Tumbi Quarry Declared Unsafe by Independent Consultants + Esso Highlands' Contractors had Already Caused Major Mudslide Incident! The Revelations Keep Coming.

LNG Watch has uncovered evidence that not only was the Tumbi quarry (QA1) declared unsafe by PNG LNG's Independent Environmental and Social Consultant (IESC),  D’Appolonia S.p, but that the contractors (MCJV) involved in the construction of the Komo Airfield were behind schedule (the quarry was being used for construction activity at the airfield). This combination of factors, LNG Watch has discovered, was leading to inadequate risk assessment. This situation was compounded by Esso Highlands’ insufficient project stewardship. These failures, it can be revealed, have already led to one major mudslide which was caused by construction work taking place before proper engineering and environmental review. 

In their March 2011 report the IESC observe (QA1 = Tumbi Quarry):

In a follow-up field visit made on 26 July 2011, the IESC complain:

The problem appears to be that the contractor working on the Komo airfield, was behind schedule. Indeed in their March 2011 report the IESC observe:

As a result of being behind schedule, the IESC claim that the project contractors were failing to take proper precautions. In a fortuitous statement, this failure to exercise due caution had already led to one major mudslide incident*:

Consequently, the IESC conclude:

We thus have evidence that project pressures were leading to a slip in risk assessment practices. Given that the Tumbi quarry was already declared unsafe, serious questions should be appearing in the mind of those conducting investigations into this tragic disaster that has taken dozens of lives. 

LNG Watch has also uncovered further evidence that there may have been blasting at the Tumbi quarry. To date, Esso Highlands (EHL) has denied there was blasting activities at the quarry, despite the fact that Landowners have claimed dynamite had been used.

In support of the landowner's testimony we have discovered that the operator was indeed planning to conduct blasting activities at the Tumbi quarry. In the 2nd Quarter Social and Environmental impact report published by LNG PNG in 2011 EHL states:

Perhaps this is not the smoking gun, but it is certainly suggestive that blasting was to be used. Adding to this suggestive evidence, is an observation made in the August 2011 report by the IESC. The IESC states aggregate for the Komo Airfield was in short supply, thus hampering an already behind project. 

This would suggest that the Tumbi Quarry was not only in desperate need (making the use of blasting more likely), it also increases the likeliness that proper risk assessments were not undertaken before extracting aggregate. Compounding problems, EHL were not exercising “sufficient ... stewardship”. Clearly the IESC were concerned that an under pressure contractor was deviating from their responsibility to the local communities, which was being compounded by a lack of EHL oversight.

While the National Disaster Committee (NDC) has dismissed landowner accusations out of hand in their January 26 report, clearly they have no reason to be so complacent. We now have evidence the quarry was declared unsafe in March 2011, the project operators were behind schedule, risk assessment practices were slipping, aggregate for the airfield construction was in short supply and Esso Highlands was not exercising sufficient stewardship. It beggars belief that the NDC failed to scrutinise the compelling evidence that has been produced by the project's IESC.

To date, LNG Watch has demanded an independent inquiry, and we have the support of the traditional landowners from the Tumbi area. Of course there exists at present a slapdash report that was composed by the NDC on 26 January. Its findings have already been questioned by international landslide expert Prof Dave Petley, and indeed the leader of the NDC investigation team, Martin Path. 

According to Martin Path an independent investigation unit has now been assigned to investigate the Tumbi disaster. This is not enough. LNG Watch and the traditional landowners demand a formal Commission of Inquiry that is entirely independent of the national government, the NDC, ExxonMobil (including their subsidiaries and contractors) and the Australian government. This Inquiry must include international landslide experts and social scientists. As Prof Petley has observed: "The methodology for such an investigation is well-established, but undertaking it requires very specialised skills.  Usually this will require an international team." While Dr Kristian Lasslett has added:

The investigative team should also have the resources to independently study the region, without over-reliance on datasets produced by ExxonMobil or its subsidiaries/contractors (unfortunately, there may be a dearth of independent data to draw on, which will make matters difficult). Furthermore, it is not enough to send in a team of natural scientists. While earth science specialists will of course be critical, the literature on disasters is clear, complex social factors mediate these types of events ... Consequently, if the right research questions are to be formulated, social scientists with relevant expertise must be utilised. 

