Hidden depths

Hidden away from Helsinki, between the forests and golf courses of Espoo, Finland, a huge underground construction project is under way. For the past two years, Lemminkäinen Infra Oy, the contractor in charge of the tunnelling, has been digging, blasting and excavating. As its part of the project nears completion, an entire network of caverns and tunnels exists beneath this beautiful expanse of Nordic countryside. The tunnels are being excavated as part of a major undertaking. The population of Espoo has grown by 10 times in the past 60 years, and as Espoo’s population grows, the facilities need to adapt. With that in mind, the Helsinki Region Environmental Services Authority is building an underground wastewater treatment plant in Espoo’s Blominmäki bedrock as part of its overall mission to help improve the environment. When the project is completed in 2020, it will be able to clean the wastewater of more than 400,000 residents. This is a big project, then, not only for residents now and in the future, but also for the environment. The new water treatment plant will be more efficient than the current one. In Finland, it has been illegal for a long time to transport untreated wastewater to the water system. Before the plant is constructed, the tunnels to house it must be excavated. It might seem more sensible to build something like this above ground, as that’s the more traditional way and it wouldn’t require the sheer amount of excavation work that’s taking place here. However, the increased initial effort is well worth it in the long term. Locating most of the plant underground is better for the surrounding landscape, for a start. The space can be used more efficiently, since building underground avoids the need to work around roads and existing structures, and in some cases wildlife. In addition, the facility is less exposed to the sometimes harsh environment of Northern Europe.

Planning during the project was a vital part of this contract, impacting every level of development. Meriläinen explains the method used: “In some caverns the excavation is even done in nine separate parts due to the big profile and high tolerances for excavation. We start with the top of the tunnel, then excavate the middle parts, and finally the sides.” Lemminkäinen uses the Sandvik iSURE software together with Sandvik DT1131i jumbos to manage the excavation process. Sandvik iSURE enables drill and blast plans to be designed and uploaded to the equipment, and the collected data can be analyzed after the excavation has taken place.

Tommi Mannelin is a computerized drill and blasting method (CDBM) engineer for Lemminkäinen, and he spends a lot of time with the Sandvik iSURE system. “I’ve been working with the system for seven and a half years, and the software certainly makes my job easier,” he says. “It saves time, and the driller doesn’t have to think about the task, as the drilling can be fully automated from the plans. The only real challenge is that sometimes the theory of a plan can be different to how it actually is in reality.” For optimal functionality, the system needs to be implemented in both the processes and the equipment. For this contract, Lemminkäinen chose two fully automated Sandvik DT1131i jumbos. Lemminkäinen had originally used the two rigs on another project. The Sandvik jumbos were originally delivered to Tampere for the Rantatunneli project, the longest road tunnel in Finland.

On an average week, Lemminkäinen excavates 14,000 to 15,000 cubic metres of rock. One week, the contractor removed 17,000 cubic metres. Any job of this size is only possible if equipment remains productive and reliable and the various contractors and stakeholders work together. Sandvik and Lemminkäinen have a strong relationship and have been partnering together for many years.

Soon the excavation work will be complete, and the framework will be there for the construction of the new underground water treatment plant. You won’t be able to tell from looking at this unassuming location from above, but something special is going on beneath the surface that is set to silently help an entire community.