What's Blocking Bertha, Seattle's 5-Story Tunneling Machine?
by: Mark Memmott, NPR, December 12, 2013 11:12:00 am
But before we get carried away about creatures beneath our cities or hidden chambers holding eggs that will hatch monsters, let's focus on what we know about what's happening in the Northwest.
"Transportation crews still don't know what exactly is blocking the path of 'Bertha,' the giant boring machine that's drilling the new Highway 999 tunnel under Seattle. The machine was stopped on Friday after encountering an object 60 feet under South Main Street."
SeattlePI.com says "the latest trouble started ... when Bertha's five-story tall cutter head felt some resistance, then stopped."
As The Blaze notes, since Bertha "is designed to tunnel through rock and soil without issue, it's puzzling as to what could have stopped it."
Today, we're hearing from The Seattle Times that it will likely take about two weeks to figure out what's blocking Bertha. It adds that:
"The leading theory is that Bertha hit a boulder, but the soil around it is too soft to hold it snugly and allow the rotary cutter head to crack the rock apart."
What to do?
According to the Times:
-- Either pull Bertha back to allow crews to get around it and then, using power drills and hammers, break up the boulder (assuming that's what the problem is).
-- Or, "work from above ... to drill down and break up the object or to lift it out. That likely would require a protective wall or pit to be installed, holding back sand and groundwater."
But if the problem involves something more mysterious ... suggestions are welcome in the comments thread.
Bertha is cutting a nearly 2-mile tunnel that will replace the Alaskan Way Viaduct — a double deck roadway along the city's waterfront on Highway 99. She's the world's largest tunneling machine, according to the Washington State Department of Transportation.