Evaluation of the D-Area Expanded Operable Unit for Monitored Natural Attenuation of Inorganic Constituents of Concern: Interim Report

A comprehensive approach is being developed to evaluate SRS sites with inorganic constituents of concern (COCs) for potential implementation of monitored natural attenuation (MNA) as a remediation strategy. In order to invoke MNA, the operative, or controlling, attenuation mechanisms at a given site must be identified and demonstrated using a technically defensible approach and site-specific data. This report details ongoing research in the application of this approach at the D-Area expanded operable unit (DEXOU). Initial screening of the DEXOU described in this interim report indicates that natural attenuation of inorganic COCs (low pH, Cr, Ni, Se, and As) is occurring to a significant degree. This work is part of continuing efforts to characterize the natural attenuation processes, both abiotic and biotic, occurring at this location and likely occurring at other SRS sites with inorganic COCs