On the 6th of February 2013, Stroyinject JSC as a subconstructor of "Metro Drujba" Ltd, started work for construction of tunnel section from Metro station 20 (КМ. 3+184.90) to Metro station 21 (КМ. 4+324.20) , part of the "Project for expansion of the Sofia metro, Stage 2 - First metro diameter", Section Blvd. "Tsarigradsko shousse"/MS 19/ - Qr. "Drujba-Sofia Airport"/MS 23/.
The tunnel section is going to be reinforced with Sheet retaining walls.
