Hampton Roads Sanitation District (HRSD), a large wastewater authority in Southeast Virginia (USA), implemented a large-scale aquifer long-term replenishment (ALTR) project, the Sustainable Water Initiative for Tomorrow (SWIFT). The primary aim of the SWIFT Project is to raise the depleted regional potentiometric surface over space and time through deep well recharge to the Potomac Aquifer System (PAS), a deep, confined hydrostratigraphic unit with three distinct aquifer layers and eleven screens within the recharge well. Previous work has demonstrated the effectiveness of injectate as an intrinsic tracer to characterize flow behavior in the multi-screen well and transport in the PAS, but after the recharge front passes a monitoring well, injectate is no longer a useful tracer unless an artificial tracer is added. This unique study employs a forced gradient sodium bromide tracer test in the PAS during recharge operations to characterize flow distribution and evaluate chemical transport. A comparison of a Single-Zone and Two-Zone model, both accounting for variable influent concentration and transient flow over the course of the test, demonstrate the efficacy of a Two-Zone model within the PAS compared to a Single-Zone model. Results are contrasted to previously estimated flow distribution and suggest a dynamic flow distribution, which changes over time as a result of preferential clogging within the recharge well.
