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Bulgarian Tailings Dam Failure.

January 17th, 2016 in News by admin

In the book Minewater Disasters we published in 2012 (International Water Association Publishing, London) a short entry regarding the 1966 mine tailings dam tragedy in Bulgaria. At the time and in our book a casualty total of 107 dead is quoted, since then more detail has come to light. Such a disaster at that time in a communist country under the influence of the Soviet State was somewhat flexible in its reporting of unfortunate news and what now appears to have been 500 + fatalities, a far higher death toll, being closer to the truth.

The reason for revisiting this story at this time is not the Brazilian tragedy at the iron ore tailings ponds collapse of last year but a request for any further detail on this Bulgarian event from the Senior Dam Safety Specialist at the Tennessee Valley Authority in Chattanooga. The TVA is compiling a data base of all dam failures and their courses and the lessons learnt from such events. The request was my sources and any documentary information that I had. Sadly much of my research carried out now 5 and 6 years ago is lost, buried in the old hard drive of a dead computer. I have though revisited the event again and have found it nearly as frustrating as it was the first time around though happily there are a few illustrations from the time that will make this piece acceptable to the general web browser!

The Plakalnitsa or Sgurigrad tailings impoundment failed a little after 11 AM on the 1st May 1966 was an event that could have coursed greater numbers of deaths had it taken place a few minutes earlier as the whole of the local population had been on parade in the square to celebrate the great communist festival of Labour Day. By the time the 3 metre wall of water entered and started sweeping through the streets many people had left the square and gone home to eat.

The flood emanating from the tailings dam of the Plakalnitsa copper mine inundated the mining village, destroying at least 150 homes and many community buildings including a hospital. The flood went on down the steep valley submerging the centre of Vratsa within minutes of the dam breach occurring. The site of the dam is not easily located today but from satellite photographs available on the internet including Google Maps there are at least two notable spill sites both close to each other that may indicate a pair of dam failures or one catastrophe. The area has been reforested in the last forty years and much of the landform is shielded by woodland canopy.
bulgarian

The buildings that were used as a hospital for the area, reportedly demolished in part by the flood.

towers

The twin towers that took the surface water away from the tailings pond collapsed shortly after the breach emptied the contents into the valley. The Photo is the opening still from Bulgarian TV News report on the run-up 60th anniversary of the disaster commemoration.

report

A ‘translation’ of the summary of the Plakalnitsa Dam failure taken from the internet and one is loath to gainsay it.

The Bulgarian news channel report showed the present site of the cross valley accident, nothing much survives of the actual dam structure that breached but several other sites in the locality still stand. The site appears to have had to cope with stream fed surface water passing around the dam emplacement, a bourne spring that was triggered by the unusual volume of precipitation over an extended period appears to have started discharging into the fill of the dam wall leading to the liquefaction of the fine particulate nature of the construction material which with the failure of the structure general led to the liquids fraction being greater than might have reasonably been expected.

In conclusion; the dam failure was not of anyone’s particular failure of duty. There were failures in surveying the site, failures in design and failures in running the tailings facility. Poor surface water controls which led to site instability and a standardised methodology of design that were of a similar nature for a 5 metre high or one that might be 20 metres above local ground level.

The biggest failure of all being the Bulgarian state’s handling of the repercussions, these included removal of those traumatised, the tracking down of film and photographs taken of the aftermath of the flood and their confiscation. Threats to families’ so that the true catastrophe might be more quickly forgotten.

Sixty years on may the victims be remembered and the story become fully known.

Author: admin

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