Drivers in south King County should expect delays this weekend as contractor crews working for the Washington State Department of Transportation will close the westbound State Route 18 ramp to southbound Interstate 5 to replace the concrete around two bridge expansion joints from 10 p.m. Friday, June 13 until 5 a.m. Monday, June 16.

The expansion joints were installed in 2012 as part of the first phase of the Triangle Improvements project that added two new flyover ramps to the I-5/SR 18 interchange. The new ramps eliminate weaving, which improved traffic flow and safety.

Recently, Department of Transportation engineers noticed potholes and minor cracks forming near and around the joints. As a result, the department is enforcing its warranty provision with contractor Mowat Construction Company to fix the concrete area that holds the joints in place, known as the header, at no charge.

“New cars come with warranties and so do construction projects as a way to protect the state if something needs to be fixed,” said Messay Shiferaw, engineering manager. “We saw problems with the concrete header around these joints and asked our contractor to replace them.”

This work cannot be done during nighttime closures; it requires a full weekend to complete the job. Contractor crews will chip out the existing concrete header with jackhammers. Once they are removed, the new ones will be installed with enough time to properly harden and cure before the ramp can reopen to traffic.

During the closure, westbound SR 18 drivers will be detoured to northbound I-5 and the South 320th Street exit in Federal Way, where they can reenter to southbound I-5. During weekends, peak travel occurs in the mid-afternoon, but backups are expected throughout the closure and drivers are urged to plan accordingly.