Soil contamination, caused by human activity, harms the environment and threatens human health. Soil remediation targets these harmful contaminants to create safer, cleaner soil. Thanks to improvements in soil cleanup technology, inhospitable land areas are becoming once again useful for human and animal life. It’s essential to understand how soil remediation works and how it can improve the environment.
Learn how your business can be more environmentally friendly through soil remediation.
What Is Soil Remediation?
Soil remediation is a specific type of environmental remediation, which deals with cleaning up hazardous materials from the environment. It’s the process of removing contaminants from the soil, restoring it to a clean and safe condition. Contaminants can include a wide range of harmful chemicals and materials, each of which threatens both the environment and human safety. Several different strategies are available for soil remediation. Depending on variable factors, the process can be either short-term or long-term.
Large toxic waste dump sites sparked public outcry in the 1970s when people learned of human health and safety dangers. In response, Congress created the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), known as Superfund. The act grants power to the Environmental Protection Agency (EPA) to:
- Clean up contaminated areas.
- Hold responsible parties accountable.
- Force responsible parties to perform cleanups or reimburse the government for EPA cleanups.
Why Is Soil Remediation Important?
Soil remediation is vital for many reasons. The contaminants found in soil are dangerous and harmful for plants, animals and humans. In addition, pollution renders land areas useless — soil remediation makes space usable again.
When pollution affects the soil, it is detrimental to plant and animal life. Plants feel the impact first. They rely on soil nutrients to survive, and their roots take up contaminants. Depending on the contaminants and how prevalent they are, they can be fatal for plant life. Contaminated soil also affects animals, since touching or interacting with polluted soil and eating contaminated plants can cause health issues. Soil contamination can destroy entire ecosystems because it often results in the loss of habitat for wildlife.
Soil contamination is also a public health concern. Eating a contaminated plant or animal can cause serious harm, as can touching the soil itself. Because animals could consume contaminated plants and wander on, it becomes difficult to know what animals are safe to eat. Those who work or live in proximity to contaminated soil face serious health risks.
Contamination can render large plots of land inhospitable and unusable. Soil remediation frees up land for investment, development or restoring natural habitats, which is another reason it’s so important.
Common Soil Contaminants Sources
Soil contamination is a broad term and can include various chemicals and materials from different sources. Some common sources of soil contamination include:
- Landfills: Landfills are a significant source of worldwide pollution, affecting soil, water and air quality. They often contain various contaminants, which can combine to form even more dangerous substances.
- Sewage: Raw sewage overflow, septic tanks and leaking sewer lines host microorganisms, nitrates and toxic materials. When sewage pollutes soil, it becomes a significant health hazard.
- Industrial plants and factories: Many different contaminants derive from industrial plants and factories, including leaked chemicals and manufacturing byproducts. Contaminants depend on the type and scope of the industrial plant.
- Mining: Mining affects soil in complicated ways. It disturbs untouched soil, resulting in large-scale erosion. The distressed, windblown soil can cause hazards of its own, and chemical spills and residue result in further pollution.
- Fuel stations: Leaked gasoline can pollute the soil surrounding a gas station. Gasoline in the soil is dangerous because it contains the toxic chemical benzene.
- Wastewater: Wastewater includes any water contaminated by human use, such as agricultural runoff or water used in industrial processes. Mismanaged wastewater will travel along irrigation routes, damaging soil in its path. Businesses can help prevent wastewater soil contamination by employing professional liquid waste management services.
- Pesticide treatments: Pesticides degrade soil quality, poisoning beneficial plants and organisms. They also drain off-site and contaminate water sources.
Common Soil Contaminant Types
From these sources arise specific soil pollutants. Each pollutant category poses a unique risk to the environment and human health. Cleaning efforts and strategies depend on the nature of the pollutants.
1. Polychlorinated Biphenyls (PCBs)
Polychlorinated biphenyls (PCBs) are manufactured chemicals including carbon, hydrogen and chlorine, also known as chlorinated hydrocarbons. PCBs’ properties, such as structure and consistency, vary depending on the amount and arrangement of chlorine atoms. Consistency varies from liquid to waxy, and color varies from light to black.
