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• alignment, it appears that the removal of the topsoil will be more economically feasible than leaving the <br />topsoil materials in place and using ageotextile/stabilization fabric. However, in [he lower/wetland areas <br />or crossings it may be feasible [o use the geotextile/stabilization fabric and increased subbaze gravel <br />section. <br />Aker the topsoil materials are removed, we recommend that the exposed clays be scarified to a minimum <br />depth of 6 inches and then he brought to within 2 percent of the optimum moisture content and then be <br />recompacted to at least 95% of the maximum standard Proctor density determined in accordance with <br />ASTM D698. Any additional fill materials placed at the site should also be compacted [o at least 95% of <br />the maximum standard Proctor density and within 2 percent of the optimum moisture content. <br />We strongly recommend that the finished subgrade surface be proofroiled with a heavy piece of <br />construction equipment after they have been adequately moisture treated and compacted, and prior to <br />placing the subbase gravels. Areas, which deform or pump under the wheel loads of the construction <br />equipment should be removed and/or stabilized prior to the placement of the subbase gravels. An engineer <br />from this office should observe the proof roll as it is completed. <br />The subbase and base course gravels should be compacted to at least 95% of the maximum modified <br />Proctor density determined in accordance with ASTM D1557. We recommend that the subbase gravels <br />mee[ the requirements for Class I base course aggregates in accordance with the Colorado Department of <br />Transportation (CDOT) Specifications, 1999. The base course gravels should meet the requirements for <br />• Class V or VI base course aggregates in accordance with the CDOT specifications. We recommend that <br />the subbase gravels and base course gravels be tested for compaction and that the thickness of [he <br />completed lifts be measured to verify that the required gravel sections have been constructed. <br />Surface Drainaee Recommendations: For the adequate performance of any roadway, positive surface <br />drainage must be provided and maintained. This includes periodic cleaning and regading of the drainage <br />ditches along the edges of the roadway. In addition, the roadway surface should be graded on a periodic <br />basis to ensure that sufficient crown or super elevations is maintained so that the roadway surface <br />adequately drains to the ditches. We recommend that subject roadway be constructed with a minimum <br />crown or super elevation of 2 percent. <br />As noted above, the collection and diversion of surface drainage away from the roadway area is extremely <br />important for satisfactory performance of the roadway. The design of surface drainage features should be <br />carefully considered to remove all water from the roadway surface and embankment areas. In addition, the <br />maintenance of all drainage structures and roadway surface should be conducted periodically to ensure <br />proper performance. <br />Limitations: This report has been prepared in accordance with generally accepted soils and pavement <br />engineering practices in this area for use by the client for design purposes. The conclusions and <br />recommendations submitted in this report are based upon the assumed traffic loadings and the data obtained <br />from the test pits excavated along the proposed roadway alignment. If during construction, the subsurface <br />• conditions appear to be different from those described herein, this office should be advised at once so that <br />Job Number: OI-094-1 N WCC, Inc. Page 3 <br />