Seattle Public Utilities (SPU) is one of only a few major metropolitan water utilities in the United States that doesn't filter all its water. While the city obtains a majority of its water supply from a pristine, 90,500 acre watershed, changing water regulations required SPUto consider either installing a $200 million filtration system or looking into alternatives to filtering their water.

Historically, SPU's water was treated only with chlorine, corrosion control chemicals, and fluoride. Having faced a similar challenge in the past, SPU turned to a design-build-operate (DBO) approach to help them manage the water treatment for the Cedar River Watershed water.

Thanks to a partnership with CH2M HILL and its operations and maintenance business unit, CH2M HILL OMI, Seattle-area residents now receive even higher quality drinking water that has been treated with state-of-the-art ozonation and ultraviolet (UV) treatment. The new Cedar Water Treatment Facility is among the first - and is the largest facility in the U.S. - to combine the technologies to treat drinking water, ensuring that SPU's customers continue to receive high-quality water for the best price. The new facility provides enhanced treatment that exceeds current and future water quality standards and improves taste and odor. CH2M HILL's contracted scope included design, permitting, material and equipment procurement, construction, onsite inspection, start-up, commissioning, and operations (for up to 25 years) of the facility.

As the first water treatment plant in the nation to employ UV technology on a large scale, the facility treats 180 mgd (million gallons of water per day). The UV and ozone treatments, combined with watershed protection, eliminate intensive chemical use and costly filtration. CH2M HILL OMI will operate the facility for 15 years with the option to extend the contract up to an additional 10 years. As Seattle's needs grow, the facility is expandable to 275 mgd.

The automated plant operates with less staff, yet reliably provides 70 percent of Seattle's drinking water. With the innovative design-build-operate (DBO) process, the CH2M HILL family of companies will save the city about $50 million over the estimated cost of a conventional design-bid-build-city-operate procurement.

CH2M HILL's design of the Cedar Water Treatment Facility was based on "least impact" to the pristine environment of the Lake Youngs Reservation. Impacts to wetlands were avoided by using a dispersed site layout, minimizing building footprints, reusing existing infrastructure, and upgrading wetland habitat through native plantings. Approximately 85 percent of the waste generated during construction was recycled. In January 2006 the CH2M HILL designed and constructed operations building earned the LEED Gold certification. LEED is a building rating system developed by the U.S. Green Building Council.

CH2M HILL was responsible for ensuring that the Cedar Water Treatment Facility met high industry standards and addressed Seattle Public Utilities' (SPU) and its own quality objectives through all stages of development, permitting, construction, testing, startup, and operation. Quality in every phase of the Cedar Water Treatment Facility project was essential in the decision to allow SPU to build this new drinking water plant using a DBO delivery process. State and federal regulatory agencies had to be assured that the water flowing into the community's homes and businesses would be unquestionably healthy, comply with current and anticipated drinking water regulations, and minimize adverse impacts on surrounding sensitive areas, including wetlands.

A comprehensive quality program was developed for the project, with an independent quality manager assigned to oversee all quality activities. Since CH2M HILL OMI's operations began, we have met 100% of state and federal requirements and 99.7% of SPU's even more stringent water quality standards.

The team defined outcomes of minimum environmental impact, permitability, water quality performance, and constructability, then integrated design and construction to achieve the outcomes. CH2M HILL designed a 400-foot-long intake system to draw water from Lake Youngs at various depths up to 50 feet to optimize raw water quality and minimize treatment costs. To minimize impact on the reservoir's potable water during construction, the designers and constructors created an innovative design that allowed most of the intake fabrication to take place on shore. Minimizing the project footprint, beyond conventional siting methods, became an integral part of the design. To achieve the tightest footprint, the design re-used as many existing facilities as possible, and also incorporated many vertical features. For instance, normally ozone treatment requires large covered concrete structures for contact time. The innovative design converted two existing 78-inch-diameter, 2,500-foot-long pipelines into the ozone contact system. This reduced environmental impact, streamlined permitting, and cut project costs. CH2M HILL also partnered with the UV vendors to design the first vertical equipment configuration.