Issue brief on the MNC Environmental Assessment

Issue brief on the MNC Environmental Assessment


The existing Montrose-Nucla-Cahone 115 kilovolt (kV) transmission line has been in place for almost 60 years. Tri-State studied multiple ways to address the aging infrastructure, improve reliability and meet significant new demand in the region. These studies showed the need to rebuild this transmission line from 115kV to 230kV to increase capacity. So in 2013 Tri-State began the permitting process to upgrade/rebuild the line by initiating the Montrose-Nucla-Cahone Transmission Improvement Project (MNC Project). 

An upgraded transmission line will strengthen the electrical transmission system, which will enhance Tri-State’s abil-ity to serve projected load growth for its cooperative members in southwestern Colorado and lessen the risk of outages. It will increase capacity for new power generation within the overall system in the region. The upgrade will also replace the existing fiber optic cable that is currently located on the line and ensure continued reliable emergency communications and broadband service for the region. 

The NEPA Process 

The existing 80-mile MNC line crosses lands managed by the U.S. Forest Service and Bureau of Land Management (BLM) (see map). Therefore, the plan to rebuild the line is subject to review under the National Environmental Policy Act (NEPA) and requires the completion of an Environmental Assessment (EA). The BLM Southwest District is the Lead Federal Agency and is completing the EA. The BLM initiated the NEPA process on May 5, 2014. 

Tri-State is the applicant in this federal process and has identified its preferred routing alternative. Tri-State proposes a slightly expanded existing transmission right-of-way to rebuild the line in place, including through the Dry Creek Basin, and then cross the Dolores River Canyon at a new, safer and environmentally acceptable location. Tri-State has proposed a comprehensive set of conservation measures and best management practices that have been incorpo-rated into the EA to mitigate impacts to the environment, land use and natural resources. 

The MNC Environmental Assessment (EA) 

On November 3, 2015, the BLM released the Draft EA for the MNC Project and is seeking comments. The EA is quite extensive so a quick summary of the alternatives being considered follows: 

Alternative A - Tri-State’s Proposed Action: Tri-State would rebuild the existing 115-kV transmission line to 230-kV largely utilizing the existing transmission line corridor with the exception of the Dolores River Crossing where a re-route is proposed to address maintenance access and erosion concerns with locations of specific structures. 

Alternative B - No Action: Selection of this alternative means the project will not be built and the electrical and physical deficiencies (aging infrastructure, need for improved reliability, load serving, facilitating renewables) will go unresolved. Under this Alternative, the line will continue to deteriorate, future service capacity will be threatened and there will be no benefits to the emergency response communication system or related broadband system benefits. 

Alternative C – BLM Routing Options: This Alternative involves three variations of the proposed action: 1. Up-grade-in-place everywhere including at Dolores River (no new crossing); 2. Relocate line to parallel State Highway 141 in Dry Creek Basin, and 3. Use both routing options; upgrade-in-place at Dolores River crossing and relocate line to parallel State Highway 141 in Dry Creek Basin. 

Montrose-Nucla-Cahone Rebuild Project 

The BLM and Forest Service decision makers are seeking public input on the project, including with respect to the Dolores River Canyon crossing and the route through the Dry Creek Basin. 

Dolores Canyon Crossing -- The upgraded line will either cross the Dolores River Canyon at the existing location or at a new location one mile downstream of the present crossing. Tri-State prefers the alternate crossing one mile downstream because it provides safer access for maintenance and construction crews and is more environmentally protective by removing the alignment from highly erosive soils. The former Dolores Crossing will be reclaimed upon removal. 

Dry Creek Basin – The existing line runs through the Dry Creek Basin in San Miguel County, which contains a remnant population of Gunnison sage-grouse. The U.S. Fish and Wildlife Service recently designated all habitat occupied by Gunnison sage-grouse in Southwest Colorado, including the Dry Creek Basin, as critical habitat. The BLM has put forth an alternative route that involves relocating the line from where it has been for sixty years to a new location along State Highway 141. The new alternative also is located in Gunnison sage-grouse critical habitat. Relocating the line would add an additional 1.3 miles of new disturbance within critical habitat compared to rebuilding the line in place. Tri-State has proposed draft conservation and mitigation strategy that provides various conservation measures to address construction related impacts. These conservation and mitigation projects include habitat acquisition, restoration and improvement. Regardless of the location, Tri-State has voluntarily offered to use a single pole design with the installation of perch discouragers to address agency concerns regarding the potential predation effects from raptors preying on grouse from the transmission line.