To mark the 60th anniversary of the Aberfan disaster, I have reposted my (now unavailable) blog posts from a decade ago describing the tragedy.
Tomorrow is the 60th anniversary of the terrible and tragic Aberfan landslide disaster in South Wales. Ten years ago I published a four part summary of what happened on that terrible day in 1966. Unfortunately, my old blog posts have disappeared, so here is a revisit of those posts (in a single post). Apologies, at this stage I have not been able to reinstate the images.
Post 1: Aberfan – A simple guide to what happened
[Tomorrow] will mark the [60th] anniversary of the Aberfan disaster in South Wales, Britain’s worst landslide disaster in which 116 children and 28 adults were killed. I will make a series of posts about the accident this week, but as a reference point I thought I would start by briefly reviewing the events of the day. Much of this is drawn primarily from the official investigation.
The village of Aberfan
Aberfan is a small Welsh village close to Merthyr Tydfil, in an area that was a powerhouse for coal mining. In 1966 the village was still dominated by mining, primarily in the adjacent Merthyr Vale colliery. The waste from this mine was tipped in a series of slag heaps on the slopes above the Aberfan. In the centre of the village, directly below one of the tips (Tip Number 7) was the Pant Glas Junior School.
On the day of the disaster, a crew arrived at Tip Number 7 to begin work at about 7:30 am. On arrival they noted that the tip had started to slide, with the track for their crane having deformed by about 3 metres. Unfortunately they did not have a telephone, so were unable to report the problems quickly (a worker was sent down to report the problem), but they resolved to move the crane back from the edge of the slide and to sever the overhanging rails. By 9 am the tip had subsided by another three metres. The report provides first hand testimony from the tipping crew of what happened next. These are the words of Gwyn Brown, the crane driver:
“I was standing on the edge of the depression. I was looking down into it, and what I saw I couldn’t believe my eyes. It was starting to come back up. It started to rise slowly at first. I still did not believe it, I thought I was seeing things. Then it rose up after pretty fast, at a tremendous speed. Then it sort of came up out of the depression and turned itself into a wave — that is the only way I can describe it — down towards the mountain . . . towards Aberfan village . . . into the mist.”
And these are the words of Leslie Davies, the charge-hand:
“When [Gywn Brown] shouted, we all got to the top of the tip and all I can tell you is it was going down at a hell of a speed in waves. I myself ran down the side of No. 3 tip all the way down towards No. 2 and No. 1 tip on the side. As I was running down, I heard another roar behind me and trees cracking and a tram passing me. I stopped — I fell down in fact. All I could see was waves of muck, slush and water. I still kept running . . . I kept going down shouting. I couldn’t see, nobody could. And I heard a voice answer me and he shouted, ‘Come out of there, for God’s sake’. That man was Trevor Steed . . . I went with Trevor Steed down on to the old railway line. By that time my mates had come down with me, behind me. We went along the line as far as we could towards the school, which we could see. All the houses were down. We could not pass that way because there was too much water rushing down . . . we could not go the way we wanted to go.”
The landslide involved about 105,000 cubic metres of spoil, which travelled at 17 to 34 km/h over a distance of about 500 metres. The landslide struck and engulfed 16 houses and Pant Glas Junior School. In total the Aberfan Disaster claimed 144 lives, and injured a further 35 people, most of them children.
The event was marked by haunting photography of the miners desperately digging through the waste in the destroyed school to try to save the children. However, the chances of surviving burial in this sort of landslide is low; the last survivor was recovered less than two hours after the accident.
In my next post I will describe the appalling actions by the National Coal Board. The Official Report is deeply critical of them, both in terms of their actions prior to the disaster and in terms of the way they approached the tribunal investigation the Aberfan disaster.
On the former point the report states:
While doubtless officials of the South Western Division, with their local knowledge and their awareness of slips which had actually occurred in the past, were more at fault, we cannot escape the conclusion that the Board must at national level also be blamed for its neglect of the stability of tips….Theirs was the overall responsibility for the initiation of policy, which involved that at national level there should have been due consideration of the proper methods to dispose of the waste of the coal-mining industry.
