The First Big Pipe

Environmental Services completed the Columbia Slough Big Pipe in 2000. The 3.5-mile long conduit extends from Northeast 13th Avenue to the Columbia Boulevard Wastewater Treatment Plant and prevents about 300 million gallons of combined sewage from overflowing into the Columbia Slough each year.

Treatment Plant Improvements

Columbia Slough projects included several significant additions to the Columbia Boulevard Wastewater Treatment Plant to accommodate the added flows from the Big Pipe.

• A new pump station to pump water from the Big Pipe to the treatment plant.

• New primary treatment tanks. The old tanks now handle wet weather flow.

• A second outfall pipe to carry treated water to the Columbia River.

• A facility to remove disinfectant from treated water before discharge to the river.

The Columbia Slough projects reduce combined sewer overflows (CSOs) to the slough by 99%.