Vegetation Management is committed to ensuring safe and reliable power delivery through the comprehensive and environmentally
responsible management of the vegetation our lines and infrastructure impact.
You've trimmed my trees before, but you've never done THAT!
City Light pays close attention to what our customers are saying to us and about us, and lately we've received a
number of concerned emails and phone calls about the degree to which we're trimming trees in our service area.
We're always willing to come out and speak with concerned customers about our line clearance operations, but
we need to hear from you before the work begins to avoid disappointment, anger and/or frustration after the fact.
City Light hangs door-hanger notification cards at EVERY PROPERTY where we intend to work.
As soon as you see that door-hanger, if you have any questions or concerns about how we're going to trim your tree,
contact us immediately. Call the number on the door-hanger, or email us your name, address and the Feeder and
Site number on the door-hanger to email@example.com
There is a lot of planning, training and resources that go into the line clearance program and we'd like to take
a moment to share with you some changes that have been made within the last few years and how they've influenced
the work we do. To find out more,
The 4-Year cycle:
Utility Line Clearance best practices are defined by the International Society of Arboriculture (ISA)
and the American National Standards Institue (ANSI), and codified in the ANZI A300 Standard, Part 1.
One of the practices highlighted in the A300 is the need to trim trees on a regular cycle. To quote the A300 Standard:
Cyclical pruning has many demonstrable advantages, including enhanced utility
reliability, reduced biological and aesthetic impact on tree and neighborhoods, and stabilized or reduced
tree maintenance budgets.
In 2007 the Seattle City Council and City Light committed to a 4-year cycle which would cover our entire service area,
something we had not previously been able to do. That meant that every mile of overhead lines were to be inspected,
evaluated and trimmed for vegetative clearances that would last for 4 years. As a result City Light contractors began
trimming in areas where we may not have been for many years, and began "digging out" areas where trimming was long over-due.
A focus on tree health:
Utility Line Clearance is not always a pretty thing. While we try to take aesthetics into consideration, our contractors
work is driven by ISA and ANSI best practices for utility tree trimming - and sometimes that means taking more of the
tree away then you might expect.
As all our contractors know, trees are best able to close over wounds and stop the inward spread of decay when those
wounds are made at the branch bark collar (where the branch comes out of the trunk). The next best place to make a
cut is where two branches diverge, assuming the branch you leave is at least 1/3rd the diameter of the branch you remove.
These are the only cuts our contractors will make, and sometimes that results in more of the tree being trimmed than
if we had just made a cut at the extent of our clearance distances.
Better training, a greater focus on preserving the urban canopy and better science have taught us a lot about
how trees react to pruning wounds and City Light is committed to holding ourselves and our contractors to those
standards. While this sometimes translates to more plant material being removed, it is a decision made with the
tree's biological reaction to the pruning cut in mind.
Protecting Our Lines, Respecting Our Environment
Everyone at Seattle City Light is committed to producing and delivering environmentally responsible, safe, low cost and reliable power -
Vegetation Management is no exception.
It's no easy task; with over 1,700 miles of lines running through eight cities and Unincorporated King County, and 657 miles
of transmission right-of-way spread across five counties, we have hundreds of thousands of trees, shrubs, vines, and landscapes to
maintain. With a small core of dedicated utility vegetation management professionals and a network of highly trained, qualified
contractors we work year-round to find solutions to these ever-growing challenges.
The utility vegetation management industry is evolving and City Light is growing with it. In the last 25 years advances in arboriculture -
the study of trees, shrubs and vines - have unlocked a deeper understanding of how woody plants respond to pruning and injury.
Come explore our programs - find out more about who we are, what we do, how and why. Learn about the challenges and opportunities
Vegetation Management faces as the demands for reliable, safe energy and our urban forests continue to grow.