Lake Oswego Interceptor Sewer – Lake Down Contract

The Lake Down Contract involved the installation of over 7,300 feet of previously fused large-diameter high density polyethylene pipe at grade tolerances of 0.02 inches to connect the buoyant interceptor to the existing sewer system. Pile supports and caps and pipe cradles were welded to steel piles to support the new pipeline and a cathodic protection system was installed for protection. Lateral sewer pipes were connected to the lake-front residents and new manholes were installed along the pipeline. The City also took advantage of the lake draw down conditions and JWF’s management skills to add significant rehabilitation and replacement pipelines within the near-shore sewer system including individual residential laterals. This additional work was designed “on the fly” jointly between the engineer and JWF.

Another unique challenge of the project involved keeping the residential sewer system operational during construction. By installing over 30 individual temporary bypass pumping stations, JWF was able to successfully divert flows around the work area without any impacts to the residents. The bypass pumping system required 24-hour monitoring to ensure continued operations throughout construction. Special sound buffering was installed on the pumps which were carefully positioned to minimize noise intrusion to local homeowners.

Oswego Lake is private and used year-round for recreational pursuits by the lake-front homeowners. A critical component of the project involved limiting the duration of time the lake would be inaccessible by the owners. The lake was closed to users after Labor Day 2010 to begin the draw down process with full use to be restored by Memorial Day 2011. The refilling process began in February 2011, which required certain lower elevation tasks to be complete in order to meet the tight deadline. JWF was able to carefully sequence the work in over 15 different areas around the lake to meet the contract’s condensed 8 month time frame – typically this work would be spread out over 18 months.

Lake Oswego Interceptor Sewer - Lake Down Contract(2) Lake Oswego Interceptor Sewer - Lake Down Contract(1) Lake Oswego Interceptor Sewer - Lake Down Contract(3)