By P.J. REILLY, Staff Writer
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Scientists taking a first-ever look at what lies beneath Lebanon and Lancaster counties are scheduled to begin work today.
The seismic study, being conducted by geologists with the state Department of Conservation and Natural Resources, is expected to last five weeks, with work crews beginning in the Grantville area today and then proceeding south through Lebanon County and the entire length of Lancaster County.
According to Jay Parrish, director of DCNR's Bureau of Topographic and Geologic Survey, these crews will be systematically vibrating the ground and then charting the sound waves to map out what the subsurface looks like down to about 30,000 feet.
"It's like a new world no one has ever looked at," Parrish said. "We have no idea what's here."
The work crews will be conspicuous as they move through the two counties, creeping along at 2 miles per day with a caravan stretched out for six miles alongside local roads.
"I'm sure there will be quite a few people wondering what the heck is going on," Parrish said.
Over the past several weeks, DCNR has attempted to notify by mail the owners of some 1,400 properties along the 50-mile route the crews will follow through Lancaster County, just to let them know of its plans.
The planned route stretches from the northern end of the county to the southern end, generally near the middle of the county, paralleling the Susquehanna River.
"The goal is to gather the necessary data with a minimum of inconvenience to the public," the letter mailed to property owners states. "You should notice minimal, if any, disruptions to your daily activities."
DCNR is studying Pennsylvania's geology as part of the requirements of House Bill 2200, which was signed into law in October by Gov. Ed Rendell.
The bill orders DCNR to evaluate the state's potential for "geologic carbon sequestration."
That's a process in which carbon dioxide emissions are captured at coal-fired industrial plants and injected deep underground instead of being released into the atmosphere.
Preliminary studies and general knowledge of Pennsylvania's geology suggest it is well suited for geologic carbon sequestration, which requires underground reservoirs at least a half-mile long that are sealed by impermeable layers of rock, DCNR's Web site states.
Parrish, director of Lancaster County Geographic Information Systems department from 1997 to 2001, said scientists already know what lies beneath many areas of Pennsylvania, where coal mining and gas- and oil-well drilling have been going on for years.
But the southeast corner of the state, including Lancaster County, is unexplored territory, since gas and oil drilling are not done here.
To understand what the county's underside looks like, Parrish said, a truck called a "Vibraseiser" will crawl along the shoulder of county roads vibrating the ground.
"If you're standing right next to it, you'll feel the ground shake," Parrish said. "But if you move back just a few feet, you won't feel anything."
Sound frequencies from the vibrations will travel down through the earth before returning to the surface.
Six miles of cable, fitted with a series of seismometers, will be stretched out in front of and behind the Vibraseiser to capture the returning sound frequencies.
The data will then be plugged into a computer to provide a picture of the underground's composition and formation.
Parrish said the cable will be laid only on public right of ways adjacent to roads.
In many places, however, those right of ways extend into people's lawns and driveways.
"People consider it to be their property, but it's actually a right of way," Parrish said.
When a cable is stretched across a driveway, it will be covered with a rubber mat that can be driven over, so access to that lane will not be blocked, Parrish said.
Any damage to property that might be caused by the project, such as a truck tire sinking into soft earth on a lawn, will be repaired by DCNR, according to Parrish.
"But we really don't expect there to be much damage, if any," he said.
State geologists will travel with the work crews to answer questions property owners or others might have.
"The geologist will not be able to show you the 'picture' of the ground under your property until the data are processed," the mailed letter states. "After that, all the information and an explanation will be available on the DCNR Web site, free of charge."
Besides searching for potential carbon sequestration areas, Parrish said a seismic study of Lancaster and Lebanon counties will provide other valuable information, such as the type of soils and rocks located deep beneath the surface and the location of fault lines and sinkholes.
E-mail: preilly@lnpnews.com
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