Simulated results for modeled conditions indicate that dredging will have little to no effect on salinity variations in areas upstream of currently proposed dredging activities. The cross-sectional models developed in this study do not necessarily simulate actual projected conditions instead, the models were used to examine the potential effects of deepening the navigation channel on saltwater intrusion in the surficial aquifer system under a range of plausible hypothetical conditions. The cross-sectional models were designed to incorporate a range of hydrogeologic conceptualizations to estimate the effect of uncertainty in hydrogeologic properties. Simulations were performed with each of four cross-sectional, variable-density groundwater-flow models, developed using SEAWAT, to simulate hypothetical changes in salinity in the surficial aquifer system as a result of dredging. Johns River on salinity in the adjacent surficial aquifer system. A study was conducted to determine the potential effects of navigation channel deepening in the St. Johns River, saline water from the Atlantic Ocean travels upstream as a saltwater “wedge” along the bottom of the channel, where the limestone is most likely to be exposed by the proposed dredging. Because of density-driven hydrodynamics of the St. The limestone unit, which is in the lowermost part of the surficial aquifer system, supplies water to domestic wells in the Jacksonville area.

The dredging operation will remove about 10 feet of sediments from the surficial aquifer system, including limestone in some locations. Johns River navigation channel in Jacksonville, Florida, deepening it to depths between 50 and 54 feet below North American Vertical Datum of 1988. Army Corps of Engineers (USACE) has proposed dredging a 13-mile reach of the St.

Army corps st johns river dredge report