Monitored Natural Attenuation of Inorganic Contaminants in Ground Water

This paper is intended to provide an overview of the U.S. Environmental Protection Agency’s (EPA) ongoing efforts to produce a guidance document on the use of Monitored Natural Attenuation (MNA) as a remedial approach for radionuclide and inorganic contaminants1 in ground water. The focus is to provide a tiered decision-making approach for determining whether monitored natural attenuation (MNA) is likely to be an effective remedial approach for these contaminants in ground water. This approach can be applied in accordance with the remedial investigation and feasibility study phases of a Superfund cleanup, under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). This approach can also be used during the equivalent phases of a Resource Conservation and Recovery Act (RCRA) Corrective Actions (facility investigation and corrective measures study, respectively). The agency policy for the use of MNA in Office of Solid Waste and Emergency Response (OSWER) cleanup programs is described in the April 21, 1999 OSWER Directive titled, “Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action and Underground Storage Tanks ” (Directive No.9200.4-17P. This is an ongoing effort and it should be noted that the final guidance will likely differ from this overview due to its ongoing development and the EPA peer review process. This guidance is intended to provide a reasoned technical approach for evaluating MNA remedies. A draft is expected in late ’04 and a final peer reviewed published report in 2005