More than 166,000 square metres of surface water drainage has been removed from Northern Ireland’s combined sewer network since 2023, creating sufficient wastewater capacity to support approximately 600 new homes.

NI Water has invested £5 million over the past three years in its Stormwater Separation Programme, working with framework partners Atkins Réalis, AG Wilson Civil Engineering and CivCo to identify priority areas and install dedicated stormwater infrastructure.

Much of the wastewater network serving the region uses a single combined system, where stormwater from roofs, drains and gullies travels through the same pipes as foul sewage to treatment works. Robert McLean, NI Water senior project manager, explained that because stormwater does not need treatment, diverting it away from combined sewers improves operational efficiency and, in some locations, removes a barrier to development.

The programme begins with extensive investigations, including CCTV surveys and drainage assessments, to locate historic misconnections before construction begins. This ensures only clean surface water is redirected.

Areas already seeing long-term benefits include Derry/Londonderry, Newry, Ballymena, Portadown, Belfast, Newtownabbey, Antrim and Coleraine. The works have delivered improved network resilience, better environmental protection and additional capacity for economic growth, according to NI Water.

McLean stated that the investment reflects NI Water’s commitment to essential infrastructure upgrades that support communities, protect the environment and enable sustained regional growth.