Investinženjering d.o.o. in association with Nivelir d.o.o. signed a contract with Hrvatske autoceste d.o.o. for technical and financial supervision services over works which include: energy supply, installation and equipment works, as well as construction of service buildings on Zagvozd – Baška voda connection road (with Sveti Ilija tunnel through Biokovo). Construction of Zagvozd – Baška Voda connection road and St. Ilija tunnel will provide a high-quality road connection between Zagreb – Dubrovnik motorway and part of the Adriatic coast so-called “Makarska riviera”. The total length of the tunnel and pertaining north and south connection roads is 9,2 km. As part of Zagvozd – Baška Voda connection road the following will be constructed: St. Ilija tunnel with a total length of 4.250 m, more than 4 km of access roads, overpass St. Križ and two underpasses of the alignment and a grade-separated intersection on the Adriatic tourist road. St. Ilija tunnel is the main object with a total length of 4.250 m. The tunnel will have two separated tunnel pipes primary and secondary. The primary pipe will be used for regular traffic with two traffic lanes. The secondary pipe will be used for rescue and evacuation needs. A tunnel will be constructed with a constant three percent slope decrease from north to south. Due to the overburden height of over 1.300 m, the tunnel represented a special challenge for all who worked on its breakthrough.