46 U.S.C. § 2303a

(a) The Secretary shall establish procedures to ensure that after a serious marine casualty occurs, alcohol testing of crew members or other individuals responsible for the operation or other safety-sensitive functions of the vessel or vessels involved in such casualty is conducted no later than 2 hours after the casualty occurs, unless such testing cannot be completed within that time due to safety concerns directly related to the casualty. (b) The procedures in subsection (a) shall require that if alcohol testing cannot be completed within 2 hours of the occurrence of the casualty, such testing shall be conducted as soon thereafter as the safety concerns in subsection (a) have been adequately addressed to permit such testing, except that such testing may not be required more than 8 hours after the casualty occurs.