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Identification and treatment of contaminated soils

48% of the surface area of the 6,013 cadastral plots presumed to be contaminated (covering 1,576 ha), which was subject to exploratory surveys of the soil condition between 2005 and 2014, was found to be contaminated, and 30% was treated.  Consequently, 472 hectares of land have been made available for use again (for housing, economic activities, etc.) following remediation work or risk-management measures.

Legal framework

The ordinance of 5 March 2009 on the management and remediation of contaminated soils (following an ordinance of 2004), known as the “soil ordinance”, specifies various events which trigger an obligation to survey soil for contamination and, where applicable, to usage restrictions and risk management or remediation obligations. The most important such events are:

  • the sale of land or buildings listed in the soil condition inventory (see the fact sheet on this subject);
  • the commencement, transfer or cessation of activities included in the list of “risk activities” that may cause soil contamination and are defined by a government decree (“soil obligations” imposed through the management of the environmental permit system);
  • the carrying out of works or the establishment of activities on land listed in the inventory that require excavation that may impede subsequent treatment or checking of any soil pollution or increase the exposure of people or the environment to any risks caused by soil contamination (“soil obligations” imposed through the management of the environmental permit system);
  • the accidental discovery of soil contamination during excavation;
  • the occurrence of an accident which causes soil contamination.

The soil ordinance introduced a procedure consisting of various technical phases carried out by a recognised soil contamination expert. The procedure makes it possible to determine whether soil is contaminated, to identify the extent and type of contamination and, where appropriate, to remediate the contamination or determine and if necessary manage the risks to public health and the environment.

  • Exploratory soil survey

If one of the “trigger events” occurs, as described above, an exploratory soil survey must be carried out by the person who initiated the event (e.g. the seller of a piece of land or property situated on it that is listed in the soil condition inventory). This survey makes it possible to ascertain whether or not the soil or groundwater is contaminated, and if so, to estimate the extent of the contamination (in particular whether the standards have been exceeded) and the nature of the contamination; it also determines whether or not a detailed survey needs to be performed. If possible, the exploratory soil survey also determines the type of contamination, “one-off contamination” (by a clearly identified, separately identifiable party), “mixed contamination” (caused by various parties, in proportions that cannot be separately identified in the case of at least one party) or “orphan contamination” (other cases). The exploratory soil survey also determines any safety measures to be taken.

  • Detailed survey

Given the limited number of soil core samples and analyses in an exploratory soil survey, in many cases the extent and type of contamination cannot be determined. It is then necessary to carry out a detailed survey. The detailed survey is a new phase that was introduced by the ordinance of 5 March 2009 on the management and remediation of contaminated soils. The aim of the survey is to define the vertical and horizontal limits of the soil contamination that was brought to light by the exploratory survey, to distinguish the increase and type of contamination, and to determine any safety measures that need to be taken.

  • Risk survey

In the case of mixed contamination or orphan contamination, a risk survey must be carried out to determine the risks that the soil contamination poses to public health and/or the environment. The risk assessment is based on the risk of exposure for humans (which depends on the designated and actual use of the land), the risk of damage to ecosystems, the risk of pollutants spreading to adjacent areas, underground water catchments, etc.

  • Risk management proposal

If the risk survey concludes that there is an unacceptable risk, a risk management proposal must be drawn up. The purpose of such a proposal is to determine the risk management measures to be taken to make the risks identified in the risk survey acceptable for public health and/or the environment in light of future or intended uses. The measures imposed by Brussels Environment include restrictions on use (e.g. the installation of hard surfacing, a ban on the creation of vegetable gardens or the use of groundwater, cellars, etc.), the curtailment of the contamination (e.g. with a concrete slab), or the removal of part of the contamination. Without the prior consent of Brussels Environment no changes may be made to the use of the site, no excavation work may be carried out and groundwater may not be pumped out.

