Blominmäki sewer excavations

The excavation of sewage tunnels is mainly carried out after cave system excavations beginning from 2018. In Mikkelä, the sewage tunnels were excavated in 2017 from the Mikkelä access tunnel to south of the Espoo River. Look map at zoomable version (pdf, 15Mb)

See also: Frequently asked questions concerning sewer tunnel excavation

Mikkelä ll, Eestinkallio and Malminmäki

Kalliorakennus-Yhtiöt Oy is the main contractor for the three contracts for the construction and excavation of the wastewater treatment plant's inlet and outlet tunnels. The contracts are Mikkelä ll, Eestinkallio and Malminmäki. The southernmost part of the inlet and outlet tunnels, Finnoo, will be tendered later.

The inlet and outlet tunnels run from Mikkelä to Suomenoja. The total work time of the tunnels is 2/2018-3/2021. The tunnels are about 4.5 meters wide and 5.5 meters high. The length of both tunnels is about 7 kilometers. Tunnel excavation progress is about 10 meters per day.

In Mikkelä, tunnels were excavated already during the sewage treatment plant's excavation stage, so work can be started directly with tunnel excavation week 12/2018. In Eestinkallio and in Malminmäki, tunnels are also built and excavated for maintenance connections which operate as driving tunnels in the excavation stage. At these sites, the work begins with earthwork and open-cast excavations, which are scheduled to start week 14/2018. After the above-ground work is completed, tunnel excavation begins.

Working hours

Above-ground work:

  • on weekdays 7:00-18:00, and if necessary, also 18:00 to 21:00 (after 18:00 below 35dB)
  • on Saturdays 9:00 to 18:00 (under 35dB)

Underground work:

  • on weekdays 7:00-18:00, and if necessary, also from 18:00 to 22:00 (after 18:00 below 40dB)
  • weekends and midweek holidays from 9:00 to 22:00 (under 35dB)
  • if necessary on weekdays from 22:00 to 7:00 or on weekends and midweek holidays from 22:00 to 9:00 (less than 30dB)

Tunnel blasting:

  • Monday to Friday from 7:00 to 22:00
  • Saturdays from 9:00 to 18:00

The loading and transport of blasted rock from the tunnel:

  • weekdays from 7:00 to 22:00, weekends and midweek holidays from 9:00 to 22:00
  • if necessary on weekdays from Monday to Friday from 22:00 to 7:00, as well as weekends and midweek holidays from 22:00 to 9:00

The exact dB level refers to the indoor noise level of a residential building, which is measured when necessary.

Prior to the commencement of blasting operations and after their completion, Finnrock Oy will conduct a building review for the properties in the nearby area and damping of vibration-sensitive devices. The properties concerned will be contacted separately.

During the entire blast operation, Kalliotekniikka Engineers Oy will perform excavation vibration monitoring measurements in the nearest properties with continuously operating vibration gauges. The permitted vibration limits are based on the regulations in the blasting and mining industry that have been drawn up by the Ministry of Labor.

The progress of the excavation and any possible changes in the blasting will be carried out on the basis of the obtained measurement results so that no damage can occur. All excavation work is done in accordance with safety regulations and official regulatory guides.

Contact details of the main contractor for residents if required:

  • project manager Mikko Piirainen, 044 551 55 31
  • responsible site manager Juha Selin, 040 570 86 24
  • blasting expert Tapio Nummela, 040 066 21 01
  • site engineer Matti Westerlund, 050 439 61 43

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