Innovation leads to productive season for safety upgrade at Moose Creek Dam – Alaska Native News

Innovation leads to productive season for safety upgrade at Moose Creek Dam - Alaska Native News

JOINT BASE ELMENDORF-RICHARDSON – Dipping temperatures and the aurora borealis streaking across the night sky signaled the end of the second construction season for the Moose Creek Dam Safety Modification Project on Oct. 12 at the Chena River Lakes Flood Control Project near North Pole, Alaska.

With the onset of winter, the U.S. Army Corps of Engineers – Alaska District capped off a successful summer by doubling its progress from last year to build a cement barrier wall in the center of the dam. The safety improvement project is now about halfway complete as the team works to reinforce 4.7 miles of the 8-mile-long earthen structure.

A new construction method is credited for the increase in productivity after the team modified its approach to contend with the dam’s unique soil composition.

“The contractor made a series of refinements to the soil-mixing technique and dramatically increased production while maintaining good quality,” said Matt Folk, resident engineer and administrative contracting officer for the project. “This method being utilized at Moose Creek Dam is a first for USACE for barrier or cutoff wall construction.”

The new technique is innovative for the contractor installing the $153 million barrier wall as well. The Bauer Foundation Corp. of Florida is accustomed to using the soil-mixing process in large rectangular footprints for reinforcing structures, but a series of successive cylindrical columns will create the wall for this project instead. The method, known as “single-column mixing,” is typically employed to create pilings, Folk said.

Essentially, the mix-in-place procedure consists of boring into the earth with an auger to loosen the soil, while simultaneously injecting a binding agent. For Moose Creek Dam, the wall material is made of cement and bentonite that is produced on-site to alleviate the cost and logistics of trucking pre-mixed material from another location. In some portions of the project, the reinforcement structure will reach depths of up to 65 feet.

“The hard, dense sand and gravel soils in the dam embankment have been the biggest challenge for the entire project,” Folk said. “The refinements to the mixing technique have been successful in addressing the difficult conditions.”

During the 2023 summer season, the team constructed about 1.56 miles of mix-in-place concrete barrier to bring the current total progress to about 2.28 miles of completed wall. The project is scheduled to finish by January 2026, but it could be done sooner if the latest production trend continues on the remaining 2.43 miles of fortification.

The improvement project was needed after a USACE modification study conducted in 2017 recommended the establishment of a reinforced dam embankment to extend the life of the aging infrastructure. The safety upgrade will enhance the dam’s strength and stability to provide the greater Fairbanks area with continued flood protection for many years to come. While construction is underway, the dam will continue to operate and regulate the flow of the Chena River during high-water events as needed.

“It is a construction project that you cannot see the progress if you are just driving by,” said Daniel Powell, project engineer. “However, it will be extremely important to the community once it is complete.”

Historically, the dam was built after one of Alaska’s worst disasters struck the Fairbanks area. In the summer of 1967, unusually heavy rains swelled the Chena and Little Chena rivers to 6 feet above flood stage, causing more than $80 million in damages and displacing nearly 7,000 people.

In response, USACE began work on the Chena River Lakes Flood Control Project in 1973 and it was completed in 1979. Today, major components of the project include Moose Creek Dam and a floodway as well as the Tanana River Levee and drainage channels. Together, these features comprise the largest federal civil works project in the state.

As a partner agency, the Fairbanks North Star Borough’s Parks and Recreation Department operates the Chena Lakes Recreation Area on the property. It consists of a no-alcohol park with restrooms, campsites, picnic area, playground, volleyball court, swim beach, non-motorized boat launch, natural area and trail system.

While construction has been underway, a strong partnership between USACE, Fairbanks North Star Borough and the contractor proved to be vital to achieving a safe and successful season. Weekly meetings between the three entities allowed for effective communication to resolve issues and address potential conflicts related to public access.

“USACE having an ‘open door’ for suggestions and concerns that were voiced regarding pedestrian safety while the project is in progress has been very helpful,” said Trisha Levasseur, project coordinator for the Fairbanks North Star Borough’s Parks and Recreation Department. “They have been great partners to help us navigate this type of project taking place in a very popular recreation area.”

The three organizations are striving to minimize impacts on local recreators. However, closures may be necessary to ensure public safety around the construction area.

“The project may look interesting to view at a closer distance, but we really ask the public to respect the construction zone as it is adjacent to the recreation area,” Levasseur said.

Once the modification project is complete, full public access will be restored so people can continue to enjoy the area’s diverse outdoor opportunities. More importantly, those living downstream of the dam will benefit from a significant structural upgrade designed to provide the community with long-term flood protection.

In the meantime, USACE has ceased its construction efforts for the upcoming winter months and will begin work again in the spring. Until then, the lull is a perfect time for visitors to stop by to engage in a recreational activity or view of the northern lights.