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and Associates, Inc. (Wheeler) to evaluate the storm drainage and flood <br /> management requirements for Pond 1.2 in accordance with the requirements of <br /> the DMG. Wheeler and Henderson determined that storm water run-of and run- <br /> off and floodwaters would be handled and treated by constructing a series of by- <br /> pass interceptor ditches around the pond to direct storm waters to a settling <br /> basin prior to discharge. Additionally, final grading and capping of the pond <br /> would be engineered to direct sheet flows to these ditches. The following <br /> information is contained within or excerpted directly from the Wheeler report to <br /> Henderson. Figure 4 consolidates the engineered drainage plan, drainage area, <br /> and shows ditch cross-sections. Data used in design calculations are found in <br /> Appendix E. <br /> The proposed drainage and flood management system for Pond 1.2 will intercept <br /> runoff from 10 year rain, snow, and rain-on-snow events, treat and remove <br /> sediment from the runoff prior to discharge. Designed interceptor ditches will <br /> • discharge higher magnitude storms up to 100 year events with at least 2 inches <br /> of residual freeboard. The existing sediment trap north of Pond 1.2 will have <br /> capacity that meets the criteria for water quality management of runoff as <br /> prescribed by the Urban Drainage and Flood Control District for the metro <br /> Denver area. <br /> 2.3.1 Design Criteria <br /> 2.3.1.1 Design Storm <br /> Snowmelt often exceeds runoff from rainstorms in higher mountain areas such <br /> as found at Henderson. However, both types of events and the flooding each <br /> might present require evaluation relative to Pond 1.2. <br /> 6 <br /> June 33.1999 <br /> rn.ax <br />