This demand for an independent Commission of Inquiry is formally supported by the undersigned parties:

*The traditional landowners: Tokoya Piwago, Hibson Puma, Timothy Nogobe, Stanis Talu, Peter Potabe, Tiki Hale, Abe Okopi, Harabe Lembo, Daniel Huriba, Eric Kembe, Wandiago Kau, Tayali Ola, Kupiawi Aluya, Giya Hawi, Pila Pani, Olabe Kaloma, Urupu Andawi, Tom Waralo, Himuni Marako.

*LNG Watch Papua New Guinea.

*The Papua New Guinea Trade Union Congress

*The International State Crime Initiative 


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* The IESC has documented this mudslide in their March 2011 report: "Erosion and sediment control are critical components of construction activities. The efforts to date have had mixed success. In general, significant effort is being placed on controlling erosion, but at the HGCP camp construction site a significant failure occurred on November 13, 2010 whereby a mudslide originating at the HGCP spoil dump site blocked water behind the Komo road. This water overtopped the mudflow on November 14 and this allowed the mud to flow to the Tagari River along the path of the Akara Creek, a distance of 4.65 km. Fish in the Akara Creek were killed in the turbid water and mud, necessitating that downstream villagers be provided fresh water by CCJV, an activity that started on November 15. The failure took place in spoil from the EPC4 top camp placed by CCJV apparently without distributing the engineering drawing to all responsible parties or without undertaking a thorough assessment of engineering and environmental/social risk. EHL internally assigned a Level II environmental non-conformance for this event and it is therefore not necessary for the IESC to assign non-conformance. It is expected that the Akara Creek incident was an important lesson-learned for the Project".

Continued questions about the role of the quarry in the Tumbi Quarry landslide

By Prof Dave Petley

Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom. 

(Originally Posted on the Landslide Blog)

Interestingly, over the last few days there appears to have been increased interest in the role of the quarry in the Tumbi Quarry landslide.  Regular readers will remember that the National Disaster Center report indicated that the failure developed as subsidence close to the quarry.  Triggering of the landslide was associated with heavy rainfall, with no evidence to support this trigger, and no other mention was made of the quarry, even though it is clear from the images that a section of it was removed by the landslide.  In an earlier post I questioned both the evidence for rainfall / high groundwater as the trigger and the lack of consideration of the role that the trigger might have played.

Two recent statements have been reported by those associated with the disaster.  First, in a Radio Australia interview, Martin Path, who is the Principal Disaster Coordinator for the  Southern Highlands province in  Papua New Guinea, has given a rather different perspective to that from the official report(LAM is Sen Lam, the interviewer):

LAM: And Martin, at the time of the disaster, the landslide was blamed on blasting at nearby quarries, near the Exxon-Mobil LNG project in the Southern Highlands. Is a clearer picture emerging, of what happened, that early Tuesday morning? Are you getting a clearer picture now?

PATH: Not as yet. We have yet to conduct, er, we are conducting some portion of the independent investigation that the National … Council has endorsed. We believe that an independent investigation unit has been assigned, and we believe that this group would be up here over the weekend. But we also have the geo-hazard technical team on the ground now, since Day One. So they’re still providing the information, so with regards to the quarry that was established some years back, we have yet to establish the actual cause, what actually caused this slide.

There is a strange confusion here – “We have yet to conduct, er, we are conducting some portion of the independent investigation…We believe that an independent investigation unit has been assigned, and we believe that this group would be up here over the weekend.”  It is hard to interpret what is going on from that.

Second, my earlier posts have been picked up by the PNG Industry News website, who then have some comments from an ExxonMobil spokesperson:

An ExxonMobil spokesperson previously told PNGIndustryNews.net that PNG LNG contractors did not conduct any blasting at the Tumbi quarry.

She said a project contractor completed work at the Tumbi quarry in August, 2011.

“There was no need for [PNG LNG-related] blasting at this quarry,” she said.

