SEATTLE (AP) After weeks of warnings, the state Department of Transportation has begun construction on a stretch of Interstate 5 through Seattle that could back up traffic for 30 mi. (48 km) in a worst-case scenario the night of Aug. 10.

Crews began working late in an area between Spokane Street and Interstate 90, just south of downtown Seattle. Besides repaving 1.13 mi. (1.8 km) of northbound I-5, they will replace or repair deteriorating expansion joints that connect concrete freeway deck slabs.

Work crews are expected to work 12-hour shifts, seven days a week, through Aug. 29.

In the first stage, scheduled through early Aug. 13, two of the four northbound lanes were closed, along with four freeway ramps. There was no access to eastbound Interstate 90 from northbound I-5.

As of Saturday night, DOT officials reported that work was progressing well, and traffic was flowing with only occasional slowdowns and minor backups. Drivers apparently took the warnings to heart and used alternative routes, as engineers estimated that traffic on the stretch of freeway was approximately 60 percent lighter than a normal.

However, rain showers were forecast for Aug. 12. The contractor planned to use a giant, trailer-mounted blow dryer to dry the roadway if rain fell, so paving material could be applied.

Traffic engineers, communication specialists and other transportation experts were gathered at a conference room in the north Seattle suburb of Shoreline to collect data and make decisions to keep traffic flowing as smoothly as possible.

“This is kind of like the brain of the system,” regional administrator Lorena Eng said Aug. 10.

The operations center includes seven computers, 13 phones and several video monitors in a conference room usually used for board meetings. All information coming from the news media, the public and government agencies will be monitored in the conference room.

Also in the building is DOT’s traffic management center, which uses 44 video screens and 35 computers to monitor traffic. Engineers in the traffic center can update reader boards and change the timing of ramp meters to suit traffic conditions.

“When you’re driving and you look up and you want to know, ’Why is this congestion in front of me?’ these are the people who are posting the messages,” said DOT spokeswoman Lauren Penning.

Another addition is a phone bank answering questions from the public.

The big challenge was expected to come on Aug. 13, the first full commute day of the project.

More ramps will open during the second stage, and drivers will be able to travel eastbound onto I-90.

During the remaining three stages, from Aug. 18 to Aug. 29, as many as three lanes will be closed on the left side of the freeway, potentially narrowing it to just one northbound lane.

The speed limit through that segment of freeway will be 45 mph during the entire project. There will be no high-occupancy-vehicle lane in the construction zone.

To keep traffic flowing, Washington State Patrol dispatchers will be able to send tow trucks to collisions and disabled vehicles before troopers actually arrive at the scene.

The State Patrol Aviation Section also will use several of its video-equipped aircraft to help the Transportation Department and troopers in King County monitor traffic on the freeway and surface streets.

“We’ve been planning and gearing up for this for a long time,” Trooper Jeff Merrill said.

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