17th Feb 2022

Chalk Aquifer Disturbance and the Impact on Municipal Water Producers

Municipal water companies operate across a wide range of geographical and geological terrains; they may use surface water from reservoirs, lakes or rivers in areas of impermeable igneous or metamorphic rock, or underground sources (aquifers) in permeable rock formations.

In England and Wales about one third of our tap water comes from underground sources such as aquifers. Water from aquifers is generally referred to as groundwater, and it is typically extracted via boreholes.  

Groundwater is generally a good source for municipal water, because although it may have a high mineral content (depending on the rocks through which it has percolated) it is generally free of pathogenic bacteria, and it typically has little to no turbidity or discoloration. These attributes mean that it tends to need less treatment than does water from surface sources before entering the drinking water system.

However, aquifers are vulnerable to changes that may occur in the surrounding area. These may be natural e.g. seismic activity/tremors, or man-made such as tunnelling, roadworks, or building construction.   These types of events or activities disrupt the natural flow of water underground and may throw the borehole out of balance.

Of particular concern to municipal water companies is the risk that such events will trigger water contamination e.g., if the surrounding rock particles get into the water. This would mean that the unexpected contaminants must be removed from the water before it can progress to the municipal water treatment plant.

When a natural event is unexpected there may be little that can be done to prevent this happening, but where seismic activity is more frequent, or where man-made activities are anticipated, the prudent approach is to put protective measures in place in advance.

One such example is the potential impact of tunnelling associated with the construction of road or rail network infrastructure. 3 years ago, planned tunnelling through chalk areas in the south of England had the potential to disrupt important aquifers in that region, with the risk of increasing turbidity levels (due to increased amount of chalk in the extracted water) which would lead to customer complaints. This is not only aesthetically unpleasant but can also be a potential health risk.

The water company that was likely to be affected pre-emptively planned for this possibility by renting and installing an Amazon Filters filtration skid at the potentially impacted location.

The skid was commissioned and fully installed well ahead of time, with water running through the skid’s filtration system even before any disruption had occurred.   The water company ran tests in advance to satisfy themselves that the rig could reliably remove the amount of chalk that any disruption might cause.  

Amazon Filters skids can be purchased or booked for long term rental. We can also offer an immediate short-term solution for unanticipated disruption.Skid systems can be fitted with appropriate filters to address a range of issues e.g., increased iron, Manganese, Cryptosporidium or for general turbidity control.

Read more about our customised skids.


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