The 5th dredging sector
Dams and Damen DOP pumps
Product Director Dredging
Damen Shipyards Gorinchem
When we think about dredging, we divide the sector into four different areas: capital dredging, land reclamation, maintenance dredging and mineral mining. However, over the last few years a new field of dredging has emerged: one that will have an impact on the water and electricity resources of many countries around the world. This fifth sector involves dredging the reservoirs directly upriver from hydroelectric dams.
“With around 40,000 hydroelectric dams worldwide, this is a considerable market,” says Damen Dredging Product Director Olivier Marcus. “The majority of these were built in the 1960s and 70s, and many require urgent maintenance because they are not operating at full capacity. This has direct implications on supplies of water for human consumption and agricultural irrigation purposes, and, of course, affects the electricity generating capacity of the hydroelectric turbines in the dam itself.”
Analysing the problem…
“With time, sediment builds up near the dam; leading to the eventual blocking of the hydroelectric turbines.” This sediment needs to be removed, but there are a number of factors involved, all of which make the task more challenging. “By definition these reservoirs are located in mountainous regions which are quite remote,” explains Mr Marcus. “So the challenges include accessibility and fuel supply – getting a vessel and its fuel to the area in question. Sometimes the location is so high – up to 3,000 metres – that even the air is too thin for diesel engines to run smoothly.”
The challenges continue once the dredging vessel is launched and ready to get to work. A reservoir behind a hydroelectric dam can be up to 60 metres deep. “These depths are necessary to achieve the height differences required for optimum hydroelectric power generation,” he continues. Dredging at such depths requires ingenuity and experience; such smart solutions are Damen’s forte.
…to discover the solution
The answer lies in Damen’s DOP pumps. “These submersible dredge pumps are extremely versatile; operators can use different heads depending on the situation and material to be dredged. For example, harder compacted materials are dredged with a cutter head. If the reservoir has a lot of silt deposits, water jets are used to loosen the sediment, then a suction head to remove the material.”
With the DOP submersible dredge pump taking care of the dredging aspect, the next solution concerns the vessel itself. These are often modular pontoons which can be completely containerised. “The vessel and all its components – the motors, piping and winches – can fit into standard containers. So you can load everything in trucks and drive to the site.”
The modular aspect also has positive implications for the dredging depth. “It means that you can dredge, in principle, as deep as you like. We can increase the length of the dredging ladder and if that is not deep enough, we can lower the DOP pump on a wire to the required depth.”
Given the fact that there are around 40,000 hydroelectric dams in the world, the scope of operations for the fifth dredging sector is substantial. What’s more, the human impact – in terms of water and energy supply – has immense potential.