An analysis by an environmental group finds hundreds of cases in which drillers used diesel fuel without obtaining permits and sometimes altered records disclosing they had done so.

For years, the U.S. Environmental Protection Agency has been frustrated in its efforts to pursue hundreds of cases of water pollution — repeatedly tied up in legal fights about exactly what bodies of water it has the authority to monitor and protect.

There are more than 6,000 active gas wells in Pennsylvania. And every week, those drilling sites generate scores of complaints from the state’s residents, including many about terrible odors and contaminated water.