Subsurface alignment of the STEP Link Sewers and the STEP Main Tunnel Subsurface view of the Al Wathba Pumping Station Tunnel Boring Machines eliminate surface disruptions Subsurface alignment of the STEP Link Sewers and the STEP Main Tunnel The depth of the STEP Main Tunnel varies from 35 meters on Abu Dhabi Island, to nearly 100 meters at Al Wathba Subsurface alignment of the STEP Link Sewers and the STEP Main Tunnel Subsurface alignment of the STEP Link Sewers and the STEP Main Tunnel Gravity flows eliminate the need for Pumping Stations STEP will handle the wastewater loads collected by other Capital Investment Programmes A Tunnel Boring Machine being lowered into a shaft Surface view of the Proposed Al Wathba Treatment Facility Previous