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deep Sierran basement rocks are tilted gently to the west towards the axis of the <br />San Joaquin valley. Secondary structural features, such as fractures and joints, <br />were not detected in soil samples retrieved by coring. Minor textural features, <br />such as microfractures and fine rootholes. were observed in a limited number of <br />samples. <br />4.3.3 Site Soil Conditions <br />The site is situated in an area of gently rolling topography. Surficial soils con- <br />sisting of silts and clays extend from the ground surface to a depth of 2 to 3 feet, <br />commonly underlain by a 1/2 -foot layer of cemented soil referred to as hardpan. <br />Extensive soil deposits cover and inhibit surface observations or mapping of the <br />underlying alluvial deposits of the Turlock Lake and Riverbank Formations. <br />Laboratory tests were run on soil samples obtained during the field investigation. <br />Bulk samples were classified using Atterberg limits and percent passing the <br />No. 200 sieve. Compaction curves and remolded permeability tests were also <br />conducted on selected bulk samples to evaluate their suitability for use as soil <br />liner and cover material. Undisturbed samples were evaluated for strength prop- <br />erties using direct shear and unconfined compressive strength tests. <br />Laboratory classifications confirmed field descriptions. Testing focused on fine- <br />grained soils with potential use in landfill construction. Fine grained soils de- <br />scribed in the field as clays and silts were classified by testing to be primarily CL <br />and ML, respectively. Sand content of fine-grained soils within the 0 to 20 feet <br />interval ranged from less than 5 to 50 percent. <br />Silty sand samples tested were found to contain between 39 and 47 percent <br />fines. It should be remembered that soil materials from shallow depths at the site <br />vary gradationally, both vertically and horizontally, with respect to fine-grained <br />versus coarse-grained characteristics. Isolated samples do not necessarily indi- <br />cate consistent lithologies across the site. <br />Samples of soils to approximately 9-1/2 feet from Borings P-1 and P-2 were <br />tested for compaction characteristics and remolded permeability to ascertain the <br />• • 9390218A.00W 22 0 July 20, 98 <br />