Trees are not only beautiful hallmarks of our emerald city: Seattle’s urban forest, much like City Light's public power system, also delivers important public services. Trees support residents by providing important benefits like energy-saving shade and cooling.
Like all urban infrastructure (utilities, parks, roadways, sidewalks and staircases), trees require active management. Throughout the Pacific Northwest, trees that grow into or fall on overhead power lines are one of the largest reported causes of electric power outages. Because of the potential public safety and service interruption risks, line qualified vegetation management work is highly technical, standardized, and regulated.
This is where City Light’s Vegetation Management & Wildfire Mitigation team comes in: We support the public throughout our service territory by planting, monitoring, and managing trees and vegetation to maintain legally required clearances near critical electric grid infrastructure.
300+ trees planted
We love trees! Our vegetation management program is committed to growing and improving the health of our urban forest. Each year we support the planting of more than 300 trees within Seattle, focusing on overburdened communities. Additionally, we support planting efforts throughout our service area by working with project delivery, engineering, and environmental groups during planning and implementation.
Our Management Work
Under state and federal mandates, City Light maintains clearances to above and below ground electric infrastructure by mitigating vegetation risk at the lowest level possible. We promote electric reliability, and place high priority on the safety of our crews and the communities we serve. We do this through effective tree management around our complex network of substations, poles, power lines, and transformers.
Our team practices industry standards from the International Society of Arboriculture and American National Standards Institute. We’ve been recognized by the Arbor Day Foundation for best practices in utility arboriculture and awarded the annual Treeline USA designation consecutively since 2013.
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 Facility | Description | Clearance 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 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.
Trees for Seattle
City Light works with many City of Seattle departments to manage the urban forest. Together we are Trees for Seattle: our city’s collective effort to grow and maintain a healthy and equitable public resource.
