Tough excavation for clean energy in Georgia 25 May 2017

Georgia Prime Minister Giorgi Kvirikashvili at project start up

Lok Home, Giorgi Kvirikashvili, and project officials press button to start up the Dariali hydropower station

The Dariali Hydropower Project in the Republic of Georgia is the first carbon neutral hydropower project in the world and was commissioned in April 2017 with a ceremony attended by Georgia Prime Minister, Giorgi Kvirikashvili. The power station is an independent power project developed through a joint venture by Dariali Energy Ltd with Georgia private companies Peri Ltd and Energy LLC, and state-owned Georgian Energy Development Fund (GEDF).

The Dariali hydro plant gathers water from the Tergi River and directs it through the headrace tunnel to the power house located near the Russian—Georgian border. Each year, the site will generate 500 GWhs of carbon-neutral energy, with 70% of power production occurring during the country’s summer months.

The 5km long headrace tunnel for the power station was bored with a 5.5m diameter Robbins main beam TBM which started work in February 2012. Robbins was also given equity for its involvement in the project as a consortium partner with contractor Peri. “Robbins understood the risk in the tunneling portion of the project and we were compensated for taking on part of the risk. Peri is a long-time customer, as we supplied a TBM to them 15 years ago for a small project in Georgia. It was great to be invited to invest and risk share on this project, and to work together again,” said Robbins President Lok Home.

Due to the remote and mountainous location of the jobsite, 160km from the capital Tbilisi, the machine was shipped in pieces to the Peri workshop and refurbished under Robbins supervision ahead of delivery to the site for assembly. Each piece was transported by truck down narrow, winding roads and dirt paths. Assembly at the jobsite was difficult, as the project site at a 1,700m altitude was covered in snow when components arrived in December. Temperatures often reached -15°C, and -40°C with the wind chill factor. Once the machine had launched, it encountered difficult ground including slate, sandstone, limestone and malms with fault zones.

Robbins 5.5m diameter TBM completed the 5km headrace

“The main challenges we faced were boring the tunnel at a 6% incline and having restricted access to service the machine. There were also two major landslides that delayed the project for more than a year,” said Home. After the first landslide, the access tunnel, which had allowed mud and water to enter the power station, had to be relocated at a higher elevation and facing away from the river valley. When the machine was nearing the end of its drive, a second landslide blocked the exit portal for the machine as well as access to the main highway. Despite these challenges, tunneling crews persevered and the machine successfully broke through in October 2014.

Throughout the construction process, careful steps were taken to minimize the carbon footprint. Although the plant’s energy production is carbon emission free, construction of the plant was not. To offset these emissions, 7,000 seedlings are being planted around the area in a reforestation effort. In years to come, the trees will absorb enough carbon dioxide to compensate for the emissions produced during the construction of the hydropower plant.

“Overall there is much to celebrate as the project has immense benefits. Not only does it provide affordable electrical power for the country, with essentially no pollution, but it also provided jobs during construction and will continue providing jobs during its operation and maintenance,” said Home.