Risk of collapse of Hidroituango Dam hangs over Colombia

Above: The abutment of the Hidroituango dam, showing the unstable slopes. Image tweeted by UNGRD June 10 2018. Dam is almost full to the brim

The 225 m high Hindroituango Dam on Cauca River in Colombia continues to face emergency situation since April, and collapse of the dam is one of the likely possibilities. It’s a very large embankment dam being built Cauca River near to Ituango in Antioquia Province in Latima American country Colombia.  The dam, estimated to cost $2.8 billion, was due to be completed this year.  When operational it will generate 17% of the electricity demand of Colombia, but critics have been questioning the need for the dam. As we see through the details below, it is clear that the mega dam has been taken up without adequate geological, social and environmental studies, and now there is a big question mark if it will be successfully completed. There is a lot for the world to learn, here, including for Indian and South Asian Dam supporters.

Ominously, William Gutiérrez, a fisherman and gold prospector, after escaping the floods due to the dam last month, with nothing but the clothes he was wearing, told Guardian as vultures circled overhead: “We’ve always said this river could not be dammed. But the dam is more important to those in power than our lives.”

On May 16, the Guardian[i] reported: “Collapse of Engine room at Hidroituango Colombia’s largest hydroelectric dam project on river Cauca, creates emergency situation, thousands of river bank people ordered to evacuate their homes… On May 16, authorities issued evacuation orders for eight municipalities (total population 120 000) downstream from the dam amid fears of another wave… Videos circulating on local media show the harrowing scenes at the dam. One clip shows workers running from massive waves, while another shows flood water engulfing digging machinery. The latest emergency was triggered after an engine room at the dam reportedly collapsed… “There’s no humanitarian assistance here, it’s total abandonment – there’s no shelters, no food, no anything.” Isabel Cristina Zuleta, an activist with Ríos Vivos, a local environmental organisation long opposed to the project said. Three community leaders from the area were shot dead by unknown assailants this month in two separate incidents. Two of the victims were members of the Ríos Vivos movement and had been campaigning for compensation for communities affected by the project… The precise cause of the disaster is contentious. EPM’s manager, Jorge Londoño, told local media that “unpredictable geological conditions” had caused the tunnel to fill and then collapse over the weekend, while activists argue that it was caused by an accumulation of plant material left uncollected by the company.”

On May 21, 2018[ii], David  Petley wrote: “Over the last few days another landslide crisis has occurred at a hydroelectric dam site, this time at the large Hidroituango project in Colombia.”

In 2014, Empresas Públicas de Medellín (EPM) (responsible for the dam) diverted the Cauca River through two tunnels, each with a diameter of 14 m, to allow construction of the dam.  Earlier this year, as filling of the lake began, the water was diverted to a further, larger tunnel 200 m upstream from the first two.  The original tunnels were plugged with concrete.

Unfortunately, three landslides occurred at the site between 28th April and 7th May.  These landslides blocked the flow of water, and the lake started to fill to a dangerous level.  Concerns started to be expressed that the lake might overtop the dam, triggering collapse. Correction: it is now clear that the tunnel was blocked by a collapse event that propagated to the surface to generate a crater, rather than a conventional landslide.

The blockage of the tunnel started to cause the water level in the dam to rise, and evacuations were initiated.  To try to manage the risk, EPM attempted to dynamite the seals from the original two tunnels.  However, progress was to slow, leading to the decision on 10th May to drain the lake through the powerhouse, causing considerable damage.

But, on 12th May the main tunnel naturally unblocked, releasing a large volume of water that caused extensive flooding downstream.

Yet another example showing how landslide risks at hydropower projects are not managed properly.

Another post on the same date[iii] said that water was flowing through the vehicle access galleries of the dam, where water is not supposed to be there. The water flow from the vehicular access tunnel was “as a result of blocking two of four tunnels leading water out of the powerhouse.” Over 26000 people have been evacuated.

May 23, 2018: Petley blog[iv] notes: On April 8, 2018: “The major change is that impoundment has commenced, and the water level behind the dam is clearly rising.  The first sign of a problem appears on 2nd May 2018”.

On May 7, 2018: “The major issue is the crater that has formed above the tunnel that was being used to control the water flow.  This crater can be clearly seen just to the right of the lake at the bottom of the image, partially destroying a track with switchbacks.  It appears that the tunnel collapsed, creating the blockage and this surface feature.  Note also the significant landslide on the same side of the lake, presumably caused by the rising water level.”

