The Bonneville Power Administration (BPA) issued a final environmental assessment (EA) for the Northern Mid-Columbia Project, finding that a West Route option for the planned 230-kV line would pose no environmental impact, BPA said March 24.
BPA is participating in the project by paying for a portion of the cost, with three public utility districts (PUDs) sharing the cost as well, BPA and the PUDs noted in a joint March 24 statement.
The Grant County PUD, Chelan County PUD and Douglas County PUD, along with BPA, have been developing the project to address load growth and mitigate grid congestion that has resulted in redispatch of hydropower resources on occasion, according to the final EA.
BPA issued a March 24 letter to interested parties notifying them of the EA and related finding of no significant impact (FONSI) for the West Route D-E and its decision to proceed with that route for the project. That route crosses the Columbia River twice, is about 8.4 miles long, and is in Chelan and Douglas counties, BPA said.
The project has an estimated cost of $23.25m for the West Route D-E, while an East Route option would be slightly more expensive and a West Route D-F option would be slightly less expensive, according to the final EA.
The new line would add operational flexibility to the grid in the region and reduce the need to decrease generation from the Rocky Reach and Wells hydropower facilities during certain conditions when transmission lines are heavily loaded, according to the final EA.
The joint project involves the construction of a 230-kV line extending from the existing Rapids switchyard owned by Douglas County PUD near the city of Rock Island, Wash., to BPA’s existing Columbia substation. The planned line is referred to as the Rapids–Columbia 230-kV transmission line.
If all of the partners decide to go forward with the joint project, construction could begin as early as 2017, BPA and the PUDs said in their statement. The line would be permitted, constructed, owned and operated by Douglas County PUD, with the partners partially funding construction and BPA adding equipment at the Columbia substation to connect the line to the Federal Columbia River Transmission System, they said.
Douglas County PUD will be responsible for engineering and designing the project to about 30% design completion by the summer, at which point the other parties will make a decision on whether they want to proceed with the project, a spokesperson for Douglas County PUD told TransmissionHub March 29.
Douglas County PUD will acquire permits and other approvals for the project and work with landowners to acquire easements where needed, according to the final EA.
About 7.8 miles of the West Route D-E would be within existing utility corridors adjacent to multiple existing transmission lines and a gas pipeline, BPA said in the FONSI. The right of way for the line using West Route D-E would be about 75 feet to 100 feet wide, and the facilities would include 67 steel pole structures ranging in height from 40 feet to 140 feet, according to the FONSI.
The project would help meet load growth by adding a new 230-kV circuit to the northern part of the Mid-Columbia transmission system, helping BPA and the PUDs improve reliability and addressing grid congestion, BPA said in the final EA.
According to the final EA, the closing of a nearby Alcoa aluminum smelter would add to the grid congestion because the large load would not be able to absorb generation from hydropower resources in the area. At the time the draft EA was written in 2014, Alcoa’s Wenatchee Works facility was in operation and it was thought that production might increase, boosting the load for Chelan PUD, but in late 2015 Alcoa said it planned to idle the facility, BPA noted in the final EA.
The Wenatchee facility was idled in December 2015, a spokesperson for Chelan PUD told TransmissionHub March 29.
The curtailment of the Alcoa facility load creates surplus power that needs to be transmitted in the area, increasing the need for the Rapids–Columbia line to improve transmission capacity, BPA said in the final EA.
The FONSI included environmental mitigation measures that would be taken to minimize any impact during construction, such as designing access roads and staging areas to minimize disturbance to soil and vegetation and drainage into surface waters, and using erosion control measures on slopes and at the two water crossings for the West Route D-E. The two waterways, Columbia River and Colockum Creek, would not see any direct impact, according to the FONSI. The route would not affect fish species because construction equipment would not enter the waterways, and any noise or activity near the waterways disturbing fish habitat would be temporary, the FONSI noted.
In addition, operation of the transmission line would reduce transmission congestion, “which would decrease the need to manage generation at the Wells and Rocky Reach dams, resulting in positive effects on water quality, which would improve fish habitat,” BPA said in the document.