With regard to their approach to the tribunal:
On the other hand, if it really be the case that those with expert knowledge advising the National Coal Board had, even before the Inquiry began, come to the conclusion that the Board was to blame for the disaster — and that is precisely what Mr Piggott under cross-examination admitted…it is vastly to be regretted that the Board did not make this clear at the outset.
Post 2: Aberfan: the National Coal Board failures
The official Tribunal roundly criticised the National Coal Board for the part that they played in the disaster. Indeed, having denied responsibility through much the of the hearing, late in the day the counsel for the Board accepted the blame. As the Tribunal states in its report:
“But, as witness followed witness, the answer to the question — Should anyone be blamed for the disaster? — became crystal clear as far as concerned the National Coal Board. It was finally enunciated in this way on Day 74 during the closing speech of counsel for the Board: “Need it have happened? . . . There is a very short answer to that one. It need not have happened and should not have happened if proper site investigations had been carried out beforehand. The failure to have any site investigations beforehand must be attributed to lack of instructions from the Coal Board.”
Before the disaster (and indeed afterwards as well) there were multiple failures by the National Coal Board, but I will focus on two key aspects – the history of spoil heap flowslides in South Wales (which I will describe today) and the failure to understand the site conditions at Aberfan (which will be the subject of my next post).
Previous flowslides in coal spoil heaps
Perhaps the most unbelievable aspect of the Aberfan disaster is the failure of the National Coal Board to recognise that flowslides in spoil heaps represented a serious threat, despite multiple previous examples. The Tibunal report has almost 100 pages describing previous flowslide events, of which a number are very significant.
In 1939 a very serious landslide occurred in a spoil heap at the Albion Colliery near to Abercynon, about 8 km from Aberfan. The Tribunal report describes it thus:
At 1:40 p.m. on 5th December, 1939, after a period of heavy rainfall, a large slide of a tip belonging to the Albion Colliery (owned by the Powell Duffryn Company) occurred at Cilfynydd Common, near Abercynon, some five miles from Aberfan. The tip, situated on the hillside adjoining the main Cardiff-Merthyr road, slid some 710 feet [215 metres] to the road, crossed it, and then progressed a further 720 feet [220 metres] to beyond the river bed. The width of the slide below the tip was 400 feet [120 metres], the main road was blocked for 585 feet [180 m] to a depth of 20-25 feet [6-8 metres], the Glamorgan Canal was filled for 540 feet [165 metres] and the railway for 500 feet [150 metres]. The River Taff was blocked to a depth of 15 feet [5 metres] for some 500 feet [150 metres] and substantially diverted. It was estimated that the total weight of the tip material in the slide was some 180,000 tons [163,000 tonnes]. Having regard to the heavy volume of traffic normally passing along this road, it is remarkable that there were no fatalities.
In the aftermath of this landslide, which was clearly a lucky escape, a document was written about the risks of such failures:
Immediately following upon the Cilfynydd slide, in that same month of December, 1939, a Powell Duffryn engineer (thought to be a Mr. A. L. Davies) prepared an illustrated memorandum entitled “The Sliding of Colliery Rubbish Tips”. The Chief Engineer of the Rhymney Valley area of Powell Duffryn handed a copy of this memorandum to his son, Mr Clifford Jones, who later became the Divisional Mechanical Engineer of the National Coal Board South Western Division. We shall have much to say hereafter about this memorandum, and content ourselves at this stage by saying that it was full of common-sense. Indeed, had its points and warnings been observed, the probability is that there would have been no disaster in 1966. But the memorandum was put into a drawer and forgotten until 1965.
The 1944 flowslide at Aberfan
Tip Number 4 at Aberfan started to be constructed in 1933. On 27th October 1944 a major flowslide occurred in this tip (although the report speculates that their may have been an earlier slide as well). This was a major failure – the spoil travelled about 500 metres. Indeed this slide is depressingly obvious in the images of the Aberfan site after the disaster
As the tribunal noted:
It is difficult to exaggerate the importance of this slide in 1944. To all who had eyes to see, it provided a constant and vivid reminder (if any were needed) that tips built on slopes can and do slip and, having once started, can and do travel long distances. Mr. Geoffrey Morgan, while denying (in common with the vast majority of the witnesses) any appreciation of the possibility that a tip slide could ever reach Aberfan village, conceded that”. . . once a tip of considerable proportions on a mountainside does slip, it is impossible to predict how far it will reach”.
