Complete the following phrase:  For many years, Black Eagle Dam's owners were required to hold simulations every five years to plan for various kinds of emergencies (flood, sabotage, mechanical breakdown, etc.) which might affect the dam and public safety. After the
September 11 attacks, these exercises were required to happen every year. PPL Montana works with local and state government and law enforcement, other companies, and the news media to plan for various contingencies and improve how it might respond in a disaster or emergency.