The Strategic Tunnel Enhancement Programme (Step) is a deep-gravity sewerage system designed to collect wastewater flow of 1.9 million cubic metres a day from Abu Dhabi island and the mainland. Future wastewater collection needs, as anticipated by Plan Abu Dhabi 2030, can also be accommodated.

The programme sets a new benchmark in the region in terms of delivery and scale of construction. In addition to incorporating sustainable solutions, Step minimises environmental impact and disruptions to the community with the use of trenchless technology and large-diameter mechanised tunnelling at significant depths (25-80 metres below the surface of the ground).

A key benefit of Step is that it will facilitate the decommissioning of 35 pumping stations. As a result, valuable land will be made available for developmental use. By eliminating these pumping stations, potential odour problems will also be addressed.

Designed for a minimum maintenance-free life of 100 years, the new tunnelling system is considerably more reliable and robust than the systems it is replacing, with a much lower burden on operational budget and associated resources. It will also result in a reduced carbon footprint.