YIT and Helsinki Region Environmental Services HSY have signed an agreement to build an underground wastewater treatment plant in Blominmaki, Espoo, Finland.
The €206m project will be carried out as a project management contract.
Construction will begin in April 2018 and the plant will be commissioned in 2021.
YIT will also execute the machinery, HVAC, automation and instrumentation work, and the electrical installation.
After completion, the 10-hectare plant will process the wastewater of 400,000 people.
According to Espoo Mayor Jukka Makela, the wastewater treatment plant is a good example of cooperation across municipal boundaries.
Makela said: “Studies show that Espoo is the most sustainable city in Europe. This project provides excellent support for the sustainability of the whole Helsinki region and the Baltic Sea.”
The new plant will replace the current Suomenoja plant, which does not have sufficient capacity for processing the region’s wastewater and treating it according to stricter environmental requirements in the future.
By 2040, 150,000m³ of wastewater is estimated to flow through the new plant each day.
Besides traditional wastewater treatment methods, the facility will also use disc treatment to remove phosphorus and UV treatment to remove microbes.
The goal is to treat more than 96% of the phosphorus and organic matter in the wastewater and more than 90% of the nitrogen.
The company has already begun work in Blominmäki in autumn 2015 with the excavation work for the cave system needed for the wastewater treatment plant, totalling around 870,000m³s.
Nearly 300m halls were excavated for the treatment tanks, each more than 20m wide and around 22m high. The company has also excavated 17 elevator, ventilation and maintenance shafts, as well as 700m of wastewater inflow tunnels.
Helsinki Region Environmental Services Authority executive director Raimo Inkinen said: “The Blominmaki 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.”