SAN DIEGO – A U.S. government effort to find drug-smuggling tunnels underneath the Mexican border with ground-penetrating radar and other high-tech gear has had little success.
Human intelligence, rather than technology, has proved to be the most effective method of finding the passageways. A case in point: The longest tunnel ever found along the border was discovered last week after a tip.
The Homeland Security Department said Monday that a Mexican, Carlos Cardenas Calvillo, was arrested in connection with the 2,400-foot tunnel, which went as deep as 90 feet and was about 5 feet in height and 5 feet wide. He appeared in federal court Monday on charges of conspiracy to import more than a ton of marijuana. A bail hearing was set for Wednesday.
“The problem is the technology picks up some kind of anomaly or variation of soil,” said Lauren Mack, a spokeswoman for U.S. Immigration and Customs Enforcement. “We go in with big backhoes and bulldozers, we spend all day doing it, and all we hit is rock or water tables.”
That was what happened earlier this month when high-tech gear alerted authorities to a possible tunnel near Boulevard, about 60 miles east of San Diego along the Mexican border. A full day of digging turned up nothing.
The technology is “not there yet,” Mack said. “What we’ve seen so far just hasn’t proven itself to be effective.”
U.S. authorities will not say much about the high-tech gear they have tried, saying it may tip off smugglers. But one problem is the sheer size of the U.S.-Mexico border – nearly 2,000 miles.
“It’s a needle-in-a-haystack problem,” said Don Steeples, a geophysics professor at Kansas University who has worked on tunnel detection for 20 years. “In this case, we don’t even know where the haystack is.”
Another drawback: Radar rarely penetrates deeper than 40 feet. Seismic waves can probe deeper, but the technology is less precise.
In 2003, University of Oklahoma experts began using ground-penetrating radar to help Homeland Security find tunnels in California’s Imperial Valley. The radar led U.S. officials to a dirt road behind an apartment building in Calexico, about 120 miles east of San Diego. In 2004, officials drilled 20-foot holes behind the building and found only a water shaft.
Then, nearly a year later, authorities discovered a nearby tunnel, thanks to radar, a video-equipped robot, a drug-sniffing dog and human intelligence, authorities said. That passage – 200 yards long, 3 feet wide and 5 feet high – went from Mexicali, Mexico, to a house in Calexico.
Many tunnels are found by sheer luck. Last week, a Border Patrol vehicle hit a sinkhole near San Diego’s San Ysidro port of entry, the nation’s busiest border crossing, uncovering what officials described as a primitive passage.
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