Tangjiashan again - and a possible new Chinese flowslide

Back in 2008 I dedicated a great deal of space on this blog to the extraordinary efforts by the Chinese Army to draining the landslide lake at Tangjiashan, just above the town of Beichuan, which was created by the May 2008 Wenchuan Earthquake. 

 These efforts were ultimately successful, but in my visit to the site in Spring 2009 it was clear that a threat remained at the site in the form of another block of material that was showing signs of deformation. Over the last few days this area has received very high levels of rainfall.  Yesterday, Xinhua reported that a 300,000 cubic metre block has detached from the scarp above the barrier, and blocked the river to a depth of 10 metres:

"More than 6,200 residents were relocated Tuesday as torrential rains pounded Beichuan Qiang Autonomous County in southwest China's Sichuan Province, local authorities said Tuesday...Some 300,000 cubic meters of debris brought by the landslide caused a dam, blocking the lake's outlet. The dam's lowest point is 10 meters higher than the present water level, the statement said.  Debris still continue to come down from the hills, and if there were more rains, then the lake level would further rise, threatening the lives of people in nearby townships.The rains had disrupted the normal life of 58,000 local residents in the county, causing huge economic losses, the statement said."

China is well-versed in dealing with these hazards, but given the magnitude of the destruction in the Beichuan area, such events must cause great heart-ache.

It is clear that the elevated level of landslide activity in the aftermath of the landslide is a major issue.  I am travelling to Chengdu on Sunday, so will see whether I can ascertain more information about these issues.

Meanwhile, Bloomberg reports a probable flowslide failure in a tin mine in Guangdong yesterday:

Zijin Mining Group Co. said a dam built to hold tin-mining waste collapsed in China’s Guangdong province following torrential rain, less than three months after one of its copper mines leaked toxic waste into a river.About 60 centimeters (24 inches) of rain from Typhoon Fanapi and mud and rock slides triggered the accident at the company’s Yinyan tin mine at about 10 a.m. local time today, Shanghang, Fujian province-based Zijin said in a statement. 

China has been impacted by a series of these events in recent years, including one that caused multiple fatalities in 2008.  There appears to be a strong need to improve the safety of these facilities before another major accident occurs.

Poor mining management was the cause of the Sigou Village landslide in China

Back in August I posted a couple of times on a fatal landslide in at Lifan (sometimes written Loufan) in Sigou County in Shanxi Province in China (the posts are here and here), which appeared to be a mining related flowslide that killed 45 people. Yesterday the People's Daily website ran a story explaining the results of the enquiry into the landslide:

"Illegal production and slack safety oversight were main causes for the landslide in north China which killed 45 in early August, investigation result showed Friday. Some 37 had been detained for investigation as they were allegedly responsible for the fatal landslide in Shanxi Province which left another one injured, and resulted in an economic losses of 30.8 million yuan (4.53 million U.S. dollars), according to a statement issued by the investigation team led by the State Council, or cabinet.

Thirteen people including Yan Quewa, head of a local iron mine where the tragedy happened, have been prosecuted, while 24 others have received administrative and Party disciplinary punishment. The local mine was imposed a fine of 5 million yuan. On Aug. 1, the landslide toppled a waste dump of the mine and buried Sigou Village of Loufan County in the suburbs of the provincial capital Taiyuan. The waste dump, within 200 meters from the village, belongs to Jianshan Iron Mine. It was operated by Taiyuan Iron and Steel (Group) Company Ltd.

Chinese law stipulates such dumps should be at least 500 meters away from residential areas and should have embankments or walls to contain dust or prevent landslides. The dump near Sigou, however, had none."

The mining and quarrying industry in China has a dreadful safety record.

