Preparedness

Seattle, Suburbs Would Lose all Water Pressure Within 24 Hours of Catastrophic Earthquake, City Study Says

The study says a disaster on par with the 2011 quakes in Christchurch, New Zealand, and Tohoku, Japan, would cripple the regional system operated by SPU. Restoring the water system to pre-earthquake conditions would take years.

by JiDaniel Beekman and Sandi Doughton, The Seattle Times / December 3, 2018

(TNS) - The ground would stop shaking. Then the water in the pipes would drain away.

As Anchorage grapples with the aftermath of Friday’s powerful earthquake, a new study says Seattle would lose all water pressure within 24 hours of a catastrophic quake and would need at least two months to entirely restore water service in the city. Suburbs served by Seattle Public Utilities (SPU), which commissioned the study, would also lose service – including Bothell, Woodinville, Kirkland, Redmond and Bellevue.

With Seattle facing 15 to 20 percent odds of a severe earthquake in the next 50 years, the study says the city should spend $850 million through 2075 to mitigate water-system risks posed by the “Big One,” playing catch-up to California cities that already have taken dramatic steps.

“For this very catastrophic earthquake, we’re looking at very significant impacts,” said Alex Chen, SPU’s water-planning director. The utility provides drinking water to 1.4 million people.

The study says a disaster on par with the 2011 quakes in Christchurch, New Zealand, and Tohoku, Japan, would cripple the regional system operated by SPU. Restoring the water system to pre-earthquake conditions would take years.

The magnitude 7 quake that struck near Anchorage on Friday morning was a less-damaging type than Seattle’s worst-case scenarios because it originated 25 miles underground. Even so, it buckled roads, cut off electric power, ruptured hundreds of gas lines and broke water pipes across the city. Train service was shut down after burst pipes flooded the Alaska Railroad Operations Center, and the Anchorage water utility advised all residents to boil water in case of contamination.

Scott Miles, a University of Washington disaster risk-reduction expert, hailed the SPU report but warned the cost estimate could be low. Miles said City Hall leaders will need to show backbone. While the projects may inconvenience the public, “the real disruption” would be water service getting knocked out by a quake, he said.

“Like in Christchurch, this means using portable toilets not just for days, weeks or months, but in some cases years,” Miles said. “Imagine having to pee at 3 a.m. and having to walk out your front door to use the honey bucket on the sidewalk … That’s how important it is to deal with this problem now.”

SPU paid five consultants $900,000 for the 722-page study, which took more than three years to complete. But the only information the utility is releasing to the public is a 13-page summary, raising questions about transparency.

“It’s very disappointing to hear that SPU is not being forthcoming,” Miles said. “The majority of the analysis is not sensitive enough to keep hidden.”

Chen said the secrecy is necessary because some portions of the report contain information about vulnerable points in the water system.

The analysis examines the impacts of a magnitude 7 earthquake on the Seattle Fault and a magnitude 9 quake on the offshore Cascadia Subduction Zone. Between 1,400 and 2,000 pipeline breaks are likely, the summary says, particularly in areas like Sodo and Interbay where loose soils can liquefy and shift.

Those breaches, combined with potential problems at SPU pump stations, reservoirs and elevated tanks, likely would result in SPU’s direct-service water system losing pressure in 16 to 24 hours.

Every Seattle neighborhood would lose tap water for drinking, showering, flushing – and firefighting.

Most serious would be leaks and breaks in the large transmission pipes, some more than 100 inches in diameter, that move water from SPU’s mountain reservoirs in the Cedar and Tolt watersheds to the cities.

Repairs to the system’s smaller distribution pipes, which carry water to customers, could start almost immediately. But as many as eight weeks would pass before SPU could start repairs to transmission pipes at underground river crossings and on steep slopes, according to the study.

The transmission-pipe problems would render SPU unable for more than three weeks to start supplying water again to most or all of its suburban customers, according to the utility. The study didn’t even look at what would happen to distribution pipes in the suburbs.

“It’s likely that we’ll lose either the Cedar or Tolt transmissions systems or both,” Chen said. “That the Eastside supply line might not be available to us. That we’ll have significant distribution-pipeline failures.”

The analysis does not include Seattle’s sewer system, which is owned and operated partly by SPU and partly by King County.

Secrecy questioned

SPU is citing a U.S. Department of Homeland Security “Protected Critical Infrastructure Information” designation in keeping the entire study, including the table of contents, secret. SPU sought the designation to ensure that the report “is not subject to public disclosure,” according to a September email to Homeland Security from SPU water-system seismic program manager Bill Heubach.

Other utilities, including the Los Angeles Department of Water and Power and Oakland’s East Bay Municipal Utility District, have taken a more transparent approach with their seismic analyses, making most information public and only withholding sensitive sections.

