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2001 Awards

January 17, 2002

National Gold Award: Tolt Treatment Facility

Category: Water and Wastewater
Engineer: Camp Dresser & McKee
General Contractors: Dillingham Construction
Architects: Mahlum Architects
Owner: Seattle Public Utilities
Description: The city established an innovative public/private partnership for development of its first water filtration plant, the 120-million-gallon per day Tolt River facility. Tolt’s pioneering design allows continuous operation through periods of high source water turbidity, and provides for long-term compliance with anticipated regulations. Turbidity in the Tolt Reservoir can increase substantially during late fall/early winter storms, which often resulted in the supply being taken out of service for days or weeks.
 
Camp Dresser managed the design/build team during development and design phases, and was responsible for demonstrating compliance with Seattle Public Utilities as well as state and local reviewing authorities. CDM also produced a document package that included 430 drawings and three volumes of specifications.
 
In addition to high-rate filtration and combined ozone contact and flocculation, other technical innovations at the facility include hydraulic flocculation, which provides an appropriate combination of mixing energy and time without added mechanical energy. Pumped injection flash mixing uses water jets supplied by the plant utility water pumps, avoiding the issues of penetrating an ozone-containing basin with rotating equipment.
 
The facility is the Northwest’s largest water filtration plant and the largest ozone disinfection facility. Design was completed in just over nine months, including parallel pilot testing program. “What they incorporated into the design minimized operation costs,” said juror Alan Coburn.


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