On May 28, 2018, Petley wrote[v]: “On 26th May 2018 a further landslide[vi] occurred at the Ituango dam site (Hidroituango) in Colombia.  The slope failure led to the evacuation of the 1500 workers at the site… Images of the landslide[vii] suggest that it… occurred on a slope above the area that had been cut.”

One reader[viii] wrote back: “New significant cracks have formed in the hillside next to dam which is the main reason for new extended evacuations. These appear to be located above the latest landslide mention here near the spillway (immediately upstream of the dam). The cracks appear to run deep into the hillside and are visible within internal road tunnels in the hillside.”

Petley notes: “Landslides associated with impounding of the lake at a large dam are not unusual – the stability of the slopes declines as the groundwater level rises.  This latest slope failure is perhaps surprising in that it has occurred so high up the slope though. This site has now suffered the initial tunnel collapse, the large landslide a few hundred metres upstream of the Ituango dam site, and now this small landslide above the works.  These events continue to ask questions about the degree to which the geotechnical conditions of the site are fully understood.”

He quotes a local Spanish newspaper report: “After the collapse, the authorities made the decision to suspend vehicular traffic to and from the urban center of the Ituango municipality. Citizens who have to enter or leave the town on Sunday, May 27, presidential election day, will have to do it by boat.”

In the meantime, Hydroworld[ix] reported: “EPM must seek to deal with “catastrophic” flooding following construction problems at the site of its 2.4-GW Ituango hydroelectric project in northwestern Colombia… EPM says the emergency was caused by a landslide that blocked a tunnel used to regulate the flow of water between the dam’s spillway and the Cauca River… EPM’s website says that due to an obstruction in the diversion tunnel of the Cauca River that presented on April 29, a water dam was generated in the upper part of the dam, resulting in variations in the flow in the river downstream. Over the course of time, the tunnels have been blocked and unblocked… On Thursday, May 17, public prosecutors said they were probing allegations that public servants received illicit payments in the project’s contracting process.”

June 3, 2018: Petley[x] wrote: “Over the last few days the Hidroituango crisis in Colombia has deepened considerably… the Colombian President, Juan Manuel Santos stated that professional advice is that the level of risk has increased in recent days.  The major problem is once again that of landslides, with new slope instabilities becoming evident as the level of the lake has risen… The major issue appears to be a new landslide that has developed on the slopes above the dam… Whilst it might be hoped that this is a comparatively shallow slope failure, images from within the tunnels demonstrate that the cracks extend into the rock mass, unfortunately… the mass that is mobile is reported to have a volume of about 130,000 cubic metres.”

June 4, 2018: Petley[xi] wrote: “The geological experts who monitor the right mountain of the Hidroituango project 24 hours a day, detected a 6 millimeters per hour detachment this Sunday, according to the report of the Unified Command Post (PMU) installed in Ituango, North of Antioquia… The implication is that the landslide is currently in a secondary creep phase, but 6 mm per hour is not trivial… The article notes that the landslide was first detected on 29th May… Technicians of the UT company Grupo Líneas Suroccidente conducted an inspection in the mountain to know the conditions of two power transmission towers and after these works, it was known that there is a considerable risk scenario.  This inspection, which was also done with EPM officials on Tuesday, May 29, resulted in a report…, which argues that one of the towers could come down because “cracks are observed in the rock.”  This authority held that these cracks, known as “saprolitos”, are characterized by the fact that the rock becomes a kind of putty, because of the humidity, and it foresees new landslides in the mountain.

Saprolitos – presumably saprolite – is chemically weathered rock, which is common in tropical areas and is known for instability problems.  This of course raises questions as to the state of analysis of landslide hazard prior to construction of this project.”

On the proposal to carry out controlled landslide, Petley says: “Be very careful!  This is what was attempted at Vajont, with catastrophic consequences.  It may be the right approach, but can only be undertaken under very, very carefully controlled circumstances, and the potential for a much bigger failure than expected cannot be excluded.  Such an exercise should only be undertaken with very detailed preparation; I am not convinced that the current situation allows that.”

On June 5, 2018: Petley[xii] wrote: “In the last few hours, RCN Radio in Colombia has reported an increase in the movement rate in the landslide at the Hidroituango dam site, breaching the alarm threshold of 10 mm per hour.  This has triggered evacuation of 45 workers at a part of the dam site… I think this means that they are concerned that: 1. Failure of the rockmass in the abutment (i.e. the landslide) could destroy the dam directly; 2. the landslide could trigger a wave that overtops the dam; and 3. the dam might fail because of seepage. If so then this is a project is in deep, long term trouble.  The lake level is currently rising at 70 cm per day, with the current level at 393 metres.  The spillway is at 401 metres, so the lake level has to increase by another 8 metres yet.  The groundwater will rise as the lake level comes up, with some lag, so the stability of the slopes will continue to decrease… Meanwhile, the two leaks at the foot of the dam are releasing 18 litres per second and 11 litres per second respectively.” It is unclear what is the source of this leak water.

