Authorities in San Diego have found a tunnel under construction beneath the U.S.-Mexico border:

SAN DIEGO – Mexican authorities, acting on information provided by federal investigators from the multi-agency San Diego Tunnel Task Force, conducted enforcement actions Wednesday targeting a sophisticated, but still incomplete underground passageway that originates in Tijuana, Mexico, and extends more than 860 feet into the United States.

The tunnel, which measures just under 1,000 feet in length overall and reaches a depth of 90 to 100 feet, did not have an entry point in the United States. The passageway has lighting, electrical and ventilation systems and is equipped with an elevator. When Mexican authorities entered the passageway Wednesday morning on the Mexican side, they encountered more than a dozen individuals who were subsequently taken into custody. All of those arrested are believed to be Mexican citizens.

Initial reports indicate the tunnel has been under construction for approximately two years. So far, there have been no arrests in the United States, but the investigation is ongoing.

The press release credits the inter-agency San Diego Tunnel Task Force, which “uses an array of high-tech equipment and intelligence information to pinpoint the location of underground passageways along the border in the region.”

To date, federal authorities have discovered more than 120 cross-border tunnels along the Southwest border. (The photo above is from 2007)

Truth is, these discoveries are typically the result of good, old-fashioned police work, not technology, according to a recent Science Daily story:

“All of them have been found by accident or human intelligence,” said Ed Turner, a project manager with the U.S. Department of Homeland Security (DHS) Science and Technology Directorate (S&T). “None by technology.”

The problem of detecting underground tunnels has frustrated geologists since the 1960s when the Vietcong used them to devastating effect during the Vietnam War. In the 1970s, tunnels were discovered (through intelligence) in Korea’s DMZ. In the 1990s, the Southwest border kept the problem alive, although not a priority.

The terrorist threat, however, has opened the floodgates of money for tunnel detection.

Among the groups at work today on the problem include major defense contractors, the intelligence community, the Department of Homeland Security, numerous components of the Defense Department and unspecified “international partners.”

Technologies under development include a seismic acoustic sensors, infrared sensors and robotics.  Tunnel detection systems are being tested on the ground and the air — aboard helicopters and unmanned drones.

The military’s Joint Task Force North conducted nine tactical missions last year to find underground tunnels using some of these technologies.

Sandia National Laboratories in New Mexico and NORTHCOM worked with the San Diego Tunnel Task Force to test advanced acoustic technologies in Otay Mesa in 2006 and 2007, according to this PowerPoint presentation.

As even a cursory look at PowerPoint makes clear, the sensor data is extremely difficult for the layperson to understand, a problem that was underscored last year when the Department of Homeland Security put out a call for a tunnel detection system that is “simple to understand.”

Lockheed Martin is testing ground-penetrating radar in a trailer towed by a truck as part of DHS’  Tunnel Technologies Detection Project.

DARPA, the Defense Advanced Research Projects Agency, has a Cross-Border Tunnel program to root out underground hiding places that can be exploited by terrorists.

An even spook-ier effort is the Counter Tunnel Operations Working Group, which included the Joint Chiefs of Staff, the Office of the Secretary of Defense, and intelligence community. The group is under the rubric of the inter-agency, anti-terrorism Technical Support Working Group.

At a 2006 Army seminar on tunnel detention, one researcher summed up the state of affairs:

Despite the longstanding effort in the geophysical community under heavy public funding, there is a dearth of success stories where geophysicists can actually claim to have found hitherto unknown tunnels.