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The City of Portland, Oregon

Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.

Customer Service: 503-823-7770


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Reservoir Management

There have been many changes to the Portland Water Bureau operations at Mt Tabor in the past couple of years, particularly with the disconnection of the open reservoirs from the water system. 

When the reservoirs were in service as part of the potable water system, they were typically drained and cleaned twice per year – once in spring and once in Fall.  Before cleaning, most of the water in the reservoirs was delivered to customers and to other lower-elevation reservoirs to limit the volume drained to the Bureau of Environmental Services collection system. Now that the reservoirs are no longer in service, new protocols for maintaining water in the reservoirs must be devised.

In July 2015 the Portland City Council directed the Water Bureau to work with the Mt Tabor Neighborhood Association (MTNA) in managing the quantity and quality of water in the Mt Tabor open reservoirs.

Together the Water Bureau and MTNA are developing a maintenance plan for the reservoirs that ensures their cleaning and draining has negligible impact on water quality; provides annual water use monitoring at each feature; and minimizes water use, in accord with City Council requirements for managing water features.

Reservoir Cleaning Schedule

The reservoirs at Mt. Tabor are drained and cleaned on a regular schedule to protect the quality of this non-potable water and conduct reservoir condition inspections.

Fall 2018ROV

Water Bureau Operating Engineers routinely inspect the reservoirs at Mt. Tabor using a Remote Operated Vehicle. During the last inspection in late August, crews discovered several leaks near the outlet between the north and south cells between the reservoir wall and floor. Water is very slowly seeping through these leaks, so they need to be repaired. 

The reservoir must be drained before these leaks can be repaired by a concrete contractor; however, the reservoir cannot be drained until the early October, when the Bureau of Environmental Services has completed repairs on the sewer pipe in which the reservoir will be drained. 

The leaks are very slow, and water levels in both cells will slowly drop. This means that the reservoir level may go below 85% full before it can be drained, as we would not keep refilling it at this dry time of year. Once it has been drained and repaired, it will also be cleaned before it is refilled.

Fall 2018

The schedule for draining, cleaning and refilling the reservoirs for Fall 2018 follows. The cycle of draining, cleaning and refilling takes several weeks. This work is weather dependent; if heavy rainfall is expected, the work will be postponed so as not to over burden the sewer system.



Reservoir 6

Reservoir 6 will not be cleaned until Spring 2020.

Reservoir 5

Reservoir 5 will go through its annual cleaning at the beginning of April 2019.

Reservoir 1

Reservoir 1 concrete liner maintenance begins April 2019 and will be completed by the end of the summer.