The metro tunnel, which connects MS 6 on Madrid Boulevard with MS 5 on Vladimir Vazov Blvd. at Chavdar Bridge was broken through. The tunnel has a length of 675 meters and a cross-section of 63 square meters, and it includes a ventilation shaft with size of 26 per 20 meters.

It passes under Danail Nikolaev Blvd., existing railway infrastructure of Stochna gara (railstation) and the Sofia - Burgas line with six active tracks, and less than three meters under the Perlovska River. The drilling and strengthening of the tunnel was a tremendous challenge, as it underwent an extremely heavy geology - blue water, sand and other similar geological structures. 

This is indeed one of the toughest of over 130 kilometers of tunnels, that Euro Alliance Tunnels has built over the past nearly thirty years. The construction of the tunnel demanded the entire expertise of the Euro Alliance Tunnels´ team to apply the New Austrian Tunneling Method - the only way this tunneling project could be realized.