Project 2: Incorporating Natural Attenuation Into Design and Management Strategies for Contaminated Sites

Principal Investigators: John Novak, and Mark Widdowson (Virginia Polytechnic Institute and State University)

Collaborators: Norfolk Southern Corporation and Waste Management, Inc.

Monitored natural attenuation (MNA) is recognized as a possible site remediation approach where it can be shown that the risk associated with this approach provides a satisfactory level of risk. One of the important uses of MNA is for sites where source removal must first occur and then the contaminated soil and/or groundwater are cleaned further to reduce the down-gradient risk. The coupling of source removal strategies with MNA is an approach that can only be addressed by modeling. In effect, this approach seeks to answer the question: How clean does the source area need to be in order to use natural attenuation? Once that question is answered, natural attenuation coupled with source removal can be compared to other remediation approaches. Simple screening models can be used to estimate the transport of contaminant mass from a source, but more sophisticated models (e.g., SEAM3D, developed at Virginia Tech) are often necessary once MNA is selected. Such models will need to be developed for practical, user-friendly application and guidance and then demonstrated at a variety of sites. We currently are assessing MNA as a remediation approach at one site and combined MNA and phytoremediation at another site with a goal of modeling the processes and rates of degradation occurring at these locations. One site is a chlorinated solvent site and the other a PAH (creosote) contaminated site. These will serve as the field locations for determining the rate of natural processes and to verify modeling results. Both sites are extensively instrumented with multilevel samplers and background data is available.