To ask the Minister for Infrastructure for an update on NI Water's ongoing work to complete modelling of sewage spills in less densely populated areas.

The management of public wastewater infrastructure is an operational matter for NI Water. However, I have sought the requested information from NI Water and have been advised as follows:

NI Water generates modelled spill information for storm overflows using Drainage Area Plan (DAP) models and this sewage discharge information outlines the frequency and volume of discharges as predicted by its DAP models. The figures are effectively an annual average, based on long-term recorded rainfall data.

In May 2024, NI Water published on its website (Storm Overflows) predictive spill data for over 1200 storm overflows across 65 catchments (main cities and large towns), representing 50% of its storm overflows.

Modelling work is ongoing to complete DAPs across less densely populated areas in the North, covering approximately a further 650 storm overflows. NI Water anticipates that by the end of 2027, it will have predictive spill data for assets in catchments with a population of over 1,500.

The development of DAP models is not planned on the remaining storm overflows as these are in very low populated areas (less than 1,500 population) and the modelling of smaller catchments is often challenging as a result of low flows and smaller pipework, reducing the accuracy of predictive spill results.

For any future queries relating to operational matters, you should contact NI Water directly, through the Elected Representatives Hotline on 0345 300 6461 or through waterline@niwater.com

Making direct contact with NI Water will ensure that you receive the information in the shortest possible timeframe and make best use of limited public resources.