Mount Prospect is defending its response to last week's flood in the face of criticism from Des Plaines about the placement of a temporary wall near Levee 37.
Mount Prospect Village Manager Michael Janonis told the village board's committee of the whole Tuesday night the village will meet with the Army Corps of Engineers and the Illinois Department of Natural Resources "to figure out if there are any adjustments that might be made" for the future.
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Meanwhile, Mount Prospect Mayor Irvana Wilks said that at the state's request, she has sent a letter to the Illinois Department of Natural Resources. The city of Des Plaines issued a news release Friday charging that actions by Mount Prospect and Prospect Heights had a negative impact on the city's flooding.
In the letter to IDNR's Arlan R. Juhl, Wilks said the construction of a temporary barrier wall on April 18 at the Levee 37 gap "had no negative impact on flood elevations downstream of the levee (Levee 37)."
Levee 37 has been built since the last major Des Plaines River flooding a few years ago. The barrier wall filled in a gap in the levee that was to remain until more storage capacity was created upstream at Heritage Park in Wheeling. That storage is currently under construction.
Wilks wrote that the village was forced by circumstances to change its normal strategy of constructing a barrier wall along River Road because the existing pumps at Levee 37 and additional pumps added later would not prevent water from overwhelming surrounding neighborhoods "adding an additional 3 feet of flooding depth to this neighborhood."
The village maintains that the amount of water displaced by the temporary barrier was negligible and amply compensated for by diverting it to the Heritage Park construction site.
Wilks added, "It should be noted that extraordinary circumstances warranted the change in our flood fight strategy."
For one thing, on April 17, the forecast abruptly changed, when the estimate for the crest at the Des Plaines River gauge in Des Plaines went from 6.1 feet to a record-setting 11.2 feet.
Public Works Director Sean Dorsey explained the village's strategy to trustees.
Dorsey said that the village traditionally has fought floods by placing a temporary barrier at the center of River Road. Dorsey said that before Levee 37 was built, the River Road storm sewer system would drain into the Des Plaines River and not affect the village's storm sewer. Now the storm sewer system drains into the Levee 37 pump station, which is the same pump station serving the northeast third of the village. Consequently, he said, "If we were to flood fight in the middle of River Road … that water would just pour into our storm sewer system."
That would have overwhelmed the pumping station and threatened hundreds of homes in the area bounded by Rand, River, Kensington and Seminole, sometimes called Newtown because it was annexed in 1972 after it was already built.
A barrier in the middle of River Road also would have left the village unable to access the pump station and the pumps, which would be underwater, he said.
"We made the decision that the only place to flood fight on that day was in the gap (of the Levee 37 wall)," he said. "The idea that we were going to sacrifice the Newtown subdivision to stormwater was never a viable option."
Another concern, Dorsey said, was how well the Levee 37 pumping station would work.
"We have concerns based on the performance during that storm that the pumping stations might not be adequate," he said after the meeting. "They weren't able to dewater the storm sewer system at a sufficient rate to keep the sewers from surcharging, to keep streets from flooding, to keep homes from flooding."
Dorsey said the village added four six-inch pumps it has had for years as backup. When that still proved insufficient, the village added two more six-inch pumps and two 12-inch pumps, the "double twelves," as he called them.
"That appeared to do the trick," he said.