A project scheduled to begin this summer will tunnel under the Four Mile Run near the Route 1 bridge to move overhead power lines underground.
As part of the project, Dominion Energy will rebuild its Glebe Substation next year, modernizing the facility that was built in the 1970s and is reaching the end of its service life. The substation serves parts of Arlington and Alexandria.
“Everything will look a lot cleaner, a lot of the equipment will be a lot smaller,” said Ann Gordon Mickel, Dominion Energy’s communication and community lead for the project.
A virtual community meeting will be held tonight (Wednesday) at 6:30 p.m. to discuss the status of the project and what to expect during and after construction.
When work begins, a 250-foot by 250-foot area will be fenced off in the Potomac Yard shopping center parking lot in Alexandria to allow for a 40- to 50-foot deep pit for tunneling.
In Arlington, a pit will be constructed at the substation and there may be temporary intermittent closures on S. Eads Street, as well as on nearby sidewalks and pedestrian paths. Electric service will not be affected.
The underground line will run between the substation and the Potomac Yard Transition Station, which will be decommissioned at the end of the project. The rebuilt Glebe Substation will incorporate new technology, requiring less maintenance and making it more reliable, the power company said.
“Any time you address aging infrastructure and replace it with new technology the reliability always enhances,” said Greg Mathey, a manager of electric transmission communications for Dominion Energy. “The transmission system feeds the distribution system, so the more reliable and hardened we can make the transmission system, the better the distribution system can perform.”
The construction to convert to underground lines is scheduled to continue through 2024. The whole project should be completed by late 2025.
The entire project is expected to cost about $122.8 million. The State Corporation Commission, which regulates utilities in Virginia, approved the project in 2019. It was originally scheduled to be up and running by this month, but due to the nature of the construction, the timeline was pushed back.
Using a trenchless microtunneling method will increase costs by about $16 million — but it shortens the construction timeline, according to project documents.
This type of tunneling will also reduce construction-related impacts to the Potomac Yard shopping center, as it won’t require as much space for pipes above ground.
The overhead lines that can be seen over Four Mile Run will be removed at the end of the project.