Integrated Vegetation Management
Maintaining reliable service
Trees are part of the natural beauty of the Carolinas, but trees and other vegetation are also one of the leading causes of power outages for utilities. In order to keep electricity reliable, we have a responsibility to protect the lines that deliver it to homes and businesses across our region.
Duke Energy Progress is responsible for maintaining more than 60,000 miles of power lines. These include nearly 40,000 miles of overhead transmission and distribution lines. Vegetation management as part of our power line maintenance program helps us provide safe and reliable electric service for the 1.5 million customers across our 32,000-square-mile service area.
Vegetation management along distribution and transmission rights of way helps reduce power outages for customers and enhances safety for our employees and contractors. We use an inspection process that identifies vegetation that could be a hazard to the lines and ensures that vegetation management activities follow our pruning and clearance specifications.
We regularly use tree-trimming contractors to conduct much of our vegetation management work. These qualified contractors are required to follow industry standards and guidelines for safety, quality and tree health.
Customers, property owners and untrained contractors should not prune or cut trees and plants near power lines.
Customers who have questions or concerns about right-of-way or vegetation maintenance can contact a Duke Energy customer service representative at 800.452.2777. Our customer service representatives can provide general information on vegetation and right-of-way issues, or they can connect customers to a vegetation management specialist or right-of-way professional.
Vegetation Management Methods
As a regulated public utility, Duke Energy Progress must balance the needs of our 1.5 million customers in the Carolinas with the need to control costs and provide safe and reliable electric service.
To maintain reliable service and minimize outages, it is important that we maintain trees and other vegetation along the lines that deliver electricity to our customers.
We hire qualified, trained tree personnel to inspect and clear vegetation that poses a threat to our power lines. Our integrated approach to managing vegetation in rights of way includes:
- Planned maintenance – including tree pruning or felling.
- Reactive pruning – trimming vegetation with a high or demonstrated risk of interference with lines.
- Felling trees – cutting down trees inside or outside the right of way that are discovered to be at risk of falling on or otherwise threatening a power line.
- Mowing – maintaining the floor of the right of way.
- Aerial trimming – using helicopters to trim trees along power lines in unmaintained areas.
- Tree growth management tools – proven products used by arborists for many years to maintain tree health. Once these are applied, a tree will begin to direct more nutrients to its roots making the overall tree stronger and less susceptible to drought. This approach can be an effective way to reduce the amount of vegetation that requires pruning when performing routine tree maintenance. These products do not eliminate the need for trimming, but can be less intrusive for property owners, less noticeable on the trees and less disruptive to a well-established urban tree canopy. This is currently applicable to distribution lines on a limited scope.
- Herbicide application – the use of United States EPA-registered and approved herbicides to control vegetation.
Tree maintenance practices vary based on the voltage and type of line, as well as the type of tree and its proximity to the line. In some cases, the tree may need to be cut down to provide safe and reliable operation of the line.
There are a variety of factors that determine whether or not a tree must be trimmed or cut down.
The methods used and scope of work are determined by a number of factors, including:
- Voltage of the line
- Width and location of the right of way
- Type, mature height and compatibility of vegetation around the power lines
- Federal and state requirements and other agreements that govern vegetation management
- Proximity to environmentally sensitive areas
- Type of power line facility construction
Our program uses a technique called directional pruning where applicable to maintain tree health while establishing acceptable clearance between power lines and tree branches. This pruning technique was developed by the Tree Care Industry Association, approved by the American National Standard Institute (ANSI), adopted by the arboriculture industry as its standard and endorsed by the Arbor Day Foundation and the International Society of Arboriculture.
Distribution Lines & Integrated Vegetation Management
Distribution lines carry electricity throughout a town or community from substations to the homes and businesses that we serve. They can be located underground or overhead on utility poles. Overhead distribution lines are the lines that most commonly experience outages caused by trees or other vegetation. Below are illustrations of distribution power lines:
Duke Energy Progress maintains more than 34,000 miles of overhead distribution power lines. Trees and other vegetation can pose a potential reliability and safety hazard to these lines if they are not managed proactively. Duke Energy Progress' distribution line rights of way are typically maintained at 30 feet width, allowing crews to maintain vegetation a minimum 15 feet on each side of the right-of-way centerline.
Trees and vegetation along distribution lines can often be trimmed rather than cut down. If, however, the vegetation poses a threat to the line that cannot be resolved by trimming, or if the vegetation may interfere with the line before we return for our next period of planned maintenance, it may need to be cut down.
Crews use a combination of vegetation management methods to help ensure system reliability. We use an industry-approved technique called directional pruning to maintain tree health while establishing acceptable clearance between energized wires and tree branches. At times, we may contact the customer to discuss pruning or cutting trees down to eliminate reliability issues due to re-growth before the next planned maintenance schedule.
We work proactively with customers, property owners, homeowner associations and community leaders to keep them informed of vegetation and right-of-way management activities in their area.
In residential, commercial and maintained areas, we notify customers a minimum of three days prior to the start of planned vegetation maintenance work. We typically notify customers with a door hanger, but we may also call, send a letter or knock on your door. Sometimes notification includes a combination of these methods. We’ll also provide a point of contact in case you have questions or concerns about the work being done. If our attempts to notify a customer are unsuccessful, work will proceed without further direct notification.
Although a three-day notice is typical, there are exceptions: a tree may be cut down sooner with customer acknowledgement or if it poses an immediate threat to the reliable operation of the power line. Trees that must be pruned or cut down may include live and/or dead, diseased or damaged trees, and they can be located inside or outside the right of way.
Transmission Lines & Integrated Vegetation Management
Transmission lines are our highest-voltage power lines. Duke Energy Progress has transmission lines that carry voltages as high as 500,000 volts. These lines are comparable to the interstates of a road system, carrying electricity from power plants across great distances to the towns and communities that we serve. Most transmission lines serve thousands of customers. Below are illustrations of transmission power lines:
Federal regulations require that our highest voltage transmission lines remain reliable and free from interference by trees and other vegetation at all times. A vegetation-related outage on these lines could result in the utility being fined up to $1 million per day.
We maintain our transmission lines to standards that ensure compliance with federal reliability requirements.
Crews use a combination of vegetation management methods to help uphold system reliability. We trim and/or cut down trees in our rights of way to continue to be able to deliver safe and reliable electric service to our customers. In addition, we manage vegetation in the rights of way to encourage compatible low-growing species.
If a tree is inside a transmission line right of way and matures greater than 12 feet, we will evaluate it for removal. For more information, please review the Transmission Rights-of-Way Use Guidelines/Restrictions.
We typically maintain transmission rights of way on a multiyear cycle, depending on the voltage, type of line and other factors.
In developed and maintained areas, we typically notify property owners a minimum of three days prior to the start of planned vegetation maintenance work. We usually notify customers with a door hanger, but we may also call, send a letter or knock on your door. Sometimes notification includes a combination of these methods. We’ll also provide a point of contact in case you have questions or concerns about the work being done. If our attempts to notify a customer are unsuccessful, work will proceed without further direct notification.
Rights of ways grant the right to clear trees or other vegetation within the specified corridor and typically allow the cutting of trees or vegetation that are located outside the specified right-of-way corridor if they pose a threat to the safe and reliable operation of the power line. These trees may be live, dead, diseased or damaged.