There is also the potential for contamination of groundwater by substances found in wastewater. It
is important to examine environmental problems experienced in other sites of active natural gas development,
though comparisons among different reservoir rocks (e.g., tight shales, tight sands, and coal bed methane) must
also consider the geologic differences between them. For more information on the differences among reservoir rocks and how they relate to contamination, please see Marcellus Shale Issue5: Jointing and Fracturing. For example, reports of
BTEX contamination and attendant health effects have been associated with natural gas drilling in coal bed
methane formations in Sublette County and Pavillion, Wyoming and tight sands in Garfield County, Colorado.