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produced a peak runoff of 4.3 cfs. Subbasin P1-12 is routed off the property by overland flow in the <br />vicinity of historical overland flow discharges and contributes flow to DP9. <br />Subbasin P1-13 has an area of 2 acres and is completely captured within the gravel mine and thus <br />the peak flow was not calculated. Water collected in the mine will be pumped into the Cache la <br />Poudre River. The storm water capture reduces flow at DP9. <br />Subbasin P1-14 is predominately cropland with an area of 159 acres. The imperviousness of the <br />subbasin is 2 percent. A portion of the basin will be used for temporary stockpiles, but these will <br />have an insignificant affect on the imperviousness. The runoff coefficient was calculated to be <br />0.400 for the 100-year storm. A time of concentration of 162 minutes would result in a 100-year <br />rainfall intensity of 1.39 inches per hour. Applying the rational method produced a peak runoff of <br />87.9 cfs. Subbasin P1-14 collects in a slough and returns to the Cache la Poudre River via a deep <br />cut channel. <br />Reclaimed Conditions <br />This site will be mined and reclaimed to create a diverse, stable, and sustainable environment. <br />There are significant opportunities to enhance wildlife habitat and the natural aesthetics of the <br />Cache la Poudre River riparian corridor. The reclamation plan is designed to accommodate these <br />opportunities. Existing riparian vegetation and wetlands have been identified and will be monitored <br />and protected through mining and reclamation. Mining activities will be set back an appropriate <br />distance from all areas designated for preservation. <br />A combination of open water ponds, wetlands, and upland pastures will be created by the mining <br />and reclamation process. Creative use of materials generated by mining and processing operations <br />will enhance and compliment the existing riparian corridor. Silts will be used to form diverse silt <br />basin wetlands. Excess overburden will be used to vary the shape and slopes of the finished unlined <br />ponds. Native and adaptive plantings and ground covers will be used to restore and enhance all <br />areas disturbed by mining activities. <br />Subbasin RBI will be predominately grassland with an area of 134 acres. The imperviousness of <br />the subbasin is 2 percent. Based on the runoff equation in the USDCM, the runoff coefficient was <br />calculated to be 0.358 for the 100-year storm. A time of concentration of 153 minutes would result <br />in a 100-year rainfall intensity of 1.45 inches per hour. Applying the rational method produced a <br />peak runoff of 69.5 cfs. Runoff is routed through Subbasin RBI as overland flow. Subbasin RBI <br />returns to the Cache la Poudre River as overland flow at DPI. <br />Subbasin RB2 will be predominately grassland with an area of 45 acres. The imperviousness of the <br />subbasin is 2 percent. The runoff coefficient was calculated to be 0.401 for the 100-year storm. A <br />time of concentration of 95 minutes would result in a 100-year rainfall intensity of 2.04 inches per <br />hour. Applying the rational method produced a peak runoff of 36.9 cfs. Subbasin RB2 would be <br />captured by Pond 4C and would no longer contribute runoff to DPI. Elimination of Subbasin RB2 <br />runoff from contributing to DPI is the major cause of the reduction from the historical peak flow <br />rate of 203.0 cfs down to the reclaimed peak flow rate of 69.5 cfs. <br />-9- Revised Pmhminuy Dminage Report.doea