[DEBATE] : Holey War: How to Close the Gaza Tunnels

[Yoshie Furuhashi]

<http://www.slate.com/id/2208889/pagenum/all/>
Holey War
How to close the Gaza tunnels.
By William Saletan
Posted Friday, Jan. 16, 2009, at 7:58 AM ET

In the skies over Gaza, Israel rules. Its planes, helicopters, and
drones patrol and fire at will. On the ground, Israeli troops advance
while Hamas lies in wait. But the ultimate battleground isn't visible
from the sky or on your television news. It's underground.

Gaza is riddled with tunnels. Some are for smuggling; others are for
transporting weapons; others are for hiding or ambushing Israeli
troops. The crucial passageways—400 to 600, by recent estimates—run
from Gaza to Egypt, circumventing the closed border. That's how Hamas
gets parts and material for the missiles it fires into Israel. Any
deal to end the current fighting has to include "an effective
blockading" of that border, "with supervision and follow-ups,"
according to Israel's prime minister. To stop the war—and to keep it
stopped—you have to figure out how to stop the tunnels.

But how? Here are some of the options.

1. Buffer zone. Israel used to control a 300-meter strip between Gaza
and Egypt. That wasn't enough to stop Gazans from tunneling under it
to Egypt. But what if the strip were thicker? Would that raise the
cost of tunneling, or the probability of a collapse somewhere along
the passage, enough to deter diggers? Israeli hawks want a buffer zone
three kilometers thick, which would make tunnel excavation much more
difficult, expensive, and time-consuming. Lately, the Israeli Defense
Forces have dropped leaflets urging Gazans along the border to leave
their homes—an attempt, some experts believe, to use the war to widen
the buffer zone. But good luck getting Hamas, the Palestinian
Authority, or European intermediaries to hand over three kilometers of
south Gaza, much less remove the inconvenient residents from their
homes.

2. Wall. Instead of thickening the old buffer zone, how about
deepening it? Years ago, Israel tried a concrete-iron wall that
extended 10 feet underground. A nice try, but fairly useless, since
the tunnels went at least 20 feet underground. Then, just more than a
year ago, two high-ranking officials from the U.S. Defense and State
Departments went to Egypt with a proposal to build a new barrier,
including "piles driven deep into the earth." But even if you extend a
wall far enough underground, tunnelers can dig through it.

3. Moat. Maybe, instead of burying a solid barrier that could be dug
through, we should make the barrier hollow and fill it with water.
That way, anyone trying to dig through would—well, let's just say you
wouldn't want to be there when it happened. This was such an
intriguing idea that Israel tried it several years ago, soliciting
bids for a moat four kilometers long, 100 meters wide, and 80 feet
deep. Estimated cost: $250 million. Israel scrapped the plan because
the water would come from the sea and might contaminate Gaza's
groundwater. But the idea keeps coming back. Two years ago, Israel
broached it again, and Egypt considered it. The U.S. officials who
went to Egypt a year ago raised it again. Even the president of the
Palestinian Authority has lobbied Egypt to do it.

4. Trench. If a moat is too dangerous to Gaza's groundwater, how about
digging the same trench but leaving it empty? That would expose anyone
who tried to get from one side to the other. Israel tried this idea,
too, soliciting bids for a trench five kilometers long and 50 to 80
feet deep. The IDF even bought a 100-ton trench digger from Texas. The
trench was supposed to be only 25 meters wide. But Israel dropped the
plan because, at a minimum, it would have required demolition of 200
Palestinian homes. That's a problem, but less of a problem than the
demolitions required for a buffer zone. And given the current
alternative—smuggling, bombardment in Israel, and war in Gaza—everyone
but Hamas might decide the demolitions are an acceptable price to end
the fighting.

5. Ground-penetrating radar. If a barrier is too hard to build or
can't do the job, maybe sensors can help. That's how the United States
detects tunnels and digging along its border with Mexico. According to
a presentation last month by the Army's Engineering, Research, and
Development Center, we've used several methods: magnetic, electrical
resistivity, ground penetrating radar, electromagnetic, and seismic.
All of these methods involve sending waves into the ground and
identifying anomalies on the rebound.

Some of the methods look unsuitable for Gaza. But what about
ground-penetrating radar? This was a favorite tool along the Mexican
border until tunnelers discovered its limits: It can't see deeper than
one meter in wet dirt or 15 meters (49 feet) in sand, dry soil, or
rock. At that point, all the tunnelers had to do was find the right
terrain and dig under the range of GPR, making it obsolete. Good news:
The ground around Gaza is dry and sandy. Bad news: Gaza's tunnels
already go 50 to 60 feet deep. So GPR may not be up to the job.

