AQW 22143/17-22


Mr Andrew Muir
Alliance Party
North Down


Tabled Date: 09/09/2021
Answered On Date: 20/09/2021
Priority Written: No


Question:
To ask the Minister for Infrastructure what metrics NI Water uses to assess whether there is sufficient capacity in the water and sewerage network for new development proposals.


Answer:
NI Water’s wastewater treatment works are each designed to treat a specific population equivalent. The Northern Ireland Environment Agency regulates these works and issues each with a discharge consent, which sets out the discharge standards to be met.
NI Water closely monitors each wastewater treatment works to ensure that they meet the appropriate levels of treatment set by the Northern Ireland Environment Agency; that the required monitoring and reporting is carried out; and that they meet the specified numeric compliance levels in line with the discharge consent. In addition, the population equivalent load of each works is monitored against its design capacity, to identify available treatment capacity.
NI Water uses Drainage Area Plan Models, and where those are not available, a Capacity Mapper Digital Tool, to assess a catchment’s ability to receive wastewater discharges. These models, which are calibrated and signed off by the Northern Ireland Environment Agency, are constructed using current catchment and wastewater pumping station records, CCTV surveys and flow and discharge monitoring results. These digital models indicate compliance of NI Water assets with discharge standards and indicate areas of out-of-sewer flooding and manhole surcharging.
Each new proposed development will have an associated population equivalent load and NI Water considers this against the current available wastewater treatment capacity of the nearby works. If wastewater treatment capacity exists at the works and the additional load will not have an adverse effect on the sewer network and receiving waters, then new connections may be permitted.
When a wastewater treatment works has no available headroom capacity or the sewer network is operating above its design capacity, negative planning responses may be made to the relevant planning authority. However, NI Water will still provide positive planning responses in catchments where a proposal has extant planning approval, is deemed ‘like for like’ or where the development proposal results in reduced hydraulic loading.
These careful considerations help to ensure that no additional connections to the sewer network are permitted, that would result in significant risk of environmental harm and disamenity including pollution, flooding and a detrimental impact on existing properties.
NI Water advises all developers to avail of its Pre-Development Enquiry (PDE) process as early as possible in the design stage to allow capacity and other water and wastewater issues to be discussed prior to the submission of a formal planning application. In many cases, the PDE will help inform developers, and shape their proposals, taking into account any existing capacity issues or other constraints.