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Wolf Creek, Montana
Holter Dam Spillway Concrete Repair
NorthWestern Energy hired Morrison-Maierle to help with the Holter Dam’s spillway concrete repair. Holter Dam is a 1,364-foot-long and 124-foot-high concrete embankment dam on the Missouri River near Wolf Creek, Montana. NorthWestern Energy owns and operates the facility as a part of its Montana Integrated Hydro system.
Completed in 1918, the Holter Dam has provided electricity for more than a century, and it supplies electricity to more than 300,000 residential and commercial customers in Montana.
After 100 years of severe weather exposure, extreme temperatures, freeze-thaw exposure, and wind, waves, and spray from Holter Lake, the concrete spillway bays were in dire need of rehabilitation.
Client
NorthWestern Energy
Location
Wolf Creek, Montana
Budget
$1.2M
Awards
2019 Intermountain Chapter American Concrete Institute Excellence in Concrete Award
The former concrete was severely worn and had deteriorated significantly.
A contractor applies shotcrete downstream of the spillway.
Shotcrete was applied as a way to remediate the deteriorating Holter Dam.
Services and Highlights
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Concrete inspection
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Concrete repair
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Construction inspection
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Shotcrete specification
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Spillway rehabilitation
A Modern Approach to an Old Problem
Morrison-Maierle worked with the owner, Northwestern Energy, to develop a unique approach to the project that addressed the various challenges with access, safety, and efficiency.
The traditional approach would have required building scaffolding in each of the 21 bays, concrete forms, reinforcing, and various concrete products for use in the varying thicknesses of the repair areas. To mitigate the time, expense, and safety risk of the traditional approach, Morrison-Maierle developed detailed repair plans that used shotcrete for all repair areas.
Using this material instead of traditional cast-in-place concrete, the contractor was able to utilize faster and more efficient means of placement, including a bridge snooper truck for most of the shotcrete installation.
In the end, the project was completed within budget and on time, which benefitted all parties. Like many dam projects, Holter Dam does not have an anticipated end of life. Instead, projects like concrete repair continue to extend the life of the structure, add value, and enhance dam safety.
Shotcrete repair on the downstream side of the spillway.
Shotcrete repair on the upstream side of the spillway.
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