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iii iiiiininiu iii ~ - c <br />~ ~~i ~, OF COLORADO <br />DIVISION OF MINERALS ANp GEOLOGY <br />Department of Natural Resources <br />1313 Sherman $i., Room 215 <br />Denver, Colorado 80203 <br />Phone: 13031 8663567 <br />FA%:13031872-8106 <br />DATE: October 20, 1994 <br />TO: Harry Ranney <br />FROM: Joe Dudash ~~ <br />RE: West Pond and East Pond Hydrology and Sedimentology, National King <br />Coal, Permit No. C-81-035 <br />II~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCE <br />Roy Romer <br />Governor <br />lames 5. Lochhead <br />Executive Dvecror <br />Michael B Long <br />Division D~rec~or <br />You had requested that I review the pond designs for King Coal's west pond and east pond. <br />This memo outlines the results of my analyses. <br />Concerning the west pond, the bottom line is that the pond discharge from a 10 year - 24 <br />hour event would have settleable solids of 2.03 mUl, in excess of the .5 mUl standard. The <br />operator did not provide a sedimentology analysis for pond discharge. Also, various places <br />on the embankment top need to be raised in order to ensure that there is at least one foot of <br />freeboard between the maximum elevation of pond water due to the 25 year - 24 hour event <br />and the top of the pond embankment. The 25 year - 24 hour event maximum elevation is <br />calculated at 7390.3 feet whereas the lowest pond embankment top elevation is 7391.05 feet, <br />as measured by a transit and rod. <br />The maximum elevation of the pond water fora ]0-year - 24 hour event is right at the <br />emergency spillway elevation. However, I had to use the minimum pipe diameter allowed in <br />Sedcad of 3 inches, whereas the real diameter is 2.38 inches. Had the real pipe diameter <br />been used, the 10 year - 24 hour event would have spilled over the emergency spillway, in <br />violation of the regulations. <br />Concerning the east pond, there is ample storage capacity to hold the nlnoff from one <br />10 year - 24 hour event, one 25 year - 24 hour event and the corresponding sediment <br />volume, all at the same time. <br />For my analysis of the west pond design I had to make certain assumptions. As you know, <br />map C-4, Mine Surface Drainage, and map C-13, As-Built Plans, show different elevations <br />for the same feature. I attempted to tie map C-13 features to map C-4 elevations, since the <br />elevations on map C-13 were only relative elevations. I also changed the elevation of the <br />