Finding an active earthquake fault under the Brightwater sewage treatment plant site is not reason enough to build the plant somewhere else, King County officials said Tuesday.
Pending a stamp of approval by King County Executive Ron Sims, expected in about a week, King County expects to begin building the $1.48 billion sewage treatment system soon.
Last fall, a hearing examiner found that King County had failed to adequately assess earthquake dangers at the 114-acre Brightwater site off Highway 9 near Highway 522 in Maltby.
King County was required to do a second environmental review of the project, focusing on the earthquake danger.
King County on Tuesday released that environmental review, which claims that it’s safe to build the plant on one known fault and a possible second fault.
The known fault is at the north end of the Brightwater property, where no structures are planned. The possible second fault is believed to run through the south end of the property, crossing a tunnel that would bring sewage into the plant and send treated water out.
The faults are part of the south Whidbey Island fault system, which stretches from southern Whidbey Island across most of south Snohomish County.
“What we have done is design the facility to withstand a lot of shaking,” said Christie True, Brightwater project director.
She said there only have been three earthquakes on the known fault in the last 16,000 years. “It’s extremely unlikely that anything will happen,” she added.
If an earthquake does occur, King County’s study said the treatment plant could survive an earthquake of magnitude 6.8 to 7.3 with little damage. That’s what the U.S. Geological Survey projects is likely on the fault system.
Brightwater critics did not have a chance to review the document Tuesday, but said they would look at it closely before an Aug. 5 deadline for appeals passes. They have questioned Brightwater’s earthquake safety in the past, pointing out that King County used proximity to earthquake faults as a way to rule out other sites earlier in the siting process.
“We have to go through it with a fine-toothed comb,” said Corinne Hensley, a spokeswoman for the Sno-King Environmental Alliance.
It was the group’s appeal of the first environmental review that forced King County to do a second review.
Once Sims signs off on the study, King County will start working on the 18-foot diameter sewage tunnel.
Construction on the treatment plant itself can’t start until King and Snohomish counties agree on what role Snohomish County will have in overseeing the project.
Snohomish County wants a public process that allows residents to weigh in with their concerns. King County wants guarantees that Snohomish County won’t put costly restrictions on the project.
Negotiations to sort it all out are scheduled to start next week.
“I believe we’re ready to have a fair and open conversation about the whole process,” said Gary Nelson, chairman of the Snohomish County Council.
Reporter Lukas Velush: 425-339-3449 or lvelush@heraldnet.com.
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