Big picture: why are we doing this?
You’ve heard about our region’s earthquake risks. The current water mains (pipes) that carry water across the Willamette River will probably not work after a major earthquake.
- When the existing crossings are damaged by an earthquake, it will leave the entire west side of Portland, over 360,000 people, without reliable water for six months and likely much longer.
- This could lead to dangerous conditions for fire and human health, and the loss of billions of dollars of economic output.
- Not only does investment in this project make sure we can fight fires and provide water to critical facilities like hospitals after an earthquake, it also strengthens the entire state’s economic recovery.
This new pipe is critical in helping make sure we can get water to the west side of the Willamette after an earthquake. That includes making sure we can get water to the families, hospitals, businesses, and schools downtown that help make Portland such a great place to live.
General construction
How big is the pipe?
The pipe will be 48-inches in diameter.
How much water per day is the pipeline designed to deliver to the west side?
39 million gallons of water per day
Construction impacts and coordination
Construction will take place in phases over 18 months. These will bring noise and traffic changes to communities on both sides of the river. More information about construction impacts is available on our Construction webpage.
We built community engagement into the project’s budget and contract. We’ve been reaching out to the public for some time, and we’re using public input to shape our plans. We’re communicating with businesses to help make sure deliveries and customers can still reach them. Soon we’ll share our plans and seek your input again.
Based on data from soil probing and sampling, we changed the path the pipe will take. That also changes the effect on neighborhoods:
- We’ll dig the shaft — the deep hole down to tunneling level — in South Waterfront Park instead of in the South Montgomery Street traffic circle. That will help traffic flow in the neighborhood.
- Along South Montgomery Street, we’ll tunnel instead of installing pipe in a trench. That way, we can keep the street open for residents, businesses and visitors.
What about noise?
We’re working on our plan to control and reduce noise, and we’ll share it as soon as we can. We’ll keep noise levels within regulatory limits based in public health — and within the permitting requirements of the City's Office of Community & Civic Life. Most noise will be during normal work hours, Monday through Friday.
The noisiest part of the project will likely be on the east side near SE Water Avenue.
On the west side of the river, digging the shaft at South Waterfront Park will be noisy. The boring machines will be deep underground and produce very little noise — but they require support from noisier equipment above ground. We’ll also use generators to support various pumps and monitors overnight.
Bringing in and taking away the boring machines will generate noise from cranes, trucks and support equipment. We’ll do that during normal construction hours.
We’ll use a vacuum truck to take out soil and mud more gently when we dig near underground utilities. The noise won’t be regular or frequent.
What about parking?
We may need to remove some parking spots near the roundabout at S Montgomery Street and S River Drive to route traffic through the west side of the roundabout. Emergency vehicles and the public will still have access around the site. Local restaurants and stores will have access for delivery trucks. When we are installing pipe in trenches in the street on the east side, we will likely close parking on the street two blocks at a time to make space for equipment to move around.
What about truck traffic?
Our contractor is planning how to route traffic through the area near the roundabout to allow safe entry and exit of trucks and other equipment. We don’t have all the details yet.
We do know that while we’re digging the shaft, lots of trucks will move in and out of the site to remove dirt. The amount of dirt removed will vary day by day. We anticipate the heaviest traffic will last three to six months. During other phases, work will be quieter.
What will you do in South Waterfront Park? What will it look like?
First we will dig a shaft, or 80 to 100 foot deep hole. The shaft is where the drilling machine that we're launching from the east side of the river will arrive on the west side. We will also launch another drilling machine from the shaft towards South Harbor Drive. We will also store materials for reinforcing the shaft at this location, and bring up the soil from the microtunnel being dug between the park and South Harbor Drive. The dirt that is excavated from the tunnel under the river will be removed on the east side of the river.
You can expect to see a large drill, forklift, crane, excavator, loader, and trucks for concrete, dumping, and delivery. We’ll also have separation plants, pumps, storage containers, and generators. The boring machines will be mostly underground.
The construction zone will appear contained, with opaque fencing rather than open chain-link. It won’t be easy to see in from outside.
How big will the shaft in South Waterfront Park be?
It will be approximately 35 feet in diameter and approximately 80 to 100 feet deep.
Will you restore South Waterfront Park after the project?
Yes. Restoring the park to pre-project conditions is part of our budget. We are working with Portland Parks & Recreation to use the park’s original designs and plans for restoration.
Economics and cost
How much will the project cost?
We’re finishing an estimate for construction costs. We’ll share it later this spring.
