The Sellwood Bridge and and Highway 43 will be at a stop for 20 minutes per blast. The southbound lane of Highway 43 will be closed from 7:00PM to about 6:00AM the following morning.
The Blasting is the only way for crews to excavate the west hillside and install retaining walls that will eventually hold up a bigger interchange. The new Sellwood Bridge will have a wider interchange to Highway 43 then the existing Bridge. This portion of the project will take a few months, then by 2014 crews will move the traffic lanes to the wet and begin constructing the east side of the interchange.
The blasts which haven't sparked any complaints from residents so far, will take place over the course of the next four weeks between the hours of 9:00PM and 3:00AM, according to Mike Pullen, a spokesperson with Multnomah County. Crews place heavy mats over the explosives to muffle the explosion as well as limit flying debris. In fact the warning sirens before the blasts are louder then the blasts themselves.
Check out video of the first blasts from a few weeks ago: