Dam Design and Construction

Hydro Review: Holter Dam’s Century of Excellence

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Hydro Review: Holter Dam’s Century of Excellence

Holter Dam was inducted into the Hydro Hall of Fame thanks to its long life of performing with high reliability. Successful construction of this dam, on the Missouri River in Montana, required a decade and two different owners.

By Jo Dee Black

Holter Dam and the associated 48-MW powerhouse — located on the Missouri River 43 miles northeast of Helena, Mt., in Lewis and Clark County — took a decade and two different owners to complete. Despite challenges and setbacks, the vision of early backers of the dam who saw the role that affordable, abundant electricity would play in the region’s economic development proved true.

Completed in 1918, the Holter Dam facility remains largely unchanged, but it continues to perform with high reliability. While auxiliary systems have been progressively upgraded during the past century, the original infrastructure and design remains.

The electricity produced at Holter is used to supply more than 21,000 residential and commercial electric customers in Montana with clean, affordable and reliable energy.

Due to the reliability and efficiency of the project, Holter Dam was inducted into the Hydro Hall of Fame at HydroVision International 2019. This article will dive into the history behind Holter Dam, its advancements, as well as its significance today.

Historical background

Anton Holter, after whom the dam was named, came to the U.S. from Norway in 1854, when he was only 23. He started by selling lumber to mining operations and became known as the “father of the lumber business” in Montana, with lumber yards in Virginia City, Nevada City, Helena, Great Falls, Sun River and Fort Benton.

Holter partnered with entrepreneur and former territorial governor Samuel Hauser in several business enterprises, the construction of Holter Dam being one. Originally known as the Wolf Creek Project, Holter Dam was on the drawing board during the construction of Hauser Dam, which was another ongoing project at the time, the next dam upstream from Holter Dam on the Missouri River, about 20 miles away.

Hauser Dam is now a six-unit hydroelectric plant with a total capacity of 19 MW. The original dam was a steel structure completed in February 1907, and it failed in April 1908. After this failure, Hauser launched an ambitious plan to both rebuild Hauser Dam and construct another dam at Wolf Creek, simultaneously. Hauser Dam was immediately rebuilt as a concrete structure and has operated reliably since it was finished in 1911.

Although Hauser’s goals in building the Wolf Creek Project are not readily apparent, in general, the state was developing hydropower in large part to support copper mining and smelting in the Butte/Anaconda area. The copper industry was booming because the U.S. was in the process of “electrification” and needed copper wire everywhere.

The construction camp at Holter consisted of more than 115 structures, including: a bunkhouse, dormitories, cottages, a dining hall, bath house, school, hospital and photography studio.

However, the Wolf Creek Project faltered due to cost over-runs and false optimism regarding the construction timeline. The initial work that began in 1909 was halted after financial backers feared bankruptcy. Only a portion of the dam’s concrete foundation had been poured when work ended.

The stalled Wolf Creek Project and Hauser Dam, started by the United Missouri River Power Co., became part of the fledging Montana Power Co. in the following years. John D. Ryan, an Amalgamated Copper executive, played a big role in the formation of MPC in 1912 and supported these projects throughout the years.

Developmental process

Work on Holter Dam resumed in March 1916. A year later, about 490 workers were on the job. Consequently, the construction camp at Holter was the largest built by MPC and included more than 115 structures, such as a bunkhouse, dormitories, cottages, a dining hall, bath house, school, hospital and photography studio. The first turbine-generator unit was operational by 1917, joined by three others in 1918.

The finished dam was 1,350 feet long and more than 110 feet high. It was the tallest dam on the Missouri River at the time. Original construction of the facility included fish passage, which was a very innovative advancement. The construction of Holter also marked the sixth dam, and hydro powerhouse, completed by MPC and its predecessor companies Marathon Oil and Ashland Inc. within a decade.

MPC owned Holter Dam until 1999, when all the company’s generation facilities in Montana were sold to PPL Montana, a deregulated merchant utility company focused on the open power market. Finally, NorthWestern Energy bought the PPL Montana hydro facilities in November 2014.

Holter Dam today

The dam is a straight, concrete gravity structure with a roadway across the top and an ogee spillway section. There are 31 spill bays equipped with gates or flashboards.

The powerhouse is a mass concrete substructure with concrete and structural steel superstructures. It contains four 12-MW turbine-generator units that generate at 6,600 volts, four 20,000-kVA transformers that set the voltage to 100,000 volts and a 75-ton-capacity traveling crane.

The plant routinely exceeds 95% equivalent availability and operates at an average of 75% capacity factor. The original design and construction have proven very reliable through the years.

