Vegetation Management

The Seattle area is known for its lush, urban forest - providing beautiful landscapes, critical shade, and environmental benefits. Our trees are also one of the main causes of power outages and can cause serious injuries when they come into contact with utility equipment.

Graphic showing how electrical power is distributed from the generation source to a residence

  1. Power is generated from dam/powerhouse
  2. Substation transformer steps up voltage for transmission
  3. Transmission lines carry electricity long distances
  4. Neighborhood substation transformer steps down voltage
  5. Distribution lines carry electricity to residents
  6. Transformers on poles step down electricity before entering residence
  7. Service line for resident 

Our Power Line Clearance team ensures the reliability of our electricity and the safety of our communities and crews through effective tree management around our complex network of substations, power lines, and transformers. We practice industry standards from the International Society of Arboriculture, American National Standards Institute, and have been recognized by the Arbor Day Foundation for best practices in utility arboriculture.

Tree Trimming and Replacement

Tree Clearance Methods

We follow very specific guidelines on the clearance of trees and vegetation near our power lines and other equipment.

City Light FacilityDescriptionClearance Objectives
Distribution Power Lines Primary Voltage 10 ft. for slow-growing species
14 ft. for fast-growing species
15 ft. overhang clearance
Service Lines and System Neutral Lines 3 ft. for slow-growing species
5 ft. for fast-growing species
City Light prunes vegetation away from Service Lines for the first 10 ft. from where they connect to utility poles
Transmission Power Lines 115,000 Volt Based on line-engineering, species, trim-cycle, and right-of-way width
240,000 Volt Based on line-engineering, species, trim-cycle, and right-of-way width
Infrastructure Underground Vaults Vaults must be accessible for maintenance work
Power Meters Meters must be accessible
Transformer 10 ft. clearance for all tree species
Utility Poles 3 ft.

Before we trim, we will visit your home to inform you of the planned work. If no one is home, we'll leave a door hanger with trimming and contact information should you have further questions.

In an emergency situation, where a tree has caused an outage or poses a safety hazard, trimming may be done immediately with a follow-up notification sent shortly after work is completed.

Removal and Replacement of Trees

We work closely with property owners to arrange for the safe removal of trees that pose a significant safety or outage risk. We provide free replacement trees, watering bags, and expert advice for customers living in Seattle through our partnership with the Trees for Seattle Program. Customers living outside Seattle will receive certificates for free trees redeemable at partner nurseries.

Graphic showing how City Light prunes trees to avoid contact with power lines