On Monday, Nov. 27, the Bureau of Reclamation started the process of draining water from the Colorado-Big Thompson Project (C-BT) tunnels and reservoirs in preparation for safety inspections and maintenance work.
The temporary drawdown reduced levels in Lake Estes from its typical level of 7,472 feet in elevation. The reduced levels also affect Marys Lake.
“Every five years, an upper C-BT water conveyance inspection must be completed,” said Ronnie Rogers, Power Plant Supervisor for the Estes Park and Marys Lake power plants. “Engineers come down from Montana and Denver to evaluate and inspect concrete every five years. They check to make sure the condition of the pipes is up to standard.”
In addition to the inspections, seal replacements will be performed on the radial gate on Olympus Dam
According to Rogers, the process to prepare the system and reduce the water levels so inspectors can safely walk the tunnels takes about a week. Starting with shutting off West Portal in Grand Lake, the water starts to drain down eastward. Water is drained from the Alva B. Adams Tunnel and Marys Lake, through Prospect Mountain Tunnel and from Lake Estes. The water is diverted to the 8-mile pipe between Crocker Ranch and Pole Hill Gatehouse.
“The process completed this morning [Dec. 4],” said Rogers. “People will be in the tunnels this week doing inspections while crews work on the gate on the dam. Next week, inspections will take place from Pole Hill to Flatiron [Reservoir].”
The work is anticipated to be completed by Dec. 14, with refilling taking a couple of days.
The 250-mile C-BT Project is one of the largest and most complex natural resource developments undertaken by the Bureau of Reclamation. C-BT stores, regulates and diverts water from the Colorado River west of the Continental Divide to provide supplemental irrigation water for 615,000 acres east of the Rocky Mountains. It supplements the municipal and industrial water supply and provides recreation for more than 1 million residents in Northeastern Colorado. It also produces enough electricity to power nearly 68,000 households.
Built between 1940 and 1944, the 13.1-mile Alva B. Adams Tunnel is the largest water diversion project in Colorado, moving water from Grand Lake under the Continental Divide in Rocky Mountain National Park and into East Portal. The water then travels to Marys Lake, Lake Estes and other reservoirs along the system.
Lake Estes, which was formed after completion of Olympus Dam, was dedicated in 1949.
If you are interested in learning more about the C-BT, visit .
