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Geological TeCluiics/ac. Page 2 Groundwater Monitoring Report Project No.750.2 _ — August 30,2004 1.0 GROUNDWATER MONITORING V 1.1 Hydrogeology of Site r The average groundwater elevation measured during the May 7, 2004, event was 55.94 feet above mean sea level (AMSL), which is consistent with previously measured average elevations at the site. The groundwater elevation increased approximately 0.99 feet since the December 9, 2003, monitoring event. Depth-to-water measurements averaged 63.64 feet AMSL. Groundwater gradients were calculated for the May 7, 2004, groundwater-monitoring event using MW-1, MW-2 and MW-3. Groundwater was flowing N83°W at 0.0028 ft/ft. The elevation, gradient and bearing data are summarized in Table 1 of Appendix A. The groundwater gradient is illustrated on Figure 3: Groundwater Gradient Map. Historical groundwater directions and gradients are presented in Figure 4: Rose Diagram, which shows a historically westerly flow direction. As required under AB2886, the depth to groundwater data was submitted electronically to GeoTracker on July 1, 2004,with confirmation number 7617405533. Vertical Groundwater Gradients �-... For the May 7, 2004, groundwater measurement, the vertical gradient was calculated for the MW-1/MW-101 pair. The vertical gradient was negative (a downward direction). However, it was insignificant as head difference between MW-1 and MW-101 was only 0.01-feet. r Generally, the magnitude of the vertical gradient has progressively decreased since February 2001. Figure 2 shows the location of the well cluster used for calculating vertical groundwater gradient in this report, MW-1 and MW-101. Table 1 shows a summary of groundwater elevations,bearing and slope. Table 2 shows the calculated vertical gradients. 1.2 Groundwater Sampling Procedure On May 7, 2004, Don Light of Del-Tech mobilized to the site to conduct a groundwater- monitoring event. Del-Tech personnel opened the wells and measured the depth to water with an electrically actuated sounding tape. The water level reading was recorded to an accuracy of 0.01 foot. No floating product was detected during the monitoring event. Stagnant water in the well casing was purged using a Waterra© pump and dedicated tubing. The rate of well purging was monitored. The well was purged of at least three casing volumes until the groundwater parameters (temperature, conductivity and pH) had stabilized (Appendix Q indicating that water representative of actual aquifer conditions was entering