Laserfiche WebLink
~' <br />December 19, 1980 <br />TD: Mike Savage - ~~~ <br />~~~~/ <br />FROM: Bob Liddle ~'~r,~~~,~//1 ~~~ <br />RE: Review of TBM Sediment Control <br />•'A <br />David C. Shelton <br />Director <br />The following comments are directed at the TBM response to Carol Pahlke's <br />adequacy comments of September 8, 1980. My concerns must be addressed <br />before we can yive approval of TBM's plan. <br />b6. To verify that the berm in the Pit p1 area will be high enough to <br />prevent disturbed drainage from entering diversion 22-D3, TBM will have to <br />show designs and cross-sections of this berm. In addition, TBM must <br />indicate what will prevent undisturbed drainage above ditches 22-D1 and <br />22-D2 from flowing off the hi 21, through the buffer area and directly into <br />pond 22-P1, A small diversion will be needed above pond 22-P1 or else <br />the ponds must be sized to include all undisturbed drainage. <br />b8. TBM's use of a C factor of 0.45 is unjustified. There are recent <br />studies indicating that regraded spoils decrease infiltration rates. (See <br />Westmoreland study by John Herrin, Pittsburgh and Midway Coal Company Study, <br />and Soil, Water, + Solute Movement in Montana Strip Mine Spoils by the University <br />of Montana.) In addition, the C factor from your referenced table 10 <br />assumes idle land that has not been disturbed and the cover at the surface <br />is grass, grasslike plants, decaying compacted duff, or litter at least <br />2 inches deep, Even the application of mulch would have little effect on <br />the C factor since the length limit of mulch for C valves is 50 feet on <br />30~ slopes. (See Table 9 of Agricultural Handbook No. 537). <br />Fiore representative C valves have been reported for mining conditions. <br />Utah State University recommends C valves from 1.30 to 0.90 depending on <br />conditions and time after disturbance. (See "Manual of Erosion Control <br />Principles and Practices", Hydraulics and Hydrology Series report No. 7f-78-002, <br />Utah Water Research Laboratory, 2978). Barfield and lfaan ("Hydrology and <br />Sedimentoloyy of Surface Mined Lands", University of Kentucky, 1979) recommend <br />'.IA 11 ill l(II OIf ArIU ni~nnlJ~U •~v•~••~~ ^11 ^p ~l~~l~~~~~~lr ' <br />999 <br />DEPARTMENT OF NATURAL RESOURCES <br />U. Monte Pasc oe_ Eyecuove Uaec mr <br />n~i~~':u i,~r~u tit i':c~,~rn~n•r~o;v <br />423 Centennial 8uild~n g, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 839-3567 <br />(cont'd) <br />