Groundwater Pollution: A Stubborn Legacy To Overcome

Groundwater pollution is a serious issue that poses a threat to human health and the environment. Groundwater is a vital source of drinking water and irrigation, but it is susceptible to contamination by various man-made products and natural processes. Pollutants such as gasoline, oil, road salts, chemicals, and untreated waste can seep into groundwater, making it unsafe and unfit for human use. The cleanup of groundwater pollution is challenging due to the complex nature of groundwater systems and the persistence of certain pollutants, such as radioactive waste, which can remain in the environment for thousands of years. Additionally, the sources of groundwater pollution can be diverse and widespread, including abandoned waste sites, leaky storage tanks, and atmospheric contaminants, making it difficult to identify and address all the sources of pollution.

Why is Groundwater Pollution Hard to Clean Up?

Groundwater is part of the hydrologic cycle, meaning it can be contaminated by pollutants in other parts of the cycle, such as the atmosphere or bodies of surface water

Groundwater is an essential component of the hydrologic cycle, a continuous sequence of water transformations that occur as water circulates from the atmosphere to the Earth's surface and subsurface regions and back into the atmosphere. As part of this cycle, groundwater is vulnerable to contamination from pollutants in other parts of the cycle, such as the atmosphere and bodies of surface water.

The hydrologic cycle begins with water evaporating from the Earth's surface, forming clouds in the sky. This water vapour then condenses and returns to the Earth as precipitation, such as rain, snow, sleet, or hail. When precipitation falls, some of it becomes surface runoff, flowing into lakes and rivers. However, a significant portion of the precipitation seeps into the ground, replenishing groundwater supplies.

As precipitation infiltrates the soil, it can carry pollutants from the surface, such as pesticides, fertilizers, and road salts, into the groundwater. This process, known as recharge, occurs in areas called recharge areas. The contaminated groundwater then moves slowly underground through cracks and spaces between soil particles, eventually reaching a discharge area where it enters a lake or stream and becomes surface water again.

During its journey, groundwater can also be affected by atmospheric contaminants. Pollutants from the atmosphere, such as toxic chemicals and gases, can find their way into the groundwater, further compromising its quality. Additionally, human activities contribute to groundwater pollution through the improper disposal of hazardous waste, leaks from storage tanks, and the use of septic systems.

The contamination of groundwater is a significant concern as it serves as a crucial source of drinking water for over 50% of the United States population and is extensively used for irrigation. The presence of pollutants in groundwater can lead to serious health issues, including diseases like hepatitis and dysentery, as well as long-term effects such as certain types of cancer.

Landfills are supposed to have a protective bottom layer to prevent contaminants from entering groundwater. However, if this layer is cracked or non-existent, pollutants can leach into groundwater

Groundwater pollution is challenging to address due to the susceptibility of groundwater to various contaminants and the complex, interconnected nature of the hydrologic cycle. Contaminants from the land's surface, such as pesticides, fertilizers, road salts, toxic substances from mining sites, and waste from septic tanks, can find their way into groundwater supplies.

Landfills, as part of waste disposal systems, play a crucial role in preventing pollutants from reaching groundwater. Modern sanitary landfills are designed with a protective bottom layer, also known as a liner system, to achieve this. This liner system acts as a crucial barrier, preventing contaminants from reaching the underlying groundwater. It typically consists of multiple layers, including soil, a geotextile layer, a gravel-based leachate collection system, a plastic layer, and an impermeable clay layer. The geotextile layer allows water to pass through while trapping solid particles, and the leachate collection system captures precipitation and contaminated liquid (leachate) from the landfill, preventing it from reaching the groundwater.

However, despite these protective measures, landfill liners may still develop cracks or flaws over time, providing a pathway for pollutants to seep into the groundwater. This vulnerability underscores the importance of regular monitoring and maintenance of landfills, even after they have been closed. In the event of a leak, early detection systems, such as electrical monitoring systems with electrode grids, can help identify breaches in the liner and facilitate prompt remedial actions.

The presence of a protective bottom layer in landfills is essential to preventing groundwater pollution. When this layer is intact, it effectively blocks contaminants like car battery acid, paint, and household cleaners from reaching the water. However, if this layer is compromised, either through cracks or its absence, pollutants can leach into the groundwater, leading to serious environmental and health issues.

To mitigate this risk, landfill operators are responsible for ongoing monitoring and must implement corrective actions if contamination is detected. The installation of secondary containment systems, such as an additional leachate collection system below the primary clay layer, can provide an extra layer of protection. Additionally, modern landfills often incorporate methane collection systems and groundwater monitoring systems to detect and address potential issues before they impact the surrounding environment.

Over time, storage tanks can corrode and leak, allowing contaminants to escape into groundwater

Groundwater is a vital source of drinking water for almost half of all Americans. It is also a crucial source of water for irrigation. Unfortunately, it is susceptible to pollutants, including gasoline, oil, road salts, and chemicals. Underground storage tanks are a leading cause of groundwater pollution. These tanks, often made of steel, can corrode and develop leaks over time, allowing their contents to escape into the surrounding soil and groundwater. Even a tiny pinprick-sized hole in a tank can result in 400 gallons of fuel leaking into the ground annually, contaminating both soil and water.

The problem of leaking underground storage tanks is widespread, with an estimated 10 million buried tanks in the United States. Leaks can occur in the tanks themselves, in the pumps, or in the connecting pipes. The contaminants can then rapidly spread through the soil and into groundwater, lakes, or rivers. The cleanup of such leaks is challenging and costly. It requires extensive testing and immediate action to prevent further contamination and increasing remediation costs.

