Recommended Plan for the Appleton Drain
Three alternative plans were prepared to separate stormwater from irrigation flows and covey the 100- year flows from the fully developed watershed to the Colorado River.
Table 14 presents a qualitative evaluation of the alternatives considered. The recommended plan is Alternative 3 with pipes for conveyance and three regional detention and water quality ponds. Alternative 3 would provide 100-year detention for the entire watershed and treat water quality for the area within the 201 Boundary, resulting in the lowest system flows of the three alternatives.
Because of costs for easements and land acquisition for the three detention ponds, Alternative 3 is not the least expensive option. However, Olsson believes
it provides the best long term benefit since it would provide detention and water quality for existing and future development, and causes the least amount of construction and maintenance disturbance at the I-70 and railroad crossings.
The costs for the regional detention and water quality ponds could be offset with fees-in-lieu of requiring future development providing on-site detention and water quality.
Alternative 1 offers no detention or water quality treatment, which results in this alternative having the highest peak flows at the system outfall. Consequently, this alternative has the largest conveyance facilities and the highest costs. Alternative 2 assumes future development would provide its own 100-year detention and water quality. This lowers the total flows throughout the system and reduces the size of the conveyance facilities. However, this alternative would provide stormwater treatment for only those properties that currently have detention and water quality facilities installed, and for future development.
Total Project Cost $25,082,343.00
Annual Maintenance $245,174.00