Disastrous mining related landslide in Burma / Myanmar

A few days ago on 3rd July a major landslide occurred in northern Burma (Myanmar) that appears to have affected a huge number of people. The excellent ReliefWeb site is carrying reports of the UN OCHA response to the disaster. The OCHA report states that:

"On the 4th of July 2009, a landslide caused by heavy rains swept away a jade miners' settlement along the Uru River in Hpakant Township (also sometimes spelt Phakant), northern Kachin State. Another jade mining city, Seng Tawng, was also reported to have been affected by the floods. Villages in the surrounding area are also reported to be affected. In the absence of a credible assessment, initial information collected reveals a wide range of disparate mortality and affected population levels. It is anticipated that clearer fatality and casualty figures will be available within the next days. The New Light of Myanmar, a State-run newspaper, reports the number of fatalities to be 24 at this stage.In Hpakant, it is reported that a total of between 900 and 1,000 individuals are currently accommodated in a total of five informal displacement locations, including four monasteries and one school. Similarly, approximately 200 individuals are currently accommodated in a monastery in Tar Ma Hkan. The population in these locations is reported to include families"

So clearly this was a pretty serious event. Unfortunately, this is one of those occasions in which Google Earth just doesn't do the business due to the resolution of the imagery:


However, there is a local website for Hpakant set up by AKSYU (a campaigning human rights group from the Kachin area). Interesting, the website reports that:

"The death toll has risen to 70 in the aftermath of floods and landslides in Burma's Hpakant jade mining area in the country's northern Kachin State on July 4 and 5. Hundreds have been injured including over 10 people from local Kachin Baptist Churches, according to official figures available from Burmese Army authorities. The floods and mudslides were the biggest ever witnessed in Hpakant jade land. The devastation was said to have been caused because the ruling junta has been allowing indiscriminate jade mining activities with sophisticated machines following the ceasefire agreement between the regime and the Kachin Independence Organization (KIO) in 1994, said local environmentalists. The death toll was compiled till yesterday by the administrative office of the Hpakant Jade Mining City also called the City Peace and Development Council (Ma Ya Ka) of the junta, said Hpakant residents. The search for bodies in jade land is underway and an additional 30 bodies were found under soil and slush dug out from the jade mines yesterday evening, a resident of Hpakant told KNG today. Eyewitnesses said they saw dozens of bodies being carried in trucks while people were searching for more bodies under the soil heads which came crashing down in the heavy downpour. Most of the deaths resulted from the mudslides because of the high land dug for the jade mines and because most villages were constructed on low land near the Uru River, according to residents of Hpakant. The Hpakant government hospital is full of people with injuries as of Saturday night but a callous Burmese military authority is yet to launch any rescue mission for the victims, said residents of Hpakant. Residents expect the death toll to touch several hundred because over seven main jade mining villages were severely affected by the flood from the Uru River which brought down heaps of soil and mud dug out from thousands of jade mines near their villages. The three major jade mining cities of Hpakant, Lonkin (also called Lawng Hkang in Kachin) and Seng Tawng were flooded by the Uru River. However the water is receding since yesterday, added residents. Private and non-government rescue and relief missions were started yesterday in some of the flood and landslide affected areas like Hpakant city, Maw One, Seng Tawng and Lonkin after the rain and floods stopped, said locals. Soon after the floods, the Hpakant Regional Kachin Baptist Convention under the Kachin Baptist Convention (KBC), the biggest Kachin Christian body in the country formed an emergency committee. It is implementing rescue and relief missions, said a KBC staff member in Myitkyina, the capital of Kachin State. Roads in most villages in Hpakant jade land are covered with over three-foot of mud and slush allowing only ferry transportation, said local residents. Residents of Hpakant city are now busy cleaning their inundated homes. They are facing an acute shortage of clean water, said residents."

So is it possible that a death toll of several hundred could have occurred here, or is it an exaggeration? Well, let's take a look at a couple of the images of the mines in the Hpakant area that AKSYU have on their site, which can be accessed here:

(click on the images for a better view in a new window)

To call this a disaster just waiting to happen is something of an understatement. This image shows how the spoil dumping has occurred (note the people on the nearer slope for scale):


The combination of dumping at the angle of repose in dry conditions, and the villages in such close proximity to the mine dumps, makes a large-scale landslide disaster a distinct possibility:

It remains impossible to know what has happened - I will keep an eye on the UN and other web sites to see if anything appears. An flowslide type of failure must be a worry in this sort of setting though.

