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3.0 CLOSURE LAN 3.1 INTRODUCTION The Stage IA partial closure of the Forward Landfill will be performed in accordance with the applicable regulatory standards included in 27 CCR, Chapters 3 and 4 and 40 CFR, Subpart F. The costs associated with the closure of Stage IA are described in Section 6.0 of this document. The improvements and systems required for the closure of Stage IA include the final cover and final grading plan, supported by landfill settlement and slope stability analyses, drainage and erosion control systems, landfill gas control and monitoring systems, groundwater/surface water monitoring system, and decommissioning of environmental control systems. A description of these closure improvements as well as a schedule for construction is presented in the following subsections. 3.2 FINAL COVER The purpose of a final cover is to provide long-term minimization of surface water intrusion, to isolate wastes from the ground surface, and to reduce the potential for odors and gas emissions. The cover also provides a base for vegetation, which will reduce drainage velocities and erosion. In addition, the final cover configuration is designed to accommodate settlement, subsidence and the effects of seismic events throughout the minimum 30-year post-closure maintenance period and beyond. 3.2.1 FINAL COVER DESIGN 3.2.1.1 REGULATORY DESIGN STANDARDS California Final Cover Prescriptive Design Standard The minimum final cover standards for the Forward Landfill, as outlined in the closure and post-closure requirements for Class II landfills contained in 27 CCR, Section 21090 include: • Foundation Layer: A minimum two-foot thick layer of soil placed immediately over the entire surface of the last lift of refuse. This layer shall have the appropriate engineering properties, so as to provide a relatively Forward Landfill PFCPCMP 3-1 J:\Allied\Forward\2005.0051 Partial Closure\Partial Closure Plan\FL-sec3.doc:6/15/2005