Seven-metre high walls are being built in the Danube riverbed at the tip of Csepel Island

In the complex project of the Colas Alterra Zrt. and STRABAG Generálépítő Kft. consortium's complex project, the construction of the suction side structures is being carried out using the MEVA formwork system.

One of the oldest and most complex water engineering structures in Hungary, the Kvassay water pipeline, is located on the northern part of Csepel Island.

In 1911, the navigation lock was opened to traffic, followed by the construction of a pumping station and a hydroelectric power station on the Ráckeve-Soroksár branch of the Danube. Because of its complexity, it is often called the Lord of the Danube. The Kvassay sluice is the first line of flood protection for the Budapest-Baja flood protection basin.

During periods of drought, the structure ensures controlled water levels in the Ráckeve-Soroksár branch of the Danube. If the water level of the Great Danube is too low, i.e. not enough water can flow through due to gravity, the power plant also acts as a pump to feed the Soroksári-Duna. This branch supplies water to the fish ponds and irrigation systems of the Danube Valley.

The structure also has a key role in regulating water quality. It would be an ecological disaster if there were not enough fresh water in the Danube tributary, as the water treated by the South Pest wastewater treatment plant flows into the river here. Without proper dilution, the nutrient content of the water in the river branch would be very high, causing significant ecological damage. The Kvassay sluice and its surroundings are a popular destination for water hikers and anglers.

Climate change has also forced the renovation of the hydropower plant

In order to ensure safe water level control on the Danube, the National Water Authority has invested in the Colas Alterra Zrt. and STRABAG Generálépítő Kft. consortium began the complex renovation of the Kvassay water barrage in January 2022 as part of a major project, which includes

• the turbines and craneways of the power plant will be refurbished,
• a new pumping station with suction and discharge works and piping,
• modernise the energy system of the power plant building,
• renovation of the listed sluice building and the service dwelling near the complex, as well as the beam storage,
• and the sedimentation system will be modernised.

The first half of the project is already complete

So far, the construction phase has already completed, among others, the new pumping station's penstock upstream of the Ráckeveei-Soroksári-Duna branch and the associated estuary structure. The energy and electrical systems of the power plant building have been modernised and the turbines have been refurbished.

Currently, the construction of the shaft structure and the reinforced concrete structure of the forebottom is underway on the suction side. For this purpose, the work area has been delimited in the river bed using reed plates and water has been pumped out. The main suction-side structure is being built within the 150-metre long and 7-metre wide service.

Formwork started at a depth of ten metres

Horizont Invest Szerkezet Kft. also played a role in the implementation of the project, and the company's experts used MEVA Zsalurendszerek Zrt. formwork to construct the structure in the riverbed to a wall height of more than seven metres.

The reinforced concrete structure for the concrete forebottom is being built on the site, and will supply water to the four pumps.

Gábor Kecskeméti, the sales engineer of MEVA, told us that the construction of the formwork started in July, and then the first elements of the structure were concreted in two phases. In order to achieve dimensional and shape accuracy, the individual wall endings were not made on site. The specialist added,

Prior to formwork, 3D formwork and product designs were prepared in order to construct the formwork as accurately and quickly as possible, even around pre-installed fittings and in unusual geometric shapes.

Day and night construction work

Due to the tight construction schedule, work at the water power plant is being carried out in two shifts, day and night. This is one of the reasons why Mammut products from MEVA for large-panel formwork were used on the structure, which can cut formwork times by up to 30 percent.

The elements can be assembled in three different ways, using just one tool. The design of the MEVA Mammut makes it suitable for use in spectacular concrete surfaces.

Heatwave, then flooding makes work difficult

The challenge of the project is that the work has to be carried out 10 metres below the level of the flood protection slit wall, in the riverbed," said Gábor Kecskeméti. The extreme heat in the summer also made the construction difficult, although they tried to take advantage of this in the concreting work, as the curing times could be shortened.

Flooding is already causing problems in the autumn season. The work area had to be flooded due to the flood wave. After the flood recedes, damage control preparations must be made and the layer of mud must be removed from the work area before work can continue.