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1 <br /> CC04vgual rech,ucs 11cc Page 2 <br /> t 4"'Quarter 2001 Groundwater Monitoring Report <br /> h Project No 507 2 <br /> r' January 17,2002 <br /> On December 20, 2001, the wells were re-surveyed in accordance with the Geotracker <br />' requirements by Thompson-Hysell Engineering of Modesto, CA The groundwater levels in <br /> these wells were also sounded on this date For this second December 2001 event, the <br /> average groundwater elevation at the site was —11 73 feet mean sea level (msl) and the <br />' groundwater flow was N55°E at 0 001 ft/ft Vertical groundwater gradient calculations <br /> between MW-9 & 109 indicated that groundwater was flowing downward at approximately <br /> four times horizontal gradient <br /> 1.0 GROUNDWATER MONITORING <br /> 1.1 H dro Bolo of Site <br /> Y g g.Y <br /> The geology of the site is predominately clays and sandy clays with lesser amounts of silts <br /> and sands The average groundwater elevation was —8 38 feet below MSL on December 4, <br /> 2001 This represents an increase of 124 feet since the September 2001 monitoring event <br /> A groundwater gradient was calculated for the event and found to be flowing N4°W at <br /> 0 001 ft/ft <br /> On December 20, 2001, the wells were re-surveyed in accordance with the Geotracker <br /> requirements by Thompson-Hyseli Engineering of Modesto, CA The wells were also <br /> sounded and the average groundwater elevation at the site was —10 66 feet mean sea level <br /> (msl) and the groundwater flow was N55°E at 0 001 ft/ft This represented an increase of <br /> 0 23 feet since the previous event (data normalized to the December 20, 2001 survey) <br />' Theradient direction for the December 4 and <br /> g December 20 monitoring events are shown <br /> in Figures 2 and 3, respectively, and the historical groundwater directions and gradients are <br /> shown in Figure 4, Groundwater Gradient Rose Diagram The groundwater elevation data <br /> are summarized in Table 1, Appendix A Table 5 provides a summary of monitoring well <br /> construction <br /> The groundwater gradient is relatively flat and the direction of groundwater has vaned <br /> during the course of the investigation As evident in Figure 4, groundwater had a strong <br /> bifurcated flow regime, trending predominantly to the southwest or north-northeast at <br /> approximately 180-degree direction reversal With the installation of wells MW-7 and <br />' MW-10 in May 2001, the direction had been to the east-northeast for two consecutive <br /> events in June and September For the two December events, a 59-degree shift to the east <br /> was experienced in a Iittle over two weeks The site is quite close to the San Joaquin River <br /> and tidal fluctuations may contribute to some of the observed changes in groundwater <br /> direction <br /> i <br />