Confidential Mine

This confidential mine experienced failures in its lethality toxicity tests at discharge. These failures stemmed from elevated un-ionized ammonia levels and investigations pointed to blasting activities in the pit as the primary source. Further complicating the issue, factors such as precipitation, groundwater inflows, temperature, pH, and CO₂ degassing also influenced ammonia loading and its speciation into un-ionized ammonia. The unpredictable nature of un-ionized ammonia levels created a significant compliance risk under the Metal and Diamond Mine Effluent Regulations (MDMER), raising concerns about potential environmental and biological harm.

To address this, True Environmental developed a comprehensive ammonia risk assessment model to aid in risk assessment and water management. This model utilized a dynamic mass balance simulation in GoldSim, integrated with geochemical speciation modeling in PHREEQC, allowing for accurate predictions of ammonia levels. It incorporated key factors affecting ammonia loading and speciation, including explosive formulation and quantity, blasted materials inventory, precipitation, groundwater inflows, pH, temperature, and CO₂ degassing dynamics. True Environmental then calibrated and validated the model using historical monitoring data, generating forecasts for both total ammonia and un-ionized ammonia concentrations. Through scenario testing under various operational and environmental conditions, as well as stochastic analyses, the model provided valuable insights for managing blasting inventories, altering groundwater routing, and optimizing pH treatment to improve water quality on-site.