Detecting tunnels a priority, but progress is hit and miss
By Anna Cearley

May 7, 2003

OTAY MESA - A drug tunnel discovered near the Otay Mesa border crossing in 1993 has become a test site for geophysicists searching for new ways to spot tunnels.

The tunnel never reached its intended destination: a factory on Otay Mesa. Authorities believe it was commissioned by Joaquin Guzmán Loera, a drug trafficker trying to muscle his way onto turf controlled by the Arellano Félix cartel.

Measuring 1,450 feet long and 65 feet deep, the tunnel has been sealed at both ends, but it remains intact underground.

"Almost anybody who has developed any kind of detection (technology) has gone to that site," said Larry Stolarczyk, owner of Stolar, a company that provides technical expertise to the military and the coal-mining industry.

Tunnels can't be found by satellite. Researchers use principles of physics such as radio waves, electrical currents, radar and seismic waves to identify hollow spaces. Their goal is to use these techniques from airplanes.

But challenges abound, because the ground is full of variations and energy sources.

Sometimes readings are thrown off by the false signals from power lines and old stream beds. Some soils have high electromagnetic conductivity, which means they absorb certain wave signals and weaken the readings.

Tunnel-searching technology took a leap forward in the mid-1980s, when the U.S. government asked researchers like Stolarczyk to find tunnels that North Korea was building to infiltrate South Korea.

Four tunnels were found, and Stolarczyk said at least one of them was located using technology developed during the search process. But then the military closed the program.

The war against drugs - and now terrorism - brought tunnels back to the attention of the federal government.

Joint Task Force Six, a unit of the Department of Defense that provides counter-drug support for law enforcement agencies, has access to teams of geophysicists who specialize in tunnel searches.

Since 1996, the teams have investigated 11 potential sites along the southwest U.S. border, according to a task force spokesman. They've found tunnels in about half of those cases, said one researcher who declined to be identified.