Security changes have been made at the Hoover Dam since 9/11. The dam is deemed one of America’s Seven Modern Civil Engineering Wonders by the American Society of Civil Engineers. $5.5 million per year is allocated to all security, including law enforcement. All visitors, or anyone doing business at the dam, are required to pass through magnetometers and X-ray screening. The traditional and hard-hat tours were discontinued, and more “top of dam” free tours with limited tour access into the dam itself.”]
Source: https://www.csoonline.com/article/2117776/securing-the-hoover-dam.html