Ashta hydropower station

The Ashta hydropower station is located on the Drin river close to Shkoder, the fourth-largest city in Albania. ENERGJI ASHTA Shpk, a project company belonging to the Austrian power providers VERBUND and EVN had contracted the project. Ashta forms the last power station in a whole range of existing power stations in the north of Albania. It utilises the drop height between the Spathara reservoir lake which is fed by the Drin river and the point where it flows into the Buna river. Consisting of two facilities and a 5 km connection canal, the power station produces a total of 55 MW of electricity by means of 90 matrix turbines. In the course of this project, PORR moved more than 3 million m³ of earth and installed some 100,000 m³ of concrete.

The construction pit presented a great technical challenge. Various civil engineering methods defined by international standards were required to tackle the difficult geological conditions in close vicinity of the Drin river: the groundwater table is located only slightly below ground level and the power station’s floor is almost 10 m below. The subsoil’s extreme permeability and the special local soil conditions required a technically demanding solution.

First, the bored piles on which the power station structure is founded were manufactured. Similar to a protective shield, a steel-reinforced concrete diaphragm wall was inserted into the ground and anchored. 

The construction pit between the diaphragm wall was excavated like a large bathtub using backhoe excavators. Subsequently, a 1.5 m thick underwater concrete floor was laid by professional divers 10 m below the surface. To prevent the water pressure from lifting it to the top, it needed to be pushed down using GEWI piles.

Only once this had been done, the water could be pumped out of the construction pit without causing technical problems. All these civil engineering measures were necessary before starting the actual concrete work on the power station structure.

Not least thanks to excellent cooperation between owner, planners and construction company, this difficult construction project could be successfully completed in a short time and at high quality.