The city of Zadar (Croatia) is expanding its sewage system in order to improve water quality and to protect the coastland from pollution. The Zadar gravity collector for wastewater discharge comprised three microtunnelling crossings in the city. Two crossings of 99 meters and one crossing of 137 meters were completed by an AVN 1000 HR (Diameter 1,2950 mm). The AVN was specifically designed for microtunnelling in hard rock conditions and handled the hard limestone with UCS from 27MPa of up to 196 MPa successfully. The AVN 1000 HR is equipped with a stronger main bearing for high contact forces of 1,110 kN and a main drive for high rotation speed, allowing a maximum of up to 17 rotations per minute. The cutting wheel is specifically designed for hard rock, with wear-resistant cutter discs with tungsten carbide inserts.