FAQ

In order for ships to be able to enter the port safely and unhindered, the Elbe and the harbour basins must be continuously kept free of excess sand and mud by dredging, just like in most seaports around the world. The dredged Elbe sediments are an important natural component of the water. We therefore transport the dredged material to tested and suitable locations in the Elbe and North Sea, where it is mixed and distributed with the natural sediments.

The dredging volumes can fluctuate greatly from year to year, depending on the natural conditions, in particular how much water flows from the upper Elbe to Hamburg. Whereas in 2011, a wet year with a lot of water from the upper Elbe, only just under one million tonnes had to be dredged, between three and six million tonnes had to be dredged in the following dry years.

The main cause of high dredging volumes is heavy sedimentation, especially when little water flows from the Elbe region upstream of Hamburg towards the Hanseatic city. The drier it is there, the more dredging is required in Hamburg and the tidal Elbe, as more sediment from the North Sea reaches Hamburg with the strong tidal current (known as tidal pumping). In addition, a large proportion of the dredged material - as other relocation sites are not available in sufficient quantities - has to be returned to the Elbe just below the harbour, at the Elbe island of Neßsand. From there, it is quickly returned to the harbour (recirculation dredging)

The fairway upgrades, as well as other changes to the Elbe such as embankments and barriers, have generally led to stronger currents and thus more sedimentation. For this reason, river engineering measures were implemented during the last fairway upgrade to dampen tidal currents and limit sedimentation. This means that the impact of the last fairway upgrade on dredging volumes in Hamburg is only minor.

The dredged material in Hamburg consists of natural Elbe sediments that reach the harbour from two directions: With the water of the Elbe from the upper Elbe area and with the tidal current from the direction of the North Sea. Mud and sand are deposited throughout the entire current-calmed harbour area and must then be dredged. The main dredging areas are, for example, the Köhlbrand, the Norderelbe, the Süderelbe and the large harbour basins.

The dredged material consists of natural Elbe sediments, i.e. coarser sand and finer-grained mud. It also contains small amounts of organic components such as plant residues.

The contamination of the dredged material corresponds to the pattern typical of the Elbe. Using modern analytical methods, a large number of organic pollutants and heavy metals can be detected everywhere in the Elbe. These originate almost exclusively from historical sources in the upper Elbe region - mining and industry in the 19th and 20th centuries are the main causes here. The pollution decreases the further the sediments travel towards the estuary as a result of mixing.

Overall, the pollution of the Elbe has fallen sharply since the early 1990s, meaning that most of the freshly deposited sediments in Hamburg are now so clean that they can remain in the water in an environmentally friendly manner, i.e. they can be relocated. This is checked by regularly sampling and analysing the sediments (so-called releases) before dredging. Almost only old, historical sediments, such as those that sometimes have to be dredged in the eastern harbour areas, are so highly contaminated that we have to treat and dispose of them on land. However, over 95% of the dredged material today is so slightly contaminated that it even fulfils the legal requirements for children's play areas.

The upper layers of sediment are removed during dredging work. This procedure changes the bottom of the water body only minimally and is also mainly carried out in areas where there is no particular biological value anyway. Fish can usually easily avoid the dredger. At certain times and in certain areas, dredging is avoided as a precautionary measure, e.g. during the spawning season of the finfish, a particularly protected fish species.

The impact at and around the relocation sites is assessed by means of comprehensive impact assessments prior to utilisation. The relocation site can only be used if there is scientific evidence that the relocation will not have a significant adverse impact on the environment. This is prescribed by law.

If the relocation site is then used, the assumptions of the forecast are regularly checked by scientific investigations (monitoring). If unforeseen or unacceptable changes occur, these are recognised by the monitoring and the relocation is adjusted or discontinued.

Over 95% of the dredged material is relocated or relocated in the water, so that it mixes with the natural sediment and can no longer be distinguished from it. This conserves resources, is standard international practice and also makes ecological sense. Dredged material that is relocated in the area of the Elbe estuary can to a certain extent counteract natural sediment loss in this area.

Higher contaminated dredged material, which has to be treated and disposed of on land, is used as a building material at the HPA's dredged material landfill sites (drainage sand, sealing layers) after separation into sand and fine material. Theoretically, it can also be used at other landfills. It can also be used as a substitute for clay in dyke construction or in the production of building materials (bricks, expanded clay pellets). Overall, however, demand for the use of dredged material on land has been low to date, not least because of the high costs involved.

The vast majority of dredged material is transported by ship to relocation sites in the Elbe or North Sea. These include the relocation sites Neßsand, St. Margarethen, Neuer Lüchtergrund and Tonne E3.

If the dredged material is more heavily contaminated, it is brought ashore in Hamburg, where it is treated and safely deposited in landfill sites.

A comprehensive assessment is carried out for each relocation site, taking all legal requirements into account. The relocation is only permitted if it can be ruled out that the shipment could have a significant adverse impact on the environment. Shipping and other utilisation concerns such as fishing or tourism are also examined.

Water depth maintenance is always carried out in a system of extensive tests. Before dredging, the sediments are levelled, sampled and tested for pollutants. During the dredging itself, the position, quantity and density are precisely determined on the ships and transmitted to the HPA in real time (remote hopper monitoring). A long-term and comprehensive monitoring programme is then carried out at and around the relocation site. For example, samples are regularly taken and analysed around the E3 bin as well as on the coasts. Relocation may only continue if all quality requirements are met. This ensures that the relocation has no significant negative impact on the environment, tourism or fisheries. We publish all results transparently.

Basically, the dredged material is very similar to the natural sediments around the relocation sites. It therefore mixes with them and becomes indistinguishable within a short time. The dredged material is dispersed with the respective currents. As the dredged material is typical Elbe sediments, this is also intended, as sediments are an important component of the watercourse.

The changes to be expected from the use of a relocation site are determined in advance by means of comprehensive scientific studies, modelling and forecasts. Relocation is only permitted if the expected changes are minor and environmentally compatible. Temporary turbidity clouds and a covering of non-local material occur locally. As soon as the relocation is interrupted, recolonisation by soil organisms that are very well adapted to changes takes place within a short period of time.

Just like the sedimentation and dredging volumes themselves, the costs of maintaining the water depths also fluctuate from year to year. The costs include more than just the dredging and relocation itself. Monitoring, compensation payments and analytics also have a significant impact. Added to this are the high costs of land treatment and disposal of highly contaminated sediments. Around 30 million euros are incurred annually for this area alone. In recent years, the overall costs have been comparatively high, as the unfavourable conditions (drought in the Elbe region) meant that more dredging was required throughout. Around 90 million euros had to be spent annually on the entire water depth maintenance.

In principle, all parties involved agree that unnecessary recirculating dredging, such as at Neßsand, must be significantly reduced and that this can only be achieved through sufficient removal of excess sediment from the Hamburg area, e.g. into the Elbe estuary or the North Sea. The federal states agreed on this in a joint declaration back in 2008.

However, there is always disagreement on the question of where and under what conditions the dredged material should be relocated. There are sometimes very different interests here. Despite these conflicts of interest, we remain in close dialogue with all parties involved with the aim of ultimately implementing the best technical solutions.