Idaho National Laboratory has a portable tunnel detector. This could be used to help detect tunnels under the border between the United States and Mexico and for detection of tunnels around Israel.
Here are some highlights.
* INL engineers have built a lightweight, portable device capable of detecting tunnels or weapons caches through 75 feet of solid earth.
* The LAS (Look-Ahead Sensor) works in sandy or rocky soil, dry ground or wet.
* The machine is portable—it weighs only 25 pounds or so—and relatively cheap.
* The LAS could potentially be mounted on an autonomous vehicle, picking its way through the creosote flats and saguaro-studded slopes of the border country, pausing every 30 seconds or so to take a reading.
These underground sensors can be combined with Smart Dew sensors. Smart Dew: 25 cent sensors can enable a 10 mile deep X 2000 mile sensor grid for border security for $10-100 million including base stations. This should change the debate and dynamics of the border security issue.
The LAS transmits acoustic waves into the earth, starting at around 50 cycles per second, or hertz. Over the course of one eight-second run, the frequency ramps up to about 200 hertz. While this is happening, an onboard motion detector measures how the waves shake the dirt and rock through which they pass. The LAS exports these values to a laptop computer, where special software can graph and analyze them.
When the assayed earth is solid, the resulting graph shows a rapidly rising line: as frequencies increase, the soil shudders more and more violently, in a continuous and predictable fashion. But if there's a void underfoot, the graph shows a humped peak or dip. This is because sound waves hitting empty space tend to behave differently. They either amplify or interfere with each other, causing a spike or drop on the graph. Once the LAS detects a void, the laptop figures out how far away it is in a matter of seconds using a mathematical formula that links frequency, the speed of sound and distance.
Despite its successes, the LAS remains a prototype, and West is hoping to attract more funding to improve its design and performance.
More than 100 border tunnels have been discovered since 1990, 23 in 2008 alone. Some of these contraband conduits are incredibly elaborate, the work of sophisticated criminal syndicates. In 2006, for example, officials unearthed a 2,400-foot-long tunnel connecting a Tijuana industrial building to a San Diego warehouse. According to the San Diego Union-Tribune newspaper, the tunnel went 85 feet down at its deepest point, and its builders, likely a Mexican drug-smuggling organization, outfitted it with ventilation and pumps to clear out seeping groundwater.
The Look-Ahead Sensor, or LAS, weighs just 25 pounds and is powered by off-the-shelf rechargeable batteries. Anything could be coming into the U.S. through these tunnels—people, drugs, weapons—so underground passages pose an obvious national security risk. But effective, proven tunnel-detection technology has yet to be deployed along the Mexican border. All tunnels discovered to date have been found by luck—such as a truck sinking through a shallowly dug section—or old-fashioned detective work.
Competing Tunnel Detection Technology
Ground-penetrating radar goes down only 40 feet or so in the best of conditions, and it does not work well in clay or moist soils. Microgravity equipment is expensive and must be held perfectly level, and at a constant temperature, when taking readings. A stationary tunnel-detecting electrode system would be huge, costly and prone to tampering. And the Israeli fiber-optic technique only detects digging, not existing tunnels.