A densely built urban environment sets strict requirements for both noise and vibration. The blasting required by the excavation work must be carried out within the permitted vibration limits and scheduled to minimize the disturbance caused to residents by noise. Moreover, in residential areas, environmental safety is of paramount importance, alongside the safety of workers.
Pohjolan Kalliotyö Oy, which is now JIITEE Louhinta and part of the JIITEE Työt Group, acted as a subcontractor for Destia in the excavation and reinforcement of a sewer tunnel in Helsinki city center. In total, about half a kilometer of tunnel was excavated, including a vehicular tunnel.
"The most challenging aspect of such projects carried out in an urban setting is the consideration that must be given to the built environment. The excavation and reinforcement of a tunnel that has its start point by the edge of a street requires coordination of the busy traffic in the area and the different work phases," says Henri Jokitalo, JIITEE Työt site manager.
Helsinki Region Environmental Services
Excavation and reinforcement work in the tunnels, transportation of excavated stone
20 professionals
Blominmäki waste water treatment plant is located in Espoo and treats the waste water of 400,000 residents. The treatment plant, which is located mostly underground, has been in operation since 2022. For the waste water treatment plant, about 20 km of sewer tunnels were excavated from different directions in several different sections.
The Malminmäki sewer tunnel section, built in connection with the construction of the treatment plant, was completed in 2018–2019. JIITEE Louhinta, then operating under the name Pohjolan Kalliotyö, carried out the Malminmäki project. It involved excavation and reinforcement work as a subcontractor for Kalliorakennus-yhtiöt Oy. In total, about 1.5 km of tunnel was excavated, including a vehicular tunnel.
"At the start point of the tunnel at the ground level, more consideration needed to be given to the environment," says Jokitalo, explaining a common challenge related to construction in an urban setting. Careful planning and precise scheduling ensured that the work could be carried out safely and that the impact on the surrounding buildings and their occupants was minimized.
The Finnoo II project, encompassing the southernmost section of the tunnel, was carried out as part of the earthworks and excavation of the Blominmäki wastewater treatment plant's intake and discharge tunnels. The main contractor for the project was the consortium TYL FMS, which consisted of SRV Infra Oy and Pohjolan Kalliotyö Oy, now JIITEE Louhinta.
In the project, around four kilometers of tunnels were excavated deep into the rock and reinforced, and pumping stations were built between 2019 and 2021. The contract also included the transportation of the excavated stone out of the tunnels. Normally, a single blasting operation can advance a tunnel five meters, but because of the greater constraints on blasting in an urban environment, progress was more limited in parts.
In addition to the urban, residential environment, the need to coordinate the Finnoo II project’s work phases with the construction work of the new metro station posed challenges. In joint meetings held with the other parties, schedules were agreed so that none of the projects interfered with each other's progress.
"For example, when concrete casting was going on at the metro worksite, blasting had to be planned so that it did not take place too close to the casting site. We also took into account transportation to the metro worksite, which was handled through the same tunnels," says Jokitalo, explaining how the two different sites were coordinated.
Experience and expertise play a key role when it comes to bedrock construction in residential centers. JIITEE Työt has more than two decades of experience in excavation and reinforcement work where traffic, people, buildings, and sometimes other construction sites underway in the area at the same time must be taken into account.
Our skilled staff and versatile equipment ensure that work can always be carried out flexibly, safely, and in line with the requirements of each site.
We are able to work even in the most demanding conditions and if necessary, innovate completely new solutions to efficiently carry out the work. So don’t hesitate to contact us when you need a professional on site.
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