Tualatin Valley Water District (TVWD) customers in Cedar Mill, Bethany and Cedar Hills will start receiving drinking water from the Willamette River this winter.

The $1.6 billion Willamette Water Supply System (WWSS) will replace the water TVWD has purchased from the Portland Water Bureau for decades. The district serves about 166,000 residents across Washington County, according to Willamette Week.

Water will be drawn from the Willamette River near Wilsonville, treated at a new facility in Sherwood and delivered through 30 miles of earthquake-resistant pipeline, according to TVWD's project page. The treatment process runs through an intake facility, sediment removal, ozone treatment, filtration with granular activated carbon and sand, UV light disinfection and chlorine disinfection.

The system is a partnership between TVWD and the cities of Hillsboro and Beaverton. It can serve 350,000 Washington County residents and is built to withstand a Cascadia Subduction Zone earthquake, according to Cedar Mill News.

TVWD spokesperson Justin Dyke told Willamette Week on Wednesday, Sept. 2 that the move is not about dissatisfaction with Portland's water or service. "It's because as a water utility in Washington County on the west side of the metro, we have long had a goal of having our own water supply that we can have an ownership stake in," Dyke said.

The district plans a phased rollout, with some customers receiving the new supply before others. TVWD has not released a neighborhood-level schedule.

Before the switch, TVWD said it is flushing and disinfecting all 30 miles of new pipeline, testing every component and conducting a required 30-day performance test at the Sherwood treatment plant.

Residents with questions can talk to TVWD staff at two upcoming events. The district will have a booth at the Cedar Mill Farmers Market on Sept. 26, from 9 a.m. to 2 p.m. at the corner of NW Cornell and Murray roads. TVWD will also be at the Cedar Mill Cider Festival the same day, from noon to 4 p.m. at the John Quincy Adams Young House, 12050 NW Cornell Rd.