The pressure relief valves are part of the original turbine equipment in the dam's power plant. When the water flow to the turbines must be stopped quickly, the pressure relief valves divert the water around the turbine and directly into the river.

This reduces the pressure rise that would otherwise occur in the penstock – the large pipes that carry the water from Lake Mead to the turbines.

Commissioner Estevan López said: "Ensuring the safety and reliability of Reclamation dams to protect the downstream public is a top priority for Reclamation.

"The new pressure relief valves will help to protect the life of the dam’s four penstocks.”

Beginning in October, construction crews monitored by Reclamation’s Lower Colorado Region will begin the process of disassembling the first of the three remaining pressure relief valves at Hoover Dam and refurbishing the units with new valves and related componentry – which will include installation of new valve head covers and hydraulic actuators.

Conversion and overhaul of the existing valves at Hoover Dam with installation of the new componentry is expected to be completed over the next three years when maintenance schedules allow.

The rehabilitation work, like all operations and maintenance work at Hoover Dam, is funded by the dam's power customers.