EPM Making More Progress in Recovering Hidroituango Project

EPM general manager Jorge Londoño de la Cuesta revealed in a July 11 press conference that engineers are making more progress in recovering the US$5 billion, 2.4-gigawatt “Hidroituango” hydroelectric dam project in Antioquia in the wake of a temporary emergency caused by a geological fault and a diversion-tunnel failure last May.

Thanks to falling water levels in the Cauca river – the result of the typical Colombia summer-dry-season starting in July – waters behind the dam have dropped to 380 meters above sea level, down nearly 14 meters from a peak in June. This will help accelerate engineering work and recovery efforts.

“According to hydrological forecasts, it is estimated that the reservoir will stabilize between elevations 370 meters above sea level and 375 meters above sea level” during the summer season, according to EPM.

Meanwhile, some relatively minor landslides above the intake gates for the tunnels leading to the machine room (where the generator turbines eventually will be located) prompted EPM to begin building a metallic-roof structure that will protect workers, machinery and equipment at the site, Londoño explained.

In that area, workers soon will install closure gates for the tunnels — hence enabling EPM to enter and repair whatever damage might be found in the machine room powerhouse, which has been used temporarily to evacuate Cauca river water because of the diversion-tunnel failure last May.

“Once we complete the civil works and install the gates of [machine-room entry tunnels] 1 and 2, in about a month, we will be able to to close the flow of water through the powerhouse,” according to EPM.

Meanwhile, last Friday (July 6), EPM radar monitors detected a rock fall in a road tunnel leading to the machine house, “which caused a slight decrease in the flow of water through the discharge tunnels,” although subsequent flows are now stable, according to the company.

“For the closure of the powerhouse, the company is working on a plan that includes closing a [Cauca River water] catchment gate and leaving a second gate open to allow [a required minimum] ecological flow to the Cauca River [downstream of the dam]. When the level of the reservoir [behind the dam] is very close to reaching the height of the engineered spillway at 401 meters above sea level, this second gate will be closed and the water flow through the machine house will be interrupted,” thus enabling EPM workers to enter and begin repairs — hopefully before year-end 2018, Londoño added.

With both the diversion tunnel and the machine-house tunnels closed, that means that Cauca River waters will instead flow safely over the engineered spillway, avoiding water-flooding in tunnels.

Meanwhile, EPM continues works to raise the dam to 418 meters above sea level over the next few weeks, after which a specialist contractor — Soletanche Bachy Cimas — will begin injecting a special type of concrete (bentonite and cement) inside the dam, further reinforcing the works, he explained.

This reinforcement work is likely to be completed by year-end 2018 or the first few weeks of 2019, hence ensuring that the dam can withstand any floods that theoretically might happen once every 500 years, Londoño explained. Dam construction nevertheless will continue to 435 meters above sea level — virtually eliminating any possible dam-overtopping by some theoretical, Biblical-style flood.

“For the definitive plugging of the right diversion tunnel and the auxiliary diversion system, EPM and the CCC Ituango construction consortium are advancing in technical and economic negotiations with [Houston-based] Halliburton, specialized in drilling for the oil industry,” EPM added. “This company will finalize in the next weeks the engineering design to proceed with the contracting and execution phases,” according to EPM.

Final closure of that diversion tunnel is estimated to be completed around October, Londoño added.

As for EPM’s concurrent social work to help downstream populations in Puerto Valdivia — temporarily moved to shelters far-above the river’s edge during the emergency — “of the 1,640 families that can receive financial support from EPM to temporarily rent a home and pay their monthly maintenance, 929 families already obtained this support and another 711 families are in the process of being processed. EPM has provided all the resources so that the evacuees have comprehensive attention in the current circumstances,” the company added.