May 26th, 2021

Recultivated future for former opencast mine

reclamation opencast mine Sedlitz

reclamation opencast mine Sedlitz

Germany is phasing out coal. In some parts of the country, coal production has long since ceased. What will become of the former opencast mine? Tractebel Hydroprojekt accompanies the recultivation of the post-mining landscapes on the state border between Saxony and Brandenburg. The region on Lake Sedlitz is to become an attractive holiday and residential area. Since the end of 2019, the work on the weir structure has been completed. With the completion of the Sielbauwerk in January 2021, another important milestone has been reached.

The recultivation of the lignite opencast mining area in  the Lusatian coalfield creates the Lusatian chain of lakes northeast of Senftenberg. Its catchment area covers around 200 square kilometres.

Tractebel Hydroprojekt has been supporting the project since 2014: On behalf of the Lusatian and Central German Mining Management Company (LMBV), the hydraulic engineering experts are planning  a conductor system to connect the chain of lakes from the future Sedlitzer See to the Schwarze Elster. They also monitor the construction of the measure.

Demanding planning and construction task

The  demanding bauprojekte  benefit from  theexpertise of the experienced planners of Tractebel. From the shut-off system, bisher  parts of the artificial  channel with seven meters sohlbreite,  a two-field  weir structure  and  a  two-field siel structure are completed. Until thearrester system is putinto operation,  a trough structure, a wildbridge, the associated open-air facilities  and around 5.8 kilometres of farm roads in the surrounding area  will be newly laid out.

Weir structure ensures sustainable management

The weir structure completed about 13 months ago and theinlet of the conductor system of Lake Sedlitz  ensures the sustainable management of the chain of lakes. Its level system determines the discharge quantities. At the same time, the  water quality  can  bemeasuredhere. The weir consists of two  fieldsn with five meters  eachn  Breite  and  hasdouble stroke shooters as closures.   With them,  the water discharge from the Sedlitzer See can beregulated. The static  support system of the  closures was designed as a  folding unit and is made of structural steel with passive corrosion protection. Rising spindles with electric drive take over the adjustment movement. They are accessible fromtheservice.

The fact that the system is also functional in winter is ensured by a sealing surface accompanying heating and an air bubble system. The upper water level in Lake Sedlitz is regulated by automatic control. A new transformer station secures the power supply of the weirsystem. In the case of revision, i.e. for the inspection or repair of the closures, aluminium dam beams are used, which can be placed in front of the closures with the help of a so-called pliers beam and ensure dry access to the components. Outside the revision times, these dam beams remain  in the newly built dam beam warehouse.

Siel building protects Rainitza and Sedlitzer See from flooding of the Black Elster

The sielbuilding  secures the deductant system against backwaters during flooding in the Black Elster. It is  designed as a so-called beam weir, in which the upper area of the weir fields is each closed by a concrete wall transverse to the flow direction.   The underlying "windows" can be closed with underflowable  contactors.  This prevents  a backwater of the Black Elster in the feedwater system during flooding.

Drive blocks with electric drive take over the adjustment movement. They are von ambedienstg aus zugänglich. Many  technical details are similar to thedesign of the weir structure:the  field widths  are  five metres each  and  the  static  support system of the closures  is  made of structural steel with passive corrosion protection  as a  folding unit. Also a  sealing surface-accompanying heating and  an air bubble system are part of the equipment. Because of  the same  field widths, the aluminum dam beams of the  weir can also be used at the siel.  

The completion of the weir and siel structures marks an important milestone for the project, as they are an essential part of the conductor system. Next, tractebel's experts will focus on the further construction of the artificial canal and the expansion of the existing rainitza river.

 

 

The new weir structure on Lake Sedlitz is still dry and will take up its control function after completion of the entire conductor system. (Photo: STRABAG)

The new weir structure on Lake Sedlitz is still dry and will take up its control function after completion of the entire conductor system. (Photo: STRABAG)

With the closures of the new weir structure, the water discharge from Lake Sedlitz into the discharge system will be controlled in the future.

With the closures of the new weir structure, the water discharge from Lake Sedlitz into the discharge system will be controlled in the future.

The Siel building serves to protect against backwaters during flooding in the Black Elster.

The Siel building serves to protect against backwaters during flooding in the Black Elster.