The new cost for repairs to make the West Point Treatment Plant fully operational is now close to double the initial estimates, hitting an estimated $49 to $57 million.
It is expected costs for the plant's repair will be covered by a $250 million insurance flood policy, but the county will be on the hook for the policy's $250,000 deductible.
Insurance also won't cover any fines state regulators impose on the county for violating its discharge permits into Puget Sound.
All the repair work should be completed by the end of the year.
Repairs are necessary after a pump failed early in the morning February 9 and dumped an estimated 150 to 200 million gallons of untreated sewage and stormwater into Puget Sound. At the time, officials said the pump failure set off a chain reaction of problems at the plant, which effectively shut it down.
A similar, smaller incident happened during a heavy rainfall the week of February 18.
It took until last week for the plant to come back online enough to meet its permit requirements for what is discharged into the sound.
"Our number one priority was getting that plant back online and protecting public safety and the environment and we did that," Mark Isaacson, director of King County's wastewater treatment division, said.
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