Public Services and Procurement Canada
This sheet presents mostly the excavation part of the technology. Post-excavation treatment options are detailed in the respective sheets associated with a specific treatment type. Specific treatment options following excavation are listed in the secondary treatment section of this sheet.
Excavation and treatment involves contaminated soils being first excavated and then transported to authorized treatment and/or disposal facilities (on-site or off-site). Sometimes pre-treatment will be required for off-site disposal to meet disposal criteria.
After treatment, the soils can be disposed of or reused as backfill and/or cover material.
Soil excavation and treatment may include:
On-site storage may include fuels, lubricants and other site materials required for the operation of machinery and equipment for the implementation of the process.
Temporary piles of contaminated materials may be stored on site, awaiting characterization, on-site processing or off-site shipment. They are usually covered to limit water infiltration and dust emission. It may be necessary to install impermeable liners under the stored soil piles.
If water pumping is required during excavation, tanks may also be present on site, as well as a temporary treatment unit.
This technology generally involves the excavation of all contaminated soil. Thus, there is little or no residue.
Dust, from excavations, soil treatment areas or soil spread on the ground by equipment, may be emitted during the work.
Contaminated groundwater is either stored in tanks for transport and treatment off-site or treated on-site for discharge to the municipal sanitary sewer, local stormwater system, or infiltration areas.
There may be vapour emission from equipment exhaust or volatilization of contaminants from fresh excavation walls or temporary piles.
The concentration of contaminants present in the dissolved and free phases is relevant when excavating in the saturated zone in the presence of water to be managed by pumping.
All types of soil can be excavated. In the case of saturated zone soils (below the groundwater table), it is also possible to excavate them, but water management will have to be implemented.
The technology is applicable in northern environments, however, remote sites require greater mobilization, resulting in higher on-site supervision costs. In addition, equipment availability is limited and work windows are relatively short.
Truck transport of contaminated materials to off-site treatment sites, or truck transport of treated materials for off-site reuse, is often very costly or impossible in remote and northern areas. Transportation by rail or barge/ship may be feasible, but is not always economically viable.
Because of permafrost, only shallow soils are suitable for excavation.
Due to difficulties in obtaining timely test results, it may be necessary to conduct field screening, plan staged interventions and/or implement a risk management approach.
For on-site and ex situ treatment, extreme cold can affect, for example, biodegradation and volatilization. Treatment systems in northern environments require climate-appropriate design, including consideration of seasonal changes as well as long periods without human intervention, refuelling.
If all contaminated soils have been excavated, there will be little or no long-term considerations.
Poorly designed and poorly compacted fills (poor choice of materials, installed when frozen, uncompacted) can create long-term geotechnical stability or differential settlement problems..
No by-products or metabolites are generated by the excavation of the soils. Such products may be generated by the treatment technology subsequent to excavation.
Depending on the type of contaminants present in the soil, a multitude of secondary treatments can be used to decontaminate excavated soils. These technologies are called “ex situ treatments” and several of them have been discussed in the following technology sheets:
The following links provide application examples:
Excavation is an effective method for removing contaminated soils. The performance of this technology, however, depends on the subsequent treatment of the soil.
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 : March 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 25, 2022