Fun fact: the US/Mexico border is 1,954 miles long.
Fun fact: the Great Wall of China contained about 3,889 miles of actual wall - we don't want to count the 1,500+ miles of trenches or rivers. No sir, nothing but real wall for us.
So our Great Great Wall will be just a few miles less than 1/2 the length of the Great Wall. That shouldn't be a problem - certainly less difficult than building a 95 story skyscraper... after all, our Dear Leader told us that long ago.
Big question: how high should we build our Great Great Wall?
Hmmm, former Arizona governor Janet Napolitano was famous for saying: "Show me a 50 foot wall and I'll show you a 51 foot ladder."
Poppycock, I tell you! She should have checked: the tallest ladder for sale at Home Depot in Mexico is 40 feet tall. That means there is no such thing as a 51 foot ladder in Mexico.
So we'll make our wall 50 feet tall just to be safe.
Next up, we know these pesky Mexicans just love to dig tunnels - remember El Chapo? So we need to dig our Great Great Wall in deep. Let's go for 30 feet, and we'll put some surprises down at the base for anyone who thinks they can get past us. We'll add the caveat that we only have to dig until we hit bedrock, so we might save some digging there.
In order for our wall to be not just great but Great Great, it's gonna have to be thick, too. We'll do the detail design later - after our (soon-to-be) Maximum Leader for Life appoints a Great Great Manager for the project - but for now, let's just go for a round number..... 10 feet.
Let's do a SWAG (Scientific Wild Ass Guess) and a ROM (Rough Order of Magnitude) to see what we're looking at for this project.
We've got dimensions: 80 feet high from the bottom of the foundation and 10 feet wide. That's 800 square feet of cross-section, but concrete is sold in cubic yards, so let's see how much we need:
800 square feet / 9 feet per yard = 89 square yards cross-section
1760 yards per mile * 1954 miles = 3439040 yards
3,439,040 yards * 89 square yards = 306,074,560 cubic yards of concrete needed
For reference, the Hoover Dam contains 3,250,000 cubic yards of concrete.
That seems like a lot of concrete, but as we know (or don't, but soon will) concrete is composed of cement, sand, aggregate (fancy word for rocks) and water. We'll leave the last 3 ingredients for now and concentrate on the cement.
To make a yard of average-strength concrete, we'll need about 6 bags (90 pounds each) of cement. More calculations:
540 pounds per yard * 306,074,560 yards = 165,280,262,400 pounds of cement
Divide by 2,000 pounds per ton = 82,640,131 tons of cement needed
That sounds like a whole lot of cement, so let's check how much is produced in the US in a year:
In 2013, the USA produced 77.8 million tons of cement.
Ummm, Houston, we have a problem. Luckily, China produced 2,480,000,000 tons of cement in the same year, and their economy is slowing down, so maybe they'll have some to share. We'll have to have Carl Icahn ask them about that, eh?
Let's keep looking at this after the little bump in the road.
Cost is no issue, of course, because our Maximum Leader has told us many times 'I'm really rich', but let's take a look anyway.
Average concrete cost is about $150 per yard, plus about $100 per yard for delivery. We're not building an average wall, but let's use $250 per yard anyway:
306,074,560 yards * $250 per yard = $76,518,640,000 cost of concrete
Now keep in mind that this is concrete suitable for a driveway, not a Great Great Wall. We're going to need better cement and a lot more rebar. Why more rebar, you asked? Good question.... concrete by itself isn't very strong, especially against impact, like a bunch of people banging on it with sledge-hammers. It's the rebar (steel reinforcing bars) that makes it strong. I'm not going to go into a long calculation on how much rebar we need.... I think you'll believe me when I guess it will be a sizeable percentage of the steel production in the US for the year.
Let's leave the cement and move on to another issue: how are we going to get all of this cement, sand (you can't use just any sand), aggregate and water, to say nothing of the concrete mixing plants, wood for forms, workers, etc., etc., etc. to the border? I just looked at the entire US/Mexico border (the wonders of Google Maps!) and found there are almost no roads within a few miles of the border. Uh-Oh!
Looks like we're going to have to build a 1,954 mile road along the border, along with another 1,000 miles of access roads to get there. Let's see.... asphalt costs.... no, wait, I'm not going through that again. Let's use $10 million per mile to get us $30 billion cost for our access roads.
There's also 2 rather large lakes right on the border in Texas... I guess that will be a management decision how to deal with them.
Oh, and as my wife (also an engineer, BTW) pointed out: we're building roads to these desolate areas where no-one in their right mind would ever cross the border because it's an un-tracked wilderness, so anyone who manages to get over or under our wall won't have any difficulty moving north.
Returning to our Great Great Wall, let's consider that an average of 3,500 men poured 160,000 yards of concrete per month for 2 years to build a structure with about 1/100th the size of our wall. We'll get lots of savings using modern tools and techniques, but it's still going to take just about every concrete installer in the country.... which doesn't matter much when you consider we're going to need all the concrete produced in the country in order to get this done in a year.
Let's say we're 10 times as efficient: we need to pour 159 times as much concrete per month with 1/10th the manpower, so that means we need about 55,650 workers. Most of the border is really desolate, so we have to feed and house them.... let's figure fully-burdened labor costs at $100 per hour (ridiculously low, IMNHO) so that's about $1.1 billion per month.
I'm not sure what the total estimated cost for our Great Great Wall would be - too many variables - but suffice to say it would be at least a couple hundred billion dollars, provided, of course, you can get all the materials and labor you need.
Oh, one more thing: a good bit of the land on the border doesn't belong to the US government, so we'll have to work out how to buy it. I'd say 'just take it', but that might get the Cliven Bundy crowd frothing at the mouth again, and we don't want that, do we?
And, of course, all of our calculations will have to be re-done if Home Depot decides to sell a 60 foot ladder in Mexico, but let's not go there, OK?
At least our Illustrious Poobah has told us that Mexico will pay for it!
LATE BREAKING: Scott Walker, in a desperate attempt to prove that he's still relevant, has floated the idea of a wall on the border with Canada!!!
Let's see..... the US/Canada border is 5,525 miles long...... the tallest ladder for sale at Home Depot in Canada is 60 feet, so we better go for 80 feet high....... we'll have to cross the Rocky Mountains with this wall, as well as 4 of the Great Lakes and a lot of the border in Alaska is virtually inaccessible, but none of that matters!
I'm just really, really glad that nobody in Central America has ever gotten the idea to build a boat and sail to Florida.