Washington State Department of Transportation officials are warning commuters that when it comes to the July closure of some lanes on the Interstate 90 floating bridge, they should prepare for the worst.

WSDOT officials attended the Tuesday, May 26 Issaquah City Council Committee of the Whole meeting to speak about how the May closure went, what lessons were learned, and what drivers should expect come July.

“If you thought it was bad in May — unless a significant number of people change their (travel) habits — July is going to be far worse,” said Russ East, WSDOT assistant regional administrator.

As in May, the work will only affect westbound traffic, headed from Issaquah and Sammamish into Seattle.

But back-ups, and drivers searching for alternate routes, will create the likelihood of increased traffic on Interstates 405, 520, and other roadways.

The westbound mainline will be closed beginning July 5 for up to three weeks.

All westbound traffic will use the center roadway.

Crews will be replacing the expansion joints at both ends. During that time, traffic will be funneled into the center express lanes, cutting travel space down to two lanes.

With a typical daily volume on I-90 of 70,000 drivers — about 2,800 vehicles per hour — the closure will make for a long commute, East estimated.

He said drivers headed from Issaquah to Seattle should expect the trip to take well over an hour.

However, WSDOT is looking into some options that could decrease construction time by one week. Those options include sending the contractor out to do pre-work before the project begins and having crews work longer hours, for instance.

But those options aren’t cheap.

“There’s a premium cost involved for doing that,” East said. “We’re working hard, but it really comes down to a time and money discussion with the contractor.”

Crews were able to finish the May project a week early by working 24 hours a day and instituting competitions and incentives for hitting certain marks, East said.

WSDOT is also encouraging people to carpool by offering three months of free vanpool service for those who sign up by June 8. While there are no HOV lanes available and carpooling won’t decrease anyone’s travel time, it will help with the overall congestion by reducing the number of cars on the road.

When asked by Council members for ways to avoid the congestion, East had two suggestions: take a vacation, or extend your work day.

During the May closure, traffic built tremendously from 7-7:30 a.m., and didn’t begin to wane until after 7 p.m. Drivers who have to use I-90 should leave before 6 a.m. and come home after 7 p.m., he said.

Weather conditions also played a huge part in traffic times; even with the same number of cars on the road on a sunny and rainy day, the rainy-day commuters will spend substantially more time behind the wheel.

“There’s a number of environmental factors that are beyond our control that … can nearly double traffic times.” East said.

But as the project progressed and drivers began to adjust their travel habits, congestion did improve, he said.

Encouraging drivers to avoid I-90 and carpool will be some of the most important steps to making the July commute smoother.

“We really need the public to understand how their own individual travel choices effect the entire region,” East said. “And much more now with this closure than probably any of the closures we’ve had before. This has the potential to be more significant than when we closed I-5 down to two lanes.”

For more information on the project, go to www.wsdot.wa.gov.