Former Washington Emergency Management director Jim Mullen said the extreme secrecy “makes no sense.”

SPU is asking for an enormous investment and the public deserves to know more about what the utility intends to do with that money and how the cost estimates were developed, Mullen said.

“It seems to me there’s no good reason not to share the whole thing and just block out those things that are really sensitive concerns,” he said.

Responding to questions from The Seattle Times, SPU has asked Homeland Security whether portions of the study could be released, said SPU spokesperson Ingrid Goodwin.

Growing knowledge

The last analysis of earthquake damage to Seattle’s water system was conducted in 1990, before the dangers posed by the Seattle Fault and the Cascadia Subduction Zone were understood. Since then, SPU says, it has spent more than $100 million on seismic upgrades to pump stations, elevated tanks, some pipelines and underground reservoirs.

But the city still has a long way to go to protect its water system from devastation, the new study says.

The city’s newer reservoirs, such as those under Jefferson Park and Maple Leaf Park, can be expected to hold up well. But SPU’s pipes, which are an average of 70 years old, would be subject to intense shaking, liquefaction, landslides, settlement and ruptures that could result in permanent ground displacement ranging from a couple of inches to more than 10 feet, the study says.

In a Seattle Fault quake, the shaking could last 15 to 40 seconds and be six times as strong as during the 2001 Nisqually quake. In a subduction quake, the shaking won’t be as intense but will last several minutes.

SPU’s consultants used seismic-hazard maps to identify areas where permanent ground displacement likely would occur, and visited those areas to judge whether the pipes would break.

They determined upgrades are needed in a number of locations, including sites where transmission pipes cross under the Cedar, Duwamish and Green rivers.

“It is likely that both earthquake scenarios would have a significant impact on the major transmission pipelines,” the study summary says.

The consultants analyzed the distribution pipes separately, determining about 2,000 repairs would be needed after a Seattle-fault quake and about 1,400 after a subduction quake. That’s consistent with what happened in 2011 in Christchurch and Tohoku, Chen said.

In addition to Sodo and Interbay, the areas most vulnerable to distribution-pipe breaks caused by liquefaction or landslides include Alki, South Park and Rainier Valley.

SPU would try to keep water from draining out of reservoirs by shutting valves, Chen said. Those reservoirs could be a source for firefighting in the immediate aftermath of the quake, he added.

Investments needed


Were a catastrophic earthquake to hit today, SPU would need 18 to 35 days to restore water service to 70 percent of its direct-service customers and as many as 80 days to restore service to all of those customers, according to the study.

The recommended upgrades would allow the utility to maintain service for some customers after a severe quake and to restore service more quickly, the study says.

If all the fixes are made by 2075, service to 70 percent of direct-service customers could be restored in 11 days, with all of them back online within 45 days.

But the work would be expensive, including an estimated $217.5 million in transmission-pipe upgrades and $322 million in distribution-pipe upgrades.

SPU recently installed quake-resistant distribution pipes for the first time, laying them along three blocks of First Avenue in downtown Seattle.

The Japanese-style pipes have special joints that rotate and telescope during earthquakes to prevent breaks. They cost twice as much as regular pipes and also are more expensive to install, according to the utility.

Under a project schedule accompanying the study, SPU would start slowly. The utility would spend less than $10 million by 2023, mostly to design large-scale upgrades and stockpile materials needed for repairs.

From then, SPU would spend $15 million to $20 million per year, initially working to install quake-resistant transmission pipes in at-risk locations.

“What we’re trying to do is prioritize the most important upgrades … and then spread out some of the less critical upgrades,” Chen said.

For now, the utility is committed to a six-year business plan approved by the City Council last year. That plan will be updated in 2020.

The political challenge will be balancing earthquake risks against what ratepayers can stomach. The monthly cost of water, wastewater, solid waste and drainage at a typical Seattle house is set to reach $248 by 2023, up from $181 in 2017.

Seismic upgrades aren’t the only projects driving up water rates. Moving ahead, SPU expects to spend about $60 million per year on other kinds of water-system capital projects.

“We need to do these seismic upgrades,” SPU general manager and CEO Mami Hara said when asked about potential pushback from ratepayers. “I can’t see our community kicking back and saying they don’t want to have a resilient system.”

Seattle lags many California water utilities in earthquake preparedness. As part of a $4.8 billion bond measure, San Francisco bored a quake-resistant water tunnel under San Francisco Bay and built a new supply pipeline designed to flex when faults slip. Oakland has invested $350 million in upgrades, including quake-resistant pipe, dam improvements and a seismically sound tunnel across the Hayward Fault, while Los Angeles has launched upgrades to vulnerable aqueducts that cross the San Andreas Fault.

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