Reducing CSOs: Other Ways the City is Keeping the Willamette Clean

Since the city of Portland and the State of Oregon made a pact back in 1991 to significantly control combined sewer overflows, several city projects have reduced CSOs to the Willamette River by 53 percent.

• The city's Downspout Disconnection Program has resulted in diverting more than 700 million gallons of rainwater from the combined sewer system. So far, 40,000 homeowners have disconnected their downspouts, allowing their roof water to drain into their gardens and lawns.
  
• In a few Portland neighborhoods, the city has installed new pipes to separate stormwater from sewage and remove stormwater runoff from the combined sewer system.
  
• Decades ago, Tanner Creek in west Portland was rerouted into the city's sewer system to facilitate development. This relatively clean runoff contributes to CSOs during heavy rains. The city has installed a separate pipeline for the creek to flow directly to the river.
  
• The city completed the $70 million Columbia Slough Consolidation Conduit in December 2000, which captures 99 percent of the sewage and stormwater that once overflowed into the Columbia Slough (a tributary to the Willamette River) when it rains. Now, the overflow is discharged into a new tunnel and routed to the Columbia Boulevard Wastewater Treatment Plant.

Useful Sources:

• Information on group presentations: Diana Hinton, Environmental Services, City of Portland, (503) 823-2827

Project Team:

Owner: Environmental Services, City of Portland
General Contractor: Impregilo/Healy Joint Venture, Portland, Ore.
Designer: Parsons Brinckerhoff, Portland, Ore.