An overview of the Shannon Scheme

On 13th August 1925, one of the most important under-takings for the economic and social life of Ireland began when the first sod was cut at Ardnacrusha, Co Clare, for the construction of the Shannon Hydro-Electric Scheme. The initial proposal for the Scheme was presented by the German firm Siemens to the Government of the Irish Free State on 1st September 1924.  It led to the establishment of the Electricity Supply Board (ESB) on 11th August 1927.

The Scheme was a mammoth undertaking for a country the size of Ireland, especially when the State was barely three years old. The project cost IR£5.2 million and an additional IR£600,000 was paid in compensation to landowners. This total represented about 20% of the Government’s revenue budget in 1925.

It was a huge undertaking, employing over 5,000 people at its peak. To avoid flooding Limerick city with discharge waters, the station was built upstream, at Ardnacrusha. Water was diverted to it from the main river, via a dam and intake weir at Parteen, and channelled to the power station down a new 13-kilometre head-race canal that was dug out by bucket excavators.

A dam, power station and turbine hall were built at Ardnacrusha. A  two-kilometre tail-race canal was blasted through the rock to take the outflow back to the river. Two rivers were diverted,  two navigation locks were built and four new bridges were constructed where the intake canal cut across roads. The chief engineer was Frank Rishworth, who had worked on Egypt’s Aswan Dam.

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 were 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 at Parteen by President of the Executive Council William T. Cosgrave on 22nd  July 1929. It was the first fully integrated (generation, transmission, distribution, marketing and sales) national electricity system in the world.

The influential London Financial Times was highly impressed with the result, commenting:

They have thrown on their shoulders the not easy task of breaking what is in reality an enormous inferiority complex and the Shannon Scheme is one – and probably the most vital – of their methods of doing it

Within 3 years the demand for electricity in Ireland had expanded so much that stage two was initiated. Instead of the planned three extra penstocks, only one was used but it used a new 30 MW Kaplan turbine with seven blades which produced high efficiency on the relatively small head and  increased the capacity of the station to 75 MW by 1933.
In 1937 the Poulaphouca Reservoir hydro plant on the Liffey was constructed adding another 35 MW.

The scale and importance of the Shannon Scheme made it an economic centrepiece for the development of the modern Irish State. It laid the ground work for rural electrification in the late 1940s, which transformed rural life and improved the quality of life in communities throughout the country and paved the way for economic, social and cultural change. It was one of the largest engineering projects of its day, and has served as a reference model for other major engineering projects worldwide. Among those also to take an interest in the scheme was Franklin D. Roosevelt who consulted ESB about the scheme and passed on relevant information to the designers of the Tennessee Valley Project.

In 1996 Ardnacrusha became the first power station in the world to achieve ISO 9002 – an award from the International Organisation for Standardization – for its management system. In July 2004, the station achieved the environmental award ISO 14001.

In 2002 the Shannon Scheme joined the ranks of one of the world’s major engineering achievements when it received two major heritage awards.  The “International Milestone” by the IEEE (Institute of Electrical and Electronic Engineers) and “International Landmark” award by ASCE (American Society of Civil Engineers). Previous winners of these awards include the invention of colour television (Milestone), Japanese Bullet train (Milestone) the first Space Shuttle (Milestone), the Golden Gate Bridge (Landmark) and the Eiffel Tower (Landmark).