ' groundwater gradient trend is North 60° West with a downward slope of 0.001 ft/ft. Since the sampling event on September 27, 1999, the groundwater has risen an average of 0.63 feet or 7.56 inches. Historical groundwater gradient maps are provided for reference ' in Appendix C. k '