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Wm. I Hunter & Associates 2220 Loma Vista Dr. Registered Geologists Sacramento, CA 95825 Petroleum & Mineral Appraisers (916) 972-7941 FAX (916) 972-1683 June 27, 1996 Steven Sasson, REHS San Joaquin County PHS Environmental Health Division 445 No. San Joaquin Street Stockton, CA 95202 Ref : Seventh Quarterly Groundwater Monitoring Report for 921 W. Fremont Street, Stockton. Dear Mr. Sasson; We have enclosed a copy of the field report, water analysis results, and a gradient map for the above property. The work was performed on March 14, 1996 by Del-Tech Geotechnical Support Services as directed by our office . The attached PLATE I shows the direction of the groundwater gradient indicated by the eight (8) measurements taken to date. The most recent data indicates a reversal of the hydraulic gradient to the south; all previous measurements showed a north/ .� northeast direction. The hydraulic gradient has flattened to . 671 /1001 , or about 35 ' /mile . The results of the laboratory anayzes of water samples collected since monitoring began are shown on TABLE I . Monitoring wells #1 & #3 are below detection levels for BTEX & TPHg. MW-2 continues to record significant amounts of BTEX & TPHg. MBTE was below detection limits in all three wells . The water table was measured at an average depth of 8 . 18 ' bgs during the December sampling event . This is a rise in over 4 feet in approximately 3 months, and the highest since monitoring began in March, 1994 . CONCLUSIONS : 1 . The hydraulic gradient during this latest sampling has shifted 180 degrees from north to south. This is the first time that has occurred since monitoring began. The significance of this reversal is unknown at this time since MW-1, the closest to the removed UST and in a downgradient position during this - sampling event, did not record any contamination. 2 . MW-2 continues to record relatively high levels of BTEX & TPHg; MBTE was below detection limits . 1