The aim of the reconnaissance campaigns and investigation phases is to detect the presence of any pollutant concentrations in the groundwater, in order to assess the environmental quality of the environment studied and to rule on any health risks.
As a general rule, the A210 service for groundwater investigations is carried out following the documentary study included in the INFOS service (site visit, historical, documentary and memorial studies, vulnerability study, etc.) of the various environmental diagnostics.
If the water table is located at a shallow depth, there are two cases to consider:
- Case 1: No significant source of pollution on or near the site;
- Case n°2: The presence of a significant source of pollution on or near the site and/or its declaration as anICPE.
Piezometers will preferably be installed so that they can be maintained once the project has been completed.
Case 1 - No significant source of pollution :
A single piezometer is installed in the center of the site, or presumably downstream, to obtain an initial indication of groundwater quality. If the water in this structure proves to be polluted, at least two other structures will be installed and levelled during a second operation, in order to determine the direction of groundwater flow at the site and the extent of the pollution plume.
In case n°2 - Presence of a significant source of pollution and/or site listed as an ICPE :
A minimum of three piezometers will be installed on site to check groundwater quality upstream and downstream of the site.
The piezometers will be levelled to determine the direction of groundwater flow.
Once the piezometers have been installed, a 72-hour waiting period is required before the groundwater can be sampled. Once this time has elapsed, a purge of 3 to 5 times the volume of water remaining in the piezometer is carried out to renew the entire water column.
Samples are then taken using either a single-use bailer or a pump, professionally packaged and sent to a COFRAC-certified laboratory or equivalent.
The A210 mission is based on the following texts:
- NF X31-620 standard, December 2021 (polluted sites and soils);
- The requirements of standard NF X10-999 dated August 2014 (construction, monitoring and abandonment of works);
- NF X31-614 standard, January 2024 (control drilling in polluted sites and soils);
- The requirements of standard NF X31-615, December 2017 (groundwater sampling);
Monitoring can also be set up to:
- Monitor groundwater quality at low and high water levels;
- Monitor groundwater flow during low and high water periods.
