MNC project overview

MNC project overview

Overview of Southwest Colorado Power System 

The power system in Southwest Colorado relies on a limited network of generation and transmission

infrastructure to maintain reliability and meet member load. In 1995, Tri-State and other regional utilities recognized that the transmission system was becoming stressed and new lines needed to be built and existing lines needed to be replaced or upgraded. Tri-State studied multiple ways to address the aging infrastructure, improve reliability and meet significant new demand in the region. Among other things, the studies showed the need to rebuild the existing Nucla-Sunshine transmission line and upgrade the Montrose-Nucla-Cahone (MNC) infrastructure from 115kV to 230kV to increase capacity. In 2012, Tri-State completed the Nucla-Sunshine line. 

In 2011, Tri-State formally began the process to make infrastructure improvements to MNC and upgrade the capacity from 115kV to 230kV. Tri-State continues to work through the process, which includes review by several state and federal agencies.

Purpose and Need

In July 2013, the Colorado Public Utilities Commission issued Tri-State a Certificate of Public Convenience and Necessity for the Montrose-Nucla-Cahone Transmission Improvement Project, essentially confirming that the project will provide an essential public service. The Commission based its determination on the following needs:

• Address aging infrastructure: The existing line was built in 1958 and has exceeded its expected lifespan of 50 years. The line is requiring more frequent, substantial and costly repairs, and the age of the poles has made them susceptible to cracking, rotting, insect infestation and woodpecker damage. Greater maintenance means greater costs, as well as increased opportunities for incidents that could threaten worker safety. 

• Meet member growth and improve reliability: Existing and future operational restraints exist because the physical limitations of the line affect Tri-State’s ability to serve projected load growth for its cooperative members in southwestern Colorado. In addition to leaving the utility at greater risk of outages, the existing line simply does not have the capacity to handle future customer demand in the region.

• Regional Transmission Benefits: Rebuilding the MNC line aligns with larger regional goals within the overall system in southwestern Colorado. Strengthening the electrical grid requires system upgrades, and the MNC upgrade is a piece of this greater objective.

• Provide reliable broadband services:
Tri-State is a major partner in providing and maintaining a telecommunications network on the MNC line and others across its system. The upgrade will ensure reliable broadband service in the area.

Design and Construction

The MNC Transmission Line Improvement Project will upgrade the existing 80-mile line, which crosses approximately 35 miles of public lands administered by the Bureau of Land Management (BLM) and about 23 miles of lands administered by the U.S. Forest Service (USFS), including the Grand Mesa, Uncompahgre, Gunnison, and San Juan National Forests. An additional 23 miles of existing line crosses lands managed by the State of Colorado or private landowners. The project spans Montrose, Ouray, San Miguel and Dolores counties; all necessary local approvals and land use permits will be obtained prior to construction.

The transmission line will be upgraded to 230-kV using primarily wooden H-frame structures and steel monopole structures. The H-frame structures will be approximately 25 feet taller and 10 feet wider than the existing structures and will require an additional 50 feet of right-of-way for a total of 150 feet. Construction of the project will be completed in two segments, with work on the Nucla Substation and Nucla to Cahone segment beginning in 2017 and work on the Nucla to Montrose segment beginning in 2018.

Project Oversight and Environmental Stewardship

Tri-State takes pride in minimizing impacts to the natural environment, property owners and other stakeholders during the construction, operation and maintenance of transmission lines and other critical infrastructure. The MNC project occurs largely on federal lands and is therefore subject to review under the National Environmental Policy Act (NEPA). Tri-State has contracted a third-party consultant to prepare an Environmental Assessment (EA) to support the BLM and USFS’s NEPA review. The draft EA will be available for public review in late spring/early summer of 2015. 

The Bureau of Land Management (BLM) Southwest District has been designated as the Lead Federal Agency and is completing an Environmental Assessment (EA) to evaluate the impact of this project. The United States Forest Service (USFS) is a cooperating agency in the EA, and will issue a separate decision to authorize work on National Forest System lands. Both agencies will use the EA to make independent decisions related to the approval of the proposed project to construct, operate and maintain a transmission line through their respectively administered lands.

The BLM will decide whether to approve the ROW, not approve the ROW, approve the ROW with modifications, and if so, under what terms and conditions. The USFS will decide whether to approve the proposed action, an alternative to the proposed action or the No Action alternative. The USFS would authorize the selected alternative with a Special Use Permit for the construction, operation and maintenance of the line, with conditions to include in the Construction Stipulations, and conditions in the Operation and Maintenance Plan. The BLM and USFS can render separate decisions regarding the proposal.

A small portion of the MNC project occurs in designated critical habitat for the Gunnison Sage Grouse (GuSG). This bird was recently listed as threatened under the Endangered Species Act, and Tri-State is working with the BLM, Colorado Parks & Wildlife and the U.S. Fish and Wildlife Service to identify design features and mitigation measures to minimize impacts and protect the species and its critical habitat. Key measures include Tri-State voluntarily agreeing to use single steel pole structures (as opposed to wood pole H-frame structures) in the GuSG critical habitat to reduce perch and nesting surfaces for the grouse’s avian predators, and fitting pole tops and arms with perch discouragers. In addition, Tri-State is considering reasonable routing alternatives to the existing alignment to further minimize impacts to the GuSG.