Enough soil has passed through Jätkäsaari over the last ten years to fill the volume of tens of Finnish Parliament Houses together. Rock materials from the West Metro construction and soil dredged from the seabed are reused in this new Helsinki district under construction.
The asphalt field freed from the Jätkäsaari harbour of Port of Helsinki began to be filled with various piles of soil and rock after August 2009. Each pile was designated to a carefully defined reuse in the area development.
“For example, most of the rock materials produced from the West Metro construction was taken to Jätkäsaari,” says Mikko Suominen, the coordinator for the City of Helsinki in charge of soil and rock materials.
The total amount of soil and rock materials is huge – 3 million cubic metres, which corresponds to the total volume of 30 Finnish Parliament Houses put together, or approximately 300,000 truckloads.
The City of Helsinki uses recycled soil and rock materials at all other large construction sites in addition to Jätkäsaari. Suominen coordinates the recycling operations at all Helsinki construction sites. His phone rings every now and then, as contractors building Helsinki keep calling and asking what to do with the soil and rock removed from construction sites. The other half of his duties comprises development: the City wants the soil and rock materials of Helsinki to be reused as efficiently as possible.
Over the last ten years, the western section of Jätkäsaari, which is Finland’s biggest residential construction yard, has served as an enormous soil and rock recycling site. At its biggest 10 years ago, the land area of the site was 20 hectares. The recycling site has shrunk as construction has progressed, and the last big pile of rock is likely to end up as landfill, most probably in 2022.
When the construction of Jätkäsaari got under way in 2010, the City was busy to find new solutions for the reuse of soil and rock materials. The City established the coordinator’s position that was filled by Suominen.
Suominen has fulfilled his duties well: the reuse of materials from excavation work has increased by nearly ten-fold. During 2014–2018, smart reuse of materials from excavation work has been promoted by a development programme, which has saved approximately 37 million euros and 5.3 million litres of fuel as well as reducing carbon dioxide emissions by 13,400 tonnes.
Dredging at Jätkäsaari was complicated further by the top layer of the former harbour’s water area, which was contaminated with hazardous substances. These soil materials could not be disposed of into the sea.
Clay from 4-hectare basins located at the current Saukonlaituri neighborhood of Jätkäsaari was found to be suitable for earthworks and foundations construction. The clay was dried and mixed with cement to improve its properties as a construction material. Today one of the many features in which clay from the seabed can be found is the mounds of the new park of Alakivenpuisto in Myllypuro. The recycling of the clay saved 2.5 million euros, as the treated clay would otherwise have had to be taken as far as Kotka to be dumped.
Smart planning also brings considerable savings in site preparation and foundation work. Recycled soil and rock can be reused here, too. A pile of rock equaling five Parliament Houses on the western waterfront of Jätkäsaari serves as a berm to strengthen the stability of soil. When construction at the site starts in a couple of years, the soil will have stabilized close to its final level. This produces savings in the construction costs of buildings and sites.
Helsinki has in just a few years become a pioneer in the recycling of soil and rock materials.
Abridged and translated from an original text by Petja Partanen