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SECTION 2 Base and Final Grading s 2.1 General The limits of WMU FU-14 were determined based on the site's operational needs, the landfill site development plan (BAS et al., 2003), and the March 2013 site topographic map. The eastern and southern limits were set based on site operational considerations for airspace and refuse fill stability considerations. The southern boundary of WMU FU-14 will eventually be connected to landfill modules to the south. The northern boundary of WMU FU-14 connects to WMU FU-13. The western boundary of WMU FU-14 connects to WMUFU-10. The WMU FU-14 grading plan and liner and LCRS sections and details are included in the Construction Drawings for the development of WMU FU-14 (Appendix A). Permanent access roads and surface drainage facilities will be constructed as the WMU meets final grades. 2.21 Liner and LCRS Grades Design criteria and reasoning to develop the grading plan includes: • Title 27 requires a minimum 5-foot barrier between waste in WMU FU-14 and groundwater. Based on the "Forward Landfill Groundwater Elevation Evaluation East of WMU FU-06" and the "Forward Landfill Expansion, Groundwater Elevation Evaluation" (GeoLogic Associates, 2007) (see Appendix B), the maximum high groundwater elevation underlying the area east of WMU FU-06 is anticipated to be minus 6-feet MSL. The lowest elevation of the WMU FU-14 base lining system is 8-ft MSL (at the top of operations layer) and is located at the eastern boundary. This elevation is approximately 14-feet above the historic high groundwater elevation. • WMU FU-14 will be graded to drain to east-west trending leachate collection pipes that lead to temporary sumps. The maximum drainage distance to the pipe is approximately 150 feet(see the Construction Drawings in Appendix A). • As outlined in the Preliminary Closure and Postclosure Maintenance Plan(CH2M HILL, 1994e), abrupt differential foundation settlement is not anticipated in the onsite soils forming the base grades of the landfill. The estimated maximum differential foundation settlement is 2 feet in 550 feet, or approximately 0.36 percent. Since the minimum drainage grades on the base of WMU FU-14 are 1 percent and the net effective slope to the LCRS pipes is at least 2 percent, positive drainage grades would remain even if the estimated maximum differential settlement were to occur. • The WMU FU-14 liner and LCRS will be connected to the WMU FU-10 and WMU FU-13 liner and LCRS and leachate from WMU FU-10 will be routed to the WMU FU-14 sumps. A portion of WMU FU-14 LCRS drains north into the WMU FU-13 cell. WMU FU-14 REPORT.DOC 2-1