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Mr Chuck Cannel <br /> May 12, 1992 <br /> Page 2 <br /> Is <br /> Figure 4 presents the TPH-G and BETX concentrations for the January 1992 sampling event <br /> Figure 5 presents a benzene nsoconcentration reap <br /> Benzene concentrations ranged from nondetectable in several wells to 300 micrograms per <br /> liter (pg/1) in ATR-4 TPH-G concentrations ranged from nondetectable in several wells to <br /> 1,200 pg/1 in well ATR-4 The detection limits for the BETX constituents and for TPH-G are <br /> 0 5 and 50 pg/l, respectively <br /> Discussion <br /> The general groundwater flow direction fluctuates from north to east at the site The <br /> hydraulic gradient has ranged from 0 001 to 0 003 The current flow direction to the north <br /> and hydraulic gradient of 0 002 are within the range of previously reported values and are <br /> consistent with recent results The water-level elevation increased in all monxtonng wells <br /> from 0 29 to 0 56 feet since the previous sampling (September 1991) The average depth to <br /> water is 10 67 feet <br /> The concentrations of hydrocarbon constituents in all wells are within the range of previously <br /> reported values of the 11 wells sampled dunng January 1992 Two on-site wells (ATR-4 and <br /> ATR-5) and one off-site well (ATR-8) contained detectable BETX or TPH-G concentrations <br /> Well ATR-3 contained a trace of free product (thickness less than 0 01 feet), which is <br /> consistent with the thickness previously reported <br /> If you have any questions about this January 1992 sampling event, please contact me at (916) <br /> 444-0123 <br /> Sincerely, <br /> BROWN AND CALDWELL CONSULTANTS <br /> RED Gp��, <br /> Jay Lucas, R 1AY RUNG <br /> Project Manager i, ho y�il <br /> JCL SP lrb FCF 7v\. <br /> Enclosures <br /> cc Mr. Gordon Boggs, California Regional Water Quality Control Board <br /> -Mr. Harlin Knoll, San Joaquin County Local Health District <br /> Mr Chns Winsor, ARCO Products Company <br /> i <br /> Brown and Caldwell 673TREP0RTSVAN92QTR-RFr <br /> Consultants <br />