Guidance on the Assessment and Monitoring of Natural Attenuation of Contaminants in Groundwater

Monitored natural attenuation (MNA) can be a sustainable risk management strategy for a wide range of groundwater contaminants, where environmental data are collected and assessed that demonstrate natural attenuation will protect receptors from pollution or harm. Natural attenuation refers to the combination of physical, chemical and biological processes that act, without human intervention, to reduce contaminant concentrations, flux or toxicity. The Environment Agency originally published technical guidance for MNA in 2000 in its R&D Publication 95. Since then, significant scientific advances have been made in understanding contaminant behaviour and reactive transport in the subsurface, alongside ongoing developments in site characterisation, monitoring and predictive modelling approaches and technologies, that are captured in this updated guidance.