The Star-Orion South Diamond Project is located in Saskatchewan, Canada within the Fort a La Corne kimberlite area in complex hydrogeological settings. Two kimberlite pipes penetrate a very transmissive deep regional groundwater system which will be excavated by two proposed pits. Large scale active pit dewatering is required for the project. The purpose of the study was to assess Feasibility Level dewatering requirements and to evaluate possible hydrogeological impacts to the shallow groundwater system and surface-water bodies in the vicinity of the project.
This paper presents the results of a multiyear hydrogeological study to define the large scale dewatering requirements for the Star-Orion South Diamond Project in Saskatchewan, Canada, and to characterize possible hydrogeological impacts to the shallow groundwater system and surface-water bodies in the vicinity of the project. Two kimberlite pipes penetrate a very transmissive deep regional groundwater system and the proposed pit excavations require implementation of an active dewatering system with a pumping rate up to 120,000 m3/d. To assess the hydrogeological needs of the project in support of the Feasibility Dewatering and Environmental Impact Studies the authors developed a numerical groundwater flow model, which was calibrated to water level and pumping test data from numerous hydrogeological wells, including a 20 day pumping test from a prototype dewatering well with a pumping rate of about a 5,450 m3/d. Model predictions include: passive inflow to the proposed pits, the number and locations of required dewatering wells, their respective pumping rates and residual passive inflow to the pits, installation schedule of the dewatering wells, power costs for the proposed dewatering system, propagation of drawdown during proposed dewatering, backfilling of one pit and pit lake infilling of another pit, and the impact of groundwater discharge to the Saskatchewan River and creeks (during both pit excavations and infilling of the pit lake).
