State of the Art Design Mitigates Seismic Risks for Brightwater Treatment Plant

The Brightwater Treatment Plant (Brightwater) is a new 50.8 million gallon per day (mgd) peak month flow wastewater treatment facility owned and operated by King County. Brightwater utilizes conventional and chemically enhanced primary clarification and membrane bioreactor (MBR) processes for liquids treatment. Solids handling consists of thickening, anaerobic digestion, and dewatering. Foul air is treated through multi-stage odor control systems.Brightwater is located in a seismically active region influenced by the Cascadia Subduction Zone, and the South Whidbey Island Fault. Since Brightwater is a green field facility, King County had the unique opportunity to configure Brightwater to mitigate the risks posed by seismic activity. This paper profiles the Brightwater seismic environment, describes site-specific studies performed to evaluate the possible presence of active faults at the site, and discusses innovative features incorporated into the design to reduce potential damage from seismic events.