abstractright abstractright

Rock construction of the Metsä-Sairila wastewater treatment plant, Mikkeli, Finland

A new underground wastewater treatment plant will be built  in the Metsä-Sairila area in Mikkeli. Building the treatment plant is a part of the larger EcoSairila 2020+ concept, where a new kind of business, research and development environment linked to circular economy is being created in the area in connection with the existing waste centre.

The completed treatment plant will be one of the most modern wastewater treatment plants in Europe and the whole world. The treatment plant is the first in Finland to use membrane bioreactor (MBR) technology in wastewater treatment. In MBR, clean water is separated after effective biological-chemical treatment by filtering the water through a membrane with very small pores. A better treatment result can be achieved with the membrane technology compared to traditional methods. The process requires less space than usual, which means that the investment costs are lower and the construction time shorter.

More information about the project is available at the treatment plant’s website: http://mipu.fi/materiaalipankki/

You can follow the progress at the worksite on YouTube: “Mikkelin uuden jätevedenpuhdistamon uutiset” (News from the new Mikkeli wastewater treatment plant)

In the project, Sito Rakennuttajat acts as the client’s developer consultant. During rock construction, Sito Rakennuttajat is responsible for the duties of the project manager, project engineer and safety coordinator as well as worksite supervision. If necessary, skilled rock construction planners from Sito will also be involved in the project to carry out expert tasks.

Sito Rakennuttajat has strong experience in different underground construction sites and has put together a capable workgroup for this demanding project to fulfil the client’s requirements and ensure that work progresses smoothly between the different stakeholders.

The demanding and multifaceted nature of the project necessitates nearly daily site supervision presence on the worksite and reporting of the onsite situation to the Client regularly each week. The safety coordinator makes weekly rounds of the worksite and writes reports into the project bank.

The developer consultant acts as the chair and takes minutes in site meetings. In addition, the situation at the worksite will be reported to the client’s project management team monthly.

The wastewater treatment plant includes a solid volume of approx. 160,000 m3 of underground excavation and approx. 8,500 m3 of quarrying, and there are three shafts of approx. 2,400 m3 in solid volume.  Approximately 30,000 metres of rock area probing and grouting holes will be drilled, with an estimated 210,100 kg of cement used in the grouting. The rock areas will be reinforced with approx. 14,000 reinforcement bolts and 6,000 m3 of shotcrete. The scope of the rock construction will include approx. 2,700 m3 of concrete structures.

The wastewater treatment plant’s rock construction started in September 2016, and it will be completed in June 2018.

Special features of the project include:

  • Modern treatment technology
  • Several stakeholders
  • One of the largest/the largest investments ever in the area.
  • The first large-scale underground rock construction work in the area


  • Mikkeli Water Utility, contact person: Reijo Turkki, Director of Mikkeli Water Utility


  • Main design: Ramboll Finland Oy
  • Treatment plant design (underground facilities, process electricity and automation design): FCG
  • Treatment plant design (process design, aboveground facilities, area and geotechnical design, building electrical and fire technical design): Ramboll Finland Oy
  • KAT rock structure design: Kalliosuunnittelu Oy Rockplan Ltd
  • RAK structural design: (interior tunnel structures) FCG
    (mouth and other aboveground structures) Ramboll


Main contractor /Rock construction:

Lemminkäinen Infra Oy