Dam Design and Construction

Wissota Hydro provides colorful history and long-running clean energy resource

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Wissota Hydro provides colorful history and long-running clean energy resource
Wissota Hydro Project in Wisconsin (photo courtesy Xcel Energy)

Xcel Energy’s Wissota Hydro Project was a historic and important development when it was completed in 1917 and today is a vital contributor to the company’s goal of delivering 100% carbon-free electricity by 2050. Read the history of this 2021 Hydro Hall of Fame inductee.

By Dean Steines

The Wissota Hydro Project in Wisconsin has been an important contributor to the regional economy since it was completed in 1917. This historic facility set many records in the industry, such as being the “second largest hydro project in the U.S.,” forming the second largest artificial water body in the state, and featuring the longest and highest-voltage transmission line.

Wissota is a 2021 inductee into the Hydro Hall of Fame. Typically these awards are presented during the opening keynote session of HYDROVISION International, but as that event was unable to be held in 2021 due to COVID-19, the awards were officially presented during a HYDRO+ virtual session on March 15. Click here to view a recording of the session.

The hydroelectric project has operated reliably for more than 100 years and forms an integral part of Xcel Energy’s future generation mix.

Hydro Hall of Fame

Setting the stage

In the 1997 movie Titanic, Leonardo DiCaprio’s character Jack Dawson, a young artist and traveler, claims he grew up in Chippewa Falls, Wisc., in the U.S. He even mentions that he went ice fishing on the frozen waters of Lake Wissota as a boy. This would have been impossible, as the RMS Titanic sank in 1912, three years before construction on the Wissota Hydro Project, which formed Lake Wissota, even began. Great movie, but two thumbs down on historical accuracy.

The Wissota Hydro Project is located on the Chippewa River near Chippewa Falls, about 100 miles east of Minneapolis. The Chippewa River begins in northwestern Wisconsin, flowing south 183 miles to its confluence with the Mississippi River, with a watershed encompassing more than 5,500 square miles upstream of the Wissota project. European explorers traveled the river as early as 1680, including Father Louis Hennepin, who called it the “River of Wild Bulls” because of the roaming bison he encountered.

The river served as a transportation route for fur traders, settlers and Native Americans in the 18th and 19th centuries. The logging boom in the 19th century led to the development of small dams along the river to aid in transporting logs. The dams created holding ponds, which allowed the lumber companies to control the number and timing of logs released downstream. Several dams, including one constructed in 1871 near the site of the current Wissota Hydro Project, were built by the Chippewa Valley Electric Railway and Light Company, which was owned by local lumbermen. After the decline of the lumber industry around 1900, developers looked to the river’s hydropower potential.

Wisconsin-Minnesota Power and Light Company

In 1905, Chippewa Valley Electric Railway and Light Company began planning several hydroelectric developments on the Chippewa and Red Cedar rivers. They determined that development on the Chippewa River would be cost prohibitive and thus did not proceed with it.

In 1914, the American Public Utilities Company, owned by Charles Kelsey and Joseph Brewer, purchased the Chippewa Valley Electric Railway and Light Company and changed its name to Wisconsin-Minnesota Power and Light Company. In 1915, the company began planning hydroelectric developments on the Chippewa River, the largest being the Wissota Project. Wissota derived its name from the new company combining Wisconsin and Minnesota.

The anticipated generation from this site, more than 30 MW, far exceeded the demand from the Wisconsin-Minnesota Power and Light system, so an agreement was signed with Consumers Power Company (renamed Northern States Power Company of Minnesota in 1917) for firm power plus specified minimum quantities of surplus energy on demand. An agreement reached in May 2017 resulted in all power generated at Wissota being sold to Northern States Power Company.

The construction cost for the Wissota site was $6.5 million, far exceeding the $2 million estimate. The cost overrun was due to initial estimates being based on depressed wage rates, which rose dramatically by the time construction started. Expected annual production was 140 million kWh, but low water years from 1919 to 1922 limited production to 49 million kWh to 77 million kWh. The higher construction cost and low production led to financial troubles for Wisconsin-Minnesota Power and Light. In 1923, Northern States Power Company purchased Wisconsin-Minnesota Power and Light and renamed it Northern States Power Company Wisconsin. Both Northern States Power Wisconsin and Northern States Power Company of Minnesota are now part of Xcel Energy.