Another important question is how much not doing this project would cost. Without it, restoring water to the west side of the river after an earthquake would take six to twelve months. That would equate to major economic impacts for businesses and families who would be out of water for up to a year.
Right after an earthquake, this project makes sure we can fight fires and bring water to crucial facilities such as hospitals. Over the long term, It benefits more than 360,000 people living on the west side of the river and helps our region’s and our state’s ability to recover economically.
Is eminent domain required?
No. West of the river, the proposed route is all either in public right-of-way or on other public property. East of the river, we’re notifying and coordinating with affected private-property owners — but the property will remain theirs.
Project History
In 2010, a Water Bureau report recommended an earthquake-hardened river crossing. More studies in 2019 explored the best path the pipe should take across the river, how it should be installed, and how to connect it to the existing system.
In May 2019, the Water Bureau hired a design-build team, led by J.W. Fowler Company, to start designing the project. We chose this team for its innovative proposal to combine two modern construction methods — horizontal directional drilling (HDD) and microtunneling.
Exploratory Phase — 2020
We knew this work would be challenging, so we built in an exploratory phase. This allowed us to spend a little and learn before we spent a lot.
We needed to know exactly what was underground before going “full bore,” so we did a small-scale pilot bore — a geotechnical probe — in August 2020. However, we ran into problems.
The drilling technology we were using, Horizontal Directional Drilling (HDD), requires the hole to stay open after drilling, for pulling the pipe through later. Instead, we found out that the hole we drilled would collapse, with the gravelly soil acting like stacked marbles. The geoprobe contractor, one of the most respected and capable in the nation, saw that HDD was not viable.
Testing for Direct Steerable Pipe —2021
In 2021, we did more testing to identify how and where to install the pipe. We learned that we needed to move the drill path a little shallower and use direct steerable pipe.
Direct steerable pipe installs a casing (a larger pipe that encloses the water pipe) behind the drill bit. This prevents the hole from collapsing in the gravelly soils. But the pipe it installs is less flexible than with HDD, so we needed a straighter, more direct alignment.
We also wanted to avoid the gravels and boulders that stopped the HDD probe in testing. Direct steerable pipe can be installed closer to the surface since it requires less pressure to keep the operation working. Our contractor is fine-tuning the design so we can begin construction in late summer 2022.
Earthquake resilience
What does “earthquake-resilient” mean?
It means the new pipe will be able to withstand any movement of surrounding soils, either moving with the soil or allowing the soil to move around the pipe.
The goal is to help make sure we can get water to the west side of the Willamette River even after a Cascadia Subduction Zone earthquake — up to magnitude 9.0. It’s part of the earthquake-resilient backbone system we’ll build over the coming years.
I've heard that the soil on either side of the Willamette River could liquify and move up to ten feet. Will that cause the new pipe to break?
Our entire project is built on the goal of building a pipeline that won’t rupture during an earthquake. It is true that we expect the soils near the ground surface to move around in an earthquake. That is why we are burying the pipe deeper where movement is much less. There may be minor movement in the soil at this depth, but the pipeline will be designed to withstand these small movements. We have created a model that incorporates the strength of the soil combined with what we know about the magnitude and direction of shaking created by the earthquake, to build a pipeline that can withstand these forces without damage.
How this project fits with the Water Bureau's other earthquake-related measures
This pipe across the Willamette River is part of the Water Bureau’s long-term plan to upgrade the backbone of our system — key supply, treatment, transmission, distribution, and collection elements — between our two sources on the east side and the Washington Park reservoir on the west side.
It will bring us closer to the 2013 Oregon Resilience Plan goals for water and wastewater systems. The plan recognized that earthquake-related upgrades for the whole system would cost more than most water bureaus spend on even 50 years of improvements — so it called for upgrading the backbone elements soonest.
Our long-term plan is to upgrade the backbone all the way from the Bull Run Watershed near Mount Hood to the west side of Portland. We’ve prioritized the parts that would be hardest to repair after an earthquake. So far, we’ve upgraded the reservoirs at Washington Park, Powell Butte, and Kelly Butte, along with the trestles that hold our large pipes as they carry water into town. Now it’s time for the river crossing.
Technical
Earthquake standards
For structural design, we use design ground accelerations determined by the United States Geological Survey (USGS) and modified by site-specific considerations for local conditions.
We follow design processes from the Federal Emergency Management Agency (FEMA) and American Society of Civil Engineers (ASCE). We use state-of-the-practice methods to ensure the pipeline will withstand all the possible earthquake conditions for the vicinity.
What type of modeling or analysis is the project using to develop a design for an earthquake resilient pipe?
