Contaminated soil requires remediation and treatment before a site can be decontaminated and properly disposed of polluted soil.
Causes of soil pollution can vary since heavy metals and other contaminants can infiltrate the soil in the environment in any number of ways. Soil pollution often occurs when hazardous substances are buried or have spilled into uncontaminated soil. This can occur when humans apply chemicals like the use of pesticides and fertilizers on agricultural lands or through accidental spills during industrial activity. Some contaminants are also naturally occurring, such as asbestos.
The basic approaches to cleaning contaminated soil include:
- Chemical oxidation
- Soil washing
- Thermal treatment
Soil containment is just as it sounds … containing the soil in one spot so that any contaminants do not spread. Containment is a strategy used when excavation and removal of the waste create additional hazards to public health, there are barriers to adequate treatment or unrealistic costs. Excavation of soil is often associated with increased costs because permits are likely required, and material handling can add more unanticipated costs to a project.
However, it’s important to note that if a project manager chooses site containment, additional concerns must be addressed, including periodic inspections for settlement, the monitoring of groundwater and surface water, and additional samples over time. If these precautions are taken, containment can often meet any long-term and short-term exposure prevention goals.
As part of this process, heavy-duty liners are typically placed under and around any contaminated soil to prevent the migration of contaminants into soil or groundwater. These liners must be periodically checked for damage as well.
A landfill cap then serves as a barrier layer that prevents toxic effects to nearby areas. A cap can be made of varying materials depending on how contaminated soil. For example, the cap could be constructed using a layering system of vegetated soil and the use of plants or asphalt concrete.
Bioremediation uses organic materials to initiate biological processes in the soil that eventually will remove contaminants. While this soil remediation process is natural and sustainable and is preferred as a way to avoid using chemicals, it can take several months to fully carry out. Nevertheless, it’s an effective method to meet your long-term cleanup goals.
Micro-organisms such as bacteria and fungi are used in this process because they use the contaminant as a food source. Bioremediation is often used when mitigating pollutants like halogenated organic solvents and compounds, as well as hydrocarbons, nitrogen compounds, some metals and non-chlorinated pesticides and herbicides.
This type of contamination remediation is also a great choice for companies that want to have little to no negative impact on the environment since it is a sustainable and environmentally-friendly choice.
During the chemical oxidation process, a compound is injected into the area of soil contamination. The primary responsibility of this reactive chemical oxidant is to destroy the contaminants.
This solution is sought after when soil contamination occurs at deep levels below a structure and can be used to treat a variety or organic contaminants like TPH (total petroleum hydrocarbons), BTEX (benzene, toluene, ethylbenzene and xylene) and PCBs (persistent organic pollutants).
Reactive chemical oxidants can also be added to groundwater, permeating through the soil. When rapid contamination control is warranted, such as during a leak, this chemical process is a great option for fast remediation.
Soil washing physically separates soil from its contaminants. During the washing approach, a solution comprised of cleaning fluid and water passes through a contaminated soil sample. Contaminants are more likely to bind to fine-grained soil and silt, and soil washing effectively removes these fine-grained pieces from the larger soil sample.
However, it is important to note that the contaminant is not destroyed. It’s moved to a new location. Therefore, a site should take care not to contaminate another area during cleanup actions. Any residual water may need to be treated as well. It’s also a good idea to test the soil after the soil washing process to ensure that the left-behind particles are contaminant-free.
The thermal treatment method moves contaminants in soil using heat. During this heating process, some contaminants are destroyed. Others move through soil toward another place, such as wells, where crews collect them and pipe them to the ground surface.
Also known as “in situ,” the heat is applied underground directly to the original area of contamination. This method is used when contaminates include solvents, petroleum and wood preservative creosote because they do not dissolve easily in groundwater.
There are a few different main methods in which this heat can be applied, including by delivering an electrical current underground, injecting steam underground that is pumped through wells drilled in the area contaminated and using heaters placed in underground steel pipes. The primary purpose of this heat is to make the area hot enough to vaporize the toxic chemicals.
Contaminated Soil Disposal Help
No matter which approach is chosen to clean contaminated soil, there may still be a need to dispose of toxic substances properly. As a facility owner or site manager, you are responsible for ensuring that your team on the ground and the surrounding community is safe.
Depending on the contaminant you are addressing, you may face another hurdle … the final disposal of any contaminated soil. For example, landfills will not accept certain types of soil unless testing shows that the contaminants fall below the maximum allowed levels. For some contaminants, these may be very small amounts.
Some landfills may set their own maximum allowed levels, and other times, only certain landfills may accept lead contamination in soil or other types of contaminants. You may even be faced with the prospect of having to transport your soil out of state in order to dispose of it properly.
Experienced hazardous waste disposal companies have developed connections with landfills throughout California and across the United States to ensure your soil disposal process goes smoothly and according to the law.
What A Disposal Company Should Offer
Make sure any disposal company you choose offers hazardous substance determination through sampling and profiling. Although you may be familiar with the contaminants you are removing and disposing of, you need to be aware of quantities since many landfills will only accept a certain amount of a specific chemical or contaminant.
If the amount of contaminants you have in your soil is low, you may not even need hazardous waste removal. A quality company can help you determine this so that you don’t pay for a service you do not need.
It’s also critical to ensure your disposal company develops a customized soil transportation plan, completes any regulatory paperwork and offers proof that your contaminated soil has been properly disposed of so you have proof for your records. The best disposal companies will also offer expert services as part of your emergency plan in case you experience hazardous materials incidents, and you need immediate action in extreme cases.
While you may have taken the steps to ensure any contaminated soil at your worksite has been cleaned, remediated or contained, it’s important to complete the process safely by ensuring any contaminated soil or hazardous materials are properly disposed of according to local agencies, state regulations and the Environmental Protection Agency (EPA). Site treatment is only the first step to securing a safe area.
Our article, 6 Tips For Contaminated Soil Disposal, further offers advice on the steps you should take to protect human health, the environment and your company.