It’s a Marseilles tradition to which city officials are happy to bid farewell: sandbagging the city’s sewage treatment plant when a rain-swollen Illinois River rises to flood level.
The fix is going to be a new 1,210-foot-long sheet pile floodwall that will wrap around the treatment plant and add another 5 feet of height protection.
Last month the U.S. Department of Homeland Security’s Federal Emergency Management Agency released $1.2 million in Pre-Disaster Mitigation funds to Marseilles for the construction of a floodwall and a pumping station to protect the city’s sewage treatment plant.
At its last meeting, the City Council approved an intergovernmental grant agreement concerning the funds. The city’s matching share will be $400,000.
“That’s the good side of it,” City Engineer Mike Etscheid told The Times. “The bad side is if it costs more the city has to come up with the rest.”
Even so, it’s a great deal and a solid flooding safeguard.
“It’s going to be great protection for the citizens of Marseilles,” said Mayor Jim Hollenbeck. “We’ve had to sandbag down there almost every year.”
Work should commence this year. Some design plans needs to be updated, Etscheid said.
“Maybe by fall we’ll be ready to go,” he said.
The city’s sewage treatment plant dates from 1939. There were major renovations in 1974 and another overhaul completed in 2010.
At that time the specifications for the higher flood wall were drafted, but efforts to get the government funding were unsuccessful until earlier this year.
The existing berm is 480.8 feet, one foot above the base flood elevation — also known as the 100-year flood elevation — of 479.5 feet, and below the 500-year flood elevation of 481.5 feet.
The 2008 flooding of the Illinois River reached 480.77 feet at the Marseilles sewage treatment plant, and in 2013, the river reached 481.15 feet.
During both events, water began topping the berm, and the city’s sandbagging efforts prevented flooding. Sandbags were placed atop the berm, raising its height approximately 12 inches during both the 2008 and 2013 flooding events.
“Without sandbagging efforts, the 2013 event would have resulted in 4 feet of water inundating 70 percent of the sewage treatment plant,” according to a FEMA report. “To restore the facility to use after such damage would cost an estimated $3,015,500.”
A flooded sewer plant also could mean basement messes in city homes.
“In the event that the berm were overtopped, raw, untreated sewage could flow directly into the Illinois River and its surrounding environment,” the FEMA report says. “Residents of the city of Marseilles could experience sewer and basement backups as the gravity-fed system would cause sewage to continue to flow to the plant.”
At one point, as an alternative, Marseilles considered the option of raising the existing levee with an earthen embankment.
“This method would cause fill to extend 20 feet into the Illinois River,” said the FEMA report. “This alternative could have impacts on the Illinois River: impeding flow, causing siltation, degrading habitat and creating erosion issues.”
That option was abandoned.