IN AGE OF TERROR, U.S. FEARS TUNNELS POSE BIGGER THREAT

Task Force Roots Out Passages As Lawmakers Try to Pass Legislation

SAN DIEGO -- Special Agent Frank Marwood was showing a visitor the
half-mile long, 80-foot deep smuggler's tunnel his agents discovered
beneath the U.S.-Mexican border at Otay Mesa when his cellphone
interrupted.

An agent was reporting in with a startling new find: another tunnel,
this one shorter and more crudely built, but big enough to provide yet
another subterranean port of entry into the USA.

These are busy days for the men and women who guard the nation's
border -- particularly for the team of federal agents charged with
rooting out border tunnels.

The tunnel Marwood learned of last month was the 35th federal agents
have found since Sept. 11, 2001, when terrorist attacks gave a new
urgency to the search.

While drug smuggling and illegal immigration have long been border
concerns, the threat of international terrorists entering the USA by
burrowing under the border has made the effort to detect tunnels a
national security priority.

"Of course they could" be used by terrorists, Marwood says of the
tunnels his team unearths. "The potential is there, and that makes it
unacceptable."

"It's a transnational threat," says Lt. Col. Steve Baker, an Army
engineer who is part of a military effort to support the tunnel
search. "You don't know that they're just bringing drugs through there."

No federal law prohibits building such tunnels. On Wednesday, a group
of senators and House members introduced a bill that would make it a
federal crime punishable by up to 20 years in prison to build or
finance such tunnels. Sen. Dianne Feinstein, D-Calif., said she pushed
the idea after Marwood gave her a tour of the tunnel here.

"What I found was amazing: a sophisticated tunnel, with lights,
ventilation, pumps and a concrete floor," she said. "This really
illustrates the danger -- that smugglers will use these tunnels to
subvert our border checkpoints, trafficking drugs, humans and weapons
under the border."

Marwood, 54, is deputy special agent in charge of the San Diego office
of Immigration and Customs Enforcement, an agency of the Department of
Homeland Security. He is also in charge of the ad hoc task force of
half a dozen agents from ICE, the Drug Enforcement Adminstration and
the Border Patrol who have been detailed to work together to find and
stop the tunnelers.

Agents from the three agencies agreed to set up the team three years
ago and operate out of an office in a nondescript building among the
many featureless industrial buildings and warehouses near a border
crossing at Otay Mesa.

The team was created not on orders from Washington but out of concerns
from agents. The Border Patrol officers were discovering tunnels when
their trucks sunk into the dirt after the ground had collapsed over
shallow passages.

The discovery in January of the sophisticated tunnel brought attention
to the team's efforts and the remarkable string of discoveries over
the past 41/2 years.

The big Otay Mesa tunnel -- with 220-volt cables and pumps for water
drainage -- likely took more than a year to build, Marwood said. It
required sophisticated engineering and moving hundreds of truckloads
of dirt. The money it would take to build it suggests it was financed
by drug smugglers, he says.

Agents brought in sniffing equipment to test the tunnel for radiation
and biohazards. They were relieved when the tests suggested no
nuclear, chemical or biological weapons had been conveyed.

The tunnel discoveries raise the question, however, of how such
large-scale construction projects can go undetected in a technological
age when sonar and other methods can spot mineral veins or treasures
of ancient civilizations.

Detection is complicated by varying types of soil. Don Steeples,
professor of geophysics at the University of Kansas, says soils with
clay or high groundwater tables resist use of ground-penetrating
radar. Some tunnel detection efforts measure the seismic waves from
ground blasts and look for echoes that indicate underground cavities.

"There are technologies that should be able to be made to work in this
environment," James Sabatier says. An acoustic scientist at the
University of Mississippi, Sabatier recently hosted a scientific
meeting with military and other researchers on the problem of tunnel
detection.

The tunnel team is getting help from the U.S. military and its Joint
Task Force North, based at Fort Bliss in Texas, which helps law
enforcement agencies combat drugs and terrorism. Baker says a group of
volunteers from all branches of service are trying out several
technological systems to detect tunnels.

The most promising technique right now is gradiometry, which measures
deviations in the Earth's gravitational forces to detect underground
voids. The group is also testing ground-penetrating radar and seismic
techniques.

"We don't have a silver bullet," Baker says. "There's no one single
method that is 100% all the time in every condition we run into."

The technology is not foolproof. It has produced a lot of bad leads,
such as false readings that prove to be underground drainage, natural
cavities in the earth or sometimes nothing at all, ICE spokeswoman
Lauren Mack says.

The most effective way to find border tunnels has been old fashioned
police work: informers, tips, surveillance.

"We rely on intelligence to get us close to our target areas and then
use our equipment to confirm or deny if we have a subterranean
crossing point," Baker says.

There remains hope that technology will help put the tunnels out of
business.

"Obviously we're working toward being able to find them before they're
completed as opposed to just finding them after they are completed,"
Marwood says. "All of us would like the technology to be farther along
than it is."