Reclamation of Acid Mine Water Contamination of an
Alluvial Aquifer State of Arizona

Situation

A 28-mile long shoestring alluvial aquifer contains a 7-mile-long plume of metals and acid resulting from seepage from historical mining operations. The front of acidic groundwater was moving nearly 2 feet per day, threatening domestic users and surface water. Hydro Geo Chem was retained to develop an effective approach for halting the advance of the acid front and develop a comprehensive plan for aquifer remediation.

Hydro Geo Chem's Approach

We determined that the plume acidity was primarily dissolved iron and its advance was controlled by acid neutralization from carbonates in the alluvium. Based on these insights and reaction rate measurements, we developed a numerical model to simulate these processes and evaluate the effectiveness of various remedial scenarios. Hydro Geo Chem designed and executed a remedial investigation and designed an interim remedial system to stabilize the plume. We then completed a comprehensive human health and ecological risk assessment leading to a feasibility study which evaluated remedial alternatives. We also identified impacted private wells and supervised the installation of alternative water-supply wells.

View Simulation

 

Our interim remedial system produced rapid reductions in metal concentrations and prevented continuing degradation of surface water quality. This effectiveness defused regulatory concerns over the threat, which consequently allowed the client and us to develop long term and cost-effective remedial solutions. This confidence also translated into community acceptance that remedial measures would be protective of their health and safety.