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 and the high water table in the area, conventional storm sewer construction is not practical in many areas. 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 has also included installation of new sanitary sewers utilizing a vacuum system.
Phases I thru X are complete and included construction of the vacuum sewer pump station, Huron Circle, Aztec Street, Blackhawk Street, Osage Street, Victor Street, East Navajo Street, and the south half of Pickard Lane. Phase XI is complete with minor punch list items remaining, and included the north half of Pickard Lane from Hall Walk Road north to Navajo Street. Phase XII is nearly complete and included the installation of vacuum sewer along Navajo Street from the pump station to Comanche Street.
This project is included in the FY25 CIP with a budget of $1,300,000 in Local Option Sales Tax funds and $450,000 in Sewer funds. The limits for Phase XIII will be Mohawk Street from Navajo Street to Comanche Street and Comanche Street from Navajo Street to Mohawk Street. It may be possible for this phase to be constructed with gravity sewer and concrete pavement. A final determination will occur during design.
Reconstruction of Mohawk will allow new housing lots to be developed on the City owned property located along the east side of the street.
EGA will continue as the project engineer. They were 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.