This abbreviated animation demonstrates a basic groundwater contamination scenario, highlighting the important role of an aquitard.
- An aquitard is a low-permeability geologic layer (e.g., clay) in limiting the vertical migration of contaminated groundwater. It illustrates how, in the absence of such a protective horizon, pumping from a municipal drinking water supply well can draw a groundwater pollution plume downward, allowing contaminants to enter the well’s screened interval and impact public water quality.
- The animation also shows how private wells can be affected by groundwater contamination, particularly in settings where protective geologic barriers are absent or compromised. However, it’s important to note that even when a deep drinking water well is pumping near a contamination source, not all deep groundwater will necessarily become contaminated. For example, a well drilled to a sufficient depth and located within a more isolated hydrogeologic zone may remain unaffected, even if installed close to a known contaminant source.
This is a simplified example, intended to help viewers understand general principles of groundwater flow, plume migration, and vertical hydraulic gradients. In real-world situations, determining the source of contamination detected in a drinking water well requires a comprehensive and site-specific forensic hydrogeologic analysis, which consists of integrating geologic conditions, groundwater hydraulics, contaminant chemistry, and site-use history.
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