Traditionally the civil and hydraulic engineering sector has always made intense use of wood and steel. The use of these materials includes some disadvantages, such as maintenance, lifespan and the environmentally unfriendly characteristics. These drawbacks were a reason for the Delfland District Water Board to opt for the use of sustainable plastic. For the renovation of the Commandeurspolder banks, Delfland selected this environmentally friendly alternative.
Profextru manufactures Prolock, a sustainable, innovative soil and water barrier system. The plastic underwater piling was inserted over a distance of 1400 metres in the Noordvliet, along the Commandeurspolder. The piling was inserted in a slightly undulated embankment, which prevents clay and lava stone moving to the centre of the waterways, which could result in subsidence of the bank. Due to this construction, a small amount of water remains on the inside to allow fish and small aquatic animals to reproduce. Spearhead The choice for plastic complies with one of the most important spearheads of the Delfland district water board, sustainability. First and foremost, wood – when compared to plastic – has a much shorter lifespan. Moreover, it is much more complicated to insert wood piling, due to the many rocks on the bedding of the Noordvliet. Due to the heavier weight of steel, the question of how to insert the construction was raised. Plastic is much more flexible to work with. A local contractor uses a vibration method to insert the plastic screens under the water, and the piles are pushed into the soil by inserting the piles from a pontoon into the recesses in the profile, with a fixed gap, to create the required firmness.
Plastic characteristics The underwater piling is made from one hundred percent recyclable plastic, which can be recycled up to six times. As such it complies with the cradle-to-cradle principle. Each time plastic piling is manufactured, it will last a minimum of fifty years, which means that the total lifespan is a minimum of three hundred years. Furthermore, the piling is virtually maintenance-free: no corrosion will occur, as is the case with steel dam walls, and it is rot-proof and rodent free. Last but not least, because of the light weight of the plastic and the ease of insertion, the screen is very flexible to handle. As such no underwater insertion needed to take place, instead the plastic screens were simply interlocked based on the smart interlocking system. As such a solid connection is created, without the use of bolts.