Housing and serving workers

Recognizing construction would require a large force of about 700 workers, the company planned and constructed two villages to house and serve workers and their families. The villages were established on the Chippewa River’s north and south banks near the construction site, with company personnel in one camp and construction contractor personnel in another. A critical component to the villages was a water and wastewater system. Fresh local spring water was pumped to every building. Wastewater discharged into the river downstream of the project site. Buildings were heated with steam.

Living quarters included a modern house for the construction superintendent. Bungalows housed engineers and construction foremen along with their families. Laborers lived in bunk houses, or separate houses if they had a family. Meals were cooked and served at a central dining facility that could seat 350 people. Each building included a lavatory with hot water and electricity. Employees were required to bathe and launder weekly.

Other services were available to the workers and families in the village as well. Health care included a resident physician, a hospital with six beds and a pharmacy. The company also employed a teacher and constructed a schoolhouse. Facilities for leisure and recreation, such as movies and billiards, were also provided. The village had a tobacco shop, but liquor was prohibited.

The Wissota Hospital served residents of the two villages that housed workers and their families (photo courtesy Xcel Energy).

Designing the project

Wisconsin-Minnesota Power and Light hired L.G. Arnold as the project engineer. The company considered several sites for the project and ultimately settled on a location just downstream of the 1871 logging dam site. The selected site took advantage of several smaller upstream rapids to allow a single dam with a head of 57 feet, a 6,400-acre impoundment and the potential to provide a capacity of more than 30 MW.

An exploration program was undertaken to assess site suitability for what was a massive project at the time. Thirty-two holes were cored in the foundation rock and samples were retrieved for testing. More than 2,000 feet of coring and water testing were conducted on the granitic bedrock to detect seams and faults in the foundation.

The layout took advantage of the site’s geography and geology. High bluffs abut each end of the structures, which span nearly 4,300 feet across the river valley. The river channel splits at one location, separated by an island. The powerhouse was constructed in the deeper south channel downstream of a rapids and adjacent to an existing railroad. The deeper channel maximizes the head and also allowed better construction access for the railroad.

The spillway is on a rock plateau about 1,000 feet north of the river. Placing the spillway on the plateau 37 feet higher than the river channel allowed for a smaller, more economical structure with a lower hydraulic drop than would be required at the north channel. A large but less expensive earth embankment dam traverses the north channel.

Construction

Construction of the project structures began in November 1915 and was completed in only 18 months. Wisconsin-Minnesota Power and Light hired a professional photographer to document the construction with more than 500 photographs. The photographs show the effort, workmanship and way of life in the early 1900s.

Initial construction focused on infrastructure to get supplies and equipment to the site.  Highways and railroads were rerouted and six bridges were reconstructed. A railroad spur provided the means to transport the materials and equipment needed for construction to the project site. Towers, hoists and cableways were erected on the banks to move tools, steel, concrete and other construction material from the river bank to their destination at the structures. Boiler houses, sheds and machine shops supported the construction. A concrete mixing plant was established on the south bank near the powerhouse and south concrete dam locations. Several railroads, roads and bridges had to be relocated and constructed to accommodate the reservoir created by the project structures.

The powerhouse, spillway and concrete dams are slab and buttress structures founded on competent granite. The spillway includes 13 steel crest gates, each measuring 64 feet wide and 10 feet high. The total concrete used for construction was 90,000 cubic yards. Openings were included in the powerhouse to allow for streamflow diversion when the concrete structures were completed and earth embankments were being constructed.

The earth embankments include reinforced concrete core walls constructed on the rock foundation. About 70,000 cubic yards of material needed to be excavated for the core walls. Railroad trestles were constructed along the embankment alignment. Rail cars carried earth fill from the borrow site to the embankments, where it was dumped in place. There are three primary and two detached embankments with a maximum height of 67 feet and total length of about 3,400 feet. More than 1 million cubic yards of fill were needed for the embankments.

The concrete core wall for the earth embankment north of the spillway section (photo courtesy Xcel Energy).

Delivery of the energy generated at Wissota required construction of a 100-mile-long transmission line to Minneapolis, including a 70-mile-long tangent section across western Wisconsin to the Minnesota border. Construction progressed at about 1 mile per day. It was the longest and highest-voltage transmission line in the country at the time, at 111,000 V.

Construction of the 36 MW Wissota hydro project was completed in 1917, with the first unit placed in operation on Feb. 12. The six turbines are vertical Francis runners. The Allis Chalmers generators had a capacity of 6 MW each at 13,200 volts.

