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001811 CONCEPTUAL PLAN OF IMPROVEMENT As the result of the June, 1985 flood, the need for upgrading the levee system at Alamosa has become a priority for action within the community. Local, State and Federal representatives have developed an overview of the types and extent of improvements needed. This report has taken those improvements a step further by refining the specific extent of improvements and identifying an initial estimate of costs for the improvements. The extent of the proposed conceptual improvements are shown on Sheets 1 to 4 of 4. A typi cal secti on of the type of levee improvements anticipated is shown in Figure 8. All features shown in Figure 8 may or may not be required along the total length of the levee system and vari ati ons in the extent and amount of these improvements wi 11 vary from section to section. , ; , A brief description of the types of improvements proposed for the various reaches of the river is provided in the following paragraphs: I A. South (right) side, D&RGWRR to Sewer Lagoons The hydraulic analysis in this area indicates that the existing levee is of sufficient height to provide the required freeboard. Improvements in thi s area i ncl ude access control, ri prap at the downstream side of the railroad bridge, and removal of the sandbar at the railroad structure on the downstream side. I B. North (left) side, U.S. 160 to D&RGWRR Improvements in this reach include the reconstruction of the easterly levee for about 400-feet upstream of the railroad and for about 1200-feet downstream of the U.S. 160 bridge. Reconstruction would consist of the removal of a portion (land side) of the levee and rebui lding a wider levee embankment with select and on-site material. The existing levee near the railroad bridge would likely be removed in total and then rebuilt. Fence removal and replacement would be included to provide access control for mai ntenance. A wet well may be constructed to permit emergency pumping of surface runoff from the land side to the river upstream of the railroad bridge. Riprap slope protection is planned ups t ream of the rai 1 road bri dge and at the U.S. 160 bri dge to protect the levee from erosion. Improvements would be made, also, to the diversion dike for the West Side Ditch. The existing dike would be rebuilt to a specified elevation height to divert water as required for low flow conditions. At higher flows, the dike would be built overtopped and breached so as to provide additional channel capacity for the flow events. l ~ t- " -19-