Question to the Ministry of Housing, Communities and Local Government:

To ask the Secretary of State for Housing, Communities and Local Government, what recent assessment she has made of the efficacy of the dry weather flow data for determining impact on waste water treatment works of increased housing.

The National Planning Policy Framework is clear that strategic policies should set out an overall strategy for the pattern, scale and design quality of places and make sufficient provision for infrastructure for transport, telecommunications, security, waste management, water supply, wastewater, flood risk and coastal change management, and the provision of minerals and energy (including heat).

Dry weather flow (DWF) at wastewater treatment works is the amount of wastewater (sewage) entering the works without any contribution from rainfall or snowmelt.

It is used to calculate the polluting load entering the works and to set environmental permits to protect the environment. DWF is measured using calibrated and independently certified and inspected flow meters 24 hours a day, 365 days a year.

Water companies must track flows entering the works in line with permit requirements and use this information to plan for growth.

Water companies must prepare, publish and maintain a Drainage and Wastewater Management Plan (DWMP, also called a Drainage and Sewerage Management Plan) setting out the actions they intend to take to secure wastewater service provision, now and into the future. These plans identify the current and future investment need to ensure sufficient capacity enables their assets continue to meet DWF permit compliance, and to address the pressures of growth and climate change. The next statutory DWMPs are expected to be published in 2027/8.