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RECLAMATION DRAINAGE ANALYSIS <br />The overall stormwater runoff for the reclaimed site was evaluated using three drainage basins. <br />Reclaimed runoff rates for the 2 -year, 5 -year, 10 -year and 100 -year storm events were calculated <br />using the Rational Method. Calculated flows were used in the onsite drainage facility evaluation. <br />Please refer to the Reclamation Drainage Plan located in the back pocket of this report for basin <br />delineation. <br />Design Storms: <br />Runoff Quantities: <br />Runoff Coefficients: <br />Soil Conditions: <br />Overland Flow Length: <br />Time of Concentration: <br />Rainfall Intensities: <br />FINAL DRAINAGE REPORT <br />IVERSON MINE <br />WELD COUNTY, COLORADO <br />Minor Storm: <br />Major Storm: <br />5 - year events <br />100 - year event <br />Developed basins were less than 160 acres; therefore, design storm <br />runoff rates were calculated using the Rational Method. <br />Percent imperviousness was determined for the anticipated land use <br />from Table RO -3 of the Urban Drainage and Flood Control District <br />Drainage Criteria Manual. The runoff coefficients were then taken <br />from the Urban Storm Drainage Criteria Manual. <br />Gravelly substratum, Ascalon loam, Dacono clay loam, Nunn loam, <br />and Otero sandy loam are the soil types on the site. The site soils <br />belong to Hydraulic Soil Groups B, C and D. <br />Flow length, L, was considered to be the furthest distance from the <br />know discharge point to the upstream end of the basin. <br />The time of concentration for the historic basin was calculated using <br />equation RO -2. A maximum distance of 500 feet was used for the <br />initial or overland flow time. Calculations and Urban Storm <br />Drainage References are included in this section of the report. <br />Rainfall intensity values were calculated using equation <br />28.5 *P1 <br />I— (10 78 <br />+ Tc� °6 <br />Manual. <br />taken from the Urban Storm Drainage Criteria <br />Calculations of the reclaimed runoff rates are included in this section of Appendix F. <br />