The Dirt on Seattle’s Tunnel-Vision Future

“Most very large rock drills like that are designed to go through rock,” said University of Washington professor David Montgomery, explaining why he personally “wouldn’t bet his house” on Seattle’s deep-bore tunnel coming in on-time and on-budget:

Drilling through unconsolidated debris is what got them in trouble with the Brightwater plant. They’ve had great results tunneling through things like the Swiss Alps—it’s really hard rock, they go deep, and a rock drill going through that stuff, it’s just a matter of time before it gets to the other side.

A big drill like that is not designed to deal with the stray boulder, loose debris, that kind of stuff. What are they going to be drilling through? Essentially glacial sediments.

The big question in my mind is how much it’ll cost to do it. You can engineer your way out of anything. It’s a question of time and money for the most part. There’s a potential for a big surprise.

Montgomery’s area of focus is geomorphology, and he defers to the scientists who have studied the soils of the Alaskan Way Viaduct replacement project more thoroughly. But then, his concerns don’t stop with the tunnel’s construction.

I was talking with Montgomery thanks to a suggestion from his UW colleague Peter Ward, whose dire warnings about the cumulative effects of climate change should give pause to anyone planning a 100-year transportation project. Climate change deniers aside, we have reached the moment when policy decisions we make today must–if we are prudent–take into account the real-world, local effects of global warming.

Ward estimates a sea level rise of between three and five feet by 2100, and his prediction is supported by this recent Scientific American report on a positive feedback effect on sea level rise: “Seas Could Rise Up to 1.6 Meters by 2100.”

That leads us back to geomorphology, because as Montgomery observed, the south end of the tunnel sits near sea level currently. It’s essential that the Puget Sound be unable to reach the tunnel entrance, or it will fill like the U-joint beneath your kitchen sink. Publicola’s “How High Does the Seawall Need to Be?” notes that as of 2008, the seawall was being designed to handle an 11-inch sea level rise.

(Arne Christensen just unearthed that back-to-the-future glimpse of what the SoDo area could look like when the Puget Sound overtops the seawall, all the more disturbing because of course SoDo used to be tidal flats not that long ago.)

Montgomery used the recent earthquake and tsunami that ravaged Japan’s coast to illustrate the dangers of thinking that we’ve accounted for either the worst-case scenario or haven’t made what in retrospect will seem an obvious, colossal strategic error.

“Look at Japan,” Montgomery said:

They had a really great model for tsunami defense, in terms of building up the seawall 30 feet or so, but they failed to take into account that during the earthquake, the coast dropped three or four feet. It’s a good example of the part that was left out of the design coming back to bite you in the place you don’t like to be bit.

What might that look like for a waterfront tunnel in Seattle? What is the likely pattern of subsidence in and around Seattle during a Seattle Fault earthquake, or a great subduction earthquake. We might have a good idea of what it would be, but the one thing we can be assured of is that we’re not going to get it exactly right. Any prediction we make is an educated guess.

With Seattle anticipating both a major subduction zone quake and unable to predict the frequency of a Seattle Fault quake (the last, some 1,100 years ago produced uplift of 15 to 21 feet), the question of the double whammy of subsidence and tsunami is a distinctly live one.

Right away, we confront the problem of hypothesizing about worst-case scenarios–the obvious one that we can identify is so worst-case that preparing for it is off the table. Seattle planners are having enough trouble wrapping their heads around one to three meters, let alone a potential ten-meter differential. And a Seattle Fault quake that shifted the floor of the Puget Sound substantially could result in a tsunami that arrives on the heels of the quake itself, in minutes.

Could pumps keep the tunnel from filling with water? Possibly–if they’re working. Montgomery points to the failure of engineers to imagine the effects of an earthquake and tsunami on nuclear power plants. Just because something is called an emergency back-up is no guarantee that it will work in an emergency.

“I’m not trying to argue a pointed technical critique…but how do you frame it?” asked Montgomery.

What’s the worst case you want them to actually worry about? The big worst-case scenario in my mind, thinking about the stability of the shoreline there, is what happens to even the non-fill part of the shoreline, the glacial debris, during an earthquake. There’s an awful lot of really big landslides along much of the coast of Puget Sound, that reflect probably big failures during earthquakes.

It’s one thing to reinforce a seawall, but if the entire shoreline is at risk from a major quake, you haven’t accomplished all that much. The true worst-case scenario may be to imagine writing off a good chunk of Seattle’s waterfront because there’s nothing that can be done to save it.

“Where is the last place that I would want to be, during a big Seattle Fault earthquake or a subduction zone quake if there was a reasonable-sized tsunami in Puget Sound?” Montgomery added, finishing his thought. “The last place I’d want to be is in a big hole under the waterfront.”

However compelling he is in laying all this out, short-term catastrophes are not what Montgomery spends most of his time thinking about. His last book, Dirt: The Erosion of Civilizations, is required reading for anyone who’s read Jared Diamond’s Collapse. It’s a retelling of the story of human civilization following agriculture, globe-trotting from Babylonian to Mayan empires, and inspecting the way that soil exhaustion (through nutrient extraction, salinization, and erosion) becomes a chronic stressor for any habitation of significant size.

Erosion is “just slow enough that it’s never the crisis du jour,” he said, adding with a verbal shrug: “Dealing with slow-fuse crises is really hard for humans.” Yet in Montgomery’s view, the questions of why we fight, why we colonize, have a lot to do with the ground beneath our feet, whether we know it or not.

Soil, he explained, isn’t just brown “stuff,” it’s the interface between geology and biology. Life gains a purchase on weathered rock, breaking it down even more, and laboriously creating a fragile skin that’s hospitable to plant life. (His book details Darwin’s less-popular but no-less-groundbreaking studies of worm castings.) “It takes nature centuries to make an inch of soil,” he said, but “around the world we’ve lost about one-third of our cropland in the last 50 years, I think, to erosional degradation.” Each year, Eastern Washington watches its topsoil just blow away.

Here he and Ward are on the same page about the possibility of global famine, though they arrive there separately. Ward has been watching the sea level rise at a speed that will threaten the world’s deltas; Montgomery has been watching us starve the deltas of sediment:

There’s enough uncertainty to make you wonder how prudent it is to do things that we’re sure will continue to raise sea level, while at the same time we turn down the amount of sediment reaching the coast.

Perversely, we’ve turned up erosion on the farm fields up on the headwaters in most parts of the world by a factor of ten or twenty. We’re just parking all that sediment on flood plains and in reservoirs, and places where it’s not actually making it to the deltas to fertilize the coast.

You look at the sediment yield to coastal environments today and it’s been cut in half relative to what it was prehistorically. We may be raising sea level, and you might expect the deltas to keep up and move inland, but that presupposes that enough dirt is making it down the river systems to actually build it up.

So there we are. There’s a poetry to this image that captures not just our ambivalency regarding climate change, but the way we double-down on exhausting resources even faster at the same time as we learn our current usage is unsustainable. Perhaps not paradoxically, the prospect of shortage results in a kind of gluttony. (Not always–in Dirt, Montgomery furnishes examples of people who have farmed the same land for millennia without exhausting it, some even adding to its health.)

Jared Diamond mentions that every single class he teaches asks what the person who cut down the last tree on Easter Island was thinking. But that is to mistake the lesson. It’s what people were thinking, because it is our decisions en masse that come to define our crises (peak oil, water, dirt). On Seattle’s Easter Island, we are thinking about how quickly we can drive past Seattle. We are thinking about gridlock downtown. We are not thinking of Eastern Washington agriculture, usually. We are thinking that someday–not now–things will get bad, and we’ll deal with them then.