91视频

The city of Portland may choose to employ a design-build approach for an innovative $57 million project involving Willamette River water main crossings.

The Portland City Council on Thursday discussed the Water Bureau’s decision to pursue the alternative contracting method. A second reading and vote is scheduled for Dec. 16.

Bureau head Michael Stuhr believes that in this instance, design-build would more effectively reduce costs and claims than would the design-bid-build or construction manager-general contractor methods.

Though much of the project is not yet nailed down, a major aspect of it 鈥� which Stuhr called 鈥渧ery cool鈥� 鈥� would feature installation of a 4,000-foot-long line of 42-inch welded steel pipe through solid rock 80 feet under the Willamette river bottom, bypassing liquefiable soils and delivering a vital supply line to the heart of the city. Crews would employ horizontal drilling, an innovative method that would only minimally affect people and the environment, according to the Water Bureau.

But the effort would require a highly-qualified contractor and very specialized equipment. With a high level of technical knowledge needed, use of only one contract for design and construction would better ensure 鈥渆verybody’s on the same sheet of music鈥� before the city issues a notice to proceed, Stuhr told the Daily Journal of Commerce.

鈥淎ny contracting method can work in any instance,鈥� he said. 鈥淲e just think this is the best type of contracting, and the best value, for this project.鈥�

The city typically favors a competitive design-bid-build process, wherein qualified bidders are sought and the one that submits the lowest bid gets the project. Under design-build, the city would issue a request for proposals and then cull a short list of three to five firms. Those firms would then submit partial designs, price commitments and timelines. A contract would be offered based on 鈥渂est value.鈥�

鈥淥ne of the big benefits of using design-build is that it allows us to cut a lot of project time, so we can get a hardened crossing a lot sooner,鈥� Water Bureau chief engineer Teresa Elliott said.

The city maintains seven water main crossings of the Willamette River, which together provide water for 130,000 people on the river’s west side, or about 20 percent of city water users. The west side is also home to three hospitals and most of the area’s government agencies.

Elliott told the council that a Cascadia subduction zone earthquake 鈥� a major seismic event 鈥� is 15 percent likely in the next 50 years, and a 6.0-magnitude earthquake emanating from one of the area’s smaller faults is 33 percent likely. Plus, soil on both sides of the river is extremely liquefiable material, and the city’s existing pipes were installed when much less was known about seismic risk, she said.

The existing pipes rest in shallow trenches on the river floor, and (like most of the city’s bridges) aren’t expected to withstand a major earthquake.

鈥淲e desperately need to be able to provide water on the west side of the city,鈥� Stuhr told the council on Thursday. 鈥淭his project is extremely important.鈥�

Of the three possible alignments shown to council, the bureau’s preferred one runs slightly north of the Marquam Bridge on the east side of the river. Until a design-build team is selected, specific terminus points 鈥� and affected properties 鈥� won’t be known.

Of the proposed $57 million project budget, $40 million would go to the design-build contractor, $4 million would go toward consulting, and the remainder would be spent internally on land acquisitions, easements, permits and staffing.

The bureau expects to appear before the City Council sometime in 2017 after agreeing with a design-build team on a final project price. The project is expected to conclude by 2019.

Most of Portland’s water originates in the Bull Run watershed, though some is groundwater. It’s stored in reservoirs at Mount Tabor and Washington parks.