Willamette Water Supply Program Sets New Bar for Resiliency 

The Tualatin Valley Water District, City of Hillsboro and City of Beaverton serve approx­i­mately 400,000  Oregonians and expect demand in the region to grow by roughly 50% by 2040.

To meet this rising demand, the owners of the Willamette Water Supply Program (WWSP) are building a new water treatment plant that relies on multiple processes to generate high-quality drinking water. Engineered to withstand natural disasters like earthquakes, the water system will also help protect public health and speed recovery during emergencies.

CDM Smith facilitated the design process which included development of operating criteria to best treat variable Willamette River water quality . A critical step in the project was to design the plant to meet the “4Rs” (Resiliency, Reliability, Recovery, Redundancy). Natural hazards assessed during the design phase included water supply cont­a­m­i­na­tion, earthquakes, wildfires, volcanic eruptions, and flooding. During preliminary design CDM Smith collab­o­rated with the owners  and stake­hold­ers to develop tailored level-of-service goals  for multiple treatment and hazard scenarios from those that the owners previously developed Program-wide.

A resilient design is one that addresses and overcomes uncertainty. To that end, CDM Smith engineers and scientists held a two-week Hazard and Operability (HAZOP) Study including multiple workshops to identify “4R” provisions for each treatment plant process and mechanical system, reducing anticipated overall operational risks. 

Advanced water treatment tech­nolo­gies, like ozone and UV, will also ensure the plant meets or exceeds regulatory require­ments during normal operations. This will maximize flexibility in meeting water quality regulations following a regional natural disaster. 

Addi­tion­ally, design was completed in 3D, facil­i­tat­ing reviews and discussion of all aspects of resiliency as design progressed.

The water treatment plant will be constructed directly on bedrock, which increases the seismic resiliency of the  site. Significant drilling and blasting is required to construct the facility. Additional construction resiliency considerations include: 

• Critical process, instrumentation, electrical and HVAC equipment was required to obtain ASCE 7-16 Special Seismic Certification or equivalent prior to shop drawing approval and installation.
• Customized requirements for ‘shelf spares’ to be provided by vendors for particularly sensitive equipment to speed recovery efforts with dedicated storage space.

When the plant becomes operational, on-site diesel storage will be sufficient for operations at 50% plant capacity for up to five days, using standby generators. The plant will also benefit from in-situ redundancy of process treatment trains to maximize operational flexibility. This includes ballasted flocculation, filters and UV reactor trains equipped with significantly higher hydraulic capacity than is needed to meet design flow conditions. 

The Willamette Water Supply Program’s focus on resiliency helps raise the bar for water system design projects in the future. Reach out today for recommendations on incorporating a deeper level of resiliency to your future treatment plant projects.