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Delve into the history of the Boulder Canyon Hydroelectric Facility

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Delve into the history of the Boulder Canyon Hydroelectric Facility
(photo courtesy City of Boulder)

By City of Boulder

The 5 MW Boulder Canyon Hydroelectric Facility is a hydropower plant owned and operated by the City of Boulder in the U.S. state of Colorado. Once a central component of hydropower production in the Rocky Mountains, the hydro plant is now a part of the city’s municipal water supply system.

Boulder Canyon was a 2022 inductee into the Hydro Hall of Fame. Read on to learn the important history of this hydroelectric project and how the City of Boulder is upgrading, maintaining and operating it for the future.

Hydro Hall of Fame

History of its development

The Boulder Canyon Hydroelectric Facility is a component of the Boulder Canyon Hydroelectric Project (BCH Project), which includes two reservoirs, two pipelines and the hydro plant. The hydro plant generates electricity using water diverted from Barker Reservoir on Middle Boulder Creek near the town of Nederland. Water from this reservoir is transported 11.7 miles in the Barker Gravity Pipeline to a small regulating reservoir, Kossler Reservoir, and then through the Boulder Canyon Penstock to the hydro plant. The hydro plant sits 1,821 feet lower than Kossler Reservoir and experiences about 800 pounds per square inch of pressure.

The BCH Project was initially built and operated by a series of power companies solely for power production. However, starting in the 1950s, the power company allocated a portion of the volumetric capacity in Barker Reservoir and its associated pipelines to the City of Boulder for municipal use. In 2001, the City of Boulder purchased the BCH Project, including the hydro plant, from the power company. Since that time, the project has operated primarily as a municipal water supply while also generating power when there is excess capacity in the system.

The BCH Project’s rich history dates to the early 1900s, when it was conceived as part of an ambitious entrepreneurial plan to bring electricity to a growing Colorado. That plan envisioned a network of hydro plants and power lines in the Rocky Mountains, but only two of the plants materialized – Shoshone, on the Colorado River near Glenwood Springs, and Boulder Canyon. Upon completion in 1910, the BCH Project featured the highest pressure recorded at a hydroelectric plant at that time and was noted for its unique engineering features, construction challenges and resulting innovative building techniques.

Construction of the BCH Project began in earnest in 1908. Each component of the project involved difficulties, beginning with Barker Reservoir, which required condemnation of land owned by Hannah Barker, who refused to sell her ranch holdings. The next component, moving downstream, is an 11.7-mile-long concrete gravity pipeline that delivers water to Kossler Reservoir. The pipeline crosses a landscape of steep, rugged hillsides, sheer rock faces, heavily forested areas and meadows. Few roads existed at the time of construction, and supplies and materials were hauled to work areas with great difficulty. Pipe sections were fabricated at work camps along the canyon and were generally short, about 2 feet long, to navigate the rugged terrain. In some areas, tunnels and inverted siphons had to be built to accommodate the natural landscape.

The penstock from Kossler Reservoir was built against a steep hillside and initially constructed from steel pipe sections joined by 2-inch-thick rivets, but this was not enough to seal the joints against the tremendous water pressure in the penstock. Engineers determined a new method of joining pipe sections was needed. A welder skilled in the emerging process of acetylene welding was brought in to secure the rivets and joints with an acetylene weld, but the welds cracked when they cooled. After experimentation, crews discovered that hitting the rivets with a ball peen hammer while still hot from welding prevented cracking and stopped the leaks. In 1994, the Boulder Canyon Penstock was awarded the Historical Welded Structure Award by the American Welding Society in recognition of it being the first structure to use acetylene welding in conjunction with the ball-peen welding procedure and for significantly advancing penstock technology when constructed in 1910.

The final component of the BCH Project, the hydro plant, experienced its own construction challenges. The site for the plant was located along a twisted path in Boulder Canyon, more than a mile from the nearest rail stop at the town of Orodell. Equipment and building materials were delivered via narrow-gauge cars to Orodell, where they were transferred to horse-drawn wagons for the last leg of the journey. As many as 16 horses were required to pull the wagons carrying the heaviest equipment, such as the turbines and generators.

The hydro plant began generating power on Aug. 4, 1910, using two I.P. Morris Waterwheels connected to two General Electric generators, each with a capacity of 5 MW. When completed, the Boulder Canyon Hydroelectric Facility was seen as the most advanced of its type in the nation and was visited by engineers and power company representatives from across the country and featured in technical journals and magazines.

