MARINE TAILINGS DISPOSAL SIMULATION

The disposal of mine tailings in deep water body requires comprehensiv e assessment of the potential environmental impacts, and estimates of the effective storage capacity of the bottom bathymetry for accommodat ing the anticipated volume of disposed tailings over the life of a min e. A mathematical simulation model was developed for this purpose to p redict the distribution and long-term deposition patterns of tailings in a fjord. The model describes the mechanics of the tailings slurry R ow along the bottom of the receiving water body and the settling of su spended particles, as well as the redistribution of the deposited sedi ments due to slumping of unstable slopes. Specific processes simulated in the model also include entrainment at the top of the density curre nt, entrainment associated with internal hydraulic jumps in areas of c hanging bottom slopes, hindered settling and coagulation of suspended particles, and sediment deposition and bathymetric changes resulting f rom the deposition of large quantities of tailings. Long-term tailings deposition patterns are predicted by analyzing the flow of the tailin gs slurry in a series of rime increments, from a few months to a year. The bathymetry is assumed to remain unchanged within each time increm ent, and the model first simulates the steady-state flow held for the tailings slurry along the bottom and the resulting deposition rates fo r several sizes of suspended particles. Then the estimated tailings de position sates are combined with slope stability considerations to pre dict the new bathymetry of the receiving water body. Data from several operating marine tailings disposal systems were reviewed to assess th e applicability of specific relationships used in the model. The model was calibrated using data from one of the mast extensively studied ma rine tailings disposal systems, the Island Copper mine in Rupert Inlet of Vancouver Island, British Columbia. Comparison of simulated tailin gs deposition patterns in Rupert Inlet with data from field observatio ns and measurements suggests that calibration of the model is satisfac tory and provides confidence in the capability of the model to predict deposition patterns and suspended sediment concentrations for propose d mines.