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-6- <br />from a 140 pound hammer falling 30 inches. This test is similar to the standard <br />penetration test described by ASTM Method D-1586. The penetration resistance values <br />are an indication of the relative density or consistency of the subsoils. Depths at which <br />the samples were taken and the penetration resistance values are shown on the Logs of <br />Exploratory Borings, Figs. 2 and 3. The~samples were returned to our laboratory for <br />review by the project engineer and testing. <br />SUBSURFACE CONDITIONS <br />Graphic logs of the subsurface conditions encountered at the site are shown on <br />Figs. 2 and 3. The subsoils consist of about 'k to 1 foot of topsoil and nil to 8 feet of <br />clay and silty sand overlying relatively dense terrace deposits of gravel, cobbles and <br />boulders in a silty sand matrix. Drilling in the terrace deposits with auger equipment <br />was difficult due to the cobbles and boulders and drilling refusal was encountered at <br />depths between 3'/z to 15'/z feet. The soils were slightly moist to moist and no free <br />water was encountered in the borings. <br />Laboratory testing performed on samples obtained from the borings included <br />natural moisture content and density, gradation analyses and liquid and plastic limits. <br />Results of gradation analyses performed on small diameter drive samples (minus 1'/z <br />inch fraction) of the coarse granular subsoils are shown on Fig. 5. The laboratory <br />testing is summarized in Table I. <br />PIT WALL STABILITY ANALYSIS <br />The stability of the pit wall slopes was evaluated based on the subsurface <br />conditions identified at the property, the proposed grading plan by High Country <br />Engineering and our experience with open pit reclamation. The cross section analyzed <br />for stability, shown on Fig. 6, is typical of the proposed southern pit wall and has a <br />maximum height of about 28 feet and maximum final slope grade of 2: l (horizontal to <br />vertical). The temporary pit wall slope was assumed to have a grade of 'fz: l and the <br />H-P GEOTECH <br />