The 27-mile-long reservoir is called Holter Lake and impounds 240,000 acre-feet of water. Upper Holter Lake has a surface area of slightly over one square mile. At the downstream end of Upper Holter Lake, the reservoir enters a steep, picturesque canyon call Gates of the Mountains. Holter Lake is a known recreation destination for anglers, both for open water and ice fishing and motorized and non-motorized watercraft. As a result, the development along Holter Lake is primarily recreational.

The Missouri River, downstream from Holter Dam, is nationally renowned for its trout fishery.

Holter Lake’s fish population includes rainbow trout, kokanee salmon, walleye, northern pike and yellow perch. The Missouri River, below Holter Dam, is a blue-ribbon tailwater fishery that is nationally recognized for its great trout fishing. According to an angler pressure survey completed by Montana Fish, Wildlife and Parks in 2017, over 170,000 days of recreational angler fishing is recorded annually in the river below Holter Dam.

Holter Lake also has both camping and daily use sites: Holter Lake, Log Gulch and Departure Point Recreation sites. This land holds 140 camping units; 25 day-use units; three designated swimming areas; two multi-lane boat ramps; and paved/graveled entrance roads.

Both Holter Lake and the Missouri River downstream are included in the Missouri-Madison River Fund Grant Program. This program is implemented through the Missouri-Madison Comprehensive Recreation Plan, which addresses ongoing needs for public recreation in the Missouri-Madison Project (P-2188) Area. The project consists of nine developments on the Madison and Missouri Rivers in southwestern Montana and develops hydropower along a 324-mile stretch of the two rivers. Holter Lake is located on the Missouri River, downstream from the U.S. Department of Interior’s Bureau of Reclamation’s Canyon Ferry Hydroelectric Project.

A public-private partnership was created among contributors of P-2188 , the Missouri-Madison River Fund Grant and NorthWestern Energy, as matching funds are awarded annually for qualifying projects.

Since the first round of project awards for FY2007, the River Fund has provided more than $4.5 million in grant funding for public recreation. Since 2014, NorthWestern Energy has provided nearly $1.2 million in matching funds. These funds, along with agency and partner contributions, have resulted in more than $9 million in public recreation enhancements in the Missouri-Madison corridor.

In 2018, the River Fund financed the Holter Lake management plan, a $133,000 project that also included $20,000 in funding from NorthWestern Energy. This management plan is a 10 year plan to manage recreation and access facilities, done by the Bureau of Land Management and U.S. Forest Service. The plan helps them forecast how and what they need to support recreation at Holter Reservoir.

Achievements and recognitions

Employees at Holter Dam were honored by the Occupational Health and Safety Administration for their workplace safety efforts in December 2016.

The hydroelectric facility was recognized with reapproval as a Star Facility in OSHA’s Voluntary Protection Program (VPP). This program recognizes work sites that demonstrate exemplary safety performance, going beyond compliance with safety regulations. Such approvals can occur every five years and are attained through the completion of a rigorous multi-day audit by a team of OSHA VPP representatives.

The VPP process promotes a safety partnership between management, workers and OSHA. The program also encourages shared ownership of safety and health responsibilities. In addition to promoting safer workplaces, VPP can help reduce off-the-job injuries and illnesses. Holter is one of four NorthWestern Energy hydroelectric operations in Montana to earn the VPP Star certification, and only 10 work sites in Montana have earned the honor.

Celebrating 100 years

At the 2018 centennial celebration of Holter Dam, Jeremy Clotfelter, NorthWestern Energy’s Director, Hydro Operations, told Independent Record’s Tom Kuglin: “For me, one of the coolest things about what we do is the privilege to work on facilities and plants that have been here for a century. We have several in the state that are at this age or older, and that’s why we’re here today, to celebrate the great longevity and the value that Holter has brought to our customers and communities in the state for 100 years. How many other industries or careers or jobs out there can actually stake that claim?”

This generator is just one piece of Holter’s original equipment that remains in service today.

Recently, NorthWestern Energy hired Dome Technology to rehabilitate 21 of the spillway’s bays. After 100 years of operation, repairs of the concrete surfaces of the bridge structure were overdue. And the company is currently preparing a request for proposals for both turbine and generator upgrades, to occur over the next several years.

Jo Dee Black is specialist, public relations with NorthWestern Energy.

Note: The Hydro Hall of Fame award is presented annually to historic, legacy hydroelectric facilities worldwide that have generated electrically continuously for 100 years or more. The 2020 inductees to the Hydro Hall of Fame will be unveiled during the opening keynote session at HYDROVISION International 2020, July 14 in Minneapolis, Minn., U.S.