On Wednesday 12th March Ian Hope, Chair of the British Dam Society, unveiled an evocative sculpture with annotated plaque to commemorate the 150th anniversary of the Dale Dyke disaster. This dam failure was the biggest disaster of its kind in our history and led to the tragic loss of at least 250 lives.

Memorial Plaque Picture 

In setting the scene Ian placed the early Victorian reservoir building programme into context with the rapid industrial expansion and dire public health needs of the day. Sheffield itself had suffered a number of well documented cholera outbreaks reinforcing the demand for safe drinking water and proper sanitation. The Dale Dyke reservoir was constructed by the Sheffield Waterworks Company following an 1853 Act of Parliament.  In stark contrast to today the Company was not regulated in this activity and was itself able to design, supervise construction and potentially operate the reservoir without independent oversight.

Immediately on completion of construction, the "300 yard long, 85 feet high" dam failed on first filling, exposing inherent weaknesses. The dam was unable to withstand the forces of the full reservoir which were further compounded by a storm event.

There is considerable conjecture as to the cause. As engineers our forensic instincts will remain frustrated! We do know that there were a number of signs we would attribute to degradation of the core by internal erosion - a "whirlpool upstream" and "cracking of the downstream face".  The dam failed during the night when appraisal under candle light would have been unlikely to shed light on the true failure mechanism.

The history of the disaster and post-event hearings brought vested interests and human behaviour into play. The scene was set for a tense and intriguing drama. Clearly Sheffield Waterworks Company was protective of its position and commendably did stand by its employees, principally the Chief Engineer, John Gunsen.  Arguably, had the coroner been less zealous with his corrosive, opinionated, directive approach perhaps the real causes would have been laid open for analysis.

Whilst there remains scant evidence as to the true cause of the failure, we are led to question whether the pressurised pipes through the body of the dam contributed to the failure. We do know that their presence would have created an inherent threat and later designs were to avoid this feature.

Certainly Hawksley, responsible for later dam construction, adopted a far more conservative approach to the construction of neighbouring structures. He undoubtedly had a greater insight as to the cause of failure, being responsible for the demolition of the remaining Dale Dyke dam structure and able to examine key features such as the integral pipework.  He steadfastedly protected the interests of his clients and did not publically admit that the Dale Dyke dam had any defects.These days beyond the internet more information can be found in Geoffrey Binnie's book "Early dam builders in Britain" and geotechnical analysis by the late Peter Vaughan. Dr Andy Hughes, BDS Vice Chair, is conducting a series of talks on the subject (please see BDS website meetings page for further information).  

As an industry we have learnt a great deal from this and other similar tragic events in Victorian times. Our confidence in the significantly increased safety of our dams today comes from the continued vigilance employed by owners and the supervision by properly trained and qualified engineers who form the membership of the British Dam Society. The Reservoirs Act 1975 provides further structured safeguards ensuring the independence of crucial engineering roles which are also detached from direct employment of the owner. Ian Hope Chair British Dam Society.

See how the unveiling of the memorial was reported by the South Yorkshire Times here

Watch Ian Hope (British Dam Society) & Newman Booth (Yorkshire Water) explain the background behind the memorial on YouTube here.