As unique as they come: Big Piney Weir Project at Fort Leonard Wood

U.S. Army Corps of Engineers, Kansas City District
Published April 26, 2023
A rock outcrop sits in the Big Piney River.

The Big Piney Weir sits in the Big Piney River to aid in the supply of water for the Fort Leonard Wood, Missouri, installation.

A rock stream flowing.

The aquatic organism passage was added to the design to allow passage of aquatic species through the year up and around the weir at Fort Leonard Wood, Missouri. It is also being used to temporarily reroute water during construction.

A rock outcrop sits in a river as water flows through the middle of it.

The Big Piney Weir sits in the Big Piney River at Fort Leonard Wood, Missouri.

A piece of heavy machinery sits on a rock outcrop in a river.

A drill rig sits on the Big Piney Weir in the Big Piney River to take borings of the weir for an ongoing construction project at Fort Leonard Wood, Missouri.

Rock samples sit in a box.

Rock borings from the Big Piney Weir construction project sit in a box at Fort Leonard Wood, Missouri.

What do hellbenders, water supply and construction all have in common? It’s the Piney Weir Project at Fort Leonard Wood, Missouri!

The $5.8 million project in the woods of Fort Leonard Wood will repair a roughly 80-year-old weir in the Big Piney River. A weir is a low dam built across a river to raise water levels upstream. At Fort Leonard Wood, the weir does just that, but serves a special purpose to the military community living and working on the installation.

“The purpose of the weir [is] to pond water for the [installation’s] water intake for water supply. It is the main water supply for Fort Leonard Wood,” said Angela Loewen, civil engineer and team lead for the project.

According to Loewen, the weir has been repaired multiple times since its construction in the early 1940s, but it has been deteriorating over time due to weather events and high river flows. Fort Leonard Wood requested the U.S. Army Corps of Engineers, Kansas City District complete this project to lengthen the lifespan of the weir and continue to provide local water to the installation.

A river of challenges

“Anytime you are working in a river with water and mother nature, there are going to be challenges,” said Eric Omundson, Military Programs section chief.

Working with water means the project is subject to issues with weather, river conditions and other unique factors.

“Our construction timeline is constricted for endangered species [concerns] … as well as the fluctuation of the river and the low rainfall period of the year. There is only a certain period of time that we can work in the river,” said Casey Bolich, Fort Leonard Wood Resident Office project manager.

The weir is home to the Eastern Hellbender, an aquatic salamander that is on the endangered species list. All work pertaining to the hellbender must be coordinated through multiple fish and wildlife, and natural resource agencies. This kind of work takes time and careful planning.

Aside from the weather and wildlife, the team has experienced multiple challenges throughout their planning and design process, like a lack in historical documentation from the original project plans or having the weir located near a historical outlook site that needs to be protected. For each unique hurdle they encountered, they found a unique solution.

For example, to work on the weir, they need to dewater the area around the weir, but can’t stop the flow of the river. Dewatering means that all the water around the weir will need to be removed and the weir must be dry. To overcome this challenge, the team designed an innovative solution.

“Follow-on aquatic organism passage features were added to the design … to allow passage of aquatic organisms throughout the year up and around the weir structure,” Bolich said. “The contractor is currently using it as a bypass to reroute the river for the repair of the weir.”

They also had to think outside the box to survey the area during the planning process due to the steep banks and rough terrain around the weir.

“[We had] to ramp down from the west side [bank]. [It is] the only kind of access point we have to the weir,” said Loewen.

Once they had access, they were able to survey and get a drill rig out on the weir to collect borings.

“Taking a drill rig out on to the top of a weir that is deteriorating was rather challenging … [but] we were able to get a couple of borings through one side of the weir,” said Loewen.

Those borings helped the team determine the composition of the weir and aided in their design process.

The team also held public meetings and forums before advertising the project to discuss concerns with the public. These meetings helped the team ensure the weir project was environmentally sound and the best option moving forward.

Due to how unique this project was, they needed to find a contractor who had the very niche capabilities needed to overcome the challenges.

“How the team overcame that challenge, was we conducted the appropriate market research, we engaged with industry and [participated] in industry days in order to solicit feedback from industry and to generate interest in the project,” said Omundson.

The contract was awarded to McMillan Jacob Associates in September 2022. Construction of the weir has begun, so the immediate area is fenced off and closed to the public due to safety concerns. This means all recreation on and around the weir is closed, including fishing.

There will be no impact to the current water intake operations throughout the duration of the project. The project is scheduled to be completed in fall 2023.