3-15. USACE operates separately from state National Guard forces and federal Army forces. its capabilities are employed for DSCA through traditional Army command structure, USCs, public law, or DODDs. During natural disasters and other emergencies, USACE can respond under its own authority, Public Law 84-99 (PL 84-99); as a component of the Department of Defense; and as the designated lead agency in support of FEMA for Emergency Support Function Number 3, Public Works and Engineering (ESF #3.) USACE receives priorities from the joint field office directly. Federal military forces may also receive mission assignments under ESF Annex #3, but they remain under the federal joint task force's command.