Willow Farm Defect Model Model Setup The Willow Farm defect model has been constructed as a 2-dimensional model oriented perpendicular to the main groundwater flow direction (north-east). The model is 1,800 m wide and has a 2.5 m x 2.5 m grid spacing. The model set-up is shown in Figure D3. The model simulates a pathway (plane) that connects the tunnel to the Mataura Stream under various permeability scenarios. Figure D3 SEEP/W Willow Farm Defect Model Setup Material Properties The model was setup as replicating a soil regolith layer overlying a rockmass. The regolith was assigned a permeability value of 1x10-6 m/s. The rockmass permeability was varied depending on whether it is simulating a fault (K=1.0x10-5 m/s), andesite rock (K= 2.5x10-8 m/s) or tuff (K=1.0x10-7 m/s). The regolith was assumed to have a Storativity of 0.15 and the rockmass to be 0.01. Boundary Conditions The model boundary conditions assigned are as follows: - LHS Constant head = 230 m RL - RHS Constant head = 200 m RL - Rainfall Recharge = 10% - Tunnel = Seepage review - Mataura Stream = Seepage review Model Results The model was primarily constructed to assess the potential short term effects the access tunnel decline might have on surface water flows and these are summarised in Table D3. Table D3 Ventilation Shaft Inflows Lithology Stream Loss (m3/d) Stream Loss (L/s) Weathered Tuff 56 0.64 Andesite Rock 15 0.17 Fracture Zones 34 0.39
RkJQdWJsaXNoZXIy MjE2NDg3