Laserfiche WebLink
2-49 <br />DRAINAGE FACILITIES <br />The layout of drainage facilities, including the design points, disturbed area, <br />culverts and ditches, are shown an Figure 2.2-3. As shown in Table 4.2-10, peak flows <br />from D- 1, D-2 and D-3 are less than 7 cfs when routed together at the pond. Designs <br />for the ditches flowing into and out of the pond are calculated in Table 4.2-13. <br />Runoff volume from these three areas during the 10-year storm total 0.34 <br />acre-feet, as shown by the values on Tabie 4.2-12. The volume of runoff for the 25, 50, <br />and 100 year storms are also shown on this table. In addition, 0.1 acre-feet of <br />sediment storage for each disturbed acre is also provided. <br />2.4.4.1 Alternate Sediment Controls <br />Three areas within the permit area are to have runoff controlled by alternate <br />means. These areas are the Office Area, Construction Material Stockpile and the <br />Topsoil Stockpile. Run-off from the three areas will be filtered through silt fences. The <br />following table lists the length of the silt fences. The 1.7-inch, 10-year event was used <br />to size the sediment fences. <br />Area Peak Flow (cfs) Length of Silt Fence <br />Office Area 0.35 16-feet <br />Construction Material 0.14 14-feet <br />Topsoil Stockpile 0.18 16-feet <br />Calculations confirming the adequacy of these controls are contained in Appendix M. <br />Berms or ditches will be constructed to direct run-off into the silt fences. The <br />berms/ditches will form triangular ditches at least 0.6 feet deep with 1.5H:1 V side <br />slopes. See Appendix M for ditch sizing calculations. <br />M`Clane Volume 1 1/02 <br />