Geochemistry of ground water-surface water interactions and metals loading rates in the North Fork of the American Fork River, Utah, from an abandoned silver/lead mine

The aqueous geochemistry and hydrology of the North Fork of the American Fork River, its tributaries, and the ground water near the Pacific Mine site were investigated. Ground water that flows directly through the mine tailings produces an acidic toxic metal contaminated ground water plume. Toxic metals loading rates suggest dissolved toxic metals enter the North Fork when it is a gaining stream. However, the total toxic metal load generally decreases through the study reach and is significantly greater than the dissolved load. Cadmium and Mn travel as dissolved species while Cu, Fe, Pb, and Zn travel as suspended solids in the surface waters, while As seems to be associated with both states. Based on PHREEQC geochemical modeling results, the most important reaction in these waters is the precipitation of hydrous ferric oxide and the sorption of Cu, Pb, most importantly Zn, and to a lesser degree As.