Reminder:Both I 405 northbound in Bellevue and 520 bridge closed this weekend

Both directions of State Route 520 across Lake Washington and northbound Interstate 405 through Bellevue are closed this weekend .

Both directions of State Route 520 across Lake Washington and northbound Interstate 405 through Bellevue are closed this weekend for critical inspections, repairs and construction.

Drivers should plan for long delays on I-90 near the detour routes, westbound SR 520 approaching I-405, northbound I-405 where all traffic will exit to Southeast Eighth Street, and I-5 through downtown Seattle. Surface streets in and around Bellevue are expected to experience extra congestion as well.

“The weekend closure of SR 520 and northbound I-405 will significantly affect traffic across the Puget Sound region,” said WSDOT’s Northwest Regional Administrator Lorena Eng. “We realize that not everyone can completely change their commute. But for those who have a choice, options such as vanpooling, carpooling or other forms of transportation can help avoid heavy congestion.”

I-405 closed at 10 p.m. Friday, July 12. The SR 520 bridge closed at 11 p.m. Both will reopen by 5 a.m. Monday, July 15.

“Combining closures helps us limit summer weekend impacts on drivers while still allowing us to complete major work,” said WSDOT traffic engineer Mark Bandy. “Scheduling this type of work isn’t easy. It must be carefully coordinated with other regional construction projects and avoid weekends such as Seafair, the Bite of Seattle and Bellevue Arts Festival.”

The shutdown is needed for maintenance and preservation of the two corridors, state officials said. By simultaneously closing both SR 520 and northbound I-405, crews will complete the time-consuming work in a short period, reducing the need for nightly closures over a much longer stretch, officials said, adding that there are a limited number of weekends available in the summer to complete work on numerous road construction and maintenance projects.

On I-405, crews will replace the 50-year-old concrete panels in the two left lanes between SE Eighth and Main streets, the length of a dozen football fields. Later this summer they will replace panels in the two right lanes. They also will grind the concrete on certain sections of I-405. When the project is complete this fall, drivers will experience a smoother ride with improved traction.

On SR 520, bridge maintenance crews will inspect the floating bridge. The annual inspection, which includes testing, maintenance and repairs, must occur during calm weather. Eastside Transit and HOV Project construction crews will take advantage of the closure to install an 11-foot-in-diameter fish-friendly culvert — the project’s largest and deepest to date — beneath all lanes of SR 520 east of 108th Avenue NE.