10-13-08 Drainage and Flooding Committee minutes

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k lot z 4~. ass 0 cia t e s The various channel improvement and diversion pond projects range from a low of $361,000 (Project 19) to a high of $11,752,000 (Project 25). Costlbenefit ratios range from $23,000 (Project 13) to $3,078,000 per loss removed (Project 32). Total expenditures for projects will depend, of course, upon the projects selected for construction. Total cost and cost-benefit as well as availability of construction funding and the opportunities for construction phasing will have to be considered in project selection. The cost-benefit ratio of relief swales is low, but conveyance improvements, because of the high level of protection they provide, have larger costs. Some of the construction cost impacts to the City can be lessened by using alternative, less traditional funding sources such as state or federal loans or grants, joint funding of projects in cooperation with other governmental entities, or establishing a storm water utility as an independent revenue source. As the costlbenefit ratio rises, projects become less economically efficient. At some point, the costlbenefit ratio becomes so high as to render a project unreasonably expensive. Clearly some of the higher costlbenefit projects of Table ES-1 fall into this category. Precisely where the breakpoint lies between an acceptable and an unacceptable level of costlbenefit level is a matter of policy, availability and source of funds, and competition for funds. However, some guidelines for selecting a breakpoint can be identified, as described in the following. If the project (Project 32) with the highest cost/benefit (and a cost of $6.2 million) is removed from consideration, the largest cost/benefit drops to $935,000. Clearly a costlbenefit of this magnitude for removal of a loss is unrealistic. If, however, only the most cost efficient options (i.e., smallest costlbenefit) are considered among the various options (while still excluding Project options 32 and 33 for Channel F212-00-000), Projects 30, 29, 28, and 27 can be removed and the largest costlbenefit drops to $161,555 (for Project 26). The largest project cost, however, still remains at $11.8 million, just as it did before any proj ects were dropped from consideration. EN - 11 Klotz Associates Project No. 0127.008.000 January 2009 La Porte Citywide Drainage Study City of La Porte