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Outfall

Columbia Boulevard Wastewater Treatment Plant – Portland, Oregon

Customer:
Portland Bureau of Environmental Services

Location:
Portland, Oregon

Project Description
Manson Construction was a subcontractor to James W. Fowler Co. for the installation of a new 84-inch concrete covered steel pipeline outfall from the Columbia Boulevard Wastewater Treatment Plant to the Columbia River.

The project began on the south shore of the Oregon Slough where Fowler had constructed a connection to the in-water outfall line from the main treatment plant. Manson buried the pipeline in an underwater ditch for 1,500 feet across the Oregon Slough. The pipe then crossed overland to a dechlorination facility on Hayden Island in the Columbia River, and continued from the facility to the shore of the Columbia River. Fowler constructed the land portion of the Hayden Island line and Manson installed the in-river section.

The pipeline terminated with a 400-foot long diffuser section in the river. The pipe was laid in an excavated ditch with 2 feet of 3-inch bedding rock, rock backfill to the pipe spring line and 4 feet of native cover material placed over the top of the pipe. The in-water portion began work in August 1999 and was finished in November 1999.

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