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PROPOSED
CHANNEL
EXISTING
CHANNEL
IOWA RIVER
STREAM
STRUCTURES
www.tetratech.comTBPE Firm No. F-3924
HIGH TERRACE
WETLAND AREA
IOWA RIVER WETLAND
AREA
HIGH
TERRACE
RALSTON
CREEK
RESTORED
FLOODPLAIN
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PROJECT OVERVIEW:
Iowa City’s history as the former state capital and home to the University of Iowa is richly intertwined with the Iowa River. Even with the Coralville Reservoir controlling
much of the watershed upstream, Iowa City has experienced several large floods and has realized extensive damage to many city and university properties. As Iowa
City continues to grow, much of that growth is focused on moving critical infrastructure out of the floodplain and providing effective management and safe access to
the Iowa River corridor. One such project is the decommissioning and demolition of the North Wastewater Treatment Plant, located at the confluence of the Iowa
River and Ralston Creek north of Highway 6. The demolition of the plant will allow for the restoration of a 5-acre site back to a natural stream/wetland complex. The
proposed concept includes adding meanders to the straightened Ralston Creek to improve flow conditions and stream habitat. Cross vanes, root wads, and soil lifts
will be incorporated to maintain stability of the revised stream pattern. The new stream geometry will result in a wider floodplain on the east side of Ralston Creek.
The west side of Ralston Creek will be lowered to create a wetland area to improve water quality, provide additional flood mitigation, and establish a diverse
ecosystem. The wetland connect to groundwater sources to maintain hydrology but will accept storm flows from Ralston Creek to maximize water quality treatment.
The wetland will be hydraulically connected to Ralston Creek and the Iowa River but physically separated by high terraces, consistent with natural streams typically
found throughout Iowa.
SECTION D-D'
PLAN VIEW
LOCATION MAP
EXISTING CONDITIONS
NORTH WASTEWATER TREATMENT PLANT RESTORATION
2014 GREEN INFRASTRUCTURE TECHNICAL ASSISTANCE
PROGRAM - IOWA CITY, IA
ROCK VANE
FLOW
SOIL LIFT
ROOT WAD
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