Natural Gas: Groundwater Pollution Risk?

Natural gas is a fossil fuel that is used for energy production. It is produced by drilling wells on land, which can disturb vegetation, soil, and wildlife habitats. The process of extracting natural gas can generate large volumes of contaminated water and air pollution. This contaminated water, if not properly handled, stored, and treated, can pollute land and water sources, including groundwater. Groundwater is found in porous, permeable rocks (aquifers) that lie close to the Earth's surface, and drilling for natural gas often involves drilling through these aquifers. This raises concerns about the potential for groundwater contamination. Improperly constructed or failing wells, natural or man-made fractures in the subsurface, and leaks or spills of drilling fluids or chemicals can all contribute to groundwater pollution. There have been documented cases of groundwater contamination with methane, hydraulic fracturing fluids, and other chemicals near oil and gas wells. The impact of natural gas drilling on groundwater pollution is a subject of ongoing research and regulatory efforts.

Natural gas leaks from wells

One of the primary sources of groundwater contamination is faulty or outdated well designs. Older gas wells, constructed as far back as the 1970s, often had shallow surface casings, leaving aquifers vulnerable to gas leaks. Improperly constructed or failing wells can allow natural gas to escape and contaminate groundwater. Additionally, natural or man-made fractures in the subsurface can provide a pathway for gas to migrate directly into groundwater supplies.

The presence of natural gas, particularly methane, in groundwater has severe consequences. Methane can turn drinking water flammable, posing a significant safety hazard. It can also accumulate in enclosed spaces, displacing oxygen and causing weakness, nausea, vomiting, and even fatal convulsions. Other toxic substances, such as arsenic, hydrogen sulfide, and benzene, can also leak from wells, further exacerbating the environmental and health risks.

The issue of natural gas leaks from wells is not limited to active wells alone. Abandoned and orphaned wells, numbering in the millions across the United States, continue to be a significant source of methane emissions and groundwater pollution. These wells, often improperly sealed or left unplugged, release methane and other toxic substances into the environment, impacting nearby communities and ecosystems.

Addressing natural gas leaks from wells requires strict government regulations, improved well-construction standards, and proper sealing and remediation of abandoned wells. The U.S. Environmental Protection Agency (EPA) has established guidelines to reduce methane emissions from the oil and gas industry, and states like Pennsylvania have initiated well-capping campaigns to address the issue.

Fracking and drilling fluids

Fracking, or hydraulic fracturing, involves pumping liquids under high pressure into a well to fracture the rock and allow natural gas to escape. This process requires large amounts of water, which can impact aquatic habitats and water availability for other uses. While fracking is a popular method for extracting oil and gas in the United States, it has also raised concerns about groundwater contamination.

Some studies and reports have suggested that fracking fluids and chemicals can migrate into groundwater supplies, leading to contamination. For example, a study by former EPA scientist Dominic DiGiulio found that fracking polluted groundwater in Wyoming, with residents reporting a bad taste and smell in their drinking water. Another study by Stanford University researcher DiGiulio suggested that fracking fluids may have migrated directly into the aquifer in Pavillion, Wyoming, through fractures. Similarly, a University of Colorado Boulder study found that groundwater in northeastern Colorado's Denver-Julesburg Basin was contaminated with natural gas, with 64% of water wells sampled containing dissolved methane.

However, other studies and organizations have concluded that fracking does not contaminate groundwater. For instance, studies by Duke University, the University of Cincinnati, the University of Texas-Austin, Syracuse University, and the Wyoming Department of Environmental Quality found no evidence of groundwater contamination due to fracking or natural gas drilling. Additionally, the U.S. Environmental Protection Agency (EPA) stated in 2015 that hydraulic fracturing activities had not led to widespread impacts on drinking water resources.

While the evidence on the impact of fracking on groundwater is mixed, it is important to note that construction methods, federal and state regulations, and industry standards aim to protect groundwater supplies during the process. For example, steel pipe casing and concrete are used to isolate the well bore from groundwater, and the horizontal section of the well is typically located below the groundwater layer. These measures help ensure safe and responsible energy development, as concluded by an Energy Department report.

Air pollution from drilling

Natural gas extraction and use have a range of environmental impacts, including air pollution. Drilling for natural gas can release natural gas into the atmosphere, and the engines and compressors used during the process also produce air pollutants. The US Environmental Protection Agency (EPA) estimates that in 2021, methane emissions from natural gas and petroleum systems, as well as abandoned oil and natural gas wells, accounted for about 33% of the total US emissions.

