The Washington State Dept. of Transportation hasn’t had the best of news concerning its two mega-projects recently. Not only is its 57.5-ft-dia. tunnel-boring machine, Bertha, in its second month of sitting stuck under Seattle just 1/10th of the way through its job, but the most recent change orders and projected fixes required for the State Route 520 floating bridge replacement show that project has eaten up its entire reserve and will need about another $170 million.

WSDOT will request the state’s Legislature to change the program’s budget from $2.72 billion to $2.89 billion.

The agency’s own pontoon design error churned through the bulk of the project’s $250 million risk reserve. An additional change order associated with the pontoon design error is expect in the next month, WSDOT says, and will likely bring the total coast associated with the mistake to around $200 million.

“The original pontoon design included an unfortunate and costly mistake,” says WSDOT Transportation Secretary Lynn Peterson.

Combine the 2012 mistake with signed or identified expected change orders worth $134.3 million for other construction in the larger State Route 520 corridor project and other, smaller change orders and WSDOT is already planning to raid existing funding sources to cover the costs and keep the project moving.

WSDOT, in a release, says “most of the needed construction funds can be obtained from available SR 520 toll bonding capacity, with other existing agency resources providing the remaining funds, dependent on legislative approval.”

In 2012, WSDOT announced four of the original pontoons constructed to replace the existing 50-year-old floating bridge—the world’s longest floating bridge—required repairs. In addition, all remaining pontoons required either modifications or an updated design. The final fixes should come this spring and push the opening of the new bridge into early 2016.

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for TIME, Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.