Underground complex "Zaramagskiye HPPs"

The project construction started in 1991. The underground complex of the Zaramagskiye HPPs located on the Ardon river in the Alagir Region of the North Ossetia-Alania Republic includes:

• Derivation pressure tunnel # 1. This tunnel is 678 m long. It is constructed for water supply from the intake structure to the turbines of the head HPP. The tunnel cross section without lining ranges from 32 m² to 240 m².
• Tunnel for diverting the Ardon river flow from the head HPP facilities and the dam during construction period and for removal of flood water when storage reservoir gets completely full during operational period. The tunnel length is 600 m. The tunnel cross section is circular with a diameter of 5 meters. The tunnel was commissioned in December 2000.

• Penstock consists of a slightly declined part - 974 meters long (two lines) that is connected with the vertical shaft – 510 meters deep. The penstock is constructed for water supply from the daily pondage basin to the turbines of the HPP-1.
• Derivation tunnel # 2. This tunnel is 14 822 m long. Its cross section without lining is 27,7 m² , with lining – 21 m². The tunnel is constructed for water supply from the diverter system of the head HPP to the daily pondage basin of the HPP-1. Excavation of the derivation tunnels was performed using continuous face method, but in very weak zones with fkp. 0,8 -1,5 - benching method was applied where cement injection was performed in advance.

At present, the derivation tunnel #2 is being excavated and the permanent lining is being assembled there. Excavation is being performed using drill and blast method.