Demolition, year-long closure of Pacific Avenue overpass starts Monday

Tacoma’s Pacific Avenue bridge over Interstate 5 is set to be demolished starting Monday as part of a project to widen the freeway, and it will take almost a year for its replacement to open to drivers.

The state Department of Transportation’s $161 million effort to alleviate freeway congestion through Tacoma will widen I-5 to four lanes in both directions, and include carpool lanes. To make space for it all, both the Pacific and McKinley Way bridges need to be rebuilt.

Crews plan to open the rebuilt Pacific Avenue span in March 2016 and then start demolishing the McKinley bridge, which should take 18 months to reopen to drivers.

“What we don’t want to do is have both bridges closed at the same time,” project engineer Jon Deffenbacher said. “We need to keep a pathway for traffic to get in and out of downtown.”

Pacific closes to drivers at 5 p.m. Monday.

“People should expect to see equipment moving in,” Deffenbacher said.

By about 10 p.m., concrete will start getting crunched.

Demolishing the bridge means periodically closing lanes of the freeway below.

Monday through Friday until the end of April, crews will close northbound exit 133 and lanes to Interstate 705 and state Route 7.

The closures start at 11 p.m. and end at 4 a.m. the next day. Traffic to I-705 and state Route 7 will be detoured to the Portland Avenue interchange.

Those closures will let crews get rid of the bridge approaches, but more closures will be needed as they move to the center parts of the overpass and lastly demolish what’s left on the southbound I-5 side of the bridge.

Some pieces of concrete will be cut and removed by crane. Some will be hauled away after they are broken off the bridge and allowed to fall onto the roadway below, which will be covered in sand to protect the pavement.

Until the overpass reopens, vehicles will be detoured to South M Street to get across I-5.

Only two lanes of the Pacific Avenue bridge will open next March. The other two are expected to follow in May 2016, which gives crews time to do finishing work, including adding sidewalks.

The span will have a combination bike-pedestrian path on one side, and a pedestrian sidewalk on the other.

Crews expect to finish widening I-5 in 2017, but it will take longer to open the carpool lanes, which will have to be extended and built through the Nalley Valley.