  • Remediation proposal

In the case of one-off contamination, a remediation proposal must be drawn up to determine the type and method of remediation work to be carried out. Such work is carried out in order to meet the sanitation standards or prevent an increase in the level of contamination.
In the case of public fuel stations, the procedure for identifying and treating contaminated soil is subject to a specific legal framework consisting of the following phases: a prospective soil survey, a more detailed soil or risk survey, a remedial survey and remediation work.

Identification of contaminated soils: soil surveys

Since 2005, numerous exploratory soil surveys, detailed surveys, risk surveys, risk management proposals and remediation proposals have been carried out as a result of events triggering the obligations described above.
The following graph shows the change in the number of surveys carried out in the Brussels Region in the context of the application of the ordinances on contaminated soils and the fuel station decree.

Evolution of the total number of soil investigations and soil treatment projects (2005-2014)
Source: Brussels Environment, sous-div. Soils, 2015

Between 2005 and the end of 2014, 4,737 exploratory surveys of the soil - concerning 6,013 cadastral plots (1,576 ha) - were carried out. 1,854 of these surveys, equating to 2,186 contaminated plots, revealed the presence of contamination and resulted in detailed investigations (surveys). Of these 4,737 exploratory soil surveys, 618 led to the carrying out of remediation work or risk-management measures, and concerned a total of 827 cadastral plots, amounting to a total treated surface area of 472 ha (30% of the total area presumed to be contaminated).

The exploratory soil surveys focused on various ‘risk activities’, the most common being storage depots for flammable liquids, especially fuel oil tanks and fuel stations (accounting for 38% of such surveys), vehicle maintenance workshops (17%), spray booths (11%), printing works (6%), storage depots for waste oil (5%), storage depots for hazardous products (5%) and metal work (4%).

Proportion of contaminated plots subject to remediation work or risk-management measures in relation to the total number of surveyed plots, by economic sector (2005-2014)
Source : Brussels Environment, sous-div. Soils, 2015

The hazardous activities which produce soil contamination most often are metal degreasing (56% of the plots investigated had been metal degreasing sites), dry cleaning (55% of the plots investigated), the chemical treatment of metals (53% of the plots investigated), deposits of used vehicles or flammable liquids (52% of the plots investigated), and deposits of varnish and paints (50% of the plots investigated).  The hazardous activities are targeted in varying degrees by remediation work or risk-management measures. The plots which had been the subject of contamination treatment the most often were those which had been sites for deposits of varnish and paints (26% of the plots investigated), dry cleaning sites (25% of the plots investigated), sites for deposits of used oils (23% of the plots investigated), sites for deposits of flammable liquids (22% of the plots investigated), sites of manufacturing activity or metal degreasing, and sites for deposits of hazardous products (21% of the plots investigated).

In 80% of the contaminated sites investigated between 2010 and 2014, the contamination found was "orphan" contamination (see above). One-off and mixed pollution represented respectively 11 and 9% of the cases.

The most common pollutants are hydrocarbons and heavy metals and also, in industrial areas and groundwater areas, chlorinated solvents.

Treatment of contaminated soils

The graph below illustrates the change in the total area of cadastral parcels treated (through remediation or risk management) and redeployed in the Brussels Region.

Change in the cumulative area of treated cadastral plots and the cumulative cost of treatment (2005-2014)
Source: Brussels Environment, sous-div. Soils, 2015

For example, between 2005 and 2014, 472 hectares of land were made available for the establishment of economic activities, housing or recreational activities, at a total cost of approximately 348 million euros, which means 74€/m³.
The remediation work and the measures of risk management carried out more specifically related to the treatment of 1.2 million cubic metres of contaminated soil and 86 thousand cubic metres of contaminated water. The most commonly used technique is excavation (averaging 75% of the trated parcels), followed by the pumping and treating of groundwater (8%), stimulated bioremediation (5%) and soil air suction (4%).

Date de mise à jour: 14/05/2021