The risk posed by contamination to controlled waters such as rivers, lakes or groundwater within underlying aquifers is one of the fundamental concerns when investigating and assessing contaminated land.
Controlled waters risk not only depends on the concentrations of contaminants, but on the mobility of these contaminants in the environment, referred to as ‘environmental fate’.
This is controlled by the chemical characteristics of the contaminants, and by the ground conditions (geology, hydrogeology, hydrology) which underlie a site. It also depends on the engineering of the built environment.
All of these elements are considered when assessing controlled waters risk, culminating in a Conceptual Site Model, or should it prove necessary, numeric modelling of contaminant dispersion, dilution and degradation.
The result is a determination of contaminative risk, and a series of remediation criteria, which will inform the works required to mitigate the risk.
Due to the potential for contamination to affect controlled waters well beyond the boundary of a site, there may be a significant third party risk, both from a financial and legal liability perspective.
The Environment Agency are currently the primary regulator with regard to controlled waters risk.