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Reservoir Covering Program

Beacon Reservoir / Construction of Jefferson Park in 2009

Program overview

Seattle’s reservoir program was first formulated in the mid-1990s in response to a Washington Department of Health Drinking Water Quality rule. A key driver of the program has always been public health protection and improved water quality. The initial plan was to cover the majority of the reservoirs with floating covers. The opportunity for new public open space and the additional security advantages led to the approach of undergrounding the remaining in-city reservoirs to be kept in the system. In 2004, the City Council approved the plan to replace Beacon, Myrtle, Maple Leaf and West Seattle reservoirs at $150 million. A federal drinking water regulation, adopted in 2006 that required all uncovered drinking water distribution reservoirs to either be covered or treated to a high standard, placed additional priority on eliminating all remaining uncovered distribution system storage.

Seattle Public Utilities (SPU) has replaced six of its open reservoirs with underground structures that will improve the quality and security of our water supply. The reservoir covering program also provided 76 acres of new open space. Reservoirs that have been replaced with underground structures include Magnolia (1995), Lincoln (2004), Myrtle (2008), Beacon (2009), West Seattle (2010) and Maple Leaf (2012).

Seismic retrofits for covered reservoirs

In March 2011 project designer MWH informed SPU that MWH had made a mistake in their seismic calculations, and four covered reservoirs might not comply with building code. Since then, SPU has been conducting its own seismic analysis of the projects, and—though there is no danger of catastrophic failure—it is likely that all four reservoirs will require some seismic retrofits to bring them up to code. MWH has been cooperating with SPU and has already made some payments toward repairing the structures. The overall program is still expected to come under or at budget, and utility rates will be unaffected by the retrofits.

Open space

As part of the program, SPU covered the reservoirs with grass and other low-maintenance plants so that communities can use the new open space immediately.

Seattle Parks and Recreation (Parks) is working to transform the new open space at the West Seattle and Maple Leaf sites into full-fledged parks. For more information about Parks’ master planning process and completed projects, please see links to the Seattle Parks and Recreation website at the bottom of the page.

Remaining above-ground reservoirs

The City has four remaining above-ground reservoirs: Bitter Lake, Lake Forest Park, Volunteer and Roosevelt Reservoirs.

Floating covers were installed at Bitter Lake and Lake Forest Park reservoirs and these covers will remain in place through the operational life of the facilities. SPU has increased security at these facilities.

SPU is evaluating whether to decommission Volunteer and Roosevelt reservoirs and is currently conducting a two-year decommissioning test at both reservoirs. To perform the tests, the reservoirs were taken out of service on April 1, 2013. While out of service, Roosevelt Reservoir will be kept drained, while Volunteer Reservoir will remain full with water and continue to be a water feature at the park.

The reservoirs will remain disconnected from the City’s drinking water system throughout the two-year test. During this time, SPU will study the impact the out-of-service facilities have on Seattle’s overall drinking water system, make evaluations and determine whether the reservoirs can be permanently taken out of service.

A public notice (pdf) about Roosevelt Reservoir being taken out of service was sent to residents living in the Roosevelt neighborhood. View answers to some frequently asked questions (pdf) about Roosevelt Reservoir’s decommissioning test.

Contact information

For questions about the Decommissioning Test, contact Cyndy Holtz at (206) 386-1990 or

For questions about the Reservoir Covering Program, contact Stephanie Murphy at (206) 386-9778 or

Related links

Maple Leaf Reservoir Parks and Green Spaces Levy Project
Jefferson Park Master Plan
West Seattle Reservoir Parks and Green Spaces Levy Project
Myrtle Reservoir Development Pro Parks Project
Washington State Department of Health Office of Drinking Water
Reservoir Undergrounding – Ordinance 121447
Funding of Reservoirs and Parks – Ordinance 120899