The dirt on Bertha

Seattle Tunnel Partners has just started digging the 120 by 80-foot Bertha rescue shaft — otherwise known as an "access" or "repair" pit — on the waterfront near Main Street needed to repair the broken tunnel boring machine. Already the tricky ground has yielded a new delay. Isn't that the story of Bertha ?
 
The project has reportedly hit a shell deposit — possibly a midden — nearly 20 feet down, which brought rescue digging to a halt on Oct. 23. Cultural features, middens are essentially Native American garbage pits that contain shells, fish bones and other items disposed of by tribes along the shoreline. They often also contain artifacts and, not uncommonly, human remains, and can serve as indicators of habitation or other uses.
 
In short, Seattle Tunnel Partners' work must stop until the collection of shells is examined and the tribes are consulted. How long a delay takes place will depend in part upon what they conclude.
 
The Washington Department of Transportation was hoping to dodge this particular bullet. The rescue pit was, of course, unplanned, but because Bertha is stuck and needs fixing, the shaft must be dug through ground between Jackson and Main streets — turf that wasn't originally intended to be excavated like this. Some 20,000 cubic yards of soil will be removed and hauled off by barge.
 
The risk, as WSDOT is now experiencing and I have previously written: Bertha is stalled deep under a problematic area that may contain other significant artifacts or material as well. The tunnel boring machine broke down along the old shoreline of Denny Island, the home of a known Indian village and later early Seattle. That same area also once hosted historically important wharves, railroad lines and was the dumping ground for a number of frontier Seattle businesses.
 
Nearby is the intriguing Ballast Island, made up of rocks and cobbles dumped by 19th-century sailing ships picking up cargo and passengers. Eventually, Ballast Island grew large enough that it became an Indian landing and campsite. Bumping into it would almost certainly yield significant materials, which WSDOT would like to avoid at all costs. Through sampling in the area, which turned up what could be ballast stones, WSDOT believes it has located the site of Ballast Island just north of the rescue pit. If they are correct, their work should not impinge on it.
 
Either way, archaeologist Robert Weaver, who has studied what lies beneath the waterfront and SoDo, insists that the Bertha pit site could yield data and artifacts that might fill in our picture of early Seattle.
 
Until now, WSDOT has tended to disagree. What interests historical archaeologists like Weaver the most — the fill materials dumped into the wetlands and bay during the 19th and early 20th century — is considered by WSDOT and its consultants to be 18 to 23-foot deep "undifferentiated fill," defined only as "loosely compacted alternately mixed and laminated silts and sands with sparse fragments of milled wood, brick, coal, glass and organics." While the make up of the soil here was determined by test bore samples in the vicinity, samples don't necessarily tell the whole story. They can still miss things of significance.
 
"There has been limited excavation below modern material of the pit so far," says WSDOT project archaeologist Steven Archer, "but previous sampling has been consistent with our expectations of unsorted hydraulic fills with no undisturbed archaeological deposits in primary context present."
 
No one is expecting a Pioneer Pompeii, but Pioneer Pompeii's landfill and garbage could still tell us a lot if we cared to sift through it.
 
WSDOT has said that the area immediately below the fill level is the original beach or seafloor. Tidelands and beaches can show signs of Native American use. Shell middens, native remains, cedar ropes and other items have been located during previous waterfront projects. On this point too, WSDOT's geo-archaeological assessment has seemed unphased. Archaeologist Elder concluded in a memo last spring that "it appears that the pre-development ground surface of the study area would have largely been inaccessible for human use just before the historic era and would have served as a poor environment for the preservation of in-situ archaeological deposits." In other words, there would probably be nothing of human archaeological interest there, and if there once was, it's probably been degraded or lost over time.
 
The discovery of a shell midden at 20 feet deep suggests that Seattle Tunnel Partners is digging into old shoreline that was, in fact, not "inaccessible to human use."
 
Still, the shell deposit was spotted because WSDOT is keeping an eye out for things of potential interest as they dig the pit. Earlier this week, archaeologist Archer said that such "monitoring will occur with all excavation until the excavation has reached glacially overridden deposits without potential to contain cultural material." Monitoring is done by spotters who peer into the pit from a "crow's nest overlooking the work" using binoculars and enhanced lighting to see the soil layers and what's being uncovered. Anytime something of interest is encountered, they will stop work so that trained archaeologists can enter the pit to take a closer look.
 
If Bertha has taught us one thing, it's that digging along Seattle's historic shoreline is full of surprises. We'd best be prepared for them.