Construction continues on the 114-year-old Taggart Outfall—a large, brick sewer tunnel located deep underground. This critical sewer line serves Southeast Portland. Repairs will increase the sewer’s resiliency, extend its service life for up to another 100 years, and help prevent sewage releases.
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. It is located deep underground in a difficult location close to TriMet light rail tracks, Union Pacific Railroad tracks, and Highway 26/Powell Boulevard. A 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.
Aboveground construction activities are concentrated at existing manholes along the Taggart Outfall and a sewer access shaft on private property. Most of the repair work occurs belowground from inside the sewer tunnel.
What’s Happening Now
Crews made steady progress over the past month. They completed grouting work between the new pipe liners and the old brick sewer, inspected lateral connections to adjacent properties, dismantled the crane, repaired a manhole at the sewer entry shaft, and removed the engineered shoring from the sewer entry shaft. They then backfilled, closed, and paved the shaft.
Activities for the next few weeks will include the following:
- Restore permanent fence.
- Install flow monitoring equipment.
- Complete post-inspection of this remaining work.
Additional Repairs in 2021
The project will require additional work during next year's dry-weather season—the installation of a cementitious liner and the abandonment of a manhole on private property. An unusually high water table this summer combined with delays due to wildfire smoke necessitated postponing this work.
Next summer, using manholes to access the sewer tunnel, crews will install a concrete liner over the surface of 433 feet of bolted tunnel liner plates to create a smooth finish. This work will take about four weeks to complete. Environmental Services will notify residents and businesses when that work is scheduled.
We Want to Hear from You
Environmental Services will work directly with the community throughout the course of the project. Community outreach staff will listen to your suggestions and respond to your concerns.
Crews have shifted to working daytime hours only. For noise complaints in Southeast Portland, email the Noise Office at firstname.lastname@example.org or complete the online form. Provide as much detail as possible about the noise, its potential source, your location, the date and time of the noise, its duration, and its effect on you. If possible, take a video with your cell phone and include it in your report.
Environmental Services is repairing about 3,700 feet of the Taggart Outfall sewer tunnel, which measures from 58 to 120 inches in diameter and from 20 to 75 feet deep.
The Taggart Outfall project is not a typical sewer construction project. There is very little aboveground construction activity and no digging in streets. Crews conduct repair work from inside the sewer tunnel deep underground.
The primary construction methods to repair the Taggart Outfall are Slip Lining and Tunnel Liner Plate. Crews enter the sewer tunnel from maintenance access holes and a sewer access shaft and climb down 30 to 75 feet below the surface. Working from a locomotive on a steel track laid inside the tunnel, crews are essentially constructing a new sewer inside the old brick sewer.
They are constructing some sections by inserting a fiberglass-reinforced pipe liner inside the tunnel. They are constructing other sections by assembling new steel liner plates in place inside the tunnel. They then fill the space between the new sewer and the old brick sewer with grout. These methods avoid digging trenches in the roadway and reduce aboveground impacts to the traveling public and adjacent properties.
For safety, crews can only work inside the tunnel on dry days when there is no water flowing into the tunnel. In the event of rainfall or a sudden surge of stormwater flowing into the tunnel, crews and equipment must be removed quickly from the sewer tunnel, and completion of repairs may be delayed.
Tunnel fans are necessary to provide ventilation to crews working in the confined space of the sewer tunnel deep underground. The fans must operate all hours and all days when crews are inside the tunnel.
What to Expect
While there will be some equipment and materials aboveground, most of the work will be conducted belowground inside the sewer tunnel. You can expect the following activities and impacts:
- Temporary lane closures and on-street parking removal may be necessary to enable safe access to the sewer tunnel.
- Equipment that generates noise will include vactor trucks, compressors, generators, ventilation fans, forklifts, and pile-driving equipment. Night work will require light tower trucks.
- Vactor trucks will operate vacuum pumps necessary to clean the tunnel and remove materials during construction. They may operate hours at a time.
- There may be periods of inactivity between construction phases due to a variety of factors including weather, subcontractor schedules, and availability of materials.
- A city inspector will be on-site during work hours and may be able to assist you with an immediate need during construction.
- Sewer, water, and other utilities will remain in service during construction.
The Portland Noise Office granted Environmental Services a noise variance to work all hours and all days (24/7) in the industrial areas of the project west of TriMet light rail tracks to enable project completion during the dry-weather season. Crews are currently working from 7 a.m. to 6 p.m.
Noise Mitigation Measures
The major sources of noise will be the vactor trucks, grout pumps, generators, forklifts, and tunnel fans. The contractor will be required, by contract, to use quiet generators. Mitigation measures are incorporated into the construction contract. These mitigation measures are the following:
- Night and weekend work is restricted to industrial areas where there are no residences within 200 feet.
- All compressors and generators will be silenced. Noise levels for quiet generators are around 69 decibels.
- Backup alarms on all trucks will be turned off and spotters will be used instead.
- Vactor truck use and any required saw-cutting will not be allowed from 10 p.m. to 7 a.m.
- Tunnel fans will be enclosed with sound barriers.
- Lighting will be adjusted to the lowest levels to limit overshooting the work site and impacts to the immediate community.
- City inspectors will be on site during work hours to enforce contract restrictions on noise.
Pre-Construction Activities 2018: The contractor for this project, James W. Fowler Co., conducted closed circuit television (CCTV) inspections and 3D laser profiling of the Outfall tunnel in the fall of 2018, which allowed the City to confirm existing conditions, create a profile of the sewer's interior, and then order the materials needed to repair the Outfall.
Mobilization in October 2019: During the fall of 2019, the city's contractor completed repairs to the small-diameter (58 to 84-inch diameter) pipe sections in SE 16th Avenue and in SE Tibbetts Street.
Re-mobilization in Spring of 2020: Crews mobilized again in March 2020 when weather permitted them to work safely inside the tunnel. This phase of work includes repairs to the large-diameter (118 to 120-inch diameter) pipe sections between SE 16th Avenue and the Willamette River.
Accomplishments in 2020: Crews have completed the following work:
- Construction of a deep sewer access shaft on private property at SE Powell Boulevard and SE 13th Place. The new shaft measures 15x15 feet wide and 35 feet deep. This shaft reduces the need for multiple access locations along the sewer tunnel.
- Installation of 2,725 feet of steel tracks inside the Outfall sewer tunnel.
- Installation of an electric, human-operated locomotive and pipe lining cart. Using a crane, crews lowered the locomotive into the sewer tunnel and onto the tracks. Similar locomotives have been used in mining and tunneling industries since the 1860s.
- Installation of fiberglass-reinforced pipe lining. Using the locomotive, crews pushed the fiberglass-reinforced pipe lining along the track and into position inside the tunnel.
- Installation of one section of pipe lining at a time. The project required 330 segments of 8-foot-long straight pipe, and 36 segments of joint pipe.
- Pumping of grout into the space between the lining and the old brick sewer—done after every 100 feet of pipe lining installation.
- Installation of new steel liner plates into the sewer tunnel, and assembly of the steel liner plates in place inside the tunnel.
- Pumping of grout into the space between the liner plates and the old brick sewer.
- Cleaning, inspection, and repair of a maintenance access hole. Casting a new concrete liner inside the existing maintenance access hole avoided digging in the street. The new concrete liner will create a watertight, corrosion-resistant interior that will reinforce the existing structure without having to replace it.
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