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Søndersø Vandværk nedrives


Modernisation of Værket ved Søndersø

Construction management of new waterworks at Søndersø

In order to provide clean and softer drinking water to citizens in Greater Copenhagen, the utility HOFOR is transforming the Værket waterworks at Søndersø into a modern, fully automated waterworks with state-of-the-art technology.

Sweco is one of the consultants on the project and is responsible for managing the construction of the new water softening plant and ensuring the feasibility of the waterworks design.



In progress, expected to be realised in 2025
Design, supervision, hydrogeological study, environmental impact assessment report
Advisory role
Construction management
Øllgaard | Cowi | Niras | Krüger
Søndersø Vandværk nedrives
Søndersø Vandværk visualisering

New environmental impact assessment screening needed

The construction management task began with the demolition of Værket at Søndersø. However, we quickly learned that the initial building contamination investigation conducted by another consultancy firm was not thorough enough. Sweco was therefore asked to conduct a comprehensive mapping of building contamination (asbestos, PCB, heavy metals and PAH) at Værket at Søndersø and other waterworks to provide a complete basis for proper cleanup.

Sweco made sure that a thorough cleanup of the waterworks was conducted by the demolition team before demolition began.

Prior to the start of the project, the developer also conducted an environmental impact assessment screening of the project. At the time, it was decided that no environmental impact assessment of the project was required. In connection with the demolition and design of the new building and processing plant, it turned out that the plant did not comply with the requirements and limits specified in the original environmental impact assessment decision. In parallel with the design and construction of the new waterworks, Sweco was asked to prepare an environmental impact assessment report for the combined plant.

In connection with the environmental review, bitumen deposits on the deep concrete foundations were detected. These concrete foundations were located about 3 metres below the water table in the main reservoir, from which drinking water for the waterworks is sourced. Sweco’s groundwater experts therefore conducted a hydrogeological study, designed a groundwater lowering system and prepared regulatory applications for extraction wells and groundwater lowering. Sweco oversaw the groundwater lowering as part of its construction management.

In connection with the removal of foundations, Sweco also made sure that fill, earth and rubble were properly excavated and sorted.

A sustainable waterworks

The aim of the new Værket at Søndersø is to create a sustainable waterworks with the lowest possible environmental impact while ensuring safe drinking water. In addition, the aim is to soften the water to reduce wear and tear on white goods and chemical and soap consumption.