Problems with water during tunnel construction

Road and especially tunnel construction represents a great threat to karst underground water pollution. Being aware of that threat and recognizing the karst as a significant drinking water reservoir, karst water protection is considered as one of priorities in Croatia. Present paper describes possible the example of technical problems during planning of underground karst water protection in the zone of drinking water catchment at the locality of construction of tunnels “ Javorova Kosa” and “ Pod Vugleš” . It describes difficulties of designing tunnels in karst according to previous research works, because of numerous surprises that are hidden in the karst. In our example, research works have shown considerable amounts of underground water so several wells were designed for its lowering. The wells drilling and tunnel breaking through have found the opposite since the water quantity in wells and tunnels was minor.