District heating tunnel, Amager Power Station

Københavns Energi wanted a 4 kilometre long tunnel built 30-40 metres under the city in a limestone seam. MT Højgaard and the tunnel boring machine Astrid were chosen to undertake the extensive tunnelling and concrete work.

To ensure the capital's inhabitants inexpensive and environmentally friendly district heating, MT Højgaard built a 4 kilometre long tunnel 30 metres under central Copenhagen for the client, Københavns Energi.

The 4-year project was completed in August 2009. The tunnelling work was carried out using the 500 ton, 128 metre long tunnel boring machine Astrid. The tunnel section from Amager Power Station to Adelgade in central Copenhagen and then on to Fredensgade near the National Hospital took 10 months, covering 10-25 metres per day. Besides boring the tunnel, Astrid also simultaneously lined the tunnel with concrete rings.

40 metre shafts

It was not only the tunnel that required boring and excavation work. MT Højgaard also established three tunnel shafts of up to 25 metres in diameter and depths of between 25 and 40 metres. It was between the three shafts that the district heating tunnel itself was bored.

In 2008, MT Højgaard handed over the tunnel to the next contractor, who installed permanent district heating pipes while we completed the concrete work including the internal shaft walls, decks, staircases and elevator shafts.

Economic and environmental benefits

Calculations show that the new tunnel will save the city 200,000 tons of CO2 emissions annually, equivalent to the exhaust emissions of 53,000 cars.

The economic and environmental benefits arise from the fact that the heat is produced at Amager Power Station's efficient new plant which uses CO2-neutral biomass to produce district heating.