“The Tumbi quarry has been operating for over two decades.”

There are two issues here.  First, the spokesperson notes that there had been no blasting at the quarry, which is in contradiction to the reports from local people.  I have no way of verifying this either way.  Second, she suggests that work associated with the LNG project ceased six or so months ago.  The unstated implication is that this means that the Exxon-Mobile work was not responsible for the collapse.

However, unfortunately slope behaviour is not as simple as that.  Whilst slope collapses can occur spontaneously during quarrying, there is often a time gap between the processes that lead to failure, and the failure itself occurring.  This is a mechanism known as progressive failure, which was first described in the 1960s.  There are two elements to this:

1. It may well be that the quarrying operations occurred when groundwater levels were low, or indeed that the quarrying caused an initial drawdown (release) of groundwater.  In such circumstances, the groundwater recovers the stability of the slope can reduce, allowing a failure to develop.  Seco

2. Failure of the slope occurs when a shear surface is fully formed that allows the landslide to detach from the surrounding rock.  This is not a spontaneous process, but requires the formation and growth of planes of weakness.  Such a process can take weeks or even years.  I have written several papers on this very process, such as this (click on the title to download the paper):

Petley, D.N., Higuchi, T., Petley, D.J., Bulmer, M.H., and Carey, J.  2005. The development of progressive landslide failure in cohesive materials.  Geology, 33, 3, 201-204

It can be the case that cutting a slope in a process such as quarrying initiates the progressive failure mechanism, and allows the slope to collapse some time later.

None of this inevitably means that the quarry was the cause of the landslide.  It may have been the direct cause, it may have been one of several causes, or it may be irrelevant.  However, understanding its role is critical.  Once again I would emphasise that this can only be uncovered with a proper forensic investigation by a team who understand the complexity of this type of landslide.  This is not a trivial task, and will involve detailed field mapping; structural measurements; examining aerial and ground images before and after the landslide; examining the quarry design and operation; looking at rainfall records; etc. The methodology for such an investigation is well-established, but undertaking it requires very specialised skills.  Usually this will require an international team.

The loss of a significant number of lives really demands that this landslide is investigated properly.  I do hope that this process is now underway.

Papua New Guinea or Papua New Palmer

Only in the Financial media could you find such frank discussion of PNG's natural resources. Owned by foreigners, divided up among foreigners, for the benefit of foreigners. The family silver has been sold.  


Palmer mulls Exxon deal


Australian Financial Review, 6 February 2012

Mining billionaire Clive Palmer is considering an offer from ExxonMobil to secure rights to explore his expansive gas deposits in Papua New Guinea.

Mr Palmer said Exxon first approached him in 2010 and he held further discussions with the global oil giant again late last year.

PNG-based oil and gas company Chinampa Exploration, a subsidiary of Mr Palmer's Mineralogy, has offshore exploration licences at the northern end of the Gulf of Papua, west of the capital of Port Moresby.

Mr Palmer told The Australian Financial Review that Exxon had proposed "farm-out" arrangements whereby the major would fund exploration work to potentially tap into the area's gas deposits in return for a stake in the venture.

Chinampa holds oil and gas exploration licences covering more than 43,000 square kilometres. The company is in the very early stages of exploration and needs significant funding to help with high exploration costs.

Mr Palmer said he had spent $40 million on geological tests which showed there was potential to find gas when drilling begins.

"This project could be bigger than the North West Shelf - it's the most significant thing we're doing at the moment," Mr Palmer said.

"There's a $16 billion LNG project going on with Exxon at the moment and our gas [site] is right opposite that."

Mr Palmer said the offer from Exxon was "a standing offer" and "we're thinking about it".

"We don't want to make hasty decisions. But we're either going to develop it, joint venture it or do a deal with the Chinese."

Through its subsidiary Esso Highlands, ExxonMobil is already working on the $16 billion PNG liquefied natural gas project, where construction work has been disrupted by a recent landslide.

Asked about the proposed deal with Mr Palmer, Esso Highlands spokeswoman Rebecca Arnold said: "It's not ExxonMobil's practice to comment on commercial matters."

