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Installation of Monitoring Wells

Monitoring wells will be installed in order to:

  • Assess groundwater quality upstream and downstream of the contaminated site.
  • Determine the leakage infiltration rate and migration pathways of the contaminants.
  • Collect relevant data for understanding the groundwater flow in the target area.
  • Control the evolution of the contamination plume.

For this reason, after investigation soil borings are drilled, they can be completed as monitoring wells. However, non-contaminating materials should be used to construct piezometers, in order to avoid cross-contamination of the groundwater which is monitored. Piezometers for water level measurement are usually equipped with short well screens or sections of a slotted PVC pipe at the end, with gravel pack filled in around the screen to approximately 0,5 m - 1 m above the screen. A bentonite seal will be poured on top of the gravel pack to seal the well and prevent vertical cross-contamination and finally grout will be placed above the bentonite seal to ground surface. In order to measure water levels, electronic water level sensor or oil/water interface meter are recommended.

After piezometer installation, but prior to groundwater sampling, the wells need to be developed. Technical specifications involve purging the wells with one-use bailers or a submersible pump. This has to be performed in order to remove stagnant water and to ensure that collected groundwater samples are representative.

Typically, the volume of water to be purged from a well is determined as 8-10 water column volumes or based on stabilization of parameters as temperature, pH, specific conductance, etc., while purging.

Prior, during and after development of wells, the static water level will be recorded and the following parameters will be measured and observed:

  • Groundwater presence and level
  • Water colour
  • Turbidity
  • Odour
  • pH
  • Temperature
  • Specific conductance
  • Presence of non-aqueous phase liquid (NAPL)


Data related to well installation activities should be recorded on a Well Installation Field Data Sheet, specifying the piezometer identification number, the measurement data, the piezometer depth and the location of the piezometer (x,y,z coordinates), determined by means of a GPS.

A hydrogeologist must supervise the installation of monitoring wells and correct security measures and procedures must be considered.