Posted on March 23, 2021
Maj. Gen. William H. Graham, deputy commanding general of civil and emergency operations for the U.S. Army Corps of Engineers, visited the Moose Creek Dam on Feb. 19 while touring the organization’s northernmost flood control project. Col. Kirk Gibbs, USACE Pacific Ocean Division commander, and Col. Damon Delarosa, USACE Alaska District commander, accompanied the general.
Situated in North Pole, Alaska, and named after a nearby waterway, the dam serves as the primary component of the Alaska District’s Chena River Lakes Flood Control Project, which protects Fairbanks from flooding during high-water events. Since going into operation in 1979, it has reduced damages for downstream communities by an estimated $420 million.
To gain greater insight and understanding of this unique project, Graham met with employees who both maintain and operate the dam as well as team members involved with the upcoming improvement project.
“It is important for USACE leadership to get boots on the ground and gain a greater appreciation for the challenges of engineering in the Far North,” Delarosa said. “There is a big difference between reading about something versus coming here, walking the terrain, seeing it with their own eyes and meeting with the people involved. From logistics, to the harsh environment, to higher operating costs, the district’s work in this state is unlike anywhere else in the Corps.”
While at the project, Graham received a briefing on modification plans designed to strengthen and extend the life of four and a half miles of the berm, while continuing to reduce flood risks for many years to come.
“I’m excited about the construction of the Moose Creek Dam Safety Modification Project, so the flood-risk management benefits can be realized by the communities of North Pole and Fairbanks,” said Steve Howard, project manager at the Alaska District.
He anticipates site preparations to take place next fall and winter. Construction activities for the main project upgrades are scheduled to begin in the spring of 2022.
The general also had the opportunity to learn about the district’s plans to fix a groin along the Tanana River that is a part of the Chena Project. These structures are built perpendicular to the shoreline to stabilize the streambank. As a braided river, it is not uncommon for the Tanana to change course. In this case, a shift in streamflow caused the groin to be hit at a 90-degree angle and become damaged.
Reinforcing the structure will help prevent erosion to this section of the flood control project. The placement of additional rock is anticipated next year.
“We are purchasing 6,000 tons of rock and delivering it by the railroad to place on the groin,” said Julie Anderson, chief of operations.
Graham then visited the project’s dam control works, where the operations team can take action to reduce the flood risk to downstream communities.
The Moose Creek Dam uses flood gates to regulate the flow of the Chena River and can store water behind its earth-filled embankment during high-water events. Known as a dry dam, the structure only retains water when necessary to protect downtown Fairbanks from flooding.
“The dam is a diversion dam,” Anderson said. “It diverts the water from the Chena River to the Tanana River to bypass downtown Fairbanks.”
Because the Chena is about one-tenth the size of the Tanana, the river can accommodate the overflow and help prevent an inundation of the city.
The general inspected the interior of the cement-encased control works to see where employees operate the dam in 12-hour shifts to keep streamflow at a safe level. Graham praised the team for maintaining the condition of the structure so well.
As the group stood on top of the control works to take in the view overlooking the floodplain upstream of the dam, temperatures hovered at minus 11 degrees with the Chena River frozen in place as is typical in the winter months. The brief exposure to the cold provided the general with taste of what the project team must contend with on a daily basis throughout the winter.
After the ice melts in the spring, the river runs freely through the dam during the summer months. Once this happens, a team from the district monitors water levels to determine if the dam needs to operate.
“It can happen anytime the river is thawed,” Anderson said. “We have operated the dam 30 times since it was constructed.”
One of the issues the team briefed Graham on is the lack of predictability in flooding at the project. Despite their engineering expertise and readily available technology, the members find it difficult to anticipate when flooding will occur.
Factors such as snowpack, temperature, rainfall and ice all impact the water level in the river.
“Just because there is a lot of snow in the mountains, does not mean a lot of melt off in the spring. Weather conditions, such as the amount of rainfall, also contribute to river levels,” Anderson said. “We plotted it out last year to see if there is a pattern and there isn’t one.”
During the flood season, the team keeps a watchful eye on water levels so that they can respond in a timely manner if they need to operate the dam.
With authorization from Congress after a flood devasted Fairbanks in 1967, the district completed construction of the Chena River Lakes Flood Control Project in 1979. The dam regulates the flow of the Chena River at a level not to exceed 12,000 cubic feet per second through downtown Fairbanks.
The stop at the Chena Project concluded Graham’s site visits to an array of USACE projects planned or under construction within the state.
The previous day, he travelled to the remote village of Elim to tour the area, meet with local officials and discuss recommended modifications to the existing harbor.
The proposed improvements would upgrade navigation, access and moorage for the subsistence and commercial fleet as well as enhance fuel and freight barge services.
“It was great to visit the harbor and engage with community members,” Delarosa said. “Seeing the site in person gives us the opportunity to truly understand the positive impact the harbor modifications can have on the village.”
