Less than half a mile from the U.S. Port of Entry at Otay Mesa in San Diego County, Mexican drug smugglers operated an elaborate 2,400-foot tunnel that connected a small warehouse 175 yards south of the border near Tijuana’s Rodriguez International Airport to a larger 50,000-square-foot warehouse on Siempre Viva Road on the U.S. side of the border.
When found in 2006, the tunnel was equipped with rails, electric lighting, ventilation ducts, and a sump pump to handle groundwater drainage. The Mexican entrance had an 85-foot-deep cement-lined vertical shaft with a pulley system to lower drugs on a gurney attached to a rope, according to the Drug Enforcement Administration. At its deepest point, the tunnel, which averaged 6 feet high by 4 feet wide, ran more than nine stories below commercial warehouses and busy border roads in U.S. territory.
No one knows how much marijuana or other drugs entered the United States through the tunnel, although at the time of its discovery pallets containing approximately two tons of marijuana were seized on the Mexican side and another 200 pounds were seized on the U.S. side.
The U.S. Immigration and Customs Enforcement, which investigated the case along with the DEA and U.S. Border Patrol, did not know how long the tunnel had been in use. It’s also not the first lengthy tunnel found in the area. A similar 1,000-foot passageway was discovered nearby in 1993, although it was unfinished when found.
“Since the early 1990s, we’ve had over 150 tunnel attempts along the Southwest border, 137 of which have actually crossed the border,” says Jose Garcia, deputy special agent in charge for ICE Homeland Security Investigations in San Diego, which includes leadership of the ICE Tunnel Task Force (TTF). TTF is composed of elements of the Border Patrol, Drug Enforcement Administration, and, to a lesser degree, the California Bureau of Narcotics Enforcement. Garcia says tunnel detection at the border is a full-time job, in the sense that the TTF crew handles no other types of investigation.
“We spend most of our time following leads and tips,” Garcia says.
Found tunnels are eventually remediated, which involves filling or otherwise impeding passage through the crude shafts and closing exit points located on United States soil.
Some of the larger ones are first plugged before they can be filled up with a material ICE declined to identify. Plugging a tunnel is not as simple as it sounds. A 6-foot diameter hole must be drilled through the earth into the actual tunnel so a concrete obstruction can be created.
The hole truth
As border security has tightened since the terror attacks of 9/11, drug smuggling, and to some extent human trafficking, has gone increasingly underground. Of the 150 or so tunnels found, none were discovered using detection technologies, simply because no reliable tunnel detection technology exists.
Ground penetrating radar, or GPR, has been in industrial use for more than 40 years and has become the gold standard for such varied work as scanning roadbeds for subsurface voids, locating unmarked graves, mapping underground utility lines, and searching archaeological sites.
GPR is also used for tunnel detection but the depth penetration limits of GPR is something around 40 feet in the best soil conditions, making it of limited utility. Some discovered border tunnels are over twice that deep. GPR also does not work well in damp clay-like soil, where penetration is only a few inches. GPR technology is also prone to false alarms that waste time and money.
“For us, GPR is better at detecting buried tunnel openings than finding tunnels themselves,” Garcia says. “It’s been quite successful finding openings where a tunnel may be exiting or starting.”
The limits of GPR are well-known, even to drug smugglers. They simply dig their tunnels deeper than the technology can detect. Garcia says one place GPR has been used reliably is to find voids in walls where drug cartels hide money.