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1 Geolagtcal r hides ur- Page 4 Groundwater Morutonng Report Project No 425 2 Apn127,2006 ' • The lithologY between 40 and 80-feet bgs is comprised of alternating layers of clay-sand mixtures and sand-gravel mixtures approximately 2 to 8 feet in thickness ' 1.4 Hydrology of Site Y �Y 1.4.1 Zone Divisions To define the site more accurately, the aquifer is divided into four zones (Zones A through D) ' defined by the screen intervals of the sixteen monitoring wells associated with the site Zone divisions and well construction are summarized in Table 1 • Zone A includes monitoring wells screened between 5 and 22-feet bgs • Zone B includes monitoring wells screened between 32 and 35-feet bgs • Zone C includes monitoring wells screened between 45 to 49 5-feet bgs • Zone D is represented by MW-202 screened between 79 and 81 5-feet bgs ' In accordance with the requirements in AB2886, the depth-to-water measurements were uploaded to the GeoTracker system on April 26, 2006 The confirmation number is ' 2050750553 1.4.2 Horizontal Groundwater Gradients M Zone A The average groundwater elevation for the January 2006 monitoring event is 73 54 feet above mean sea level (AMSL) This represents a decrease in elevation of 0 46 feet since the October 30, 2005 monitoring event The zone-specific groundwater gradient and bearing was 0 0007 ft/ft and N 17°E, respectively The contours generated by Surfer 7 00 show that the ' groundwater moves N39°W at 0 0019 ft/ft in the southern half of the site and than rotates to a bearing of N17°E in the northern half of the site A review of historical groundwater data in Zone A show groundwater bearing and slope average N 18°E at 0 0012 ft/ft, respectively Table 2 of Appendix A summarizes Zone A groundwater elevations, gradients and bearings Figure 3 illustrates the January 22, 2006 groundwater gradient for Zone A Figure 4 is a rose diagram summarizing historical groundwater bearing and slope information Zone B ' The average groundwater elevation for the January 2006 monitoring event is 73 66 feet AMSL and indicates a decrease of 0 41 feet from the previous monitoring event The groundwater gradient and bearing for Zone B during the January 22, 2006 monitoring event was 0 0030 ft/ft flowing N79°W, respectively The predominant groundwater flow is to the north-northwest with the slope averaging 0 0062 ft/ft Table 3 of Appendix A summarizes Zone B groundwater data and Figure 5 shows the groundwater gradients for January 22, 2006 groundwater monitoring event Figure 5 is a rose diagram summarizing historical groundwater bearing and slope information