Another European beewulf (Philanthus triangulum)  female that passionately started digging of what seemed to become a nest on the digger wasp hill. After extensive digging apparently the spot did not satisfy and she left.
Up until now none of the wasp digging in the hill have finished their nest, which raises the question why. My presumption is the sand is still to loose making tunnelling difficult.
References1 Nederlands Soortenregister