Layers of rock have traditionally been used to provide scour protection in front of quay walls. Open Stone Asphalt mattresses provide a thinner and more secure protection layer.
At Vulcaanhaven scour protection was provided to protect the quay wall against the high forces generated by bow-thruster propellers. Instead of a traditional 1-2m deep rock layer, the specified solution was to use 0.2m thick OSA mattresses. This resulted in less excavation and a reduced depth of sheet piling necessary.
10,000 m2 OSA mattresses were placed. Individual mattresses weighed up to 150 tonnes and were placed using GPS and checked by divers.