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On-site Pollution

Natural Gas Well Site, Dimock, PA

Natural Gas Well Site, Dimock, PA. Photo © 2010 J. Henry Fair

Pollution at the Well Site

There are a large number of on-site environmental impacts associated with natural gas drilling operations in the Marcellus Shale. Another section of this website has already addressed the obvious impacts associated with deforestation to clear land for well pads and roads. Once a drilling site is constructed and extraction begins, there are a number of additional environmental impacts that occur related to the water use and disposal at the site, release of toxic compounds into the air, and incidental impacts such as noise and light pollution.

Water pollution

As noted elsewhere on the site, the hydraulic fracturing process requires a vast amount of water. The horizontal wells used in the Marcellus Shale require from 1.5 million to 9 million gallons of water over the course of the fracturing process (which takes 4-6 weeks and is completed before extraction begins). Added to this immense volume of water are several tons of a mixture of toxic chemicals, sand, and salts that facilitate the fracturing process underground. Approximately 30-40% of the water used for fracturing returns to the surface contaminated with compounds added by the industry such as surfactants and detergents, salt, metals, fracturing chemicals, oil, and grease, as well as anything picked up underground such as a variety of suspended solids. Disposal of this contaminated water is an important concern. In some areas, the water goes through the local wastewater treatment plant. However, most of the wastewater treatment plants in the areas where extensive drilling occurs are rural, small-scale, and ill-equipped for dealing with the huge volumes of wastewater produced by the natural gas industry and many of the compounds included in the wastewater.

There are a few on-site options for dealing with wastewater from fracturing. Many gas companies pump the contaminated water into large open on-site pits where it evaporates. The pits are prone to overflow during periods of heavy rainfall and are lined with plastic that can be easily punctured. The pits therefore require constant monitoring to avoid any leakage and contamination of soils and groundwater. Numerous complaints of contaminated groundwater where drilling is occurring suggest that monitoring of wastewater pits is currently not as effective as it should be. Another on-site option is the injection of wastewater into deep injection disposal wells. However, this option runs a high risk of contaminating groundwater and could pose significant long-term dangers. It is unknown what effect the process of hydraulic fracturing has on the stability of the geology of the shale region and the potential for release of toxic chemicals in the future should be taken into consideration. The third on-site option consists of storage of wastewater in tanks followed by transportation to larger wastewater treatment facilities. This option requires additional legal work and financial input on the part of gas companies who must negotiate a lease for on-site storage with the land owner and entails some risk of contaminated water leakage from the containers or during filling.

Aside from concerns about the disposal of wastewater from the fracturing process, there is some concern that contaminated water could escape from wells at the surface of the drilling site and underground through leakages in the concrete casing of the vertical portion of the wells. It should be noted also that the horizontal sections of the wells are not cased in concrete and therefore leakage from these sections could represent a significant threat to groundwater.

In addition to the release of contaminated water, the activities at drilling sites also produce polluting solid wastes such as drill cuttings, flocculated bentonites, and a variety of other solid additives. Other waste include used oils, cementing chemicals, and toxic organic compounds that contaminate the soil and water near drilling sites.

Air Pollution

Many of the chemicals used in hydraulic fracturing are easily converted into airborne toxins and pose a significant health risk to those living near well pads. Although many of the chemicals used in hydraulic fracturing are off the public record due to trade secret protection, there are documented health effects from proximity to drilling sites and exposure to these chemicals. According to the booklet produced by the Columbia University Urban Design Research Seminar, of these chemicals "94% result in eye and/or skin harm, 83% respiratory harm, 87% brain/neurological harm, and 93% gastrointestinal harm."

A major air pollutant that results from hydraulic fracturing operations is the production of ground-level ozone. Ozone is produced at well sites as a result of a chemical reaction catalyzed by sunlight between nitrates (NOX) and volatile organic compounds (VOC) released into the air at drill sites. According to the EPA, ground-level ozone is the main component of smog and can cause or aggravate a variety of health problems: breathing difficulties, aggravation of asthma, increased susceptibility to asthma and respiratory illnesses such as pneumonia and bronchitis, and permanent lung damage with frequent exposure. Ground-level ozone can also have significant environmental impacts by damaging the vegetation of trees and other plants, making them more susceptible to disease, insects, pollutants, competition, and weather. These effects have the potential to reduce crop yields and affect the productivity of forests.

Noise and Light Pollution

In addition to the polluting effects of contaminated water and release of volatile compounds into the air, activity at drilling sites can also have negative impact on the environment and human well-being in the form of noise and light pollution. The drilling machinery itself creates noise and light due to 24 hour operation and the constant traffic of trucks associated with construction, maintenance, delivery of water, etc. significantly contributes to noise and light pollution of the ambient environment. A study by Sullivan County, Texas on the City of Denton found that, for each primary extraction phase conducted at a well site (usually three), approximately 592 one-way truck trips were made per well by trucks weighing 80,000 to 100,000 pounds. The report found that there was greatly increased truck traffic in Denton associated with the industry. The increased level of traffic can have a negative impact on the structural integrity of roads and the lifetime of pavement, leading to increased frequency of repair on municipal roads paid for by taxpayers, not the industry.

Since well pads can be located extremely close to peoples' homes (as close as a few hundred feet), the level of noise produced by drilling operations can negatively impact the daily lives of local residents as well as disturb the natural environment, such as by having a negative impact on the activities of animals in the area. As is the case with noise pollution, the 24 hour operation of drilling rigs results in the presence of industrial light sources in close proximity to residences and the disturbance of natural patterns in the local environment.


Columbia University Urban Design Research Seminar. "Hancock and the Marcellus Shale." p. 10.

CUUDRS. "Hancock and the Marcellus Shale." p. 10.

CUUDRS. "Hancock and the Marcellus Shale." p. 10.

CUUDRS. "Hancock and the Marcellus Shale." p. 10.

Rana, S. 2008. Society of Petroleum Engineers. "Facts and Data on Environmental Risks - Oil and Gas Drilling Operations." Available at

Rana, S. 2008. "Facts and Data on Environmental Risks - Oil and Gas Drilling Operations."

CUUDRS. "Hancock and the Marcellus Shale." p. 11.

Marcellus Shale booklet. p. 11.;see also; for an analysis looking at a smaller sampling of fracturing chemicals, see

"Ground-level Ozone." ( Last updated 8 March 2010. Accessed 28 April 2010.

"Ground-level Ozone." ( Last updated 8 March 2010. Accessed 28 April 2010.

"Ground-level Ozone." ( Last updated 8 March 2010. Accessed 28 April 2010.

CUUDRS. "Hancock and the Marcellus Shale." p. 11.

CUUDRS. "Hancock and the Marcellus Shale." p. 11.