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12-18-85 <br />Due to the ephemeral nature of Coal Gulch, the channel will be covered i <br />• with topsoil similar to other backfilled and graded areas and seeded <br />with a seed mix shown in the reclamation plan. <br />Stipulation No. 11 <br />Within thirty (30) days of permit issuance, the applicant must submit to <br />the Division a plan for erasion control of the temporary Caal Gulch <br />diversion adequate to handle the velocities of the 10-year, 24-hour <br />storm. This plan must be approved prior to implementation. <br />Stipulation No..ll Response <br />As shown in Exhibit 1, Drainage and Sediment Control Plan Calculations <br />for Ditch No. 1, the velocity of flow for the 10-year, 24-hour event has <br />been calculated for several segments and are within the range shown in <br />the Drainage and Sediment Control Plan Appendix, Appendix 1. Therefore, <br />the riprap as designed for the 100-year, 24-hour peak flow is more than <br />adequate for the 10-year, 24-hour peak flow. The large riprap for the <br />100-year, 24-hour peak flow has been installed in the Coal Gulch <br />temporary diversion channel. <br />• <br />Stipulation No. 12 <br />The applicant must submit adequate designs for the culvert conveying <br />flows from the Coal Gulch diversion under the haul road within thirty <br />(30) days of permit issuance. These designs must be approved by the <br />Division prior to any haul road construction. <br />Stipulation No. 12 Response <br />As shown in Exhibit 1, Drainage and Sediment Control Plan Calculations, <br />the peak flow from a 10-year, 24-hour precipitation event is 183 cfs. <br />from the nomograph titled B-9, Headwater Depth for Corrugated Metal Pipe <br />Culverts With Entrance Control (U.S. Bureau of Public Roads) on page 566 <br />of Design of Small Dams, 1974, a 76 inch diagram CMP will carry the peak <br />flow with 0.3 foot of head. <br />Stipulation Na. 13 <br />Within thirty (30) days of <br />• disturbance, the applicant <br />designs for the west ditch <br />24-hour storm. The designs <br />prior to this stipulation bi <br />permit issuance and prior to any additional <br />must submit to the Division for approval, <br />adequate to pass the flows from a 10-year, <br />must be approved in writing by the Division <br />ping satisfied. <br />-5- <br />