The Willamette River Water Treatment Facility: a design/build project

From meadow to water in 28 months

Michael A. Stone, P.E.
City Engineer
City of Wilsonville, Oregon

The City of Wilsonville, Oregon, population 14,000, is located along Interstate 5 at the north end of the Willamette Valley approximately 12 miles south of Portland. Although the city lies on the banks of the Willamette River, it has historically obtained water from eight wells located in an underlying deep bed basalt aquifer with steadily declining water levels. With projected system demands matching production, a moratorium limiting the amount and rate of growth of new planning approvals was declared in January 1998, pending the successful determination and construction of a new long-term water supply source. Staff was directed to conduct an evaluation of available options and to report back to the City Council with its findings. Three options were evaluated:

  • Build additional wells. Due to the city's location within a "groundwater sensitive area" as established by the State of Oregon, and local residential/agricultural objections, securing the necessary permits for additional wells was not possible.

  • Connect to Portland's "Bull Run" surface water system. Due to the high construction costs, the need to traverse several neighboring communities with large diameter piping, and the uncertainty of a long-term water availability guarantee, this option was similarly eliminated.

  • Construct a new water treatment facility on the Willamette River. Given the "treatability" of the Willamette River, as confirmed by water quality studies extending back approximately ten years and recent pilot testing, the City Council determined that the Willamette River option best met its long-term water supply needs. Staff was directed to look to the construction of a state-of-the-art multi-barrier water treatment facility producing water that would exceed EPA/State of Oregon drinking water standards. This alternative was additionally attractive due to the pre-existing (1973) water rights that the city held with its partner, the Tualatin Valley Water District (TVWD).
In 1999 an election was held in which the citizens of Wilsonville were asked to affirm the City Council's decision to choose the Willamette River as the city's long-term water supply source and to approve $25 million in revenue bonds to finance construction. With the successful passage of the measure, the city's revenue bond proceeds were combined with funding from TVWD for construction of a $43 million facility. Construction commenced in July 2000.

Given the state-mandated limitations on the length of the moratorium, liquidated damages ranging up to $12,500 per day would be assessed for failure to complete the contract within the time specified.

Project Description
With the limited availability of sufficiently sized parcels adjacent to the Willamette River, the city purchased a 31-acre site located between a concrete plant and a residential area very early in the planning process. Drawing from the results of pilot studies, a general description of the facility and anticipated component sizing were proposed:

  • 15 million gallon-per-day (mgd) initial capacity.
  • Submerged 120 mgd intake screens.
  • Raw water pump station with pumping expansions to 120 mgd.
  • Chemical mixing facilities.
  • Ballasted coagulation (ACTIFLO).
  • Intermediate ozonation.
  • Gravity filtration with granular activated carbon.
  • 2.5 million gallons of finished water storage.
  • High-service pump station with pumping expansions to 120 mgd.
  • Gravity thickening of sludge with disposal in an approved landfill.
  • Chemical storage and metering.
  • Administration building with certified laboratory.
  • Access road, pedestrian path, bridge, public park, landscaped water pools, educational displays, pedestrian trails and a river overlook structure.
Why Design/Build?
Schedule was the key motivator for the use of design/build. With "conventional" methodology, the estimated completion timeline exceeded the city's immediate water needs and the state-mandated limitations on the length of the planning moratorium.

Selection Process
Much like the decision to implement the design/build approach to construction, the selection process for the design/build contractor was accomplished under emergency conditions. As a means to determine the most qualified "team" to serve as the design/builder, the city and TVWD issued a Request for Qualifications (RFQ). A Technical Review Committee, consisting of representatives from the city, TVWD and CH2M-Hill, then reviewed the RFQ materials based on the following disciplines:

  • Organization of design/build team.
  • Overall experience.
  • Permitting experience.
  • Design/build experience.
  • Financial capacity.
  • Comments on proposed project.
Based on the outcome of the review and scoring process, the committee recommended that MWH Inc. and Black & Veatch be invited to participate in an oral interview process. MWH was determined to be the most competent and compatible firm to complete the facility. The city and TVWD chose CH2M-Hill to continue to act as the owner's representative during the construction and US Filter Operating Services (USFOS) to operate the facility.

Design/Build Services
The design/builder was tasked with completing the design, permitting and construction within 28 months from notice to proceed. Partial design drawings were prepared for most key components of the facility. A cooperative relationship with the construction contractors allowed construction to begin based on 30 percent design, allowing the design/builder maximum flexibility to reduce construction time.

The design/builder was successful in obtaining and coordinating permits and approvals from a number of agencies within an eight-month window: Oregon Division of State Lands, Oregon Water Resources Department, Oregon Health Department, Oregon Department of Environmental Quality, U.S. Department of Fish and Wildlife/National Marine Fisheries Service, U.S. Army Corps of Engineers, and Wilsonville's Land Use and Architectural Design offices.

Although there have been some relatively small issues relating to the "just in time" nature of design/build, the plant became operational on April 29, 2002 within the allocated construction time. Since that time there have no production stoppages due to issues related to the plant design, construction or operation.

Michael A. Stone can be reached at (503) 570-1564 or at