Enhancing project operations

The Boulder Canyon Hydroelectric Facility was modified and updated over the course of the 20th century. This included replacement of the Unit A turbine with a larger Pelton wheel and installation of new generators and other equipment in the mid-1930s, which doubled the capacity of each unit; completion of a new transformer yard and transmission lines by the late 1940s; and replacement of the Unit B turbine in 1959. One of the two generators at the plant had to be rebuilt in 1964 after an operating mishap caused so much vibration that the generator broke its mounting bolts and lifted itself out of its pit, causing substantial damage.

Through the 1940s, the BCH Project was operated solely for power production. In the 1950s, through a partnership between the power company (Public Service Company) and the City of Boulder, the BCH Project began delivering water to the City of Boulder to meet growing municipal water supply demands. Between 1955 and 1999, the City of Boulder acquired municipal water rights for storage in Barker Reservoir and developed agreements with Public Service Company to secure increasing amounts of municipal storage capacity in the reservoir for treatment at the city’s nearby Betasso Water Treatment Plant.

In 2001, the City of Boulder purchased the entire BCH Project from Xcel Energy (formerly Public Service Company) for $12.4 million. Full ownership increased the reliability and flexibility of the city’s municipal water supply by providing additional reservoir storage space, higher municipal water yields and the ability to do much-needed repair and improvement to the system to address operational and water treatment issues.

Shortly before the city purchased the BCH Project, the plant’s Unit A generator failed and the remaining operational 10 MW turbine and generator were at the end of their expected lives. Because the city prioritized use of the system for its municipal water supply, the functioning turbine and generator were operating outside of their optimal flow range. The hydro plant was in great need of upgrades, as well as resizing, to support Boulder’s operational goals. In 2005, the City of Boulder completed a feasibility study to integrate municipal water supply reliability and hydropower generation. The study showed that a 4.9 MW hydro turbine-generator unit would be an appropriately sized replacement and could allow annual generation to increase because of increased turbine efficiency with proper sizing and decreased operational issues.

In 2010, the City of Boulder was awarded $1.18 million in federal funds by the U.S. Department of Energy toward a total estimated project cost of $5.16 million to replace and modernize the Boulder Canyon Hydroelectric Facility. This funding allowed the city to move forward with plant modifications that would ensure the plant continued to operate. 

The modernization project was completed in 2012 and resulted in improved efficiency and safety. The average annual generation with the old 10 MW turbine/generator unit had been about 8,500 MWh, whereas annual generation with the new turbine/generator averages 11,000 to 14,000 MWh, representing a 30% to 65% increase. The old unit was a single nozzle Pelton turbine with a 5-to-1 flow turndown and a maximum turbine/generator efficiency of 81.8% but with actual efficiencies in the range of 40% to 70% due to age and non-optimal capacity of the turbine for the available water flow. The new turbine is a double nozzle Pelton turbine with a 10-to-1 flow turndown that operates in the range of 70% to 88% efficiency through a large portion of the existing flow range. The modernization project also upgraded deteriorating wiring, improved lightning protection and installed a remotely operated turbine isolation valve.

Modernization of the plant was designed to reduce negative environmental impacts by reusing the existing facilities without operational changes. Concrete, cast iron, steel and copper removed from the plant were recycled, and recycling revenues helped offset project cost. Additionally, two transformers that posed an oil spill risk near Boulder Creek were removed. Wherever possible, the city preserved equipment in place for educational and display purposes, including the 1936 turbine. Today, plant visitors can view historic and modern hydroelectric technology side by side. 

The City of Boulder’s decades-long partnership with the power company and eventual acquisition of the BCH Project showcases the multiple and mutual benefits derived from hydroelectric facilities. While the BCH Project is primarily operated for a municipal water supply, excess capacity in the system is used to generate power, which is sold by the city to local electric utilities. Hydropower provides a renewable source of energy that supports electric utilities’ renewable energy commitment. Revenue from the sale of hydroelectricity from this and seven other municipal hydroelectric facilities offsets a portion of the capital and operating costs of Boulder’s water utility, which would otherwise have to be paid by Boulder’s water customers through higher water rates. The hydro plant also enables the city to further its climate action goals by incorporating renewable energy production into its operation and by utilizing a water supply that operates with relatively low energy requirements due to the elevation difference between the water source, the water treatment plant and the water customers.

The City of Boulder is proud of the history of the Boulder Canyon Hydroelectric Project and its integration into the municipal water supply system. It is a part of the city’s heritage and an important part of ensuring future water and energy resilience for the Boulder community.

Editor’s Note: If you’d like to view this historic facility in person, Boulder Canyon is included in one of three technical tours scheduled for HYDROVISION International 2024 in Denver, Colo., U.S., this July. And join us for the opening keynote at HYDROVISION, where the 2024 Hydro Hall of Fame inductees will be announced.