Workers setting the rotor for the No. 3 generator in place (photo courtesy Xcel Energy).

Unique features

The Wissota spillway gates are self-operating Stauwerke gates. The design originated in Switzerland and had a good performance record in cold climates. Each gate consists of a steel panel hinged at the bottom where it attaches to the spillway. A strut supports the upper portion of the gate. Within the hollow slab and buttress section are massive concrete counterweights. The struts pass through holes in the spillway slab and connect to a balance beam attached to buttresses. Rising water causes the struts to push on the balance beam, rotate on a pin and lift the counterweights. The gates will open partially with a six-inch surcharge and open fully with an 18-inch surcharge. Wissota was the world’s largest self-operating spillway when it was constructed and has the only remaining Stauwerke gates in the U.S.

The Stauwerke gates are being built at Wissota (photo courtesy Xcel Energy).

When constructed, Wissota was “the second largest hydro project in the U.S.” Historical documents indicate Wissota had the largest embankment dam in North America at the time of construction. However, the documents do not specify the basis for this designation. Lake Wissota was the second largest artificial water body in Wisconsin at the time. Wissota became  one of the greatest waterpower developments of the Midwest and one of the steadiest and most reliable sources of electric power on the continent.

Agreements to transmit and sell power to the Twin Cities (Minneapolis and St. Paul) allowed the project to be funded and constructed. None of the power generated at the Wissota Project was used locally until 1935, after the Rural Electrification Administration was established. The REA provided funding to construct the infrastructure to distribute electricity to farms and homes in mostly rural areas. Before this, there was no electrical distribution system in the area.

Economic and recreational asset

Lake Wissota spurred tremendous economic development in the Chippewa Falls area. The area was nicknamed the “Niagara of the Northwest” after the dam was completed. Several resorts opened catering to recreational users on the newly formed lake. By 1930, there were eight summer resorts and seven grocery stores around the lake. By 1940, after Prohibition was lifted, there were 15 taverns on the lake. By 2016, Lake Wissota’s estimated annual economic impact to Chippewa County was $84 million.

Lake Wissota, the “Niagara of the Northwest,” is a valuable recreational asset in the region (photo courtesy Xcel Energy).

In 1961, the state of Wisconsin established Lake Wissota State Park along the north shore of the lake. The park formally opened in 1972 with 990 acres. Since 1972, additional acquisitions increased the park’s size to 1,062 acres. About 100 acres is devoted to trails and campgrounds. The remainder of the park consists of forests and prairie grasslands. The park highlights features formed by glaciers 10,000 years ago and restored farmland to prairie grasslands. The park offers boating, swimming and fishing in the summer and skiing, snowshoeing and ice fishing in the winter.

Modifications

Concrete deterioration of the aging structures required modifications of the slab and buttress dams on both sides of the powerhouse in the late 1980s. Much of the south structure was removed and replaced with an earth embankment. The remaining concrete structure was modified by placing mass concrete between buttresses to form a gravity dam. The north structure was also converted to a gravity structure by adding mass concrete.

Additionally, over the past 10 years, two of the units were upgraded from 6 MW to 8 MW, increasing the total plant capacity to 40 MW.

Replace of one of the turbines at Wissota in 2012, which increased unit capacity by 2 MW (photo courtesy Xcel Energy).

Conclusion

Although the Wissota Hydro Project nearly financially ruined its original developers, it has since provided a century of renewable energy and economic benefit. Wissota Hydro was an impressive achievement in its time as one of the largest dams and hydroelectric plants in the U.S. Much of the original infrastructure remains today as a testament to the project’s design and construction. The average generation over the past 10 years has been almost 161,000 MWh, providing clean and renewable energy as originally constructed.

Today, Xcel Energy is on the lookout for innovative energy technology ideas to help meet the goal of delivering 100% carbon-free electricity by 2050. Yet even an old idea like hydroelectric power still has an impact on energy production. In fact, thanks in part to the power of moving water, Xcel Energy is the No. 1 renewable energy provider in the Wisconsin. The company now runs 19 hydro plants in Wisconsin, as well as one in Minnesota and six in Colorado. Wissota Hydro was a significant early source of energy and after a century of operation remains an integral part of the energy future.

Dean Steines, PE, is principal engineer with Xcel Energy.