Overall reconstruction and expansion of the Central Waste Water Treatment Plant Prague (WWTP) on the Císařský Island, New water line and other objects

After a long time of preparation we saw the beginning of "Total overhaul and extension of the WWTP on the Císařský island." The aim of the whole project is to optimize the treatment of wastewater produced by the capital of our republic and the preparation and implementation of such a complex wastewater disposal, which meets the mandatory legislative conditions for wastewater discharge.

Total basic solution concept reconstruction and expansion of the WWTP is that of building new water lines (NWL), which takes up 50% of future capacity in the construction of major pumping stations and the inlets to the WWTP and reconstruction of existing WWTP. Continuous waste water treatment must be achieved during all future construction work on the reconstruction of existing WWTP. Both water lines, old and new will now be incorporated into a unique micro-region Troja basin and covered NWL will be created expressive uniform and permeable recreational area. Construction NWL is performed on the basis of the work under FIDIC contract conditions called Yellow Book (design, build and operate).

To ensure a broad construction NWL pit and providing a foundation building pit main pumping station and the inflow objects were in a large scale used special foundation technologies.


The construction pit for a new water line WWTP, stage 0001

Extensive construction pit for a new water line WWTP dimensions of about 560 x 123 m, was most shoring perimeter wall of sheet piles, installed into the slurry cut-off diaphragm wall grab excavated and sunk into impermeable subsoil. On the part of the perimeter where the bottom surface was in a silicified shale layers, grab unminable, pit was shored by secant pile wall. Shoring structures were anchored in two levels 3-6strand temporary anchors through standardized steel anchor straps.

The construction pit for the main pumping station and WWTP inflow object, stage 0007

The main pumping station (MPS) and the inflow object (IO) are part of the construction stage 0007 of the  total reconstruction and expansion of the Central Waste Water Treatment Plant Prague (WWTP) on the CísařskýIsland and will be put into operation with a new water line (NWL). The main pumping station and WWTP inflow object are built in a common pit, situated between the existing WWTP in the northwest and the construction pit for the object NWL to the east. Special feature of the project is the fact that through the construction pit three pipes of overflow drain rainwater backbone sewers go. These were for the construction period temporarily transferred to a lower horizon. In the final state the function of these discharges will changed and to the inflow object and than to the main pumping station wastewater from the backbone Prague sewers will flow. From it will be pumped to the existing WWTP (up to 4,1 m³ /s) as well as new water line (up to 7,1 m³/s).

Draft shape and method of construction pit shoring MPS and IO was then given a certain extent by the existence of the overflow drain. Construction activity took place in two main phases: the first included securing common construction pit with diaphragm walls, the second securing dugout for siphon overflow outlet and sealing the outlet passage space between the construction pit using diaphragm walls by jet grouting.