Crews will also remove more than 70 creosote-treated timber piles from Bone River and restore an estimated 82 square feet of streambed.
The Bone River Bridge is located on Willapa Bay, about three miles north of the Bay Center peninsula, and carries an average of 2,700 daily drivers.
The $8.8 million project is scheduled for completion in 2014, and is the first of four bridge replacements planned for Pacific County.
Later this year, WSDOT will start work on three new bridges – on US 101 at the Middle Nemah River, and on SR 105 at Smith Creek and North River.
All four projects are funded through the 2005 gas tax package and pre-existing state funds.