Estimates of groundwater inflow were performed using Visual MODFLOW, a finite difference code for groundwater simulation based on the software originally developed by USGS. By using symmetry, only one quarter of the area needed to be simulated. A constant head boundary was located at a distance of 5000 feet from the shaft center-line. The shaft face was simulated with constant heads slightly above the elevation heads in order to avoid model instability from drainage and re-wetting of cells.

Transient analyses were run for a period of 60 days. The analyses assumed that the shaft was instantly constructed through the limestone at time zero. Inflows were determined at 2, 4, 10, 20, 40 and 60 days.