Drainage_and_Flooding_Final_Report-dated_06-16-2008

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Mr. Ron Bottonm June 16, 2008 Page 4 of 6 k I o t z a s s o c i a t e s Alternative 3 includes the placing of inlets at the entrance of the park to collect the sheet flow from a larger storm event of Creekmont Subdivision Section 2 and directing the flow with. storm sewer pipes to Big Island Sough within a 10 foot easement that the City owns (see Exhibit 7). Alternative 3 is a completely separate system that will convey only the "Additional Drainage" Areas of 48.6 acres to Big Island Slough shown in Exhibit 3. This system will go across the pipeline corridor that is to the east of Creekrnont Park. A survey needs to be conducted before this alternative can be finalized. It is assumed that the pipeline easement will not interfere with the Alternative 3 storm sewer system, but if it does, a siphon may be required to cross the pipeline corridor. This alternative will not connect to North H Street or be in the 1R.ight=of=Way of North H Street and will have its own outlet at Big Island Slough. Table 5 show the pipe sues and cost estimated for the 5-, 10-, 25-, 50-, 100-year storms. Alternative 3 will require HCFCD review and approval since new outfall would be required. Same additional Right -of -Way and/or construction easement may be required for this alternative and the costs for these are not included in the cost estimate. +'fir � �� f � �- f• r �: a The initial assessment of the data shows that any of the alternatives will collect the sheet flow from a larger storm event from the Creekmont Subdivision Section 2 at the location of the Creekiriont Park entrance. The alternatives show possible ways to convey this flow to provide some relief Creekinont Subdivision Section 2. Alternative 1 consists of 910 feet of pipe that will connect to the existing storm sewer on North H Street. The total cost estimate for alternative I will range from $344,000 to $428,000 depending on what storm event is chosen (refer to Table 6 for details). Alternative 2 consists of 1,885 feet of pipe that will connect to North H Street and run parallel on North H Street. The total cost estimate for alternative 2 will range from $725,000 to $1,294,000 depending on what storm event is chosen (refer to Table 7 for details). Alternative 3 consists of 1,322 feet of pipe that will outfall into Big Island Slough. The total cost estimate for alternative 3 ranges from $474,000 to $571,000 depending on what storm event is chosen (refer to Table 8 for details).