New Map Shows Widespread Sinking Near Bertha Rescue Pit | KUOW News and Information

New Map Shows Widespread Sinking Near Bertha Rescue Pit

Dec 11, 2014

  Much of Seattle's Pioneer Square neighborhood has sunk an inch or more, according to a map released by state transportation officials on Thursday.

The sinking is greatest next to a 120-foot-deep pit being dug to rescue the broken-down tunnel machine known as Bertha. There, the ground has sunk 1.4 inches.

Areas more than a quarter mile away from the pit have sunk by half an inch or more.

Bertha has been stuck underground for a year now, instead of digging a new highway tunnel as planned beneath the Seattle waterfront.

Washington State Department of Transportation's contractor, Seattle Tunnel Partners, has been pumping out groundwater as it builds a pit to rescue Bertha.

Washington Department of Transportation map shows sinking ground around the Bertha rescue pit (the red mark near the waterfront).
Credit WSDOT

WSDOT officials have said that removing groundwater can lead the ground to compress. They announced on Sunday that Seattle Tunnel Partners would cease dewatering the ground. On Thursday, a WSDOT press release said the map, which shows ground sinking deeper the closer you get to the pit, "does not present conclusions about the effect of dewatering."

WSDOT is monitoring the neighborhood's streets, sidewalks and buildings for settling as often as twice a day. Road crews were out Thursday afternoon studying a widening crack in the middle of South King Street near First Avenue South.

State officials told the Seattle City Council this week that the Alaskan Way Viaduct remains safe to travel on.

WSDOT officials, including Washington Transportation Secretary Lynn Peterson, will report their findings to Seattle City Council Monday morning.