Barrier-controlled monitored natural attenuation

Three existing technologies (source containment, source reduction, and moni tored natural attenuation) are integrated in barrier-controlled monitored n atural attenuation (BCMNA)-a new approach for managing plumes of contaminat ed groundwater and remediating contaminated sites. The basic BCMNA concept uses a low-permeability, nonreactive barrier to release contaminants into a n aquifer at a rate that optimizes natural attenuation. A simplified, one-d imensional model of the process is developed, and a hypothetical example of BCMNA is presented for a site contaminated with benzene. The analytical so lution is used to demonstrate how contaminant concentrations can be control led at a downgradient point of environmental compliance by manipulating des ign variables. BCMNA provides a greater degree of process control and risk reduction than monitored natural attenuation alone. BCMNA also holds promis e for reducing remediation costs because (1) barriers can be constructed re latively inexpensively and (2) a cost-effective amount of source reduction can be applied inside the contained area with the BCMNA system remaining in place to safely complete the remediation process after source reduction is terminated. Further numerical modeling and a demonstration project are rec ommended to address important details and prove the concept.