Representatives from the Village of Flossmoor presented a plan to use land near Heather Hill School to help alleviate flooding of the Flossmoor Road viaduct at the May 22 District 161 Board of Education meeting.
The plan would include the creation of a stormwater detention basin on park district land and an open field behind the school. This implementation would use an existing 42-inch drain pipe that runs parallel to the railroad tracks that cross above Flossmoor Road. The storm drain continues behind Heather Hill before turning east towards Butterfield Creek.
Bridget Wachtel, Flossmoor village manager, gave the board some background information about the persistent flooding problems the village has experienced.
She explained that the basin project would help to keep traffic moving through the Flossmoor Road viaduct. Flooding of the viaduct can slow emergency vehicle access to parts of the village during major storms. The village hopes that the basin will also help to decrease storm damage in the area.
“In September of 2019, we received seven inches of rain in twelve hours, causing an estimated $585,000 in property damage, impacting 107 properties,” Wachtel said. “At that point in time, our village board said, ‘We have to do something.’”
The village has been considering the plan for two years and has found very few options due to the lack of open land in the area. The Park District/Heather Hill field is one of the only spaces large enough to accommodate the amount of water that accumulates during a major storm.
The village has already received some funds to help pay for the plan. According to Public Works Director John Brunke, Flossmoor was awarded nearly $2 million in grants that can be used for the retention basin.
“We’re still pursuing other grant money to help bolster this project, said Brunke. “The estimated cost is about $7.8 million total for everything.”
Brunke said that they will continue to seek additional aid over the coming months and are hopeful that the construction phase of the project will begin next year.
Matt Moffit, an engineer from Baxter and Woodman (the firm hired to plan the project), explained that the detention basin would be an open design. The park district tennis courts would need to be removed and the soil would be excavated at the site. The open pit would then be planted with native prairie plants that would help to filter and drain water from large storms.
“This is a dry bottom basin,” Moffit said. “There is no water except during flood events. It will fill up and drain down within nine hours after a 10-year storm event.”
District 161 board members expressed concerns and asked questions about the risk the detention basin would pose to children at the school.
Board member Michael Rouse II said, “Regardless of how quickly there is going to be a significant amount of water, there is a risk for children of drowning. I would be in favor of something that minimizes that risk.”
Rouse expressed apprehension about the four-foot fence depicted in the plan drawings, believing it might encourage children to enter the area and suggested a taller fence. Wachtel explained that the height of the fence is regulated by code, and a six-foot fence is the tallest permissible.
Assistant Public Works Director Dan Milovanovic showed the board several examples of similar basins in the area. His examples were also adjacent to schools or playgrounds and did not have large fences to keep children out. Instead, tall native plantings served as a deterrent to entry. The village offered to pay for any fencing and educational signs explaining the purpose of the basin and the native plants.
Board members asked what would happen in a 100-year rain event if this retention basin was only designed for a 10-year event. Moffit informed them that rain events larger than the design could accommodate would result in flooding of the viaduct and other sites upstream. This would not pose any additional flooding risk to the school.
Maintenance on the basin would require controlled burns. These regenerative prairie fires are usually prescribed every three years. Brunke said that this type of maintenance would be scheduled on weekends or when students were not present.
The village representatives stressed that they were willing to discuss the project further with school officials and other community members. The plan will require an agreement with the park district in addition to the easement from the school district. The groups concluded that they would meet again with more information as many factors are considered.