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I I I Table 44. Benefit/Cost Comparison. I I IX. PLAN FORMULATION This section involves the selection of an improvement plan from among the alternatiqes, details the preliminary design and describes the implementation of the selected improvement plan. I I Alternative Project Installation Cost I Cooper Slou~h Reach 1 2-a $ 790,300 I 2-b 2-c 3 I 1,114,900 1,427,400 498,800 Cooper Slough Reach 2 1,905,900 2-a I 2-b 2-c I 3 Boxelder Creek Reach 1 1,340,900 2,506,400 2,749,700 2,877 ,300 I 2a-c & 3 5,500 I I Annual Cost AnnlJal O&M Cost $ 60,000 $1,800 84,600 108,300 37.900 144,700 190,200 208,700 218,400 101,800 1,800 1,800 1,900 4,140 4,140 4,140 2,880 Total Annual Cost $ 61,800 86,400 110,100 39,800 148,840 194,340 212,840 221,280 107,300 An nua I BenefIt $118,000 140,000 147,000 147,500 539,700 675,700 700,200 705,400 23,200 Table 45. Total Improvement Economic Analysis. Annua I Benflt Net 8eneflts Cost Ratio <Cost> 3.71 3.62 3.48 3.29 3.19 0.22 1.91 1.62 1.34 I Plan Selection The selection of an improvement plan was primarily baaed on the economic analysis. The economic analysis was on a ~each by reach basis and this allows combinations of the alternate plans to he considered. Besides the results of the economic analysis, selection of a plan is based on the inherent advantages and disadvantages as related to construction, maintenance, and implementation. Before recommending the final plan selection, the advantages and disadvantages of each alternative were considered. $ 56,200 53,600 36,900 107,700 I 'I I 390,960 481,360 487,360 I Alternative 1 has the economic advantage of a lack of construction costs. This is an attractive alternative when flooding is confined to a narrow valley channel. For wide, shallow flooding it is not as attractive. First, there is no guarantee that flood damage reduction will occur because existing struc- tures may not be relocated and there is no guarantee that the required legislation will be implemented to avoid further development in the floodplain. Another disadvantage is the indirect costs associated with legislation, non-developable property and future flooding. Also, it does not solve the existing problems which occur at the crossings of Boxelder Creek and the Larimer Weld Ditch and the Lake Canal and of .COoper Slough and the Lake Canal and Cache la Poudre Reservoir Inlet. Alternative 2 is a capital intensive program. It requires channels and drop structures which must be maintained by the community. Most openings on channel crossings must be enlarged which will cause temporary disruption in the community. The major advantage of this alternative, is that the improve- ments are generally confined to a narrow section along the existing channel. It solves the problems along Cooper Slough and Boxelder Creek of separating floodwaters from ditch water and prevents ponding behind existing canal and road crossings. Improvements may be implemented in a sequential manner to spread out the costs. Alternative 3 involves a moderate level of capital investment with a 484,120 I < 84,100> I , I I I Cost Annual Cost O&M Total Annual Cost Benef Its B/C I Alternative 2 Chtlnnellzatlon Net 8enef I ts I I 10 year 50 yeor 100 year 'I AI ternat Ive 3 Detention I I I 4,037,100 4,962,200 306,400 11,440 317,840 680,900 376,600 11,440 388,040 838,900 5,518,000 418,800 11,440 430,240 870,400 4,218,200 320,200 10,280 330,480 876,100 2.14 2.16 2.02 2.65 363,060 450,860 440,160 I I 545,620 I 90 I , major portion of this going for land acquisition costs. The resulting product of. this alternative requires la~ge areas of land to be put into detention I 91 I