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-~- <br />gations for ponds, building, and other surface structures. <br />None of these previous borings is located directly beneath <br />the initial waste rock storage area. However, several borings <br />are located reasonably close to the storage area. The uni- <br />fomity of materials encountered in these borings and the <br />morphologic character of the bench provide reasonable justi- <br />fication for assuming that similar materials will comprise the <br />foundation beneath the waste rock pile. This assumption will <br />be verified later when the ground water monitoring system is <br />installed. <br />Logs of borings from within this general area indicated <br />that subsurface materials consist principally of low plas- <br />ticity clays (CL in the Unified Soil Classification system, <br />Plate 3) and sandy clays (CL-SC). Small rock fragments are <br />present throughout. The material generally grades from stiff <br />just below the topsoil cover to hard at depth. Water content <br />varies from moist to slightly moist, typically being within <br />the range of 10 7 to 20 7. A topsoil layer of soft silt and <br />clay is generally one to two feet thick. Logs of relevant <br />borings are presented in Appendix B. <br />Testing which has been perfomed on typical subsurface <br />clays from within the bench area includes triaxial tests, <br />direct shear tests, swell-consolidation tests, gradation <br />analyses, compaction tests, and index tests. <br />Based on all available test results, Chen and Associates <br />(1980) have recommended the following effective stress para- <br />meters for the natural soils in the vicinity of the initial <br />waste rock storage area: <br />Soil Type ~' c' (ksf) <br />Slightly sandy clay 34° 0.25 <br />rcoHrooo corawimw, iwc. <br />