The consequences of groundwater pollution from leaking storage tanks can be severe. For example, in Canob Park, Rhode Island, residents unknowingly used contaminated water for years, leading to a prolonged battle with oil companies and concerns about potential health damage. Similarly, in Rockaway, New Jersey, Shell scientists discovered groundwater contamination from leaking underground storage tanks, with the contaminant MTBE proving particularly difficult to remediate.

The challenge of cleaning up groundwater pollution from corroded and leaking storage tanks is further exacerbated by the presence of hazardous waste sites across the United States. These sites, often abandoned and uncontrolled, can contain barrels of hazardous materials that, if leaked, can contaminate the soil and eventually reach the groundwater. The combination of leaking storage tanks and improper waste disposal at these sites poses a significant threat to groundwater quality and the health and safety of nearby communities.

To address this issue, the EPA has been regulating underground storage tanks since 1984, and over 500,000 leaks have been cleaned up. However, as of 2024, more than 57,000 known sites still require full cleanup, underscoring the magnitude of the problem. The average cost to remediate a single site is approximately $154,000, highlighting the financial burden associated with addressing this environmental challenge.

Pesticides and fertilisers can find their way into groundwater supplies

Groundwater is an important source of water for irrigation and drinking, with over 50% of the US population depending on it for drinking water. However, it is susceptible to various pollutants, including pesticides and fertilisers.

Pesticides are chemicals designed to kill pests, such as insects (insecticides), weeds (herbicides), and fungi (fungicides). They are commonly used in agriculture to protect crops from pests and diseases. However, they can contaminate groundwater in several ways. Firstly, through the seepage of contaminated surface water. When pesticides are applied to fields, they can be carried by runoff, especially after rainfall or irrigation, and end up in nearby bodies of water. This is particularly common in areas with high rainfall, as the risk of pesticides contaminating water increases with greater rainfall. Additionally, pesticides can reach groundwater through accidental spills and leaks, improper disposal, and injection waste material into wells.

The solubility and persistence of pesticides play a significant role in their ability to contaminate groundwater. Highly water-soluble pesticides that are relatively persistent and not readily absorbed by soil particles have the greatest potential for movement and contamination. The content of organic matter in the soil also influences how well it can absorb pesticides. Increasing the soil's organic content enhances its ability to hold water and dissolved pesticides, making them available to plants and subject to eventual degradation.

Furthermore, the depth of the groundwater is a critical factor. In areas where the groundwater is close to the soil surface, there is less soil to act as a buffer against contamination. Permeable geologic layers, such as gravel deposits, allow water and dissolved pesticides to percolate downward and reach the groundwater. On the other hand, less permeable layers, such as clay, inhibit the movement of water and pesticides.

Fertilisers, which are used to provide nutrients to plants, can also find their way into groundwater supplies. Excessive fertiliser application can result in nutrient runoff, which can contaminate nearby water bodies and eventually reach groundwater. Additionally, fertilisers can leach through the soil and impact groundwater quality.

The contamination of groundwater by pesticides and fertilisers poses significant environmental and human health risks. These chemicals can have toxic effects on humans, animals, aquatic organisms, and plants. While efforts are being made to protect source waters and treat polluted water, the cleanup of contaminated groundwater remains challenging due to its slow movement and the difficulty in determining the extent and duration of contamination.

Radioactive waste, which can persist in the environment for thousands of years, poses a significant challenge to groundwater cleanup efforts

Groundwater contamination occurs when human-made products such as gasoline, oil, road salts, and chemicals seep into the groundwater, making it unsafe and unfit for human use. Radioactive waste is a particularly challenging issue within the broader problem of groundwater pollution. Radioactive waste can persist in the environment for thousands of years and poses significant risks to both public health and the environment. The Department of Energy's (DOE) Office of Environmental Management (EM) is tasked with cleaning up and treating this hazardous waste, which includes millions of gallons of radioactive waste from nuclear weapons production and energy research.

One of the primary challenges in addressing radioactive groundwater contamination is the lack of a comprehensive cleanup strategy. EM has faced criticism for its approach to managing cleanup efforts, which primarily relies on individual sites to negotiate activities and set priorities. This has resulted in inconsistencies in cleanup methods and costs between sites treating similar waste. For instance, the Hanford and Savannah River sites' plans for treating radioactive tank waste differ significantly in cost, with Hanford's efforts estimated to be tens of billions of dollars more expensive.

The absence of a standardized strategy has also led to issues with accountability and transparency. EM manages most of its cleanup work as operations activities, which are subject to less stringent requirements than other environmental remediation projects. Consequently, independent oversight outside of EM is not mandatory, hindering DOE's ability to hold EM accountable for its performance. Furthermore, EM has been criticized for providing incomplete, inaccurate, or misleading information to Congress about its cleanup progress.

Another challenge is the sheer magnitude of the task at hand. There are over 20,000 known abandoned and uncontrolled hazardous waste sites in the United States, and this number continues to grow annually. The scope of the problem, coupled with the persistence of radioactive contaminants, demands sustained long-term efforts and resources. EM's cleanup responsibilities are extensive, encompassing not just groundwater but also contaminated soil, facilities, and liquid waste. The estimated liability for DOE's Office of Environmental Management grew by a staggering $241 billion from 2011 to 2018, underscoring the immense financial burden associated with radioactive waste cleanup.

Compounding the issue is the fact that EM has faced significant workforce management challenges. GAO reports have highlighted an aging workforce, with a high percentage of staff nearing retirement and difficulties in recruiting and retaining personnel. These issues have resulted in project failures, schedule delays, cost overruns, and workplace accidents. Additionally, communication breakdowns between EM and DOE's Shared Service Center have hampered EM's ability to effectively manage its workforce.

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