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<br />Design Volume Calculations -Lower Sump <br />Area Drainage Area (acres) 1.13 <br />Design Event 100 yr. Storm <br />Design Precipitation 3.2 <br />Average CN 89 <br />Calculated S 1.23595505618 <br />Description Exposed gravel and rocky soil <br />Calculated Runoff Volume (Q) 2.08 <br />Calculated Runoff Volume (acre-ft.) 0.20 <br />Ponding Percentage 5.00 <br />Actual Runoff Volume (acre/ft.) 0.19 <br />As shown on the Hydrology Map, this sump will have the design capacity of .22 acre feet allowing <br />for extra volume for sediment storage. Collection ditches will be installed that direct water from the <br />• disturbed areas into the sump. These ditches will be v-ditches of at least 1.0 feet deep and 2.OH:1.OV <br />sideslopes. No lining will be employed since the grades are mild and they aze leading to sediment <br />sumps. <br />Alternative Sediment Control (SAE) Topsoil Stockpile # 2 <br />Once topsoil is removed from this stockpile and while the azea is final-graded, a berm of 24" height <br />will be placed azound the former pile azea (2.69 acres) to prevent erosion from the azea. This berm <br />will be placed with a small dozer and will have 2H:1 V sideslopes. Once final bond release is granted, <br />this berm will be regraded into the surrounding terrain. <br />Stream Channel Reconstruction (Carbon Junction Canyon) <br />Carbon Junction Canyon will be reconstructed and permanently diverted as detailed below. The work <br />involves a diversion of 1962 feet that will be riprap lined and will have one culvert crossing under the maul <br />access road. The channel itself will be 14' wide after lining and varies in depth from 1.9 feet to 2.8 feet for <br />segment 6, including freeboard. <br />Technical Revision to Appendices 5-9 and 5-10 of this coal permit shows that the peak flow for the <br />upper segment (above the junction with the mine access road) is 346 cfs for the 100 year event for a <br />drainage azea of 188 acres. This was verified to be correct. This flow was used to design the <br />diversion channel. <br />TR09, TRtt 5-8 Revised 3/98, 8/02 <br />