The 1963 landslides in Tip Number 7
The 1966 disaster occurred on Tip Number 7. Sadly, this spoil heap had failed previously, in 1963, probably more than once. In fact the Tribunal provides little technical detail about this set of landslides, noting with barely contained anger that the National Coal Board had not been very forthcoming about the events. The tribunal quotes Mr W. R. King, the National Union of Mineworkers’ Lodge secretary:
“What I noticed on the day that I had a look at the tip in November (1963) was as if somebody had scooped the middle of the tip out with a huge shovel and also that the base of the tip had run forward. There was a distinct hole in the centre of the tip, and the top plateau of the tip had sunk a little, and the other feature then was the fact that slurry had run down for a considerable distance. . . . The hole extended up two-thirds of the tip itself . . . from the bottom. The width, as far as I could recall, (was) about 80 to 90 yards.”
Later the report provides a little more detail:
Although on Day 65 Mr. Piggott, the National Coal Board expert, accepted that . . . “there were signs of failure and degrees of failure on the tip from about 1963 onwards”, it was not until the 66th sitting of the Tribunal that the issue of whether or not there had been a slide of Tip 7 late in 1963 was removed from the realm of controversy. This was when Professor Nash, the expert witness called by the National Coal Board, agreed that the relevant aerial photograph established (a) that there had been a rotational slip of the tip which was quite different from a tailings run, (b) that a big volume of material had moved, though it might not have moved very far, and (c) that the result of this movement would inevitably have been observed by any proper investigation of the tip.
The Tribunal notes that the slope showed signs of movement and deformation from then right up until the failure. The Tribunal notes that:
Two convincing witnesses, Mr D. T. Jones and Mr M. W. Maybank, testified that they were able to judge by reference to a dead tree (known locally as Hangman’s Tree) on the mountainside that during the last six months before the disaster the toe of Tip 7 advanced downwards by some 20-30 feet. There is credible evidence that in the last three to four months there were frequent sinkings of the top of the tip of up to four feet and that a few times during that period the sinkings were of 10-12 feet. These occurred right across from one side of the tip to the other at the point where a ridge had existed ever since the major slide of 1963.
A failure to learn lessons
It is now clear that, in addition to the failures described in the report, other slips and flowslides occurred in spoil heaps in the South Wales coalfield. The failure to learn lessons from these multiple accidents, and the lack of recognition that spoil heaps were hazardous, is extraordinary, especially as the risks had been documented. In addition, there was an extraordinary local failure to recognise that the tips at Aberfan were particularly problematic.
Despite this, not a single National Coal Board employee was prosecuted, dismissed or even demoted in the aftermath of the accident.
Post 3: Aberfan: The National Coal Board failures part 2
Above I have described how the National Coal Board failed to recognise, or just ignored, the risks posed by spoil heaps, despite multiple previous failures. Some of these occurred at Aberfan itself. But this was not the only failure by the National Coal Board in the period leading up to the collapse. The Official Tribunal was also scathing about the siting of the spoil heaps at Aberfan:
With the enduring reminder of the 1944 slide so clearly visible and its causes still remaining unknown, no fresh tipping on the mountainside should have been begun without a complete survey, without boreholes, without proper drainage, and without indicating the limits of the tipping area. And even without a survey, reference to the available geological map would have revealed a line of springs at the Brithdir seam, the Ordnance Survey would have given warning of watercourses, and the site would thus have been revealed as obviously unsuitable for tipping beyond a short distance from the rail incline. Indeed, even without referring to a single map, we are satisfied that there were features clearly to be seen which should have brought home to Mr. R. N. Lewis (Colliery Manager) and Mr. Joseph Baker (Group Mechanical Engineer) how limited was the area of suitable tipping land there available to them.
So why did the Tribunal determine that the site was so unsuitable for the siting of a spoil heap? This lies at the heart of the collapse.
