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Report• Groundwater quality Monitoring—October 20-21,2005, 7500 West Eleventh Street, Tracy, CA. Page 10 <br /> Thus, the estimated specific gravity of the floating product in well MW-7 is: <br /> PP =0.79 <br /> The depression in the elevation of the water table due to the presence of floating product <br /> is given by: <br /> } ' W=T / (Equation 1) <br /> Where: <br /> W= the depression of the water table <br /> T = the thickness of floating product in the monitoring well <br /> pW = the specific gravity of the groundwater <br /> PP= the specific gravity of the floating product <br /> Thus, in the case of the floating product measured in well MW-7 on October 20, 2005: <br /> W=0.14 (0.7911.0)= 0.11 ft. <br /> Accordingly, when drawing the contours shown on Figure 2, the elevation of the <br /> groundwater in well MW-7 was adjusted by 0.11 ft. based on an assumed depth to <br /> groundwater 0.11 ft. higher than that actually measured. <br /> !'t In the period from June 23, 2005, the date on which the depths to groundwater in the <br /> -' monitoring wells were last measured to October 20 2005 the <br /> groundwater table in the <br /> majority of wells that are screened in the near-surface aquifer beneath the site fell <br /> between 0.5 ft. and 1.0 ft. (See Figures 4 through 9 for aquifers and well screen <br /> intervals.) As has been observed on previous occasions, the fall in the groundwater table <br /> observed in the wells in the approximate southern half of the well array was somewhat <br /> greater than the fall observed in the northern half of the monitored area. In the monitoring <br /> wells that are screened in the first aquifer that is located deeper than the near-surface <br /> aquifer (i.e., Monitoring Wells MW-3A and 12A), the piezometric head fell, on average, <br /> k> by 0.93 ft. In the deepest aquifer that is monitored at the site (by Monitoring Well MW- <br /> 3B), the piezometric head fell by 0.49 ft. <br /> The observed changes in the general depths to groundwater in the groundwater-quality <br /> monitoring wells that were observed between June and October 2005 reflect the fact that <br /> agricultural irrigation dominates variations in groundwater elevations in the area around <br /> k Tracy. When crops are being irrigated, very large volumes of water are imported to the <br /> fields around Tracy via the Delta-Mendota canal and water pumped frorn deep <br /> agricultural wells is being discharged to shallow aquifers. This activity begins in the <br /> sic <br /> r <br />