Civil Engineering Reference
In-Depth Information
Project:
Cedar Water Treatment Facility
Owner:
Seattle Public Utilities, Washington
Design-Build (DB) Entity:
CH2M HILL
Completion Date:
July 2004
Description of Project
Seattle Public Utilities (SPU) needed to provide advanced treatment to meet dis-
infection requirements for a surface water supply. A new water treatment plant
(WTP) was needed. SPU selected CH2M HILL as the prime contractor to design,
build, and operate a new $79 million, 180-mgd (681-ML/d) water treatment facil-
ity. CH2M HILL also provides operations and maintenance (O&M) services under
a 25-year contract. The full design-build-operate (DBO) project value was $109
million.
The new facility has two independent treatment trains, each providing (1)
ozone generation, injection, contact, residual quenching, and destruction systems,
and (2) ultraviolet (UV) disinfection. The UV disinfection system consists of 13 UV
reactors: 6 for each process train plus 1 spare. The facility is the largest UV drink-
ing water facility in the world, providing regulator-credited 3.0-log
Cryptosporidium
disinfection.
The project included construction of a new intake and raw water pump station.
One of the innovations that was gained through the DB delivery method was to
reline existing transmission pipelines and convert them into highly efficient ozone
contactors. This approach avoided costs and site impacts associated with construct-
ing conventional ozone contactors. Treatment also includes chlorination and lime
addition for corrosion control. Other facility components include two 10-mil-gal
(38-ML) clearwells for treated water storage and flow metering and control stations
designed for an ultimate capacity of 275 mgd (1,040 ML/d).
Why the Owner Chose Design-Build
Seattle Public Utilities wanted to take advantage of the innovations and cost savings
inherent in design-build delivery. DBO delivery saved SPU $50 million when com-
pared with traditional DBB delivery.
Success Outcomes
One of the unique requirements of the project was that it had to meet LEED™
criteria, eventually receiving a rating of “gold.” LEED™ is a building rating system
developed by the US Green Building Council to promote design of facilities that are
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