The rebuilt Granby Pumping Plant-to-Windy Gap
The rebuilt Granby Pumping Plant-to-Windy Gap transmission line is complete, June 2018. The rebuild replaces two single-circuit lines with one double-circuit line. The view shown is looking northwest in the Idle Glen neighborhood near CR4. (Photo courtesy of WAPA staff)​ See more photos on WAPA's Flickr photo album for the project .



WAPA owns and operates the Granby Pumping Plant-to-Windy Gap Substation transmission line in Grand County, Colorado. The line was originally built as a single line in 1939 to power pumps moving water through the federal Colorado-Big Thompson Project, which includes Lake Granby. Over time, the power from the transmission line has been used to also serve the local community and municipal economy with reliable electricity.

WAPA recently rebuilt the 12 miles of transmission line as a double circuit to increase the reliability of the power system in the local area and ensure continued operation of the Colorado-Big Thompson Project facilities. This project replaced WAPA’s existing 69-kilovolt transmission line and provided a new second 138-kV feed from north of Granby to the pumping plant using some of the existing right of way.

Current status​: (July 2018) All construction has been completed. The 69-kV side of the line went into service in January 2018, and the 138-kV side went into service in May 2018. Some seeding and remediation, such as repairing the right of way and adding access road gates will continue through the end of summer.


The purpose of this project is to:

  • Provide a second source of power to the area between Grand Lake and Granby before failure of the 69-kV cable located in Alva B. Adams water tunnel (also known as the Adams Tunnel Cable)
  • Continue to provide reliable, looped transmission supply to MPEI customers in advance of an Adams Tunnel Cable failure
  • Ensure the electric system in the area will continue to operate within acceptable voltage criteria, while accommodating future load growth in the area and the operation of the Farr and Willow Creek Pumping Plants
  • Allow Tri-State to serve its local member (MPEI) with reliable power
  • Allow WAPA to serve its customers in the area in a reliable manner
  • Replace a 60-year old overhead transmission line and add shield wires for improved lightning protection


The Alva B. Adams Tunnel is a water diversion tunnel that stretches under the Continental Divide between Estes Park and the Town of Grand Lake. It also contains a 69-kV transmission line in the form of an electric cable owned by Bureau of Reclamation and operated by WAPA. This cable currently provides a second source of electrical power to the area from Grand Lake to Granby by allowing looped transmission service between Estes Park and Windy Gap Substations. The Adams Tunnel cable has exceeded its predicted useful life and, upon failure, will not be replaced. The Granby Pumping Plant-Windy Gap Transmission Line Rebuild Project addresses the electrical deficiencies created when the cable fails.

The failure of the cable system will suddenly leave large parts of the Mountain Parks Electric, Inc. (MPEI) system with only a one-way or radial transmission supply. The MPEI system affected by this transmission system includes members in the area extending from the west side of Rocky Mountain National Park on the north, to the YMCA Snow Mountain Ranch on the south, and from Byers Canyon on the west to the Arapaho National Recreation Area/Continental Divide on the east. Included in this area are the Towns of Hot Sulphur Springs, Granby and Grand Lake, as well as hundreds of customers in the rural parts of that area, particularly along the Highway 34 corridor. Without completion of this project, these customers of MPEI would risk extended power outages especially during adverse winter weather due to the lack of an alternate transmission circuit to supply the area.

The project will insure the electric system in the area will continue to operate within established electrical criteria during motor starting operations at Farr Pumping Plant and Willow Creek Pumping Plant. Engineering studies indicated that once the Adams Tunnel Cable is out of service, the voltage drop when starting motors at Willow Creek Pumping Plant will exceed acceptable limits starting in 2010, if load growth in the area continues at the current rate. This impact would affect both NCWCD and MPEI customers being served by these facilities.​


About 12 miles of the current line was rebuilt, with relocation of some structures to minimize visual impacts. There are also some new substation facilities being constructed at both ends of the line and at intermediate line switching facilities. ​

What’s new

  • ​72 steel poles, weighing about 1,000 tons in steel with 7,400 tons of concrete foundation along 12.2 miles.
  • 31 of the steel poles are located within the substation and pumping plant fences or along the existing Windy Gap non-public access roads
  • 41 steel poles are on private or public-managed lands

What was removed

  • 258 wood poles, weighing about 275 tons, along 11.8 mile

Construction schedule

See the maps that show the initial construction schedule.

The general timeline for this project was:

  • December 2016: WAPA construction contract awarded
  • May 2017: Staging of materials and equipment
  • June 2017 to January 2018: Construct line, place 69-kV line in service
  • January to July 2018: Comp​lete substation testing, place 138-kV line in service, complete seeding and remediation  ​


WAPA, in collaboration with US Fish and Wildlife Service, USDA Forest Service Sulphur Ranger District, Bureau of Land Management, Colorado Parks and Wildlife, Mountain Parks Electric and others, completed and published an environmental review of this project in June 2013. A Record of Decision was signed Oct. 1, 2013.

See the Environmental Impact Statement​. A reference copy is also located in the Juniper Library District branches.


Public Affairs
Western Area Power Administration
P.O. Box 281213
Lakewood, CO 80228
phone: 720-962-7050

Last modified on September 5th, 2023