Lake Oswego Interceptor Sewer

The City of Lake Oswego needed an affordable, long-term solution to ensure reliable sewer service to its 37,000 residents. Its original 1960’s lake interceptor was undersized and corroding and would collapse in an earthquake. Brown and Caldwell’s creative engineering design replaced the aging two-mile underwater sewer pipeline beneath Lake Oswego with an unprecedented buoyant, flexible gravity sewer constructed of HDPE pipe. The project also included 1.5 miles of pile supported pipe, three miles of cured-in-place rehabilitated pipe and two new pumping stations. Completed on schedule, 10 percent under its $100 million budget, and with broad public support, the Lake Oswego Interceptor Sewer is expected to serve for a century or more. This is the first known buoyant gravity sewer pipeline in the world and serves roughly 75% of Lake Oswego households and businesses.