RiverViews, Spring 2024

Two construction workers inside a large trench with jacks supporting the walls. The two construction crew members are positioning a large diameter sewer pipe that is being lowered in by a crane.
RiverViews is a newsletter from the Bureau of Environmental Services — your sewer and stormwater services provider.
In this article

Maintaining Our Hidden Infrastructure

Beneath our busy streets and neighborhoods lies a network that every Portlander relies on every hour of every day.

Managed and maintained by Environmental Services, thousands of miles of sewer pipes, nearly 100 sewage pumping stations, and two treatment plants are unseen or unnoticed by most Portlanders. While a lot is hidden from view, this infrastructure plays an essential role in moving and treating wastewater, preventing pollution, managing rainwater runoff, and protecting public health and the environment.

Like many cities in the United States, Portland has a wastewater and stormwater system that is aging and needs significant investment. Some sewer pipes were built 100 years ago or more.

Learn about a real-world example of what happened when a sewer pipe failed and how that failure impacted a Portland neighborhood. Without significant investments in upgrading and maintaining our infrastructure, these costly failures will become more common.

SE Yamhill Sinkhole

Behind the scenes of an emergency repair project

The SE Yamhill St. sinkhole shortly after it opened up. Large chunks of the road surface can be seen in the sinkhole. The approximate size of the underground portion of the sinkhole is outlined in white paint, and a PBOT truck has the road blocked off on SE 76th.
10:00 a.m., May 12, 2023

Emergency response

A map showing the sinkhole location, which is between SE 74th and 76th on SE Yamhill St.

On Friday morning, a concerned resident reports a sinkhole on SE Yamhill St between SE 74th and SE 76th avenues.

By 10 a.m., Portland Bureau of Transportation (PBOT) crews arrive at the scene to block off the affected area, implement traffic control, and assess the sinkhole and surrounding area for immediate safety risks to the community.

By noon, Environmental Services engineers identify that the repair work requires the deployment of their emergency on-call repair contractor.

The following week, engineers identify the cause of the sinkhole. A private sewer lateral, dating to 1914, that connected to the mainline about 10 feet down had failed. The failure created an underground cavern along the clay sewer pipe, eventually leading to the sinkhole.

Developing a solution

Over the next several weeks, the on-call emergency contractor works to stabilize the sinkhole and prevent further damage.

Meanwhile, Engineers are hard at work assessing the extent of the repairs required and discover the sewer mainline further down SE Yamhill had been failing for an unknown amount of time.

Engineers quickly recognize the need for specialized materials and begin sourcing a custom-sized 16-inch liner to reinforce the clay sewer pipe.

Several orange barricades and a road closed to through traffic sign are blocking off SE Yamhill St. Between the barricades, an excavator is making repairs.
10:10 a.m., May 18, 2023 - The crews repair the failed private sewer lateral and close the street until the mainline can be repaired.

Challenges and delays

Challenges and delays arise the last week of May when the liner ordered is unavailable due to industry-wide material shortages and supply chain disruptions. Crews learn a 16-inch liner can’t be delivered until the end of July.

Environmental Services has liners for smaller diameter pipes on hand for the many scheduled projects around the city and typically borrows pipes from a scheduled project for emergencies. However, that isn’t the case for 16-inch liners, which are larger than the more common pipe sizes found in residential neighborhoods.

A view inside the sinkhole from the street level. The sinkhole’s walls are now supported with jacks. At the bottom of the sinkhole, you can see the original clay sewer pipe.
7:45 a.m., August 7, 2023 - Stabilizing the sinkhole is crucial to prevent further collapse, safeguarding both the surrounding community and the workers.

Pipe repair begins

The liner is delivered, and the crew begins installation on August 7.

A crew member sitting and looking at two computer screens while operating equipment with two joysticks. One screen has a camera feed of inside the sewer pipe.
12:45 p.m., August 7, 2023

To repair the old clay sewer pipe and extend the overall life of the pipe by an estimated 50 years, cured-in-place-pipe lining (CIPP) is used. The process effectively creates a new pipe inside the existing pipe and doesn’t require digging up the entire length of the pipe and the street. For more information about this technique, as well as other sewer construction methods, visit the construction methods webpage.

An excavator, dump truck, and hydro-excavation truck positioned around the sinkhole work area. One crew member is guiding the hydro-excavation equipment, which looks like a large vacuum hose.
8:50 a.m., August 8, 2023
A crew member standing above a drill hole in the street and controlling hydro-excavation equipment.
Crews begin hydro excavation, a digging method that uses pressurized water and a vacuum system to safely and precisely remove soil and debris.
A concrete truck pouring high-density fill into the sinkhole. Several crew members are standing around the hole, making sure all the voids are being filled in.
12:30 p.m., August 8, 2023 - After repairing the pipe, crews fill the void with densely compacted fill to stabilize the ground and prevent further collapse.

Filling the sinkhole and paving

With the liner installed, the project team can fill the street voids the following week.

One section at a time, crews dig to expose the pipe down the length of the 100-year-old mainline and fill the underground voids to ensure the street is free of any large air pockets underground. If not done right, the fill may not support the pipe or street properly.

On August 15, SE Yamhill is paved, and work shifts to the intersection of Yamhill and 76th to repair the sub-surface voids around the maintenance hole.

Crews finish the final maintenance hole repairs and complete the work on August 16. Before reopening SE Yamhill, final testing and inspection ensure the work area is safe for traffic and public use.

A dump truck and asphalt roller working on finishing the road surface.
12:15 p.m., August 14, 2023
Two crew members doing some preparation work with rakes and shovels before the final layer of pavement.
A crew member doing a final pavement density test on the finished pavement. The piece of equipment to analyze pavement density is placed on top of the pavement and is approximately the size of a shoe box.
8:25 a.m., August 15, 2023 - A crucial final step is a pavement density test, which measures compactness to ensure the pavement meets durability and structural standards.
A look down SE Yamhill St. with all the work completed.
7:30 a.m., August 15, 2023
A look down SE Yamhill St. with all the work completed. There are just a few cones around the finished pavement area as it cures.
The final process of grading, paving, and cleaning up is completed on SE Yamhill St.

Emergency repairs vs. planned maintenance and upgrades

The SE Yamhill sinkhole is one reminder of infrastructure’s critical role in our daily lives, the risks of aging infrastructure, and the importance of ongoing maintenance. The choice to use the most durable and cost-effective repair option highlights our commitment to public safety and responsible resource management.

Funding challenges can create a cycle of emergency repairs, which diverts resources from planned maintenance and upgrades. This cycle can decrease service reliability, create service disruptions, increase costs for ratepayers, and impact the quality of life for Portlanders.

We work hard to keep you informed

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Who is Environmental Services?

We are Portland’s sewer and stormwater utility, made up of a team of nearly 700 employees who plan, design, construct, monitor, operate, and maintain the pipes, pumps, and treatment plants that collect and recover resources from wastewater and stormwater. We reduce and prevent pollution, enforce regulations, manage stormwater, and protect and restore natural areas and urban waterways.

What is it like to work for Environmental Services?

Find out from some of our employees as they share their stories and experiences.