Moving Power Lines Underground: Benefits & Challenges

As our communities continue to rebuild following hurricanes Debby, Helene and Milton, many of us have seen firsthand the importance of maintaining and continuing to advance our resilient power grid. But what does this mean when it comes to our network of overhead power lines?

As we continue to rebuild from three major hurricanes in as many months, we often get asked: Why don’t we simply bury all power lines? We work diligently to identify targeted opportunities to bury power lines in areas where it makes the most sense. However, it is important to recognize that self-healing grids cannot withstand the level of devastation that many areas saw during the extreme weather events of September 2024.

Moving existing overhead lines underground

Burying power lines, also called “targeted undergrounding,” helps to improve storm response and reliability by using smart data to strategically identify the power lines that would be most beneficial to move underground. These lines include those that are outage-prone as well as those that are difficult to access, such as lines located in back lots, on steep slopes, in heavily wooded areas, etc.

Strategically relocating these lines underground can significantly reduce power outages and momentary service interruptions and can also reduce costs while quickening restoration time after a major event.

The process of moving an overhead power line underground begins and ends with working closely with those directly impacted:

1. Duke Energy obtains signed permission from property owners to perform work.
2. To prepare the worksite, our workers will mark the proposed utility routes with stakes and flags. You can expect to see colored paint markings on and around your lawn during this part of the process.
3. We will review the site plan with property owners to ensure we are aware of any concerns about unmarked underground equipment or facilities.
4. Crews, trucks and equipment will begin their work on undergrounding the lines. First, drilling equipment will be used to install the lines underground. Whenever possible, we will use low-impact drilling equipment to minimize property disruption.
5. Next, we will install any additional equipment needed to provide underground service in your area. This could include pad mount transformers and meter base adapters.
6. Once installation is complete, a short outage will occur as we switch the service and energize the new underground lines. We will communicate the outage date and time with property owners in advance so you can plan accordingly.
7. Finally, once the entire installation project is complete, crews will return to remove the overhead electric lines. We will work with property owners to restore your property after construction.

What are the benefits of burying power lines?

Undergrounding power lines can help to reduce the number of power outages during an emergency event, improving the quality of electric service in outage-prone areas and minimizing service interruptions related to downed trees, ice, high winds and other instances of weather events.

This tactic can also aid in ensuring that power is restored faster for customers directly impacted by major storms or other emergency events. Before and after these events, underground power lines may not require tree or vegetation management work in order to work on hard-to-access lines, greatly reducing or eliminating the frequency needed for this type of work.

What are the risks and challenges associated with burying power lines?

While this work does result in significant reliability improvements, it does not guarantee that underground lines are fully protected from extreme weather or other emergency events.

On top of generally being more expensive than overhead lines to build and maintain, underground power lines are not always practical in unstable sandy or rocky mountainous areas and can be susceptible to damage from storm surge and flooding, as we’ve seen recently.

Hurricanes Helene and Milton, which both made landfall in late September 2024, are strong examples of this. These storms posed unique challenges not previously encountered in tropical storms due to the intensity of flooding. In western North Carolina, we saw underground wires damaged by water infiltration and exposed by flood erosion and falling trees, in addition to being washed away in some cases. In Florida, we experienced severe damage to critical infrastructure equipment such as switchgears and transformers due to storm surge flooding the equipment with salt water.

Below are images of underground power lines and other equipment exposed and damaged by storm surge from recent hurricanes.

To learn more about targeted undergrounding efforts, you can find more information on our website.