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Key Indicators for Understanding Our Region

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Environment / Marcellus Shale Drilling

No subject has attracted the attention of the Pittsburgh Region as has the explosion of interest in deep-well gas drilling into the Marcellus Formation; a shale formation thousands of feet below the land surface.

Unconventional oil and gas wells, such as those drilled into the Marcellus Shale have several impacts on the region's water. First, each well takes millions of gallons of water to stimulate production with a process known as hydralic fracturing. Second, much of that water returns to the surface, with chemical additives and subsurface contaminants, which must be disposed of in some way. And third, spills and accidents at the well site or other locations can pollute streams and groundwater sources.

This map shows the number of unconventional wells drilled in PA to date (in orange) as well as the number of permits issued (pink) and violations (yellow).

Data source: PA DEP via