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Daniel Hernandez <br />Apri121, 2006 <br />Page 5 <br />- Alignment of the spillway channel should be preserved and/or redesigned. <br />- Installation of an upstream guard gate and extension of the outlet pipe as discussed <br />above. <br />- Site specific field investigation of soils and determination of strength pazameters as <br />discussed above. <br />- Recalculation of factors of safety and yield accelerations with representative soil <br />strength parameters. <br />- Further investigation into deep drainage features such as horizontal or directionally <br />drilled drains for the landslide. <br />- Appropriate filter criteria must be met for the chimney and blanket drain material. <br />We appreciate the opportunityto review and provide comment to the Colorado Division ofMinerals <br />& Geplogy and hope the information provided is helpful in your review of the submitted coal mine <br />permit revision. <br />Sincerely, <br />Jason P. Ward, Ph.D., P.E. <br />Dam Safety Engineer <br />cc: Frank Kugel, Division Engineer <br />Wayne Schieldt, Assistant Division Engineer <br />Steve Tuck, Water Commissioner <br />Mark Haynes, Chief of the Safety of Dams Program <br />Willy Kistler, President, Minnesota Ditch & Reservoir Company <br />