Precautionary measures to minimize environmental impact
A hydrodynamic numerical study of the current in the port shows that only marginal and temporary effects (e.g., from contaminants, turbidity, and low-oxygen areas) on the adjacent waters are expected even with the tidal construction method. Appreciable particle movement is only expected in the immediate area and only to an extremely low extent out to the Stromelbe. The following precautionary measures are planned in order to prevent any negative effects on the waters:
- To prevent the silt at the bottom of the port from being displaced or swirl up during filling and to stabilize it, a top coat of sand will be put in place in the first step of the raising process (“irrigation”).
- On top of this, mixed soil typical to the port (with a limited fine particle percentage of max. 40%) will be placed to reduce the turbidity of the water and thus lower the risk of oxygen depletion.
- To minimize the “contact surface” of the flow on the deposited soil, the individual sub-areas from South to North will be raised as quickly as possible to above the water line at +2 meters a.s.l. For raising below this water line, only LAGA Grade Z1 soils will be used.
Water: changes in tide dynamics
The Federal Waterways Engineering and Research Institute (BAW–Bundesanstalt für Wasserbau) has determined the possible effects of the project on the water levels and current as well as the water exchange within the Port of Hamburg. The study states the following:
- The planned works will have a minimal effect on the high-tide and low-tide water levels, and will come in at well under the threshold. There will be no measurable or observable effects.
- The tidal currents will increase above the threshold of 0.02 m/s only in the immediate area, in the Rosshafen, Vorhafen, Ellerholzhafen, and Travehafen harbor basins.
- The creation of the Steinwerder Süd location will not significantly alter the sedimentation in the Lower Elbe.
- The tidal volume of the Ellerholzhafen, Oderhafen, and Travehafen basins will be reduced. The time needed for the exchange of 90% of the water located there will be up to 17% less after the renovation than currently – although the change will depend greatly on the tidal scenario (high/low tidal range).
In its hydrological study, the BAW came to the conclusion that the Steinwerder Süd project will not have any significant/measurable and observable effects on tide dynamics.
Designing the renewal to be as environmentally safe as possible
Removing the peaks and raising the Oderhafen harbor basin will require a large quantity of earth to be moved. Although only a negligible, temporary impact is expected due to the intended “tidal” construction method, precautionary measures will be taken to minimize any potential impact on waters.
Soil management: around 2.9 million cubic meters of earth will be moved
Raising the Oderhafen basin and the entire area in general will require large quantities of earth (around 1.1 million cubic meters of sand and around 1.8 million cubic meters of mixed soil for a total of just under 2.9 million cubic meters). A large portion of this (1.1 million cubic meters) will be obtained directly on site from the removal of the Roßhöft und Oderhöft peaks. An additional 400,000 cubic meters will be supplied from the renovation of the nearby Kreetsand/Spadenlander Busch spoil area into a tidal flats region. The just under 1.5 million cubic meters remaining can be obtained from other port and infrastructure projects in the metropolitan area.
Water: water surface area ratio in the river
To renovate the port for Steinwerder Süd, 8.3 hectares of land will be excavated and 10.4 hectares of water surface area will be built over. This will result in a negative water surface area ratio of 2.1 hectares. There are plans for a series of projects in the surrounding area that will make a significant positive impact on the water surface area ratio.
Raising: tidal construction method
The raising of the Oderhafen basin will use what is called a tidal construction method in order to haul most of the earth in and dump it directly on site from the waterway using hopper dredger. To minimize water exchange during raising and thereby minimize particle movement into adjacent waters, what is called a sill and a partial retention dam will be constructed in the northern area of the Oderhafen basin.