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Site Characterization To Support Use Of Monitored Natural Attentuation For Remediation Of Inorganic Contaminants In Groundwater
Citation:
FORD, R. G., R. T. WILKIN, AND S. D. ACREE. Site Characterization To Support Use Of Monitored Natural Attentuation For Remediation Of Inorganic Contaminants In Groundwater. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-08/114, 2008.
Impact/Purpose:
To highlight at what stage of the process solid phase characterization techniques need to be implemented in the site characterization process and to describe two case studies where the results of such techniques were critical to evaluation of MNA as a potential component of groundwater cleanup.
Description:
Technical recommendations have recently been published by the U.S. Environmental Protection Agency to address site characterization needed to support selection of Monitored Natural Attenuation (MNA) for cleanup of inorganic contaminant plumes in groundwater. Immobilization onto aquifer solids provides the primary mechanism for natural attenuation of metals and long-lived radionuclides that are frequently encountered in contaminated groundwater. In order to reliably evaluate the capacity for and stability of contaminant immobilization within the aquifer, mechanistic characteristics of the partitioning process and identification of the subsurface components that influence the extent of the immobilization reaction need to be understood. This requires information on the abundance and chemical speciation of solid phase reactants and products that participate in the immobilization reaction. Discussion of a hypothetical groundwater plume is used to illustrate the types of solid phase characterization data acquired to address information needs under the tiered analysis approach for site characterization. Analysis of data requirements and analytical approaches used to acquire solid phase characterization data and to project contaminant mobility for two Superfund sites is then provided. For these two sites, MNA was evaluated as a potential component of the groundwater remedy, where arsenic or uranium was the primary inorganic contaminant of concern.