Groundwater Pollution: Understanding The Contamination Risks

Groundwater pollution, also known as groundwater contamination, occurs when pollutants are released into the ground and make their way into groundwater. This can be caused by both natural and human-induced factors, with the latter constituting the majority of cases. Natural causes include the presence of arsenic or fluoride in the groundwater, while human activities such as industrial processes, agricultural practices, and improper waste disposal are major contributors. The consequences of groundwater pollution are severe, posing risks to human health and the environment.

Poorly constructed wells

Wells are typically constructed by drilling a hole into an aquifer and inserting a pipe, screen, and pump to extract water. During construction, a steel or plastic casing is installed to prevent the collapse of the borehole. The space between the casing and the sides of the hole is filled with grout—such as cement, concrete, or bentonite clay—to seal off the channel and prevent pollutants from reaching the water table.

However, in poorly constructed wells, the casing may be inadequate or improperly installed, allowing contaminants to seep into the well. This can occur if the well is not cased deep enough below the water level, or if the casing is not extended high enough above the surrounding land, causing surface water to run down the casing and carry contaminants into the well. Improperly sealed wells can also allow surface water to enter, carrying bacteria, pesticides, fertilisers, or oil products into the drinking water supply.

To prevent these issues, it is crucial to hire a competent, licensed well driller and pump installer. Well owners should also regularly inspect and maintain their wells, ensuring that the casing is secure and intact, and that the well cap is tightly secured. Additionally, it is important to follow state regulations and recommended minimum separation distances from potential sources of pollution to reduce the risk of groundwater contamination.

Improperly abandoned wells

The National Ground Water Association (NGWA) warns that household water well owners should address any improperly abandoned wells on their property as they can pose threats to people, animals, and drinking water sources. Old wells can be dangerous as people or animals may fall into them, but they can also provide a pathway for surface contamination to reach aquifers. It is estimated that there are millions of abandoned wells and drilled holes in the United States, and finding them can sometimes require detective work. Signs of an abandoned well include pipes sticking out of the ground, small buildings that may have been a well house, depressions in the ground, concrete vaults or pits, and out-of-use windmills. Old maps, property plans, and neighbours who have lived in the area for a long time can also provide clues.

Once an abandoned well is found, a qualified water well system professional should be contacted. The contractor will determine if the well needs to be plugged, and if so, will remove all materials such as pump parts, pipes, wire, and gravel from the bottom of the well. The borehole is then disinfected, and specialized grout is used to fill the well from the bottom up to prevent surface water contamination. The cost of plugging a well varies depending on factors such as the depth and width of the well.

In addition to the risks posed to drinking water, improperly abandoned wells can also cause sinkholes. When a well is not properly plugged, groundwater can seep into the borehole, dissolving salt minerals and creating underground voids. These voids can cause the ground above to collapse, creating dangerous sinkholes that can damage infrastructure and pose risks to people and animals.

Septic systems, sewers, and pipelines

Septic systems are used by around one in five American households, as well as many businesses, as a cheap method of sewage disposal where municipal sewers are unavailable. While not all systems are problematic, an unknown number are putting human health at risk. Septic waste can introduce pathogens and pollutants that cause vomiting and diarrhoea, such as norovirus or cryptosporidium. It can also increase the risk of diseases caused by long-term exposure, such as those linked to nitrates, which can cause brain damage in infants.

In areas with a high density of septic systems, studies have shown that fecal bacteria in streams and groundwater increases. This is due to the soil's treatment capacity being diminished by the volume of waste. Septic tanks also do not break down pharmaceutical compounds, which can be harmful to fish and other aquatic species.

In addition to septic systems, sewers, and pipelines, underground storage tanks can also leak and contaminate groundwater. Over 542,000 underground storage tanks are buried in the US, and these often contain hazardous substances.

Uncontrolled hazardous waste

Hazardous waste sites can include landfills, which are supposed to have a protective bottom layer to prevent contaminants from seeping into the groundwater. However, if this layer is cracked or non-existent, contaminants such as car battery acid, paint, and household cleaners can leak into the groundwater. Additionally, the transportation and disposal of waste can also lead to uncontrolled hazardous waste. Accidents and leaks during transport are common, and waste-carrying trucks often release solid and hazardous waste.

Furthermore, the use of pesticides and fertilizers in agriculture can also contribute to uncontrolled hazardous waste. While they are necessary for farming, these chemicals can make their way into groundwater systems through runoff. Some pesticides have been linked to an increased risk of cancer and reproductive problems and can cause eye, liver, and kidney damage.

Another source of uncontrolled hazardous waste is industrial activities such as mining, metallurgy, and solid waste disposal. These activities can release toxic metals, including lead, cadmium, and chromium, which can eventually enter groundwater systems.

The presence of uncontrolled hazardous waste sites and the improper handling of hazardous materials highlight the importance of proper waste management and the need for stricter regulations to protect groundwater resources from pollution.

Atmospheric contaminants

Industrial emissions and acid rain are examples of atmospheric contaminants that can pollute groundwater. When power plants create acid rain, the chemicals can seep into the ground and contaminate water sources. Atmospheric contaminants can also include volatile organic compounds (VOCs) introduced through careless industrial practices. VOCs are often found in gasoline and can be harmful to human health.

Additionally, atmospheric deposition of pollutants can occur when airborne pollutants are deposited on land or water bodies and subsequently washed into the groundwater. Atmospheric deposition can come from both natural and anthropogenic sources, such as industrial emissions and vehicle exhaust. Atmospheric deposition can lead to the contamination of groundwater with toxic chemicals, heavy metals, and nutrients like nitrogen and sulfur.

Furthermore, atmospheric contaminants can also affect groundwater through acid rain and dry deposition. Acid rain forms when sulfur dioxide and nitrogen oxides are emitted into the atmosphere and combine with water vapour, forming sulfuric acid and nitric acid. These acidic compounds then fall to the ground as rain, fog, or dry particles, contaminating water sources, including groundwater.

The effects of atmospheric contaminants on groundwater quality can vary depending on the specific pollutants involved and the local geological and hydrological conditions. In some cases, atmospheric contaminants may be filtered or diluted as they percolate through the soil, reducing their impact on groundwater quality. However, in other cases, they may persist and accumulate in the groundwater, leading to long-term contamination.

To mitigate the impact of atmospheric contaminants on groundwater, it is essential to implement measures such as reducing industrial emissions, improving air quality, and implementing better wastewater treatment practices to prevent the release of harmful chemicals into the atmosphere.

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