Work continues on West Side Combined Sewer Overflow project

Nestled away in Northwest Portland's Industrial District, amidst warehouses and factories, work continues to progress on the Nicolai Shaft portion of the West Side Combined Sewer Overflow project.

"When the project is completed no one will even know that it is there," said Paul Gribbon, program manager for the West Side CSO program and an employee with the city of Portland's Bureau of Environmental Services, the agency overseeing the project.

The Industrial District site, located next to the intersection of Northwest Nicolai Street and Front Avenue, may not be the most visible construction site in Portland, but certainly it is a major part of one of the most prominent projects to hit the Portland construction scene in recent years.

The West Side CSO is a project designed to reduce the volume of untreated combined sewage that overflows into the Willamette River during rainstorms. The project includes building an 18,500-foot pipeline on the west side of the Willamette River, and a large pump station on the east side of the river on Swan Island in North Portland.

The Swan Island pump station will eventually be the connecting point between the east and west side sections of the overall 20-year CSO project. The east side section is still in the design phase.

"This is the first big challenge since the Columbia Slough (pipeline) went into the ground," said Linc Mann, spokesman for the Bureau of Environmental Services.

The Columbia Slough pipeline refers to the recently completed $195 million project that helped to reduce sewer overflows into the Columbia Slough by 99 percent. The Columbia Slough Consolidation Conduit, a major portion of the project, was completed in October.

Using tunnel digging equipment referred to as "clam diggers," soil is removed from the Nicolai Shaft and dump trucks haul it away. Work is well underway at the site.

The Nicolai Shaft site joins several other ongoing projects that make up the $293 million West Side CSO project. Work is also underway at the Upshur Shaft on the west side of the Willamette River, and at the Confluent Shaft and Swan Island pump station, both located on Swan Island.

"We're thrilled with the way things are going," Mann said. "We haven't encountered any major problems, and we are on budget. Things are going great."

The Nicolai Shaft, along with four other shafts, is being constructed along the course of the West Side Big Pipe, which will be four miles long and 14 feet in diameter. The tunnel will begin at Southwest Clay Avenue, run under Waterfront Park and cross beneath the Willamette River to connect with the new pump station on Swan Island.

The shafts will eventually connect sewer pipes to the tunnel and in the future allow for maintenance access. Construction on the Clay and Ankeny shafts will begin later this year.

The Nicolai Shaft will serve as the starting point for two tunnel- boring machines: one will travel north and the other south from the Northwest Portland location. The tunnel-boring machines are being specially manufactured in Germany for this project, and will arrive in July.

The general contractor for the project is a joint venture between two companies Impregilo and S.A. Healy. Impregilo is an Italian firm with extensive mining experience, while S.A. Healy, Impregilo's Chicago-based sister company, has extensive underground construction experience.

"There's only a handful of firms that can do this kind of work in the world," Mann said.

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