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TECHNICAL MEMORANDUM Page 3 June 3, 1992 SAC31583.AC.ZZ a composite lining system consisting of flexible membrane lining (FML) underlain by a minimum 2 -foot -thick compacted clay liner. In areas outside of the base excavation, refuse will be placed over existing waste material including an ash disposal pit (WMU E), an interim leachate impoundment facility (which will be closed prior to having refuse placed above it), and various other Class 2 and Class 3 WMUs containing various types of waste. The eastern ash disposal pit (WMU E) is lined with a 2- to 4 -foot compacted clay liner at approximately elevation 15 feet. The location of WMU E is shown in Figure 1. The final cover for the proposed landfill extension will be benched to control surface drainage and reduce erosion. The vertical distance between benches will be 50 feet. The maximum slope between benches will be 3 to 1; the effective overall slope of the cap will be 3.3:1. The project also includes two sedimentation basins and leachate impoundments. As shown in Figure 1, these sedimentation basins and leachate impoundments are are located near the creek. Previous Explorations A subsurface exploration was performed by EMCON Associates in 1972 to evaluate the soil conditions at the Forward Landfill site. A total of 17 borings, ranging from 38 feet to 178 feet in depth, were performed by EMCON. The approximate location of these 17 borings are shown in Figure 1. A Cone Penetrometer (CPT) exploration was performed by Insitu- Tech in 1987 in the WMU E area. The exact CPT locations are not known. Limitations This report has been prepared for the exclusive use of CH2M HILL and Forward, Inc. for specific application to the project described in this technical memorandum. Conclusions, recommendations, and results of engineering analyses presented in this technical memorandum are based on information obtained from the field exploration and from existing data. These results reflect subsurface conditions only at specific locations, times, and to the depths explored. Variations in subsurface conditions may not be revealed by these borings. This technical memorandum was prepared in accordance with generally accepted local geotechnical engineering practice. No other warranties either expressed or implied are •