CentralNotice From Wikipedia, the free encyclopedia Jump to: navigation , search Looking down the main construction shaft to the East Side Big Pipe during construction The East Side Big Pipe is a large sewer line and tunnel in Portland in the U.S. state of Oregon . It is part of a combined sewer system of pipes, sumps, drains, pumps, and other infrastructure that transports sewage and stormwater run-off to the city's Columbia Boulevard Wastewater Treatment Plant. The East Side Big Pipe project, begun in 2006 and finished in 2011, was the largest of a 20-year series of projects designed to nearly eliminate combined sewer overflows (CSO)s into the Willamette River and the Columbia Slough . The combined projects were completed on time, and they reduced CSOs into the river by 94 percent and into the slough by more than 99 percent. 1 History 2 Technical details ...