The East Side and West Side tunnels meet at the Swan Island CSO Pump Station. As Portland’s largest pump station, it can pump up to 220 million gallons a day through the Peninsular Force Main to the treatment plant. Tunneling ended in October 2010, and the city started using the East Side Big Pipe in fall 2011. The nearly 6-mile-long tunnel is 22 feet in diameter. The 14-foot-diameter, 3.5-mile tunnel extends from SW Clay Street and SW Naito Parkway north to the Swan Island CSO Pump Station.Įnvironmental Services finished work on the East Side Big Pipe project, the largest sewer construction project in Portland history, in 2011. It prevents about 300 million gallons of combined sewage from overflowing into the Columbia Slough each year.Įnvironmental Services completed construction on the West Side Big Pipe in 2006. The Big PipesĮnvironmental Services completed the Columbia Slough Big Pipe in 2000. This 3.5-mile-long tunnel extends from NE 13th Avenue to the Columbia Boulevard Wastewater Treatment Plant.
The project included new storm sewers and a pipeline to convey stormwater to a 26-acre constructed wetland called Ramsey Lake for treatment. The largest sewer separation project was in the St. Sewer SeparationĮnvironmental Services constructed new storm sewers in some areas of west, north, and southeast Portland.
Stormwater SumpsĪbout 3,000 stormwater sumps and sedimentation manholes in combined sewer areas throughout north, east, and southeast Portland collect street runoff, trap sediment and pollutants, and allow water to soak into the ground. Stream DiversionĮnvironmental Services constructed a pipeline to carry clean stream water, including Tanner Creek, from Portland’s west hills directly to the Willamette River and remove that water from the combined sewer. The largest of these initiatives was the Downspout Disconnection Program. The City partnered with residents of neighborhoods east of the Willamette River where soils and topography make it safe to disconnect roof drains from combined sewers and redirect the flow to yards or gardens. At the end of the program, more than 56,000 disconnections were keeping 1.2 billion gallons of stormwater per year out of combined sewers. The Beginning: Cornerstone Projects Divert Stormwater from Sewersįirst were the “Cornerstone Projects.” These were projects to keep stormwater out of the combined sewer system. Each year, these projects continue to keep millions of gallons of stormwater out of sewers.
The East Side, West Side, and Columbia Slough Big Pipes are probably the most well-known parts of Portland’s program to control CSOs. The overall program, however, was made up of several projects and initiatives around Portland. The Big Pipe Project: More Than Just Pipes The number of overflows are dramatically lower: To eliminate 100 percent of CSOs, the project cost would have doubled without a significant increase in improving river health.īefore Big Pipes, an average of 50 Willamette River overflows occurred each year, sometimes lasting for days. Today, an average of four overflows occur each rainy season and one every third summer. Fast FactsĮnvironmental Services explored several options for controlling combined sewer overflows (CSOs). The option that eliminated most, but not all overflows, was the most cost-effective way to protect our rivers while also recognizing the impact of sewer rates on our customers.Ĭompleted in 2011, the Big Pipe Project took a generation to build – 20 years – and $1.4 billion.ĬSOs have been nearly eliminated, dropping by 94 percent to the Willamette and 99 percent to the slough, significantly improving river health. The Big Pipe Project is shorthand for an ambitious set of actions and improvements that together eliminated most combined sewer overflows, or CSOs, to the Willamette River and Columbia Slough. Before the Big Pipes, it didn’t take much rain to cause an overflow-only about one-tenth of an inch.
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