Drivers on State Route 518 will endure nighttime detours and delays around Sea-Tac International Airport as the light-rail line is built across the freeway.

The light rail bridge will be built across SR-518, just west of International Boulevard near the South 154th Street station in Tukwila.

Because of increased airport traffic on Friday evenings, there will be no Friday night closures. The closures will also take a holiday during Independence Day week from Thursday, June 28, through Friday, July 6.

The closures are scheduled between 11 p.m. and 5 a.m.

Westbound lane closures from SeaTac and Tukwila are scheduled to begin Wednesday, June 13, through Monday, June 18, with little delay expected.

Full westbound closures to southbound Airport Expressway or on to Burien are set from Tuesday, June 19, through Sunday, June 24.

The freeway and the westbound exit to the airport will be closed for three days beginning Monday, June 25.

For vehicles coming westbound to Burien, they will detour off SR-518 at the State Route 99 (International Boulevard) off-ramp and make a left turn westbound onto South 154th Street, getting back on SR-518 at the South 154th Street on-ramp.

Greg Phipps, spokesman for the Washington State Department of Transportation, estimated only a five-minute delay.

A five-minute delay is also expected for westbound vehicles taking the airport expressway. Drivers would exit onto the SR-99 off-ramp, turn right to get onto southbound SR-99 and take another right at South 170th Street, then enter onto the expressway via the on-ramp loop there.

Although delays might be minimal, Phipps cautioned travelers to plan to arrive at the airport two hours before their fight's departure time.

"To catch your flight, it is even more important to obey the two-hour rule," he cautioned.

Closures are also planned for eastbound SR-518 drivers from Burien.

Lane closures are set for Monday, July 9, through Wednesday, July 11, with full eastbound closures for July 12, 16-19 and 23.

While no detour is required for eastbound travelers using the airport expressway, for those going on toward Tukwila the route is more complicated.

The eastbound detour requires drivers to exit at the expressway, then exit to Air Cargo Road, take a right turn to eastbound South 160th Street and turn left onto northbound SR-99. The detour could add 10 minutes to the drive, according to Phipps.

Electronic-message and portable signs will guide travelers through the detours.

Closure dates are subject to change. The detours are expected to end by July 23.

Updated information will be available at wsdot.wa.gov, soundtransit.org and portseattle.org/seatac.

Sound Transit will use the same balanced cantilever construction technique used to build the light-rail bridge over Interstate 5 near north Tukwila, according to construction coordinator Madeline Greathouse.

Sound Transit spokesman Bruce Gray estimated the downtown-to-airport light-rail link construction is about 70 percent completed.

Officials plan to have light rail up and running to Tukwila by the summer of 2009. The final two-mile link to the airport is set to open in December 2009 in time for the January 2010 Olympics in Vancouver, B.C.

A lone bid from Mowat Construction for the airport/SeaTac city center station, which came in more than 80 percent higher than budgeted, may create a snag in the timeline.

Gray said Sound Transit is working with Mowat on reworking the design and bid amount. Further details may be announced soon, he added.