On top of the $18 million it cost Manatee County to make emergency repairs in 2014 to prevent the Lake Manatee Dam from failing, it will cost an additional $17 million to complete Phase 2 of the project.
Phase 2 was expected to begin in 2016, but additional investigation into the dam and downstream structures have shown that there are more issues with which to contend. Among those issues are filling in voids under downstream structures that are diverting seepage and addressing seepage around the primary spillway. Some of the scope of work includes replacing the existing approach slab, installing a continuous barrier and making any needed repairs to those underwater structures not seen since the dam was built in 1965.
The news comes on the heels of the county having to use $30 million in reserve funds for Hurricane Irma cleanup. Though the Federal Emergency Management is expected to reimburse most of that, “We don’t know when,” said Commissioner Carol Whitmore. Officials said they were confident the funding will be available, whether it’s within existing reserves or whether the county has to look at incurring debt.
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Part of the challenge is getting to the underwater structures while keeping the 1,800-acre lake servicing more than 300,000 people in Manatee and Sarasota counties. A coffer dam, or barrier, is being proposed to cut off the spillway slab in order to do “dry work,” according to Mark Simpson, water division manager for Manatee County utilities.
The county tried a $4 million coffer dam in 2011 that failed and in 2014 attempted a grout jetting system to stop seepage, but, “That didn’t work as well as we hoped,” Simpson said.
According to the scope of work, some of the work done in 2014 will have to be readdressed and that didn’t sit well with the commissioners at Tuesday’s workshop.
Simpson said the 2014 emergency repairs were, “Something that had to be done quickly. So we went through an emergency procurement process with the understanding that we had some caveats that we needed the lake to remain in service. The challenges were under the spillway itself and our engineers as well as the contractors all had a good understanding that the surest way to make sure all that seepage was taken care was to do it in the dry, or drain the lake and rebuild the dam. That was not an option for us under those circumstances.”
Under this plan, the project should be able to get to the slab and other underwater structures by drying out the project area without having to take the lake out of service. But the commission wants guarantees that it’s going to work. Simpson wasn’t sure they would get them, but Mitchell Palmer, county attorney, said the county would need some type of warranty or the contractor won’t get the job.
Commission Chairwoman Betsy Benac said the reserve fund is what this kind of situation is for and otherwise, “How do you budget for a 50-year-old dam?”
Benac pointed out that other counties just now beginning to construct dams for drinking water reservoirs are paying many more millions of dollars than this will ultimately cost Manatee County, “But we still want to make sure it’s done right.”
Simpson said once the approvals are in place, the project could be completed by late 2019 and informed the commission that his team will be bringing forward a series of needed approvals over the course of the next eight months.