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The Dolgarrog Disaster, 1925
The failed section of the Eigiau Dam
In 1925, the failure of two dams caused a flood that swamped the village of Dolgarrog in North Wales, killing 16 people. The disaster was started by the failure of the Eigiau Dam, a small gravity dam. The water released from the reservoir flooded downstream, and overtopped the Coedty Dam, an embankment dam. This dam failed, releasing the huge volume of water that flooded Dolgarrog.
Reservoirs Safety Legislation
The disaster at Dolgarrog led the British parliament to pass the Reservoirs (Safety Provisions) Act in 1930 that introduced laws on the safety of reservoirs. This has since been updated, and the current one is the Reservoirs Act, 1975.
This Act covers the safety of all reservoirs in the United Kingdom that can hold at least 25,000 cubic metres of water. Under the Act, there is a "Panel" (or group) of civil engineers who are responsible for checking the safety of these reservoirs and their dams. They are called "Panel Engineers", and they can only belong to the Panel if they are considered to be well qualified, and experienced, in reservoir safety matters. Every reservoir has to be inspected every 10 years, or more often, when it is necessary. Panel Engineers also get involved with the construction of new reservoirs and repairs and changes to existing ones.
The act makes reservoir owners legally responsible for the safety of their reservoirs. They are required to employ suitably qualified civil engineers to make regular checks on safety in between the Panel Engineers' inspections.
Checking Dam Safety
These are some of the safety checks that engineers do: