Which condition requires emergency action to prevent failure at an impoundment or refuse pile?

The condition that necessitates immediate emergency action to prevent failure at an impoundment or refuse pile is related to an accident. Accidents can involve unexpected events such as equipment failure, geological instability, or human errors that pose a significant risk of causing a hazardous situation. Effective response to an accident is critical in mitigating potential consequences like the breaching of an impoundment, leading to environmental damage or safety hazards for personnel.

In contrast, while blackdamp signifies a dangerous gas condition in underground environments, it is not directly linked to structural integrity issues of impoundments. Hazards are general risks that may exist but do not call for immediate action unless they escalate. Similarly, the term failure refers to the collapse or breach that has already occurred rather than a condition that requires proactive measures to avert an incident. Thus, addressing accidents promptly is essential to maintain safety and operational integrity in mining environments.