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• West Refuse Pile Haul Road: Based on the four test holes advanced along this road, it appears that [he <br />pit run sands and gravels aze highly vaziable in depth and condition. The pit run gravels placed in the <br />eastern end of the roadway and above the hill ranged from 12 to 24 inches in thickness, however, the <br />upper 6 to 8 inches of material were very loose and should be recompacted. A 6-inch layer of pit run <br />sands and gravels was encountered at the roadway surface at the bottom of the hill, however, it was <br />underlain by approximately 22 inches of coal fill material. We did not encounter any pit run sands and <br />gravels in the westem end of the roadway. <br />Based on the conditions enwuntered along this roadway, we recommend that the western half of the <br />roadway, from the top of the hill to the west end, be constructed with a gravel section consisting of 4 <br />inches of base course gravels and 17 inches of pit rnn sands and gravels. Prior to placing the pit run <br />sands and gravels, the exposed subgrade soils should be scarified to a minimum depth of 12 inches, <br />brought to within 2 percent of the optimum moismre content determined in accordance with ASTM D698 <br />and then be recompacted to at least 95% of the maximum standard Proctor density. For the pottion of <br />[he roadway situated a[ [he east end of the alignment and above the top of the hill, we recommend that <br />the exposed pit run sands and gravels be scarified to a minimum depth of 6 inches and then be <br />recompacted to at least 95% of the maximum modified Proctor deosiry. After this area has been <br />recompacted and tested, an additional 5 inches of pit run sands and gravels should be placed over these <br />materials. Four inches of Class VI base course gravels should be placed over the pit run sands and <br />gravels after they have been adequately compacted. <br />• Horizontal and vertical profiles were not provided for this roadway. Therefore, we did not address these <br />issues in this report. <br />Subbase/Base Coarse Preparation: We recommend tltat the existing roadways, Haul Road B Extension <br />and Fish Creek Borehole Access Road, be proofrolled with a heavily loaded truck prior to any gravel <br />placement. Areas which deform excessively under the wheel loads should be removed and stabilized. <br />Areas appearing to be stable should be scarified to a depth of 4 inches, moistened to the optimum <br />moisture content and then recompacted to at least 95S'o of the maximum modified Proctor density, i^ <br />accordance with ASTM D1557. Any additional base course or pit run gravels placed on the roadway or <br />any portions of the roadway where additional gravels are required, should also be compacted to at least <br />95% of the maximum modified Proctor density at or neaz the optimum moisture content. The base <br />course and subbase gravels should be approved by the soils engineer, prior to placement. We <br />recommend that the road base gravels placed on the roadways meet the requirements for Class V or Vl <br />base course in accordance with the Colorado Department of Transportation specifications. In addition, <br />the subbase gravels should meet the requirements for Class 1 or Class iI base course. <br />Drainaee: As previously stated, the collection and diversion of surface drainage away from the roadway <br />aeeas is extremely important for satisfactory performance of the roadway. The design of surface drainage <br />features should be carefully considered to remove all water from all roadway areas. In addition, the <br />maintenance of all drainage structures should be conducted periodically to ensure proper performance. <br />We recommend that the new gravel surface be constructed with a crown or super elevation of at least 2 <br />• percent. We a]so recommend that the existing gravels be reshaped so that a crown is established <br />throughout the pavement section. <br />lob No. 994061 Northwest Colorado Consulunts, Inc. Page 5 <br />