U.S.-Mexico Drug Tunnels Evolving Amid Increased Border Security

Under the corrugated steel plates that divide the U.S. and Mexico in Otay Mesa, dozens of clandestine cross-border tunnels slash through the soil.

As President Trump looks to build new barriers along the border, criminal organizations in Mexico are improving the tunnels they use to smuggle people and drugs under the border fence -- making them smaller and maintaining a high level of sophistication, featuring electricity and railways.

Smuggling tunnels vary in shape and size, but generally fall under one of these three categories, according to U.S. Border Patrol:

• Rudimentary tunnels, or “gopher holes,” are cheaply made and stretch short distances, maybe 50 feet. They are used to smuggle humans or small quantities of drugs under the border.
• Interconnecting tunnels exploit existing municipal infrastructure, linking up with storm drains and sewer lines. They are used to smuggle humans and drugs under the border.
• Sophisticated tunnels can stretch for long distances (the longest ever found was equivalent to the length of eight football fields) and are often equipped with lighting, electricity, ventilation, water pumps, railways and more. They are used to move large volumes of drugs under the border.

In San Diego, tunnels are usually sophisticated, partly because of the highly organized criminal organization operating in Baja California -- the Sinaloa Cartel -- as well as the characteristics of Otay Mesa, a neighborhood that exists on both sides of the border. In the U.S. and in Mexico, Otay Mesa is crowded with warehouses, providing numerous spaces to hide tunnel entry and exit points.

According to the U.S. Border Patrol, in the past three decades, 29 of the 62 sophisticated tunnels that have been found along the U.S.-Mexico border were in the San Diego sector. Meanwhile, of the 197 total tunnels discovered along the border, 62 were in the San Diego sector. These figures exclude about 100 unfinished tunnels found on the Mexican side of the border.

Drug tunnels began to proliferate in response to increased border security, particularly border fence construction launched in the 1990s, according to U.S. and Mexican researchers.

“The more sophisticated our border infrastructure has become, the more the smugglers have upped their game,” said David Shirk, director of the Trans-Border Institute at the University of San Diego.

Shirk said cartels are going as far as consulting with top engineers in Europe to perfect their tunnel architecture.

“And they have every incentive to do so. If it costs $1 million to make a tunnel like that, they can make that back on the first run,” he said.

Drug seizures in tunnels are often in the multimillion-dollar range, which suggests that cartels are making hundreds of millions of dollars on these tunnels.

The 'Tunnel Rats' Get to Work

Lance Lenoir is captain of Border Patrol’s five-person tunnel entry team, known as the Tunnel Rats. When a tunnel is discovered with an exit in the U.S., the Tunnel Rats get to work.

“What we do is assess the tunnel, characterize it, go in, pull out evidence, map it, get rid of it,” Lenoir said.

By “get rid of it,” Lenoir means they fill the tunnel with cement on the U.S. side of the border -- what Border Patrol calls “remediation” of the tunnel. The tunnels often remain open on the Mexican side.

Lenoir said the sophisticated tunnels centered around San Diego are becoming narrower and harder to detect -- ranging anywhere from 36 inches to less than 4 feet in diameter.

So far, the most reliable method of detection has been what Lenoir called “good old-fashioned police work,” with officials pursuing leads from informants who notice suspicious jackhammer sounds, large piles of dirt, or people coming and going at unusual hours. But U.S. federal agencies are now seeking to improve tunnel detection technologies.

Tunnel Detection Technology 'Lacking'

“We need to bring the technology piece. Right now, it’s lacking,” Lenoir said. “I mean we’re talking about a niche problem that doesn’t have any parallel to commercial or industry standard.”

Existing technology -- ranging from ground-penetrating radar to sensors that detect changes in microgravity -- gets thrown off by surface clutter and noise, and there is a lot of cross-border traffic in this area. Radio and electromagnetic interference is another problem. Heterogeneous geology along the U.S.-Mexico border -- a mix of porous, sandy and rocky -- also makes it hard to see what is underground.

Lenoir said he does not know if plans to expand the border fence will affect tunneling. But the cartels keep getting more creative in making tunnels, and he said he wants to make sure the U.S. gets more creative in finding them.

“You can’t go to Walmart and buy those things -- so that’s what we’re working on actively right now,” Lenoir said.

The Galvez Tunnel Remains Open

About 90 feet under Otay Mesa, footsteps from the Cross Border Xpress bridge that connects San Diego and Tijuana, lies a drug tunnel about 6 feet high and 4 feet wide, with lighting and ventilation.

It is called the Galvez Tunnel. Unlike most tunnels discovered in the U.S., this one was left partly open to train the Tunnel Rats. It used to have a rail system for transporting cocaine, marijuana and other drugs. U.S. investigators found the tunnel before it was finished.

On a recent Monday, the Tunnel Rats opened it up to give reporters a tour. Lenoir wore a tan shirt with an illustrated cartoon rat on the back.

“This is like the Cadillac of tunnels,” he said, placing a hand on the sandstone walls, which did not require shoring with cement because they were naturally stable.

Despite the tunnel’s sophistication, tool marks along the walls show it was made with a mere hammer drill, like most tunnels.

“Pure manual labor. Blood, sweat and tears,” Lenoir said.

Cartels Get Creative

Some of the most creative elements of drug tunnels involve the way cartels disguise the entry and exit points. The Galvez Tunnel is a good example of that creativity.

“This one in particular was hid under a bathroom floor that actually raised and lowered to get in and out. We’ve seen elevators, bona fide elevators with up and down buttons, everything but the music,” Lenoir said.

For ventilation, criminal groups often utilize things like leaf blowers and floor dryers.

“My personal favorite is the bounce house blower,” Lenoir said. “Very ingenious.”

The creativity of the tunnels is consistent with Mexican drug cartels’ way of overcoming the border fence above-ground -- using catapults, drones and ladders to get the drugs across, for example.

“The cartels are always trying to innovate and respond to challenges in exactly the same way that any other business does,” said Tom Wainwright, author of "Narconomics," and Britain editor for The Economist. “The message seems to be that whatever technology is used on the U.S. side, the cartels are going to counter with technology of their own.”

Jose Manuel Valenzuela, an investigator for the Mexican border research institute El Colegio de la Frontera Norte, said he does not think tunnel detection technology will ever be good enough to prevent the problem.

If the U.S. and Mexican governments really want to stop drug tunnels, Valenzuela said, they need to chase the massive profits they generate -- in the banks. He said that with existing regulatory regimes, banks are a blind spot for authorities on both sides of the border.

“That’s the large tunnel of the drug market -- the banks,” he said. “Until we look at that perspective, we’ll keep talking about this game of cat and mouse."