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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />4.3 EXPAND GREEN RIDGE GLADE RESERVOIR <br /> <br />CDM was directed by the City to evaluate two sites for providing additional <br />storage: (1) expansion of the existing Green Ridge Glade Reservoir, and <br />(2) construction of a new reservoir at Maitland Canyon. This section of <br />the report summarizes the results of the Green Ridge Glade analysis. <br /> <br />Various increases in capacity at Green Ridge Glade were modeled to <br /> <br />determine the effect on the Design Condition deficit. It was assumed that <br /> <br /> <br />the reservoir would operate in the future as at the present; i.e., excess <br /> <br /> <br />Transfer Decree water would be stored and then withdrawn for use when <br /> <br /> <br />other supplies have been exhausted. Storable waters would be diverted from <br /> <br /> <br />the Big Thompson River through the Dille Tunnel and Charles Hansen Feeder <br /> <br /> <br />Canal into Green Ridge Glade Reservoir. <br /> <br />Topographic and engineering data available from previous engineering <br /> <br />studies of the Green Ridge Glade site were used to develop area-capacity- <br /> <br />elevation relationships and costing information for this evaluation. <br /> <br />Construction of additional reservoir storage capacity at Green Ridge Glade <br />could result in elimination of the 100-year deficit. The active (water <br />supply) capacity of the reservoir required is 4,550 AF. Figure 4-4 <br />illustrates the 100-year deficit which would result from various active <br />reservoir capacities. The amount of storage required per AF of deficit <br />reduction increases from 1.2 AF for storage less than 2,500 AF to 1.8 AF as <br />storage increases beyond 2,500 AF. <br /> <br />Based on preliminary hydrologic analyses of the Green Ridge Glade site, <br /> <br /> <br />approximately 500 AF of additional capacity would be required for <br /> <br /> <br />protection against a probable maximum flood (PMF) resulting from a 24 hour <br /> <br /> <br />rainfall of 34 inches. \lith allowance for a flood pool, the total capacity <br /> <br /> <br />required is then 5,050 AF. The location and area of inundation of a 5,050 <br /> <br /> <br />AF reservoir at Green Ridge Glade is shown on Figure 4-5. The normal water <br /> <br /> <br />surface elevation of 5,346 feet above mean sea level (ft msl) corresponds <br /> <br />4-18 <br />