In August 2018 VRT inspected the tailwater side of the Imatra hydropower plant owned by Fortum in Vuoksi river. Previously diving inspectors had noted that in some places the structures were in poor condition. Fortum decided to take action to renovate the concrete structures near the draft tube outlets.
The area to be scanned was a good 7 hectares of river bottom, and 1.8 kilometres of vertical wall structures. VRT’s inspections allowed Fortum to see the real condition of the structures, how they are connected to the rock and what else lies on the bottom.
In the inspections VRT used multibeam echo sound for the underwater structures. In addition, laser scanner was used for the banks of the tailrace channel above the water surface.
Some of the structures in the Imatra hydropower plant are up to 90 years old. The blueprints are old and there might be even several different versions of them, so they might not tell how the structures really have been constructed, according to the Project Manager Tomi Jokiranta from Fortum. Nor are there enough photographic material from the time of construction to tell, how the now-underwater structures used to look like.
The information diving inspectors gather is very limited to the exact diving locations. With VRT surveys, Fortum got a good overview of what lies beneath the surface. After surveys like these, the divers can be sent to inspect the possible damages more closely.
VRT delivers the reports to their clients both as literary reports and as point cloud data. Photographs are also used for sightings above the water. 3D data is always delivered through web-based and easy to use Gisgro online service. The reports include all findings with their severity classification.
Fortum thought the inspection reports to be clear and high quality. They also complimented the cooperation to be fluent.
Jokiranta describes Gisgro as a good tool for presenting the survey reports inside the company. Fortum is likely to use the point cloud data in the repairs of the concrete structures mentioned earlier. The 3D data from the tailrace channel is also useful on water flow simulations.
Imatra hydro power plant
The Imatra hydro power plant, completed in 1929, is located in the centre of the city of Imatra. The hydro power plant is Finland’s biggest. Its output is 192 MW and head is 24 meters. One Kaplan and six Francis turbines. Average annual production covers the annual electricity use of 50,000+ households with electric heat.
Fortum is a leading clean-energy company that provides its customers with electricity, heating and cooling as well as smart solutions to improve resource efficiency. We want to engage our customers and society to join the change for a cleaner world. We employ some 9,000 professionals in the Nordic and Baltic countries, Russia, Poland and India. In 2017, our sales were EUR 4.5 billion and 61% of our electricity generation was CO2 free. Fortum’s share is listed on Nasdaq Helsinki. www.fortum.com
“The biggest benefit for us was that now we have outlined knowledge of what lays under the water in the tailwater side of powerplant. The blueprints of the old powerplants might be outdated, and it is difficult to implement successful renovation planning based on them.”