Washington Week

Friday Nights on PBS

Donald Trump wants to build a wall on the border with Mexico. Can he do it?


Donald Trump has made immigration a key part of his pitch to be the next president of the United States. At his presidential campaign announcement in June, Trump said that undocumented immigrants were "rapists" and bring "drugs" and "crime" across the southern border. "When Mexico sends its people, they're not sending their best," he said.

The centerpiece of his immigration proposal is to "build a great, great wall on our southern border" to keep undocumented immigrants out, and he "will have Mexico pay for that wall."

That plan has not gone over well with some. "A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," Pope Francis said in response to a question about Trump. Both Democratic presidential candidates have criticized Trump's idea. All three Republican candidates support the idea of a wall or fence on the southern border, but no candidate has gone as far with this proposal as Trump.

All of this is set against the backdrop of the immigration issue, which is once again at hot-button issue in this election. The president's executive actions, allowing young migrants in the country to remain in 2012 and in 2014, allowing temporary status to those in the country illegally, set the stage for a major case before the Supreme Court in the current term and lots of conversation on the campaign trail.

Would a wall work? Is this even realistic? How would Donald Trump accomplish this? We took a look:

How long would the wall be?

The U.S.-Mexico border stretches 1,989 miles, but Trump has said the U.S. only needs to build a wall over 1,000 miles because of "natural barriers" that already exist. For comparison, the length of the Berlin Wall was almost 128 miles. The Great Wall of China, actually a set of noncontiguous walls, stretches over 13,000 miles.

As of October 2014, the federal government has already installed 653 miles of fencing along the southern border. Federal law requires the Department of Homeland Security to construct at least 700 miles of fencing along the southwest border.

How tall would the wall be?

Trump's number is difficult to pin down. The range could be anywhere from 35 to 65 feet. The pedestrian border fence that sits near Nogales, Ariz., is 21 feet high.

How would the wall be constructed?

"Hardened concrete" and "rebar" were the materials Donald Trump mentioned during a December rally in Virginia. However, pre-casted concrete panels -- similar to the ones you see on the side of highways -- could be the way to go, according to civil engineers who spoke with CNN. Other materials, such as cinder blocks or poured concrete, are either too labor-intensive or will not hold up. 

How long would it take to build?

So far, that's unclear. Trump said in an interview last August that "the wall will be under budget and ahead of schedule."

How much would it cost?

Trump has asserted many figures, from $8 billion to "maybe $10 or $12 billion." Experts and fact-checkers certainly believe it would cost billions of dollars to erect the wall, and dispute Trump's figure because he has not explained specifics.  

Remember the 653 miles of fencing that sits on the southern border? It cost more than $7 billion to build, according to analysis by The Washington Post. That means it cost roughly $10.7 million per mile. Multiplying that rate by the 1,336 miles left un-fenced (assuming the whole border would be walled off), it would cost $14.3 billion to do the rest of the border.

Don't forget maintenance of the fence either. The Army Corps of Engineers estimates that upkeep costs could range anywhere from $16.4 million to $70 million per mile over a 25-year life cycle.

Trump keeps talking about how he will make Mexico pay for the wall. Is this possible?

Mexican President Enrique Pena Nieto said in March "there is no scenario" in which his country will pay for the wall. Mexico's treasury secretary agreed with that sentiment and called it "a terrible idea."

Trump said he would get Mexico to pay for the wall by cutting off "the flow of billions of dollars in payments that immigrants send home to the country, an idea that could decimate the Mexican economy and set up an unprecedented showdown between the United States and a key regional ally," The Washington Post reported. Among other items, Trump would change a portion of the Patriot Act that allows Mexican immigrants to transfer money to Mexico, but only if Mexico made "a one-time payment of $5-10 billion"for the wall.

How does would a wall compare to other large-scale projects from history?

Trump has compared his southern border wall to the Great Wall of China. But the Great Wall took several centuries to build, starting around the fifth century B.C. to the time of the Ming Dynasty (1368-1644).

Here's how several other major infrastructure projects compare:

  • The nearly 47,000-mile Interstate Highway System is estimated to have cost $129 billion.
  • The total cost of the Apollo Lunar Program, which eventually put a man on the moon, came out to nearly $170 billion (in 2005 dollars).
  • The Hoover Dam -- completed two years ahead of schedule -- would cost $750 million to build these days.
  • Boston's "Big Dig," a massive highway project that moved a major highway through the city to an underground tunnel, exploded to a cost of nearly $15 billion and was finished eight years behind schedule. 

What would be the possible ramifications for a wall?

A 2009 report by the Congressional Research Service, albeit before Trump's idea to build a wall became public, detailed the possible consequences if the United States chose to build physical barriers along its northern and/or southern borders: "Do the gains in border security outweigh the risk of alienating Mexico and Canada? Should the Mexican or Canadian government's opinions or wishes be taken into account when border fencing is concerned? Given the need to coordinate intelligence and law enforcement activities at the border, should maintaining cordial working relationships with Mexico and Canada take precedence over sealing the border with physical barriers?"


Donald Trump holds a press conference during a visit to the U.S.-Mexico border in Laredo, Texas, in July 2015. [CNN]
The existing U.S.-Mexico border fence. [flickr / BBC World Service]
The Great Wall of China. [flickr / Chris Ford]