The Indian Trail Improvement District Board of Supervisors heard an update Wednesday on plans to upgrade the levee separating the J.W. Corbett Wildlife Management Area from The Acreage.
At the board’s previous meeting, residents raised concerns about reduced seepage through the new levee, which they felt might affect their wells.
Funding for the project was recommended by Gov. Rick Scott and approved by the state legislature after flooding from Tropical Storm Isaac nearly breached the levee, which would have caused larger flooding problems in The Acreage.
John Mitnik, bureau chief of engineering and construction for the South Florida Water Management District, said his agency has completed the design for phases 1 and 2 of the project, although only phase 1 is financed currently with $4 million approved by the state legislature. The total cost of the project will be about $7.8 million.
Phase 1 is the western mile and a half of the total 2.5-mile-long project just north of the M-O Canal.
Mitnik said his staff is finalizing the necessary procurements before moving into the award of a contract and actual construction later this year. He said the western portion of the levee was identified as being of greater concern to the overall integrity of the existing berm.
After going through several different design iterations that the SFWMD shared with residents for input over the past year, they arrived at a design for an earthen levee just north of the existing berm.
He explained that the existing berm, which is about a one-to-one slope, will be pulled back from the M-O Canal to a new levee to the north with a three-to-one slope.
“The levee at the top width will be about 14 feet so you can drive on it and get access,” Mitnik said.
On the northern side in Corbett, they will be able to maintain a higher water level to preserve the wildlife habitat while keeping residents of The Acreage dry, he said.
At the previous meeting, during which the board granted an easement, residents raised concerns about reduced seepage that might affect their wells.
Mitnik said the concern arose out of a report the SFWMD submitted to the Department of Environmental Protection during the permitting process.
“I’ll be honest with you, I probably would have reworded that sentence to more accurately reflect what it is we’re really talking about,” he said.
Mitnik explained that all earthen berms will have seepage.
“It’s an engineering fact of life that once you have water stacked up higher on one side of a pile of dirt than it is on the other, you’re going to have water want to move through that pile of dirt,” he said.
Mitnik said the seepage becomes an issue when the water starts moving through the berm more rapidly through the soil and causes sloughing, where the dirt starts moving with the water.
“When you go out to the berm today, you can actually see areas where the soil has sloughed off and fallen to the bottom of the canal,” he said. “That’s what you’re looking to prevent. That’s what you’re looking to mend. It’s through that mechanism that levees fail.”
He said the new levee with a three-to-one slope will give it more stability. “The seepage is still moving through the area, still moving toward the canal, but we’re managing it such that it has a much longer flow path to go through,” Mitnik explained.
