AMD Prediction Spreadsheet (ARIES/NetAcid)

The AMD Prediction Spreadsheet implements two complementary methodologies: ARIES (Acid Rock Drainage Index Estimation System) and NetAcid (a simplified net acid generation calculator). ARIES uses empirical correlations between mineralogy (e.g., pyrite content), geochemistry (e.g., total sulfur, carbonate content), and field-observed leachate chemistry to classify material acid-forming potential (AFM) or non-acid-forming (NAF) behavior. NetAcid applies stoichiometric acid-base accounting—calculating total acid potential (TAP) from sulfide oxidation and neutralization potential (NP) from carbonate dissolution—to derive net acid generation (NAG = TAP − NP) and net acid production (NAP) after correcting for organic carbon and reactive Fe phases. The spreadsheet incorporates user-defined parameters such as weathering rates, infiltration estimates, and kinetic assumptions to project AMD evolution over decadal timescales. It serves as a screening-level tool aligned with regulatory frameworks like the Canadian Mine Environment Neutral Drainage (MEND) protocols and ASTM E2823, enabling rapid comparative analysis of waste rock or tailings before deploying more computationally intensive models (e.g., PHREEQC or MINTEQ). Its transparency, accessibility, and auditability make it widely adopted by consultants, regulators, and mining companies for pre-feasibility AMD risk classification and closure planning.