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Bertha tunnel dig: What CSI experts could tell us

Crews drill to look for an obstruction in front of the tunnel-boring machine on Seattle's waterfront. Credit: Washington State Department of Transportation

With a preliminary plan for digging the pit to save Bertha in hand from Seattle Tunnel Partners, the Washington Department of Transportation's archaeologists are testing the ground where the big dig is going to take place. Last week, some press reports suggested they were going to be digging for artifacts, which brings to mind images of Indiana Jones.

WSDOT clarified that by saying their test drilling is really an effort to get a sense of what kind of ground they'd be digging into, the lay of the land underground. The project's cultural heritage expert Steve Archer calls in a "inventory" that must be done to comply with federal law. They have done such testing in the general vicinity of Bertha, but not as extensively as they now are doing, says Archer: "We just did not anticipate such a deep/broad impact" in the current location.

Prior to digging the big pit, WSDOT is in the process of drilling approximately 60 holes, anywhere from 20 to 40 feet deep, according to spokesperson Laura Newborn. They will be checking out two areas above Bertha between Main and Jackson streets on Alaskan Way. One is a patch 150 feet long (north/south) and approximately 110 feet wide. The other is 130 feet long and 50 feet wide. Can they get better and more specific clues about what to expect during excavation?

Truth be told, the tunnel builders would likely be happy if no artifacts whatsoever were found, because any finds might lead to further delays. Still, while the state has tested the soil at various points along Bertha's route, officials need better information about what lies underneath Alaskan Way in this spot because they never planned to dig a giant pit there. Bertha was tunneling along, for the most part, at a depth where the soil predates human history.

The rescue pit, however, will be dug through ground that is located along the shoreline of original Seattle, an area that included important wharves, landing sites, possible native encampments, etc. It also include tidelands that might have been used by Native Americans for fishing, gathering shellfish and innumerable other activities. The testing, Archer says, will tell WSDOT "what sensitivities exist, not that we think there are specific artifacts or sites at the shaft location and are trying to find them." 

WSDOT's says that it is cooperating closely with the local tribes. In testing nearby, only one known native artifact has so far been recovered — a bit of cedar rope — but there could be more. The state's surveys along the length of the waterfront indicate the possibility of indigenous use and earlier finds in many places. Paul Dorpat's excellent history of the waterfront gives a good example of how complex it all can be.

In 1998, human remains were uncovered during the construction of the Port of Seattle's Bell Street Harbor project. Historians know that a native burial ground existed near the foot of present day Seneca Street, which suggest that burials were known near the present waterfront, but Dorpat reports that the Bell Street bones were quite possibly in soil that was dumped there as landfill much later. In other words, they might have been inadvertently relocated during one of the early 20th century's re-grades. In addition to flattening the city's hills and filling in tidelands, ravines along the water were filled in and built over. The remains were found near the entrance of an old ravine that was filled as part of extending Elliott Avenue in 1912. If nothing else, it's a fascinating snapshot of the complexity of the creation of the modern waterfront.

The top tiers of soil where Bertha is stuck are almost certainly composed of various layers of fill, and who knows what might be in them? No one is expecting an Indian village or graveyard or Doc Maynard's whiskey bottles, but excavating can frequently turn up surprises like Bell Harbor's or South Lake Union's recent mastodon tusk. (For a real bonanza, check out what soil testing just turned up in Los Angeles.)

The thing is, what might be the most valuable down below is often the most mundane. If WSDOT hauls up layers of sand, ash from the Seattle fire, coal or even sawdust from Yesler's mill, the question isn't whether they've found an exciting object but whether they will excavate in a way that can help them make the most of what they find. Could Bertha's woes yield a substantial public benefit in the process?

Dennis Lewarch, the Historic Preservation Officer for the Suquamish Tribe, says the Bertha pit offers a unique potential. "I've been involved in this project since it's inception — it's our only opportunity to have a horizontal exposure in an area that's the old shoreline," he says. That shoreline was heavily used by the tribes, including Chief Seattle's people, who played such a huge role in the founding of Seattle, from feeding settlers to being the city's original workforce in milling and fishing.

What an archaeological investigation might yield here is context. Lewarch says the pit is big enough that a large exposure could be made and archaeologists working in the pit could find, for example, evidence of how the beach was used in the pre- and post-contact period. They'd be looking for things like post-holes from structures, fire pits and stains from planking that can allow for a CSI-like reconstruction of structures like longhouses. In other words, it's not so much artifacts as evidence of use, how people worked and lived, that could be uncovered. That you can't get from core samples. The pit would be big enough that archaeologists could use a backhoe like a trowel, Lewarch says, removing the historical layers a bit at a time.

WSDOT will certainly monitor the digging when it takes place. Archaeological monitoring is pretty standard practice. But Seattle historical archaeologist Robert Weaver, who has done waterfront survey work for the state, says that drilling and monitored digging itself won't necessarily result in an adequate evaluation of this historical spot.

He suggests that a retaining wall be constructed down to the old beach level and that the fill materials be removed down to the Seattle Fire layer. Then the excavators, Weaver says, should use "controlled archaeological methods to deal with the deposits including the 1889 fire layer or the beach area below it. Such an approach (which provides far better observation and evaluation of the deposits) would allow for controlled excavation that would result in far better interpretation of early-Seattle. It would also increase confidence in the findings if what’s there really doesn't have any historical value."

He estimates an experienced archaeological crew could remove material in the matter of a week or two. Most of the follow-on work would be done off-site later to catalog, sort and analyze the materials found. It would cost some money, but shouldn't lead to delays. He cites a dig in London as an example of what could be done here.

Is there lemonade that can be squeezed from the Bertha lemon? The new core samples won't tell us everything about what's down there, but they could give us new clues. And those could lead to some exciting original work and insights into the early years of the place that became Seattle and the people who lived here before and after.

Check out Crosscut’s exclusive Bertha page for all the news and commentary about Seattle’s most famous underground machine.

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