The origins of contamination

While many factors have contributed to the contamination of residential land in Quebec, the problem is mainly the result of extensive industrial development over the last century, the disposal of domestic and industrial wastes in unmonitored landfills, the use of oil tanks for home heating, and the lack of monitoring of storage tanks commonly found at former gas stations.

Main pollutants found in contaminated soils

Since there are many different sources of pollution, there is almost no limit to the number of toxic substances that can be found in polluted soil. Even so, it is possible to get a general picture of contaminated lands in Quebec¹:

Of the contaminated lands in Quebec:

  • 69% are contaminated by organic substances, such as petroleum products and hydrocarbons;
  • 11% are contaminated by inorganic substances such as heavy metals;
  • 20% are contaminated by both types of substances.

¹ Environnement_et_sante_publique – Fondements_et_pratiques, Michel Gérin, Pierre Gosselin, Sylvaine Cordier, Claude Viau, Philippe Quénel, Éric Dewailly, Edisem, Éditions Tec&Doc, 2003, 1,023 pages

What is contaminated land?

In Quebec, a site is contaminated if it contains contaminants with concentrations exceeding the limit values established in regulations.

There are currently three criteria:

Level A: Background values for inorganic parameters* and quantification limit** for organic parameters.
*Varies based on the geologic province.
**Minimum concentration that can be quantified using an analysis method with a definite accuracy.

Level B: Maximum acceptable limit for lands used for residential, recreational*, and institutional** purposes.
*Recreational usage includes a large number of possible cases with varying degrees of sensitivity, such as sports fields. Types of recreational usage that are less sensitive, such as bike paths, may fall under Level C.
** Institutional usage includes use by hospitals, schools, and daycares, for example.

Level C: Maximum acceptable limit for lands used for commercial or industrial purposes.

For more information, consult the Guide d’intervention – Protection des sols et réhabilitation des terrains contaminés (available in French only) –

Economic issues

The contamination of residential soils can lead to numerous problems, including the deterioration and loss of certain soil functions, or polluted surface water and groundwater. Contamination can potentially result in significant costs to owners:

  • Decontamination-related costs that fall under the owner’s responsibility
  • Full responsibility for the migration of contaminants outside of the property
  • Reductions in the property’s municipal value and market value
  • Recalling of the mortgage loan by the bank
  • Rejection of a refinancing application

Specific problems encountered on former landfills

If a residence has been built on a former landfill, the owner will not necessarily suffer legal damages. But to be sure, the owner, or future buyer, should complete three tests:

  • Soil characterization—Phase 2: to find out if it contains hydrocarbon contaminants or heavy metal contaminants (such as lead, mercury, or arsenic)
  • TestGeotechnical test: to determine the soil’s load-bearing capacity (meaning, whether the residual materials that have been deposited in the landfill, as well as the backfill, are able to sufficiently support the property constructed on it)
  • Air quality test: to verify if there are biogas, methane or other gases emanating from the site that could affect occupants’ health.

Migration problems

Rain, snow melt, geology, land slope, and soil pH can all affect the transfer of contaminants to other areas, making it particularly difficult to predict migration.

This is why IMMOPROOF analyzes not only the property itself, but also properties located within a 200-metre radius. To do so, data is queried in no fewer than seven different registries.

What are the types of environmental tests available on the market?

Every problem has its own test.

  • Georadar test: to find out if an old oil tank is buried underground (if there is not too much clay in the soil)
  • Exploratory test: to determine if there is a leaky tank (you must know the exact location of the tank)
  • Environmental assessment—Phase 1: to obtain a complete history of the environmental risks

If your property is located on top of or near a former landfill, three different analyses are necessary:

  • An air quality analysis, to find out if biogas is emanating into the property
  • A geotechnical study, to determine the soil’s load-bearing capacity
  • A characterization test—Phase 2, to find out if the soil contains contaminants exceeding the thresholds established in the regulations

Whatever you do, don’t try to “wing it” and do it yourself! Contact an environmental firm that will be able to recommend the right tests for your situation.

Decontamination (or rehabilitation)

There are many methods for rehabilitating contaminated soil.

In Quebec, the most common decontamination method used is excavation and burial of the contaminated soil in a location that is permitted under the law.

A future solution for Quebec is phytoremediation, or decontamination through living green plants. Phytoremediation mainly consists of growing certain types of plants that easily absorb soil pollutants into their tissues.

If my property is located on a former landfill, is it guaranteed that I'm going to have problems?

No. What we know about landfills is that three problems may arise: soil contamination, insufficient load-bearing capacity, and poor air quality inside the residence. In the best of cases, owners will not encounter any of these problems and, in the worst of cases, the owner will encounter all three.

In some cases, the problem will not manifest for several years. This is why we recommend transparently disclosing all information.

If my house is built on contaminated land, why isn’t it recorded on my title to property?

A contamination notice is only recorded on a title to property when stipulated for specific circumstances in the Environment Quality Act, which has been in effect since 2003. As a result, not all contaminated lands come with a contamination notice.