Actively facilitated permeable reactive barrier for remediation of TCE from a low permeability aquifer: Field application

Proven in situ treatment and remediation approaches are limited for low-permeability aquifers materials, particularly because of limitations to the delivery of reactive chemicals or access to contaminated plumes. In this paper, we describe the development of a cutting-edge solution for the remediation of contaminated groundwater in a low-permeability and low water-bearing aquifer contaminated with the chlorinated hydrocarbon trichloroethylene (TCE). The remediation technique introduced coupling of large-diameter permeable reactive barrier wells (PRB wells) with: (1) extraction wells through in a highly impacted plume; and (2) re-injection wells at the fringe of the plume. A pump-and-treat system (PTS) was employed at the site in a separate plume to reduce the mass of TCE near the second source zone. This research focuses only on the large diameter PRB well system. Conceptual site model development, design considerations, implementation and performance evaluation demonstrated how each of these elements were applied in the field. Approaches for coupling technologies to increase technical and economic feasibility are presented. Extraction and reinjection wells of treated groundwater at the fringe of the plume promoted a positive hydraulic gradient, facilitated groundwater transport through the reactive media, and contained the plume. Detailed geospatial and statistical analysis with over 10 years' monitoring data showed that dissolved TCE plume delineation shrank, and still concentration continues to decline, and were projected to meet the demands of remediation compliance regulations in the next few years. The results of this study indicate that significant remediation was achieved despite the challenging hydraulic conditions of the aquifer. The developed the remediation technology and conclusions indicate the system's usefulness at other sites.