Snohomish, King, and Pierce Counties working together to be earthquake ready.
The Puget Sound area is highly susceptible to seismic events that could cause significant damage to the regional drinking water supply and threaten the health, safety, and economic conditions of millions of people in Washington state. Water utilities are vulnerable to earthquakes because of their extensive network of pipelines, pump stations, tanks, and treatment facilities.
What are the earthquake risks to Puget Sound water systems?
Earthquakes could damage water systems in Snohomish, King, and Pierce Counties. A Cascadia Subduction Zone event would impact the entire region at once.
Cascadia Subduction Zone: Large zone that runs approximately 620 miles from the southern end of British Columbia to the northern portion of California. All utilities in the Puget Sound region would be impacted.
South Whidbey Island Fault Zone: Cuts diagonally through Puget Sound roughly from Port Townsend to North Bend and farther east. Everett Public Works, Seattle Public Utilities (serves Seattle, much of eastern King County and independent utilities), and the surrounding areas would be impacted.
Seattle Fault Zone: Runs west-to-east across Puget Sound, through south Seattle, and along the Interstate 90 corridor, ending near Fall City. Seattle Public Utilities would primarily be impacted.
Tacoma Fault Zone: Originates near Hood Canal and runs eastward, splitting into three strands. Pierce County utilities, including Tacoma Water, would primarily be impacted.
What are the likely impacts to water systems from a catastrophic seismic event?
- Major water supply outages. It may take up to two months for water suppliers in King, Snohomish, and Pierce to resume operations.
- Over 100 breaks or leaks on transmission pipelines that carry water from regional mountain sources.
- Up to 6,000 breaks or leaks on regional distribution pipelines that bring water from transmission lines to homes and businesses (2,000 pipe failures in Seattle alone).
- Loss of water and water pressure to fight fires, which are common after earthquakes. Large quantities of water needed to fight these fires is anticipated throughout the region.
- Poor drinking water quality from landslides in the watersheds where most of our drinking water comes from; disturbance of groundwater aquifers that supply drinking water wells; contaminants in water storage or pipes; and disruption of water treatment.
- Over $2 billion in state-wide economic losses resulting from damage to the Puget Sound water system.
