Dominion Energy
tysons idylwood Improvements atTysons Substation tysons substation Idylwood substation 495 66 66 267 267 Lessburg Pike Lessburg Pike Lessburg Pike Lessburg Pike Lessburg Pike Lessburg Pike HDD OPEN TRENCH Phase i Phase h Phase g Phase f Phase e Phase D Phase c Phase b Phase a
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project overview

The Idylwood - Tysons 230kV Underground Electric Transmission Line Project was approved by the Virginia State Corporation Commission in September 2018. The final route consists of an underground build that allows us to accommodate the needs of the community and meet growing energy demands in Fairfax County.

Existing dominion line #124

Existing Line


Dominion Energy has an existing right of way corridor containing a 115 kilovolt (kV) transmission line that runs from our Gainesville Substation north to our Loudoun Substation. This line will be converted to operate at 230 kV and will not require construction work in this portion of the right of way.

Construction Methods

Open Trench

Open Trenching

Open Trenching involves excavating along a pre-determined path so transmission cable can be safely installed underground.


Horizontal Directional Drilling

Horizontal Directional Drilling allows for the installation of transmission cable underground in minimally-accessible areas, such as under highways and waterways.


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Improvements At Tysons Substation

Originally built in 1964, the Tysons Substation is located at 8440 Tyco Road. A remodel and upgrade of the substation is necessary to support the new Idylwood-Tysons 230 kV underground transmission line. The remodeled substation will be quieter, more efficient, and operate within the existing property while allowing us to meet the growth demands of the area.

Highlights of the work include:

  • Replacing typical air-insulated substation equipment with Gas-Insulated Substation (“GIS”) equipment. GIS is the best available technology that can be used in a smaller footprint.
  • Removing one backbone structure, and replacing the two remaining 70 foot backbone structures with 75 foot backbone structures.
  • Removing six distributions poles, and placing the existing distribution lines underground.

As of July 20, 2020, a site plan for the work will be resubmitted to Fairfax County for modifications. The site plan was last submitted April 8, 2020.