In February 2014, a 20 metre long, 5 cm wide crack was found on the upstream side of a pier in the spillway of the Wanapum dam in Washington State. As an emergency measure, the Grant County Public Utility District, which operates the dam, lowered the level of the reservoir by eight metres to reduce pressure on the structure.
In May 2014, it awarded the contract to repair the dam to Soletanche Bachy’s North American subsidiary Nicholson Construction. Nicholson began by coring the dam from the drainage gallery to map the crack. It then installed 35 vertical anchors with a maximum capacity of 1,000 tonnes on each of the 13 dam piers to stabilise the dam and reinforce the spillway.
This part of the project was completed in November 2014 following 10 months of uninterrupted work. It ended with the installation of uphole drains in the gallery, drilling, installation of 69 bars on the ogee and grouting to plug the crack.