The implementation of the project began officially in September 2008, eight months after Bulgaria's former Socialist-led ruling coalition signed an agreement on it during then-Russian President Vladimir Putin's visit to Sofia.
Implementacija projekta počela je zvanično u septembru 2008, osam meseci nakon što je bugarska bivša vladajuća koalicija na čelu sa socijalistima potpisala sporazum o tome tokom posete tada predsednika Rusije Vladimira Putina Sofiji.