Puget Sound Energy transmission line project
Central Pierce-Alderton 115 kV transmission reliability improvement project
2018 project updates
- Construction of Plase 2 began in June 2018 and will last approximately 5 months.
- Phase 1 of construction was completed in 2014.
PSE is working to improve electric service reliability for approximately 24,000 customers in Sumner, Bonney Lake, Orting and central Pierce County. Currently, the local electric system is prone to power outages due to limited capacity and redundancy.
The existing 38-mile transmission line ties together three major substations in the area. If there is an outage on the line, the system does not have the redundancy to continue reliably serving customers, increasing the possibility of outages for many customers in the area.
To strengthen the current system and improve electric service reliability for our customers, we will construct three new 115 kilovolt transmission lines from points along the existing transmission system to the Alderton substation in Puyallup. The lines will be constructed in two phases:
- Phase 1 (completed in 2014): Constructed one 115 kV transmission line along four miles of an existing water main corridor. The line runs from an interconnection point on an existing 115 kV line approximately 1,000 feet west of our existing Rhodes Lake substation in Bonney Lake to the Alderton substation.
- Phase 2: Construct two 115 kV transmission lines along 3.2 miles of an existing regional utility corridor. The two parallel lines will run from the Alderton substation to an interconnection point on an existing 115 kV line at Myers Rd E near Highway 410. See the project map for reference.
By constructing the new lines, we are segmenting the existing system into three smaller, more reliable systems that can back each other up in the event of an outage on one of the lines. This will add redundancy to the overall transmission system, limit the number of affected customers during an outage, and eliminate electric capacity constraints on the existing system – ultimately keeping the lights on for our customers. We estimate that this project will allow us to reduce outage risk for all 24,000 customers by at least 50 percent.
This project is related to our Pierce County 230 kV project , which constructed approximately eight miles of new 230 kV transmission line from the White River substation in Bonney Lake to the Alderton substation in Puyallup. The Pierce 230 kV project will be completed in late 2017. These projects work together to strengthen the overall electric grid and increase electric reliability for our customers in Sumner, Bonney Lake, Orting and central Pierce County.