As the ground settles more than anyone wants near the great tunneling issue in downtown Seattle, crews from the Washington State Dept. of Transportation kept up the analyzing and surveying last week.
Since announcing the uneven settlement on Dec. 5 of approximately 1.4 inches near the access pit to repair North America’s largest tunnel-boring machine, another note of unfortunate news in a project that slowly turns into a major construction issue for Seattle as Bertha—the tunneling machine—hasn’t had significant movement now for over a year with at least a few months still remaining until it even attempts forward progress, crews have surveyed the area around the settlement.
By the end of the day on Friday, Dec. 12, crews had surveyed 20 of the approximately 30 buildings where the greatest settlement has occurred, along with keeping a close eye on the already troubled Alaskan Way Viaduct.
In a release on Friday, WSDOT says: “Our experts are still analyzing data and conducting daily inspections of the viaduct, but to date, no significant settlement has been observed beyond the initial settlement.”
WSDOT says the viaduct remains safe for travel.
Also last week the existing crack that apparently had widened on South King Street received further attention. Project contractor Seattle Tunnel Partners checked the roadway with ground-penetrating radar. While WSDOT awaits the report, no voids were detected under the pavement.
To keep the analyzing up to date, twice daily manual measurements at the bottom of both the east and west columns of the viaduct continues, along with measurements of deep survey points more than 80 feet underground.
The adjacent map shows data from the ground surveys and deep survey points, but does not represent data from building surveys or the surveys of the viaduct.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.