During the night of October 24–25, 2025, the final breakthrough of the tunnel was achieved between the excavation points 6 and 1, at chainage 0+508.5. This event, which is of great engineering importance, marked the completion of underground excavation works for the tunnel of a total length of 12,125 meters.
The excavation of a tunnel of such great length is a civil engineering achievement worthy of attention and respect in a broader sense. This tunnel is the longest of its kind in the Western Balkans and the second longest in Southeastern Europe.
It should be noted that this tunnel, which passes through two distinct geological formations, will convey water from the Nevesinje reservoir to the Dabar Hydroelectric Power Plant. The tunnel’s intake structure is located along the Zavidolska River, and it continues into a penstock that will carry the water to the powerhouse.
Main characteristics of the headrace tunnel for the future HPP Dabar:
- Length: 12,215.00 m
- Elevation at tunnel entrance: 813.00 m
- Elevation at tunnel exit: 787.06 m
- Longitudinal slope: 2.139‰
- Circular cross-section, clear diameter: 4.6 m (at length of 7,853.00 m)
- Horseshoe-shaped cross-section, excavation height: 5.20 m (at length of 4,272.00 m)
- Constructed using the New Austrian Tunneling Method (NATM).
In order to accomplish excavation of this tunnel, the work was carried out at a total of six excavation points, operating in two to three shifts, engaging 200–250 workers during various construction phases. Approximately 500,000 m³ of material was excavated and about 150,000 m³ of concrete was cast, all using the specialized construction machinery.
Although achieving the breakthrough of the tunnel is a significant milestone, substantial work and challenges remain before project completion, particularly concerning stable financing. The remaining tasks include:
- Construction of 1,948 m of the tunnel secondary concrete lining;
- Construction of 260 m of tunnel using the “cut-and-cover” method;
- Installation and commissioning of mechanical equipment at the intake structure;
- Construction of a concrete plug at the junction of the Straževica access tunnel and the headrace tunnel;
- Construction of the pavement structure of the access road to the intake structure;
- Execution of final and rehabilitation works.
