Pile-driving works on the artificial island about to finish
181 hectares – this is the size of the artificial island, which is constructed as part of the Vistula Spit canal project. The pile-driving works in this area are just about to end. To close the perimeter, only the membrane and the technical gates on the island remain to be completed.
The island is created at the level of the village of Przebrno – 4.5 km south-east of the canal through the Vistula Spit and east of the fairway on the Vistula Lagoon. It will be filled with spoil from dredged fairways on the Vistula Lagoon and the Elbląg River. Ultimately, this space is to become a paradise for birds that already visit it.
“We are currently finishing the main pile-driving works, but there is a lot of other work ahead of us to complete the entire cofferdam section. We have completed over 20 percent of the island’s perimeter, which is about 5 kilometres ,” says Mariusz Sasin, Deputy Contract Director for the Construction of the Island from the NDI/Besix consortium, which carries out the cut.
Works related to the extraction of mud from the inside of the cofferdam and diving works related to the underwater assembly of tie rods are also in progress. The island’s ring is filled with sand.
“After completion of the dredging works, the interior of the cofferdam is filled with sand. We pour it several dozen centimetres above the water level so that the excavators can work in dry conditions. They profile the sand to the desired profile section. Then, a geotube is made on its surface, which is a sand structure with the use of geosynthetics,” explains Mariusz Sasin.
After reprofiling and making the geotube, the whole structure is covered with hydrotechnical stone, which comes from the port in Elbląg using self-propelled barges. In turn, it is delivered to the port by rail from the south of Poland.
The fine fraction of stone is placed on the crest of the cofferdam, which will serve as a technological route in the future. On the other hand, a thicker fraction of stone is laid on the slope – so as to protect the island against harmful waves and ice.
As part of the investment, 442,000 m3 of soil will be built into the backfill of the artificial island, which gives the volume of 118 Olympic swimming pools.
The island is divided into two parts. The first, with a volume of approx. 5.9 million m3, is filled during the fairway construction phase. The second, with a volume of approx. 3.3 million m3, will constitute a reserve for spoil from future cleaning works, necessary to maintain the assumed depth of the fairway to the port in Elbląg.
“The choice of the location of the artificial island was made mainly due to environmental reasons, by the indication of an area with the lowest natural values, where the habitats of the Lagoon are the poorest in terms of benthos and vegetation and away from inventoried spawning grounds, as well as due to the safety of navigation. It is located in a place that is currently of little importance for birds, both during the breeding season and migration within the Vistula Lagoon, and also outside the most valuable habitats of the reservoir for ichthyological fauna. The island will be uninhabited, accessible only to birds,” said Dorota Słabek, Head of the Department of Environmental Impact of the Maritime Office in Gdynia.
Space artificially built on the occasion of the cut will enrich the habitats of Natura 2000 areas. In the area of the Vistula Lagoon, over the last 20 years, there has been a decline of grassland, which is a breeding ground for many species of birds.
“After the island is built and the shores are covered, the right conditions for the nesting of both great crested grebes and mute swans, which are under protection, will appear in the transition zone. In the future, the island may also be a resting and feeding place for water and marsh birds during the migration period, for example, species such as gadwall, shoveler, Eurasian wigeon, mallard, pintail, garganey, Eurasian teal, but also for the protected greater white-fronted geese and taiga bean geese,” – says Angelika Brzeska – Kośmider, Technical and Environmental Engineer from the NDI/Besix consortium. “We also hope that a properly developed island may increase the population of breeding species,” – adds Angelika Brzeska.