MORE OUTLET PIPE CAPACITY, LESS ENVIRONMENTAL impact FOR THE SEA
The outlet pipe project of Turun seudun puhdistamo Oy helps mitigate climate change and updates the company’s purification processes and resilience. Started in 2018, the project is set to be completed in the spring of 2023.
The Kakolanmäki waste water purification plant’s waste water outfall system has insufficient capacity and it overloads during heavy rain. The plant also lacks a backup outfall system, which makes it ill-prepared for emergencies. Turku gains some 2,000 new citizens annually, which increases the amount of waste water in the sewer network. Meanwhile, climate change will bring more rain and increase the frequency of exceptionally heavy rain, adding more storm water. The sea level is also expected to rise, which limits the current outfall system’s capacity.
Once the outlet pipe project is completed, the plant will be able to operate at full capacity during exceptionally heavy rain and high sea levels. The purification plant’s resilience will also be improved with the old outfall system remaining as a backup for handling maintenance and disruptions. A new UV disinfection facility will also be built at the plant. The project will significantly improve the sanitary quality of the waste water released into the sea in the Turku area. Furthermore, the plant’s turbine will generate eco-friendly energy from the waste water flow.
Excavation and tunnelling were chosen as the working methods. Tunnels only require open cuts for their start and end and cause the least nuisance for both traffic and residents. The technology’s carbon footprint and energy consumption are also considerably lower than those of fully open excavations. Another benefit is that the water purification plant can operate normally during construction.
A cut-and-cover excavation was dug from the plant, continuing into a tunnel that terminates in the port basin. Excavation for the UV facility and outlet tunnel began in October 2019 and was completed in March 2021. The work was carried out from inside the plant. Tunnelling began in February 2020 with the excavation of the start and end cuts. The pipe’s jacking, microtunnelling, was carried out between July and August in 2020, and the jacking contract was completed in April 2021. The construction of the UV facility in a cavern dug out inside the plant started in May 2021. Partial use of the outlet pipe started towards the end of June and full-scale operation started in early July in 2022. The project is set to be completed in the spring of 2023.
The project was granted Blue Project-certified funding by the Nordic Investment Bank. The jacked section of the project has received two prestigious awards: the project was issued the Vuoden työ 2021 award by the Finnish Society for Trenchless Technology and it shared second place in the RIL-Palkinto 2021 competition. In addition, the project was among the finalists in the international Ground Engineering Awards 2022 competition, in the International Project of the Year series.
Turun seudun puhdistamo Oy sends out regular communications about the project and organises press conferences, as necessary.
Project management and monitoring: Fimpec PMO Oy
Design and planning: AFRY Finland Oy
Procurement legal: Procurement Partners Ltd
Excavation contractor: Kalliorakennus-Yhtiöt Oy
Excavation vibration consultants: Forcit Consulting Oy
Jacking contractor: Ward & Burke Construction Limited
Equipment supplier: Hyxo Oy (UV)
Equipment supplier: Saahkarin Kone Ky (turbine)
Equipment supplier: Tecalemit Flow Oy (diversion channel floodgates, stop dams, valves, lateral adjustment flanges, flexible couplings, and pipe clamps)
Equipment supplier: Oy Lining Ab (turbine sluice gates)
Worksite services: Ramirent Ltd
UV plant contractor: Skanska Infra Oy
Final excavation restoration: V-S Asfaltti Tiimi Oy
Turun seudun puhdistamo Oy advocates for a cleaner Baltic sea as part of the Baltic Sea Action Plan 2019–2023 of the cities of Helsinki and Turku.
Mirva Levomäki, tel. +358 40 712 6241
Managing director, Turun seudun puhdistamo Oy
Jarno Arfman, tel. +358 40 712 6231
Technical manager, project lead, Turun seudun puhdistamo Oy
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