"A U.S. Geological Survey study of Butler and surrounding counties found thousands of acres of land and forest disturbance because of Marcellus shale and traditional gas well drilling."

"The USGS study examined aerial images from the National Agriculture Imagery Program taken between 2004 and 2010.

In Butler County, 109 natural gas extraction sites resulted in more than 324 acres of disturbance, including about 13 miles of new roads, according to the most recently released study.

The disturbance was concentrated in the northeastern portion of the county."

Jodi Weigand reports for the Pittsburgh Tribune-Review September 29, 2013. [2]