While Portland’s wastewater history starts in 1864 with a simple wooden trough that collected sewage and carried it directly to the river, the Taggart Outfall was constructed in 1906. It is one of the longest-serving large diameter sewer pipes in the City. Spanning 7,600 linear feet, the 64 to 120-inch brick sewer was in need of rehabilitation. James W. Fowler Co. (JWF) worked with the City of Portland’s Bureau of Environmental Services to rehabilitate portions of the Taggart Outfall.
In order to minimize surface disruptions and maximize the use of existing resources, trenchless rehabilitation techniques were used where feasible. JWF was also responsible for the repair of manholes and local hydraulic improvements. The 114-year-old brick sewer tunnel was critical in serving Southeast Portland residents and visitors. While completion of this project will increase the sewer’s resiliency, extend service life for up to an additional 100 years, and help prevent sewage overflow in buildings and on streets, it didn’t come without challenges. The tunnel is located close to high traffic areas including TriMet light rail racks, Union Pacific Railroad tracks, as well as, Highway 26/Powell Boulevard. Rainfall also interrupted work as stormwater flowed rapidly through the tunnel creating unsafe working conditions. Even with the challenges presented, JWF crews successfully completed repairs. Working underground minimized disruptions to the public and surrounding businesses.
The main repair methods used are Slip Lining and Tunnel Liner Plate. Using a locomotive, crews worked up to 75-feet below the surface to construct a new sewer inside the old brick sewage system. Some sections were be completed by inserting 8-foot long fiberglass-reinforced pipe liner inside the tunnel; other sections involved bolting new steel liner plates inside the tunnel. With careful attention as to not deflect the pipe, the gap between the host pipe and the tunnel liner plate was then filled with grout.
Manholes were rehabilitated in order to augment or restore structure integrity, repair voids, remove loose materials, protect against corrosion and infiltration, among other things. Active inflow and infiltration (I/I) into the sewer was reduced through proper preparatory work prior to tunnel liner installation and localized repairs. Pre construction inspections of sewer mains to determine the location and extent of corrosion, deformation, obstructions and defects were critical in the projects success. Three-dimensional light detection and ranging laser (3D LIDAR) was one of the tools used to generate inspection summary reports for all locations. Internal dimensions of the pipeline were also measured to accurately show the inner diameter of the entire pipeline. With this, geographic referenced 3D point clouds for bend-radius configuration analysis was also provided. Inspection logs were kept, tunnel liner plates were installed, and trees in the public right of way were replaced. Now, residents and business-owners can rest assured knowing their living and working space will not flood with sewer water on a stormy Portland day. In the midst of downpour, it’s a little ray of sunshine knowing the Taggart Outfall is rehabilitated and ready to serve its constituents. JWF is proud to have furnished all labor, supervision, equipment, tools, and materials to make this rehabilitation project a reality for our community, the City of Portland, residents, and visitors alike.
