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Geologccat7CC1 ucsfnc. Page 2 <br /> Groundwater Monitoring Report <br /> Project No.750.2 <br /> May 13,2004 <br /> 1.0 GROUNDWATER MONITORING <br /> 1.1 Hydrogeology of Site <br /> The dominant soil type in the upper 75-feet of subsurface geologic soils investigated is sand <br /> with fine to coarse-grained texture. Varying amounts of silt, silty sand and laterally <br /> discontinuous clay lenses were encountered from borehole to borehole. A thick clay layer <br /> was encountered starting at 95-feet in SB-101/MW-101 and continues to at least 115-feet. <br /> The average groundwater elevation measured during the March 13, 2004, event was 56.46 <br /> feet above mean sea level (AMSL), which is consistent with previously measured average <br /> elevations at the site. The groundwater elevation increased approximately 0.99 feet since <br /> the December 9, 2003, monitoring event. Depth-to-water measurements averaged 63.64 <br /> feet AMSL. <br /> Groundwater gradients were calculated for the March 13, 2004, groundwater-monitoring <br /> event using MW-1; MW-2 and MW-3. Groundwater was flowing N74°W at 0.0029 ft/ft. <br /> The elevation, gradient and bearing data are summarized in Table 1 of Appendix A. The <br /> groundwater gradient is illustrated on Figure 3: Groundwater Gradient Map. Historical <br /> groundwater directions and gradients are presented in Figure 4: Rose Diagram, which shows <br /> a historically westerly flow direction. <br /> As roun <br /> required under AB2886, the depth to groundwater data was submitted electronically to <br /> q p g Y <br /> GeoTracker on April 15, 2004, with confirmation number 4180332779. <br /> Vertical Groundwater Gradients <br /> For the March 13, 2004, groundwater measurement, the vertical gradient was calculated for <br /> the MW-1/MW-101 pair. The vertical gradient was negative (a downward direction). <br /> However, it was insignificant as head difference between MW-1 and MW-101 was only <br /> 0.02-feet. Generally, the magnitude of the vertical gradient has progressively decreased <br /> since February 2001. <br /> C Figure 2 shows the location of the well cluster used for calculating vertical groundwater <br /> gradient in this report, MW-1 and MW-101. Table 1 shows a summary of groundwater <br /> elevations,bearing and slope. Table 2 shows the calculated vertical gradients. <br /> 1.2 Groundwater Sampling Procedure <br /> LOn March 13, 2004, Don Light of Del-Tech mobilized to the site to conduct a groundwater- <br /> monitoring event. Del-Tech personnel opened the wells and measured the depth to water <br /> C <br />