Britain is an exceptionally well-mapped country, such that both the mine planners and the Tribunal has access to very high quality, unbiased maps of the terrain prior to the construction of the tips.
[A number of streams] flow down into the valley from these springs. The investigations were led by Professor A.W. Bishop of Imperial College, an authority in soil mechanics and slope behaviour. The Tribunal notes that Professor Bishop highlighted that this water contributed to the landslide in four ways:
I. Water issuing beneath the tip has caused back-sapping [this is erosion on the downslope face of the tip] and led to recurrent movements over the years since 1963.
II. Water under pressure acting in the tip material and in the limited area of the foundation where the slip surface was adjacent to the natural ground reduced the effective stresses in the fill and initiated a shear displacement. In view of the presence of pre-existing slip surface, this pressure need not have been very large.
III. Water filling (or nearly filling) the voids of the loose fill comprising the tip and covering the area of mountainside below it made it susceptible to a catastrophic flow slide, since a shear displacement or shock wave could result in the transfer of most of the load on to the relatively incompressible water in the voids, thus reducing the frictional strength to a very low value.
IV. Water released by the slip and consequent flow slide caused a ‘mud run’ of tip rubbish.”
The key mechanism is the second if course, in which the rising water level decreased the resistance to shear, allowing the slope to fail. The construction of the tips on top of the springs and their associated streams, without any means for the water to be managed, inevitably meant that water would collect in the spoil heaps. This was utter folly.
The point about pre-existing shear surface is critical – Bishop found that Tip Number 7 had been built upon waste from earlier failures, and of course had previously slipped. This meant that the materials were weaker than when freshly tipped, and so more likely to slip. But the slope was also mantled with a layer of glacial till, commonly known as boulder clay in the UK, upon which the tip had been constructed. This boulder clay may have provided an additional weak layer that allowed the tip to deform (it did not form the shear surface of the landslide itself), and it may also have prevented drainage of the water that was ponding in the tip. Finally, the role of the springs may have been exacerbated by mining disturbance, which had opened up new pathways for water to flow from the slope, probably nearer to the valley floor, and thus increased the ponding of water in the slope.
Thus, the Tribunal was clear about the failures by the National Coal Board. They highlight that it is obvious that construction of a tip on a pre-existing slope requires additional consideration, and in particular detailed site investigation. The Tribunal is clear that the National Coal Board did not undertake adequate site investigation, did not prepare the site correctly, did not plan the expansion of the tips (particularly with respect to allowing a new tip to be built on the deposit of a previous failure), and did not manage the tips in a responsible manner.
In the modern context, a basic requirement would be to undertake proper site investigation, to remove weak materials from the land surface before tipping begins, to build culverts to allow the springs to flow, to actively drain the water from the waste, to plan the tips and to monitor their stability. This has prevented repetition of this disaster in most developed countries, but as I point out in my New Civil Engineer article, water-induced failures of mine waste are still far too common in some places.
[60] years on it is hard not to be horrified by the multiple failures of management that led to this catastrophe.
Post 4: Aberfan: What happened next?
In the stunned aftermath of the Aberfan tragedy, a sense prevailed that there must never be a repeat. The Official Tribunal worked efficiently, and the final report pulls no punches about individual and corporate responsibility, even if this did not translate into criminal prosecutions. As I have noted previously, a remarkable aspect of the Tribunal is the belligerence of the National Coal Board – even more remarkable for the fact that it was a government body – to the extent that the Tribunal report includes a section entitled “The attitude of the National Coal Board“. The section on liability starts with the following observation:
Blameworthiness for the disaster of 1966 remained an issue strongly contested by the National Coal Board for the greater part of the Tribunal’s sittings
This is indeed the case, although ultimately they did concede responsibility, and the Tribunal report does not hide its distaste for the way that the National Coal Board conducted themselves. Given the facts of the case, how could the National Coal Board have argued that they were not to blame?
At the start of the Tribunal, the National Coal Board claimed that:
“The Board’s view is that the disaster was due to a coincidence of a set of geological factors, each of which in itself is not exceptional but which collectively created a particularly critical geological environment.”
