Estimation of vertical hydraulic conductivity of the clay layer between the Eutaw and Gordo aquifers in the vicinity of Faunsdale, Marengo County, Alabama
The vertical hydraulic conductivity of the confining bed between the Eutaw and Gordo aquifers in the vicinity of Faunsdale, in northeast Marengo County, Alabama, is 1x10(-5) foot per day or less. Modeling vertical conductivities larger than 1x50(-5) foot per day produced drawdowns in the Eutaw aquifer greater than those observed in a test where 750 gallons per minute were pumped from the Gordo aquifer. Modeling has shown that vertical hydraulic conductivity of the confining bed is the controlling factor on the drawdown in the Eutaw aquifer. At equilibrium (steady-state) pumping 750 gallons per minute there was 3 feet of drawdown in the Eutaw aquifer with a confining bed conductivity of 1x10(-5) foot per day. When the conductivity was decreased to 1x10(-6) foot per day drawdown in the Eutaw aquifer was only 0.35 foot. A conductivity of 1x10(-5) foot per day in the 48-hour simulation reproduced the drawdown in the well from the 48-hour pumping test, but the conductivity may be as small as an untested 1x10(-6) foot per day. (USGS)