Finland will build the world's third longest undersea tunnel

It is reported that Finland will build the Helsinki Undersea Heat Recovery Project water tunnel, the third longest undersea tunnel in the world.

The project, worth 400 million euros, will use TBM to dig a 17km long undersea tunnel, which will collect seawater from the Baltic sea at a temperature of about 2 ° c and a depth of 70m. The tunnel will transport seawater 50m³/s through the tunnel to the Salmisaari plant, which will be used in the district heating system of Helsinki, Poland.

In addition to the water tunnel, the contract also includes the construction of underground chambers to house the facilities, a 9km long drill-and-blast tunnel to discharge excess seawater, water intake caissons and pipelines. The project is currently under development, with construction expected to begin in the fall of 2024 and take about five years to complete.