Final stretch of the Kalvebod Brygge Cloudburst Tunnel

KALV Forsidebillede (1)

"Sigrid" is the name of the massive 110-ton tunnel boring machine, named at a ceremony on December 20, 2023, at the edge of Copenhagen Harbor. After three months of tunneling she finished chewing her way through the second and final stretch of the Kalvebod Brygge Cloudburst Tunnel.

January 22, 2024
  • SECTORS: Infrastructure, Water
  • COUNTRIES: Denmark
  • CLIENT: HOFOR and Frederiksberg Forsyning A/S
  • DURATION: 2017-2026

The name "Sigrid" dates back to the Viking Age and means "victorious beauty." With a diameter of 3.6 meters and a combat weight of 110 tons, Sigrid appears as a formidable companion as she is lowered into the tunnel shaft at Kalvebod Brygge 45.

"It's something very special to see Sigrid being lowered into the shaft. Now you truly see the scale of the cloudburst tunnel, and it instills a certain humility when standing here today at the ceremony. Many of us have worked hard to be ready for today," says Nikolaj Romm Skytte, project manager at NIRAS after the ceremony in december 2023. 

April 12, 2024 Sigrid finished her way through the second phase of the 1.3-kilometer-long tunnel, designed to protect the eastern part of Frederiksberg and Vesterbro from flooding during cloudbursts. Sigrid takes over from "Signe," which tunneled the first stretch of the Kalvebod Brygge Cloudburst Tunnel.


Interdisciplinary and international expertise

NIRAS provides engineering consultancy for the cloudburst tunnel, and throughout the project from 2017 to 2024, more than 300 employees across NIRAS's organisation have been involved. The consulting spans from the early analysis phase to detailed planning, procurement, and execution. NIRAS will be involved until the cloudburst tunnel and pumping station are put into operation in 2026.

"The interdisciplinary aspect has been prevalent throughout the project, where expertise in environment, geotechnics, construction, infrastructure, water, and utilities has been involved. In the first half of 2024, the focus will be on construction, and after the summer, much of the installation work will begin. Many of the same expertise areas will come into play again," says Nikolaj Romm Skytte.

According to Nikolaj, it has been crucial to collaborate with a strong Danish and international advisory team assembled in 2017. Experts from Danish GEO and the architectural firm Gottlieb Paludan, tunnel specialists BabEng from Germany, and Jacobs from England contribute to the advisory team with NIRAS at the forefront.

"The collaboration with HOFOR and Frederiksberg Forsyning has been excellent, and it's always good to work with a client who is not afraid to take the lead with new solutions," says Nikolaj Romm Skytte.

A project with significant complexity

Before the tunneling phase, the project's parties went through a lengthy process of obtaining regulatory approvals, design and analysis, and handling many safety requirements. According to NIRAS's project manager, the project becomes particularly complex as the tunnel has to pass under roads, railway tracks, the entire Meatpacking District (Kødbyen), and cross the Metro line very closely underground. This adds to the demanding yet exciting nature of tunnel construction:

"The cloudburst project has special solutions for complex issues, which is natural when establishing infrastructure of this size in dense urban areas. The solutions have posed some challenges, especially because we had to construct a tunnel shaft in the harbor basin, where we had to build a large working platform in the harbor. At the same time, we have tunneled under the New Theater and in 2024, we will cross all the railway tracks leading to the Central Station. The regulatory processes required to obtain the necessary permits for such a project are very complex, and many things need to fall into place at the right times," says Nikolaj Romm Skytte.

NIRAS's services:

  • Concept development
  • Hydraulic calculations
  • Geotechnical investigations and soil management
  • Development of tunnel alignment
  • Risk analysis and management
  • Environmental mapping and assessment
  • Design of the pumping station
  • Power installations and supply
  • Preparation of EIA basis and EIA application
  • Public dialogue and stakeholder management
  • Authority approvals and building permits
  • Groundwater management
  • Occupational health and safety
  • Detailed design of construction structures and buildings
  • Detailed design of mechanical and electrical installations
  • Design with BIM 3D modeling
  • Building registration
  • Monitoring of buildings and infrastructure
  • Programming and automation CE marking
  • Tendering and contracting
  • Supervision

No more flooding?

The Kalvebod Brygge Cloudburst Tunnel is a crucial piece among the hundreds of projects aimed at securing Frederiksberg and Copenhagen against flooding due to cloudbursts and heavy rains. There are specific requirements for a large cloudburst tunnel, making the project both exciting and challenging:

"We have conducted uptime calculations showing a reliability between 99.95% to 99.99%, which is an exceptionally high reliability for a cloudburst system like this. There can be several years between the extreme rain events, but when there is a cloudburst, we don't get a second attempt. The system just has to work. But with a strong team behind us and the incredible groundwork that has been done, I stand 100% behind the project," says Nikolaj Romm Skytte.

Extreme dimensions

The tunnel will be up to 3 meters in diameter and can retain 10,000 cubic meters of water. During very severe cloudbursts, a pumping station at Kalvebod Brygge can pump the water from the tunnel into the harbor at a rate of 20 cubic meters of water per second. The concept of the pumping station and testing how water can be pumped out into the harbor at high speed has been one of the significant milestones in the project, according to Nikolaj.

Nikolaj explains how timing and coordination are both crucial and the most challenging aspects of the project:

"The biggest challenge is timing and getting all the different processes, regulatory dialogues, permits, and the completion, control, and adjustment of the design to be ready so that we can keep to the schedule. All the hydraulics and construction technical aspects must align with the electrical and mechanical systems, and it is a complex operation. Individually, the elements are quite simple, but when everything has to work together, it becomes complex," 

says Nikolaj Romm Skytte.

Watch the video

Kalvebod Brugge cloudburst tunnel during the years

2016: HOFOR and Frederiksberg Forsyning decide to construct the cloudburst tunnel.

2017: The advisory team led by NIRAS is selected.

2018-2020: Tunnel project planning.

2020-2021: Contractors are chosen, and the construction phase commences.

2022: The contractor begins the project.

2023: Completion of the initial phase of tunneling.

2023: Tender for installation work on one of Northern Europe's largest pumping stations.

2023 December: Naming ceremony for Sigrid - the second phase of tunneling begins.

2024: Commencement of concrete and installation work in the shafts.

2025: Installation work for the pumping station at Kalvebod Brygge begins.

2026: The cloudburst tunnel is ready for use.


Get in touch

Nikolaj Nørgaard Romm Skytte

Nikolaj Nørgaard Romm Skytte

Project Director

Allerød, Denmark

+45 4299 5343

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