Award of Merit Civil Works/Infrastructure

Photo courtesy of Brown + Caldwell
Brown + Caldwell was the engineer on the project.

Build a sewer in a lake? Make it buoyant? Will it work? Officials of the City of Lake Oswego, Ore., and their consultant asked and answered these and many other questions while designing and constructing what project officials say is the world's first-known buoyant gravity sewer. The $95-million project was completed ahead of schedule after a 10-year planning, design and construction process. Its centerpiece is a buoyant gravity high-density polyethylene sewer, held to proper grade beneath the lake surface by 428 ground anchors and tethers. A serpentine alignment provides thermal expansion loops to maintain grade despite wide-ranging water temperature.

Key Players

Owner: City of Lake Oswego, Ore.

General Contractor: Advanced American Construction, Portland, Ore.; James W. Fowler Co., Dallas, Ore.

Construction Management/Civil, Structural Engineer: Brown + Caldwell, Portland. Ore.

Submitted by:

Brown + Caldwell