On Sept. 23, Hoover Dam’s hydroelectric mechanics (HEM) went to work placing the stop logs to kick off the FY2017 maintenance season. Stop logs are 9-ton water barricades that stop tail bay water from flowing into the draft tubes.

Once the stop logs are placed in their respective channels, eductors (also known as jet pumps or Venturi pumps) pump all of the water from the draft tubes. The water pressure from the river holds the stop logs in place.

This process of installing the stop logs allows workers to walk around inside the draft tube and the scroll cases, where they can perform inspections and conduct maintenance and repairs as needed.