Future Water Source Projects

Tualatin Basin Water Supply Project 

Water resources agencies in Washington County are working to ensure clean, safe, and reliable water supplies for the environment and needs of a growing community. They have formed a water supply partnership to finance and plan for future water supplies from the Tualatin River. The Tualatin Basin Water Supply Project partners include: 

The project also operates in partnership with the U.S. Bureau of Reclamation (USBR). The USBR is the builder and owner of the Scoggins Dam and Hagg Lake. 

Beaverton's Involvement 

Beaverton’s current level of participation in the Tualatin Basin Water Supply Project is 1,763 acre-feet (574 million gallons of storage) or 3.33% of the total nominal 52,900-acre-feet of new raw water storage that would be created in an expanded Scoggins Dam with a 40-foot dam raise. The Scoggins Reservoir expansion would nearly double the current volume of the reservoir totaling 60,640 acre-feet (usable volume 53,640 acre-feet). 

Beaverton currently owns a right to use up to 4,000 acre-feet in Hagg Lake and 4,300 acre-feet in Barney Reservoir for summertime water supply. During the summer, water in the two reservoirs is released into the Tualatin River as needed to meet the city’s potable (drinking) water demand. The City of Beaverton acquired rights to its 4,000 acre-feet of water in Scoggins Reservoir (Hagg Lake), referred to as the Tualatin Project, under two separate contracts with the USBR.

Evaluating Alternative Water Supply Options 

In June 2001, the Beaverton City Council authorized signing of a funding agreement to participate in a Water Supply Feasibility Study of the Tualatin River basin, the first phase in the Tualatin Basin Water Supply Project. Completed in 2004, the study evaluated alternatives for reliable, safe, and sustainable water supply options to meet the long‐term Tualatin River stream flow, agricultural irrigation, and municipal and industrial water needs in Washington County to the year 2050. 

From 2005, an alternatives analysis examined the various supply options and two were presented in an environmental impact statement. The first alternative is a 40‐foot dam raise of Scoggins Dam (at Hagg Lake) with a large‐diameter raw water pipeline pumpback from the Tualatin River to refill Hagg Lake each year. The second alternative is a multiple source option that includes a 25‐foot raise of Scoggins Dam with a large‐diameter raw water pipeline pumpback, and expansion of the Willamette River Water Treatment Plant located in Wilsonville.

Aerial view of Hagg Lake and Scoggins Dam on a partly cloudy day.
Water treatment facility near Hagg Lake.