(a) At the time of occurrence of a marine casualty, a discharge of oil into the navigable waters of the United States, a discharge of a hazardous substance into the navigable waters of the United States, or a release of a hazardous substance into the environment of the United States, the marine employer shall make a timely, good faith determination as to whether the occurrence currently is, or is likely to become, a serious marine incident.

(b) When a marine employer determines that a casualty or incident is, or is likely to become, a serious marine incident, the marine employer shall take all practicable steps to have each individual engaged or employed on board the vessel who is directly involved in the incident chemically tested for evidence of drug and alcohol use as required in this part.

(c) The marine employer determines which individuals are directly involved in a serious marine incident (SMI). A law enforcement officer may determine that additional individuals are directly involved in the SMI. In these cases, the marine employer must take all practical steps to have these additional individuals tested according to this part.

(d) The requirements of this subpart do not prevent personnel who are required to be tested from performing duties in the aftermath of an SMI when their performance is necessary to respond to safety concerns directly related to the incident.

(e) The marine employer shall ensure that all individuals engaged or employed on board a vessel are fully indoctrinated in the requirements of this subpart, and that appropriate vessel personnel are trained as necessary in the practical applications of these requirements.