What easily could have been a run-of-the-mill sewer pipeline replacement project in Oregon went from underground to underwater—creating what participants say will be the world’s first buoyant gravity line.
Now under construction, the Lake Oswego interceptor sewer boasts 17,000 ft of wastewater-carrying pipe and another 12,000 ft of attached air-filled buoyant pipe. Replacing an existing submerged concrete pile-supported pipeline built in 1963, the new system will hook to the city’s current system on both sides of the lake. It will serve 10,000 connections, about 74% of the city’s customers in the state’s Willamette Valley area. The $85-million project will involve an additional $52 million for in-lake work.