Less than a week after torrential rains inundated businesses and residences along North Main Street, Ottawa City commissioners learned about the work behind the scenes as county and city employees responded to the high-water emergency.
Franklin County Emergency Management Director Alan Radcliffe and Ottawa Public Works Director Michael Haeffele spoke with city officials during a Monday afternoon work session at city hall.
Thursday’s rainstorm, Radcliffe said, was much worse than even meteorologists forecasted the day before.
“What we received was twice what was predicted,” he said. “By 6:30 a.m., 8.5 inches of rain was recorded at the water plant.”
The rain event lasted 12 hours, but the moisture blamed for flash flooding fell between midnight - 6 a.m. Thursday, Radcliffe said.
Downpours earlier that morning caused runoff into area streams and rivers, which were already full because of required releases at Melvern and Pomona lakes. With so much rain this summer, many of the state’s reservoirs, which are managed by the Corps of Engineers, have been forced to release water to keep their flood pools from being at capacity. In late-May, Pomona and Melvern lakes were both at a record 82 percent of capacity.
So when Thursday’s storm hit, water was already being released at 3,000 cubic feet per second,Radcliffe said. It was 7:30 a.m. before those releases stopped.
“Rain came down Eight-Mile Creek from Lone Star in Douglas County to Centropolis and into the (Marais des Cygnes) river west of Ottawa,” he said. “By 1 a.m., the water was at 13 feet. Between 7 a.m. and 8 a.m., the river rose to 24 feet.”
Eventually, the river crested at 35 feet Thursday afternoon.
City officials close the Main Street flood gates when the Marais des Cygnes River reaches 33 feet. So far this year, the gates have been closed three times.
As the rains worsened, Haeffele said city public works employees responded. One employee arrived around 10:30 p.m. Wednesday, he said, adding two more arrived around midnight. Haeffele said he arrived a few hours later.
“Every time the river comes up, I hear the rumor that the city did not close the outlets,” Ottawa Mayor Blake Jorgensen said.
“That is absolutely false,” Haeffele said.
Ottawa’s levee system, according to the Corps of Engineers, includes two drainage structures, one pumping plant, two rolling gate closure gaps, a floodwall toe drain, a concrete floodwall and 1.21 miles of earthen levee along the Marais des Cygnes River and Wilson Creek.
Haeffele said the levee pumps were activated and performed as designed. Between the city’s pumps and those borrowed from the Corps of Engineers and other entities, officials said the city had at least 15 working throughout the community.
Radcliffe told commissioners the flood was a rare occurrence.
“With the flash-flooding event we had, you’re looking at a 500- to a 1,000-year event,” Radcliffe said.
The Corps of Engineers defines a 500-year-flood as meaning a flooding event of that size or greater has a one in 500 chance of occurring in a given year.
Commissioners like Eric Crowley also asked Haeffele questions during the work session, hoping to squash other rumors surfacing during the flood. Crowley questioned if the lift station on the north side of Ottawa, near the levee, was capable of eliminating standing storm water. Haeffele told him it wasn’t.
“OK. So it being off because the transformer had been damaged - was a generator brought in to run that?” Crowley said.
“Yes,” Haeffele said. “So that has nothing to do with the getting rid of any storm water?” he said.
“No,” Haeffele said. “I just wanted that out there because it’s another one of the rumors I heard is that the pump wasn’t working,” Crowley said.
“We’re talking about two completely different systems,” Haeffele said. Unlike pumps designed to remove storm water, a lift station is used for pumping wastewater or sewage from a lower to higher elevation.
Radcliffe told commissioners eight to 10 homes were affected in Ottawa, including those on the east side of town along Skunk Run Creek between Second and Third streets and Poplar.
While floodwaters forced city officials to close the intersection at Main and Keokuk streets until Monday afternoon,
Haeffele said it would take at least a month for the traffic signals there to be repaired. Commissioners were told it would take 30 days to receive the parts and have them installed. Until then, the traffic signals will display flashing red lights in all four directions.