Bulgaria has commissioned the third of four modernized compressor stations, which is transiting 85% of natural gas to the country’s neighbours, the Energy Ministry announced on Monday.

State-owned gas grid operator Bulgartransgas has put into operation the key Strandzha compressor station following investment of BGN 70 M, the ministry said in a statement.

The compressor station near the city of Burgas, in southeastern Bulgaria, is used currently to transit 14 billion cubic meters of gas a year to Istanbul, Turkey, Prime Minister Boyko Borisov told the commissioning ceremony, according to the statement.

The volume is 85% of total gas transit via Bulgaria’s territory, Energy Minister Temenuzhka Petkova added.

Total investment in the upgrade of the four compressor stations (Ihtiman, Lozenets, Strandzha and Petrich) exceeds BGN 200 M.

Works on Ihtiman and Lozenetz compressor stations have already been completed.

The last of the four upgraded stations, in Petrich close to the borders with Macedonia and Greece, is expected to be put into operation in the middle of the year.

The project for the upgrade of the four stations by means of integrating low emission gas turbine compressor units is funded by Bulgartransgas.

Construction works are being implemented by Bulgaria’s Glavbolgarstroy. U.S.-based Solar Turbines Incorporated, a subsidiary of Caterpillar Inc., is supplying the equipment.

The modernization brings the four compressor stations in compliance with the European environmental requirements and increases their operational safety.