The Carolina Trunk is a large sewer pipe - essentially a 3-4 foot wide tunnel deep underground. This pipe is showing signs of deterioration and needs to be replaced. The new pipe will have a life expectancy of 120 years or more. The repairs will maintain sanitary and storm services and help protect public health and the community by preventing sewage releases to buildings and streets.
Project Area
The project area is located in S Portland, between S Barbur Blvd and S Macadam Ave.
What's Happening Now
The project team has reached the 60% design milestone. The design approach involves abandoning the existing sewer trunk within the project limits. This section of the existing sewer trunk is in very poor condition, with limited access points for maintenance workers, and is situated beneath several private properties. The old pipe will be decommissioned by filling it with concrete to ensure that there are no future issues.
Additional pipes will be constructed in SW Slavin Road to accommodate storm and sanitary sewer flows. These new pipes will provide increased capacity and service for many decades to come.
How We Plan to Build the Sewer Trunk
Designers have divided the project into four “sections.” Each section has unique characteristics and will require different designs and construction methods. Please see below for a description of the preliminary design for each reach.
Section One: SW Slavin Road
Section One will require substantial work in SW Slavin Road. Crews will build temporary retaining walls at several locations along the north and south sides of Slavin Road to allow for equipment access.
Crews will need to close the north lane of SW Slavin Road and install new sewer and stormwater pipes using the open trench excavation method. All properties will still be accessible during the work.
Anticipated Timeline
Once we have completed the project design in late 2024 or early 2025, we'll have a better schedule for construction and a general start date.
Fall 2024 – Spring 2025 – Preliminary work and preparation will begin throughout Section One this fall. Preconstruction activities can include soil sampling, surveying, and relocating some underground utilities. You can find out more about preconstruction activities by visiting the preconstruction information webpage.
Beginning around Summer 2025 – We anticipate major construction to get started on Section One of the sewer trunk. Section One should take about 18 months to complete. Environmental Services will send out notices of activities, including detailed timelines once we have established an official schedule for the project.
Traffic Impacts
When major construction begins in 2025, crews will close the north lane of SW Slavin Road to install temporary traffic lights at either end of the work zone. These lights will allow vehicles to travel through the work zone using the south lane in one direction at a time. This one-lane configuration will be in place for the duration of work on SW Slavin Road.
During some phases of the work, neighborhood residents may need to detour around a street closure to access SW Slavin Road.
Impacts to Private Property
Due to limited space in the work zone, it may be necessary for crews to use private property to store materials and equipment, install temporary retaining walls, and conduct construction activities.
City Staff will continue to work with nearby property owners to acquire easements and other permissions for work that may impact some private properties adjacent to Slavin Road. Over the coming months, staff will continue to engage nearby property owners.
Section Two: SW Slavin Road to Interstate-5
For Section Two, crews will dig a shaft at the east end of SW Slavin Road and another pit at the bottom of the hill next to Interstate 5 (I-5). Crews will then tunnel underground between the two pits and install a new pipe. The majority of this work will occur inside an existing City easement.
Anticipated Timeline
Work on Section Two will occur at the same time as Section One and should take about 12 to 18 months to complete.
Traffic Impacts
To access the area adjacent to I-5, crews will build temporary construction on and off ramps accessed from the freeway. This work will occur mostly at night and will require the closure of one lane of I-5 while the ramps are built. Once installed, crews will access the site via the construction ramps during the day and at night as needed.
Impacts to Private Property
City staff will continue working with nearby property owners to acquire easements and other permissions for work that may impact some private properties adjacent to the work zone.
Nightwork and Noise
During some phases of the work in Section Two, we anticipate that the Oregon Department of Transportation (ODOT) will require some of the work to occur at night. Environmental Services is working with the City Noise Office to acquire the proper permits and ensure that crews follow noise requirements for night work.
Section Three: I-5 to S Corbett Avenue
For Section Three, crews will dig a shaft inside the traffic island located on Corbett Avenue, between I-5 and the freeway off ramp. Crews will then tunnel underground between the pit in S Corbett Avenue and the pit on the other side of I-5.
Anticipated Timeline
Section Three will occur at the same time as Section One and Two and is anticipated to take about 18 months to complete.
Traffic Impacts
Brief delays along Corbett Avenue and connecting streets will occur during some construction activities.
On rare occasions, there may be a need to close the Corbett off ramp. These closures will be limited, and detours will be communicated well in advance.
Section Four: S Corbett Avenue to S Macadam Avenue
For Section Four, crews will dig a pit adjacent to S Macadam Avenue. This pit will be located in an existing parking lot that is partially owned by the City of Portland. Crews will then tunnel underground between the Macadam pit and the pit located up the hill next to S Corbett Avenue.
Once all the tunnels are complete and the new pipes are installed, crews will connect the newly constructed system to the existing system underneath S Macadam Avenue.
Anticipated Timeline
Section Four will occur at the start of the project and is expected to take about 15-18 months to complete.
Traffic Impacts
Some brief delays may occur near the end of the project when crews connect the new pipes to the existing system in S Macadam Avenue.
Impacts to Private Property
Private property impacts for the shaft adjacent to S Macadam Avenue are expected. City staff are working directly with the property owners on agreements for using this area.
Project Background
Sewer trunks are an important part of the City’s sanitary sewer system. Smaller neighborhood sewer lines connect to these trunk lines, which then carry flow of sanitary sewage to treatment facilities. The Carolina Trunk travels under I-5, which makes this project a high priority.
This area of Portland presents its own challenges that the project team must consider. Much of the project area is located on old landfill that is covering an old stream bed. The steep terrain in this part of Portland also presents challenges that the engineers must consider when designing the new sewer pipe alignment.
The current trunk line runs underneath private properties, making it nearly impossible to repair without temporarily displacing residents. Given these challenges, the design team has proposed a new alignment (see map above) that accounts for these challenges. This new alignment will move the trunk and other infrastructure under existing right of way and permanent easements and provide access points to make it easier to maintain in the future.
We Want To Hear From You
We would like to hear from you about special events, school activities, and community services in your neighborhood you think may be impacted by this project. Also, we want to know if you have any concerns related to business operations, disability or mobility issues, medical or business deliveries, and proposed night work. Your input will help us minimize the impact to your neighborhood during construction.
Sign Up For Project Updates
Environmental Services will inform residents and businesses about project activities and respond to questions and concerns in a timely manner. The following resources will help you stay informed and report concerns:
- Project Updates: To receive email or text message updates for this project, sign up now at Sign Up for BES Project Updates. Updates provided through our free GovDelivery subscription service are the best way to stay informed about what’s happening and what to expect. You can also sign up for bulletins on other projects and topics
- Questions: Contact Aaron Abrams at Aaron.Abrams@portlandoregon.gov or call 503-823-2827.
- Sewer Emergency: Call 503-823-1700 immediately. The City Maintenance hotline is staffed all hours, all days (24/7).