Power Generation

Colorado-Big Thompson Project power plants generate an average of 760 million kilowatt hours of renewable energy per year. The C-BT Project’s West Slope pump plants annually use 70 million kilowatt hours. The remaining 690 million kilowatt hours are sold to customers in Colorado, Eastern Wyoming and Western Nebraska.

Power is generated by water flowing through C-BT Project power plant turbines to produce hydroelectricity. The power sold to customers is enough to supply approximately 67,000 homes for a year. The Western Area Power Administration markets and distributes the C-BT Project power.

The C-BT Project has six power plants. Five are located on the East Slope between Rocky Mountain National Park and the mouth of the Big Thompson Canyon. Green Mountain Power Plant is located on the Blue River near Kremmling on the West Slope.

Power for the Pump Plant at Lake GranbyWhen the C-BT Project was planned in the 1930s, the East Slope and Green Mountain power plants were designed to provide power to the Willow Creek and Farr (previously Granby) pump plants due to a lack of sufficient power plants and electrical infrastructure on the West Slope when the project was built.

The Willow Creek and Farr Pump plants receive electricity from the East Slope power plants via a 69Kv transmission line extending through the Adams Tunnel. Today, even with adequate West Slope electrical infrastructure and power production, the Adams Tunnel transmission line still provides the West Slope pump plants with a portion of their electrical needs.

Plants Respond to Peak Power Needs
The East Slope hydroelectric plants also supply power for peak demands by using a system of forebays, afterbays and penstocks (large-diameter above-ground pipelines).

When peak electrical power is needed, such as early-evening hours, water is moved from a plant’s forebay (a small reservoir above a hydroelectric power plant) into a penstock leading to the power plant.

The force of the water moving through the penstock and turbine generates electricity. After the water passes through the turbine, it is typically released into the afterbay (a small reservoir located below a hydroelectric power plant).
C-BT Power Plant Profile Map
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Water Descends 2,900 Vertical FeetWater flows beneath Rocky Mountain National Park via the Adams Tunnel to the East Slope and descends the Front Range mountains nearly 2,900 vertical feet through these five power plants and three reservoirs: 
  • Mary’s Lake Power Plant and Mary’s Lake southwest of Estes Park
  • Estes Power Plant and Lake Estes east of downtown Estes Park
  • Pole Hill Power Plant and Pinewood Reservoir west of Loveland
  • Flatiron Power Plant and Flatiron Reservoir southwest of Loveland
  • Big Thompson Power Plant on the Big Thompson River west of Loveland
Green Mountain Power Plant
The Green Mountain Power Plant is located at the base of Green Mountain Dam at Green Mountain Reservoir on the Blue River southeast of Kremmling. The plant has a 25.8 megawatt capacity and was the first power unit of the C-BT Project to produce electricity. It began power production in May 1943.