Agenda Item 12: Lake San Cristobal Natural Lake Stabilization Issues

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Page 2 Heavy runoff occurring during the mid 1980's severely damaged the already deteriorating structure. The lake was lowered to a point that caused concern of a repeat of the events of the 1950 Temporary measures were installed to help maintain the lake's water level and provide a level of erosion protection. The measures consisted of placing large boulders across the outlet channel at the upstream side of the old timber structure. These measures have maintained the lake surface and prevented further deterioration of the channel. County personnel fear that everything could fail during the next heavy runoff. If the temporary measures fail during high water, extensive flooding will occur downstream. Damages to homes and buildings will be considerably more severe than before because of increased downstream development. A new highway bridge constructed 100 to 200 feet downstream of the old structure would also likely be lost or severely damaged. Severe damage is likely throughout the county in areas along the Lake Fork of the Gunnison River. The area, heavily dependent upon summer recreation, will be severely impacted. A foundation investigation of soil materials was made at the bridge site prior to its construction. The investigation found extremely soft materials at depths below the surface armoring. Because of the weak foundation conditions, the bridge was placed on spread footings rather than piling. The existing structure is 80 feet wide. The design flow is not known. The overfall at the structure is about two feet. The channel downstream is fairly steep. A new structure would likely require a designed drop of three to four feet. conclusions: This is a worthwhile project that must be done. If repairs are not made in the outlet channel of Lake San Cristobal, it is just a matter of time before the recreational values of -the lake are destroyed. Without the lake, the tourist economy of the area will suffer This has all of the requirements of being an excellent RC &D type project. Economic development, environmental problems, flooding, and erosion control are are all components of this proposed measure. The RC &D Program is an excellent area in which to help the county raise the necessary funds to correct this problem.