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5 rATL OI° COl ONAI)O II^ ~I nll 11 U. L~MM r{nvnrr.,e <br />DEPARTMENT OF NATURAL RESOURCES <br />D. Monte Pascoe, Executive Director <br />1V11NED LAND RE(1LAMA'TION <br />423 Centennial Bui{ding, 13135herman Street <br />Denver, Colorado 80203 Tel. (303) 839-3567 <br />III IIIIIIIIIIIII III <br />999 <br />David C. Shelton <br />Director <br />TO: Brian Munson ~ / <br />FROM: Jim Pendleton <br />RE: Review of A pendi N, O, P and Q of the Hayden Gulch Coal Mine <br />Permanent Permit Application, Dealing with Various Geotechnical Topics <br />Pursuant to your request I have reviewed appendices N, O, P and Q of the Hayden <br />Gulch Coal Mine application. I forward the following comments for your <br />consideration. <br />Appendices N, O and P <br />Appendices N, O and P, prepared by Chen & Associates, each deal with <br />foundational investigation and engineering design of various ancillary facilities <br />for the Hayden Gulch Coal Mine. (underground fuel storage tanks, building <br />foundations, railroad spur, loadout building foundations, haul road pavement <br />section design, etc.) <br />In each case Chen & Associates appears to have conformed with prudent state-of- <br />the-art of geotechnical and engineering practices. Assuming the construction <br />of the facilities conforms with the consultant's recommendations, I would not <br />anticipate any performance problems with these facilities. <br />Appendix Q <br />Appendix Q presents the results of the geotechnical investigations, design <br />parameters, stability analyses, construction guidelines and monitoring <br />recommendations for each of the proposed five sediment control reservoirs. In <br />the words of the consultants: "The proposed earth Fitt embankments will range <br />in configuration from a crest height of 22 to 54 feet and side slope of 2.5 to <br />3 horizontal to 1 vertical and have maximum impoundment of approximately 5 to <br />39 acre-feet." As such all of the proposed embankments classify as "sedimentation <br />control reservoirs", in accordance with Rule 4.05.6(10). <br />The consultant's report contains thorough geotechnical investigations, including <br />materials testing results of the sub-soils and bedrock, of each of the various <br />reservoir sites. The report observes that care in design and construction is <br />necessary on this site because of the moderately steep foundational slopes and <br />the high degree of saturation of many of the foundational sub-soils. Particular <br />concern is focused upon pond kI and its embankment. <br />(cont'd) <br />March 18, 1981 <br />