Spokeswoman Meagan McFadden in Yakima said traffic will be directed through the washout area by portable lights.
She said the contractor will have to bring in a lot of fill to replace ground that gave way Tuesday following heavy weekend rain.
The 500-foot long washout is three miles east of the White Pass summit. A 45-mile stretch of highway between Packwood and Naches is closed.
The department plans a temporary fix with a permanent repair next spring.
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