WAPA » Regions » RM » Planning and projects

Granby Pumping Plant-Windy Gap Transmission Line Rebuild Project

​Project overview

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 is rebuilding 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 will replace WAPA's existing 69-kilovolt transmission line and provide a new second 138-kV feed from north of Granby to the pumping plant using some of the existing right of way. 


Current status​: (January 2018) The construction is complete on the north and south segments, and nearing completion on the middle segment. The next stage will be seeding and remediation (i.e. filling ruts along the right of way) in the spring.

See the Construction Schedule below for more detail.​

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.​

Construction Schedule

The rebuild schedule includes rebuilding 12 miles of the current line, 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. Removal of the former line will be done once the rebuilt line is delivering power.

The general timeline for this project is:

  • December 2016: WAPA construction contract awarded
  • May 2017: Staging of materials and equipment
  • June 2017 to January 2018: Construct line
    • Mid-May through mid-August: Construct north segment (completed)
    • Mid-August through November: Construct south segment (completed)
    • November through late January: Construct middle segment and remove former wood-pole line (in progress)
  • April 2018: Complete final walkthrough, including seeding and remediation, as well as energize entire line  

Related information

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

The rebuilt north segment of the Granby Pumping Plant-to-Windy Gap transmission line is complete, Aug. 19, on the right of way near the old transmission line. The north segment is the first of the four-phased construction to ensure reliable power for the local area in Grand County, as part of the Colorado-Big Thompson Project. The rebuild replaces two single-circuit lines with one double-circuit line. The old lines will be removed once the rebuilt line is complete and energized. (Photos courtesy of WAPA staff)

See more photos on WAPA's Flickr photo album for the project     .

Page Last Updated: 1/22/2018 9:43 AM