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III IIIIVIIIIIII III Doc Date:12/11/2001 <br />sss <br />5 ~ t Introduction <br /> <br />Enclosed in this appendix are the detailed design calculations for <br />tl~e sediment control system for Trinidad Basin Mining, Inc. <br />~ references used for the calculations are as follows: <br />1) Peak flows in Colorado, S6, M3rch, 1980. <br />2) Predicting Rainfall Erosion losses; Departrrent <br />of Agriculture, December, 1978. <br />3) Qiidelines fran MLRD of August 20, 1980 and August 21, <br />1980 which are enclosed. <br />Sediment ponds were sized for peak flows and a two year sediment <br />storage. Sediment storage was determined by using 0.1 acre-feet/disturbed <br />acre or by the U. S.L. E. equation. Peak flow was de+P*,++;n~ by using a <br />Type IIA storm in Eastern Colorado, according to acreage and curve <br />• number and appropriately corrected for slope ('t`able E1, Reference 1) <br />and for Watershed Shape Factor (Figure E-1, Reference 1). Ponds were <br />sized to meet the 10-year 24-hour event shown in Reference 1. <br />IInergency spillways were sized for the 25-year 24-hour event. <br />Drawings for each pond have been included as referenced in the text. There <br />are four areas shown on Map V-6 which are not wnducive to control <br />of sediment by ca3i.nant ponds. TSM will use erosion matting, specifi- <br />cation attached herein, to provide the best available technology to <br />control sediment from these areas. <br />Diversion ditches are designed to handle the 10-year 24-hour <br />event as are the culverts. <br />There appears t;o be a significant discrepancy between the actual <br />runoff events gaged on tl~e Apishapa River Hasin, adjacent to the Del Agua <br />• <br />