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s <br />• We strongly recommend that the finished subbase grade surface be proofrolled with a heavy piece of <br />construction equipment after it has been adequately moisture treated and compacted, and prior to placing <br />the base course 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 base course gravels. An <br />engineer from this office should observe the proof roll as it is completed. <br />We recommend that the subbase sands and gravels meet the requirements for Class I base course <br />aggregates in accordance with the Colorado Department of Transportation (CDOT) Specifications, 1999. <br />However, the upper end of the gradation requirement should be modified to allow 6-inch minus materials. <br />The base course gravels should meet the requirements for Class V or VI base course aggegates in <br />accordance with the CDOT specifications. We recommend that the subbase gravels and base course <br />gravels be tested for compaction and that the thickness of the completed lifts be measured to verify that the <br />required gravel sections have been constructed. <br />Surface Drainase 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 the 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 azea 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 azea for use by the client for design purposes. The conclusions and <br />recommendations submitted in this report are partially based upon the assumed subsurface conditions and <br />traffic loadings. If during construction, the subsurface conditions appear to be different from those <br />assumed and described herein, this office should be advised at once so that reevaluation of the <br />recommendations may be made. We recommend the on-site observation of the subgrade proof rolling, <br />gravel placement and fill~ttpaction by an engineer from this office. <br />If you have any quest s concerning this report or our recommendations, or if we may be of any further <br />service, please cont this office. <br />ANTS, INC., <br />U <br />• <br />A <br />Job Number: 01-5023 NWCC, Inc. Page 2 <br />