28 May 2018
Another landslide at the Ituango dam site in Colombia
Posted by Dave Petley
Another landslide at the Ituango dam site in Colombia
On 26th May 2018 a further landslide occurred at the Ituango dam site (Hidroituango) in Colombia. The slope failure led to the evacuation of the 1500 workers at the site. There were no injuries and the integrity of the dam does not seem to be threatened. The best report that I can find is in El Espectador (in Spanish of course), a translated version of which is as follows:-
Empresas Públicas de Medellín (EPM) reported that a new landslide occurred on the afternoon of this Saturday in the Ituango hydroelectric project, which has been on alert since April 28. The company reported that, due to the fact, the 1,500 workers who were working on the project were evacuated. EPM also informed that there were no workers injured as a result of the incident and that at this moment the necessary technical evaluations are being done to know when they can resume work on the project. 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.
Images of the landslide suggest that it was much smaller than the earlier event, and occurred on a slope above the area that had been cut. Juliana Ramirez tweeted an image of the landslide:-
The landslide was also caught on a video that has been posted to Youtube by Noticias Caracol:
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. I am sure that will be a major theme as the dam is commissioned. In the short-term EPM are doing the right things in maintaining the evacuations, strengthening the crest of the dam and monitoring the slopes.
Below is a link to an article that is on the HydroWorld website:
Dave, as you can see in the photo it is not a landslide per se, it is some kind of tunnel or cavity collapse…
Hi Dave, 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. It sounds like there is serious concern about the whole stability of the hill adjacent to the dam. My reading of the faults shown in the images is that when it fails it could impact the spillway structure and possibly the intake for the powerhouse (possibly the powerhouse itself) but it does not look like the entire hill side will fail from what I’ve seen so far. See twitter for multiple images of the cracks (Some on the hillside near the power lines, another on a surface road and some from within the tunnels – Search for ‘Hidroituango’). It’s annoying how hard it is to find good technical info on the extent of the faults (especially in English from the UK)!
I’ve also seen concerns expressed that they can’t control the flow of water through the powerhouse and possible impacts this will be having on it, the tunnels and the structures around it long term. As mentioned by Jan in an earlier comment, it was apparently a partial blockage in the powerhouse that sent water down the access tunnel to the foot of the dam. I’ve not heard how they were able to bring that under control. The successive landslides also sound like those progressive failures you often talk about. I’d be interested in your thoughts on the robustness of the hillside and how they might recover from the current situation, especially if they are unable to control of the water flows.
ps, I’m just an amateur observer trying to follow the heroic effort to fix this on social media. The above is my best interpretation of what I’ve seen to date.
I though I should find you some links to save you searching…
This articular has a good summary with images from in the tunnels… https://www.semana.com/nacion/articulo/hidroituango-otra-vez-alerta-maxima-para-las-comunidades/569313
Here’s some of the hillside cracks… https://twitter.com/mabelgasca/status/1001864636663320577 and… https://twitter.com/Diario_sigloxxi/status/1001855747288776704
More images of the hill and crack in the road… https://twitter.com/TotoSerrath/status/1001815620109946880
This shows the intake to the powerhouse below the cracks… https://twitter.com/DiarioLaPiragua/status/1001846883017469957
A nice wide angle view of the area affected… https://twitter.com/infirmieredouce/status/1001828207509811200
I just realised that there is another likely risk that the volume of material currently in motion (based on the cracks) will probably be significant enough, and close enough, that the wave/displacement generated from it entering the reservoir will over-top the dam 🙁
Another thought was that in the event of a significant failure of the dam, the sudden release of water will likely results in the waterlogged banks slumping and causing large landslides along the length of the reservoir behind the dam as the water drains. I imagine this will cause significant problems upstream in addition to the obvious issues down stream. Are their any examples from the past of such secondary risks following a failure that the planners should be considering?
Here is a good satellite time-lapse of the reservoir filling… https://twitter.com/Pierre_Markuse/status/1000050310516232194
This article has a good wide image of the dam and the hill that’s been having all the cracking issues and which contains all the tunnelling and powerhouse… http://www.valoraanalitik.com/2018/05/30/creditos-para-hidroituango-estan-cubiertos-con-polizas-de-seguro/
This article has a wide image of the dam and hillside that having the cracking issues. I think this will be from a few days ago but will help you judge the overall topography… http://www.valoraanalitik.com/2018/05/30/creditos-para-hidroituango-estan-cubiertos-con-polizas-de-seguro/
Hi, Another photo this time showing what I assume is the powerhouse intake just below the hillside cracks (may be secondary intake as this is quite high up the dam?). Note the ledge where the future landslide debris is likely to land… https://twitter.com/masverdeperiodi/status/1002550340682592256
Another “Expected [landslide] in Hidroituango would be 130,000 cubic meters of Earth” … https://twitter.com/opinionpublick/status/1002549820794527744
One more… “Cauca River would begin to pass through the [spillway] of Hidroituango in five days” … https://twitter.com/BluRadioCo/status/1002544955179569153
and finally for now… “At this time HidroItuango workers finish emptying the last slab of the landfill. They have to finish details of the wall that goes against the mountain and proof of waterproofing” … https://twitter.com/gaboperiodista1/status/1002552953314607104
I hope this details are of use for you 🙂
Best details I’ve see on the locations of tunnels within the hillside… https://twitter.com/aposadao/status/1002884560999378944
There are reports of water coming out from bellow the dam: https://noticias.caracoltv.com/hidroituango-en-emergencia/denuncian-filtracion-de-agua-en-la-presa-de-hidroituango-ie137