It comes as little surprise that, of the 150 buildings sitting above the proposed deep bore tunnel set to replace the Alaskan Viaduct, 37 buildings have been identified as “vulnerable” during construction. The buildings, identified by transportation officials on Thursday, are in the southern end of the tunnel route where soil and, frankly, the buildings are the most unstable. According to the Seattle PI transportation watch “The list of downtown buildings considered most vulnerable includes the Polson Building, the Western Building, the old Federal Office Building and the Alexis Hotel. (WSDOT already has altered the tunnel route to avoid going beneath historic buildings in Pioneer Square)”
This will be an issue for the three companies bidding to build the underground tunnel. The proposals, which will be due in October, will be judged in part by how they plan to mitigate damage to these buildings and how they will address soil settlement. Property owners have been assured that there will be enough safeguards to protect, mitigate, or respond to any damage caused during construction. Seattle transportation projects are not strangers to voids caused by soil settlement. In constructing the light rail tunnel in Beacon Hill, Sound Transit was forced to spend millions of dollars filling voids.