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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 />Chapter IV - Formulation of Alternatives <br /> <br />reservoir and allowing the reservoir to dry for several months, then removing the sediment with <br /> <br />excavation equipment. It is anticipated that approximately 100 AF or approximately 150,000 CY <br /> <br /> <br />of material could be removed economically. The normal reservoir storage to the spillway crest <br /> <br />will be approximately 450 AF after dredging the reservoir. <br /> <br />Table IV-l <br />Reservoir Sediment Results <br /> <br />Reservoir Elevation Original Storage 2000 Storage Change in Storage <br /> (AF) (AF) (AF) <br />6892.0 0.00 0.00 0.00 <br />Intake inlet elevation <br />6895.0 3.80 0.00 -3.80 <br />6900.0 30.52 0.00 -30.52 <br />6905.0 96.46 7.94 -88.52 <br />6910.0 205.84 72.75 -133.09 <br />6915.0 365.77 162.D1 -203.76 <br />6920.0 587.22 307.93 -279.29 <br />6925.0 866.64 527.10 -339.54 <br />6930.0 1,170.84 817.88 -352.96 <br />6931.5 1,270.04 916.04 -354.00 <br />Dam crest elevation <br /> <br />E. Breach and Restore Alternative <br /> <br />A possible alternative to rehabilitating the: dam is to breach the structure and restore the <br /> <br /> <br />surrounding areaback to its natural condition. Breaching the dam will require environmental <br /> <br />studies to determine what impacts the removal o{the structure would have on existing wetlands <br /> <br /> <br />and wildlife habitats. The breach and restore alternative presented in Figure IV -14 will maintain <br /> <br />a natural upstream environment, which will sustain the wetlands and wildlife habitat. The <br /> <br /> <br />alternative will also allow the passage of flood events without increasing upstream flood stages. <br /> <br />This alternative involves removal and disposal of the existing embankment material and <br />outlet works, construction of a drop structure to transition from the existing reservoir invert to <br />the downstream invert, and local downstream channel improvements. Figure IV -17 shows an <br />articulated block lined channel would be constructed with a 150-foot bottom width along the <br /> <br />Monument Lake Dam Feasibility Study <br /> <br />30 <br /> <br />BOYLE <br />