Vegetation in close proximity to the electric facilities is not only the leading cause of power outages, but also represents a safety risk to utility workers and the general public. VEC takes the responsibility to reduce the risks to both safety and reliability very seriously.
Statement of Purpose/Goals & Objectives
VEC’s Forestry Department has the responsibility of maintaining vegetation so as not to threaten the safety or integrity of overhead electric facilities. The primary goal of the vegetation management program is to develop an environment-friendly approach to vegetation management designed to improve reliability, provide for safe and efficient operation and maintenance of distribution and transmission systems, maximize cost-effectiveness and enhance member satisfaction.
Integrated Vegetation Management
Integrated Vegetation Management (IVM) is a system of managing plant communities that considers a combination of methods to control undesirable vegetation and includes biological, chemical, cultural and physical (e.g. mechanical and manual) methods of control. IVM assists managers in improving the efficiency and cost effectiveness of vegetation management by utilizing the most appropriate and effective control methods based on individual site conditions.
Properly implemented, IVM is recognized as a methodology that encompasses a range of industry-established best practices. In general, physical and/or chemical control methods are the most appropriate and most frequently used vegetation control options for utility rights-of-way. The retention of low-growing, compatible vegetation will inhibit the future growth of incompatible species and is therefore considered a form of biological control. Other biological controls (e.g. grazing by animals) and cultural controls (e.g. using fire to eliminate undesirable vegetation) have limited application and are seldom used as utility vegetation maintenance techniques.
VEC has selected IVM to promote sustainable plant communities which are compatible with the electric facilities and discourage incompatible plants (i.e. plant species which at maturity will attain a height of greater than +/- 15 feet tall) that may pose concerns including safety, access, fire hazard, electric service reliability, emergency restoration, visibility, regulatory compliance, environmental and other specific concerns.
Important benefits of IVM include:
Determination of Vegetation Management Needs
VEC’s Forestry staff is responsible for establishing a preventative maintenance strategy, identifying an appropriate routine maintenance cycle, identifying necessary funds to complete maintenance on the desired cycle, determining scheduling units, prioritizing scheduling units and completing routine maintenance systematically and on the desired cycle. Vegetation maintenance records, service interruption data, detailed Line Worker Reports, aerial and ground patrols and member-customer input all contribute to assigning priorities for vegetation maintenance each year.
There are several factors the Forestry staff must consider when evaluating vegetation management needs. These include the frequency of service interruptions, vegetation quantities and characteristics, time elapsed since last treatment and member-customer requests. Extreme weather conditions such as thunderstorms, snowstorms and high winds will also need to be taken into consideration and often take priority over treatments scheduled based on normal factors.
Vegetation Maintenance Cycle
VEC has established a target of attaining a five-year vegetation maintenance cycle on transmission rights-of-way and a seven to ten-year maintenance cycle on distribution rights-of-way.
Undesirable Vs. Desirable Vegetation
Essentially, all of the commercial tree species found in the forest types identified within VEC rights-of-way are classified as incompatible with electric utility lines. They are generally moderate to fast growing species, reaching mature heights in excess of 15 feet tall. Immature trees (less than 4 inches in diameter at breast height and with the capability to exceed 15 feet in height) are defined as incompatible target brush.
Although immature target brush does not pose an immediate threat to system reliability or safety, allowing it to mature can increase maintenance costs and impede or prevent accessibility to electric facilities. Aggressive incompatible target brush species control is crucial in limiting VEC’s future vegetation control workload and cost increases.
While individual healthy trees existing within rights-of-way may be pruned and maintained in order to avoid contact with conductors, the majority will be eliminated when economically feasible, and planting of these tree species within the rights-of-way is strongly discouraged.
The most common reason for pruning an incompatible tree rather than removing it is landowner request. This may be because of the aesthetic value, or because of its value as a shade tree or as a screen from a highway. Apple trees, due to their value as wildlife feed, will be pruned for maximum clearance without jeopardizing their survival and removed only when necessary.
Not all vegetation found in VEC rights-of-way is undesirable. There are many low-growing plants and shrubs such as lilac, serviceberry, dogwood, hawthorns, honeysuckle, etc., which can be compatible with utility lines. In wetlands and boggy areas, species such as speckled alder and pussy willows, as well as cattails, ferns and many other low growing plants and shrubs are quite compatible.
Retaining or encouraging the growth of low-growing desirable vegetation will help to suppress the growth and density of less desirable species. While shrub growth will not eliminate the encroachment of tree species, it will compete with the other species for nutrients, light, and space.
Significant shrub growth is not retained in the area immediately surrounding pole locations or directly under the conductors. These areas must be kept free of obstruction to facilitate access to the poles and create an open climbing space. This is especially important for any plant species bearing briars or thorns, as they could cause a puncture hole in a lineman’s rubber gloves, thereby creating the risk of electric shock.
