State transportation officials announced on Tuesday afternoon that the I-90 floating bridge would reopen in the early hours of July 18, nearly 10 days ahead of their original schedule.

WSDOT said in a Web site update that construction crews working on the westbound lanes of the I-90 floating bridge made quicker-than-expected progress over the weekend installing new expansion joints on the Homer Hadley Bridge. The repaired westbound bridge expanse will be reopened by 5 a.m., Saturday morning.

One more major piece of the construction work remains, however: Crews will close all but one westbound lane of I-90 on Friday night to re-stripe lanes on Mercer Island and in Seattle.

Last week, as I-90 westbound traffic slowly went from bad to worse and backed up onto Mercer Island streets, WSDOT reported that they had avoided the nightmare scenario.

They said commuters seemed to be heeding their advice and staying home, telecommuting, taking alternate routes or leaving for work before 6 a.m. during the work week. Officials had feared traffic delays of up to an hour for the Issaquah to Seattle drive, but long traffic jams never happened.

Speaking on July 8 during a media event at Mercer Island’s Lid Park, WSDOT Assistant Regional Administrator Russ East said the reduced number of motorists on the roadway has kept traffic levels tolerable.

“There’s no question the traffic is heavier, but it’s much better than we anticipated,” he said. “The public is doing a great job.”

The early finish is great news for commuters, but WSDOT spokesperson Jeff Switzer said he still hoped drivers would continue to try and avoid the peak rush-hour times if they had to use the bridge, if only for a few more days.

“Since the [July 4] holiday weekend, commuters have been evaluating their choices,” he said. This Monday morning, more and more drivers were settling for I-90, pushing drive times up to 35 minutes between Bellevue and Seattle.

East also commended the increase in bicycle commuters, whose numbers he estimated had reached 1,500 to 2,000 riders per day on the bridge.

Mercer Island motorists headed to Seattle faced their own traffic twist due to the construction as traffic backed up into the Mercer Island business district by motorists seeking to use the 77th Avenue on-ramp detour, causing delays. Switzer advised using the Island Crest Way express lane on-ramp to save time.

Late in the evening on July 10, construction teams replaced the two 65-ton expansion joints when their replacements arrived on the “Los Angeles,” a barge fitted with a massive crane. Next up for the repair crews is installing rebar and pouring the concrete to hold the new joints in place.

Engineers hadn’t predicted the amount of stress that the joints would bear when the Homer Hadley I-90 floating bridge was built in 1991, forcing constant maintenance and welding of the weak points. When the cracks started appearing faster than they could be repaired, WSDOT decided to replace them. An expansion joint failure could cause the metal plate to shift upwards on the roadway as high as eight inches, Switzer said.

Morning traffic

According to WSDOT, morning commute traffic was a little heavier than typical. Between 8 a.m. and 8:30 a.m. on Monday, it took 35 minutes to get from Interstate 405 to Interstate 5, about 20 minutes longer than usual. Traffic was a bit heavier on alternate routes like SR-520 and I-405.

Evening traffic

Westbound SR-520 remained heavy throughout the afternoon, but despite a 7 p.m. Mariners home game and no express lanes last week, the peak travel time on westbound I-90 was just under 30 minutes, about seven minutes longer than usual. Eastbound I-90 travelers had no delays.

Progress on the job

After moving and leveling the joints into place, construction teams will pour concrete as a final step. The repairs may conclude before the July 20 deadline.

What can drivers do?

• Plan for 30- to 60-minute delays on I-90.

• Check the Web for the latest information at www.wsdot.wa.gov/construction/2009/today.

• Check the Seattle traffic map to pinpoint and avoid congestion: www.wsdot.wa.gov/traffic/seattle.

• Use the overhead freeway signs and the 5-1-1 driver information line to get up-to-the-minute information on the road.

• Call the WSDOT I-90 information hotline at (206) 440-4444. The hotline is staffed from 8 a.m. to 5 p.m., weekdays. Leave a message, and your call will be returned.

• WSDOT has been communicating with drivers using twitter: http://twitter.com/wsdot.

For the latest information on I-90 delays, visit the MI Reporter.com’s dedicated I-90 Bridge Closure – Full Coverage link.