QUALITY

Setting water quality standards that are higher than those required by state and federal regulations, and enhancing treatment to improve taste.

SAFETY

Using a multi-barrier treatment system able to inactivate bacteria, viruses, protozoa, and other pathogens.

RELIABILITY

Making certain your water needs are met today, tomorrow, and beyond.

SAVINGS

Employing a design-build-operate approach saves time and money. Seattle Public Utilities and its customers saved nearly $50 million over a conventional design-bid-build procurement process for the Cedar Water Treatment Facility.

 

Seattle Public Utilities has a superior reputation for providing high-quality water to its customers. That tradition continues with the new Cedar Water Treatment Facility at the Lake Youngs Reservation. The new facility—designed, built, and operated by CH2M HILL, using its full-service delivery capabilities, including CH2M HILL Constructors, Inc. (CCI), and Operations Management International, Inc. (OMI)—relies on both time-tested and innovative techniques to supply high-quality drinking water. The time-tested techniques include watershed protection and chlorination, and the innovative techniques include ozonation and ultra-violet light disinfection. The facility provides 70 percent of all drinking water used by the Seattle metropolitan area, and can treat up to 180 million gallons of water per day.

How does Seattle Public Utilities provide high-quality water from the Cedar River?

A multi-barrier system is used to ensure that high-quality water is provided from the Cedar Water Treatment Facility to SPU's customers.

Watershed Protection

  1. Watershed Protection

    2. Watershed Protection The production of high-quality water starts at the source—the Cedar River Watershed.

    The watershed encompasses 90,500 acres of forest land. Below an elevation of 1,600 feet, most of the watershed consists of a porous glacial moraine, which is the rock, gravel, sand, and clay left by glaciers. The moraine provides natural filtration and adds some minerals to a portion of the water supply. The Cedar River Watershed is one of only six major drinking-water systems in the country that do not require filtration.

    Access to the watershed is restricted. There are no residential or commercial activities in the watershed and a team of watershed inspectors monitor the quality of the water. Cedar River water meets or surpases all federal standards for drinking water, and water samples are tested for a wide variety of substances every day.

  2. Raw Water Intake System

    3. Watershed ProtectionLake Youngs serves as a transmission reservoir for Cedar River water prior to its treatment. Like the watershed, access to Lake Youngs is restricted, minimizing the opportunity for introducing contaminants. Water quality within the lake can vary due to seasonal changes, such as algae growth and temperature stratification within the lake. To ensure that the best quality water is drawn from the lake, the raw water intake and pump station is located 400 feet offshore in water that is approximately 50 feet deep. In addition, the pump station has three inlet gates so water can be drawn at different depths to optimize water quality and treatment.

  3. Ozone Generation and Injection Facility

    4. Ozone Generation and Injection FacilityThe heart of the Cedar Water Treatment Facility is a coupled ozone/ultraviolet (UV) process. This two-step process both disinfects and improves taste and odor in a highly efficient and cost-effective manner. Water is pumped from Lake Youngs and piped to the ozone injection facility. Here liquid oxygen is transformed into a gas and a portion of the oxygen is converted to ozone. The ozone is transferred to the water by diffusing the gas into the flow within concrete injection chambers. The water must stay in contact with the ozone for aobut 10 to 15 minutes to complete the oxidation and disinfection processes that improve the taste and odor of the water and disinfect bacteria, viruses, and Giardia. Typically, this process involves construction of large, covered concrete structures; however, the Cedar Water Treatment Facility uses two existing 78-inch-diameter pipelines as the ozone contact chambers. Ozonation occurs as the water travels from the ozone injection facility to the UV disinfection facility. Using the existing pipelines resulted in a substantial reduction in costs and impacts on the site.

  4. Ultraviolet Light Disinfection Facility

    5. Ultraviolet Light Disinfection FacilityThe Cedar Treatment Facility is the largest facility in the United States to use UV technology to disinfect drinking water.

    The UV light disinfection facility exposes water to high intensity light to inactivate the pathogens. UV light is the primary disinfectant barrier against bacteria, virues, and Giardia. UV light has many benefits: it is effective against chlorine-resistant pathogens such as Cryptosporidium, limits the amount of chemicals needed for disinfection, and it is not known to produce any byproducts. Following UV disinfection, chlorine is added to the water to provide an additional and residual disinfection barrier throughout the water distribution system. Lime also is added to make the water less corrosive to building plumbing.

  5. Operations Building

    6. Operations BuildingThe operations building houses the main control room, analytical laboratory, offices, workroom, and lockers. The facility reflects the Northwest style of architecture that emerged during the 1960s. The building and site incorporate a number of sustainable design features, including recycled building materials and energy conservation. The operations building at the treatment facility has been designed by CH2M HILL to achieve a LEED silver rating. Click here to learn more about LEED and sustainable design at the Cedar Water Treatment Facility.

  6. Clearwells

    7. ClearwellsThe two circular concrete clearwells are used for short-term storage of treated water to meet fluctuations in demand.