Environmental Services is designing a project to repair about 3,700 feet of the 110-year-old brick Taggart Outfall sewer so that it can operate for another hundred years. The sewer pipes are showing signs of cracks, fractures, missing brick and mortar, and obstructions in the pipe, putting the Outfall at risk of structural failure. The Taggart Outfall drains a large area of Southeast Portland and conveys overflows from the combined sewer system to the Willamette River during rain events. Structural failure of the Outfall would have profound impacts on this area, potentially flooding numerous businesses and residences and resulting in many millions of dollars of property damage and disruption.
Although the Taggart Outfall has functioned for the past 100 years, it is currently in need of structural repair. This project will allow the Outfall sewer to properly perform its role in protecting public health, water quality, and the environment for another 100 years.
Sewer repairs are anticipated to occur between May and October of 2018 and 2019. The project will likely require two construction seasons because crews can safely work in the Outfall pipes only on dry days.
The Taggart Outfall is a large-diameter and deep sewer pipe. It is between 5 to 10 feet wide and 23 to 64 feet below the surface. Safety requires that crews will only be able to work in the Outfall pipes on dry days when there will be no flow from either rain or other parts of the sewer system.
The primary construction method to repair the Taggart Outfall will be Tunnel Liner Plate. Of all the construction methods Environmental Services analyzed, this method will most effectively reinforce the Outfall pipe and cause the least impact and disruption to the neighborhood. This method will minimize traffic impacts and noise. All access to the sewer will be through existing manholes with no excavation required.
Crews will enter the sewer through existing manholes, as illustrated in the project map. Inside the sewer, crews will essentially construct a new tunnel inside the old brick sewer. They will assemble the new steel liner plates in place inside the sewer and then fill the space between the liner and the old brick sewer with grout.
Work at each manhole west of the light rail tracks may last several months, while work on manholes in SE 16th Avenue and in SE Tibbetts Street should be less than a month at each location. Crews may be working at multiple locations at the same time.
To take advantage of Portland’s dry season to complete these urgent repairs, the city is planning to work all hours and all days in the industrial area between SE Grand Avenue and SE 16th Avenue adjacent to light rail. Work in the other, more residential areas will be completed during regular daytime construction hours from 7 a.m. to 6 p.m. Monday through Friday, and Saturday if needed.
Potential Traffic Impacts
Accessing the sewer line through manholes will require lane closures, which will require traffic control and construction signage. When lanes are closed in a work zone, they will be closed 24/7 for the duration of construction in that area, including at night and on weekends. Where needed, traffic will be routed around the work zones.
Traffic controls will be implemented at the following locations:
- Traffic restrictions along SE 10th Avenue from SE Gideon to SE Woodward
- Pedestrian and cycling detours near the "Clinton Triangle" - along SE Gideon between SE 13th-16th
- Minor traffic restrictions for a day or two at SE Milwaukie and SE Woodward
- Traffic restrictions for short periods of time near SE 16th and SE Pershing, SE 16th and SE Center, and SE Tibbetts and SE 19th.