Another Chinese tailings dam failure

The Chinese media are reporting another tailings dam failure, this time in Hunan province. Fortunately, the effects appear to be far less devastating than this event last year. The reports suggest that a manganese ore tailings dam failed in Huayuan County, Xiangxi Autonomous Prefecture in Hunan Province early on Thursday morning, releasing a flowslide that hit a house, killing three people and injuring four more.

The Tennessee flow slide accident - what went wrong?

The fallout from the recent flowslide accident at the Tennessee Valley Authority's (TVA) Kingston power plant in the USA on 22nd December, which I highlighted here, continue. There is an increasing sense that this was an unacceptable failure (it is hard to argue with that) and that it was lucky that there was not a loss of life in the accident.

This AP image is a good starting point as it is much clearer from this as to what has happened:

Perhaps the most useful resource though is this article from the www.tennessean.com, which I thoroughly recommend. It provides an excellent interpretation of what happened in the lead up to the accident. They have provided two aerial images of the site, before:

And after:


The gist of the article is as follows:

1. The failure occurred on a 20 m high embankment constructed primarily from ash blocks that collected in the base of the plant's burners. The fly ash is deposited into the lagoon in a wet state;
   
2. In November 2003 the lagoon suffered from a blow out (failure) caused by piping and seepage (i.e. water starts to flow through the ash, which then induces erosion. This then allows a pipe to form, which collects, channels and accelerates the flow, allowing erosion to intensify. This can rapidly create a weak zone);
3. In December 2003 a mitigation scheme was proposed, consisting of "a series of trench drains at different levels on the dike, another drain at the base of the mound and a riprap (i.e. armoured) channel."
4. This mitigation scheme was completed in October 2005
5. In 2006 a further failure occurred, with a 1.5 x 1.5 m section failing through seepage, releasing some ash;
   
6. This section was repaired and wells were installed behind the embankment, presumably to lower water pressure, monitored using 30 shallow piezometers;
7. The article mentions that the embankment was inspected and passed in a report produced on 15th February 2008 and found to be stable, but that "plant operators were commended for mowing the landfill slopes. Trees too large to be mowed should be cut, the stumps removed, the area backfilled with soil and seeded". "They mentioned small trees being removed," said Tschantz, the dam safety consultant. "I'm wondering if trees had a role to play. You don't just pull those things out. The root channels have to be filled and compacted."

In December 2008 the site received 125 mm of rainfall (the average for December is 70 mm). Failure occurred on 22nd December.

Clearly it is far too early to identify exactly what has gone wrong or who, if anyone, is to blame. The key issues must be to clear up the mess and to learn the lessons, especially if there are other sites that are also vulnerable to failure. One suspects that the costs of this incident will be very high indeed - far more than the cost of constructing a safe embankment in the first place.

I do recommend the article (here) - it appears to be a good piece of journalism.

As an aside, it appears from the images that sections of the embankment have been moved intact (see image below - these can also be seen in the photo at the top of this post):

The sides of the embankment also appear to have failed (marked "lateral failure?" above). This suggests to me that pore pressures in the ash were very high indeed. I wonder if a factor here is the use of ash in the embankment as its comparatively low density might have made the embankment rather vulnerable to failure due to high buoyancy forces.

Ash flowslide at Knoxville, Tennessee

A few months ago Shaanxi Province in China suffered a dreadful flowslide when the dam holding back mine wastes collapsed, releasing an avalanche of material onto the town below. About 260 people were killed. On 22nd December, what appears to be a similar failure occurred at Knoxville in Tennessee, USA, when the retaining wall holding back coal ash from the Tennessee Valley Authority Kingston Steam Plant in Harriman power station collapsed, releasing an estimate 2 million cubic metres of waste, which then flowed down slope (image from Knoxnews).


Fortunately, the area below was only sparsely inhabited, so in this case no-one has been killed, but about a dozen homes have been rendered uninhabitable and, as the picture above shows, a train was also hit (image from Knoxnews).


