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.
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Overview
Over the past few months, crews have continued the process of filling the two parts of the reservoir, testing for leaks, and repairing small cracks. Crack repair is an anticipated step with the construction of any large concrete project and this work will continue through April.
In addition to the ongoing repair and testing for leaks, crews are pouring concrete for vents, and installing electrical conduit, mechanical devices, and guardrails.
In April or May, we will disinfect the pipelines that serve reservoir along with the tanks using a low-level bleach solution which kills any existing bacteria. Later this spring, the reservoir will begin serving water to the public.
Intermittent closures of Madison Trail
Our contractors are accessing some pipes and valves buried near Madison Trail to get the reservoir ready to start serving water. In order to keep people safe from construction trenches and heavy equipment, the trail will be closed intermittently through June.
More information about the leak testing process
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!
We're making sure the reservoir starts its long life water tight, so 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 we 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.