The renovation of the Nunnankatu stormwater pumping station, completed in spring 2025, was one of the most demanding projects carried out as part of the cooperation. Renovating this critical pumping station increased its capacity, improved energy efficiency and enhanced operational reliability.
Increased capacity for growing stormwater volumes
The renovation of the Nunnankatu stormwater pumping station was part of a broader project to improve the structures of Kaivokatu and drainage in the surrounding area. The capacity of the old pumping station needed to be increased so that it could handle rainwater and snowmelt more reliably.
– The renovation increased the pumping station’s capacity and improved its energy efficiency. The pumps were correctly sized with design rainfall levels taken into account, improving the station’s operational reliability even during periods of high stormwater flow, says Rami Pirkola, Water Services Manager at Naantali Water Services.
Comprehensive modernisation of the pumping station
The renovation included replacing the pumping station’s pressure pipeline and installing a new pump control centre. Both plastic welding and conventional welding methods were used for the piping work.
The acid-resistant stainless steel piping was prefabricated to precise measurements at ETH Group’s workshop in Eura. Completing as much of the fabrication as possible in advance accelerated the on-site work and helped minimise the pumping station’s downtime.
– The pumping station was comprehensively renovated and modernised. We prefabricated the acid-resistant stainless steel piping at our Eura workshop and then installed it on site. We also arranged the temporary bypass pumping required during the renovation, says Tuomas Hossi, Project Manager at ETH Group.
Reliable bypass pumping ensured effective water management
The timing of the renovation presented specific challenges in Naantali. Spring is a demanding period because of snowmelt and stormwater, so the temporary bypass pumping had to operate reliably throughout the project.
The city centre and the old town also needed to be ready before the busy summer and event season. The renovation therefore followed a strict schedule ahead of the events beginning in spring.
– The temporary bypass pumping was implemented extremely well, and the solutions had been carefully planned in advance. This allowed the pumping station to be returned to service as quickly as possible, Pirkola says.
Thorough advance planning, extensive prefabrication and reliable bypass pumping ensured that the renovation of this critical pumping station was completed according to schedule.
– The work progressed smoothly and was completed on time. Meeting the tight schedule required careful advance planning of both the work phases and the technical solutions, Hossi says.
One partner from commissioning to ongoing maintenance
ETH Group’s comprehensive service covers pumping station commissioning, electrical and automation work, ongoing maintenance and fault diagnosis. When the same partner is familiar with the pumping station from the renovation and construction stages onwards, the causes of potential faults can often be identified more quickly.
The required piping, pump, electrical and automation specialists are all available under one roof. The customer does not need to determine which contractor is responsible for a fault, while shorter communication chains help the work proceed more smoothly.
The renovation of the Nunnankatu stormwater pumping station improved Naantali Water Services’ ability to manage growing stormwater volumes. Correct pump sizing, modern technology and improved maintainability will support energy-efficient and reliable operation for many years to come.
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