Resiliency

Tree trimming is a planned, data-driven part of Nashville Electric Service (NES)’s Vegetation Management (VM) Program to keep customer trees and power lines safely separated. Tree trimming reduces outages, protects public safety, and maintains system reliability. Vegetation growing in the wrong place can disrupt power, damage NES facilities, and pose safety hazards to workers and the public. NES’ goal is to keep customer trees alive and healthy while ensuring they do not interfere with electrical equipment. Tree trimming is not a single action; it varies based on line type, location, vegetation characteristics, and risk.

• Routine cycle trimming: Scheduled maintenance performed across the system to maintain required clearances. NES is currently on a 4-year trim cycle, covering approximately 1,200 miles per year and will be moving to a 3-year trim cycle of 1,600 miles per year.
• Hazard tree mitigation: Targeted trimming or removal of dead, diseased, damaged, or structurally unsound trees that could strike power lines.
• Secondary/service line trimming: Limited trimming is conducted when vegetation presents a realistic risk of abrasion, strain, or outage.
• Unplanned Vegetation Management work: Includes emergency, storm, hazard-trimming requests, engineering/operations requests for construction or maintenance, and hot spot or cycle buster for circuit reliability.

Tree trimming clearances are established based on factors that account for the best weather and the worst weather conditions:

• Storm hardening objectives
• Nominal line voltage
• Expected tree and conductor sway/movement under both routine and severe weather conditions
• Trim-cycle length
• Conductor sag due to load and temperature variations.
• Distribution Lines: All branches/limbs fifteen feet from the conductors, and any overhang should be removed. Vegetation ten feet below system neutral may be ok to stay in place but must be trimmed if they grow into the clearance space.
• Transmission Lines: All branches/limbs fifteen feet from the conductors in all directions,
  and any overhang should be removed.

Previously, NES targeted roughly 1,200 miles of tree and vegetation trimming each year to ensure our 4,600 miles of above-ground power lines stay on a proper 3–4-year maintenance cycle. Since 2022, we have averaged 75% completion of this goal, while accounting for factors such as necessary vendor changes, variable weather, and terrain difficulty. The new target will be 1,600 miles of vegetation management and tree trimming per year to bolster the maintenance goals.

Between July 2025 and January, NES completed approximately 600 miles of planned line trimming for the year. Since Winter Storm Fern began, crews have assessed and trimmed over 2,800 miles of additional lines to address overhanging and storm-damaged trees that pose risk of outages. An enhanced policy supports a broader commitment to fulfilling 100% of the goal for
the year.

Vegetation-related damage has been a primary cause of outages during major weather events.Tornadoes, straight-line winds, winter storms and severe storms account for 19 of Tennessee’s 20 Federal Major Disaster Declarations since 2020

• The independent, interim after-action review has validated enhanced vegetation management as critical to the health of our system and the appropriate action:
  • NES recognized vegetation management was a contributor to outages in Fern. Immediately following Fern, NES took appropriate, aggressive action to enhance vegetation trimming standards (wider clearances between trees and power lines, as well as removing any overhanging limbs). (PA Consulting Report April 2026)
• Memphis (MLGW) experienced a harsh ice storm three years ago, and MLGW adopted an enhanced tree trimming policy as a part of a greater reliability plan, which has
  resulted in the total average minutes their customers experience each year in half. The renewed efforts have had a marked impact on the reliability of MLGW’s electric grid.

* TreeCanopy.US

Tree trimming decisions are driven by data, teams that include arborists, and standardized methods.

• Professional review: Certified arborists and vegetation management specialists assess ecosystem data, outage history, line characteristics, and growth patterns. Currently, we
  have increased oversight and quality control with seven additional arborists to oversee the enhanced policy.
• Standards-based methods: NES contracts require the use of lateral pruning, as endorsed by the International Society of Arboriculture (ISA) and the Arbor Day Foundation. Lateral pruning preserves tree structure, improves resistance to high winds and heavy ice, and guides growth away from power lines.
• Technology: NES is now equipped with advanced tools such as LiDAR to use in future trimming plan considerations. Year-over-year data will illuminate areas where the trim
  cycle can be lengthened and where faster-growing vegetation needs more frequent attention.

NES’ approach extends beyond trimming. A holistic ecological focus helps:

• Reduce urban heat island effects
• Improve stormwater management
• Mitigate environmental stressors

If you answer “yes” to any of the following questions, your tree may need to be trimmed or removed.

1. Can a branch reach the line during wind or ice?
2. Is the tree directly under or overhanging a power line?
3. Is it within 15 feet of the electrical line?
4. Is the tree dead, leaning, cracked, or decaying?
5. Could trimming now prevent emergency cutting later?

Customers along planned trimming corridors and property owners with trees near overhead lines will receive the following:

• Advance notification through phone calls, emails, and mailed postcards, when appropriate
• On-site conversations between crews/arborists and property owners
• Graphics and educational resources on our website
• Dedicated channels for questions, follow-up, and access to management if needed.
  • A dedicated hotline for tree trimming has been put in place with our customer
    team and can be reached at 615-695-7400.

Customer concerns can be addressed at any point in the work process:

• Before trimming: Tree Trimming dedicated hotline 615-695-7400
• During trimming: Onsite conversations between crews/arborists and property owners
• After trimming: Tree Trimming dedicated hotline 615-695-7400

The broader objective of NES’ tree trimming policy is to maintain reliable electric service, especially during severe weather, while managing vegetation responsibly. Although the visual impact can be significant in the short term, the approach aims to reduce outages, improve public safety, and create more sustainable clearance over the full trim cycle.

One-sided trimming is used because the part of the tree closest to the power line is most likely to cause problems. The side facing the line presents the highest risk for outages, especially during wind, ice, and storms when both conductors and limbs move. By establishing adequate clearance on the utility side, crews reduce the likelihood of limbs contacting energized equipment, the leading cause of storm-related outages.

From a structural standpoint, when performed correctly using directional pruning, one-sided trimming does not destabilize a healthy tree. NES’ certified utility arborists follow standards that consider species, growth patterns, and structural integrity. Targeted pruning can encourage healthier growth away from the lines over time. If a tree is structurally compromised or likely to become hazardous due to its proximity or condition, removal and replacement is offered to the homeowner.

The effectiveness of this approach depends on proper execution and clear communication with customers. When concerns arise, follow-up inspections and adjustments ensure that both safety and community expectations are met. If the updated guidelines require that about 40% of a tree’s canopy be removed, NES will recommend to the homeowner that we remove the tree.

• NES contracts require the use of lateral pruning, as endorsed by the International Society of Arboriculture (ISA) and the Arbor Day Foundation.
• NES is recognized by the Arbor Day Foundation as a Certified Tree Line USA utility, reflecting excellence in vegetation management.
• NES management and arborists oversee trimming.