Contractors recently noticed condensation leaking through the concrete lids covering West Seattle’s Myrtle reservoir and Beacon Hill’s Jefferson reservoir. While the water supplies were not contaminated, the waterproof seals covering each reservoir will need to be replaced.

Shortly after Sept. 11, 2001, Mayor Greg Nickels ordered that all open water reservoirs be covered. Since then, Seattle Public Utilities (SPU) has been replacing its open reservoirs with underground structures to improve the quality and security of the city’s water supply and provide 76 acres of new open space.

A thick concrete lid has been placed over these reservoirs covered by a waterproof seal on top of which soil and grass lie. It is the waterproof seals that have been found defective at the Myrtle and Jefferson reservoirs.

While Cornell Amaya, spokesperson for SPU, emphasized that there are no public health risks caused by the leaks, the waterproof seal is necessary to maintain the stability of the concrete. While the defective seal was made of a material called procore, the new seal will be made of a rubberized asphalt.

The soil and grass covering the lids has been removed so that the waterproof seals can be replaced.

The cause of the leaks has not been determined, but Amaya said blame will likely fall on the contractor, Mid-Mountain, or the designer.
They will also be held responsible for the financial costs of replacing the waterproof seal.

A lid to cover the Westcrest reservoir has not been completed, but Amaya said that procore will not be used at that park.

According to Amaya, all the city’s open reservoirs are supposed to be covered by December, but he has not determined if the project’s completion will be delayed by the leaks.

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