Manatee County Commission ratifies $14M dam fix

skennedy@bradenton.comApril 4, 2014 

MANATEE -- The Manatee County Commission ratified a $14 million contract Thursday for an emergency fix to the Lake Manatee Dam.

County utility officials recommended repairing the potentially serious conditions at the dam, according to county documents.

Tests conducted by engineers found "voids beneath the downstream spillway structure" were causing soil erosion.

Test samples identified loose material within the earthen dam's core.

"There's been a significant amount of soil loss in these areas," said Mark Simpson, county water division manager, at a Manatee County Commission meeting.

An investigation into the best way to deal with instability threatening the East Manatee dam has been underway for weeks.

The contract calls for two phases of work.

The first phase to be substantially complete by June 1 calls for reinforcing the dam by mixing soil and a binder of clay/cement to form a homogenous, impermeable water barrier, according to a summary from the Manatee County Utilities Department.

"The priority goal is to re-establish and improve seepage control with a new cutoff wall within the existing dam near the service spillway..." read the summary.

Engineers plan to extend the new cutoff wall near dam abutments as well, it said.

The second phase calls for

work on the downstream side of the dam spillway.

The first clues there might be a serious problem came from recent annual inspections showing anomalies, Simpson told commissioners.

He said it took time for study and testing to gauge the seriousness of the matter.

In February, officials announced the dam may have been compromised by erosion, and slowly brought lake levels down from 40 feet to 38 feet as a precautionary measure.

Since then, utilities staff and its county engineer of record, Carollo Engineers Inc. of Sarasota, along with a consulting firm, AMEC Environmental & Infrastructure Inc. of Tampa, have been developing stabilization plans.

They chose Hayward Baker Inc. of Tampa as their contractor.

"The conclusion from this investigation showed that the core of the dam is compromised, and allows water to seep through and under the dam," the summary said. "Seepage control needs to be re-established and a seepage control structure needs to go much deeper than the original core depth."

Manatee County commissioners Thursday approved three following motions to launch repairs:

1. Declared work on the dam an emergency since they hope to have the job completed before June 1 when the rainy season starts and gushing rainfall might cause a catastrophic failure.

2. Ratified the $14,091,190 repair contract.

3. Adopted a related budget amendment to supply money for the project.

The utilities department's handling of a difficult situation should comfort Manatee County citizens, said County Commissioner John Chappie.

"It's one of the best utility departments in the state and the country," he said.

Commissioner Vanessa Baugh congratulated county staff members, saying they had effectively diagnosed trouble and avoided property damage or worse.

"You've done a great job, and probably saved us from having a very ugly time," she said.

The dam is part of the Manatee County utility system, which provides drinking water for Manatee and some Sarasota County residents through a treatment plant at 7914 Waterline Road. It was completed in 1967, creating the 1,800-acre Lake Manatee reservoir, which stores 7.5 billion gallons of water.

Sara Kennedy, Herald reporter, can be reached at 941-745-7031. Follow her on Twitter @sarawrites.

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