Underground wastewater treatment plant in Mikkeli, Finland

Mikkeli Water Utility is developing a new wastewater treatment plant, which will be one of the most efficient and modern in Europe.

Mikkelin jätevedenpuhdistamo / Mikkeli wastewater plant

Mikkelin jätevedenpuhdistamo / Mikkeli wastewater plant

The contract covers excavation of the underground wastewater treatment plant in Metsä-Sairila, Mikkeli, grouting, rock support works, as well as the construction of a drive ramp and concrete structures in the cavity.

Mikkeli Water Utility is responsible for planning the wastewater treatment process and the procurement of equipment. We will bring our special expertise in underground construction and excavation to the project. The client’s reasons for awarding the contract to us include our proven track record of equally complex excavation contracts, such as the Viikinmäki wastewater treatment plant in Helsinki and the Blominmäki wastewater treatment plant in Espoo, both in Finland.

The project will involve excavation of a total of around 160,000 solid cubic metres of rock to make space for the new wastewater treatment plant. In addition to a staff of approximately 40, the construction site will employ two jumbo drills, three excavators and wheeled machines, a grouting vehicle and a shotcreting robot.

The project has made excellent progress, and is currently ahead of schedule. The rock engineering started in September 2016. By May 2017, the project had progressed to the blasting of tunnel top headings, shaft excavation, and reinforcement. The horizontal excavation also started in May, and the construction of concrete structures will start in August. The excavation and reinforcement will be completed in autumn 2017, and the concrete structures in spring 2018.

The new treatment plant is due for completion in 2020, and will serve a population of 69,000.

rock construction

water supply construction


Project name
Mikkeli underground wastewater treatment plant
Mikkeli Water Utility
Project status
Under work
Business segment
Tunnel excavation approx. 160,000 solid cubic metres, open excavation approx. 8,500 solid cubic metres Three shafts, approx. 2,400 solid cubic metres Rock chamber probing and grouting, approx. 30,000 metres drilled Cement used for grouting, approx. 210,100 kg The rock will be reinforced with around 14,000 bolts and 6,000 m3 of shotcrete. The rock engineering will use a total of approx. 2,700 m3 of concrete structures.