THE NATURAL CONTROLS OVER THE NATURAL WATER QUALITY OF POTABLE GROUND WATER IN THE APPALACHIAN BASIN OVERLYING DEEP MARCELLUS AND UTICA SHALE GAS DEVELOPMENT: A REVIEW OF THE CHESAPEAKE ENERGY CORPORATION WATER QUALITY DATASET

The USEPA (2015) recently published an extensive and long awaited draft report on potential water quality impacts caused by unconventional drilling for oil and gas. In their review, EPA found minimal water quality impacts and no systemic water quality problem in any basin across the country caused by unconventional gas and oil development. Herein, we report results of additional baseline (pre-drilling) sampling for methane in 13,040 potable ground water samples in Northeastern Pennsylvania and 8,004 samples from a “Western Area” (southwest Pennsylvania, eastern Ohio, and north-central West Virginia) that were collected on behalf of Chesapeake Energy Corporation as part of its pre-drill monitoring program.

Our conclusions independently agree with EPA’s. Methane naturally occurs in most shallow aquifers used for drinking water in the Appalachian Basin, sometimes exceeding action limits set by Regulatory Agencies. More dissolved methane, iron, manganese, barium, and other redox sensitive solutes occur in waters with hydrogeochemical facies types trending towards Na-Cl and Na-HCO₃ , and these waters usually are tapped in water wells along the flanks of ridges and hills and in valleys, where they intersect deeper and older groundwater flow paths nearer to a freshwater-saline interface. The occurrence There, thermogenic methane, ubiquitous in the basin, often occurs in potable waters within a few hundred feet of the land surface. Natural ion exchange adds sodium to water as it moves along flow paths, leading to almost ubiquitous exceedences of regulatory advisories for sodium concentrations in ground water.