For groundwater quality monitoring, the first step is to drill wells to access groundwater at the test site, so as to build safe monitoring stations for all relevant personnel. This is a lengthy process. The following explains how to set up a groundwater quality monitoring test site and the key precautions involved.

Numerous factors need to be taken into account. It is advisable for relevant staff to formulate a unified implementation plan to ensure the safe and standard installation of Online Groundwater Quality Monitoring stations. The key points are summarized as follows:

1.Clarify the objectives of the groundwater quality monitoring test site

Staff must define monitoring objectives prior to on-site operations. While each monitoring station has customized requirements, the objectives generally fall into three established categories.

2.Implement strategic monitoring

Strategic monitoring involves collecting groundwater samples in the short term, mainly for detecting trace diffused pollutants. Monitoring stations shall be deployed at sensitive locations, and this monitoring mode can also be applied in combination with other methods.

3.Attach importance to defensive monitoring

Defensive monitoring is ideal for long-term monitoring stations. It is recommended to adopt this approach to conduct early warning monitoring against potential adverse impacts on groundwater regimes.

4.Conduct investigative monitoring to facilitate follow-up work

Investigative monitoring is applied to assess groundwater quality and characteristics in potential polluted areas or contaminant plumes. If monitoring objectives are likely to be adjusted, a clear set of objectives must be confirmed before any on-site construction and installation work commences.

5.Technical requirements for well drilling

Well drilling is carried out to extract groundwater and create qualified conditions for sampling and analysis at monitoring sites. The geological conditions of the site determine the applicable drilling technologies. Areas with high concentrations of volatile organic compounds pose potential safety risks during drilling.

6.Reaction zone

The reaction zone connects to the aquifer and consists of filter assemblies and well screens. These components play a vital role in groundwater monitoring, as they can filter out solid sediments that may interfere with test results.

7.Casing materials selection

Material selection is critical. Metal casings deliver superior structural strength, yet metals other than stainless steel are prone to corrosion. Although corrosion may not cause obvious problems in the short run, it will severely damage the monitoring stations in the long term. Therefore, casing materials must be selected with extreme caution.

8.Sealing treatment

After well drilling and casing installation are completed, effective sealing shall be performed at the monitoring points. Bentonite is the most commonly used sealing material. Upon completion of grouting and sealing, well caps are installed to finish the construction of the groundwater quality monitoring station.