Closeup of Obermeyer Gate Rendering

Thurlow gate replacement to begin soon

By Michael Butler

Thurlow Dam is as iconic as the Benjamin Fitzpatrick Bridge in Tallassee. The wall of concrete and wood that creates the reservoir known as Lake Talisi will be undergoing a facelift soon.

Alabama Power Company will begin the process of replacing the 36-gate flashboard system that has been in place for decades. A meeting is scheduled for Wednesday in Birmingham to finalize construction plans for the project with work expected to start in June.

"A lot of times when the flashboards go down and the lake drops five feet, the flashboards should stand back up," Thurlow Dam Superintendent Joel Johnson said. "When they don't, our men have to go out on a barge and hook a crane to them and pull them up.

"We started looking at some newer technology and came up with the Obermeyer Gate System, which is a steel gate system. Now you can control the angle of the gate. Not only can you control the flow over the spillway, you can get ahead of the floods and do a much better job with reservoir management."

Rendering of Replacement Obermeyer Gate System

In addition to changing from wood to steel, the 36-gates will become four spans instead.

"The difference is a lot of those concrete piers will come out. Now you have 36 individual gates. The first span is only going to be about 45 feet long. Span two will be 342 feet. Spans three and four will be 380 feet each. Each span will operate independently of the other spans," said Johnson. "When we did make the decision to go with this newer technology, we had meetings with the Alabama Historical Commission and University of Alabama doing research on Thurlow Dam. We tried our best to make it look like it does now."

The "Niagara of the South" scene when the gates are down creates quite the spectacle and according to Johnson will not go away.

"What you'll see is a more controlled spillway, but I think you'll see all spans down. I've been at Thurlow a little over seven years and I've not seen them all down. I've seen probably 26 of the 36 (gates) down."

Thurlow as it appears today

Thurlow Dam is an arched spillway that was constructed by Alabama Power Company in 1928 and an historic landmark in Tallassee.

Rendering of trash boom to be used for picking up debris

"There was an old masonry dam that was there when the mill was running," Johnson added. "When the power company came in, they poured concrete over the top of it. If you'll look when you go across the bridge, you'll see these concrete openings in the spillway. That's actually where we go in every three months and do an internal inspection of the dam.

"The only thing that will change will be the type of the spillway. A lot of the concrete abutments between the gates will come out. What you'll end up with is an abutment at each end. You'll have three intermediate piers. Right now you have about 25. We wanted to do our best to mimic what we have as far as color in trying to make it look the same but incorporate the new technology."

Alabama Power operates 14 hydroelectric plants in the state.

"This one is unique. It sits underneath a bridge. We have very few of these," Johnson added. "If you think about the technology back in '28, they didn't have computers. That's a lot of good engineering back in those days."

As most might guess, the project will cost millions of dollars.

View of flashboard gate section with overflowing waters

"I don't have the exact dollar right now. That's above my pay grade. It's going to be a multi-million dollar project. We had to spend quite a bit just to get through the engineering. That's the most important part. We've spent over a year just engineering this to make sure we get it right the first time."

Hydro Review Magazine cited that an Obermeyer gate system for an 860-foot dam on the Colorado River cost $25.4 million for replacement gates. Once work is underway in Tallassee, local residents can expect water levels to be down on Lake Talisi for a good portion of the next two summers.

"It's going to be good for the city of Tallassee. I know the folks in Tallassee on the river, they're not real happy with me right now because I'm going to lower the lake in the summertime when they like to have recreation. I understand that. I like the lake myself.

"The reason we're doing it in the summertime is we had reservoir management do a study on when we have the most floods. Our rainy season is from November to May. It's very difficult to get all this equipment mobilized and try to do it in the wintertime. The summertime is when we get the least rain. We can do a better job of controlling the reservoir level and get the work done efficiently."

The official dedication ceremony of Thurlow Dam in 1939 included an unveiling of a tablet honoring the namesake, Oscar Thurlow, by his daughter Elisabeth Thurlow (above right). Photos courtesy of Tallassee Community Library.

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