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Report:Groundwater-quality Monitoring_December 20-2I,2005, 7500 West Eleventh Street, Tracy, Cit. Page 11 2.1.1 Groundwater Mound A significant feature of the groundwater contours shown on Figure 2 is the groundwater mound centered near Monitoring Well MW-16. The existence of that mound was first observed in the groundwater measurements made on February 24, 2005 (The San Joaquin Company 2006c). As was noted at that time, SJC believes that it can be attributed to a failing septic tank leach field that is located in an area to the east of the Capitol Furniture building at 7501 West Eleventh Street. The depth to groundwater in Monitoring Well MW-16 on December 20, 2005 was measured at 4.05 ft. BGS, which is 2.60 ft, higher than the depth to groundwater last measured in that well on October 20, 2005. However, the December 2005 amplitude of the groundwater mound was not as great as when it was first observed in February 2005 when the depth to groundwater in Monitoring Well MW-16 was only 2.6 ft. The presence of the groundwater mound remains a striking feature of the groundwater contours in the area north of West Eleventh Street, as is the highly complex pattern of groundwater contours to the south of the groundwater mound that were first observed during the ..r October 2005 round of groundwater monitoring. • Despite the continuing presence of the mound of groundwater, at the scale of the site as a whole, the general direction and gradient of groundwater flow remains to the north- northeast at approximately 0.003 ft/ft, as generally has been the case throughout the six- year period that groundwater depths have been monitored at the site. 2.2 Purging of Groundwater-quality Monitoring Wells After the depths to groundwater in the seventeen groundwater-quality monitoring wells to be sampled were measured, a small-diameter, submersible pump was used to purge each of stagnant water. The pumped water was discharged into 5-gallon pails, each of which was, in turn, discharged into a 55-gallon drum. The water in the drum was periodically discharged into a 1,100-gallon holding tank on the 7500 West Eleventh Street property. During the purging procedure, the temperature and electrical conductivity of the stream of purge water were monitored by checking those parameters periodically using a multi- function electronic meter. Purging continued until both parameters stabilized (i.e., �.. variations between measurements were less than 10%) or, in the case of wells screened above the water table, until a minimum of 15 gallons of groundwater had been removed, whichever was greater. The array of parametric results for each well is recorded in SJC's `l field notes (see Field Notes, Appendix A). 2.2.1 Disposal of Purge Water As noted above, purge water extracted from the monitoring wells was discharged periodically into in a 1,100-gallon storage tank located on the Navarra Site. For economy ;— and efficiency, water will be held in that tank until it is full. It will then be pumped into a vacuum truck and transported to a recycling facility, where the petroleum hydrocarbons sic