Theories abound about what's blocking Big Bertha, Seattle's tunnel boring machine, the world's largest at that.
The tunneling action is underground, of course, but it's become a popular spectator sport, second only to the Seahawks in terms of national speculation. Big Bertha is blocked. Few were expecting that. A giant like Bertha, surely it could chew through anything.
If I-told-you-sos were crows, they'd be lining the Alaskan Way Viaduct right now cawing and guffawing. Mike McGinn and consultants and tunnel opponents are delighting in Bertha's birth pains. Tunnel agnostics have joined the peanut gallery too, because for the first time in a long while there's interest in what lies beneath the city.
Entrepreneur and author Bill Speidel managed to turn Pioneer Square's basements into a tourist attraction that continues to fascinate visitors. The Underground Tour hardly gives you entrance to a buried Pompeii, but the layers do tell an intriguing story of how Seattle rebuilt after the fire lifting ground floors up a story, how our sewer pipes were once made of wood and our toilets were turned into geysers by the incoming tide.
The fascinating thing about whatever geological or archaeological thrombus is blocking Bertha is that the list of suspects is long.
Bertha’s forward progress has been halted in the vicinity of once-upon-a-time Ballast Island, the site along the waterfront where cargo ships routinely dumped piles of rocks from their holds. In the olden days, Seattle had no respect for wetlands, so we filled them in — with anything. Vast stretches of the waterfront and SoDo are manmade with fill from various local regrades and sawmill tailings. And there's a lot of water down there too. (Some SoDo property owners can literally watch the tide go in and out of damp basements.) The tunnel builders are installing pumps and digging wells to keep Bertha from drowning. Maybe she needs a Captain Nemo to navigate the slurry.
Seattleites also used Elliott Bay and the Duwamish tide flats as a garbage dump for many decades. They tossed stuff from ships and off the docks. Some early communities actually lived on docks over the water. When work was being done on the Starbucks headquarters, for example, they found evidence of the city's first Chinatown, which had been built on a pier.
There's an old sailing ship, the Windward, buried somewhere near Western Ave. and the Colman Building. There could be other gear down there too: steam engines or wrecks. In the fast-growing city, no one kept strict track of the garbage or the fill or what either contained. The city simply left all the discarded stuff in place and sprouted up around all it.
Certain people and projects have recently attempted to map the old shoreline. Author/geologist David Williams is working on a book about how the city reshaped its waterfronts and hills. It will no doubt be an epic story.
The soundest Bertha theory, which Williams favors, is that the boring machine has run into a large boulder, possibly a glacial erratic left over from the last ice age, some 10,000 or more years ago. Such rocks are found here and there about the city, from Seward Park to Wedgwood. If it is a single object blocking Bertha, a massive glacier-deposited rock is the most likely suspect.
But the layers below the manmade strata occasionally cough up plenty of alternative interesting stuff. Williams notes that the city's re-graders uncovered buried forests, bones and even a suspected meteorite.
In the 1960s and '70s, major projects kept turning up mammoth, mastodon or sloth bones belonging to ancient visitors that moved in as the ice retreated. (For proof, visit The Burke Museum.) A giant ground sloth was found at the Sea-Tac airport, and prehistoric mammoth or mastodon bones turned up in digs at City Hall, the Library, I-5 and the Space Needle. Could Bertha have stumbled upon a giant prehistoric graveyard? Is a mammoth's molar big enough to stop a giant dental drill like Bertha?
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