Cannon Branch 230kV Line & Substation

Construction Update

The work at the Cannon Branch substation is nearly complete, and the work on the transmission lines is nearing completion. See the "Construction Updates" link below for additional details.

The new 230kV line, approximately three miles long, was approved by the Virginia State Corporation Commission (SCC) in a final order issued Dec. 21, 2011. Refer to Route Maps below for information about the approved route.

The Cannon Branch Substation, located within the City of Manassas, will need to be expanded to accommodate additional equipment and new distribution and transmission lines.  In 2011, Dominion requested a permit from the City of Manassas for this expansion and intends to have work completed by 2013.

Project Details

Construction Updates

Transmission Line Work

  • Construction of the transmission line began earlier this year. To date, approximately 80% of the work has been completed and is expected to finish in early 2014.

Cannon Branch Substation

  • Work on the expansion of the substation is nearing completion.

New Cloverhill Substation

  • Work on the new substation near the Manassas airport will take place entirely within the substation or within the right-of-way corridor, beginning in September 2013.
Route Maps

The SCC approved Dominion’s new proposed Route in its final order on Dec. 21, 2011.

Project Description

Construct  a new 230-kilovolt line between Cannon Branch Substation in the City of Manassas and construct a new substation to be built on commercial property east of the Manassas Airport in Prince William County.

  • Approximate total line length:  3+/- miles 
  • Right-of-Way:  New right-of-way corridor is, on average, 120’ wide
  • Typical structure description:  Structure types have not yet been determined, but will likely be single-pole steel structures, average height 110 feet
Project Benefits

This transmission line and substation will:

  • Facilitate economic development in the area
  • Improve electric infrastructure to support residential and commercial customers
  • Provide flexibility to support potential future growth in the region
Project Timeline
  • Fall 2010 – Community outreach; finalize route alternatives
  • January 2011 – File application with Virginia State Corporation Commission (SCC)
  • December 2011 – Received approval from SCC to construct new facilities
  • January 2012 – Begin construction of substation and 230 kilovolt line
  • Fall 2014 – Complete substation and line construction; energize facilities
SCC Approval Process

Dominion filed an application with the SCC on February 7, 2011.  The application and further information will be available to the public on the SCC Docket Search section of the Web site, in the "Search Cases" section.  In addition, interested parties may also comment directly to the SCC by sending an email to

On Friday, September 30, 2011, a SCC Hearing Examiner found that Dominion has established need for the proposed Cannon Branch  - Cloverhill transmission line and issued a report recommending approval by the SCC.

On December 21, 2011, the SCC issued a final order authorizing the construction and operation of the line as proposed by Dominion.

Contact Us

Contact us if you have questions or concerns about the Cannon Branch 230kV Line and Substation project.  Let us know if you would like to receive project updates via email.

Questions and Answers

What happens if Dominion is not able to meet its target dates?

Dominion has a statutory obligation to serve its customers; therefore we must work cooperatively with the state regulators and localities to meet mutual goals to have service available in a timely manner to meet the needs of new commercial customers as well as provide continued reliable service to existing customers in the region.

Will Dominion require additional right-of-way?

Yes, the proposed transmission line will need to be routed in a new transmission corridor as no existing corridor is available to connect the Cannon Branch Substation to the new proposed substation east of Manassas Airport.

Will tree clearing be necessary for this line?

Yes, in some locations. Prior to building a new power line, the new corridor will be cleared to allow construction activities and eventual transmission line operation. Existing low-growing vegetation may be left in place when it does not interfere with construction activities. Additionally, trees located outside of the right-of-way which are tall enough to potentially impact the transmission line, may also be removed. These trees are commonly referred as danger trees; view a diagram of danger tree clearances.

Trees are cut to be no more than 3 inches above ground level. Clearing will be accomplished by hand in wetland areas and within 100 feet of streams. Care will be taken not to leave debris in streams or wetland areas. Matting will be used for heavy equipment in these areas. Erosion control devices will be used on an ongoing basis during all clearing activities. Property owners will be notified before construction clearing begins.

Can Dominion build a portion or the entire line underground?

