Reporters check out expansion joints in the Interstate 90 bridge over Lake Washington.

In fact, there are dozens of cracks that have so worried engineers that the state Department of Transportation has decided to close large sections of the bridge for at least two months this summer.

A state DOT employee climbs below the I-90 floating bridge deck to inspect for cracks and other problems

The expansion joins connect the shore structure of the bridge to the floating section of the bridge. "These joints allow the bridge to go up and down with the water level," says Phelps.

But the extension joints on the express lanes and the westbound bridge have been showing their age.

Project Designer Ralph Dornsife says, "The existing joints that were on the bridge were modular joints, and they were not designed for fatigue."

Cracks in the joints began appearing soon after they were installed 20 years ago. But now those cracks are so numerous they cannot be repaired.

Dornsife says if one of the joints broke "you would end up with gaps in the roadway which could obviously present safety issues to motorists."

Phelps predicts something even worse.

"If we don't replace these now they could pop up and create an accident," he warns.

A crack can be seen in one of the joints underneath the I-90 floating bridge deck.

"It is going to be challenging for drivers," he says. "You are losing the express lanes for three weeks in May, losing the outer (westbound) roadway for three weeks in July."

The state has done traffic analysis and is predicting if no one changed their driving patterns during those two months commute times between Bellevue and Seattle could double, triple - even quadruple.

"When we shutdown the express lanes in May, you can expect to add roughly a half-an-hour to your commute. When we shut down the westbound outer roadway in July, you can plan on adding about an hour to your commute," predicts Phelps.

Even those drivers who don't use the I-90 bridge should prepare for an impact.

The 520 bridge is already crowded most mornings and evenings. Engineers say it cannot handle any excess traffic.

King County Metro bus lines too are operating largely at capacity and don't have much room for new riders. Going around the lake north of south could be an option, but those roadways are also already heavy during peak hours.

"If you are driving, carpooling, or riding the bus anywhere in the great Seattle metro area you need to plan ahead," says Phelps.

Mike Murphy with the state DOT says workers should consider telecommuting, taking vacation, biking or using vanpool.

"We're asking people to consider starting a new vanpool. Thanks to grant money, Metro is working on a special offer that could allow some reduced cost options for doing that," says Murphy.

The entire project is estimated to cost $8.33 million, but contractors have $80,000-per-day incentives to finish quickly.

Luckily, none of this work is weather-dependent, so predicting a finish date is easier. By the beginning of August, Dornsife hopes the work will be finished.

"We expect the new ones to last for the remaining lifetime of the structure (50 years)."

For more information, go to this DOT website: www.wsdot.wa.gov/projects/i90/homerhadleybridgerepair/