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The original item was published from 12/16/2020 4:53:01 PM to 12/16/2020 4:53:53 PM.

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Posted on: December 16, 2020

[ARCHIVED] Groveland Avenue Levee Flood Risk Mitigation Project FAQs

Buckley Flooding Presentation - 12-6-2018 VBOT Meeting 32

What is the Groveland Avenue Levee Flood Risk Mitigation Project? 

This project is designed to prevent the repeated flooding of residential structures on Forest Avenue, Groveland Avenue, Kimbark Road, Lincoln Avenue, Park Place and West Avenue.   The project consists of a proposed floodwall on West Avenue, raising the height of the Groveland berm, and extending a floodwall east on Park Place to Woodside Road. 

Why is the project needed?

Flooding in Riverside has become more common because of climate change and upstream development.  The past three Mays have set consecutive records for rainfall in Riverside.  The two worst floods in Riverside’s history occurred in 2013 and 2020.  Rainfall predictions show this trend will continue. This leaves two choices – try to protect the area most directly impacted by repeated flooding or allow the flooding and accompanying losses to continue. 

Who is designing the project and who would build it?

The project is being coordinated and managed by the Army Corps of Engineers, but all aspects of the project are being reviewed and verified by the Village Engineer, Christopher B. Burke Engineering, Ltd.  The project has also been reviewed by the Illinois Department of Natural Resources and the Metropolitan Water Reclamation District. At this time, it is unknown who the contractor of the project will be because completion of the design phase is needed before the project can be sent out for bids. 

How much will it cost and who will pay for it?  

The total estimated cost for the project is $7,160,082. Of that amount, the federal government will pay $4,654,054. The remaining amount of $2,506,028 will be paid by the Metropolitan Water Reclamation District through an unprecedented agreement with the village. Recognizing the importance of the project in terms of storm water management, the MWRD agreed to cover the non-federal cost that normally would have fallen to the Village of Riverside. As a result of this agreement, Riverside residents will pay none of the costs for engineering, design, or base construction. If the village wants extra items not directly tied to the base project, such as aesthetic improvements to the floodwall or extra landscaping, it might have to pay for those. 

Will the project put an end to all flooding issues?

The floodwall will not end all flooding issues because there are different kinds of flooding. The project is designed to stop flooding caused by the river overtopping its banks in the affected area. Flooding within the Village also can occur when the village’s combined sewer system reaches over capacity during a heavy rainfall. Some homes experience seepage in their basements due to a high water table when the ground becomes saturated, which can occur even when there is no river flooding.  

Will the project cause increased flooding upstream, downstream, or to the west ?

No. The flooding at issue results when the river flows into a depressed “bowl” around Groveland Avenue that then acts as a reservoir of still, non-flowing water. Water will seek the lowest ground. Elevation levels in the area around Groveland dip to between 610 and 613 feet, creating the bowl. The amount of water stored in this bowl is very small compared to the flow of the river. When the river level drops, the water in the bowl drains back into the river. Preventing water from flowing into the bowl will send that water downstream, having no effect on river levels upstream, downstream, or to the west. This flood pattern was verified by modeling conducted by the Army Corps of Engineers and confirmed by the Village Engineer.  

Why does the Groveland berm need to be raised if the river has never topped it?

The project needs to be built at a height that provides the greatest protection possible. The Army Corps is required to take into account the 100-year flood level and then add two feet to provide extra insurance that the levee height is sufficient. Although no project can guarantee protection against all possible flooding, this one is engineered to provide maximum protection.

Why was Riverside selected for this project?

This project was part of a bigger watershed study that looked at ways to reduce flood damage along the Des Plaines River and its tributaries. Over the course of 14 years, hundreds of sites were analyzed. Sites that provided an economic benefit were included in a final feasibility report.  This Groveland Avenue project was identified as a priority because it will benefit a residential area where homeowners experience frequent flood damage. The study determined constructing a floodwall and heightening the Groveland berm would reduce the occurrence of flood damage in the area, producing savings greater than the cost of building the wall.

Learn more about the project here.
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