The Washington Transportation Department admits mistakes have been made in the construction of pontoons for the new Highway 520 floating bridge across Lake Washington between Seattle and Bellevue.

The department announced Tuesday that it is making repairs and design modifications to ensure a 75-year life of the bridge.

The changes are the result of findings by an expert review panel that was convened last year to review cracking in the first pontoons built in Aberdeen

The department says the panel agrees the pontoons are structurally sufficient. But the panel found the department did not follow standards of good practice to validate the pontoon design elements and did not strictly follow protocols for oversight on the construction site.

A total of 77 pontoons will make the world's longest floating bridge.