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1 <br />' REVISED <br />7/30/85 <br />Runoff parameters and watershed characteristics were utilized in <br />' deriving total runoff and peak flow for each sub-watershed, using the <br />methods outlined in Procedures for Determining Peak Flows in Colorado <br />' (SCS, 1977). Total runoff was used to design impoundment structures; <br />peak flow rates were used to design diversion ditches, culverts and <br />' outlet works. <br />Sedimentation Parameters <br />The established design criteria for drainage and sediment control <br />facilities is the amount of runoff resulting from 10-year, 24-hour <br />precipitation event. Therefore, the sediment storage capacity of a <br />' sedimentation pond should be adequate to store the volume of sediment <br />generated by a 10-year, 24-hour precipitation event at all times. The <br />method of determining this volume is to calculate the total runoff and <br />' peak flow for the design event and insert these values in the Modified <br />Universal Soil Loss Equation (MUSLE). This method is described in <br />' Applied Hydrology And Sedimentology For Disturbed Areas (Barfield, <br />Warner and Haan, 1981, pp. 365-380). The sediment yield thus derived <br />is the minimum allowable storage volume of the pond. Since the <br />permanent pool area must be cleaned out when it is 60 percent full of <br />sediment, the storage capacity is calculated by multiplying the 10-year, <br />' 24-hour sediment yield times 100/40. Thus, even when the permanent pool <br />is 60 percent full of sediment, there is adequate capacity to contain <br />' and treat the 10-year, 24-hour event. This method was applied to Pond E <br />and the detention basin at the Fish Creek Tipple. <br />' SEDIMENT CONTROL FACILITIES <br />Sedimentation Pond E <br />The_design of Pond E and associated"ditches-and -culverts-was-apps~wed~by <br />~he CM-LR_D_`und_er a Technical Revision to Permit 76-16 on March 18, 1983. <br />' The pond is located in the southwest -quarter of Section 2, Township 5 <br />North, Range 86 West, and receives drainage from tfie Fish Creek Tipple <br />facilities. Tributary disturbed area is 24 acres; tributary undisturbed <br />-3- <br />