Underground Dubrovnik hydroplant too good to be true?

15/01/2013

Environmentalists are worried about a plan to build a hydroplant underground.

By Cornelis van Zweeden for the Southeast European Times in Dubrovnik -- 15/01/13

The Western Balkans has more limestone mountains than any other region in the world. Croatia’s mountains are famous for their ski trails. [AFP]

It seems almost too good to be true: an underground hydroplant. And so it is, said Jagoda Munic of the environmental organisation Green Action in Croatia: "This project is insane."

The idea was first dreamt up under communism. The Western Balkans has more limestone mountains than any other region in the world. In spring, when the snow melts, ponds and lakes emerge throughout the country. Then, come May, it is as if an invisible hand pulls the plug. The water disappears, feeding into underground streams and rivers.

Often, these rivers surface very close to the sea. This makes it impossible to build traditional hydropower plants. So why not construct them underground?

The Ombla hydro-plant near Dubrovnik is set to become a test case, if the proponents of the project can get beyond the hurdle of an environmental impact study.

"The potential for underground electricity generation in the Balkans is huge," Davorin Kolic, representative of the Croatian Association for Tunnels and Underground Structures, told SETimes. "Greece and Turkey also have large underground water reservoirs."

Kolic emphasised that thorough research is required to identify the feasibility of an underground plant in a particular area. In Dubrovnik that geological research started three decades ago, he said.

Jagoda Munic of Green Action said something else is needed too: a thorough environmental impact study. Together with other Croatian NGOs she lodged a complaint with the European Bank for Reconstruction and Development, which is financing the project for 123 million euros, 80 percent of the total costs.

Munic said that even traditional hydroplants can damage the environment, let alone an underground one.

"We don't know what will happen if you construct a dam in a cave," she told SETimes. "The water pressure behind it will build up, and new cracks can emerge in different places. A very small but similar project in Bosnia caused a landslide in the cave."

Looming large is the issue of the biodiversity. More than 40 percent of Croatia rests on porous limestone, where water has created so many caves that it is virtually impossible to dig a tunnel without hitting one. These caves are home to species that do not exist anywhere in the world, such as an eel-like salamander that has legs but no eyes.

"Other countries might have rich fauna in rainforests, but in this area we have the best range of cave fauna in the world," Jana Bedek, a biospeleologist, told the BBC.

Yet, the proponents of the project say the project will not endanger life in the cave. The 3.5-kilometre long, 395-metre high dam already exists, ITA President Zvonomir Sever said. Due to tectonic shocks, however, cracks have opened up in the otherwise impenetrable dolomite barrier.

"We will only close these cracks," he said.

Munic said that process will also damage a protected landscape. "They will make an access road to the top of the mountain, drill a hole every 3 meters and fill it with concrete."

Once the dolomite barrier has been made watertight, the water level behind it will start to rise and fill a huge "sponge" of cracks and smaller caves behind it. The water will be channeled into the turbines through a vertical shaft, all of which will be hidden in the cave, proponents said.

Officials present the future plant also as economically sound.

"It is cheaper to repair an existing barrier than to build a new one," Sever said.

This content was commissioned for SETimes.com.