Unraveling Urban Life and Space
Lots of talk these days about a wall on our southern border, but walls aren’t built with words. They’re built with concrete, masonry, reinforcing materials, excavation, drainage…the everyday palette of landscape architecture practice. It’s not often that the national conversation overlaps with site construction expertise, so… let’s talk about walls.
Walls are major construction. They are big and heavy and not flexible, so they need foundations - footings. An ordinary wall that screens a dumpster or encloses a garden is about six feet high above ground, and a few more feet below ground, depending on frost depth. Larger walls require larger footings.
Footings require excavation, and some idea about the stability of the soil or rock below and around that excavation. It’s especially important to have material down there that won’t shift or expand and contract, such as with water absorption. Some soils do this during ordinary seasonal rains or storms. Since properly constructed walls last a long time - see Great Wall of China and Hadrian’s Wall - they must be designed not just for ordinary storms, but once-in-a-lifetime or once-in-several-lifetime storms. Stronger walls use more materials for each linear foot of wall, so greater storm resistance = more money.
For a structure this size, especially if soils are less than ideal, an engineer likely would recommend tying the footing to the underlying bedrock. So how far down is the bedrock? How do you do find out? You do it the same way you determine what the elevation and slope of the soil surface is along the path of the wall and what pre-existing obstacles require demolition or adjustment of the wall’s path: you hire someone to do a survey and soil borings. This preliminary work is not minor; it takes time and expertise. You can’t skimp on it, because if it’s done poorly, it will ruin the project. My only comment about an unstable 1000 mile long 25’ high wall: liability nightmare.
These surveys must happen before any realistic, buildable final design can be done. It’s common for design work to be delayed while waiting for the survey, even on small projects. How long does it take to do a survey for a 1000 mile long corridor? A while. A long while. It’s a whole lot of work.
All of this footing and survey and money and time stuff is a big part of the reason why much of our border has fences, not walls. Fences only attach to the earth at their posts, making them more of a connect-the-dots kind of exercise than a continuous, inflexible structure that will crack (fall, collapse) if the ground beneath it shifts. Fences are cheaper and faster to build because of this, and they allow some adjustment of construction details in field, meaning you can figure some of it out as you are putting it up. It’s like fencing in a garden plot or field at your house, just bigger, obviously. Over rough terrain like arroyos or rock outcroppings, it’s not easy to build a fence, either, which is part of the reason why some of our southern border has no fence, either.
Once you’ve got a survey and design, you still have to build the wall itself. The simplest possible structure would be a massive project, since it stretches over 1000 miles. If it has, for example, a walkway on top, that adds time and expense. If it has occasional lookout towers or guardhouses or gates, like, again, the Great Wall or Hadrian’s Wall or that iconic fictional wall of our time, The Wall in Game of Thrones, all of those additional features must be designed and constructed and supported structurally. A guardhouse is essentially a building attached to the top of the wall or sitting within the wall itself, and buildings take time to design and build, and they, um, aren’t free. I’ve heard little detail about how the border wall should look or what features it should include, but any structure this large will take a long, long, long time to build. The astonishing cost estimate of the border wall reflects this - bigger structures cost more to build because they use more materials, but also because they take more design time, more survey time, more engineering time, and a whole lot more construction time on site. All that time is someone’s time, and all of it costs money.
How long will it all take? Given the time it takes to put out a call for bids, go through the bidding process for public projects, allow the selected companies to gear up and assign people to work on this, how long until the border becomes more difficult to cross than it is today? I’d bet longer than four years, longer than eight years, in fact. China’s Great Wall is 13,170 miles long (really! although it's more ambiguous than you'd think) and took about 2000 years (!!) to build. Hadrian’s Wall is only 73 miles long and took at least six years to build. (The Game of Thrones Wall was built by magic, and (spoiler alert!) doesn’t exist. Plus it’s made of ice, which is not the material of choice on the Mexican border.) These were built without modern technology, so we’d do it faster. How much faster? Ten years seems like a safe bet, although if anything is certain in life, it is that large construction projects always encounter delays. So bet on delays.
If you want to keep people out of the country with a wall, would you give them ten years’ notice about it? People - in this case, that’s professional smugglers, criminals who do this for a living and charge potential immigrants crippling sums of money - have all kinds of ways of getting around, over, under, and through the existing barriers on the border. How will this be different? In ten years, couldn’t you figure out how to get around (over, under, through) a wall?
Maybe we take another look at building it with magic - somebody call George R.R. Martin! While you’re at it, check with Merriam-Webster, too: you’re gonna need this term.
Assorted drafts, previews, and outtakes from the book I'm currently writing about the impact of vegetation and neglect on urban life. I also take other thoughts for a test drive here, including nascent design and research ideas.