Gig Harbor WWTP Outfall Extension

Project Description

This project for the City of Gig Harbor consists of replacement of the undersized existing 1,600 feet 10-inch outfall pipe with 9,228 feet of 24-inch high density polyethylene (HDPE) outfall pipe. This improvement allows treated effluent wastewater to travel from the Treatment Plant to Colvos Passage of Puget Sound. The new outfall pipeline increases the capacity of the Wastewater Treatment Plant and improves water quality in the Harbor.

The new outfall pipe was connected to the pump station located at the end of the harbor, extend 5,808 feet to the Coast Guard owned sand spit where it was horizontal directional drilled 711 feet by AAC’s subcontractor Mears Drilling. Once the pipe was drilled under the spit, AAC deployed the final 2709 feet of pipe into the Colvos Passage of Puget Sound. A 550 foot diffuser section is located at the end of the outfall at a depth of 200 feet. Mobilization began in late May 2010, with project completion May of 2011.

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