Our engineers are using a Fast Lagrangian Analysis of Continua (FLAC) model. The FLAC model uses ground motion measurements from different types of earthquakes around the world. The FLAC models are run with the different ground motions to evaluate ground deformations for different types of earthquakes. Design engineers use motions and modeling that match our location by selecting earthquake records from similar geologic settings around the world (i.e., subduction zones) and scale up the past earthquake records to the magnitude we are expecting (i.e., 9.0 magnitude).
Location
Why did you choose the current location?
We studied options for several years. We chose the current general location after considering:
- Community impacts
- Earthquake resilience
- Hydraulics of our water system
- The locations of structures, pipes, rail lines, etc. on the east and west banks, as well as piers for the Interstate 5 bridge
- Maintenance and shutdown requirements
- Construction staging requirements
We narrowed down the general crossing location by the types and composition of soil under and on the banks of the river, and our understanding of how best to install earthquake-resilient pipe in these soils.
This location gives us the best resilience, a safe and successful project with the least impact to communities, and a reasonable cost.
What routing and staging locations did you consider?
We considered these general locations:
- On the west side: SW Naito Parkway between SW Harrison Street and Market Street
- On the east side: near SE 10th Avenue and Harrison Street
The current alignment is the culmination of five years’ work by both the Water Bureau and our contractor to determine the best results for the best cost.
Why did you change the pipe’s route across the river in 2021?
This is important project history documented in the Testing for Direct Steerable Pipe —2021 section of this FAQ.
Can you change the west-side location of the pipe so there won’t be a construction site in South Waterfront Park?
No. If we tunneled from the east side of the river in a straight line west to downtown, we would run into the foundation of the RiverPlace Condominiums, underground piles that hold the Marina in place, and the Marquam Bridge supports. We also need to stay clear of large underground sewer and stormwater pipes north of RiverPlace. To avoid these obstacles, the pipe would need to make a sharp deflection, or bend — but the pipe can’t bend that sharply.
Instead, we’ll stop drilling at South Waterfront Park, then start again using a different type of machine. We’ll weld the two pipes together at an angle at that location. We’ll dig a vertical shaft for lowering the drilling machines as deep as 100 feet, and for welding together the pipes. The construction site and its staging area in the park is for digging the shaft. We considered digging the shaft in the S Montgomery Street circle instead, but that would have been more disruptive to traffic in the neighborhood.
Another option would be to change the water system’s underground route across town, established in the early 1900s, to line up an easier crossing. But that would be far more expensive, including the cost of impacts on many more communities, businesses and transportation routes.
Site geology
What did you learn about the soil during 2020 and 2021 that caused you to change the pipe’s route?
The geology on the west side of the river has three zones, each progressively deeper:
- Recent fill materials (wood chips, sand, gravels)
- Recent river sediments (sand and gravels, less than 15,000 years old)
- Ancient river sediments (gravels, Troutdale formation, two to three million years old)
Our test probe — a “geoprobe” that sends back data — was able to drill through the recent fill and the recent sediment layers of soil. Then it encountered the ancient Troutdale formation at depths of 50 to 150 feet, and couldn’t go further.
To overcome this problem, we changed drilling techniques from horizontal directional drilling to microtunneling. The specific form of microtunneling we are using, direct pipe, installs a casing (a larger pipe that encloses the water pipe) behind the drill bit, preventing the hole from collapsing in the gravelly soils.
Residents know of hazardous material in the soil and groundwater underneath the RiverPlace development. How will the project manage them?
The project will be watertight and heavily regulated by the state Department of Environmental Quality. We’ll continually test and treat water to prevent releasing hazardous materials into the river.
We’ve also planned for hazardous soils, but we often run out of time to talk about it when we give public presentations. We’ve done an environmental study and we know where the contamination is. We believe we’re equipped to protect the area.
Drilling technologies
How do drill bits differ for the initial and current drilling methods?
HDD uses a large, rotating drill bit like what you would use to drill a hole in the wall of your house, just bigger. Direct steerable pipe uses cutter heads (rotating cylinders with sharp teeth) mounted on a circular cutting face.
For a closer look at drilling technologies, watch this video from a well-known drilling company.
With the change to the drilling method, you’ll be drilling closer to the surface. Why?
The pipe string behind this type of machine is less flexible than one pulled by an HDD machine — so we needed a more direct alignment that doesn’t descend as deeply under the river. We also wanted to avoid the gravels and boulders that stopped the HDD probe. It’s safe and effective to install steerable pipe closer to the surface because it requires less pressure from the surrounding soils to keep the operation working.