Buoyant Interceptor Inspection Featured in Pacific Northwest Trenchless Review

The first known buoyant gravity sewer in the world, the Lake Oswego Interceptor Sewer, needed its first routine condition assessment after a decade of service. Because this innovative infrastructure is fully submerged beneath Oswego Lake, access points for a standard inspection were limited. To avoid draining the lake or disrupting service, the tailored approach combined trenchless inspection technologies, engineer-diver-led exterior assessments, and carefully coordinated barge and caisson access operations on the lake. The critical data gathered from the assessment informed a five-part capital improvement plan to guide future maintenance.

Trenchless technologist Brendan O’Sullivan breaks down this assessment approach on page 29 of the Pacific Northwest Trenchless Review by the North American Society for Trenchless Technology.