English

Abstract

Spreadsheets can be used to provide an accurate and straightforward method of modeling the effects resulting from the disposal of treated and untreated mine wastewaters using percolation and land application disposal on surface and ground water quality. Spreadsheets are more user-friendly than many ground water modeling programs. Spreadsheet models are a valuable tool that can be used to evaluate the potential effects of a new mine, proposed revisions to a mine's operating permit throughout mine life, water disposal options in preparation for closing tailings impoundments, and for disposal of adit water. As mining progresses, adjustments may be made to the formulas and input values to reflect changes in water quality and quantity, hydrogeologic data, mine wastewater treatment efficiency, method or volume requiring disposal (water balance), and other changes that may occur in the composition of the mine wastewater streams. The spreadsheet models are constructed using basic data (e.g., hydrogeologic, wastewater quality and quantity, treatment, storage, and disposal system capacities, etc.), Darcy's equation, standard mixing zone calculations, and weighted-average equations. The calculations used are consistent with those of the National Pollutant Discharge Elimination System (NPDES) permitting for discharges to surface water and to ground waters that discharge to surface water. The use of spreadsheets is an innovative approach to identify water disposal requirements and the more critical elements of a water management system so that the most effective capital investment can be made during operations, and to identify operational mitigations that should be implemented to avoid costly issues during closure.