Mr Palmer declined to discuss the details of Exxon's offer but it is believed that, under the proposal, the company would get a certain percentage of Chinampa's tenements and would have an option to do more drilling down the track.

Chinampa has three exploration licences in shallow to deep water close to the planned LNG plant at Port Moresby.

Mr Palmer plans to make a formal announcement on the offer later this year. Chinampa has also been in discussions with the PNG government on the project.

Last June, Mr Palmer spoke at a dinner that raised about $10,000 for the country's United Resources Party. He has described PNG as "the promised land" and is hoping to find oil and gas to sell to China for the country's growing energy needs.

"If we find gas, we develop it and make billions of dollars out of it," he said.

"First we're looking at reserves and then the cost of extracting . . . But it looks very promising." There's a real need for more energy in the world."

Mr Palmer claimed the $40 million spent on 3D seismic geological tests revealed 22 trillion cubic feet of gas.

"We looked at a comparative company in the US with that many reserves and with that amount it's worth about $60 billion [in market capitalisation]," he said.

Oil and gas experts said while the geological tests would indicate a potential for drilling, it was too early to tell its value. PNG LNG is scheduled to start shipments to its Asian customers in 2014.

One expert who wished to remain anonymous said: "Exxon Mobil are very good at what they do and don't look at something unless they think there's potential."

ExxonMobil Employee/Contractor's Racist Rant

When researching coverage of the Tumbi landlside, we came across the Call Me Big Papua blog, written by an American employee of Exxon or one of their contractors. The employees name is Justin Reed. The racist and derogatory description of Papua New Guinea contained in the blog are disgusting. Two examples are provided below:

And this is from an earlier posting:

If you care to read more of this nonsense, the blog is still online: http://call-me-big-papua.blogspot.com/

We certainly hope this sort of attitude is not condoned by ExxonMobil or any of its contractors.

NDC's Martin Path Accuses Tumbi Victims of Fraud

To date, the NDC have colluded with ExxonMobil to produce a report on the Tumbi disaster, which international landlside expert, Prof Dave Petley, labelled "unimpressive". However, now the NDC's principal disaster coordinator, Martin Path, has the audacity to accuse the victim communities of fraud.

ABC Radio, 10 February 2012

So not only have the NDC protected ExxonMobil from being scrutinised, they are now attempting to paint ExxonMobil as the victim of a fraud perpetrated by local villagers, in order to extract money from the project operator. To date, it is not clear why the NDC is going to such unprecedented lengths to protect ExxonMobil. We do not know whether it is being instructed from the top (i.e. at a ministerial level), or whether this problematic relationship is being organised at an NDC level. But clearly if a Commission of Inquiry is to ever take place, the NDC will need to be at the top of their list to be investigated.

The Face of an Independent Investigation: The Tumbi Disaster Whitewash

Representatives from Exxon Mobil, AusAID and the NDC, 25 January 2012 

Further Commentary by Prof Petley on the NDC 'Report'

By Prof Dave Petley

Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom. 

(Originally Posted on the Landslide Blog)

Several people have asked what I mean by a proper landslide investigation with respect to the report on the Tumbi Quarry landslide.  To illustrate, one might compare these two reports:

1. The Tumbi Quarry landslide report, prepared by the National Disaster Center.

2. Report on the landslide that blocked SH 1 and the railway line near Rosy Morn Stream south of Kaikoura on 10 September 2010, prepared by GNS Science as part of the Geonet programme.

The GNS report is not long, and nor is it highly detailed.  However, it is throrough, it investigates and describes the landslide properly, and it allows evidence-based conclusions to be drawn about the landslide and its triggers and causes.

This should be the minimum level of report for a major landslide event.  Of course, in New Zealand (or indeed the UK) a landslide that killed 25 or more people would probably be investigated in very much more detail*.

*LNG Watch: The O'Neil government has demonstrated the capacity and willingness to conduct such an inquiry with respect to the MV Rabaul Queen disaster (it will be led by a retired Australian judge and will include international experts). The same will and capacity appears to be lacking with respect to the Tumbi disaster. Facebook contributors have asked the question, is ExxonMobil the critical difference.  

