Laserfiche WebLink
INTEROFFICE MEMORANDUM <br />TO: 'I'RAPPGR MR-1881~iL' <br />FROM: Jr\NE'1' B]NNS <br />SUBJECT: RIiTGN'1'IO OF (. 'POUR DI'1'CFIh'S "CO SUPPORT LIVL?STOCK Wr\'I'ER "TANKS <br />DATE: 03/28/03 <br />I have reviewed MR-188 for retention of contour ditches to support permanent stock ponds. <br />TMI has requested contour furrows that feed into Livestock ponds: CM07, JE03, JM02, JM12, JW07, <br />JW25, NNM03, NNMOS, NNM07, NNWO1, and NNW04. These livestock ponds have already received <br />approval to remain as permanent in SLr01. The contour ditches help direct runoff into the livestock <br />ponds. Post-mining land use is rangeland with wildlife use. Water vailablity is limited in these upper <br />slopes so directing additional water into the livestock ponds would support the post-mining land-use. <br />Rule 4.05.3(3) requires that permanent ditches be capable of carrying the 10-year 24-hour precipitation <br />event. TMI provided SEDCAD4 model runs using 10-year, 24-hour storm events. Ditches were designed <br />to pass a 25-year, 24-hour event with a curve number of 70. TMI's modeling shows that the ditches are <br />adequate to pass the 10 year-24 hour event with a 67.0 curve number. The actual curve number is likely <br />lower than this due to 10-15 years of vegetative growth and litter in these areas. The Division considers <br />that these ditches will withstand a 10-year, 24-hour storm event. <br />TMI has submitted revised page 3- I51 to allow for retention of contour furrows. <br />The Division agrees that the contour ditches to the specified livestock ponds may remain. <br />