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• Samples obtained from the test holes were examined and classified in [he laboratory by the project <br />engineer. Laboratory testing included standard property tests, such as natural moisture contents, dry <br />unit weights, grain size analyses and liquid and plastic limits. The laboratory testing was conducted in <br />general accordance with applicable ASTM and AASHTO specifications. <br />The subsurface conditions encountered in the test holes were variable and generally consisted of a layer <br />of gravel fill materials overlying natural sands and clays. <br />The existing gravel layer ranged from 9 to 16 inches in thickness. The near surface subgrade soils <br />encountered beneath the gravel layer generally consisted of sands and clays to the maximum depth <br />investigated. The sands and clays generally classified as CL to CL-SC soils in accordance with the <br />Unified Soil Classification System. The sands and clays will generally provide poor to fau subgrade <br />support for the proposed gravel sections. Free groundwater was not encountered in the test holes a[ <br />the time of drilling. <br />Pavement Recommendations: The subgrade soils encountered along [he proposed roadway were <br />somewhat variable and generally consisted of a layer of existing gravel fill materials overlying natural <br />sands and clays. The existing gavel till materials were in very poor to fau condition; therefore, a <br />strength coefficient of 0.03 was used in the design of the new gravel section. The underlying clays <br />classified as A-7-6 to A-6 soils in accordance with the American Association of State Highway <br />Transportation Officials (AASHTO) classification system. Using the group index values obtained on <br />• the subgrade soil samples, a correlated soils resilient modulus of 5000 psi was used in the design <br />process. <br />It is our understanding [ha[ the subject roadway will be used as an access road which will generally be <br />subjected [o light traffic volumes related to pickup [rucks and occasional delivery and construction <br />trucks; however, the northern 2,000 Feet of the roadway will be subjected to a moderate to high traffic <br />volume during the disassembly of the dragline. Therefore, we have assumed an 18 kip equivalent single <br />axle loading (ESAL) of 120,000 (or the northern portion of the roadway and an ESAL of 6,500 for the <br />southern portion of the roadway. <br />The gravel sections presented below are based on the field investigation, laboratory test results, the <br />assumed traffic loadings and the AASHTO Guide for Design of Pavement Structures (1986). The <br />design calculations are shown in Appendix A. <br />We recommend that [he gravel section to be constructed for the portion of the roadway located from <br />the dragline to the north end of the roadway consist of a minimum of 12 inches of pit run gravels and 6 <br />inches of road base gravels. The portion of the roadway located south of the dragline should be <br />resurfaced with a minimum of 6 inches of pi[ run gravels and 4 inches of road base gravels. The new <br />gravel sections should be placed over the existing gravels. <br />Subgrade/Gravel Preparation: Prior to placing the new gravel sections on the roadway, we <br />• recommend that all of the loose and soft materials be removed and [he existing gravels be reshaped <br />IRa~ <br />