3. The Shannon Scheme

Shannon Scheme
Sinéad Cahalan, Tipperary CoCo
View From Tailrace
With the kind permission of ESB Archives
Shannon Scheme
With the kind permission of ESB Archives
General Plan of the Scheme
With the kind permission of ESB Archives

In the 1920s Clonlara was at the epicentre of the largest civil engineering project in Ireland’s history. On 13th August 1925, the construction of the Shannon Hydro-Electric Scheme commenced at Ardnacrusha Co Clare. The scheme led to the establishment of the Electricity Supply Board (ESB) on 11th August 1927. The project cost IR£5.2 million, about 20% of the Government’s revenue budget in 1925.

A German firm, Siemens, undertook this huge project, employing over 5,000 people at its peak, 1,000 Germans and 4,000 Irish workers. A power station and turbine hall were built at Ardnacrusha. Water was diverted to it from the Shannon, via a dam and intake weir at Obrien’s
Bridge, and channelled to the power station down a new 13-kilometre head-race canal that was dug out by bucket excavators.

A two-kilometre tail-race canal was blasted through the rock to take the outflow back to the Shannon River. Two rivers were diverted, two navigation locks were built and four new bridges were constructed where the intake canal cut across roads.

The logistics were fascinating: a temporary power station was needed to power the various workshops and an electric crane. 100 kilometres of narrow- gauge railway was installed to navigate around the Scheme, with some 100 locomotives and 3,000 wagons to move the massive amounts of clay and rock which were excavated. Three large rock crushing plants were used to excavate the rock so it could be re-used as hard-core.

The Scheme was officially opened by President William T. Cosgrave on 22nd July 1929.


  1. ESB archives online 19/01/2020.
  2. High Tension (Life on the Shannon Scheme) Michael McCarthy

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