The circuit emits a magnetic field at 380 hertz that follows any groundwater it finds, Rollins says, "because water's really the best conductive [material] under the ground." The greater the amount of saturation, the greater the magnetic field, which emanates upward where it is recorded by Willowstick's surface sensing instruments. The gathered information is uploaded to computers at Willowstick's facilities, where researchers follow the thread of any 380 hertz readings to map the flow of underground water sources.
This will help determine the source of the leak, even if the leak is under the dam, Hughes says. "All dams leak to some extent," he adds, "but we don't want them to get out of hand."
U.S. companies have used AquaTrack to map dam seepage as well as determine the extent and location of groundwater those companies may have contaminated. Once a company that owns a plant or mine, for example, discovers it has polluted the local groundwater (or has been ordered by the U.S. Environmental Protection Agency to investigate the possibility that it has), the only real way to understand the problem to this point has been to dig a series of wells—generally six inches in diameter—to sample soil and underground water for contaminants, Rollins says.
Companies generally pay up to $120,000 to drill each well, so "they're not going to want to put 100 holes in the ground," Rollins says. "By creating theoretical flows in a modeling environment, the scientists can create theoretical magnetic fields," he adds. "They will then model these flows until the theoretical fields match [the data] collected in the field. Once they get the shape of the theoretical anomaly to match the actual data, then they can accurately determine depth of the dam seepage or groundwater." The goal here, as when the technology is used to find dam leaks, is to inform engineers as precisely as possible where they should drill to either pour concrete (in the case of a leaky dam) or take water samples to find the route of the contaminated water.
AquaTrack is designed to function much the way an MRI or X-ray is used locate a health problems within the body prior to surgery. "You wouldn't walk into a doctor's office and tell them to cut you open to find out what's wrong," Rollins says. "You'd first want to get an X-ray or MRI."
Of course, AquaTrack is not the only technology that allows scientists and business prospectors to better understand what lies beneath. Oil and gas companies for years have used the techniques of blasting or pounding into the ground and measuring the resulting shock waves to determine a site's crustal composition and, more importantly, where they might want to drill. "The acoustic signal travels through the Earth, and at each rock layer interface some of the signal bounces back up to the surface to be recorded by the sensor array," says Alex Krueger, vice president of research, development and marketing for Headwave, Inc., a Houston-based maker of software that can make maps out of raw data. "Thus, an image of the subsurface layers can be created."