Microsoft Virtual Earth has this rather nice black and white image of the site, which I have annotated to show the salient features (click on the image for a better view in a new window):


The image below shows the crown of the failed area (see annotation) - comaprison with the above image confirms which part of the storage pond has failed (image from Knoxnews):


However, as the image below shows, the failure affected a very large part of this lower set of ponds (image from Knoxnews):


My current interpretation of what has happened is shown below, which is an annotated zoom-in of the MicrosoftVirtual Earth image above:


Interestingly, the mass of mobile ash also appears in places to have caused the ground to fail without flowing. This image shows the access road to the site - note how the material has moved forward over the road without fluidising (image from Knoxnews):


That such a failure should occur is extraordinary, given that the danger of flowslides has been known for over 40 years. The only fortunate aspect of this is that no-one was killed, which seems to be a matter of luck given the volume and mobility of this landslide. However, coal ash is an unpleasant material (which is why it is stored in ponds like this), sometimes containing lad, arsenic and mercury amongst other heavy metals, although in very low concentrations. The major issue will probably be dealing with the sludge before it enters the watercourses.

Accidents like this should not be allowed to happen - they are utterly avoidable. I hope that a review is underway to ensure that there is no repeat.

The Lifan landslide - from natural disaster to cover up

In China this summer there have been two big mining-related flowslides. The second, at Linfen County in Shanxi Province attracted a great deal of publicity (see my blog reports here and here), not least because of the very high death toll. However, the story of the first, which happened on 1st August at Lifan, also in Shanxi Province, is a great deal more murky, but details are now emerging.

On the day after the slide there were a series of reports that it had occurred and that 11 people had been killed. I picked up a Xinua report for example that stated that:

"More than 100 rescuers are clearing the landslide debris under which 11 people have been confirmed buried in north China's Shanxi Province. The landslide was in the early hours on Friday at Sigou Village in Loufan County. An initial investigation showed seven houses and11 villagers were buried, according to rescuers. Rescuers were working in shifts with excavators to clear the debris of stone and earth with an estimated volume of more than 100,000 cubic meters. The landslide site has resumed power and communications supply. "

Note that there is no mention here that the failure occurred in the dump from an iron ore mine, and the suggestion is that there was a large-scale and rapid response. In late August to mid September a different picture started to emerge. This suggested that in fact the failure had been a flowslide from an iron ore mine and, more importantly, that there had been a cover-up by the authorities, who had failed to search for a substantially higher number of victims. Over the next few days a recovery operation was launched, and eventually it was ascertained that 44 people had been killed.

So what happened to expose this incident? Well, a Chinese newspaper, the Guangzho Daily, has now published an account together with an interview with the reporter who exposed this event. This interview has been translated and published with photographs here. The reporter, Sun Chunlong published an article in late August pointing out that there had been a cover up. He based the article on an undercover visit to the site in which he compiled a list of 41 victims from family members. It turns out that many of the victims were migrant workers for whom the local authorities seem to have had little regard. He then followed his article with a post on his blog on 14th September in the form of an open letter to the governor of Shanxi province. This letter (which is translated at the end of the article here) came to the attention of the Chinese Premier, Wen Jiabao, who ordered a recovery operation and allowed the new to emerge officially. Between 22nd and 29th September they uncovered many victims, providing a final toll of 41 bodies and six partial remains.

Now, a formal investigation has been launched both into the landslide itself, which is just one of a catalogue of mining-related fatal accidents in China, and of the subsequent cover-up.

Updates on the Cairo and Shanxi landslides

The search for victims in both the Manshiyet Nasser rockslide and Shanxi flowslide continues. The following is the latest news:

Manshiyet Nasser, Cairo
The number of recovered victims is now 107, with many more still believed to be trapped under the rubble. Clearly there are still extraordinary difficulties in getting beneath the large blocks. Interestingly, there is now a Quickbird image of the site, as highlighted by Almasry Alyoum. Below I have compared the before Google Earth image with the after Quickbird (click on the image for a better view - before in the left (Google Earth), after on the right (Quickbird)).

The Almasry article makes two interesting observations:

1. Since the Quickbird imagery was collected on 18th September, no official body has requested or made use of the images;
2. "The shots reveal that Muqattam Mountain may be vulnerable to other collapses, especially in its southern areas and in particular, its “Sharei tesa’ah” and “Maidan al-Naforah" areas, said geologist of the National Authority for Space Sciences Muhammad Naguib Hegazy"

There is also a nice article about the human aspect of vulnerability in shanty town here.