6. Electromagnetic gradiometry. This might solve the depth problem.
Originally developed for the demilitarized zone between North and
South Korea, it detects underground voids by discerning slight
anomalies in electromagnetic or gravitational fields. Companies that
sell EM gradiometers try to keep the range secret, so they don't
become obsolete like GPR. One published account estimates their
outside range at 150 feet. That's deeper than any known Hamas tunnel.
Still, it leaves the problem of administration. The IDF abandoned its
strip on the Gaza-Egypt border four years ago because it was too hard
to defend. Who's going to operate the machines?

7. Drone-operated gradiometry. Here's an idea: Put the tunnel sensors
on unmanned aerial vehicles. Supposedly this has been tried
successfully at least once on the U.S.-Mexico border. A year ago, the
Department of Homeland Security told Congress that DHS was
"experimenting with UAV mounted digital electromagnetic gradiometers."
A presentation from the DHS Science and Technology Directorate depicts
a team of drones (see Slide 27) using gradiometry to sniff out
tunnels. The drones selected for the assignment are already available,
"fully autonomous," can fly for 10 hours, and have "a data link range
of up to 22 nautical miles." Or the IDF could modify its own drones to
do the job. So Israel wouldn't need sitting-duck ground forces to
monitor tunnels and diggers. It could hunt them from the air.

8. Automatic sensors. If you don't want drones along the border, you
could try "acoustic" or "seismic" sensors. These require no operators
and, according to a research paper that accompanied last month's Army
presentation, can detect digging or movement in a tunnel even in
conditions that "confounded GPR and electromagnetic techniques." The
Army has field-tested a network of buried acoustic sensors in Iraq,
with "overwhelming success," the paper reports. This network, which
the Army now calls the Tunnel Activity Detection System, consists of
buried sensors ("geophones") that are connected by an underground
cable and transmit data to an operations center "via a satellite
uplink." Theoretically, the geophones could be buried along the
Egypt-Gaza border, and the operations center could be in Tel Aviv.

The U.S. Army Corps of Engineers is already working with Egypt on such
a system. Recently, the United States allocated $23 million to Egypt
for tunnel sensors. Two months ago, Ha'aretz reported that the corps
was teaching Egyptian soldiers how to find tunnels using "instruments
that measure ground fluctuations." Last week, the Washington Post said
the corps was helping Egypt find tunnels with "sonar equipment."
Apparently, what worked in Iraq is now being tried to Gaza.

Unfortunately, Israel doesn't trust Egypt to police the tunnels. Could
Israel's defense industry build a similar system? It already has.
Sonic Lynx, a firm based near Tel Aviv, advertises "an array of
seismic and acoustic sensors deployed in the ground" that relay data
"to a remote control and display station, where security personnel can
view the classification of the threat together with its accurate
location." Meanwhile, Electro-Optics Research and Development, a Haifa
company that specializes in acoustics and seismology, has developed
seismic antennas that can identify underground threats. Sonic Lynx
recently lobbied the IDF to put its sensors under the Israel-Gaza
border. In fact, Israel already has experience using acoustic sensors
to hunt tunnels along Gaza's border with Egypt.

9. Statistical bombing. Having failed to block the Egypt-Gaza tunnels,
Israel is now bombing them from the air and shelling them from the
sea. Some tunnels were picked out beforehand—the Israeli Air Force hit
40 in a single night—but in other cases, according to Yedioth
Ahronoth, the IAF "dropped at 10-meter intervals 600 kg bombs with
timing devices, which 'statistically' hunt the hidden tunnels." If
Israel can't get a deal to block the tunnels with sensors or a
barrier, it might have to resort to "statistical" bombing again. That
could mean a bombing campaign along the border every three to six
months—the length of time it takes diggers to complete new tunnels. An
ugly prospect, to be sure. But not as ugly as what's going on right
now in Gaza.

(Human Nature thanks Slate interns Jennifer Akchin and Gage Newman,
who tunneled through the Internet to bring back the parts that were
assembled to make this article.)

(Now playing at the Human Nature blog: 1. Why old people don't cause
more car crashes. 2. Why cell-phone users do. 3. The beauty of
adjustable glasses.)

William Saletan is Slate's national correspondent and author of
Bearing Right: How Conservatives Won the Abortion War.

Article URL: http://www.slate.com/id/2208889/