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• The natural topsoil materials encountered in the majority of the test pits were typically 3 to 8 inches in <br />thickness. However, a thicker layer of topsoil materials, approximately 2 feet in thickness, was <br />encountered in the test pit (#3) excavated in the lower lyine/drainage areas. Natural clays were <br />encountered below the topsoil materials in all of the test pits. The clays extended to depths ranging hom <br />3'/: to 10 feet below the existing ground surface. The clays were nil to slightly sandy with sand and clay <br />lenses, moderately to highly plastic, very stiff to hard, slightly moist to moist and brown in color with <br />occasional mottled gray and iron staining. The clays classified as CL to CL-CH soils in accordance with <br />the Unified Soil Classification System and az A-7-6 soils in accordance with the AASHTO Classification <br />System. <br />Natural sands and gravels were encountered below the clays in test pit #4 at a depth of 5 feet. The sands <br />and gravels extended to the maximum depth investigated, 6 feet. The sands and gravels were silty to <br />clayey, fine to coarse gained, medium dense, wet and brown to gray in color. Caaystone bedrock was <br />encountered below the clays in test pit #6 at a depth of 3 '/, feet and these materials extended to the <br />maximum depth investigated, 5 '/: feet. The claystone bedrock materials were nil to slightly sandy, <br />moderately to highly plastic, hard, slightly moist and brown to gray in color. A sample of the claystone <br />bedrock materials classified as a CL-CH soil in accordance with the Unified Soil Classification System and <br />as an A-7-6 soil in accordance with the AASHTO Clazsification System. The laboratory test results are <br />summarized in Table 1. <br />Groundwa[er seepage was encountered in test pit 3 at a depth of 9 feet at the time of excavation and in test <br />• pit 4 at a depth of 5 feet. The depth at which the groundwater levels were encountered and the depths at <br />which the soil samples were taken are shown on the logs of the exploratory test pits. <br />Pavement Section Recommendations: It is our understanding that the new access road will generally be <br />subjected [o low traffic volumes typically consisting of pickup trucks with occasional delivery haul trucks. <br />Therefore, we have assumed an J 8-kip equivalent single axle loading (ESAL) of 3,000 for the access road. <br />Based on the laboratory test results and classification of the clays, we have correlated a soils resilient <br />modulus of 5000 psi for these materials. <br />Based on the subsurface conditions encountered across the site, the assumed traffic loadings and our <br />experience with similar projects, we recommend that the proposed access roadway be constructed with a <br />gravel section consisting of 8 inches of subbase (pit run) gravels and 3 inches of base course gravels. An <br />alternate section would consist of 6 inches of pit run gravels and 4 inches of base course gravels. These <br />gravel sections should be placed on the natural clays or properly compacted fill materials. We have <br />azsumed that the topsoil materials and organics will be removed prior to placing gravels or embankment fill <br />materials. If the client elects to leave the topsoil materials in place and place the pavemenUgravel section <br />over a geotextile/stabilization fabric, such as Mirafi 600X or an equivalent product, then the subbaze gravel <br />sections given above should be increased by 12 inches. Which results in total subbase gravel thickness <br />ranging from I8 to 20 inches. <br />Suberade/Gravel Section Recommendations: Prior to placing the gravel sections on the new roadway or <br />• prior to constructing any embankment fills, we recommend that all of the topsoil and organic materials be <br />removed. Based on the limited amount of topsoil encountered across the majority of the roadway <br />Job Number: 01944 NWCC, Inc. Page 2 <br />