Impacts on Water During Well Drilling

The Marcellus Shale in New York lies 3000 to 5000 feet below the surface. In the area of New York underlain by the parts of the Marcellus shale likely to be exploited for natural gas, groundwater suitable for human use is generally at depths of less than 500 feet. Even though there is groundwater at deeper depths, this water is generally too high in salts or other solutes to be used for drinking, irrigation and most industrial processes. Therefore, most of the concern regarding the potential impact of the process of gas drilling on groundwater resources is focussed on drilling through the first several hundred feet in areas that contain utilized groundwater aquifers. The New York State Department of Environmental Conservation (DEC) requires drillers to use only air or freshwater when drilling through freshwater aquifers (http://www.dec.ny.gov/docs/materials_minerals_pdf/dgeisv1ch9.pdf)

As drilling proceeds, the bore hole created is cased and sealed to surrounding rock with cement. From the surface to the depth of potable groundwater, the bore hole will be sealed with multiple casings. If the bore hole is not properly sealed, it is possible for water in aquifers near the surface to leak into lower aquifers, or water from deeper aquifers, water used in drilling muds and hydrofracking to move into surface aquifers. Hence, it is very important that the bore hole be well sealed. The New York State Department of Environmental Conservation (DEC) mandates casing and cementing (http://www.dec.ny.gov/energy/1536.html) of well bore holes. Since any water from higher layers that enter the gas play would likely have to be pumped out, it is also in the interest of the gas well owner that the bore hole be well sealed.

In addition, wells or well pads must be a prescribed distance (known as a setback) from municipal water wells (1000 to 2000 feet), reservoirs and controlled lakes (300 feet), streams, ponds and private wells (150 feet) (dSGEIS 7.1.12).

Some Marcellus shale gas wells could be located within the boundaries of the watershed in which New York City has reservoirs. The city has several concerns regarding gas well drilling within their watersheds including the possibility of fractures existing or being created that would allow for seepage from the Marcellus shale into their water supply system and contamination of their water reservoirs from gas well activities at the surface (http://www.nyc.gov/html/dep/pdf/natural_gas_drilling/nycdep_comments_final_12-22-09.pdf).