The Puget Sound Energy (PSE) service area experienced winds ranging from gale force to the equivalent of a category two hurricane over Dec. 14-15, 2006. With soils saturated from previous heavy rains, tens of thousands of trees uprooted, falling onto power lines and substations. More than 40% of PSE’s transmission lines were knocked out of service.

In the aftermath of the storm, PSE began a review to identify what additional measures could be taken to prepare for severe storms, minimize or prevent storm damage and improve the response when outages occur. As trees played a dominant role in the extent of system damage incurred, any successful avoidance or minimization of future storm damage will necessarily entail new, altered or increased vegetation management activities.

Ecological Solutions Inc. of Sherwood Park, Alberta was contracted to audit PSE’s vegetation management program and to assess and quantify conditions that impact tree-caused service interruptions.

This report describes:

  • the investigation process,
  • data collection and analysis
  • resulting conclusions, and
  • recommendations of means and options for transmission system hardening.

This section of the report provides a synopsis of the project, its 27 findings and six recommendations....(Read more...)