Anglian Water like any other Water and Sewerage Companies (WaSC) are responsible for the adoption and maintenance of public sewers and lateral drains. Public sewers with respect to surface water drainage are defined as sewers that drain roof and appurtenant yards. Flows from areas such as footpaths and highways are classified as highway runoff and are the responsibility of highway authorities. Similarly, flows from greenfield areas or gardens is classified as land drainage is usually the responsibility of the landowner or Internal Drainage Board where one exists.
WaSC are identified as a Risk Management Authority (RMA) within the Flood and Water Management Act (2010). The FMWA sets out the duties and responsibilities of RMAs in managing flood risk within developments and wider catchments. Among their duties an RMA has to work collaboratively with other statutory bodies in managing surface water flood risk.
Thus Anglian Water works collaboratively with Highway Authorities and LLFA in managing surface water flooding. Some key areas involve highway drainage improvement works and surface water flood alleviation schemes by LLFA. In both cases, the flows from these areas are classified as non-public flows and Anglian Water are not duty-bound to accommodate such flows within the public surface water network. By law the surface water network is not meant to accommodate non-public flows.
However, in the wider duties of working collaboratively to manage surface water flood risk, Anglian Water does cooperate with other RMAs to facilitate and provide solutions that have wider benefit to the overall surface water management within catchments. It is therefore incumbent on us to set out the evidence required when such non-public flows require a connection to the public network.
The following is the minimum information required to prove the need and wider benefits resultant from a connection of non-public flows to existing public sewer network:
• Technical Drainage report outlining the current wider surface water flooding problem within the area or catchment.
• The Technical Drainage report should highlight the before and after scenarios for the following critical design events; 1-in-1, 1-in-5, 1-in-10, 1-in-30 year. 1-in-30 year is the critical design for stormwater network where no flooding should exist.
• The wider benefits of the proposals to the existing public sewer network, including social benefits to the wider community.
• For highway improvements; consideration of SuDS solutions will be key to accommodate any new highway drainage into the public network.
