Hydrologic and geochemical evaluation of aquifer storage recovery in the Santee Limestone/Black Mingo Aquifer, Charleston, South Carolina, 1998-2002

Implications of Rate‐Limited Mass Transfer for Aquifer Storage and Recovery

“…Bulk electrical conductivity measures both mobile and immobile fluids in the aquifer. The discrepancy in storage period behavior between mobile and bulk measurements suggests that local‐scale solute exchange between the two porosity domains is responsible for the anomalous salinity rebound rather than advective upwelling of fluids from the confining units, as is proposed in earlier work (Petkewich et al 2004).…”

“…Sodium and sulfate concentrations of the recovered water demonstrate mixing of fresh water and native water. Some salinity rebound was observed in the BM/SL Aquifer during storage in these experiments and was attributed to upconing of salts from adjacent confining units (Petkewich et al 2004).…”

“…Aquifer storage and recovery (ASR), where excess surface or municipal water is injected into subsurface aquifers for later recovery, is one promising strategy for managing surplus water and overcoming water shortages (Pyne 1995). The recharged water may be stored for use during an emergency, to offset periods of water deficit, or to augment efforts to limit salt water intrusion in coastal areas (Brothers and Katzer 1990; Pyne 1995; Campbell et al 1997; Petkewich et al 2004). The ASR injection displaces the native aquifer fluid, creating a reservoir of potable or nearly potable water that can be used later (Eastwood and Stanfield 2001).…”

“…Although biological processes may be limited to the immediate vicinity of the wellbore, changes in water quality due to interaction with the rock matrix and native water can occur at great distances from the injection (Le Gal La Salle et al 2005). Mixing with native pore fluids is the primary mechanism by which injected water is degraded at the Charleston site (Petkewich et al 2004). In cases where only advection and dispersion processes are considered, mixing is confined to the edge of the injected fresh water bubble.…”

“…The 1993 to 1995 ASR tests were conducted at the “pilot study” site, west of the main Charleston peninsula, and the 1998 to 2002 “phase II” tests were done about 3 km to the east, on the main Charleston peninsula (Figure 1). The geology at both ASR sites is similar except for minor differences in formation depths: the sites consist of approximately 760 m of Upper Cretaceous through Quaternary age sedimentary rocks that are underlain by Precambrian and Paleozoic basalt (Petkewich et al 2004). The fractured‐rock aquifer targeted for ASR evaluation is the Black Mingo Group, a Tertiary‐age marginal marine and inner shelf deposit.…”