Lake Manatee Dam is 'severely distressed,' at risk for collapse with large rainfall

Lake Manatee Dam is 'severely distressed,' at risk for collapse with large rainfall

jdeleon@bradenton.comFebruary 15, 2014 

MANATEE -- The Lake Manatee Dam is in a "severely distressed state" because of erosion, engineering consultants have found, forcing county officials to take "corrective actions."

Heavy rains over four or five days "could compromise parts" of the Lake Manatee Dam, Manatee County government warned in a news release Friday afternoon.

"Lake Manatee Dam is in a severely distressed state," wrote engineers with Carollo Engineers Inc. and AMEC Environment & Infrastructure Inc. in an assessment for the county. "Without immediate intervention there is a high risk of an uncontrolled release of reservoir, most likely following a large rainfall event and opening of spillway."

Officials held a news conference

late Friday afternoon. They said they had begun to advise nearby residents of the problem.

"Without intervention, a significant rainfall event could compromise the dam," Manatee County Commissioner Larry Bustle said. "While there is no cause for immediate alarm, we wanted to waste no time in notifying the public of the measure being taken."

The National Weather Service forecast calls for a 20 percent chance of precipitation Saturday in Manatee, with no more rain predicted for the early part of next week.

Manatee County Water Treatment Plant Superintendent Bruce MacLeod explained what engineers found during a supplemental dam inspection, which the county began doing a couple years ago when they found anomalies during the annual inspection, he said. Water under the dam would rise during high releases, typically following large rain events or storms.

"That in itself is not the problem, once that water starts to go down it pulls soils from behind the dam and underneath the spillway," MacLeod said. "That's what's happening, and slowly it works its way back to the dam."

Now engineers and officials are concerned that the dam's clay core may have been compromised.

"The good news is, there is a relatively quick fix to this, and we are in the dry season," MacLeod said. "We are going to look into the core and see where the compromised soil could be."

Engineers, working through the weekend, will continue to investigate for the next five to seven days.

"Once we identify the critical areas we can inject concrete down in there," MacLeod said.

Projections for work to be completed on the critical area is 30 to 45 days, with all the work being done in 60 to 70 days, he said.

As a precaution, workers have begun to lower the water level of the lake to bring it down to 38 feet instead of its capacity of 40.

Many residents said late Friday afternoon that they hadn't heard news of any problems with the dam.

Chris Lesser lives only 1,000 feet from the dam and said he hadn't heard anything.

"It's somewhat concerning to me that there is something wrong with the dam," Lesser said.

Still not receiving Manatee County's emergency alerts, Lesser said he now intended to sign-up.

Bill Sexton said he hadn't heard a word either from officials.

"They did the last time when one of the gates got jammed," Sexton said. "They called and then they came door to door."

In the 11 years since Sexton has lived on Hagle Park Road, he said it has flooded two to three times.

"The highest it got was two to three inches," Sexton said. "I think with this new bridge (Rye Bridge) here, it would trap a lot of it."

His neighbor down the road, Jessica White, was very concerned that she had not heard any news yet after being evacuated last time there was an issue at the dam.

"We were told by county officials that the ground here was so low that if the dam were to malfunction, the water would reach the top of my roof," White said.

Since purchasing her home in 2002, White said officials have come door to door multiple times when tropical storms and hurricanes threatened the area.

"We are close enough that when they open and close the dam, we can hear the sirens," White said.

Repairing the dam -- which also would extend its life by another 50 years -- could cost $3 million to $6 million, officials said. The dam is near the end of its service life, and replacing it could cost a minimum of $35 million.

County officials said they do have enough in emergency reserves to cover the cost of the repairs.

The 50-year-old dam is the primary source of raw water for the Manatee County Utility System. The lake's watershed covers 82,240 acres, and its total storage volume is 7.5 billion gallons.

Ground for the dam was broken in October 1963, and construction was completed in December 1967.

Deputy County Administrator Karen Windon assured residents during the press conference.

"There is no crisis at this time," Windon said. "We just wanted to get out to the public what is going on in our community and let everyone know what the situation is."

Windon also encouraged residents in Manatee County to sign up for the county's emergency alert system in the event the situation were to become severe.

Anyone interested in receiving emergency alerts from Manatee County should go to www.mymanatee.org/alerts.

Jessica De Leon, Herald reporter, can be reached at 941-745-7049. You can follow her on Twitter @JDeLeon1012.

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