Until the Toxic Substances Control Act banned PCB manufacturing in 1979, they were produced for many applications, from heat transfer to pigmentation. Because they can last a long time without breaking down, they continue to affect the environment. PCBs can potentially cause cancer and damage the immune, reproductive, endocrine and nervous systems of exposed humans and animals. Soil remediation can help remove PCBs from the environment.
2. Volatile and Semi-Volatile Chemicals
Volatile organic compounds (VOCs) are also human-made. They’re produced during the manufacturing of many products, such as paints and refrigerants. They emit over time as gases from manufactured products, causing adverse health effects. They permeate natural environments — VOCs are common contaminants in soils.
3. Radioactive Materials
Radioactive atoms have unstable nuclei, which causes them to emit electromagnetic waves or streams of subatomic particles. Radioactive contamination reach soils in multiple ways, including:
- Nuclear weapons testing
- Overproduction of nuclear fuels
- Uranium mining
- Improper waste disposal
- Accidental leaks
While some radioactive materials occur naturally, an overabundance can degrade soil, making it unable to host plants. Radioactive contamination in soil renders areas unsafe, as these materials pose serious human health risks, depending on the length and severity of the exposure. High doses of radiation can cause Acute Radiation Syndrome, Cutaneous Radiation Injury and an increased risk of developing cancer long-term. Soil remediation can target these dangerous materials.
Heavy metals contamination is a major source of soil pollution, deriving from leaded gasoline, paint, fertilizer, sewage and many other sources. Some common metal contaminants include:
These metals sink into soils and often resist breaking down for a long time. They can cause human health risks by contaminating plants and water sources. Hazardous metals are another targeted soil pollutant through remediation efforts.
5. Organic Compounds
Human activities such as agriculture have led to unnaturally high quantities of organic compounds in soil. Examples of organic compounds include:
- Polychlorinated dibenzofurans
- Polycyclic aromatic hydrocarbons
- Microorganisms in biowaste
These organic compounds dilute throughout the world’s soil. They can be challenging to identify, measure and track, but remediation can help reduce their quantity.
Another type of soil pollution includes pathogens. Pathogens can kill plant life, affecting ecosystems. Human activities contribute to a higher density of soil-borne pathogens. Livestock waste contains bacteria and viruses, and wastewater used for irrigation can expose soil to further pathogens. When pathogens spread through agricultural practices, food can become contaminated. Pathogens are another contaminant that remediation targets.
How Long Does Soil Remediation Take?
Contaminated soil remediation is a complex, advanced process. It takes time to clean and repair affected soil. How long the process takes depends on certain variables.
- Contaminant concentration: The quantity of contaminants affects how long the soil remediation process takes. Higher pollutant densities are more challenging to address.
- Soil density: Another factor to consider is the soil’s density. Soil filled with rocks and debris will take longer to treat.
- Depth of the area: The amount of affected soil directly correlates to how long remediation will take.
Short-Term vs. Long-Term Soil Remediation Projects
Soil remediation projects can be short- or long-term, with short-term projects requiring less than a year. Short-term remediation involves separating contaminated and clean soils. A liner directs runoff liquid away from the clean soil area. With the liner removed, clean soil remains. Long-term projects are more intensive and last longer than a year. These projects necessitate long-lasting liquid containment solutions.
5 Soil Remediation Techniques
Several soil remediation methods are available, utilizing physical, chemical and biological techniques. The process can be either “in-situ” or “ex-situ.” In-situ means the process happens on-site, while ex-situ soil remediation involves excavation and off-site treatment within soil remediation plants. Here are some of the strategies used to clean contaminated soil.
1. Excavation and Removal
As an ex-situ treatment method, excavation and removal are one form of soil remediation. The first step is the removal of possible contamination sources, like chemical-filled drums and debris. Then, experts test the soil to identify what contaminants are present. They excavate any polluted soil using construction equipment, like backhoes, and pump away present water.
