Rijkswaterstaat is having the broken dam in Maastricht closed with enormous quantities of large stones. These are brought in by ship from Wallonia, Belgium and then packed in huge nets that alone weigh 8.000 kilos. The nets are supplied from Rotterdam. May van de Kerkhof, director of network management Zuid-Nederland at Rijkswaterstaat (RWS), mentioned this as one of the options on Thursday during a visit to Maastricht.