Before any tree work can be performed on private property, WMECO’s contractors must notify tree owners, except under certain easement conditions. Door hanger notifications are provided when tree owners are not home. For work on public property, permission generally is granted by the appropriate highway official or municipal tree warden.

WMECO’s program has many components:

• Scheduled Maintenance Trimming (SMT) is performed on a regular basis by electrical circuit with a goal of trimming roughly 15 percent to 25 percent of WMECO’s circuit miles every year. The clearance guidelines for SMT are: 8 feet on sides, 10 feet below and 15 feet above the line, including tall-brush removal. Trees and limbs that are decayed, insect infested, damaged or structurally weak, may be removed.
• Mid-Cycle Trimming (MCT) is periodic inspection of high-customer (“backbone”) portions of line and subsequent spot-trimming, and weak or structurally unsound limb and tree removal.
• Enhanced Tree Trimming (ETT) is extra-ordinary trimming, and weak or structurally unsound limb and tree removal, along pre-selected line portions. This is a limited program designed to improve reliability, along specific high tree-problem areas. ETT guidelines include: 8-foot side clearance; removal of all overhanging limbs where possible (minimally to a height of 20 feet); removal of all tall-growing brush under the line; and removal of trees and limbs that are decayed, insect infested, damaged or structurally weak.
• Emergency Tree-Work is cutting and/or clearing trees and limbs that: 1) have caused an outage; 2) are “short circuiting” our system; or 3) are imminently threatening to cause an outage.
• Requested Tree Work is work we may do in response to people requesting tree work on vegetation affecting our lines. “What-we-will-do” upon request depends on many factors, including line type, voltage, number of customers affected, and the degree of perceived “threat” to the electrical system.

Limbs are pruned using a tree care industry technique, known as target pruning. Each limb is pruned back to a point where it meets the branch collar so that the pruning cut calluses over and prevents decay of the pruning wound. Additionally, “directional pruning” techniques are used to promote growth away from our lines.

On a typical day, WMECO’s certified Arborist oversees approximately 15 contractor crews that are working on trees to improve reliability for our customers. In the event of severe weather or widespread outages, this number increases substantially.

Vegetation management identifies trees requiring trimming, tree removal, and woody vine removal on and around utility poles and wires. All of this work is performed by contractor tree crews who are trained in tree work and the safe work practices necessary for working near energized electric lines.

Crews complete the work in accordance with professional standards established by the American National Standards Institute and the International Society of Arboriculture. Following these guidelines helps ensure that pruning cuts minimize injury to the tree and consider the individual characteristics (size, shape, form and condition) of each tree.

During the course of a year, trees are responsible for approximately 25 percent of all service interruptions. When a storm with high winds or heavy, wet snow comes through Massachusetts, more than 90 percent of customer outages on WMECO’s system are caused by trees and tree limbs.

Trimming activities reduce both the number and duration of outages for customers, and is the most effective means of improving service reliability for customers. It also benefits the communities we serve by removing dead or diseased trees that not only threaten power lines and rights-of-way but also public roads.

• To proactively maintain reliable electric service to our customers.
• To provide visual and physical access to our equipment.
• To prevent equipment damage – replacing and repairing equipment is very time consuming and expensive.
• To promote the safety of the public, our employees and contractors, and for other utility workers (phone, cable TV) who may be working nearby