A new wastewater treatment plant is being built underground in Espoo, Finland

Helsinki Region Environmental Services in Finland is building a new wastewater treatment plant in Espoo's Blominmäki bedrock to replace the current Suomenoja plant, which doesn't have enough capacity to handle the entire region's wastewater in the future.

The caves excavated underground will house wastewater treatment basins and the majority of other facilities, too. The aboveground parts of the wastewater treatment plant will consist of the administrative and repair shop buildings, the methanol reception station, biogas storage facilities and the exhaust tower.

Our contract includes the excavation works and rock support works of the new wastewater treatment plant. "We are excavating multiple parallel caves at the same time. We will utilise our experience from our similar earlier projects. Our customer will benefit this through effective project execution. We are placing particular focus on carrying out the excavation work efficiently with minimal disturbance to the environment and local residents," says Harri Kailasalo, Executive Vice President, Infra projects at Lemminkäinen.

Progress of excavation to pick up speed

We started tunnel excavation in autumn 2015. The work on plant was about five per cent complete as of January 2016, but the excavation of the bedrock will pick up speed during the spring. The excavation will proceed at maximum speed with 5–6 drilling jumbos. Excavation and support works will continue until January 2018.

In addition to open excavation, the excavation work for the aboveground facilities includes drilling, sheeting, loading and stone transport. In the tunnels, we are carrying out blasting and aggregate transport. Blasting work and excavation vibration are measured and monitored during the entire blasting phase. We will excavate approximately 910,000 cubic meters of rock through three tunnels.

After its completion in 2020, the treatment plant will process the wastewater of 400,000 residents. It is estimated that by 2040, a total of 150,000 cubic metres of wastewater will flow through the new treatment plant daily. According to Jukka Mäkelä, Mayor of Espoo, the wastewater treatment plant is a good example of cooperation across municipal boundaries. "The plant will treat wastewater from Espoo, Kauniainen, Kirkkonummi, Siuntio, western Vantaa and possibly Vihti. The plant is centrally located with respect to the future urban structure," Mäkelä says.

"The Blominmäki plant will achieve by far the best wastewater treatment results in Finland and the entire Baltic Sea region. It will also be the most energy-efficient treatment plant in Finland, and perhaps all of Europe," says Raimo Inkinen, Executive Director of Helsinki Region Environmental Services Authority.


Blominmäki wastewater treatment plant
HSY Helsinki Region Environmental Services
City of Espoo