Professionals cover the excavated soil with tarps to ensure wind and rain don’t blow or wash it away. It’s either taken to a landfill or left covered on-site. The process is complete when test results reveal safe soil in the surrounding area.
Capping is another way to protect environments from soil contaminants. Capping involves placing a cover over contaminated materials — it does not destroy or remove the contaminants, but it does prevent them from spreading further. Capping stops moving water from carrying contaminants to water sources, and it prevents wind from blowing the pollutants off-site. It also stops leaking gas from volatile organic compounds.
Several different types of caps are available, and many experts choose to combine them. Concrete or asphalt slabs can double as parking lots or building foundations, while other coverings include clean soil and vegetation, with a drainage pipe between. A geomembrane helps prevent gas leakage and water drainage.
Another method is solidification, which binds the waste in a solid block. While this technique does not destroy the pollutants, it prevents them from leaking into the surrounding environment by trapping them in place. Common binding agents include:
- Fly ash
Some binding agents also produce a chemical stabilizing reaction. For example, a water and limestone powder mixture will affect any metal pollutants in the soil, rendering them unable to dissolve in water. Solidification and stabilization are possible either in-situ or ex-situ. On-site, augers drill holes into the ground for injecting and mixing the additives. Off-site, pug mills grind and mix excavated soil.
4. Thermal Treatment
In-situ thermal treatments use heat to move the contaminants within the soil. It’s one of the more advanced soil remediation technologies. In essence, the extreme heat levels vaporize the chemicals. Once gaseous, the chemicals travel through the soil and become easier to remove, allowing for soil vapor extraction. Three different methods are available to generate the heat:
- Electrical resistance heating: For this method, two metal rods stick underground within the polluted soil. Electrical currents travel between them, resulting in heat.
- Steam-enhanced extraction: Steam-enhanced extraction pumps hot steam through underground wells.
- Thermal conduction heating: The heat produced through conduction in underground steel pipes is enough to destroy some chemical pollutants.
As the name suggests, bioremediation uses microscopic life to eat away contaminants. Microbes will feed on petroleum products, certain solvents and pesticides. Then, they will digest the contaminants and produce trace amounts of carbon dioxide, water or ethane. Bioremediation depends on favorable conditions for these microbes. To support microbial life, one can add oxygen-producing chemicals or vegetable oil to the soil using a well. Bioremediation is a favorable option since it eliminates pollutants. However, it can take months or years.
Other Types of Environmental Remediation
Pollution affects the entire natural environment, not just the soil — contaminants that start in the soil often wind up in freshwater sources. Remediation is also necessary for sediment, surface water and groundwater.
The EPA’s Superfund also targets contaminated sediment. Methods for cleaning up pollutants in sediment are similar to those for cleaning up soil. The EPA uses natural processes, capping, dredging or excavation techniques.
Surface Water Remediation
It’s imperative to keep surface waters clean, as human contact with surface water is likely. Thankfully, surface water is also easy to access. One technique for surface water remediation is air stripping, which involves transferring volatile organic compounds within liquid into an airstream.
Several methods are useful for groundwater remediation, as well. One strategy has earned the appropriate name “pump and treat,” which describes the process. Wells bring groundwater into above-ground treatment systems. Another technique is to use a permeable reactive barrier. These barriers are permeable because they allow some substances to escape while retaining contaminants.
Contact ERC for Contaminated Soil Remediation Services in the Mid-Atlantic
Soil remediation techniques make the environment cleaner and safer for plant, animal and human life. They remove or contain harmful contaminants such as PCBs, volatile chemicals, radioactive materials, metals, organic compounds and pathogens. Several different processes for soil remediation are available, with some being more effective than others and some being quicker than others.
If you’re wondering how or when to do soil remediation, consider contacting the Environmental Recovery Corporation (ERC). At ERC, we process and transport residual waste, ensuring compliance with all regulations. We offer comprehensive soil remediation services and we can help you pursue environmental sustainability through soil remediation. Contact us at ERC to learn more.