This technical note covers soil stabilisation and solidification as chemical remediation solution.
What is stabilisation and solidification?
Soil stabilisation/solidification (S/S) can be used in contaminated soil remediation to immobilise or encapsulate harmful contaminants through the addition of a binder / additive to prevent them from leaching into the environment. The S/S treated soil forms a stable, impermeable mass, reducing the risk of contaminant migration and facilitating safe disposal or reuse of the treated soil.
How does the process work?
The selection of an S/S approach requires careful consideration of many factors, such as soil properties, contaminant species and concentrations, project requirements, environmental regulations, remedial targets and long-term performance expectations. Thorough site characterisation, laboratory testing, including treatability studies and engineering design are essential for selecting the most suitable S/S mix formulations , implementation methods and optimising the effectiveness and cost-efficiency of the approach. In addition, monitoring and quality control during implementation are crucial to ensure the desired outcomes are achieved.
Which contaminants are suitable for stabilisation and solidification?
S/S is suitable for many combinations of organic and in-organic contaminants including:
- Metals;
- Radionuclides;
- Petroleum hydrocarbons;
- Larger chlorinated organics;
- Biological materials;
- Non or semi-volatile organic compounds; and
- Inorganic compounds.
Is stabilisation/solidification safe?
The binders and reagents used in S/S are often materials that are commonly used in construction and other activities. When these materials are handled and used correctly, they pose little risk to those undertaking the treatment process or the wider environment. Appropriate risk assessments and method statement should be provided for the works, including an understanding of COSHH (Control of Substances Hazardous to Health Regulations).
A strategy for monitoring and mitigation of dusts and contaminants should be employed during any works and may include dampening down using water to ensure dust and contaminants are not released to the air during the treatment mixing process. If required, the impacted media can be mixed inside tanks, or the treatment area can be covered to minimise dust and vapours. Once treated the materials are laboratory tested to ensure the leachability of the contaminants has been reduced. This can include both batch and tank leaching tests. The strength and durability of the treated materials may also need to be tested, depending on the performance specifications required.
Why use S/S ?
Soil S/S can provide a relatively quick and effective way to prevent exposure and limit migration of contaminants and is a process that is used worldwide. Other benefits of S/S include:
- Relatively low cost because the binders and chemical reagents are widely available and inexpensive;
- Can be used on a large variety of contaminants present;
- Can be used to target both saturated and unsaturated impacts;
- Can be applied to different types of media;
- Treatment equipment is widely available and relatively simple to use.
Treating geotechnically unsuitable and contaminated soils using these methods for re-use on site can remove the need (and therefore the associated costs) for off-site disposal, in addition to reducing the requirement for the import of materials.
A case study example can be found as follows: Willenhall-case-study-.pdf (geostreamuk.com)
For further details, contact our in-house S/S expert Dr Chris Evans info@geostreamuk.com