Analysis of Release and Transport of Ammonia from the Atlas Tailings Pile and Its Fate in the Colorado River

The tailings pile at the Atlas site near Moab Utah releases ammonia and other pollutants to the Colorado River through the groundwater pathway. Current releases may exceed standards for the protection of fish and fish larvae in the river. This report addresses whether a tight clay cover on the pile would reduce releases of ammonia from the pile, and lead to concentrations in the river that comply with current standards. The tasks involved with evaluating the effectiveness of the remediation are listed below: Estimate the rates of ammonia being released from the site presently and during site operation. Also estimate the release rate of ammonia into the river from discharging groundwater, and the discharge rate of ammonia in the river itself. Account for possible mechanisms for ammonia release other than discharge to the river. Use the estimated ammonia fluxes to back-calculate the likely fluxes of water through the tailings pile, and the effectiveness of the low-permeability cap. Estimate the concentrations likely to occur in the river under present-day and remediated conditions in the future.