A critical spill is the spill that is an "imminent and substantial threat to public health or the environment" or was the result of a major failure of a utility's infrastructure.
Critical Spill Determination
When determining if a wastewater or reclaimed water spill is a critical spill, the operator should consider:
The location of the spill
The severity and volume of the spill
The size of the contaminated area
The risk to the general public
Spills that backup into residences or buildings and spills that affect businesses associated with a high level of public health risk such as food establishments, nursing homes or medical facilities should typically be considered to be critical spills. Spills that are the result of a major failure of a utility's infrastructure, such as the failure of a reclaimed water or sewer line or a problem with a lift station or treatment facility, should be considered to be critical spills. Assume that the spill is a critical spill if there is any doubt.