Shanxi flowslide

AP image of the landslide debris

There is a good article reviewing the causes of the Shanxi flowslide here. Interestingly it states that:

1. The number of fatalities is now 265;
2. The landslide was not associated with a spell of we weather. Indeed, "The whole county had received only a minimum rainfall amounting to 1.5 mm since the beginning of September, according to the Xiangfen bureau. This amount was not enough to sufficiently wet the ground, let alone cause a mudslide, said specialists at the China Meteorological Bureau."

Another Chinese flowslide? 1st August 2008

Xinhua is today reporting that:

"The State Council, China's Cabinet, has sent a team to investigate the landslide that buried dozens of people in the northern Shanxi Province, but was initially played down by local authorities. The landslide toppled a waste dump of a local iron mine and buried Sigou Village in Loufan County in the suburbs of the provincial capital Taiyuan on Aug. 1."

The landslide was reported to have killed 11 people, but Xinhua notes that the toll may in fact be much higher:

"Eleven dead bodies were found by Aug. 16, and the official death toll ended there. Families complained at least 34 others had been trapped under more than 800,000 cubic meters of rocks and waste from the mine. The emergency rescue headquarters have since dug 122,000 cubic meters of waste to search for more victims, but to no avail. The exact number of people trapped remains unknown because most of them were migrants and were not registered at the local public security bureau, which means their disappearance might not be immediately reported."

The mining industry in China has a very poor safety record, with over 3,000 annual fatalities. However, it appears that there is also a substantial safety issue associated with the spoil tips and tailings dams. To be fair these problems have affected the mining industry worldwide and in each case have required a strong safety management ethos to be engendered as the industry matures. The fact that China is now reporting these events suggests that they are now getting a grip of this issue, but it will take a considerable amount of effort to deal with all of the problems.

Loss of life in the Manshiet Nasser (Cairo) and Taoshi township (Shaanxi) landslides

Xinhua is now reporting that the death toll in the Shaanxi landslide has now reached 254. They also report that the recovery teams are yet to search two channels in which local people believe more bodies are buried

AFP is reporting that the number of fatalities in the Manshiet Nasser (Cairo) landslide is now 82 people, with at least another week of recovery work to follow. Interestingly. they also report that "Residents have blamed the rock slide on work that had been going on for several weeks on the Moqattam hill overlooking the shantytown". It would be interesting to find out more about this work.

Updated: A flow slide disaster in China

UPDATED: New image of the site added
UPDATED: Google Earth image of location added.


Update: This image from http://aboutxinjiang.com/ shows the site of the failure. This confirms both the magnitude of the event and the type.

This has been a terrible week for landslide disasters. Sadly, news emerged yesterday of yet another, this time in Taoshi township, Linfen County in Shaanxi province. I think that I have managed to identify the location - see Google Earth image below (location is 35°54' N, 111°30' E). Initial reports suggested that 26 people had been killed; this has now been increased to 34, but it seems likely that the death toll is much higher.

Details are a little sketchy at the moment, but the suggestion appear to be that heavy rain caused a tailings dam to fail, releasing a large amount of material that swept as a debris flow down the valley. Xinhua has a limited commentary but a rather interesting set of images of the disaster:

The Xinhua report states that "The mud-rock flow ... destroyed a three-story office building, a market and some villagers' houses in the valley. Witness said the flow roared down the valley and washed away the market and the houses in a few minutes."

The description and images of the landslide suggest that this was what is termed a flowslide - this is a large volume debris flow consisting of soil, rock and water. They are able to move exceptionally fast and to travel large distances. Sadly the mining industry has a terrible record of flowslides originating from spoil heaps or the failure of tailings dams. Examples include:

There is a full if rather horrifying list of these events here. In most more developed countries the accidents at Aberfan, Buffalo Creek and Stava have meant that mine dumps are very tightly regulated, meaning that the accident rate is now low. The impact of not doing so are graphically illustrated by this pair of images (see this web page) of the Stava event in Italy (click on the image for a better view):

Here, 200,000 cubic metres of fluorite tailings flowed over 4 km downstream at over 90 km/h.