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I I I. . I I I I I I I I . I I I '. . . I The alternatives presented are for the 100-year frequency storm. Many alternatives exist for the range of frequencies from no improve- ments to the 100-year improvements. It is reasonable to use frequency as an alternative and allow residual flooding when using frequencies less than the 100-year storm. Damages resulting from the residual flooding are less than that for the 100-year storm; however, due to the flat terrain, the differences are not great. Many times, the selection of which storm frequency to design for is not made by the amount of damage reduction, but is made by the cost of the project. After each basin discussion, where appropriate, a graph is presented that shows the relationship between the flow, pipe size, and fre- quency,.to serve as a means of extrapolating flow rates and pipe sized for more frequent storm events. In order to prevent deterioration of the existing curb and gutters, major grade changes would be required. Street and gutter slopes should be increased to minimize slopes of 0.4 to 0.5 percent. It is recommended that these changes be gradual over several years as the streets need reconstruction. Currently, the streets are so flat that water ponds at several places, usually not at inlets. It ap- pears that the grade changes can be fitted with existing development. Most changes would occur in the middle of the block, in Basin III for instance, as inlets are at the intersections. Costs have not been included as the replacement wouldb~ normal city maintenance. 1. Basin I The area west of Design Point 2 is mostly undeveloped. Depend- ing upon how it is developed, significant increases in flow to the developed areas could be experienced. To avoid this un- known situation, this basin is to be divided at Design Point 2. -27-