Digging of the Vistula Spit: Installation of the first gate to the “heart” of the investment

In September, the assembly of the first lock gate at the construction site of the Vistula Spit Canal began. It is one of the largest structures of this type in Poland. The gates will prevent the mixing of the waters of both reservoirs.

“The ongoing investment will not affect the salinity of the Vistula Lagoon. This is due to the technology used to build the shipping canal, which prevents uncontrolled mixing of waters and the sequence of works – first the lock, and then the dredging works in the northern and southern parts of the canal. Also during the operation, after the shipping canal is put into use, there will be no free mixing of waters between the Gdańsk Bay and the Vistula Lagoon. The differences in the water level between the reservoirs will be levelled out within the lock, which will open only during the passage of vessels,” says Andrzej Małkiewicz, head of the Investment Implementation Department at the Maritime Office in Gdynia, the investor of the entire project. “This will ensure that both salinity and water dynamics do not change outside the immediate vicinity of the canal. The local nature of the investment’s impact in this area has been confirmed by model studies included in the environmental impact report,” adds Andrzej Małkiewicz.”

In order to assemble the lock gates, each of them has been divided into six elements. Each item is shipped separately. First, it is welded in a prefabrication plant, then a trial assembly of all six segments takes place. Then, they are split again and transported to the area of the lock, where they will be built in.

“We have just started works related to the assembly of the steel structure of the first of the four gates. One gate is about 160 tonnes of steel structure,” says Paweł Ciomek, Bridge Works Manager from the NDI/BESIX consortium, the General Contractor of the investment. “We installed the lower truck, thanks to which we could start work related to the assembly and integration of the lock gate. After the components are connected, the upper truck will be mounted. Both trucks will allow the gate to move in the direction transverse to the lock. Thanks to this, it will be possible to close it after a ship enters it.”

The planned deadline for the construction of the lock is the first quarter of 2022. Then, it will be flooded with water and all tests of tightness and mobility of the gates will be carried out.

Dry-concreted basin

The heart of the investment is the tight lock basin. It is a chamber 230 metres long, 25 metres wide, 6.5 metres deep to the water surface and 2.5 metres above the water surface.

“We are in the final stage of the construction of the southern pocket. We will soon finish the culvert. At the end of September, we will begin the construction of the last element of the southern pocket – the drive house building, a facility which will house all the hydraulics and automation responsible for the movement of both gates,” said Mariusz Janczewski, Deputy Project Director – NDI/Besix consortium. “Reinforced concrete works related to the construction of the main lock’s enclosure walls are also well advanced. We have also started the construction of a cap, which is the final finishing element of the entire gate structure, on which the hydrotechnical equipment will be installed.”

As specialists emphasise, such an accurate and quality execution of this object is possible thanks to the selection of a specific technology of work.

“The contractor decided to work in a dry trench, after concreting the bottom of the lock in the jet-grouting technology. In this way, we avoided underwater concreting. Thanks to this, we can say with great certainty that the quality of execution of reinforced concrete wall elements will be at a high level. Undoubtedly, it was a good step,” emphasizes Jarosław Bobrowski from SWECO, which supervises the contract.

Eastern breakwater with sheet piles

Intensive works are also carried out in the Gdańsk Bay area. The driving of steel sheet piling in the main part of the eastern breakwater has already been completed. Currently, tie rods are being installed. A rock mound is also made and XblocPlus concrete blocks are placed. The substrate and a levelling layer of concrete are being made, as well as the superstructure on the western breakwater. The production and delivery of XblocPlus elements for the breakwater heads have started.

A lot is happening also on the other side – in the Vistula Lagoon, where an artificial island is being built. Dredging works and the backfilling of the island’s cofferdams are in progress. A layer of hydrotechnical stone was also made on the technical zone in 20 sections and a mound of hydrotechnical stone on the slope in 11 sections. The sheet piling was cut in 9 sections.

Bridges and enclosed structures
The north bridge is still under construction. There, the assembly of a traffic barrier as well as hydraulic and electrical installations was completed, and the surface was completed on sidewalks and on the road. The bridge has been weighed. Let us recall that the twin south bridge has already been put into operation. In addition, electrical, teletechnical and sanitary works are continued throughout the entire investment. Devices and installations in enclosed structures are also being commissioned.

What’s next?

“Works on the Vistula Spit are proceeding according to the adopted schedule. Already next year, the first ships will be able to enter the Vistula Lagoon from the Gdańsk Bay. Those with the target maximum parameters will use the new waterway in 2023, after the completion of the entire investment,” says Minister of Infrastructure Andrzej Adamczyk.

The pace of works is not slowing down and the next months promise to be equally intense. It is planned, for example, to complete the pile driving works on both breakwaters as well as the installation of wall bollards in the shipping canal. On the artificial island, works related to driving sheet piling, installation of tie rods, construction of geotubes as well as dredging works and backfilling the island cofferdams will still be carried out.

“We are currently implementing two of the three stages into which the construction of the waterway connecting the Vistula Lagoon with the Gdańsk Bay was divided. The progress of the first stage, on the Vistula Spit, reaches over 70 percent. In the second stage, involving the Elbląg River, the contractor started works related to strengthening the subsoil for the road leading to the new bridge in Nowakowo, which will be built as part of our investment. Works related to the preparation of technological roads and the development of the construction site in terms of logistics are also in progress. Later this year, we plan to announce a tender for the third stage – dredging works, which is to integrate the entire investment and connect Elbląg with the Gdańsk Bay with a waterway with appropriate parameters,” said Master Mariner Wiesław Piotrzkowski, Director of the Maritime Office in Gdynia.