In 1992-93 working for Golder Associates, Inc., J. Karanjac prepared several versions of a two-layered mathematical model of the greater Galmoy mine area in the Republic of Ireland for ARCON International Resources. The flow modeling was done using the U.S.G.S. modular three-dimensional code, widely known as MODFLOW. The solute transport was simulated using a two-dimensional Aquifer Simulation Model, known as ASM by Kinzelbach and Rausch.
The model was developed for the following reasons: (1) to check aquifer parameters obtained from several pumping tests, (2) to validate these parameters by calibrating the model response to water levels observed during the 42-day pumping test, (3) to forecast the likely scale of dewatering requirements, (4) to quantify the spread of the cone of depression with space and time during the initial 5-year dewatering operation, (5) to quantify the rate of shrinking of the cone of depression after pumps are shut off, and (6) to simulate the solute transport after mine closure.
The ground water system of the greater Galmoy area was simulated as a two-layer system: (1) the upper layer composed of several meters of glacial granular material and several meters of broken rock, (2) the lower layer composed of rock aquifers belonging to several dolomite and limestone formations. Both layers are unconfined and may receive recharge from infiltrated rainfall.
One of the major conclusions of this model is that the total volume rate of ground water that should be evacuated from the mine is about 17,250 m3/day (200 l/s), in the first year of dewatering. The dewatering operations should be designed in such a way that as much as possible is pumped out by perimeter wells. The spreading of the cone of depression, as an indicator of the efficiency of dewatering and environmental impact, is sufficiently documented in the modeling report. To see one of drawdown maps created with Modflow and GWW click here. To see a typical cross section with cones of depression created by dewatering click here. To see a typical lithologic section through one of wells click here. To return to Home Page click here.
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