Rock Mechanics and Tunneling Design

Salmisaari Coal Storage

The four underground coal silos built in connection with the Salmisaari Power Plant in the early 2000s are located at a depth of 120 meters below sea level. When completed, the Salmisaari underground coal storage facility was the first of its kind in the world. The silos are 65 meters high, 40 meters wide and can accommodate 250,000 tons of coal.

The shape of the storage silos was a result of a shift to full automation. The cylindrical coal silo allowed for the use of gravity in the handling of the coal and it was also optimal for rock mechanical reasons. As a result of situating Salmisaari’s coal stores underground in the rock, the former surface coal field was released for commercial and office use.

Helen Oy is committed to phasing out the use of coal. Coal from the Salmisaari Power Plant is planned to be replaced by 2029. We look forward to seeing how Salmisaari’s underground facilities will be used in the future!

Kakola Heat Pump Plant

The Kakola Heat Pump Plant uses the waste heat from the Kakolanmäki Wastewater Treatment Plant and produces both district heating and district cooling for properties in Turku. So the heat pump plant gets its energy from a renewable energy source!

The Kakola Heat Pump Plant has been excavated in the rock in connection with the Kakolanmäki Wastewater Treatment Plant. Upon completion, the heat pump plant reduced the consumption of fossil fuels and greenhouse gas emissions in the area, as it could partially replace the use of coal at the Naantali Power Plant.

ONKALO® Research Facility

The underground ONKALO® research facility, which extends to a depth of 450 meters, provides valuable information on the suitability of the Olkiluoto bedrock for final disposal. The bedrock is studied geologically, hydrogeologically and geochemically, among other things. The site is excavated using the traditional drill-blasting method. Research, surveys and monitoring of conditions can be conducted from ONKALO® without disturbing the construction of the disposal facility.

Inside, ONKALO® looks like this!

ONKALO® is a registered trademark of Posiva Oy

Viikinmäki Wastewater Treatment Plant

The Viikinmäki Wastewater Treatment Plant, built mainly inside the rock, was commissioned in 1994 and is the largest wastewater treatment plant in Finland and the Nordic countries.

The Viikinmäki Wastewater Treatment Plant process is based on the activated sludge method, in which the organic matter from the sludge is digested, producing energy.

Rockplan has been involved in both the original design of the Viikinmäki Wastewater Treatment Plant as well as in its later expansion phase. In the expansion, space was excavated for a new biological post-filter and a new treatment line, keeping the treatment plant is in operation throughout the excavation. The expansion increased the plant’s nitrogen removal capacity to the level of 70%, as required by the authorities.

Kittilä Mine Main Level 900

The design of the maintenance level of the Kittilä gold mine is currently the deepest ongoing project at Rockplan. The new maintenance level, to be excavated and built into the rock, will be located at a depth of 900 meters. The maintenance level will provide warehouse space and social facilities for personnel. In the future, this may be the location of the deepest workplace cafeteria in Lapland!

Sewage Tunnels at the Blominmäki Wastewater Treatment Plant

The sewage tunnels of the Blominmäki Wastewater Treatment Plant consist of an inlet tunnel leading to the treatment plant and a discharge tunnel leading out of the treatment plant. A total of about 20 kilometers of inlet and discharge tunnels and associated access tunnels will be excavated.

In addition to the tunnels, the contract includes maintenance and emergency exit shafts that are critical for safety, the Suomenoja Acceleration and Drainage Pumping Station built within the rock as well as its associated above-ground shaft access buildings, and a challenging connection to the existing offshore tunnel. The offshore tunnel directs treated wastewater 15 kilometers to the sea.

Rockplan was also involved in the general design phase when a suitable site was sought for a new wastewater treatment plant in Espoo. There were five alternative locations under review.

The contracts are estimated to be completed in the summer of 2021. In 2022, the new Blominmäki Wastewater Treatment Plant will treat wastewater from 400,000 inhabitants in the Espoo, Kirkkonummi, Siuntio and West Vantaa areas.