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Water and Wastewater Plant Directory
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Seattle, Washington, USA
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Cedar Water Treatment Facility
700 Fifth Avenue
Seattle, Washington, 98124-4018
USA
Contact Information:
Contact: Frank McDonald
Email:
franke.mcdonald@seattle.gov
Telephone: (206) 386-1838
Fax:
Plant Operation: Municipal
Processing: Water
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Web site:
http://projects.ch2m.com/cedarps/
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Plant/Process Description:
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.
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.
Lake 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.
The 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.
The 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.
The 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.
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Owner:
Seatle Public Utilities
Web site:
http://www.seattle.gov/util/services/
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Operating Company:
CH2M Hill
Web site:
http://www.ch2m.com
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Directions:
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Disclaimer:
Water and Wastewater.com provides the information on
this page for reference purposes only. We do not certify
the accuracy of the information provided by third-party
individuals for this listing.
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