Web Extra! Download a .pdf of the flood report
The task force created to study issues related to the Sept. 12-13 flooding on River Forest released a 25-page report to the village board Monday night.
The eight-person group, chaired by resident Rick Gillis, was formally named the Task Force to Study Sewer System and Flooding Issues. It met nine times between November and April, including with engineers from the Metropolitan Water Reclamation District. Its primary task was to develop a comprehensive understanding of what occurred in September, and determine what needed to be done to avoid future problems.
In addition, several trustees pressed former village president Frank Paris in October to have the task force to determine what the village may have done wrong during the flood. That was not done in the final report.
Public Works Director Greg Kramer, who sat on the task force, began by giving the board an overview of the flood, said the task force had met formally nine times, including with engineers from the Metropolitan Water Reclamation District. He asked that the report be referred to either the board’s public works committee or to a committee of then whole for detailed presentation and discussion.
“Due to the complexity of scope, and due to the fact that many of the recommendations contained within this report involve an expenditure of funds or capital outlay, we thought it would be most appropriately referred to either the public works committee or to the board as a whole,” Kramer said.
Based on how they decide to proceed, Kramer said, the village board will likely face additional budgeting decisions related to flood mitigation.
Kramer added that the work is not yet completed, saying, “We hope to be in existence until all flood mitigation recommendations to the board are in place,” he said. He urged that as many members of the task force as possible be involved in the committee and board discussions.
The report noted that in September the Des Plaines River crested 14 inches higher than it did during the last major flood, in 1987.
Among other the key points:
The Metropolitan Water Reclamation District does not control or obstruct the Des Plaines River. The river’s water level is determined by overland water runoff.
When the multi-tunnel Deep Tunnel system is at full capacity, “MWRD gives priority to emptying the Des Plaines River tunnel over other sections of the tunnel to reduce flooding potential of the Des Plaines River.”
The Lake Street sewer system west of Thatcher runs west to First Avenue in a “siphon chamber” under the river. “When there are severe water levels, this siphon chamber may not work as designed, and possibly could reverse flow back into the Lake Street sewer system.”
The report makes three primary recommendations regarding the sewers:
Have a consulting engineer conduct a study of the Lake Street sewer system to determine the “optimum design requirements” to prevent future flooding, possibly including a pump station, a relief connection to the upper Des Plaines interceptor, or a cross connection to the Thatcher sewer system.
As a short-term solution, buy a sufficiently powerful portable pump to direct sewer and flood water back into the Des Plaines, something allowed in flood emergencies.
Perform a village wide re-survey of downspout connections. Property owners will be required to disconnect their downspouts from the sewer system to avoid over-taxing the sewer system.
A major concern is an earthen berm just north of Lake Street and east of the river. Key findings by the task force are that the berm, constructed in 1988, would be “difficult” to construct today because of current state and federal environmental laws. The laws do allow the berm to be repaired to 1988 conditions, but any further improvements will require an involved and time consuming permitting process involving numerous state and federal agencies.
The task force recommended a two-part approach, starting with improvement allowed under the original Forest Preserve District license. That would extend the berm to the north and the south, work permitted but not done under the original 1988 plan.
Phase two work would pursue permission to extend the berm to the northeast, toward Edgewood Place.
In addition, the task force recommends investigating “other overland flood control alternatives such as removable fences or barriers.”
Such a system, they say, would allow public works crews to more quickly set up flood barriers, rather than relying on sand bagging, which notes was “both labor intensive and time consuming.”
The issue of a resurvey of residential downspouts raised a concern with President John Rigas, who said, “It’s my understanding that what happened is the September flooding was caused by overflowing of the river.” When Kramer confirmed that, Rigas suggested that that requiring residents to disconnect downspouts might be unnecessary.
Kramer said there were a number of flooded basements, and that the task force did not focus solely on the river overflow.
“It’s not just the river that was looked at,” he said. “The sewer surcharging was also looked at.”
Trustee Cathy Adduci, who serves on the public works committee, praised the report’s overall recommendations, and asked Kramer to have the task force prioritize the recommendations contained in the report.
“Absolutely,” Kramer replied, saying the task force would meet again prior to sitting down with the public works committee.