Lake Oswego Interceptor Sewer and Near Shore Sewer Repairs and Upgrades

Completed in 2011 as a replacement for the City’s aging in-water sewers, the Lake Oswego Interceptor Sewer (LOIS) is a 42-inch buoyant pipeline, serving central and western portions of Lake Oswego. Decennial inspection of the pipeline interior, exterior, wave action tethers and anchors are recommended in the LOIS Operation and Maintenance Manual. This is the first assessment of the LOIS Pipeline since construction was completed in 2011.

Every three years, the Lake Oswego Corporation opens downstream gates and draws the lake down approximately 10 ft in order to allow lake front homeowners to complete maintenance activities and for lake bottom dredging. During the 2017 Oswego Lake Draw-down, deterioration of mortar joints was noted at in-water manholes upstream of the LOIS. Initial assessment of mortar spalling was conducted in 2020, including acoustic testing, but was inconclusive.

Inspection, assessment and cleaning of the Lake Oswego Interceptor Sewer, inspection and assessment of the Near Shore Sewer manholes, creation of a permitting summary memo, and creation of a proposed Capital Improvement Plan project with actionable recommendations to address deficiencies found during inspection.

Inspection and cleaning work are anticipated to be conducted in Fall/Winter 2021.