Monitored Natural Attenuation of Explosives in Groundwater: Cost and Performance

Monitored natural attenuation (MNA) is a remedial alternative for explosives-contaminated groundwater at sites where a decline in contaminant mass can be demonstrated to occur at a rate sufficient to ensure the protection of potential receptors MNA is not a "no-action" alternative, but requires careful characterization of the site hydrogeology and contaminant distribution, long-term monitoring of groundwater, and groundwater modeling to conceptualize the contaminant plume and to predict future migration and attenuation MNA in the context of the demonstration described herein does not include intervention to promote natural processes Demonstrating that MNA is a viable remedial alternative requires gathering a "weight of evidence" that natural processes are sufficient to protect receptors of concern within a reasonable time frame. Explosives are subject to several attenuation mechanisms that effectively reduce concentrations in natural systems. Some of these processes have been defined, while other are poorly understood. MNA relies upon quality site characterization data, carefully conducted long-term monitoring, and groundwater modeling for contaminant conceptualization and long-term predictions of contaminant fate.