NBC and the Post-Courier have issued worrying reports on the disaster efforts in Tumbi. All energies are being directed at helping ExxonMobil, while the victims are left to suffer in silence. 

Govt told to honour agreement

Post Courier, 9 February, 2012

SETTLERS at the LNG project area want the Government and developer ExxonMobil to fulfill the relocation exercise signed in the agreements before the Tumbi debris is cleared and LNG road link reopened.

Hides landowner Chief Yokoya Piwago and Kobalu Chief Ega Ango said the Tumbi disaster should prompt the State and developer to speed up the relocation process before the start of the LNG project. Mr Piwago wants the LNG stakeholders to explain why they failed to deliver the relocation exercise and 25 of his immediate relatives perished and buried under the debris.

He said by the Government using the police and army to remove the debris and reopen the road showed it did not have concern for its citizens, their rights and their welfare. Mr Piwago said that policemen were heavily present at Tumbi to force the locals out of the area without due respect for the genuine landowners who perished in the disaster and were still buried.
Kobalu Chief Ango called on the police to be wary of using excessive force as the landowners were fighting for their rights that were overlooked which were simple and appropriate such as relocation of people.

Mr Ango said due to their failure the disaster had claimed the lives of the landowners who would have lived today if not of the LNG developments.
He asked the Government to be more realistic on whose interest it was serving - to get the maximum benefit for its citizens or serve the developer.

“It disappoints and brings fear on us when excessive force is used by the Government to reopen the road without fulfilling the documented and signed agreements for the safety of the locals,” he said.

Chief Ango said his people wanted the Government and the developer to deliver the promised packages with emphasizes on relocation as the priority and follow suit with other promised commitments made to the landowners.

He said those agreements penned at the Kokopo UBSA and LBBSA were important commitments ever made but the deliverance part of it was slow and urged the Government to also rectify before the debris were cleared.

“They said today we are fighting and tomorrow you our fellow Papua New Guineans will fight when such situation arises in your area and urged the locals serving in the project and State agents to fall behind them,” he said.

They want the State and developer to:
* retrieve the bodies in good shape to process for funeral service;
* fully comply with relocation exercise immediately before the reopening of the road;
* other promised benefits to be delivered and ;
* if not complied, he urged the locals to withhold their equipment and labor workforce so that the expatriates can be employed to work.

They said Papua New Guineans must stand together to fight for their common good and in this case show respect for those who perished as part of their culture

LNG Landowners Bloc Vulunpindi Haus

NBC News 9 February 2012

Photo: LOs outside Vulunpindi Haus

ExxonMobil Claim Tumbi Landowners are Lying

ExxonMobil has just informed PNGindustrynews.net that "there was no need for [PNG LNG-related] blasting at this [Tumbi] quarry". This directly contradicts testimony given by local landowners, who claim blasting occurred at the quarry at the centre of the deadly landslide which killed approximately 26 people. 


For example, on 29 January 2012, Timothy Nogobe informed LNG Watch: 

"We have ... come to conclude that what has  triggered the landslide is the quarry and the use of chemicals and dynamite to blast the quarry at the top of the mountain, this has changed the ground water (Tumbi and Tuku) for the rapid breakdown of the mountain Tumbi burying alive more than 25 people".

Clearly, this is a core evidentiary issue that now needs to be clarified; among many other. 


Unfortunately it wont be clarified. In a clear breach of basic due process, those who stand accused of negligence, the PNG government and ExxonMobil are already colluding to ensure they get their stories straight. 


Indeed it was observed today in the Post-Courier: "Local authorities have had closed door meetings with the Local Disaster Management team, developers Oil Search and Exxonmobil, disaster officers from Port Moresby, Police and other stakeholders". Very cosy indeed and how transparent and independent. When will the NGOs, community groups and traditional landowner representatives be allowed into these closed door meetings.


