[et_pb_post_title title="off" meta="off" featured_image="off" admin_label="Sanierung "Schneller Graben" in Hannover
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Redevelopment "Schneller Graben" in Hanover

On behalf of the state capital of Hannover, the Schnelle Graben and a section of the Leine have been de-silting since December 2020 in order to re-establish sufficient retention space for flood events. In addition, the progressive silting up of the Schneller Graben is to be counteracted. The de-silting is intended to increase the discharge cross-section again and ensure better flow through the Schneller Graben in the area of the weir. The remediation work is being accompanied by an expert opinion from M&P Ingenieurgesellschaft mbH. Prior to this, we carried out work phases 1 to 7 and in situ sampling from June to October 2020.

In the course of the desilting work, the sediment is to be removed up to a height of 49.50 mNN. This corresponds to sludge thicknesses between 1.09 m and 2.33 m. The sediment from the Leine and the Schneller Graben will be pumped to the BE area by suction dredger and treated there accordingly. In the area of the Schneller Graben there is also a silted-up area of approx. 540 m², which must be cleared and freed of all plant material before the actual desilting. Afterwards, the suction dredger is to loosen the material from the water side with its cutting head and also transport it to the BE area.

Due to the high sand content, especially in the Leine area, this fraction is first separated. The sand is dewatered purely gravitationally in containers. The finer-grained material is dewatered with the addition of a flocculant using a high-performance centrifuge. After dewatering, the material to be disposed of must have a dry matter content of at least 40 % or be compact so that it can be transported and accepted. Currently, dry substance contents of approx. 50 % are achieved for the sludge and approx. 85 % for the sand.

The Leine area was already completed in mid-January 2021. By the end of February 2021, the Schnelle Graben should also be completed. According to in situ sampling, a total of approx. 3,850 m³ of sediment will be produced, which can be transported mainly as LAGA Z2 (lead, zinc and sulphate) to the corresponding recycling or disposal facilities.