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DRAFT <br />r <br />4 MODEL CALIBRATION <br />4.1 Approach <br />The regional model was calibrated by adjusting the input parameters until the model <br />results in reasonable agreement with the calibration targets (Section 3.10). The first <br />step was to calibrate the regional model to steady-state conditions based on the initial <br />estimates of hydraulic parameters from the pilot dewatering test and well tests, and <br />closely matching the simulated hydraulic heads to the observed heads from monitoring <br />wells and piezometers. This was done by adjusting the distributed recharge rate and <br />boundary conditions. <br />Then the boundary conditions, hydraulic parameters, and head conditions from the <br />regional steady-state calibration were used as the initial head condition, initial hydraulic <br />parameter estimates, and boundary conditions for the calibration of the model to the <br />transient hydraulic response observed during the pilot dewatering pumping test. For the <br />transient model, the mesh was refined near the location of the pilot dewatering well <br />(C-04-16B) to better represent the observed response. A sub-region of the regional <br />model was used for the transient calibration in order to efficiently calibrate the model. <br />The transient calibration model domain is shown in Figure 4.1. The transient calibration <br />to the pilot test allowed for the refinement of hydraulic conductivity and storage <br />coefficients estimates for the bedrock units of the F/G sequence, and the units directly <br />overlying and underlying the F/G sequence. <br />The adjusted hydraulic parameters from the transient calibration were assigned back <br />into the regional model. The regional model was then recalibrated to steady-state <br />conditions by holding the hydraulic parameters constant and adjusting the distributed <br />recharge rates. <br />4.2 Steady-state calibration <br />Calibration of the regional model to steady-state conditions focused on matching <br />simulated water levels to observed water levels measured in piezometers and <br />monitoring wells completed in the FS, F/G, H, and I sequences. Wells and piezometers <br />monitoring area-wide groundwater levels were used (i.e., located from the central <br />portion of the mine footprint and north). Perched water levels were not simulated in the <br />model since they represent localized conditions and not the area-wide flow regime. <br />Recharge from perched zones to the area-wide regime was modeled as part of the <br />distributed recharge. Figure 4.2 shows the comparison between measured and <br />modeled heads. Figure 4.3 shows the calibrated steady-state head contours for the F/G <br />sequence (top of layer 9). <br />2572-R3 <br />17 <br />Water Management Consultants