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_ ---- - Report: Groundwater-quality Monitoring—June 23-28,2005, 7500 West Eleventh Street, Tracy, Page 11 that, as SJC has noted in previous reports, agri cultural imgation dominates variations m irri groundwater Tracy via elevations in the area around Tracy. When crops are beingth Delga-tMendot large volumes of water are imported to tcuiltura swellsns being discharged to shallow canal and water pumped from deep agri typically continues through aquifers. This activity begins in the spring of each year and typ Y t the summer, after which it declines and groundwater levels in shallow aquifers begin tin o to fall until some time fall. Except in unusually wet winters, levels usually continuese and fall i the groundwater February or March. Inspection of Table 1 shows that th ttle ;. table elevation beneath the 7500 West Eleventh Street site usually whe ttheirainofalls relationship to seasonal precipitation m the San Joaquin Valley between May and September of each year. p generate Table 1 were used to the groundwater { The groundwater elevations d in contours shown on Figure 2. wells MW-3A, MW-3B and MW-12A were The groundwater elevations in monitoring not considered when the groundwater contours were drawn because the differences between the elevations of the groundwater in Wells MW-3, MW-3A and MW-3B and in eat to indicate that the groundwater monitored MW-12 and MW-12A are sufficiently grdifferent b the shallow well at the locations of each os£in the see cluster.clusters it mut herefore l !, pi zometzic pressure from that of the deeper well be assumed that, at least locally, the shallow wells monitor aquifers different from those monitored by the deeper wells. 2.1.1 Groundwater Mound oundwater contours shown on Figure 2 is the groundwater A significant feature of the grwas first mound centered near Monitoring Well MW Company on The 24 existence °2005 (The S Joaquin observed in the groundwater measurements made ' Company 2405). As was noted at that time, SJC believes that it can be attributed to a l � failing septic tank leach field that is located in an area to the east of the Capitol Furniture building at 7501 West Eleventh Street. on February 24, 2005, the depth to When the groundwater mound was first encountered6ftAlthough that depth had increased to groundwater in Monitoring Well MW 16 wasoundwater mound still 3.5 ft. by June 23, 2005, as can be seen on Figur on of the hehgro groundwater table in the has a significant amplitude above the elevate orin area and has a marked effect on the local directio le of the site aas a whole, :- neighboring at the the area around Monitoringgraundwate°flew remains to the north-northeast at the general direction and gradient approximately 0.003 ft/ft, as generally has been the case throughout the six-year period pp i that groundwater depths have been monitored at the site. 1 2.2 purging of Groundwater-quality Monitoring Wells gr in the After the depths to sixteen groundwater-quality monitoring wells to .._'� sic :.11