On June 6, 2018 Petley[xiii] wrote: “In the last 24 hours, the behavior of the mountain on the right bank of the reservoir has been stable [I think this means stable sliding – i.e. no change in behaviour.  It is certainly not stable from a slope stability perspective]. According to the data of the interferometric radar  have presented some slides of surface material that reach Speeds less than 10 millimeters per hour, i.e. below the alarm threshold… This situation was described yesterday as being “highly critical” by Jorge Londoño De la Cuesta, manager of EPM… The most interesting development though is a set of suggestions that the site could be affected by much larger landslides.  For example, El Colombiano has a report online that appears to imply that an American report – presumably the report by the US Army Corps of Engineers? – indicated that the maximum volume of a landslide at the site could be between 10 and 40 million cubic metres.  That would be an exceptionally large landslide – this is the realm of the high mobility (i.e. rapid) rock slide (although high mobility is not inevitable even at this volume), which could be very dangerous indeed.”

On June 11, 2018 Petley[xiv] wrote: “Meanwhile, small landslides continue to occur, and I assume the main slip is continuing to move… This image (of June  10) is interesting in that it appears to show a series of new, shallow slips higher up the slope, some of which are not directly connected to the main slides.  Presumably this is an indication of continued increases in groundwater level.  One of these caused the evacuation of some workers on Sunday morning, although it seems to have been managed within agreed protocols.  Note also how close the lake level is to the spillway.  The water is now testing the rapidly emplaced fill at the crest of the dam; this is the material that has been reported to be below standard in terms of compaction.”

USA based CIEL (Centre for International Environmental Law)[xv] has supported the local communities’ complaint to the funder of the dam, the Inter American Development Bank’s accountability mechanism for violations of social and environmental norms in funding the Hidroituango Dam in Colombia by IADB.

On June 12 2018, Guardian reported[xvi]: “If that (breach of Hidroituango Dam) happens, or should water cascade over its wall – both risks that the United Nations Environment Programme has highlighted – the consequences could be catastrophic both for those living nearby – and for EPM, the state-owned company behind the project.”

“Our main concern is getting through this alive,” Isabel Zuleta, a vocal Ríos Vivos activist was quoted as saying by the Guardian. Its very uncertain how many will achieve that.

Compiled by SANDRP (ht.sandrp@gmail.com)

END NOTES:

[i]  https://www.theguardian.com/world/2018/may/16/colombia-tens-of-thousands-of-ordered-to-evacuate-after-floods-at-dam

[ii] https://blogs.agu.org/landslideblog/2018/05/21/hidroituango-1/

[iii] https://blogs.agu.org/landslideblog/2018/05/21/hidroituango-crisis-2/

[iv] https://blogs.agu.org/landslideblog/2018/05/23/hidroituango-dam-site-3/

[v] https://blogs.agu.org/landslideblog/2018/05/28/ituango-dam-site-4/

[vi] One reader though differed: “it is not a landslide per se, it is some kind of tunnel or cavity collapse…”

[vii] Video of the landslide: https://youtu.be/Z6uV32LNv5M

[viii] There was reference to twitter images: https://twitter.com/Diario_sigloxxi/status/1001855747288776704

[ix] https://www.hydroworld.com/articles/2018/05/ituango-situation-leads-epm-to-cancel-planned-gas-acquisition.html

[x] https://blogs.agu.org/landslideblog/2018/06/03/hidroituango-crisis-6/

[xi] https://blogs.agu.org/landslideblog/2018/06/04/hidroituango-6/

[xii] https://blogs.agu.org/landslideblog/2018/06/05/hidroituango-7/

[xiii] https://blogs.agu.org/landslideblog/2018/06/06/hidroituango-8/

[xiv] https://blogs.agu.org/landslideblog/2018/06/11/hidroituango-9/

[xv] http://www.ciel.org/project-update/ituango-hydroelectric-project-drowning-transitional-justice-in-colombia/

[xvi] https://www.theguardian.com/world/2018/jun/12/colombia-river-cauca-breach-flooding-farc