Seattle City Light Climate Change Vulnerability Assessment and Adaptation Plan

Seattle City Light is the city of Seattle’s publicly owned electric power utility. The Seattle City Light Climate Change Vulnerability Assessment and Adaptation Plan researches and evaluates the impacts of climate change on the utility and develops strategic actions to maintain reliable, safe, low-cost, and environmental sustainable power to the Seattle region despite changing climate conditions.

The vulnerability assessment analyzes eight effects of climate change (e.g. sea-level rise, higher temperatures, changing streamflows, increased risk of erosion, wildfires) and identifies thirteen impact pathways in which these effects could make the utility vulnerable. For example, reduced snowpack may change the alignment of seasonal stream flows with seasonal operations of hydroelectric projects and warmer temperatures may reduce transmission and distribution capacity for insulated equipment (for all 13 pathways, see page 16).

These impact pathways are divided between five utility functions of City Light’s operation and infrastructure:

  • Shoreline infrastructure - related to the properties City Light owns near Puget Sound and Duwamish Waterway which will be exposed to sea level rise.
  • Electricity demand - related to the expected changing demand for cooling and heating and the financial impacts for the utility.
  • Transmission and distribution - related to the 650 miles of transmission towers and lines owned by the utility and the risks to those lines from climate change.
  • Hydroelectric project operations - related to the five hydroelectric projects owned by the utility that provide 90% of the region's power.
  • Fish habitat restoration - related to the preexisting efforts of CIty Lights to protect fish habitat and mitigate adverse effects from hydroelectric projects.

Chapter 4 looks at each of the eight climate impacts and details City Light’s exposure, sensitivity, and adaptive capacity for any of the utility functions that are put at risk by that climate impact. For each, the plan also identifies near-term and long-term adaptation options. For example, a short term option for responding to increased temperatures that will influence demand for energy, the plan suggests evaluating co-benefits related to existing energy efficiency programs in the near-term, and developing a demand response program for reducing peak commercial load on hot days in the long-term.


Chapter 5 includes tables that lists each expected climate impact and assess how prepared the utility is to address those impacts. For each impact, it also assesses the potential financial cost, safety concerns, reliability concerns, and risks to environmental responsibility. For example, the risk of increased damage and transmission interruptions due to wildfire is viewed as creating high financial costs in both 2030 and 2015, high safety concerns for both time periods, and medium reliability concerns. The plan assess that the utility’s capacity to adapt is medium.

Publication Date: 2015

Related Organizations:

  • Seattle City Light
  • City of Seattle, Washington

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Resource Types:

  • Adaptation plan
  • Assessment

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