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The city of Portland will spend $4 million to repair or replace 8,000 linear feet of failing sewer pipe in its Northwest section.

The Portland City Council on Wednesday authorized competitive bidding to furnish materials and labor for the Far North Nicolai Sewer Rehabilitation Project.

Murray and Associates along with the Bureau of Environmental Services prepared plans for the project, which is part of a to modernize sewer infrastructure. Construction is slated to start in the spring and last about 18 months. Funding will come from the Sewer System Operating Fund.

The project area falls roughly between Northwest Nicolai Street and Thurman Street and between Northwest 21st and 28th avenues. The densely populated neighborhood has a mix of residences and small businesses. Pipes in this part of Portland are too small to meet current demand, and buildings there have historically been susceptible to basement backups, BES spokesman Linc Mann said.

Most of the pipes targeted for replacement are around 80 years old. In many cases, 12-inch pipe will be replaced by 36-inch pipe.

Northwest Vaughn Street, between Nicolai and Thurman streets, is a heavily-traveled road off of Interstate 405. To minimize traffic impacts there, crews will work nights digging up intersections between Northwest 23rd and 27th avenues. Initially, more work was planned on Northwest Vaughn, but after a redesign – in response to public concern about adverse effects – the bulk of construction shifted three blocks north.

The job will include a combination of open-trench excavation and cured-in-place pipelining, a trenchless repair method that takes several days per section and requires crews to work around the clock. To perform work outside the 7 a.m. to 4 p.m. period mandated by city code, a noise ordinance variance was acquired.

About 40 businesses will be affected by the project, according to BES.