Aquifer coefficients determined from multiple well effects, Fernandina Beach, Florida

Abstract

On September 30, 1977, a large industrial plant in Fernandina Beach, Florida, shut down six artesian wells that had been pumping continuously for several weeks from the Floridan aquifer. Two wells continued pumping until November 20, 1977, at which time the shutdown wells were restarted. A water-level recorder on an observation well recorded the changing water level following shutdown and startup. Pumping rates of the wells ranged from 400,000 to 590,000 cubic feet per day (11,000 to 16,000 cubic meters per day). Distances from the pumped wells to the observation well range from 660 to 7,920 feet (200-2,420 meters). Analysis of the water-level data was further complicated because the wells were neither turned off nor restarted simultaneously; during recovery one well was restarted and pumped for several hours; and at the beginning of startup, a well that had been pumping continuously during the shutdown was turned off. The Cooper-Jacob graphical method, based on the principle of superposition and using values of specific drawdown or specific recovery (s/Q) and weighted logarithmic mean of the distance squared divided by time , was applied to determine the aquifer coefficients for the upper water-bearing zone of the aquifer. A transmissivity of 30,000 feet squared per day (2,800 meters squared per day) and a storage coefficient of between 2.5 × 10 -4 and 4.0 × 10 -4 were computed.