ENCI (Eerste Nederlandse Cement Industrie - First Dutch Cement Industry) is a Dutch company based in Maastricht, where they dig marl out of the hill St Pietersberg to make cement. The dug-up earth is used to make a hill called d'n Observant. There are plans to fill the hole in St Pietersberg with water to change it into a water recreation area. A pair of Eurasian Eagle-owls have been nesting at the ENCI quarry since 2001. This is one of the most West European known nesting sites for the bird.