Earthquake faults worry Brightwater opponents

  • Lukas Velush<br>For the Enterprise
  • Monday, March 3, 2008 6:48am

WOODINVILLE — The more scientists learn about the faults that run under the future site of the Brightwater sewage treatment plant, the more plant opponents say they are justified in pushing King County to build it elsewhere.

In the past two years a combination of new and old technologies has allowed scientists to peer underneath trees, buildings and streets and for the first time see ruptures in the earth that prove there have been as many as three major quakes on the South Whidbey Island Fault in the past 3,000 years.

That’s what U.S. Geological Survey seismologist Craig Weaver told 50 people Monday, May 23 at an earthquake seminar sponsored by opponents of the $1.48 billion sewage treatment plant King County wants to build at Highway 9 and Highway 522.

To resident Richard Block, it adds up to one thing: King County didn’t do its homework before picking the south Snohomish County site.

“I wanted to hear from the experts about the potential impact from an earthquake,” said Block, who lives not far from the plant site in Woodinville. Weaver’s report “just confirmed that there’s a lot to this that King County probably didn’t look into before it decided to politically put that plant here.”

Weaver said the U.S. Geological Survey and others who study faults want to do more research on the South Whidbey Island Fault, something members of the Sno-King County Environmental Alliance interpret as meaning there’s more to know about the fault system – too much to allow King County to move ahead with a plan to build Brightwater on one, perhaps two, active faults.

“They were whipping right along, saying there wasn’t going to be a problem,” said Charley Blaine, an alliance board member. “The problem is, they still don’t know what they’re dealing with.”

King County officials disagree, saying they would build Brightwater to the highest available earthquake standards, ones that would allow it to survive a magnitude 6.8 to 7.3 earthquake the USGS projects for the fault line on the Brightwater site.

Last fall, a King County hearing examiner ordered the county to do a second environmental impact statement to make sure the plant would survive a major earthquake on the fault.

King County has made several changes since environmentalists forced it to take another look at the earthquake danger, said Christie True, Brightwater project director. The changes would limit the amount of damage that would occur if there were a large quake, she said.

“I think it’s improved the project,” True said, crediting the alliance. “It certainly has changed our thinking quite a bit.”

Changes include rearranging the site plan to get key structures away from a known fault at the north end of the site, as well as another that may exist at the south end.

King County has decided to use flexible connections on all pipelines at the facility, which would allow them to move instead of break during a quake.

It also decided to keep chemicals used to treat sewage in separate locations to reduce the chance they could mix and explode.

Still, the environmental review shows an earthquake on the fault system would be highly unlikely, said True, who called the probability of one happening “absolutely unlikely.”

“Even with the worst-case scenario, the public wouldn’t be harmed,” she said. “There would be some environmental damage.”

True said it’s too late for King County to find another site. King County is expected to outgrow its sewage treatment capacity about the time Brightwater opens in 2010, she said.

The second environmental review did not turn up anything that suggested moving the plant is necessary, she said. True added that final results of the review are due in July.

Construction on the 114-acre Brightwater site is on schedule to start by the end of the year. The treatment plant, which will serve south Snohomish and north King counties, is expected to cost $1.48 billion.

Scenarios in the supplemental environmental review show some circumstances in which Brightwater could be damaged by an earthquake.

If such an earthquake did happen on the one known fault on the north end of the site, the plant would sustain no damage, True said.

If a suspected fault on the south end of the property caused a quake, the pipeline bringing sewage to the plant and taking treated effluent to Puget Sound could break, possibly spilling sewage in a localized area. Otherwise, there would be no damage, True said.

Reporter Lukas Velush writes for The Herald in Everett.

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