Works on the Sió Canal and major works - Colas Alterra
Works on the Sió Canal and major works

2024. 02. 15..

The final touches have been put to the Lake Balaton drainage system, with several weirs and sluices being renewed, but the work is far from over.


About the project in general

On 19 September 2019, our contract entered into force, marking the start of the Lake Balaton Drainage Modernisation Project, which not only renewed the Siófok Drainage Lock and Ship Lock and the Balatonkiliti Dam, but also almost the entire length of the Sió Canal and the Bogyiszlo Lock.

The structures are suitable for min. 100m3/s, thus allowing the water level of Lake Balaton to be raised, thus increasing the capacity of the storage network, which can serve as a reserve in dry seasons.


Balatonkiliti dam

The Balatonkiliti embankment dam was built downstream of the old dam at the 118+030 river kilometre section. The structure has two openings, of which the 8.0m opening is for controlled water release and the 12.0m opening is for navigation. Due to the drained Sió Canal, it was possible to build the lock in practically dry conditions.

The embankment dam was built using around 2,400 m3 of concrete, the openings are steel-framed shut-offs with a tilting-plate design.

Following the construction of the new structure, the demolition of the old sluice was started, starting with the dismantling of the steel structures. It was then discovered that DRV’s DN300 penstock crosses the Sió right at the site. After replacing these pipes, the old weir was dismantled down to the base plate.


Discharge and navigation lock

The old boat lock was built sometime between 1941 and 1947, so it was time to modernise it. The purpose of the navigation lock is to ensure the passage between Lake Balaton and the Sió Canal.

As in the case of the Balatonkiliti structure, the construction started with the delimitation of the working area with reed plates. Due to the proximity of Lake Balaton and the continuous infiltration of groundwater, the work area had to be secured with open water. Approximately 7500m3 of structural concrete was used for the construction. The main closure is provided by a retaining gate on the upstream deck and a steel-framed segmental slab on the downstream deck. The width of both is 12m.  The structure underwent its first real test in July 2023, when two new BAHART catamarans and two new BAHART ferries arrived at Lake Balaton on 3 July 2023.

Work on the outlet sluice also started with the demarcation of the working area with reed plates and the construction of the open water drainage. The sluice gate will be operationally closed to ensure a constant water level in Lake Balaton. It will consist of two 8-metre wide sluices, which can be operated separately or, for maintenance, it will be possible to close only one of the sluices. The construction of the outlet sluice required 1400m3 of structural concrete.  In addition to the construction of the structure, the old sluice was dismantled and the final riverbed condition was created. After the placement of the precast concrete and the associated precast elements next to the structure, on 27 October 2023, we started to retrieve the reed plates that had been dropped into Lake Balaton, thus giving the structure its final shape. The arched bridge that will allow vehicular access to the BAHART plant was constructed at the entrance to the outlet sluice.

All three structures are operated from the Operations and Services Building.

The structures, together with other associated construction elements such as road construction and landscaping, were completed by the contractual deadline.


Reconstruction of the Sió Canal

In addition to the construction of major works, the reconstruction of the Sió Canal was also part of the project. The aim was to improve the water permeability of the channel to allow the water flow (up to 80 m3/s) to be safely maintained in the large waterway and to prevent further rutting while increasing the safety of navigation.

The dredging and construction works were carried out from Siófok to the Kapos estuary (120+854 fkm – 79+477 fkm). A mechanical stabilisation was constructed on top of the depots, thus ensuring that KDTVIZIG could approach the sluice structures used for flood protection measures at any time.

At the same time, we completed the first phase of the left bank embankment relocation and related dredging works in Kölesden. This intervention on this stretch of the Sió was justified by the need to dewater the embankment on the waterside of the flood protection embankment. The first phase was completed in November 2021.

The contract was amended in the meantime to allow the second phase of the embankment relocation to start in spring 2022. The start of construction was hampered by land acquisition obstacles. The works were completed at the end of 2022.

After the completion of the embankment relocation, the wetland creation started in late 2022 – early 2023, but again there were problems with land acquisition procedures. Due to the protracted issues, it was also necessary to submit an Amendment 3 to the contract, which changed the end date of the project to 15 November 2023 and included the necessary material and technical changes to the content. Finally, this part of the work was fully completed in October 2023.


Text: Antal Harangozó
Photo: László Regőczy

Colas Hungária