A crack in Pioneer Square's urban renewal

A neighborhood built on squishy, loamy landfill, confronted by physics, is faced with an urban conundrum.
Crosscut archive image.

A Pioneer Square street.

A neighborhood built on squishy, loamy landfill, confronted by physics, is faced with an urban conundrum.

Seattle was wet from the beginning. The town was founded on tide flats and marshes, the nearby soil soaked with runoff. This is rain country, after all, and the relentless wet left some early pioneers in tears. The ground under Pioneer Square is squishy and waterlogged by both sea and springs. Much of it is landfill.

Why should it be a surprise that if you pump out millions of gallons the land and buildings built on top of this slurry would notice? In the attempt to rescue Bertha — broken down for more than a year in a stretch near the current Alaskan Way Viaduct between Jackson and Main Streets — the physics of the rescue pit are a tad complicated, but also simple: For every action there is an opposite reaction. Pump out water and dig out soil, and stuff will move. A chunk of Pioneer Square is now slowly sinking.

Worries about the soil and settlement were raised early on in relation to the tunnel itself. Peter Steinbrueck, who worked as a consulting Historic Architect on the project, raised questions in 2013, worried about the impact of the tunnel project's potential “interference to hydrological status” of Pioneer Square and how the tunnel builders would respond to known and unknown risks of just this kind. A city study in 2011 warned of the high risks of building a tunnel in the area due to soil conditions.

The Washington State Department of Transportation and its contractor, Seattle Tunnel Partners, have issued a map that physically represents the areas where Pioneer Square is sagging — at least one block has sunk an inch or more. The city council was informed this week that a major water main running down First Ave. has been bent by the sinking soil and will have to be replaced, a no doubt expensive and gridlock-inducing repair. I for one would not want to pay that plumber’s bill.

The Viaduct too — the sinking of which after the Nisqually Earthquake is the whole rationale for the tunnel — is also sinking further. And other street damage is showing up — notably a large crack near First and King Streets. That in itself is nothing to get too exercised about. Many of Seattle’s streets resemble the road to Kandahar. But the overall concern is: Architecture and shifting geology are not always a good match.

The question is, what exactly is the dynamic underground, and how much is soil shifting? Are we talking about just some cracks and inconvenience, or larger instabilities that could render the Bertha rescue impossible, or prohibitively expensive? Is the Viaduct still safe? What if we have neither the tunnel nor the Viaduct? Are we looking at sinkholes and buildings rendered unsafe? Remember, this isn’t an earthquake but a manmade emergency.

So, now the engineers are making it up as they go along. Bertha’s now notable enough that it’s gaining national attention, being featured in publications ranging from the New York Times (“In Seattle, a Sinking Feeling About a Troubled Tunnel”) to Popular Mechanics (“It’s still stuck”). Rather than being hailed as a technical marvel, we’re looking hapless. Boosters can console themselves that at least it appears to be “world class” haplessness.

If Pioneer Square is valuable to us for what it was in the past — our original settlement and our first downtown, a repository of history in a city often thought to have too little of it — it is also a huge piece of the future. The snagging of Weyerhaeuser’s corporate headquarters, the new housing near the stadiums, the expanding transportation node at King Street, the makeover of the waterfront — all of it is part of making the district and adjacent areas more vital for business and new residents who are not reliant on shelters and missions.

Bertha’s woes threaten the literal foundations of a new kind of urban renewal for the district, as well as doing damage to our heritage. Is Bertha simply cracking a few eggs to make a new urban omelette, or will it turn out to be a truly rotten engineering egg?

The answer is somewhere down there, right under our feet.


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About the Authors & Contributors

Knute Berger

Knute Berger

Knute “Mossback” Berger is Crosscut's Editor-at-Large.