The oil and gas industry is a significant source of methane emissions, a potent greenhouse gas with a global warming potential more than 25 times that of carbon dioxide. It is also the largest industrial source of volatile organic compound (VOC) emissions, which contribute to the formation of ground-level ozone (smog). Exposure to ozone is associated with a range of adverse health effects, including aggravated asthma, increased hospital admissions, and premature death.

In addition to ozone, VOC emissions from the oil and gas industry include air toxics such as benzene, ethylbenzene, and n-hexane, which are known or suspected carcinogens. The construction and land disturbance required for drilling can also contribute to air pollution, as they can alter land use and harm local ecosystems by causing erosion and fragmenting wildlife habitats.

Furthermore, residents living near unconventional gas well sites are at an increased risk of health issues due to air pollution from natural gas development. The burning of natural gas for energy, while resulting in fewer emissions of most air pollutants compared to coal or petroleum, still releases carbon dioxide (CO2) and other pollutants.

To address these issues, the EPA has established guidelines for reducing methane and other harmful air pollutants in the oil and natural gas industry. These include strict government regulations and industry standards to ensure the safe transportation, storage, distribution, and consumption of natural gas.

Contaminated water from drilling

The production of natural gas can lead to contaminated water in several ways. Firstly, drilling activities can disturb vegetation, soil, and water resources. This includes clearing and levelling land around well sites and laying pipelines, which can impact local ecosystems and water sources. Drilling also requires large amounts of water, which can affect aquatic habitats and water availability for other uses.

Secondly, natural gas wells and pipelines often have engines that produce air pollutants and noise, impacting the surrounding environment and potentially contributing to water pollution. The process of extracting natural gas can also generate contaminated water as a byproduct, which, if not properly handled, stored, and treated, can pollute land and water sources. This water often contains high levels of salinity, chemical products, and residual hydrocarbons, posing risks to soil and groundwater quality.

Thirdly, hydraulic fracturing, or "fracking," involves pumping liquids under high pressure into wells to fracture rock and release natural gas. This process has been associated with groundwater contamination due to leaks and spills of fracturing fluid, which contains chemicals that can be toxic. In some cases, this fluid may migrate along abandoned wells, improperly sealed wells, induced fractures, or failed wastewater pit liners, leading to contaminated groundwater.

Furthermore, oil and gas wells have been found to leak natural gas, including methane, propane and butane, due to faulty or shallow surface casings. Older wells constructed in the 1970s, for example, may have inadequate casing depths, leaving aquifers vulnerable to potential gas leaks. Improperly constructed or failing wells can allow gas to escape into groundwater, as seen in documented cases in Ohio and Pennsylvania.

Lastly, the unauthorized use of toxic drilling fluid additives during drilling through freshwater aquifers can contaminate groundwater. The use of certain chemicals in the drilling process has raised concerns among residents and environmental groups, with some chemicals linked to health risks such as kidney, liver, heart, blood, and brain damage.

Radioactive materials in groundwater

Groundwater is often used for drinking water and bottled mineral water, and it is generally considered safe, clean, and economical. However, groundwater can become contaminated with hazardous chemicals and gases, including naturally occurring radioactive materials (NORMs) such as uranium, thorium, and radium. These NORMs are introduced through water-rock interactions during geological time periods and are present in groundwater environments worldwide, with concentrations depending on the local geologic settings.

In a study of bottled mineral water facilities, researchers found that diverse radionuclides, including uranium, radon, lead, and polonium, accumulated on the filters used in groundwater treatment processes. While the NORM concentrations in the treated water decreased compared to the incoming raw water, the measured surface radioactivity dose rate increased sharply on the early-stage filters. This elevated radiation may pose potential risks during the bottling, transport, and disposal processes, underscoring the importance of proper management and disposal of the filters.

The presence of NORMs in groundwater is not limited to specific locations but is influenced by the local geologic settings. For example, high concentrations of uranium are typically found in groundwater associated with granitic bedrock regions. Additionally, human activities, such as oil and gas development, can introduce further contamination. Improperly constructed or failing wells can allow natural gas, methane, and other gases to leak into groundwater, impacting both groundwater and surface water sources.

To address the issue of radioactive materials in groundwater, regulatory bodies like the Nuclear Safety and Security Commission in Korea have established guideline values for acceptable levels of radioactivity. These guidelines aim to ensure that treated water meets safety standards and mitigate potential risks associated with elevated radiation levels. It is crucial to continue researching and monitoring the presence of radioactive materials in groundwater to safeguard public health and the environment effectively.

Frequently asked questions