Resurgence of Pump and Treat Solutions: Directed Groundwater Recirculation

Summary and Conclusions DGR is an effective technology to enhance aquifer flushing mechanisms to address complex contaminant distri-bution resulting from varying hydrau-lic conditions an aquifer experiences during decades-long propagation and development of large diffused plumes. The dynamic and adaptive implementa-tion of DGR allows for the CSM and system performance data to guide the process of system design, implementa-tion, and operation. As a summary, key steps and considerations for effective design and application of DGR include:• Use a quantitative model for the initial design to minimize flushing times between injection and extrac-tion wells and limit hydraulic dead zones. Test alternate flow rates to understand flow field changes asso-ciated with changes in flow for the selected well layout.• During system installation and start up, conduct hydraulic testing to confirm local hydraulic conductiv-ity, well performance, and contami-nant distribution.• Focus on system evaluation and adaptive optimization to achieve target flow rates, expected mass removal rates, and not just on the “capture zones.”• Emphasize extraction well location within the highest permeability zones that can most effectively access contaminant mass with the highest migration potential. In some cases contaminant mass recovery rates at these wells can temporarily increase in the short term as the well increasingly captures water from higher concentration zones. In particular, this response may be observed in fractured rock sites.• Evaluate system performance con-tinuously by tracking well-specific and total system contaminant mass removal rates against total volume