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QUARTERLY GROUNDWATER MONITORING REPORT <br /> 3725 Tracy Boulevard Tracy Calrtorma <br /> 1 <br /> In July 1990, MW-1, MW-2, and MW-3 were abandoned during station reconstruction <br /> The wells were replaced near the original monitoring well locations with wells MW-1A, <br /> MW-2A, and MW-3A in August 1990 Soil boring samples were collected and submitted <br /> to an analytical laboratory The results for petroleum constituents were BDL for TPH, as <br /> gasoline, and BTEX, except in MW-2A at 5 0 feet below grade (0 013, 0 052, and 2 2 ppm <br /> ethylbenzene, total xylenes, and TPH, as gasoline, respectively)(Delta report to Shell <br /> dated November 28, 1990) <br /> The original monitoring wells were apparently monitored and sampled only once in <br /> September 1989 In July 1990, the original monitoring wells were abandoned and the <br /> replacement wells were installed in August 1990 Delta began a program of quarterly <br /> measurements of depths to and sampling of groundwater following installation of the <br /> replacement wells Emcon was retained by Shell in January 1992 to collect quarterly <br /> groundwater depth measurements and groundwater samples from the wells on site The <br /> data collected by Emcon, including the laboratory analytical results, were provided to <br /> IAegis for inclusion in this report (Appendices A and B) <br /> 4 0 GROUNDWATER MONITORING <br /> 4.1 Groundwater <br /> On February 14, 1992, Emcon personnel collected measurements of the depths to <br /> groundwater in wells MW-1A, MW-2A, and MW-3A, according to the Emcon sampling <br /> procedures (SP) included in Appendix A Water level measurements collected during the <br /> last year are summarized in Table 1 A groundwater elevation hydrograph is included as <br /> Figure 3 and a contour map of the potentiometnc surface on February 14, 1992, is <br /> included as Figure 4 <br /> Groundwater levels have risen in all three wells an average of approximately 0 82-feet <br /> since November 1991 On the basis of the February 14, 1992, measurements, <br /> groundwater is estimated to flow to the east (Figure 4) at an average gradient of <br /> approximately 0 003 ft/ft Delta reported the direction of groundwater flow was to the east <br /> on November 21, 1991 <br /> I <br /> 90 089A OMR 2 <br />