The Management Plan (MP) is a tool used to establish different clean-up scenarios. This tool is used in site remediation when it is possible to act both on the state of the environment and on future uses.
A Management Plan (MP) is therefore appropriate for :
- Rehabilitation of former industrial sites;
- Closure of Installations Classées pour la Protection de l'Environnement (ICPE) ;
- The site's environment, when an EMI approach demonstrates the need to implement management measures.
The aim is to study the various management measures that can be put in place to ensure compatibility between the state of the environment and the chosen uses. These include :
- Pollution control measures;
- Use restrictions;
- The choice of constructive measures.
Historical and documentary studies, environmental vulnerability studies and various field investigation campaigns provide us with in-depth knowledge of the state of the environment at a given site. These results determine the presence of concentrated or diffuse pollution .
The determination of the most favorable management measures from both a health and an environmental point of view must give priority to the following actions:
- Firstly, the elimination of pollution sources;
Concentrated pollution (or pollution source) corresponds to pollution whose pollutant concentrations can be treated by pollution control techniques. It corresponds to a finite volume of underground medium in which the concentrations of one or more substances are significantly higher than the concentrations of the same substances in the immediate vicinity of the pollution source.
When such pollution is encountered, risk management policy advocates first and foremost seeking ways of eliminating the pollution and its impacts.
In this case, predictive health risk analysis is used to validate the management measures identified in the cost-benefit balance.
- Secondly, the deactivation of transfer vectors.
In contrast, diffuse pollution is characterized by the presence of one or more substances whose concentrations are relatively uniform and impact large volumes and surfaces of one or more media.
When such pollution is encountered, the risk management policy proposes to compare site values with management values and to verify, by means of predictive health risk analysis, whether the concentrations revealed are the cause of unacceptable health risks. In the event of excess health risk, management measures will focus on eliminating transfer routes.
Prior to the various analyses of environmental and/or health and/or economic issues, rehabilitation objectives must be set. Thus, the study of management scenarios includes :
1 Determining cut-off points
This is a statistical approach used to spatially delimit sources of pollution and concentrated pollution.
- The first step is to determine the distribution of concentrations of a compound at a given site. The different breaks in slope highlight the different levels of pollution, i.e. make it possible to distinguish between so-called diffuse and concentrated pollution;
- The second step quantifies the mass of pollutant. This involves determining the pollutant concentration range at which the percentage of pollutant mass becomes greater than the percentage of soil volume. This step shows that treating a limited volume of soil enables the majority of the pollutant mass to be treated;
- The third stage involves the construction of iso-concentration curves. This stage takes into account the lateral and vertical extent of pollution.
2 Defining rehabilitation objectives
Once the cut-off points have been determined, we need to check that they are compatible with the targets to be protected (users, environment).
The cut-off point is derived from a statistical analysis of the distribution of pollution in soil volumes, whereas the rehabilitation threshold must take into account :
- Pollutant mobility;
- Pollution control techniques;
- Future use of the site;
- Environmental quality objectives;
- Health risks;
- Financial considerations.
Thus, the defined cut-off point corresponds to the rehabilitation objectives if and only if:
- There is no significant deterioration in groundwater quality due to the release of pollutants contained in the soil;
- Water quality is comparable upstream and downstream of the study site;
- Residual soil pollution is compatible with predictive residual risk analysis (RRA);
- Treatment of areas with the highest concentrations of pollutants in the soil is financially acceptable in terms of the cost-benefit balance.
In order to meet these objectives, the Management Plan is likely to include the following studies:
- An analysis of water resource issues (A300) ;
- An analysis of environmental resource issues (A310) ;
- A predictive residual risk analysis (A320) ;
- A cost-benefit analysis (A330).
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