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File No. 20-1008-36 July 14, 1995 2.3 BORROW OPERATION Borrow materials will be transported by truck from Granite's Tracy plant stockpile. During excavation of materials, soils with SC, CL, CH, ML, and SM classifications will be stockpiled for mixing and use in the barrier layer. No clean, sandy materials (SP)will be used in cover materials. 2.4 BARRIER LAYER SOIL DESIGN MIX A total of five bulk samples were obtained from the designated stockpile areas at Granite Construction. The soil samples collected at the stockpile consisted of clayey sand (SC) and sandy clay (CL). While previous studies indicated that some of the untreated stockpile materials would meet the minimum permeability requirements, it is evident that the majority of the materials currently at the stockpile do not meet permeability requirements or a desired"cushion" amount. Based on our experience over the past eight years, a large supplier of imported clay has been North American Refractories located in Ione, California. Because of its remote location from the landfill, a closer source of imported clay is desirable to reduce haul costs. Granite Construction currently has a supply of red clay at their Tracy plant, located approximately 4-1/2 miles north of the landfill. According to Granite, this clay exists as overburden and seams in their aggregate mining operations. An engineer from Meinfelder observed a portion of the inplace red clay and acquired a bulk sample of this clay. The clay deposit appeared fairly uniform; however, some small amounts of gravel were encountered at the base of these clay deposits. Permeability, gradation, Atterberg Limits, and compaction curves were performed on samples composed of various percentages of this clay mixed with the bulk samples from the stockpile area. A summary of these laboratory tests is presented on Table 2-2; Laboratory compaction curves are presented in Appendix D. The percentages of red clay varied between 20 and 30 percent. During the preparation of test samples, it was originally intended that the minimum degree of compaction would vary from approximately 90 to 95 percent for red clay percentages at 30 and 20, respectively. The recommended minimum degree of compaction is 90 percent of the maximum dry density as determined by the ASTM D1557 test procedure for a minimum of 30 percent of red GSM.-md CH195 Page 8 of 31 July 14, 1995 20-1008-36(CQACOR) Copyright 1995,Kleinfelder,Inc.