2012-04-10_REVISION - M1981185 (43)

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Between Stations 16 +50 and 21 +00, the upper 30 inches of road should be overexcavated and replaced in layers less than 8 inches thick, moisture condition to within 3 percent of optimum, and be compacted to at least 95 percent relative compaction per ASTM D1557-09. Between Stations 21 +00 and 27 +50, the roadway subgrade should be prepared by scarifying the upper 6 inches, moisture conditioning the scarified soils to within 3 percent of the optimum moisture content, and compacting to at least 95 percent relative compaction per ASTM D1557-09. The completed roadway should covered with a layer of 2 -inch minus crushed rock approximately 6 inches thick. The crushed rock paving layer should be compacted with vibratory roller. Four passes with the roller will be sufficient to achieve the desired compaction of the crushed rock layer. 5.3 Retaining Walls Where the minimum allowable roadway width cannot be achieved at the existing fill slope inclinations, a mechanically stabilized earth (MSE) wall is recommended to construct the fill slopes. Because MSE walls utilize horizontal reinforcing mats in the fill behind the wall face, slopes can be increased to 3/4:1 or steeper. The wall should bear on bedrock and be designed in accordance with the manufacturer's recommendations. The manufacturer may require the use of granular fill which, if not available onsite, may need to be imported or processed on site. 5.4 Monitoring A monitoring program to measure the magnitude and rate of movement of key access road locations and retaining wall components, if necessary, should be designed and implemented by the Geotechnical Engineer. At a minimum, monument control points should be established at 20 +20, 20 +40, 20 +60 and 20 +80. The monitoring points should be monitored by a surveyor licensed in the State of Colorado to within a tolerance of 0.01 feet. Following baseline readings, the first round of survey measurements should be obtained one week later and quarterly thereafter while road is in use. Where movement exceeds 0.1 feet between monthly readings, monitoring frequency should be reduced to weekly. If movement exceeds 0.1 feet between weekly readings, use of the access road shall cease until an inspection by the Geotechnical Engineer is performed to assess the nature of the movement judges the road sufficiently stable or until recommended repairs implemented under his/her oversight. Rule 6.5 Geotechnical Stability Technical Revision New Access Road April 2, 2012 Page 6