Engineers define Lake Manatee Dam repairs

EAST COUNTY — Engineers consulted to determine potential repairs to the Lake Manatee Dam reaffirmed what Manatee County staff already knew: any fix can be completed prior to the rainy season.

In a Feb. 28 memo to the Manatee County Board of County Commissioners, Mike Gore, county utilities director, said engineers will make a final recommendation on repairs to the dam late this week, after the East County Observer went to press.

“We are confident that this matter is well under control and mobilization and work will have commenced by April, and the most crucial measures completed by June 1,” Gore wrote to commissioners. 

An annual inspection conducted by a private consultant determined the core of the dam, which provides drinking water to more than 300,000 residents in Manatee and Sarasota counties, may be compromised due to erosion. 

During a review of notes from the inspection of the dam, Bruce MacLeod, superintendent of Manatee County’s Lake Manatee Water Treatment Plant, noticed the report revealed irregularities near the dam’s spillway gate.

The report indicated there are spaces in a few areas in the dam’s clay core, which stops water from leaking downstream.

If the core becomes compromised, it could prevent the structure from regulating the amount of water that flows through the dam with the worst-case scenario resulting in the flooding of 18 homes located downstream from the dam’s location on Waterline Road.

The report said a four- or five-day rainfall could compromise parts of the dam, risking its collapse and heightening the urgency to complete the repairs before the rainy season begins.

Engineers confirmed the issue is more related to the natural aging of the 48-year-old dam than any specific cause.

MacLeod said construction methods used today are much different than 50 years ago.

“We followed what were standard operating procedures at the time,” MacLeod said. “In fact, the engineers said we were one of the first to use soil and cement in construction of a dam.

“For a dam of this service length, ours is probably in the shape it should be in,” he said. “Technology is quite a bit better now. We are confident this fix may extend the life of the dam beyond 50 years.”

During the last few weeks, engineers have conducted coring techniques — accessing the core of the dam by drilling into different areas of the core and lowering cameras into the holes, to capture pictures of the soil below the surface. 

The photographs will reveal whether the soil protecting the core on the upstream side of the dam is loose — and how large of a fix is required.

In the memo to the board, Gore, suggested several repair methods are being considered, including jet grouting — a process that uses “jets” of water to cut away earth and uses pipes to inject grout into holes.

“But additional methods exist that may be more conducive and economical to our specific situation,” Gore wrote. 

MacLeod said the county is already talking with a construction company about the nature and cost of potential fixes.

MacLeod has said costs could be in the $3 million to $6 million range.

After staff receives the engineers’ final recommendation on fixes, it must approve them.

The Board of County Commissioners would then have to approve the repairs.

Officials hope to start any necessary repairs by April.

Contact Josh Siegel at [email protected].