Tualatin Valley Water District (TVWD) and the City of Hillsboro are jointly developing the Willamette Water Supply System to serve their customers’ future drinking water needs. The City of Beaverton is also considering joining the partnership. The new system will draw water from the mid-Willamette River at Wilsonville and, once treated, deliver it to TVWD and City of Hillsboro customers. The Willamette Water Supply Program is being funded by TVWD and City of Hillsboro ratepayers.
Plant Location and Capacity
Construction of a new, seismically secure water treatment plant (WTP) is essential to the new water system. It will be located in the Tonquin Employment Area, currently in unincorporated Washington County, near the intersection of SW 124th Avenue and Tualatin-Sherwood Road. The WTP will be sited within the southern portion of the nearly 100-acre parcel that is part of a larger planned industrial development. The WTP will occupy about 20 acres. Approximately 20 additional acres are earmarked for roadway improvements, setbacks and habitat preservation. The site meets several important criteria including that it is geologically stable, is slated for future development, is of adequate size, and allows opportunities to conserve wetland and upland habitat. The stable soils on this site mean the WTP will have superior seismic resiliency and will be better able to withstand a catastrophic natural disaster.
The WTP site is within the Urban Growth Boundary, is zoned industrial, and will eventually be part of the City of Sherwood (see map). The new WTP will initially produce up to 60 million gallons of water per day (mgd) but will be designed for a maximum of 120 mgd.
Water Treatment Process
The new WTP will be designed to utilize similar processes as the existing Willamette River Water Treatment Plant (WRWTP), which has been delivering safe and reliable water to Wilsonville and Sherwood residents since April 2002. The WRWTP utilizes multiple treatment steps to meet drinking water standards. Steps include enhanced coagulation sedimentation, ozonation, granulated activated carbon filtration, sand filtration, and secondary chlorine disinfection (learn more here).