Tiedeman, C.R., A.M. Shapiro, P.A. Hsieh, T.E. Imbrigiotta, D.J. Goode, P.J. Lacombe, et al.
Groundwater 56(2):300-316(2018)

Field characterization of a 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 TCE biodegradation. Modeling showed that injection would 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 would be diluted by groundwater flux from other areas, limiting bioremediation effectiveness downgradient. Results emphasized 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.