Bertha may sit stuck for weeks as mystery solved

SEATTLE — Diagnosing what has blocked a boring machine working on a highway tunnel under downtown Seattle, and figuring out what to do, could take about two weeks, the project director for Seattle Tunnel Partners said Wednesday.

The Transportation Department said crews are drilling “de-watering” wells Thursday to relieve pressure on a machine.

Spokeswoman KaDeena Yerkan said the wells should make it easier to identify what’s blocking the machine known as Bertha. Then contractors will determine how to proceed.

The machine was halted Saturday by the mysterious obstruction. It may be a huge boulder.

The boring machine is 60 feet under the streets and about one-tenth of the way into the planned 1.7-mile tunnel that will carry Highway 99 traffic and replace the Alaskan Way Viaduct.

Chris Dixon said specially trained workers could be sent to the site next week, The Seattle Times reported. They would peek outside the tunnel machine’s cutter head to see what’s in the way.

The machine can retreat about 18 inches and compressed air would be forced into the small space in front of the cutter head to allow workers to get a look at the problem.

Since the top of the tunneling machine is about 60 feet below ground, professional divers used to working below the surface would be needed.

The leading theory is that the machine called Bertha hit a boulder last Friday and that the soil around it is too soft to hold it firmly and allow the cutter head to crack it apart. The machine was shut down Saturday about 1,000 feet into the 1.7 mile project.

The quickest way to remove whatever it is would seem to involve divers breaking it up with power drills and hammers, along with Bertha’s drills, Dixon said.

Alternatively, contractors could drill down from above and break up the object or lift it out. That probably would require building a protective wall or pit to hold back sand and groundwater.

“It would take several weeks to build that,” Dixon told a news conference.

The 58-foot diameter tunnel is scheduled to be completed by the end of 2015, creating a four-lane route for Highway 99 traffic between South Lake Union and the area south of downtown.

The $1.4 billion tunnel contract is part of the $3.1 billion project to replace the Alaskan Way Viaduct along the downtown Seattle waterfront.

———

Information from: The Seattle Times, http://www.seattletimes.com

More in Local News

Man arrested after police find van full of drugs, cash and guns

An officer on patrol noticed a vehicle by itself in the middle of a WinCo parking lot at 2 a.m.

Jim Mathis, the Vietnam veteran whose Marysville garden was recently featured in The Herald, died Wednesday. Mathis, who suffered from PTSD and cancer, found solace in his beautiful garden. (Dan Bates / The Herald)
Vietnam veteran Jim Mathis found peace in his garden

The Marysville man who served two tours died Wednesday after suffering from cancer and PTSD.

Smith Island habitat restoration cost to rise $1.2 million

The project is intended to increase survival rates for juvenile chinook salmon.

Add deputies and bump taxes a bit, executive proposes

Dave Somers’ Snohomish County budget proposal also would address traffic problems in neighborhoods.

County councilman proposes banning safe injection sites

Nate Nehring says county officials also should find “credible, long-term solutions to addiction.”

Car crashes near Everett after State Patrol pursuit

The driver and a second person in the car suffered injuries.

They chose the longshot candidate to fill a vacant seat

Sultan Mayor Carolyn Eslick will serve as representative for the 39th legislative district.

Alien brain? No, a colony of harmless freshwater creatures

Bryozoans are tiny invertebrates that live in jelly-like masses, and their presence is a good thing.

Definitely not Christmas in July for parched young trees

“I live in Washington. I should not have to water a Christmas tree,” says one grower. But they did.

Most Read