Background/Discussion
The area of East Manawa is very flat with open ditches. There are no storm sewers in this area and the streets are thin asphalt or seal-coated rock roads. During rainfall events, considerable surface ponding occurs due to the poor drainage.
Due to the narrow right-of-way (30 ft.) and the high water table in the area, conventional storm sewer construction is not practical. The use of porous pavement in conjunction with a drainable granular base and shallow subdrain/conveyance system was determined to be the most cost effective means available to improve the area drainage.
The rehab program also includes installation of new sanitary sewers utilizing a vacuum system.
Phase I and II of the program have been completed and included Huron Circle from Navajo to north of Osage Street. Phase III of the program was construction of the sanitary sewer vacuum pump station. Phase IV included the first phase of vacuum sewer installation with the porous pavement and subdrain system on Huron Circle from Navajo to just west of Blackhawk Street. Phase V is complete and continued the rehab along Huron Circle from just west of Blackhawk Street to 585 feet east and Osage Street from Huron Circle to Victor Street. Phases VI and VII are now complete and included Blackhawk Street, Victor Street from Osage to Blackhawk Street, and Aztec Street from Huron Circle to Victor.
Phase VIII is currently under construction and includes Victor Street and Aztec Street from Victor to the south.
This project is planned for the FY21 CIP and includes a budget of $1,000,000 in Sales Tax Funds. The exact limits for Phase IX will be determined during the project scoping.
EGA was previously selected from the pre-qualified list of engineers because of their successful project history and strong relationship with the Iowa DNR, and subsequently provided engineering services for the previous construction phases. As before, they will be partnering with FOX Engineering who developed the master plan for the East Manawa area, and have been part of the engineering team on each of the previous phases. It is appropriate for the EGA/FOX team to continue their role as project engineers.