Abstract:

The failure of the gold heap leach facility at the Eagle Mine on June 24, 2024 resulted in the release of approximately 4 million tonnes of ore, 2 million tonnes of which escaped containment. The ore, saturated with cyanide solution, was transported to downgradient areas where it subsequently came into contact with surface water. The site’s existing water treatment infrastructure, designed to remove total suspended solids (TSS) and dissolved metals from the open pit and waste rock areas, was inadequate for treating the cyanide-laden leach solution. As a result, surface water affected by the ore displacement, along with residual leachate draining from within the heap containment, required immediate management and treatment.

Given the high risk of exceeding the site’s available water storage capacity, the absence of preparedness for cyanide treatment, and the stringent effluent limits specified in the Water Use License to protect the surrounding pristine environment, the situation created a true environmental emergency. This paper outlines the emergency response strategy initiated in mid-September 2024, which focused on the rapid adaptation and expansion of the existing water treatment plant to mitigate the immediate environmental risks posed by the cyanide-contaminated water.

The paper discusses key challenges encountered during the implementation of emergency treatment measures, including the selection of an appropriate treatment approach, the rapid sourcing and installation of necessary equipment, and the demonstration of the plant's ability to meet effluent toxicity requirements. Additionally, the early onset of winter conditions added complexity to the operation, further exacerbating logistical and operational difficulties.

The lessons learned from this project offer valuable insights into the management of cyanide-laden water in emergency scenarios, emphasizing the need for improved preparedness, flexible treatment technologies, and robust contingency planning. The paper aims to contribute to the broader industry knowledge base by sharing critical experiences in responding to cyanide-related water treatment emergencies and provides recommendations for improving future risk management and response strategies in similar contexts.

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