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CMC CONTINENTAL MATERIALS CORPORATION <br /> Nearly the entire area west of the mine boundary was burned in the Waldo Canyon Fire in 2012. <br /> This area is naturally restoring itself and contains a mixture of grasses and shrubs. A curve <br /> number of 63 was selected for this area, and this value is for semiarid rangelands with oak, <br /> aspen, mountain mahogany, and other shrubs with fair conditions and D group soils. <br /> A curve number of 70, described as "pinyon-juniper, pinyon, juniper, or both; grass understory", <br /> was used for native areas north and south of the quarry, based on Figure S-3 in Peak Flows in <br /> Colorado (SCS 1977). These areas have a B group soil, and a cover density of 25% was used. <br /> For the portions of the stockpiles and slopes that have been reclaimed as grassland, a CN of <br /> 74 was selected based on a grassland with light or occasional grazing with C-type soils. Curve <br /> numbers are summarized in Table G-2. A weighted curve number was calculated for <br /> subwatersheds that were comprised of a mix of these cover conditions. <br /> Table G-2 <br /> Curve Number Summary <br /> Cover Curve Curve Number Reasoning <br /> Number <br /> Reclaimed stockpile and slopes 74 Grassland with light or occasional <br /> grazing with C type soil <br /> Forested area 63 Oak-aspen-mtn brush with D type <br /> soil and fair conditions <br /> Pinyon-Juniper 70 Juniper-grass with B type soil and <br /> 25/o cover <br /> c. Sediment Control Structures <br /> This section describes the sediment control structures necessary to meet the water <br /> management design criteria during reclamation and includes two types of channels: terrace <br /> ditches and down drain ditches. The ditches have been designed to collect runoff from <br /> reclaimed areas and convey it to existing drainages. Runoff from native areas between the <br /> drainages and the reclaimed areas will collect in the down drain ditches and is included in the <br /> runoff calculations. Runon from drainages west of the quarry is also considered in the <br /> calculations. The designs for each of the ditches are based on calculated peak flow rates. Figure <br /> G-1 shows the drainage plan for the final re-sloped surface and includes the network of ditches. <br /> Terrace ditches will intercept runoff from reclaimed areas, minimizing local erosion and assisting <br /> the shedding of water off the surface. The terrace ditches have been spaced to limit slope <br /> lengths to approximately 225 feet (100 feet in elevation). This slope length is typical for the <br /> Pikeview Quarry Amendment 4 <br /> G-5 <br />