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| Environmental Services is constructing the Portsmouth Force Main as part of the city’s program to control combined sewer overflows (CSOs) to the Willamette River. The 66-inch diameter, three-mile-long pressurized pipe will carry combined stormwater and sewage collected by the West and East Side Big Pipes from the Swan Island CSO Pump Station to the existing Portsmouth Tunnel. Combined sewage will flow by gravity through the tunnel to the Columbia Boulevard Wastewater Treatment Plant. Force main construction is scheduled to be complete by the end of 2011.
Odor Control The force main project includes installing chemical injection equipment at the Swan Island Pump Station where the West Side and East Side Big Pipes meet. When conditions exist that could generate odors, the system will mix the chemical calcium nitrate with combined sewage to safely and effectively prevent odors.
The system will also control odors at the North Shaft site on N Willamette and N Carey boulevards, where the Portsmouth Force Main connects with the existing Portsmouth Tunnel. To ensure that there are no odor problems in the neighborhood, Environmental Services will construct a vent with a filter system at the North Shaft site. The vent will be flush with the surface of the ground. The odor control systems will be functional when the city activates the Portsmouth Force Main.
What You Will See The city will construct a 10 by 12-foot by 10-foot high control building with an adjacent 30-foot radio antenna pole or tower at the North Shaft location. The construction will include landscape improvements including planting more than a dozen trees.
The project also includes constructing two open face biofilters and a support building between N Columbia Court and Columbia Boulevard behind the trailhead at the city’s Columbia Boulevard Wastewater Treatment Plant. Each biofilter will cover about 1,200 square feet and be filled with organic media, primarily shredded wood.
At both locations, vines and vegetation growing on wire trellises will screen the control and support buildings.
If you have questions or would like more information, please contact Debbie Caselton at 503-823-2831 or debbie.caselton@portlandoregon.gov.
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