Safety Measure - Annual inspections conducted to ensure Barnett Reservoir dam stays safe
Reservoir officials are getting ready to conduct their annual dam inspection. Every year, reservoir officials hire a registered state engineer to conduct the inspection.
From performance to leakage, erosion and equipment operation, the inspection ensures the dam is operating at peak levels.
For the past six years, Burns Cooley Dennis Inc. has handled the task.
“We’ve procured services from Burns Cooley Dennis Inc.,” said John Sigman, Pearl River Valley Water Supply District (PRVWSD) general manager. “They do great work and have a great reputation to do the annual inspection… When we reviewed them for this work, they had dam inspection experience.”
Along with approving the bid proposal from Burns Cooley Dennis for this year’s summer inspection, reservoir officials have also accepted the engineering firm’s report for the 2016 inspection.
“Every year we come up with another proposal for the cost. Right now we’re approving the 2016 report and the proposal to do the 2017 dam inspection,” said Sigman.
Both items were scheduled to be approved during the March 13 meeting.
“Work includes inspecting all facets of the dam. They look at how it’s performing, the amount of leakage and erosion, how the equipment’s operating. They look at reports in terms of flow of water under the dam, just making sure there aren’t any changes.”
“We’ve been doing it from day one every year,” he said.
The cost of the inspection can run anywhere from $40,000 to $50,000, depending on if officials ask the firm to perform any extra work or tasks.
“We vary the time of year (for the inspection),” said Sigman. “In 2016, it was done in the winter months. This year it’ll be done during the summer.” Changing conditions such as rainfall, ground saturation, lake level and vegetation coverage dictate when the work needs to be performed.
“You can see more when vegetation coverage is down, but you also want to see if there are any problems when vegetation is present,” Sigman said.
A major component of the summer inspection is ensuring animals haven’t burrowed and disturbed the integrity of the dam’s structure.
“Burrowing animals are more active in the summer,” said Sigman. “So, we might see more activity in the summer than in the winter.”
Along with the yearly inspection by Burns Cooley Dennis Inc., reservoir officials conduct weekly inspections.
“They’re owner inspections,” said Greg Burgess, reservoir chief engineer. “Then there’s also the requirement that we do an annual, third-party inspection with a registered Mississippi engineer.”
Often, the yearly inspection takes about a week, and then months to put the data and information together.
“The engineering firm goes through past inspections and notes to get ready on their end. I’m not sure how much time it takes, but there’s obviously prep time,” said Burgess. “They spend a couple of days on site, and a couple of months later we get the compiled information.”
Burgess said the engineers also look at the control tower, documents, emergency plans “and things of that nature” to put together their findings.
“We give a copy of that to the state as well,” he said.
The entire inspection is almost strictly visual. Inspectors walk around the dam and on the catwalk above the dam to get an up-close look at it.
“If you see where grass and dirt is moving away, like on the side of the road, that’s how surface water carries off dirt. (We look at) ponding areas like in your yard, where there’s a low spot with water. That’s seepage with water coming up in certain areas.”
Burgess said eroded areas are refilled with dirt, just like in one’s yard or property. Sigman said the firm also runs a survey to ensure the dam hasn’t shifted by running levelers across it.
“We go through where we keep records of discharge, they can go through that,” Burgess said.
To test the leakage under the dam, Sigman said engineers inspect the water gauges.
“There’s no access channel (under the dam),” he said. “They do observe the gauges to make sure they’re in good shape and make sure there’s not any inordinate leaks through the gates.”
Burgess will also perform an interior dam inspection with the hired dam inspectors.
“We’ll drive a boat very slowly around on the water side as close to the gate as possible,” he said. “We have to avoid the pulling factor, but we ride the whole face around the spillway.”
The dam has 10 gates. One gate raised four inches lets out 400 cubic feet per second, the normal amount of discharge into the Pearl River.
Water levels at the reservoir are normal at 22 feet deep, or 297.5 feet above sea level.
The minimum discharge for the dam into the river is 240 cubic feet of water.
The reservoir dam has 10 gates to control flow of water