FAQ

In order for ships to be able to enter the port safely and unhindered, the Elbe and the port basins must be continuously kept free of excess sand and silt 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 mixes and disperses 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 tons had to be dredged, between three and six million tons had to be dredged in the following dry years.</p

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 (tidal pumping). In addition, a large proportion of the dredged material has to be returned to the Elbe just below the port, at the Elbe island of Neßsand, as there are not enough other dredging sites available. From there, it is quickly returned to the port (recirculation dredging)

The fairway adjustments, as well as other changes to the Elbe such as embankments and barriers, have generally led to stronger currents and therefore more sedimentation. For this reason, river engineering measures were implemented during the last fairway adjustment to dampen the tidal current and limit sedimentation. The impact of the last fairway adjustment on dredging volumes in Hamburg is therefore only minor.</p

The dredged material in Hamburg consists of natural Elbe sediments that reach the port 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. Silt and sand are deposited throughout the entire current-calmed port area and must then be dredged. The main dredging areas are, for example, the Köhlbrand, the Norderelbe, the Süderelbe and the large harbor basins.</p

The dredged material consists of natural Elbe sediments, i.e. coarser sand and finer-grained silt. Small quantities of organic components such as plant remains are also included.</p

The contamination of the dredged material corresponds to the typical Elbe pattern. With modern analytics, 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 as the sediments move towards the estuary due to mixing.

Overall, the pollution of the Elbe has fallen sharply since the beginning of the 1990s, so 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 regular sampling and analysis of the sediments (so-called releases) before dredging. Almost only old, historical sediments, such as those that sometimes have to be dredged in the eastern port 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 low in contamination that it even meets the legal requirements for children's play areas.</p

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 are generally able to avoid the dredging equipment. 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 dredging sites is assessed prior to use by means of comprehensive impact forecasts.

Only if these are scientifically proven to come to the conclusion that there will be no significant adverse effects on the environment as a result of the transfer can the transfer site be used. This is prescribed by law.

If the transfer site is then used, the assumptions of the forecast are regularly checked by scientific investigations (monitoring). If unforeseen or unacceptable changes occur, these are identified by the monitoring and the shipment is adjusted or discontinued.</p

Over 95% of the dredged material is relocated or moved 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. This allows the mudflats to grow with the sea level.

After separation into sand and fine material, highly contaminated dredged material that has to be treated and disposed of on land is used as construction material at the HPA's dredged material landfills (drainage sand, sealing layers). Theoretically, it can also be used in 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 so far been low, not least because of the high costs involved.   

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

If the dredged material is more contaminated, it is brought ashore in Hamburg, where it is treated and safely disposed of in landfill sites.</p

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

Water depth maintenance is always carried out in a system of extensive tests. Before dredging, the sediments are sounded, 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 program is then carried out at and around the dumping site. For example, samples are regularly taken and analyzed around the E3 garbage can as well as on the coasts. Shipments may only continue if all quality requirements are met. This ensures that the shipment has no significant negative impact on the environment, tourism or fishing. We publish all results transparently.

In principle, the dredged material is very similar to the natural sediments around the dredging 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 sediment, this is as it should be, as sediment is an important component of the watercourse.

The changes to be expected from the use of a transfer site are determined in advance through comprehensive scientific studies, modeling and forecasts. The transfer 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 transfer is interrupted, recolonization by soil organisms that are very well adapted to changes takes place within a short period of time.</p

Just like the sedimentation and dredging volumes themselves, the costs of water depth maintenance also fluctuate from year to year. The costs include more than just the dredging and dumping itself. Monitoring, compensation payments and analytics also have a significant impact. In addition, there are the high costs for 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 unfavorable 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.</p

<p>However, there is always disagreement on the question of where and under what conditions the dredged material should be transported. In some cases, there are very different interests here. Despite these conflicts of interest, we remain in close contact with all parties involved with the aim of ultimately implementing the best technical solutions.</p