Geophysicists at Ohio State University have found a new application for ground penetrating radar - detecting subsurface liquid hazardous waste.
By changing the antenna configuration within a standard ground penetrating radar (GPR) device, they were able to detect deposits of creosote buried beneath an EPA clean-up site in Marion, Ohio. The technique may hold promise for finding other buried hazardous waste.
Jeffrey Daniels, professor of geological sciences, and his students found several deposits around an abandoned wood treatment facility, including two tanks of creosote beneath 1m of concrete.
They reported their results in a recent issue of the journal Geophysical Research Letters.
'Without this new antenna arrangement, we never would have found the tanks, 'said Daniels.
How well GPR detects objects depends on the alignment of the sending and receiving antennas, he said.The common arrangement - the two antennas side by side - detects smooth objects like buried pipes or flat layers of rock well. But jagged objects such as broken rocks confuse because they scatter the radar signal.
The geophysicists showed that crossing the antennas into a T-shaped formation brings into focus coarse deposits of hazard- ous waste mixed with rocks and soil.
At the Marion facility the Ohio EPA and the US EPA had been unable to pinpoint how creosote had leaked from the property into the nearby Little Scioto River.
The geophysicists'map created by the sideby-side configuration showed a messy jumble of signals. But the cross-pole test produced a cleaner signal. Glowing bright red on the 3-D maps were several well-defined areas that contained foreign material - the creosote.
The geophysicists detected creosote in a pit near a former pump house, and in a trench connecting two cement pads that supported the missing storage tanks. It also detected creosote beneath the tank pads. 'We thought they were there to support the storage tanks, ' said Daniels.
Two months later, the EPA broke through the concrete pads and uncovered another two tanks of creosote leaking into the surrounding soil.