Construction on the new South 216th overpass along Interstate 5 in SeaTac. The old overpass will be demolished starting Dec. 8, causing overnight freeway closures for at least one weekend and possibly two weekends. COURTESY PHOTO, State Department of Transportation

Construction on the new South 216th overpass along Interstate 5 in SeaTac. The old overpass will be demolished starting Dec. 8, causing overnight freeway closures for at least one weekend and possibly two weekends. COURTESY PHOTO, State Department of Transportation

I-5 overnight closures in SeaTac set for Dec. 8-9 near S. 216th Street

State Department of Transportation to demolish old S. 216th Street overpass; new bridge under construction

Tons of concrete and rebar will drop to the ground piece by piece when the demolition of the South 216th Street bridge over Interstate 5 in SeaTac begins Friday, Dec. 8, according to a state Department of Transportation news release.

Crews are already building a wider and longer bridge next to the existing structure as part of the state Department of Transportation’s State Route 509 Completion Project.

Demolishing the existing bridge could take up to two weekends. During demolition, crews will close one direction of I-5 at a time overnight along with South 216th Street. Freeway traffic will use signed detours via State Route 99 during the nightly directional closures. Drivers should also consider using other alternate routes such as State Route 167.

To prepare the bridge for demolition, crews will close South 216th Street between Military Road South and 31st Avenue South to traffic at 8:30 p.m. Thursday, Dec. 7, and drivers will follow signed detours. South 216th Street will reopen at 5:30 a.m. Friday, Dec. 8, to westbound traffic only.

• Westbound traffic on South 216th Street will cross I-5 using the southern portion of the replacement bridge except during demolition of the old bridge.

• Eastbound traffic on South 216th Street will continue to use signed detours to cross I-5 for six months.

Bridge demolition closures

Friday, Dec. 8

• 8 p.m. - Southbound I-5 lanes begin closing.

• 10 p.m. - All southbound lanes will close at South 200th Street. The South 200th Street on-ramp to southbound I-5 will also close.

• 8 a.m. Saturday, Dec. 9 - All lanes and the ramp reopen.

Saturday, Dec. 9

• 8 p.m. - Northbound I-5 lanes begin closing.

• 10 p.m. - All northbound lanes will close at SR 516 and the SR 516 ramp to northbound I-5 will close.

• 8 a.m. Sunday, Dec. 10 - All lanes and the ramp reopen.

Friday, Dec. 8, to Sunday, Dec. 10, 9 p.m. to 9 a.m. nightly

• Both directions of South 216th Street between Military Road South and 31st Avenue South will close. Travelers will follow signed detours via South 200th Street and SR 516.

If demolition is not completed Dec. 8-9, a second weekend of nighttime closures will be scheduled for Dec. 15-16.

Bridge demolition information

To tear down the bridge, crews will spread a protective 6-inch-deep layer of sand over I-5. Excavators fitted with claw and jackhammer-like attachments will break and remove pieces of the bridge, dropping them on I-5. The sand will absorb the impact of the debris. Bulldozers and sweepers will push the bridge debris off I-5 in time to open lanes each morning.

Why the replacement

The existing South 216th Street bridge must be removed and replaced with a longer bridge to make room for new northbound and southbound collector-distributor lanes that will pass under the bridge:

• Northbound I-5 between SR 516 and the new SR 509 Expressway that connects to a new northbound flyover ramp.

• Southbound I-5 between the new SR 509 Expressway on-ramp to southbound I-5 and SR 516.

About the new bridge

When complete in mid-2024, the new bridge will feature one lane in each direction, an eastbound left turn lane to Military Road South, bike lanes, and sidewalks accessible to all non-motorized users.

SR 509 project information

The SR 509 Completion Project builds a new four-lane, 3-mile-long tolled expressway. Completing this long-planned connection will help reduce congestion on local roads and highways by providing more direct access to Sea-Tac Airport from the south for both passengers and air cargo, as well as marine shipping at Port of Seattle.

Puget Sound Gateway Program

The SR 509 Completion Project is part of the Puget Sound Gateway Program, which also includes the SR 167 Completion Project in Pierce County. Together, these two projects will complete critical missing links in Washington’s highway and freight network. Both projects have multimodal benefits and create more than 18 miles of sidewalks, bike lanes and shared-use paths.

The $2.69 billion project is expected to be done in 2029, according to the state Department of Transportation.

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