Generally involves the cutting of all brush (up to 25 ft. on each side of the center of the pole line for distribution lines and up to 50 ft. on each side for transmission lines) to ground level, as well as proper pruning of all branches growing towards conductors and removal of any/all trees, which can not be properly pruned to provide adequate clearance.
Hazard Tree Removal
Involves the removal of trees, which due to size, location and/or condition, have a potential for damaging the conductors or structures now or within the next ten years. These trees will be removed regardless of distance from the center of the pole line.
Minimum Tree-to-Conductor Clearances
Distribution System - A minimum of 10 feet of clearance on each side of the outside conductor and 20 feet of clearance for all branches that overhang the conductors must be achieved. Additional clearance is necessary on branches that could bend (due to snow or ice loading) or break and contact the conductors below.
Transmission System - A minimum of 15 feet of clearance on each side of the outside conductor must be achieved. No branches shall be left overhanging the conductors.
These are the minimum required clearances. Individual tree location, health, species, and growth rate must be considered when determining appropriate/acceptable clearances.
Brush, branches and woody debris from pruning and removal operations along roadsides and within 100 feet of house sites will be chipped. In all other areas, brush will be moved away from the poles, out from under the conductors and windrowed (placed in a long, low heap or pile) off to the side.
Trees, which have been cut remain the property of the landowner and will be left on site. Trees that appear to contain log products will be left in long lengths (except when it is necessary to take them down in smaller sections) and all other wood will be left in manageable lengths, unless directed otherwise by the member.
The Contractor has the primary responsibility for contacting property owners prior to the commencement of vegetation management work. Personal contact will be made wherever possible and a VEC member notification hang tag will be left at all residences along the rights of way scheduled for maintenance activities.
Where personal notification has not been made, maintenance activities will not take place for a minimum of 5 days following the placement of a VEC member notification hang tag. If 5 days have passed and the member has not made contact with the foreperson identified on the hang tag, maintenance activities will take place without any further notice.
A reasonable effort will be made to identify property owners at locations where there is not a nearby residence.
When applying herbicides, VEC conducts general notification to landowners according to Vermont Public Service Board Rule 3.6 and the Vermont Regulations for the Control of Pesticides. Herbicide Notification Coupon (PDF). VEC Forestry staff will provide the Contractor with the physical address of all individuals who have previously requested that herbicides not be utilized on their property.
The Contractor is responsible for making personal contact with each individual who has requested that herbicides not be used and meeting with them to clearly identify their property lines on the ground prior to any herbicide applications.
In instances where the Contractor is unable to identify and/or contact a property owner, the Contractor will work with VEC’s Forestry staff to determine the appropriate course of action prior to any herbicide application.
VEC’s vegetation management program is based on the following basic principles, as published in the National Rural Electric Cooperative Association (NRECA) Cooperative Research Network’s (CRN) Vegetation Management Manual.
VEC’s vegetation management program is administered by a professional forestry staff with a dedicated annual budget.
VEC’s forestry staff continually works to improve management processes used to assess and prioritize vegetation maintenance needs in order to facilitate a preventative maintenance strategy. While there will always be a need for some level of unplanned vegetation maintenance to address danger tree removals and hot spots, separate contracts are awarded for this type of work in an effort to limit the impact on scheduled maintenance activities and allow for completing routine maintenance systematically and on the desired cycle.
VEC’s Vegetation maintenance activities are conducted by Qualified Line Clearance Contractors who are bound by contract to adhere to the American National Standards Institute (ANSI) Std. A300, "Tree, Shrub, and Other Woody Plant Maintenance‑Standard Practices", and other established and widely accepted pruning guidelines such as those presented in The Society of Arboriculture’s “Best Management Practices Utility Pruning of Trees” and/or Dr. Alex Shigo's booklet titled "Pruning Trees Near Electric Utility Lines”, as well as “VEC’s Specifications for Vegetation Management on Transmission and Distribution Systems”. VEC’s Forestry staff conducts routine maintenance inspections and contract administration to ensure that maintenance activities are conducted in accordance with established standards.
Following a thorough review and evaluation of the benefits of an Integrated Vegetation Management (IVM) strategy, VEC will introduce the selective use of herbicides to control vegetation in 2009. Herbicide application will be expanded, where appropriate, on the remainder of VEC’s transmission system over the next 5 years and on the remainder of VEC’s distribution system over time.
VEC’s Forestry staff has worked closely with Information Technology (IT) to develop a comprehensive record-keeping and reporting system. Detailed information regarding right-of-way conditions and maintenance activities are now entered into an access database. This provides continuous, long-term information to assist in justification of management decisions, annual forecasting and budgeting, prioritizing and scheduling work loads, monitoring crew productivity and determining the most cost-effective vegetation maintenance methods. VEC is currently investigating additional technology to further expand data collection, record keeping, tracking and reporting capabilities.
VEC’s Forestry staff includes a SAF (Society of American Foresters) Certified Forester and an ISA (International Society of Arboriculture) Certified Arborist.