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Mr Chuck Carmel <br /> June 14, 1993 <br /> Page 2 <br /> Analytical results of groundwater samples are summarized in Table 3 The complete <br /> laboratory report for the sampling event is presented in Exhibit A Figure 2 shows TPH-G <br /> and BETX concentrations for the April 14 1993 sampling event Figure 3 is a benzene <br /> isoconcentration map <br /> Benzene concentrations ranged from nondetectable in several wells to 160 micrograms per <br /> liter (pg/i) in ATR-4 TPH-G concentrations ranged from nondetectable in several wells to <br /> 810 pg/l in wells ATR-4 and ATR-5 The detection limits for the BETX constituents and for <br /> TPH-G are 0 5 and 50 pg/l, respectively Approximately 0 02 feet of free product was <br /> measured in ATR-3 <br /> Discussion <br /> Water level elevations have decreased an average of 0 46 feet across the site since <br /> January 18, 1993. The east-northeastern groundwater flow direction and the hydraulic <br /> gradient (0 003) are consistent with previously reported data <br /> Concentrations of hydrocarbon constituents are nondetectable or dust above detection limits <br /> in on-site monitoring wells ATR-1, ATR-2, and ATR-7 and off-site monitoring wells ATR-9 <br /> through ATR-12 BETX and TPH-G concentrations in wells ATR-4, ATR-5, and ATR-8 are <br /> within the range of previously reportc d N :.'ues. The benzene and TPH-G concentrations in <br /> the sample from ATR-6 are higher than f,�eviously reported concentrations. Well ATR-3 has <br /> not been sampled since the fourth quarter of 1991 due to a trace of free product (thickness <br /> approximately 0 02 feet) found each quarterly sampling penod <br /> If you have any questions about the April 1993 sampling event, please contact me at <br /> (916) 444-0123. <br /> Sincerely, <br /> BROWN AND CALDWELL CONSULTANTS <br /> _�L4 u� <br /> Jay C. Lucas, R G. <br /> Project Manager <br /> JCL SP lk <br /> Enclosures <br /> cc. Mr Gordon Boggs, California Regional Water Quality Control Board <br /> /ThisMr Harlin Knoll, San Joaqum County Local Health District L,-- <br /> This <br /> report was prepared in accordance with the standards of the environmental consulting industry at the time it was prepared It <br /> should not be relied upon by parties other than those for whom it was prepared and then only to the extent of the scope of work which <br /> was authorized This report does not guarantee that anv additional environmental condinons beyond that described in this report exist <br /> at this site <br /> 7443,RF.PORTS�APR93QTR RPT <br /> Brown and Caldwell <br /> Consuitants <br />