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2 -42 <br />As shown on Figure 2.2 -3, sub - basins D -1 through D -16 are the major sources of <br />sediment for the sediment pond. The sub -basin area is about 70 acres. Pages 13 -17 in Appendix <br />M shows the required runoff volume of 1.7 Ac -ft, and the required sediment storage volume of <br />0.2 Ac -ft is calculated using the Universal Soil Loss Equation. Discharge from the sedimentation <br />pond is permitted through an NPDES permit issued by the Colorado Department of Health (See <br />Appendix E). <br />The facilities in the mine operations area were designed to convey the runoff from the <br />undisturbed area around the site in buried culverts. Design of all culverts is shown on Table 4.2- <br />13. The design points are shown on Figure 2.2 -3. As shown on Table 4.2 -10, there is a peak <br />flow of 32.4 cfs at the upstream end of the 42 inch diversion culvert for sub -basin C -3. Table <br />4.2 -13 shows the calculations which indicate that the capacity of the culvert is 117 cfs. The <br />diversion ditch and existing drainage downstream of the culvert have greater than 20 square feet <br />of waterway area to carry the flow at reasonable velocities. Culvert installation practices are <br />contained in Appendix M. <br />The 30 inch culvert on the north side of the mine site carries undisturbed flow from sub - <br />basins C -1 and C -2. Peak flow from C -2 is 14.03 cfs and C -1 is 3.67 cfs. The culverts have <br />adequate capacity of 63 cfs and 32 cfs respectively. This culvert discharges into the same <br />drainage as the 42 inch culvert draining C -3. The discharge area of these culverts are armored <br />with rip -rap to protect against erosion. The Operator has also obtained DRMS approval (MR- <br />15) to extend both of these culverts 50 feet to the bottom of the slope that they discharge onto to <br />further reduce the possibility of erosion. <br />The 42 inch culvert beneath the haul road is designed to safely pass the combined flow <br />from the upstream diversions. The design flow is 52 cfs and the capacity of the culvert is 149 <br />cfs. The other drainage facilities, as depicted on Figure 2.2 -3, are adequate to carry surface <br />runoff from the disturbed and undisturbed area, in accordance with applicable regulations. <br />Culverts Q, R, S and T were added at part of the TR -16 Gob pile and associated surface <br />facilities design. Culvert Q will go beneath Light Use Road #1 and has a design flow of 6.8 cfs. <br />Culvert R will go under the Haul Road to the Gob pile and has a design flow of 7.32 cfs. Culvert <br />S will go under Light Use Road #2 and has a design flow of 7.24 cfs. Culvert T will go under <br />Light Use Road #2 and has a design flow of 7.32 cfs. All three culverts will be 24" diameter and <br />provide a capacity of 12 cfs. <br />Rule 4.05.18, `Stream Buffer Zones', requires that surface coal mining operations will not <br />cause or contribute to the violation of applicable water quality standards, and that during and <br />after mining, the water quantity and quality, and other environmental resources of the stream <br />shall not be adversely affected. Therefore, a silt fence will be installed as shown on Figure 2.2 -3 <br />in order to control runoff from the disturbed area within 100' of East Salt Creek. The Stream <br />Buffer Zone will be clearly marked with signs in accordance with Rule 4.02.5. <br />MR -50 M`- Volume 1 (Rev 04/14) <br />