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XI-3 Utility Crossings. The design and construction of utility crossings, either under the river bed or overhead, should not cause increased flood hazards or an increase in flood water surface. Such crossings should allow for river bed degradation of at least three feet without causing an obstruction. Existing crossings which already create or contribute to flood or erosion problems should be modified. Regional Recreational Plans. South Platte River parks and recreation devel- opment plans, gravel mine operations and permits, and river corridor devel- opment shall be fully coordinated with regional recreational plans of the various governmental entities, or groups of entities. Drops and Check Dams. Design of river flow obstructions such as drops and checks dams must consider the impact of construction on the flood carrying capacity of the channel. Design Criteria The following specific criteria are used to develop alternatives for this Master Plan. Groundwater. The quality and quantity of the alluvial groundwater in the natural floodplain of the South Platte River should be protected from dete- rioration and diminution. Flood Hydrology. be compatible and Table 111-5. All planning and design for the South Platte River shall in accordance with the following design floods given in Inactive Gravel Mines. Flood hazards should not be increased over natural South Platte River floodplain conditions due to the presence of unman aged inactive gravel mines. Normal flood period releases from Chatfield, Bear Creek, and Cherry Creek Reservoirs may be up to 5,000 cfs. Such releases for planning and design are not to be added to floods generated downstream of the dams due to rainfall occurrences. Active Gravel Mines. Mining of gravel in the natural floodplain of the South Platte River should be undertaken in a manner so as not to increase flood hazards or adversely impact the quality or quantity of surface and groundwater. Low Flow Hydrology. Average monthly low flows in the South Platte River, based on a dry year analysis, for near term planning and design purposes are listed below. Low flow hydrology for future years under changed municipal water supply river and reservoir operations are discussed in Section V. Mining Requests. All applications for gravel permits should include en- forceable post mining reclamation plans containing post mining land use pro- posals for approval, realizing that not all gravel pit lakes can be prudent- ly utilized for recreation, and further that a 20-mile long reach of the river in Adams County should not be a river of water filled holes. Littleton Denver Henderson Gage Gage Gage Month (cfs) (cfs) (cfs) January 39 78 163 February 44 84 229 March 56 95 168 April 51 102 197 May 82 218 405 June 164 229 539 July 274 294 519 August 146 197 311 September 58 88 215 October 42 67 144 November 60 116 173 December 36 84 221 Floodplain Management Program. The South Platte River corridor should have a floodplain management program throughout its entire 40 mile reach. Parti- cular emphasis should be placed upon floodplain management between Sand Creek and Baseline Road (Brighton).