NRCS Helps Rehab Aging Watershed Dams
If you drove by the watershed dams scattered across North Dakota you probably wouldn’t think that there’s a problem with some of the sturdy looking structures.
They still hold back billions of acre feet of water. They still protect farmland, homes, businesses and roads from flooding. The reservoirs that have formed behind some of the dams still offer fishing, boating, camping and other recreational opportunities.
But many of the dams are now beyond or near their expected 50-year design lifespans.
As earthen dams age, they can weaken. Seepage and cracks are common. Sediment fills in behind the dams, reducing the capacity of the reservoir and increasing the chance that water can run over the top of the dam and cause it to fail. Earthen spillways used to control reservoir levels erode. Concrete, iron and steel used in dams gates, chutes and spillways gates can crumble and rust.
The dams don’t meet the new, more stringent design and construction safety regulations enacted since the dams were built, either. At the same time more homes, agricultural structures, roads and bridges have been built downstream from many of the dams.
The USDA Natural Resources Conservation Service is currently helping rehabilitate seven watershed dams in North Dakota. The dams are classified as “high hazard” dams. A “high hazard” dam is one in which loss of life or significant damage to downstream homes, businesses, farms, roads, bridges and other transportation infrastructure may occur if the dam failed suddenly or were mis-operated.
The dams are:
- Matecjek, Fordville and Bylin Dams on the Forest River in Walsh County, owned by the Walsh County Water Resource District.
- Senator Young, Olson and Bourbanis Dams on the Tongue River in Cavalier County; owned by the Pembina Water Resource District.
- Larimore Dam on the Turtle River in Grand Forks County; owned by the Grand Forks Water Resource District.
“We’re helping the owners bring these dams into compliance with current state and federal performance, design and safety standards,” says Christi Fisher, NRCS state engineer, who heads up the watershed team. NRCS works with several state agencies and private engineering firms to rehabilitate dams.
Six years, $15 million
Rehabilitating a dam is a big job. The full process takes at least six years to complete and costs as much as $15 million.
The work starts with an assessment of a dam’s condition and studies of all the different rehabilitation options. The potential environmental, social and economic impact of all feasible alternatives are considered, including the possibility of decommissioning the dam. Several meetings are held to get input from the public as well as local, state and federal agencies. Once the dam owner decides what to do, NRCS comes up with a design and a construction plan.
NRCS provides 90% of the planning, 100% of the design and 65% of the construction costs. The money comes from the federal Watershed Rehabilitation Program, which Congress created in 2000. The dams’ local sponsors pay 35% of the construction costs. They typically secure grants from the North Dakota State Department of Water Resources and the Red River Joint Water Resource District to help cover their share.
The Watershed Rehabilitation Program is a big help, says Daryl Campbell, chairman of the Walsh County Water Board. “We couldn’t finance the rehabilitation of these dams ourselves.”
Work on North Dakota’s seven high-hazard dams probably won’t be completed at least until 2025. But the results will likely be worth the wait. The Renwick Dam -- a high-hazard dam on the Tongue River that protects the City of Cavalier and the surrounding area downstream -- was rehabilitated in 2014. The 180-acre lake behind the dam is part of Icelandic State Park and is a popular recreation area with camping, boating and a beach with public swimming.
NRCS helped the Pembina Water Resource District raise the height of the dam by five feet; install settlement plates across the new fill material; and replace the unsafe earthen spillway with a roller compacted concrete spillway that is 500-foot wide, 5-feet thick and has 20-foot-tall concrete sidewalls. The new spillway makes it possible to draw down the lake faster and more safely during intense rain or runoff conditions.
“Rehabilitation extended the life of the dam for another 100 years,” wrote Dwain Phillips, National Watershed Coalition media director, in a report upon the completion of the project.
The change in weather patterns has created a big concern for earthen dams and vegetative spillways, says Richard Axvig, chairman of the Grand Forks Water Resource District. which owns and operates the Larimore Dam. He has been a member of the district’s board for 17 years and was with the NRCS for 34 years.
“Dams need to be rehabilitated to function safely in these large summer rains, such as the 20+ inches of rain that occurred west of Larimore, N.D., in 2000,” he says.
Being able to rehabilitate a dam and preserve the flood protection and recreation benefits for future generations is especially rewarding, Fisher says.
“The Watershed Rehabilitation Program is a good example of NRCS ‘Helping People Help the Land’ on a broader scale than typical conservation projects with individual agricultural producers,” Fisher says. “The resulting projects benefit a broad group of individuals, governmental entities, and natural resources.”
For a high resolution file of the image, click here.
for the Natural Resources Conservation Service - North Dakota