Mary deFlaun and Scott Drew (New Jersey) recently collaborated with several researchers from the U.S. Geological Survey on an article published in the online edition of the journal "Groundwater" on September 5, 2017.
The article is entitled "Bioremediation in Fractured Rock: 1. Modeling to Inform Design, Monitoring, and Expectations." Their co-authors were C.R. Tiedeman, A.M. Shapiro, P.A. Hsieh, T.E. Imbrigiotta, D.J. Goode, P.J. Lacombe, C.D. Johnson, J.H. Williams, G.P. Curtis.
The paper is the first of a paired set of papers from the same project site. The second paper is entitled "Mobilization of Chloroethene Compounds from the Rock Matrix." The papers detail studies undertaken in the Lockatong mudstone underlying a former Naval Air Warfare Center in West Trenton, New Jersey, where groundwater was contaminated with TCE.
Impact statements are, respectively, "Groundwater flow and solute transport modeling was critical in designing bioremediation in fractured sedimentary rock," and "Chloroethene mobilization from the rock matrix after bioremediation in a sedimentary rock is quantified using groundwater fluxes."
Groundwater is a publication of the National Ground Water Association (NGWA)., NGWA is a community of groundwater professionals working to advance groundwater knowledge and the success of its members through education and outreach; advocacy; cooperation and information exchange; and enhancement of professional practices. The organization's members use their scientific and technical leadership, knowledge, and resources to pursue innovation, model best practices, and improve the business climate for the groundwater industry.
Field characterization of a trichloroethene (TCE) source area in fractured mudstones produced a detailed understanding of the geology, contaminant distribution in fractures and the rock matrix, and hydraulic and transport properties. Groundwater flow and chemical transport modeling that synthesized the field characterization information proved critical for designing bioremediation of the source area. The planned bioremediation involved injecting emulsified vegetable oil and bacteria to enhance the naturally occurring biodegradation of TCE. The flow and transport modeling showed that injection will spread amendments widely over a zone of lower-permeability fractures, with long residence times expected because of small velocities after injection and sorption of emulsified vegetable oil onto solids. Amendments transported out of this zone will be diluted by groundwater flux from other areas, limiting bioremediation effectiveness downgradient. At nearby pumping wells, further dilution is expected to make bioremediation effects undetectable in the pumped water. The results emphasize that in fracture-dominated flow regimes, the extent of injected amendments cannot be conceptualized using simple homogeneous models of groundwater flow commonly adopted to design injections in unconsolidated porous media (e.g., radial diverging or dipole flow regimes). Instead, it is important to synthesize site characterization information using a groundwater flow model that includes discrete features representing high- and low-permeability fractures. This type of model accounts for the highly heterogeneous hydraulic conductivity and groundwater fluxes in fractured-rock aquifers, and facilitates designing injection strategies that target specific volumes of the aquifer and maximize the distribution of amendments over these volumes.
Learn more at: https://www.ncbi.nlm.nih.gov/pubmed/28873502.
Learn more about the second article at: https://www.ncbi.nlm.nih.gov/pubmed/28873499.
Learn more about Mary at: https://www.geosyntec.com/people/mary-deflaun
Learn more about Scott at: https://www.geosyntec.com/people/scott-drew