Puget Sound Energy talked about underground transmission lines at an online informational meeting Monday.
PSE has been recommending an above-ground transmission line from its Murden Cove to Winslow substations, but some members of the public kept asking about an underground system.
As it has said before, cost is a major consideration. The pricetag is $5 million to $17 million per mile underground, compared with $2.5 million per mile above ground.
All 1.1 million PSE customers would help pay for an above ground system. Bainbridge Island would have to pay the difference if an underground system was used.
Another issue is maintenance. An above-ground problem can be found and repaired easier, sometimes within hours. A below-ground problem can take two to five weeks to fix. It is harder to locate the problem, and it takes longer to access the issue due to digging, etc.
“It’s a specialized repair,” said Lowell Rogers of Oak Strategic Inc. “And we don’t have a lot of underground repair staff.”
Actually, PSE has no underground lines as of yet. Rogers said outside consultants would have to be brought in.
During public comments, Stephen Hellriegel asked how the city would pay for the difference if underground was chosen.
“We don’t have any experience with that currently,” said Andy Swain of PSE. But he said the city could go after grants, long-term financing bonds or just add the cost with taxes.
Jen Summers asked if underground would lessen wildfire possibilities. Swain said wildfires in BI are not listed as a major concern, but the risk of wildfire with overhead lines wouldn’t be any different than other transmission lines already on the island.
Officials did agree with David Johnson that underground lines reduce outages caused by trees and animals.
Tom Hansen asked if some of the line could be underground, such as near the fire station and schools, and some above ground.
That would be possible, presenters said.
“We would be happy to explore the option,” Swain said. “We are not against it.”
Next steps would be for the city to pay for a feasibility study. The city would review it and if the decision was made to continue the underground system would need to be designed and engineered. Agreements would need to made on how to pay for the added costs.
The presentation
Karen Brubeck of PSE started the meeting off saying the goal of the project is to reduce power outages and improve reliability by updating transmission lines and putting a new one in. A proposed route will be selected by the end of the year.
Rogers said overhead systems are very reliable with proper vegetation clearance. But the underground option is sometimes considered because of height limitations or visual concerns.
Underground systems need vaults that are 8 feet wide, 20 feet long and 9 feet tall every 2,000 feet so workers can splice cable together, which adds to the cost. Other factors can include steep slopes, ravines, geology, wetlands, etc. Above ground can simply go over those issues.
“Underground has more direct impact on the environment,” Rogers said, adding vegetation has to be removed, the ground has to be contoured and tree roots can be damaged, killing nearby trees. “Overhead the environment is left more intact.”
