In event of catastrophe: Study recommends Volunteer Park reservoir remain ready to serve Capitol Hill and beyond

22 million gallons of Cedar River water is waiting atop Capitol Hill (Image: CHS)

A recent study recommends that Volunteer Park’s reservoir will remain exactly that — a reservoir. Even if it were to stay unconnected to the city’s drinking water system, as it is now, the water could prove crucial in the event of a major earthquake. There is a 15-20% likelihood that such an earthquake will hit Seattle within the next 50 years.

Back in 2013, the city began studying the reservoir, along with one in Roosevelt, to see if it was still needed. Federal safety guidelines about protecting the water supply mandate expensive upgrades (basically putting a lid on it) in order to continue using the reservoir as a source of drinking water. So the city considered decommissioning it instead.


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While it usually has been full of water for the past five years, the reservoir is not connected to the city’s drinking water system. Over the six years since the studies began, a number of ideas have flown around for what to do with the space, assuming it would ultimately be removed from the system. The latest study makes it seem most likely that the reservoir will simply remain as it is.

Initially, Seattle Public Utilities had released only the executive summary of the study, citing safety concerns. But after a Seattle Times report and a number of experts questioned that reasoning, the majority of the study was released.

For study purposes, a catastrophic quake was defined as either a 7.0 earthquake along the Seattle fault, or a 9.0 along the Cascadia subduction zone. The Seattle fault runs east-west just a bit south of I-90. The Cascadia subduction zone is a north-south fault a few hundred miles off the Olympic Peninsula in the Pacific Ocean.

The study concluded that both the Volunteer Park and the Roosevelt reservoirs should stick around:

Roosevelt and Volunteer Reservoirs should remain part of SPU’s drinking water system. Since they are not covered reservoirs, recent regulations have determined that the water is nonpotable, which has resulted in both reservoirs being disconnected from the drinking water system. However, for emergency response purposes, the two reservoirs could be configured to provide emergency water. In the future, they may be upgraded to potable water reservoir standards.

The study goes on to paint a fairly bleak picture of what will happen to the city’s water system in the aftermath of catastrophic earthquake. Even though Seattle Public Utilities has spent $100 million over the last 30 years performing seismic upgrades to the water system, there’s still a long way to go. The water system is expected to lose pressure with 16-24 hours after the quake. It could take as long as eight weeks or more to restore the system fully.

Capitol Hill will be among the first areas to lose pressure. No matter how severe the quake, gravity will still work, and water will still flow downhill. So higher elevations in the city will be the first to notice the absence of pressure.

The problem, in general terms, is that if a pipe ruptures, water will leak out of it, and since the pipes are largely connected, it will keep flowing until all of the water above it drains out. Since a major quake will likely rupture a number of pipes, it would create multiple points where the water would drain. Moreover, the pipes bringing the water to Seattle from the Tolt River, pass through vulnerable areas and would also be likely to break, cutting off the supply at the source.

Keeping the Volunteer Park and Roosevelt reservoirs full of water, even if it’s not technically drinking water, could help during the first hours after a quake. The study notes that the extra water, about 20 million gallons in Volunteer Park and 50 million in Roosevelt, could delay the loss of water pressure by as much as 10 hours. Those extra hours could be critical, particularly for fighting fires expected immediately after an earthquake.

It’s not always full of water. In 2013, the reservoir was emptied for cleaning (Images: CHS)

Additionally, the water could be routed into the drinking water system in an emergency. Technically, the city would need to issue a notice to boil water if it tapped into the Volunteer Park Reservoir. However, in the event of a major earthquake, such a notice would likely be issued anyway.

The study recommends spending the coming decades retrofitting key points of the infrastructure to help reduce that eight-week timeline. It could cost $40 million to $50 million over the next 15-20 years, and another $800 million over the next 50 years, with still more expenses in the decades following that. Some of that money could go toward isolating the Volunteer Park Reservoir so it could better hold onto its water.

Part of those expenses could also include a more in depth study of the Volunteer Park Reservoir. The study states:

The geotechnical investigation and assessment needed to assess the seismic vulnerability of Volunteer Park Reservoir was not performed as part of this study. If Volunteer Park Reservoir is returned to service, a comprehensive assessment that incorporates the current understanding of the seismic hazards and geotechnical response should be performed.

If all this has you feeling a little shaken, be sure to check out the city website with tips on how to prepare for a disaster. Preparedness guidelines generally call for one gallon of water per person, per day (among a bunch of other supplies). And to expect that you could be on your own as far as food and water for seven to ten days.

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