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• Geotechnical investigations for the CRDA-1, 2, and 3 are given in Appendices <br />13-4 and 13-5. At the CRDA-1, the Conclusion and Recommendations given by <br />Rocky Mountain Geotechnical in Appendix 13-4 are generally being followed. <br />The combination of 2h:1 v slopes with 10' to 15' wide benches on 30' intervals are <br />being installed above the first bench which is 50' high. The three subdrains were <br />installed during the initial construction. Three conventional piezometers have <br />been installed on the first bench (as opposed to the six pneumatic piezometers <br />suggested by Rocky Mountain Geotechnical). The top of the fill will be graded <br />2% to 5% to promote adequate drainage. Drainage from the top of the fill will not <br />be directed over the outslopes of the fill. The outslopes of the fill are considered <br />to be the completed face between two benches. When each new bench is <br />constructed, the rough construction face below that point will be completed by <br />grading it to its final configuration. Benches on CRDA-1 will be graded to the <br />inside at 2°1° - 5% and graded to drains to the sides at 2°1° - 5°!°. The CRDA-2 <br />was constructed in a similar fashion with the exceptions that underdrains were <br />not installed and the slope between benches does not exceed 2.5h:1 v.. <br />C <br />Powderhorn Coal Company will also comply with applicable parts of 4.10, 4.11, <br />4.09.1 and 4.09.2, except to the extent that the requirements of those <br />subsections are varied in 4.10.4. The specific measures to be employed include <br />the following: <br />- Piezometric monitoring of the coal processing waste embankment to <br />assess the accuracy of the assumptions used in the design analysis. <br />- Monitoring of side slopes to maintain a maximum slope angle of 2h:iv <br />between benches on CRDA-1 and 2.5h:1v between benches on CRDA-2 . <br />• <br />13-21 <br />(Rev. 5/03) <br />