Vegetation Management on Rights-of-Way

Electric utilities are charged by state and federal regulatory agencies with the responsibility for providing safe, reliable electric service to their customers. Customers may include homeowners, businesses, municipalities and other utilities. Electricity is a product which is needed on demand and cannot be stored in large quantities. Because it is essential for domestic use, economic growth and providing vital services, the pathways for the flow of electricity must be kept open at all times.

Trees and other vegetation can cause interruptions of service by growing into, or falling through power lines. These interruptions are a major concern of electric utilities because service is not being provided to customers when needed. A loss of service is not only costly and inconvenient to customers - it can also be life-threatening to people on life support systems. For many utilities, tree related outages rank among the leading causes of interruptions of electric service during both normal operating conditions and during major storm events.

Properly maintained rights-of-way are essential to provide safety for customers and workers, minimize tree-related outages, provide access for inspection and maintenance of facilities and for timely restoration of service during emergency conditions. The goal of right-of-way vegetation management programs is to provide safe transmission and distribution service and to minimize interruptions caused by trees and other vegetation while maintaining a harmonious relationship with varied land uses and the environment.

Most electric utilities employ a combination of control methods for right-of-way vegetation management in a process known as "Integrated Pest ¹ Management" (IPM). Integrated pest management is a system of controlling pests (weeds, diseases, insects or others) in which pests are identified, action thresholds are considered, all possible control options are evaluated and selected control(s) are implemented. Control options - which include biological, chemical, cultural, manual and mechanical methods - are used to prevent or remedy unacceptable pest activity or damage. Choice of control option(s) is based on effectiveness, environmental impact, site characteristics, worker/public health and safety and economics. The goal of an IPM system is to manage pests and the environment to balance benefits of control, costs, public health and environmental quality.

¹ In vegetation management, "pest" refers to trees and other vegetation which are capable of endangering the safety of the public and workers and the reliability of service of the lines.

As part of their IPM Program, nearly all utilities utilize some mechanical vegetation control. However, cutting or mowing vegetation perpetuates the growth of incompatible (tall growth) vegetation because of the biological response of sprouting. When a single stem is cut, multiple sprouts can grow from the severed stump or the root system (so-called "root suckering"). These sprouts are fast-growing because they are fed from the root system which is already well established. A repetitive cycle of cutting and sprouting results in an increasing density of tall growth species.

It is a common public belief that mechanical/manual methods (power saws and mowing) are safer and have less environmental impact than herbicide methods. Often overlooked are environmental and safety concerns associated with repeated cutting of vegetation such as: soil compaction from heavy equipment, damaging sensitive wetland areas, worker and environmental exposure to petroleum products (which are more toxic than many herbicides used for R/W maintenance), the potential for physical injury from sharp tools and equipment and the repeated, significant alteration of potential wildlife habitat.

In many instances, herbicides are preferred because they control the entire plant and greatly inhibit re-sprouting, thereby reducing the need for repetitive cutting. Even though most herbicides used for vegetation control have low human and animal toxicity, some utilities minimize herbicide use because they fear adverse public reaction from the use of synthetic herbicides. Improved environmental safety of available products and technology and the potential for increased competition in the utility industry may result in increased herbicide usage.

The long-term goal of a vegetation management program is to provide for public and worker safety and to provide reliability of service by converting right-of-way plant communities from predominately tall growing plant species to communities dominated by low growth plant species. This can be accomplished by selectively controlling tall growing plant species, while preserving low growing grasses, herbs and woody shrubs over a period of many years. With proper management, the low growing vegetation can eventually dominate the right-of-way and retard the growth of the tall growing vegetation, providing control of incompatible vegetation and reducing the need for future treatments.