Turku Region Waste­water Treat­ment Plant Ltd’s invest­ment comp­leted on schedule and below budget – new outlet pipe and UV plant inaugu­rated in May

Turku Region Wastewater Treatment Plant Ltd’s new outlet pipe and UV disinfection plant were inaugurated 23 May 2023. The UV plant was handed over to the customer in March 2023.

The new outlet pipe and UV disinfection plant mark a substantial improvement in the Turku Region Wastewater Plant’s capacity and reliability. The purification process is also more effective now with UV disinfection performed on the wastewater after the regular treatment process. As a result, the wastewater will meet hygiene requirements set for swimming water, and the hygienic environmental load on the Turku sea area is reduced.

Fimpec involved in Turku Region Wastewater Treatment Plant’s biggest ever investment

Fimpec PMO Oy was in charge of project management, supervision, safety coordination, cost control and project reporting to the customer’s management between 2020 and 2023. Several Fimpec experts from different service sectors participated in the project.

“We at Fimpec are honoured to have been able to work on such an extensive and unique project in close co-operation with the professionals at Turku Region Wastewater Treatment Plant Ltd and other parties,” says Fimpec’s Esa Kunnassaari, Head of Operations, Project Services, who was in charge of the project management services for the project.

Project completed on schedule and below budget

The purchases for the project were carried out as public procurement. The approved cost estimate for the project was EUR 48 million, and the final costs were around EUR 45 million. Despite the complex nature of the project, use of technology that was unproven in Finnish ground conditions and major changes in the global situation, the project was completed on schedule and below budget.

The outlet pipe was taken into full use in early July 2022, and the trial run of the UV disinfection plant began in January 2023. The UV plant was taken into use at the end of March 2023. The successful execution of this large-scale and complex project required close co-operation between several parties to reach the common goal.

“The outlet pipe project is a textbook example of successful co-operation between different stakeholders. Fimpec’s operations and competence contributed significantly to the planned completion of the project,” says Mirva Levomäki, Managing Director of Turku Region Wastewater Treatment Plant Ltd.

A first in Finland: pipeline installed using the microtunneling method without any disturbances

The new outlet pipe measures around 800 metres in length and has a diameter of 2.5 meters. The reinforced concrete pipe was driven into the ground using the microtunneling method. This is the first microtunneling project of this scale to have been carried out in Finland.

The pipe segments were jacked into the ground to a depth of approximately 8 metres. The method helped to minimise the carbon footprint and environmental impacts of the pipeline project as excavations were only required at the start and end points of the pipeline. The pipeline was jacked below municipal infrastructure and busy street areas without any disturbances.

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The launching shaft at the Turku harbour (left) and reception shaft at the Hansapuisto park next to the treatment plant (right)

The excavation required for the outlet tunnel and UV disinfection plant called for technical expertise and smooth communication with the residents and operators in the area

Another major component of the entire project was the excavation of the 300-metre outlet tunnel and the space for the UV disinfection plant. The UV plant and outlet tunnel were excavated adjacent to the underground treatment plant already in use. The outlet tunnel was excavated from the UV plant to the Hansapuisto park, where the tunnel connects to the 804-metre jacked pipeline. The outlet tunnel and pipeline total 1,104 metres in length. The space for the UV disinfection plant was excavated under challenging conditions close to apartment blocks and a day-care centre. The space extended partly beneath the operational day-care centre.

Any disturbance caused by the project were minimised through meticulous pre-planning, vibration monitoring and property audits.

“During the excavation, attention had to be paid to ensure the disturbance-free operation of the fully operational Kakolanmäki wastewater treatment plant. The excavation work was also scheduled according to the nap times of the day-care centre’s children. At this phase of the project, special attention was paid to informing the neighbourhood and addressing any questions raised by the local residents and operators,” says Kunnassaari.

The last part of the investment, the UV disinfection plant, was handed over to the treatment plant on 30 March 2023

UV disinfection in progress.

With the completion of the UV disinfection plant, the entire investment was completed in March 2023. The UV plant build adjacent to the Kakolanmäki wastewater treatment plant is used to disinfect the wastewaters before tunnelling to the outlet pipe. The effectiveness of UV disinfection has already been controlled through follow-up measurements, and the results are excellent.

“The project has involved special requirements throughout, and the network of experts operating at the site has done a fantastic job resolving them. Building the UV disinfection plant was part of a complex project in which the operation of the plant was integrated into the operational wastewater treatment plant,” Kunnassaari says.

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“Construction of the UV plant called for close interaction between the operating personnel of the treatment plant, Fimpec’s personnel and Skanska Infra, which was the contractor,” Kunnassaari explains.

“Our co-operation with Fimpec’s experts was excellent! As a representative of the customer, I can be very pleased with the outcome,” says Jarno Arfman, Technical Manager, Turku Wastewater Treatment Plant Ltd.

“The outlet pipeline and UV plant project gives Fimpec a major foothold in public sector plant projects,” says Fimpec’s Business Unit Director Jorma Paananen.

The innovative investment of Turku Region Wastewater Treatment Plant Ltd received recognition already during the construction phase:

For more information, please contact:

Esa Kunnassaari

Operative Director,
Project services, Helsinki



+358 400 702 621

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