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Identification and treatment of contaminated soils

Of 3,294 cadastral parcels where an exploratory soil survey was carried out between 2005 and 2012, 39% were found to be contaminated and remediation or risk management proposals were put forward for 13% of these. As a result, 398 hectares of land were made available for new purposes (such as housing and economic activity) through remediation or risk management.

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 clean up 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 party) or “unattributed 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 unattributed 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. No changes may be made to the use of the site without the prior consent of Brussels Environment, 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.

Changes in the cumulative number of cadastral register plots subject to a procedure for the identification and treatment of contaminated soils (2005-2012)
Source: Brussels Environment, Soils Sub-Department, 2013


Changes in the cumulative number of cadastral register plots subject to a procedure for the identification and treatment of contaminated soils (2005-2012)

Between 2005 and the end of 2012, 3,294 cadastral plots underwent exploratory soil surveys. Of these, 1,535 plots (39%) were found to be contaminated, giving rise to detailed surveys that led to remediation or risk management proposals being put forward for 511 plots (13%).
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 (19%), spray booths (9%), printing works (5%), storage depots for waste oil, storage depots for hazardous products (5%) and metal production.

Proportion of contaminated plots subject to remediation work or risk management measures in relation to the total number of surveyed plots, by economic sector (2005-2012)
Source: Brussels Environment, Soils Sub-Department, 2013


Proportion of contaminated plots subject to remediation work or risk management measures in relation to the total number of surveyed plots, by economic sector (2005-2012)

The risk activities that most commonly give rise to soil contamination are the degreasing of metals (56% of the surveyed plots on which degreasing activities were performed), the chemical treatment of metals (53% of the surveyed plots), storage depots for scrapped vehicles (52% of the surveyed plots), storage depots for varnishes and paints (50% of the surveyed plots) and metal production (44% of the surveyed plots). The implementation of remediation or risk-management varies according to the risk activity. The plots most commonly treated for contamination are those where the following activities formerly took place: storage depots for varnishes and paints (26% of the surveyed plots), storage depots for waste oil (23% of the surveyed plots), and metal production and degreasing activities or storage depots for hazardous materials (21% of the surveyed plots).
79% of the contaminated plots studied in 2010 and 2012 involved unattributed contamination. One-off contamination and mixed contamination represent 10 and 11% of cases respectively.
The most common contaminants are hydrocarbons, heavy metals and, in industrial areas and in the groundwater, chlorinated solvents.

Treatment of contaminated soils

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

Change in the cumulative area of treated land and the cumulative cost of treatment (2005-2012)
Source: Brussels Environment, Soils Sub-Department, 2013


Change in the cumulative area of treated land and the cumulative cost of treatment (2005-2012)

For example, between 2005 and 2012, 398 hectares of land were made available for the establishment of economic activities, housing or recreational activities, at a total cost of approximately 276 million euros. The remediation work carried out more specifically related to the treatment (i.e. remediation and/or risk management) of 372 thousand tonnes of contaminated soil and 22 thousand cubic metres of contaminated water. The most commonly used technique is excavation (averaging 75% over the period 2005-2012), followed by the pumping and treating of groundwater (8%), stimulated bioremediation (5%) and soil air suction (4%).
 

 

Date de mise à jour: 23/01/2018