The clock is ticking on the biggest high construction closure ever.

On Aug. 10 crews of the Washington State Department of Transportation will close multiple lanes and ramps on northbound Interstate 5 between Spokane Street and I-90 around the clock for 19 days to perform extensive rehabilitation work on the freeway.

This closure will dramatically affect traffic in the greater-Seattle area. Transportation officials are asking drivers to make a plans to avoid the area and not get stuck in traffic backups.

During the 19-day closure, crews will break apart and remove 34 failing expansion joints that link the concrete bridge slabs that comprise this 40-year-old freeway section. If these expansion joints completely fail, large pieces of metal and three-foot-long bolts would pop up from the freeway deck and lead to potentially deadly collisions. Crews will also pave northbound I-5 between Spokane Street and I-90.

Transportation officials want to cut the number of vehicles on northbound I-5 just south of downtown by more than 50 percent to help prevent gridlock. Unless drivers help, traffic engineers expect severe congestion on I-5 from 4 a.m. to midnight every day. The worst-case scenario would be backups from downtown Seattle to Tacoma.

The transportation department has been preparing for this closure for months by contacting hundreds of community and business groups; working with Seattle and transit agencies. It has mailed informational packets to a thousand major employers.

State transportation officials are asking drivers to:

- Take a look at bus and Sounder train schedules and vanpool options in your area and consider how they could work for individuals.

- Talk to employers about working on-line and at home one or more days a week.

- Consider flex work schedule and commuting very early or late.

- Plan to arrive early and stay late when visiting downtown for shopping and entertainment. Arrive early and go out for breakfast or stay late and enjoy dinner in the city.

- See commute options at www.wsdot.wa.gov/Projects/I5/SpokaneStreetBridgeRepair/CommuteOptions.

Construction prep work is already underway. Drivers may have noticed scaffolding located under I-5 and workers in protective suits removing old, lead-based paint from the freeway expansion joints and bolts.

Drivers will notice overnight lane closures and work on both north and southbound as it gets closer to Aug. 10.

Check the special Website, www.wsdot.wa.gov/Projects/I5/SpokaneStreetBridgeRepair . Drivers can now get real time traffic and weather information by dialing 5-1-1 from most phones. This new traveler information system builds upon the highly successful Washington State Highway hotline that managed 4.6 million calls each year. Callers can also use 5-1-1 to get statewide construction, mountain pass condition, and state ferry system information, as well as toll free numbers for passenger rail and airlines. TTY users can call 1-800-833-6388.