On another note, we have also seen a shoddy pieces of research conducted by the National Disaster Committee, which has been slammed by international landslide experts, being paraded by the industry as fact: "There are claims blasting at the Tumbi quarry may have contributed to the landslide. But the NDC’s report found the landslide was caused by continuous heavy rainfall which weakened the underlying limestone and resulted in subsidence" (PNG Industry News, 8/2/12). If this was a balanced report, surely it should at least cite the eloquent response by Prof Dave Petley.


Sadly balance has gone out the window with the Tumbi disaster.


The whitewash is well under way.  

Money for ExxonMobil Yes; Money for Victims No!

This was published today by the Post-Courier/Pacnews, note the contrast to our previous post. This is reflective of a state that is run by and for the elite.


More than two weeks after the Tumbi landslip at Hides near the multi-billion kina LNG project site in Tari and authorities have made no efforts to retrieve the 25 or more bodies still buried in the landslide.

Hela Provincial Police Commander Supt John Anawe, who is co-ordinating the emergency and relief centre at Nogoli, said it would take some time before rescue workers move in and try to retrieve the bodies believed to be buried alive in the January 25 disaster.

Supt Anawe said it was likely that a mass graveyard would be declared in the landslide site if efforts to retrieve the bodies fail.

He said officers from the National Disaster Office in Port Moresby visited the disaster site last week and they were yet to finalise relief assistance to the relatives and victims of the disaster.

In the last few days, local authorities have had closed door meetings with the Local Disaster Management team, developers Oil Search and Exxonmobil, disaster officers from Port Moresby, Police and other stakeholders. 

The outcome has not be established so far.

Meanwhile, locals told the Post-Courier at the disaster site yesterday evening that the authorities are yet to give them relief support and compensation money.

This is despite the K10m that has been allocated last week by the National Government for emergency assistance to those affected by the landslip.

Locals also said the disaster was caused by heavy explosions, drilling and the development of the quarry for the LNG project and Exxonmobil must take full responsibility for the lives lost and properties destroyed in the disaster.

They also warned that they would not allow work to re-open in Nogoli, Hides and Komo highway if they are not compensated.

Fuel and supplies bound for the LNG sites at Komo and Hides 4 areas are fast running out due to the road blocks, and work on the LNG sites have been disrupted for two weeks now..


SOURCE: POST COURIER/PACNEWS

$4.5 Million US to Help ExxonMobil the 'True Victim' of the Tumbi Landslide

Can you believe it, the national government hasnt the resources to put together an investigation report on the Tumbi disaster that would pass 1st year university, but they can clear the road for their friends ExxonMobil. 


Landslide stops work at ExxonMobil's airport project


Radio New Zealand, 8 February 2012


The Papua New Guinea government has allocated more than four and a half million US dollars to clear a road damaged by a recent landslide, so that the Exxon Mobil airport project can resume in the Southern Highlands region.

The landslide struck in the vicinity of Exxon Mobil’s liquified natural gas project’s Nogoli base, burying a village and killing at least 25 people.

The minister for Transport and Works, Francis Awesa, says Exxon Mobil has also contributed money to have the road cleared.

Mr Awesa says it will benefit villagers in the Komo district as well as Exxon Mobil’s airport project, which has come to a halt since the landslide.

“In the Komo area work stopped because there’s no fuel, you can’t get fuel in there because the road is blocked so we’re trying to get the road cleared in order to get fuel in there and people, villagers and government officials moving in and out of the area, and then the project personnel and contractors.”

Francis Awesa says they hope to get road access in the next few weeks.

The National and the Salvation Army Aid and Abet ExxonMobil

At the moment it is not clear whether Esso Highlands (ExxonMobil subsidiary) is liable for the landslide in Tumbi. The government, as we predicted, are trying to whitewash the whole affair; using the tragedy of the Rabaul Queen as a diversion. 


And the media is happy to play its part by failing to ask absolutely basic and essential questions. Worse still, The National has come out and published Esso Highland's latest press release as a news report. Corporate public relations offensives, particularly in light of possible criminality, should not be given free air play; if they want to advertise their efforts, let them pay for an advertisement. 