The Tribunal report notes that:
The Tribunal is in no doubt that this was the starting-point of an attempt, persisted in for many weeks by the National Coal Board, to persuade acceptance of the view that the concatenation of geological features on Merthyr Mountain was such as could not reasonably have been expected to exist. The observation quoted at first sounded impressive, but it turned out that it explained nothing.
The Tribunal is particularly critical, and rightly so, of Lord Robens, the Chairman of the National Coal Board, who gave evidence to the Tribunal investigation the Aberfan tragedy. The report notes that within two days of the disaster Lord Robens had made the following comment to a television reporter:
“It was impossible to know that there was a spring in the heart of this tip which was turning the centre of the mountain into sludge”.
This was of course clearly not the case – the Ordnance Survey maps clearly showed these springs. Despite this, the Tribunal notes that this remained the position of the National Coal Board until Day 65, and even then they only changed their position under cross-examination. Late in the day, the Tribunal decided to give Lord Robens the opportunity to give evidence. Remarkably, he initially maintained his position that the hazard could not have been known, and thus that the Aberfan tragedy could not have been anticipated:
I think it would have been apparent to anybody that what I was saying is that the people on the site did not know, and it would have been impossible for them to know, because we had failed as a Board to provide the necessary regulation [sic] to enable them to know…
The criticism of this position by the Tribunal is scathing:
That this interpretation was placed on his words by no other National Coal Board witness who was asked to deal with them and, furthermore, had not occurred even to learned counsel appearing for the National Coal Board, emerged clearly in the course of the Inquiry. Nor did we accept it for one moment. Ultimately, even counsel for the National Coal Board invited the Tribunal to ignore it. By his words, read in their entirety, Lord Robens had conveyed to no-one that he was accepting that any measure of blame lay with the National Coal Board.
Hidden in this statement is a remarkable observation:
Ultimately, even counsel for the National Coal Board invited the Tribunal to ignore it.
Thus, even the lawyers for the National Coal Board directed the Tribunal to consider Lord Robens to be an unreliable witness. The Tribunal also noted that during his cross-examination, Lord Robens eventually conceded that the National Coal Board had determined that the instability was foreseeable, even before the Tribunal itself began. The report notes:
If the position really was as Lord Robens said (viz, that before ever the Inquiry opened the National Coal Board realised that the instability of Tip 7 was reasonably detectable before the disaster) it followed that a vast amount of time had been unnecessarily spent on issues which were directed at establishing that very point.
Recommendations of the Tribunal
The Tribunal made a number of recommendations. The first concerned the site itself – the Tribunal of course recommended that the site be made safe, but noted the objections by the National Coal Board to the ideal solution, removal of the tips altogether. Thus, the Tribunal recommended recontouring and drainage. I return to this below.
The Tribunal also made clear recommendations about the assessment of sites to be used for tipping, and about management of the tips themselves, primarily through a National Tip Safety Committee, with properly qualified experts. The Tribunal notes the importance of proper governance, responsibility and accountability. This was enshrined in law in 1969. That there has been no repeat of Aberfan in the UK suggests that these recommendations were effective.
The scandal of the unquestionably unlawful extraction of money from the Disaster Fund to pay for the removal of the tips
In the aftermath of the Aberfan tragedy, the public donated £1,606,000 in almost 90,000 individual contributions to a Disaster Fund. In 1966 this was a vast sum of money (wikipedia estimates that this is £27.8 million by 2015 values). After the disaster, a decision was taken to remove the tips above Aberfan, although the National Coal Board maintained a view that as they were not dangerous they had no responsibility for the costs of this operation. Under “intolerable pressure” from the Labour government, but in secret, the trustees of the Disaster Fund agreed to provide £150,000 to pay for the removal. This deed did not become fully clear until 1997; subsequently the regulator of charities in the UK, the Charities Commission, have ruled that this was “unquestionably unlawful”.
In 1997, the Labour Government of Tony Blair repaid the £150,000 to the Disaster Fund, but without any interest. Whilst this in some ways repairs some of the damage, that interest was not paid means that the Disaster Fund made, in effect, an interest-free long term loan to the National Coal Board.
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