Dam helps flood Warrenville, report says

A dam designed to keep Naperville properties dry may contribute to flooding upstream in neighboring Warrenville during extreme rainfalls, according to a newly released report.

But Warrenville shouldn't push for dramatic changes to the way DuPage County operates Fawell Dam, according to the panel that prepared the report. Instead, Warrenville's Fawell Dam Workgroup is recommending that city and county officials work together to make some operational changes while focusing on projects that alleviate flooding.

“The dam isn't the cure-all for us,” said Ronald Mentzer, Warrenville's community development director. “There's other things that can be done that we can get better benefits from. But most of those other things are controlled by the county. Therefore, we need to work in coordination with the county to move these flood mitigation projects forward as quickly as possible.”

Warrenville residents have long suspected that the city's flooding problems partially were caused by Fawell Dam, which is along the DuPage River's west branch in the McDowell Grove Forest Preserve near Naperville, but there wasn't any conclusive evidence.

After severe flooding in September 2008, Warrenville hired a consultant who did an analysis of what would happen to flood elevations in the city if Fawell Dam's gates are left open.

What the new study found was that “the dam may contribute to increased flood elevations as far north as Williams Road” in Warrenville.

“It is possible that in the largest (storm) events ... the operation of the dam could have an impact on flood elevations in Warrenville that wasn't shown under the old modeling,” said Mentzer, who served on the panel.

But DuPage legally is obligated to operate and maintain the dam, which was restored a decade ago. So the report concludes the structure won't be removed “anytime in the foreseeable future.”

Meanwhile, city officials concede there are other factors — including increased construction upstream and the development of the Cantera area — contributing to the flooding issues.

One factor the city has identified is that bridges at Williams, Warrenville and Butterfield roads can sometimes impede the flow of river water.

Warrenville is planning to replace the Williams Road bridge in 2013, officials said. And the bridge along Butterfield will be rebuilt as part of the state's widening of the road.

When it comes to the Warrenville Road bridge, city officials are hoping the county will rebuild it sometime in the future. There is no funding for the project.

Something that could help in the meantime is if DuPage removes sediment underneath the Warrenville Road bridge to improve water flow. County board member Jim Zay said officials are working to find money to do that work.

The county also has an updated watershed plan for the DuPage River's west branch that identifies a list of possible projects that could reduce flooding in Warrenville.

“We're committed,” Zay told Warrenville city council members Monday night. “We're going to do everything we can to make this right and move forward and alleviate the flooding for the people of Warrenville.”