Here's Why Donald Trump's Mexico Wall Will Never, Ever Happen
U.S. Border Patrol agents patrol the border fence near Naco, Ariz. in 2012.

Donald Trump makes securing the U.S. border sound incredibly simple: build a wall, make Mexico pay. But, according to two men who have dedicated much of their professional lives to curbing illegal immigration, it's not that easy -- nor does it make a lot of sense.

"What does Trump even mean by a wall?" said Mark Krikorian, executive director of the Center for Immigration Studies, a non-profit research organization that advocates immigration reduction in the United States. "A lot of people use the term wall like 'Great Wall of China' wall, but other people refer to what we have already, which is actually fencing, metal barriers."

In fact, according to Krikorian, one of the major holes in Trump's great wall plan is its lack of, well, holes. Those who spend their time actually patrolling and securing the U.S. border don't want structures of concrete and steel to bolster their efforts. They want a fence, one they can see through.

"The border patrol has no interest in a masonry wall because you can't see what's on the other side," Krikorian said.

Currently, there are already about 700 miles of fencing (not wall) along the 2,000-mile border between the United States and Mexico -- the result of the Secure Fence Act passed under President George W. Bush's administration in 2006.

Krikorian -- who jokes that apart from patrol agents, he's probably spent more time at the border than anybody -- says about half of what is currently in place are vehicle barriers. A few feet high, they are intended to "stop trucks from driving across from Mexico with loads of dope," not keep people from getting across. "You're grandma can hop over those," he added.

The other half is comprised of pedestrian fencing, which is designed to keep people out. Just a small fraction of that entails what border security advocates really want: double fencing -- two layers of barriers Krikorian describes as "optimal for the border patrol."

Trump has proposed building a wall across what he initially said would be the entire 2,000 U.S.-Mexico border, though he has since reduced his estimate to 1,000 miles where a barrier may actually be beneficial. (Krikorian agrees with that part of Trump's plan.) The real estate magnate has given varying estimates for the height of the wall in recent months, ranging from 30 feet to over 60 feet (and whenever Mexico does something he doesn't like, the wall seems to get 10 feet higher) and in December said the wall would be made of concrete and steel.

Trump has clarified that he is flexible in his positions, meaning he may be open to revisiting his solid wall plan and instead look into putting up a fence through which border patrol agents can see.

Peter Nuñez, chairman of the board at the Center for Immigration Studies and former U.S. attorney in the southern district of California and assistant secretary of the treasury for enforcement in the U.S. Department of the Treasury under President George H.W. Bush, believes that's the case.

"I always assume, wall, fence, he was using those terms loosely," he said. "Call it what you want, it's a barrier."

But if Trump were to truly keep his campaign promise and insist that a wall be built, he would leave a lot of border agents unhappy -- not to mention taxpayers.

Were Trump to decide to start from scratch, it would mean tearing down over 300 miles of fencing in Arizona and more than 100 miles of barriers from each California, New Mexico and Texas. It would also entail essentially tossing out the millions of dollars already spent on building. According to data provided by a spokesman for U.S. Customs and Border Protection, pedestrian fencing costs $6.5 million per mile and vehicle fencing $1.8 million per mile, including the cost of design, real estate and environmental planning, construction and construction oversight.

"What do you do with all the fencing that's there? Is he going to tear up the relatively new, pretty good fences that are there?" Krikorian said.

Trump's wall plans would also force him to revisit an area with which he is quite familiar: eminent domain. And if an old woman in New Jersey gave him a run for his money on the issue years ago, he'll have his work cut out for him at the border -- especially in Texas, where most of the unfenced border is located.

"Texas has almost no federal land," said Krikorian. "All of that practically would have to be on privately-owned land, which involves purchasing it, which involves, potentially, lawsuits."

All of this isn't to say that Trump's border security plan is entirely impossible, as long as Trump-the-negotiator is willing to strike a deal.

Actually, Even a Fence Isn't What Immigration Enforcement Advocates Really Want

Nuñez, who has been involved in immigration enforcement since the 1970s, says there is absolutely no question that building fences, putting up lights and installing cameras at the Mexican border has been a "fantastic advantage" in deterring illegal immigration, drug smuggling and other illicit activities. But that's just the tip of the iceberg in addressing the issue at hand.

"As strongly as I support border enforcement, that is not going to solve the problem until we get ahold of the workplace," he said.

Krikorian concurred. "I understand the emotional appeal of fencing, I even understand the political purpose of sort of establishing our determination and commitment to enforce our borders. I get all of that, I don't belittle it, it's just that if we're going to spend the next new million dollars on enforcement, it should be going to visa tracking or workplace enforcement," he said. "That's the kind of thing I'd like to see more effort put on."

Both highlighted mandatory e-verify, an internet-based system that allows businesses to determine the eligibility of employees to work in the United States, as an avenue for improvement, as well as interior enforcement.

"I'm for fencing where it helps the border patrol, but it doesn't just happen when you snap your fingers," he said. "The marginal benefit, the marginal return on investment from the next dollar we spend on enforcement is way bigger in other areas than the fence."

"Do you need more agents before you need fences? Do you need lights before you need the fence? Let the experts decide what is needed most," Nuñez said.

As for Trump's immigration plans, Nuñez says what's on the candidate's website appeals much more to him than what the GOP frontrunner discusses during rallies, debates and interviews.

Krikorian's take was more cutting: "It's sort of bar-stool policy making."

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