A 1991 agreement between the City of Portland and the State of Oregon to dramatically reduce combined sewer overflows (CSOs) led to Portland's Big Pipe Project. The project, part of a related series of Portland CSO projects completed in late 2011 at a cost of $1.44 billion, separates the city's sanitary sewer lines from storm-water inputs that sometimes overwhelmed the combined system during heavy rains. When that occurred, some of the raw sewage in the system flowed into the river instead of into the city's wastewater treatment plant. The Big Pipe project and related work reduces CSO volume on the lower river by about 94 percent.
A 199,1 agreement between the City of Portland and the State of Oregon to dramatically redu?ce combined sewer overflows (CSOs) led to Portland's Big Pipe Project. The project, part of a related s.eries of Portland CSO projects completed in late 2011 at a cost of $1.44 billion, separates the city's sanitary sewer lines from storm-water inputs that sometimes overwhelmed th:e combined system during heavy rains. When that occurred, some of the raw sewage in the system flowed into the rive!r instead of into the city's wastewater treatment plant. The Big Pipe project and related work reduces CSO volume on the lower river by about 94 percent.