Construction of the Cloudburst Tunnel in Valby, Denmark

Major contract in Denmark: Eiffage Infra-Spezialtiefbau and the cloudburst phenomenon.

Another significant milestone for Eiffage Infra Specialised Civil Engineering: Together with the main contractor MT Højgaard Danmark, our company has been commissioned to carry out one of the largest infrastructure projects in the Greater Copenhagen area – the construction of the approximately 2.4 km-long Cloudburst Tunnel in Valby.

The aim of the project is to better protect the districts of Valby and Frederiksberg West against heavy rainfall and so-called ‘cloudbursts’. The tunnel serves as an underground retention basin capable of holding up to 30,000 m³ of rainwater. This is roughly nine times the volume of water contained in the Round Tower, a Copenhagen landmark. The water is then channelled in a controlled manner to the sewage treatment works. Only in extremely exceptional cases is it discharged via outlets into natural watercourses such as the Gåsebækrenden or the Enghave Canal – a targeted contribution to the protection of the nearby Kalveboderne Natura 2000 site. The tunnel begins in the F.L. Smidth area in Valby and runs deep through the limestone beneath well-known neighbourhoods such as Grønttorvet, Valby Idrætspark, Valbyparken and Musikbyen in Sydhavnen. Construction work began as early as the summer of 2024, with completion of the tunnel and pumping station scheduled for 2028.

With a contract value of around DKK 490 million, the project is one of the largest initiatives in the Danish climate protection programme. The tunnel forms part of a comprehensive plan comprising hundreds of so-called ‘cloudburst’ projects, designed to make Frederiksberg and Copenhagen more resilient to extreme weather. Thanks to our extensive experience in specialised civil engineering and tunnelling – including on similarly complex projects – Eiffage Infra Spezialtiefbau was selected as a reliable partner. “A project of this scale poses significant challenges – we have the expertise to deliver it successfully in collaboration with MT Højgaard,” said Carsten Lund, CEO of MT Højgaard Danmark.

The current progress of the works is promising: the first shaft, designated ‘ENG’, has been fully drilled, and excavation is due to begin shortly. At the same time, our drilling rigs have been strategically redeployed: Drilling rig 1 has already begun its move to shaft “MUS”, whilst drilling rig 2 is now taking up position at shaft “BLU”. This means the team is working on all four shafts simultaneously – an important milestone in the project’s progress. Meanwhile, shaft “FLS” is being managed by our joint venture partner, ensuring that the entire shaft programme is operating at full capacity. This coordinated approach not only accelerates the project but also highlights the excellent collaboration within the entire team and with our partners. The clients, HOFOR and Frederiksberg Forsyning, also emphasise the importance of the project: it not only protects people and property but also enhances safety in the affected urban areas – an investment in the future of urban infrastructure.

The contract includes:
• The construction of four working shafts
• The tunnelling of three main tunnel sections
• The installation of the tunnel linings
• Connection to existing sewers via two structures
• The construction of a drainage pumping station on the Enghave Canal