Diagnosis of polluted sites - Drilling and extraction

Drilling and sampling, coupled with laboratory analysis, are the means used to detect the presence of pollutants in soil or groundwater at a given site. They are used to carry out what is commonly referred to as an "environmental diagnosis of the subsoil". A manufacturer may need to carry out such a diagnosis and use drilling and sampling techniques at various stages in the life of an industrial site.

• Prior to the construction of an industrial facility, it may be useful to assess the quality of the soil and groundwater at the site to ensure that there is no pollution.

• When there is a change of operator or owner, subsurface investigations are increasingly used to carry out an "inventory of fixtures" at the time of the transaction.

• Drilling and sampling are also required to carry out the risk assessments requested of certain manufacturers by the authorities as part of the national survey of potentially polluted industrial sites, initiated in 1993 by the French Ministry for Spatial Planning and the Environment.

• In the event of accidental pollution of the subsoil on a site, drilling and sampling must be carried out quickly to identify the pollution and treat it efficiently and cost-effectively before it spreads.

• An environmental diagnosis of the subsoil is generally required when a classified facility ceases operations, in order to assess the need for soil and groundwater remediation (article 34-1 of the decree of September 21, 1977 applicable to classified facilities).

• During soil or groundwater decontamination, samples are taken to monitor the effectiveness of the treatment and check that the decontamination objectives have been achieved.

  An environmental diagnosis of the subsoil requires the drilling of boreholes to make observations and measurements on the soil and groundwater, and to take samples whose chemical analysis will enable pollution levels to be quantified. The problem then arises: do the diagnostic conclusions reflect reality? The representativeness of a diagnosis depends largely on compliance with strict drilling and sampling procedures, and on the suitability of the techniques employed in relation to the pollutants sought and the geology of the site.

  In order to successfully diagnose the environmental impact of a site, it is therefore important to use drilling equipment adapted to the terrain, the depth of investigation and the pollutants being sought. Drilling techniques must also take into account the constraints associated...