MODELING APPLICATION IN EVALUATING GROUNDWATER-SURFACE WATER INTERACTIONS DUE TO PHOSPHATE MINING ACTIVITIES
The proposed mine consists of an open pit that would be mined in three panels and includes various auxiliary mine facilities. Mining activities include construction of overburden piles and ore stockpiles, pit backfilling, construction of sediment retention structures, water management facilities and reclamation of impacted areas. Several surface water bodies occur within or near the project area, one of which is a Special Resource Water recognized as needing protection to maintain outstanding characteristics and current beneficial uses.
The objectives of the model application are to simulate the groundwater system and its interaction with surface water bodies and evaluate the potential impacts on surface and groundwater resources associated with the proposed mining activities. Specifically, the developed numerical model was used to (1) estimate groundwater inflow and dewatering requirements for the open pits, (2) predict potential changes in groundwater levels and quality during mining operations and after closure, (3) predict potential changes in stream flows and quality in the surface water related to mining activities during mining operations and after closure, (4) predict post-mining water levels in backfilled pits and impacted aquifers, and (5) estimate potential impacts to groundwater and surface water quality associated with leachate from mine facilities, including open pits, backfills, external waste dumps, and ore stockpiles. Furthermore, the numerical model may be used to establish operational monitoring and compliance points, evaluate mitigation strategies, and determine practical compliance levels for constituents of concern in groundwater and surface water.