Overhead (OH) transmission lines have proven to be the best choice for providing safe, reliable and economical energy to our customers. Underground transmission lines are not as desirable from an operational point of view. The duration of outages for underground transmission lines is significantly greater compared to overhead lines due to the complexities of locating failures and facilitating repairs.  Additionally, labor and material costs for the installation of a 230 kV underground transmission line would be 8 to 10 times more expensive than an overhead option.

If requested by the Virginia State Corporation Commission (SCC), Dominion would develop additional alternatives to the Cannon Branch project which could include underground.  Underground transmission projects can cost up to 10 times what an equal distance overhead line costs, and such expenses can be passed on to customers in the local area.

Under newly enacted Virginia SB 645, localities can request the State Corporation Commission to approve an agreement with the utility to have a new transmission line constructed underground when there is a feasible overhead alternative but must create special tax districts to impose and collect local tax revenue to cover the incremental costs of the underground construction. In the end, the SCC will make the final decision as to what Dominion is required to build.

What will be the environmental impact of construction of the line?

As part of the SCC application, Dominion completes an evaluation of potential environmental, cultural, and historical impacts of the project. Dominion works with many local and state agencies to complete these evaluations and mitigate any impacts. The company also submits annual Erosion and Sedimentation (E&S) Control Specifications for the construction and maintenance of transmission lines to the Virginia Department of Conservation and Recreation for review and approval. This project will be submitted for approval prior to construction. Our contractors receive copies of the E&S specifications and any additional permit conditions prior to construction and are directed to meet any requirements. The right-of-way will be rehabilitated when construction is complete.

Should I be concerned about Electric and Magnetic Fields?

Dominion is sensitive to public concern about possible health effects from exposure to electric and magnetic fields (EMF). Dominion includes data on the levels of both electric and magnetic fields produced by proposed facilities in all applications submitted with the SCC. We continually monitor EMF research and speak to our customers and employees regularly to share the latest information available.

The Virginia SCC, which regulates the construction and operation of electric transmission lines of 138kV and above, considers EMF in every application. Hearing Examiner’s remarks from recent proceedings are below.

  • March 23, 2009 Beaumeade-NIVO (Case Number PUE-2008-00063) Report of Michael D. Thomas, Hearing Examiner concludes that "… electric transmission line electromagnetic fields do not represent a human health hazard.”
  • May 4, 2010 Hayes-Yorktown (Case Number PUE-2009-00049) Report of Deborah V. Ellenberg, Chief Hearing Examiner, states, “I find that EMF has not been identified as a carcinogen for human beings despite extensive study over many years, and there is, therefore, no basis on which to prohibit the Company from authorizing appropriate uses of its right-of-way.”
  • August 23, 2011 Hollymead (Case Number PUE-2011-00015) Report of Michael D. Thomas, Hearing Examiner, states, “The proposed facilities do not represent a hazard to human health, which finding is consistent with the Virginia Department of Health’s report entitled Monitoring of Ongoing Research on the Health Effects of High Voltage Transmission Lines (Final Report) dated October 31, 2000.”

The Virginia Department of Health in its final report evaluating EMF research concluded:

"Based on the review and analysis of the exhaustive literature review and other research projects completed under the EMF-RAPID program, the Virginia Department of Health is of the opinion that there is no conclusive and convincing evidence that exposure to extremely low frequency EMF emanated from nearby high voltage transmission lines is causally associated with an increased incidence of cancer or other detrimental health effects in humans. Even if it is assumed that there is an increased risk of cancer as implied in some epidemiologic studies, the empirical relative risk appears to be fairly small in magnitude and the observed association appears to be tenuous. The studies published in the literature lack clear demonstration of a cause and effect relationship as well as a definitive dose-response gradient."

Additional information:

Where may I obtain more information on the project's SCC application?

The Virginia State Corporation Commission will issue dates for a public hearing, most likely in the project area, with an evidentiary hearing thereafter.  Citizens are encouraged to participate in the process and provide input. The SCC maintains copies of all documents related to the case. Updates about the status of the application can be found on the SCC website at

How can I get involved and better understand the transmission line planning and approval process?

Dominion welcomes comments and suggestions from property owners and the general public. Contact us for more information and please let us know if you would like for Dominion to send you project updates or invitations to future opportunities for public participation.

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