Public Services and Procurement Canada
In situ solidification/stabilization is used to trap and limit the migration of contaminants in soils. This technology does not treat or eliminate contaminated materials, but it does reduce their potential impact on the environment.
The solidification/stabilization process consists of mixing contaminated soils, present at shallow or deep depths, with stabilizers and/or binding agents such as gypsum, lime, bentonite clay, Portland cement and various additives such as pozzolans, fly ash, sulfur and blast furnace slag. Polymers, organic materials (biosolids, manure and compost) and various minerals can also be used as admixtures.
Stabilization involves a transformation of the chemical properties of the contaminants present in the soil matrix by decreasing their solubility in water, their mobility and, therefore, their toxicity.
In addition, solidification involves a transformation of the physical properties of the treated matrix through the addition of binding agents that compact it, modify its pore size and reduce its hydraulic conductivity. The addition of binding agents can maximize the stabilization process.
There are two in situ solidification/stabilization technologies:
In situ solidification/stabilization technology can include:
In addition, if volatile components are present or if there is a potential for vapour emissions during stabilization/solidification operations, then a system for collecting and treating these emissions may be required.
In-situ soil stabilization/solidification may involve the use of specialized machinery or equipment that may require special installation conditions. On-site storage may include binding agents, admixtures and water required for the process, as well as fuels, lubricants and other site materials required for the operation of machinery or equipment for the process.
Stabilized contaminated soils are not usually considered waste, although they remain in place. However, there is a risk that liquid and vapour residues may be emitted from the system or during the solidification/stabilization process. Similarly, dust may be emitted during mixing operations. Water with added additives could also run off during the work.
A treatability test is recommended to determine the type and optimal amount of binder/stabilizer to add and to validate the stability of the products for several chemical and physical parameters. These tests also establish the geotechnical properties of the stabilized materials.
Solidification/stabilization technology is only applicable to solid contaminated matrices such as soils, sludges and sediments. Solidification/stabilization technology is used in the unsaturated zone to a depth of approximately 30 m. In addition, it is usually easier to implement in silty, sandy or gravelly soils, as opposed to soils with high clay content, since a uniform mixture is easier to achieve in this case. Soils containing clay tend to leave unmixed and destabilized residual clay lenses.
For Phenolic compounds, applies to pentachlorophenol (PCP) only.
Long-term monitoring of in situ solidification/stabilization performance is generally required to validate its continued effectiveness. Long-term performance monitoring may include groundwater quality monitoring to ensure that contaminants are not leaching from the stabilized soil areas. Long-term monitoring may also include an evaluation of the physical integrity of the stabilized zone and the maintenance of its geotechnical properties over time; the integrity of the stabilized soil zone may also be validated by long-term monitoring of vapour emissions.
There are no by-products generated during the implementation of the in situ solidification/stabilization technology. However, this technology does not treat the contaminants and they are still present on site following stabilization. They are retained within the matrix as long as the integrity of the matrix is maintained.
Soil screening may be required to separate the uncontaminated soil particle fractions and reduce the amount of material to be processed.
The following links provide application examples:
Unavailable for this fact sheet
Composed by : Martin Désilets, B.Sc., National Research Council
Updated by : Martin Désilets, B.Sc., National Research Council
Updated Date : April 1, 2008
Latest update provided by : Nathalie Arel ing., M.Sc., Frédéric Gagnon CPI., Sylvain Hains ing., M.Sc., Golder Associates Ltd.
Updated Date : March 2, 2022