Dredging delivers a dream on the river
The Watermaster can undertake both suction dredging and backhoe dredging, whilst also having the capability to perform pile driving works.
Dredging is helping the city of Joensuu in eastern Finland transform an old contaminated sawmill area near the city centre into a modern housing district.
But before the building could startt, the whole area must be thoroughly restored after more than a century of heavy industrial useage. From 1871 until 1988 a sawmill operated on the banks of the river Pielis close to the city centre in an area called Penttilä. The soil and storage bay at Penttilä had become severely contaminated with heavy metals and other toxic materials.
The city had bought Penttilä in 2008 and was planning to turn the area into a modern, eco-friendly housing district for some 3,000 to 4,000 residents over the next 20 years, but first the area had to be thoroughly cleaned.
Total restoration costs have risen to some €21m in what has become one of the biggest restoration projects ever carried out in Finland. The name of the project is ‘A dream at the river mouth’. The Penttilä district encompasses 40 hectares and more than 500,000 m3 of soil was must be cleaned.
The old storage bay next to the river had been kept open during the winters by directing the flue gases from the nearby plant to the bay. This inevitably caused the accumulation of vast amounts of heavy metals in the bottom sediments. The size of the bay is some 3 hectares and the water depth varies from 2m to 4m. It was the most polluted spot in the area its cleaning was considered to be the most challenging part of the whole restoration project.
The bay is shallow and hard to reach with traditional dredging machinery so after thorough trials, the versatile Watermaster dredger was chosen as the best option for working the site.
Watermaster is a Finnish made, serially produced versatile dredger which can undertake both suction dredging and backhoe dredging, whilst also having the capability to perform pile driving works. Watermaster can ‘walk’ in and out of the water without crane assistance and it moves independently in the water as well, minimizing the need for support machinery and manpower.
The contractor has operated all the previous Watermaster generations but is now using the latest model, Classic IV, the fourth generation of the original Watermaster concept. The new Classic IV will work to a greater depth, has a larger boom, enhanced stabilisation, and a more luxurious cabin.
The Watermaster has been suction dredging vast amounts of contaminated sediment from the bay. The material is pumped into geotextile tubes to separate the sediments from the water. Sediments are left to dry for about a year and will then be transported for further processing to the nearby waste treatment plant. A small marina will be built to the storage bay area later on.
The cleaning of the whole area is to be completed this year and the house building phase can begin in 2012. Penttilä should be receiving its first new residents in 2013 as new buildings continue to rise for a further two decades.
By the end of the project, Penttilä will have been transformed from an industrial wasteland into a modern, verdant and desirable new residential area, which will undoubtedly attract new residents to live at the ‘mouth of the river’.
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