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geometry of the proposed expanded landfill, the differential settlement of existing wastes is expected to be negligible. The settlement analyses of new wastes indicate that significant settlement can occur. However, assuming a uniform settlement potential for refuse of 25%, the minimum landfill final cover slope gradient is calculated to drop from 5% to 3.75%. If randomly differential settlement of 22% to 28% occurs, the calculations indicate that the final cover gradient could range from 1% to 6% in areas where a 5% cover gradient is constructed. The settlement calculations also indicate a potential to promote ponding or to damage geomembrane cover layers if voids develop in refuse within 10 or 3 feet of the cover, respectively. In order to avoid this condition, additional load checks and waste disposal inspections will be performed to exclude large, potentially void-susceptible materials from the waste fill. 3.4.2 SURVEY/SETTLEMENT MONUMENTATION In order to monitor the future settlement of the Stage IA partial closure area, a settlement and survey monuments will be installed on the landfill in accordance with 27 CCR, Section 20950 (d). These monuments are proposed to consist of galvanized pipe, two inches in diameter and six inches in length placed in blocks of concrete, 24-inches in diameter by eight inches in depth. A nail and tag will be placed in the center of each monument for identification (see Detail 3 on Drawing Sheet D-3). One settlement monument is proposed to be placed on the bench of the Stage IA partial closure area as shown on Drawing Sheet 2. Survey monuments will be placed on undisturbed ground as reference points not subject to settlement as shown on Drawing Sheet 2. These points are the horizontal and vertical control points for the site aerial topographic survey and will be maintained or replaced, as needed, throughout the post-closure maintenance period. An aerial photographic survey of the site with a maximum contour interval of two feet will be performed and provided to the RWQCB, LEA and the CIWMB upon completion of closure activities. The settlement monument will be surveyed upon completion of all closure construction activities. Additionally, in accordance with 27 CCR requirements, Forward Landfill Inc. will update the aerial survey of the Stage IA partial closure area every five years throughout the post-closure Forward Landfill PFCPCMP 3-8 Z:\PROJECTS\Allied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-ser3.doc:6/16/2008