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I I I I I I I I I I I I I I I I I I I -;29- flood and would be very difficult to keep open and clear. Should the structure plug with debris and the road overtopped, it is probable that washout will occur. Existing traffic needs may not require: replacement of the structure until it is washed out during a flood. with the structure plugged with debris the IRF floodplain comes very close to existing dwellings along the west bank. If the bridge is kept open the floodplain is below the level.of the housing, based upon the topographic mapping, although erosion could cause a flooding problem to develop. Broken Lance Road (D/S) .to villaqe Road Both IRF and SPF floods are within the general channel area through the u/s portion of this reach. A pedestrian crossing structure is likely to be damaged or washed out under IRF con- ditions. One building on the east bank is very close to the floodplain and is likely to receive some flood damage during both IRF and SPF conditions. The main factor contributing to floodwaters leaving the river channel is the Four Seasons Pond Dam. The small dam in the Blue River near the Four Seasons shopping center has a spillway of very minor capacity. The structure is shown in Figure 4 in the Breckenridge Flood plain Report. The capacity of the spillway is approximately 300 to 350 cfs. The flooding potential at this point can be reduced by enlargement of the spillway. It is not practical to enlarge it towards the east or the Four Seasons area, but an enlargement could take place towards the west. To pass the peak 100-year flood with no flooding of the Four Seasons shopping area would require a spillway of crest length approximately 120 feet. The dam is less than 10 ft. high and therefore does not come under the administrative control of the State Engineer of Colorado. Over- topping and failure of the dam can cause damage to the village Road crossing located below the dam and could conceivably cause additional flooding to development in the vicinity of village Road crossing. The crossing at Village Road consists of two corrugated metal pipe culverts of 8 foot diameter. The capacity of this structure is adequate to pass the lOa-year storm providing debris has not accumulated to block the flow. Some erosion could occur at the downstream end of the structure. The upstream is in reasonably good condition. This structure is one of the better ones wi':h- in the town and would likely be one of the last to be replaced with a bridge should such a program be undertaken. Because of ~ Leonard Rice Consulting Water Engineers. Inc.