COVID-19 Risk Level for Multnomah County: High Risk

Washington Park Reservoirs construction updates

Construction type
Project status
Under construction

Construction at the Washington Park Reservoirs started in 2016 and will continue until 2025. Read on for the most recent update.

2016 through 2025


On this Page

The Water Bureau is replacing its original 1894 reservoirs with a new 12.4-million-gallon, seismically reinforced underground reservoir. This reservoir will supply water to Portland’s west side and serve more than 360,000 people, including all downtown businesses and residents, 20 schools, 5 hospital complexes, and more than 60 parks.

Sign up for the project email newsletter.

When you subscribe, select the checkbox next to "Washington Park Reservoir Improvement Project."


Taken from above the reservoir site, this photo shows the Gatehouse and Dam at Washington Park along with a variety of construction activities going on around it.
Click here to view our live webcam

We began the first fill of the reservoir in mid-December to begin testing the reservoir. The reservoir is divided into two chambers, known as cells, and as of mid-January, both cells were filled.

Take video tours of the unfilled reservoir

Due to precautions we are taking during the pandemic, we couldn’t offer public tours of the finished reservoirs. We were, however, able to capture some video—two videos, in fact, each with a different look and feel. We hope you enjoy! 

Sometimes, the infrastructure we build is so big it feels like it should be in a movie. In the spirit of Hollywood, we created a movie “trailer” for the project. Get your popcorn and check it out.
How do you build an underground reservoir that's capable of holding millions of gallons of water and withstanding earthquakes? Carefully, and with a lot of help. Join Washington Park Reservoirs Improvement Project inspector Bill Nordquist on this tour of Washington Park Reservoir.

Madison Trail reopens for public use 

Illustrated map shows the closure of Madison Trail between SW Sacajawea Boulevard and SW Canyon Road

As of March 1st, a fallen tree has been cleared from the path and Madison Trail has reopened. Our contractors may need to make temporary closures of the trail to move equipment and supplies around the site from time to time. However, these closures will take place during construction hours, and the trail will remain open during non-working hours. 

Filling the reservoir 

We have begun the process of filling the reservoir with water. Because this is the first time the reservoir structure has had to withstand the weight and pressure of water, we are only filling one of the two cells at a time, and only bringing the water level up four feet per day. This allows the weight of the water to “settle in.”

Leak testing

At the base of the 40' high reservoir wall, water is seen seeping through hairline cracks.
How big are these cracks? As you can see in the picture above, these are hairline cracks, so small that water slowly weeps through them. Tests in the first cell we filled showed only trace amounts of water lost through leaks, measuring well below the amount that is considered “allowable.”

You might be surprised to learn that it is common to find small leaks and cracks the first time a brand-new reservoir is filled. Even though it’s the best building material to use for all kinds of projects, concrete cracks. Just look at your own driveway or sidewalk to observe the properties of concrete. Because we expect this, concrete crack repair is a step in our process and written into our contract. 

Some of these cracks may repair on their own during the filling process through a process called autogenous healing. In this process, cement from within the reservoir hydrates and cures, sealing these hairline cracks.

Crack repair is an anticipated step with the construction of any large concrete infrastructure project.

For the fractures that don’t heal on their own, we hire specialized divers to swim through the filled reservoir with video cameras and canisters of a milk-based substance. If they see an area that looks like it might be prone to leaking, they spray the milk sealer into the water. If there is a crack, the movement of the water pulls the milk into the crack and the diver marks the area to be repaired. The video documents the process to make it easier for us to return to the spot and make repairs. When divers recently tested the first half of the reservoir for leaks, no cracks were significant enough to attract the milk substance—a good sign!

To make sure the reservoir starts its long life water tight, we are repairing areas that show the potential for leakage. We inject grout deep into the hairline cracks to seal them, testing a second time to make sure filled every little space.

Park openings and closures

Visit the Explore Washington Park COVID-19 resource page for updated maps and information about Washington Park openings, closures, and safety.