Furthermore, the Salvation Army (see below) should be ashamed of itself. By taking money from a key suspect in this affair, they are now complicit if any criminal activity is uncovered with respect to this disaster. 


The Press Release

The News Report

Esso assists in relief efforts

The National, Wednesday 08th Febuary 2012

ESSO Highlands Ltd, operator of the LNG project, has donated K179,000 to support relief efforts following the landslide in Southern Highlands.
The amount will be given to the Papua New Guinea Salvation Army.
It includes a K41,000 donation made last year to the Salvation Army Red Shield Appeal.

The Salvation Army will use the money to support the affected people in the Hides area.

Esso managing director Peter Graham said the thoughts of all their employees and contractors were with the people affected by the landslide.

“This is a difficult time for families in the area who are mourning their loved ones,” he said.

“Our support for the Salvation Army will go toward assisting these families.

“We continue to offer our support to the government and the community and have already provided assistance in the form of transportation, food and temporary housing.

“We stand ready and willing to assist the government in their efforts.”
Major Rex Johnson, the Salvation Army’s secretary for programmes, welcomed the support.

“This donation will enable the Salvation Army to carry out its disaster management and relief work in a more efficient and effective way. Our prayers are with the families affected by the landslide in the Hides area.”

Landslide Expert Appraises National Disaster Commission Report on Tumbi Landslide

By Prof Dave Petley

Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom. 

(Originally Posted on the Landslide Blog)

The National Disaster Council of Papua New Guinea has posted online a report into the Tumbi Quarry landslide (see previous posts here, here, and here).  Presumably this is the “official investigation” that was promised.  They should be credited with making this available online, and the document has some useful information on, and images of, the landslide.  It is also helpful to get the official view on the landslide event, and there is a management plan for the victims and survivors of the accident.

However, there are aspects of the report that are perhaps interesting, as follows:

1. The report only very briefly mentions the quarry.  The report states that “naturally high geological weaknesses assisted by abnormally high rain fall combined to cause subsidence to the immediate north west of the quarry triggering a landslide of composite debris.”  The image on the front cover clearly shows a part of the quarry, with some of the benches truncated by the lateral margin of the landslide:

The report is ambiguous as to whether this means that the landslide was associated with the quarry.  It maybe that the quarry access / haul road also crossed the area now destroyed by the landslide (as per the Esso Highlands plan), and yet this is also not discussed.  Clearly at least a part of the quarry was lost in the landslide, so a proper discussion of whether the quarry played a role in activating these weaknesses seems essential to me.

Note also that these naturally-occurring geological weaknesses are not described or discussed (I assume that this means a set of joints?), and the mechanism of “subsidence” is also quite strange.

2. The landslide trigger is definitively described as being rainfall, on the basis that there was no recorded seismicity.  However, although “continuous heavy rainfall” is described, there is no data to support this, and no eye-witness reports.  The next sentence talks about “abnormally high rainfall”, but I can find no other reference to this event.  I wonder what evidence there is for this abnormal rainfall event, given the high rainfall that this area is likely to receive anyway.

3. There are odd aspects of the landslide mechanism as described in the report  First, the report notes that pools and seepage on the shear face indicate that the “ground water rose significantly above its historical levels”.  I do not understand this logic.  Seepage and pools are likely to occur in the aftermath of almost any deep landslide of this type, and I do not see why they indicate that the groundwater levels were abnormally high, or indeed that groundwater even played a substantial role.  Second, the report notes that the initial assessment team “saw clear evidence of liquefaction of the rock formation”.  This is most surprising.  Limestone is not a material that undergoes liquefaction – I have never heard of such a mechanism in a hard rock – and so I just cannot understand this purported process.  Unfortunately, it is not discussed further.

So overall, whilst the description of the site is really helpful, though it would be good to see a more detailed consideration of the ways in which the quarry might have been a factor in activating these geological weaknesses.  In designing a quarry it is normal practice to ensure that such natural weaknesses are not exposed to the point that they can permit slope failure to occur.

To my mind this report should not be considered to be the definitive analysis of this landslide.  Much more detailed analysis is needed, and lessons need to be learnt in terms of other slopes in Papua New Guinea.