Third Dam headed for a summer finish

Work on Third Dam project along the Logan River continues this summer. The ground on the south side of the rive is being stabilized to ensure the safety of the structure.

LOGAN – Mark Montgomery, general manager of Logan City Light and Power, said the Logan River Third Dam reconstruction has taken more time than they originally thought it would. The repairs include replacing the surge tank, sluice gate spillway, gatehouse and other necessary improvements.

Steel workers tie the re bar in the new gatehouse Monday to prepare ti for the concrete walls.

The Logan River Trail will be inaccessible to the public in the area around Third Dam until the reconstruction is complete.

“When we got to the foundation, it wasn’t what we thought it was going to be,” he said. “The design was based on assumptions of what we would find. Things had to be changed to match the existing structure. We had to tear it out and start over.”

Originally, the plan was to have the dam operational by last spring, now he’s certain the dam will be operational by June or July.

“It is an active project,” he said. “We have to work with several government agencies. The U.S. Forest service owns the dirt, Utah Department of Transportation owns the road next to it, and the Federal Energy Regulatory Commission oversees the project.”

The Army Corps of Engineers, Utah Dam Safety, U.S. Fish and Wildlife, Utah Division of Wildlife Resources, Utah Division of Water Resources and the State Historical Preservation Office all are involved in the making sure the project meets their approval.

“Right now, we are stabilizing the soil on the south side of the project,” he said. “They are drilling down and injecting non-permeable fill into the holes.”

John Miner of Lehi is a supervisor over the ground stabilization process on the south side of the dam along the Logan River,

When they tested the soil they found it was not very stable.

He said they have more science than they used to when they first built the dam.

“The old guys over 100 years ago didn’t have the scrutiny we have today,” Montgomery said. “When we dug into the dam, we ran into some issues.”

The issues are the reason the project is still not done. The old gate house was torn down and they are building a slightly bigger building made of concrete.

“The old gates were made out of wood boards and were kind of dangerous,” he said. “The new gates will be controlled by a bladder that uses air, similar to the one (Utah State University) built at First Dam.”

The project also includes removing the silt and sediment backed up behind the dam and refurbishing the turbines if they can.

The Logan River flows over Third Dam while crews are working on the gate house Monday.

“The hydroelectric generators are kind of historical relics,” said Montgomery. “The original structure was built in the early 1900’s. I think it was upgraded to its current state around 1920 and hasn’t had anything done to it since then.”

Stantec, an international engineering firm working on the dam, has a photo taken around 1904 of some men standing on the dam. From the picture, it seems the dam was built with rock boulders covered with concrete.

Gerber Construction, out of Salt Lake, is doing the actual construction. The Logan office of JUB Engineers is also involved in the Third Dam renovation.

Third Dam is a diversion dam that takes water from the river and pushes it into a 72-inch pipe that feeds water to the turbines at the second dam’s generating plant.

Logan City Light and Power derives its electricity from many sources. Along with two hydro turbines on the Logan River, they also have a natural gas turbine and a solar farm. The city also buys power form several outside sources.

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