Water companies are considering their role in relation to the adoption of Sustainable Drainage Systems (SuDS) after government decided not to implement Schedule 3 of the Flood and Water Management Act 2010 – which would have provided a comprehensive regime for surface water drainage.

This work, a revision of the existing but voluntary Sewers for Adoption manual, would have resulted in a mandatory manual – version SfA 8.

The work was incorporated within the implementation of Ofwat’s Code for Adoption Agreements which requires the water sector to prepare guidance on both water and sewerage asset adoption.

That guidance must include Design and Construction Guidance (DCG) and it is this document which contains details of the water sector’s approach to the adoption of SuDS which meet the legal definition of a sewer.

Following the Pitt Report in 2008, a number of enquiries have identified that one of the major impediments to the increased use of SuDS is uncertainty about long-term maintenance. While the legal requirements under which water companies operate will not allow all SuDS to be adopted by water companies, the new mandatory approach should see a significant increase of SuDS assets being adopted by water companies as sewers.

On 1 April 2020 the new sewerage adoption arrangements came into effect.  In order to allow a smooth introduction of the new arrangements alongside various other initiatives which are to take effect on that date, reporting against most of the new performance metrics is going to be delayed for a maximum of six months from 1 April, as noted in the Sewerage Sector Guidance document (SSG).

Published principles, to deal with the transition between the current Sewers for Adoption regime and the new SSG, state applications using current standards will continue to be accepted for six months from the implementation of the SSG on 1 April 2020.

For schemes currently being developed, which involve SuDS, it would to be beneficial for the new SSG standards to be followed – developers are strongly encouraged to contact their local sewerage undertaker to discuss this further.

SURFACE WATER SEWERS AND SUDS DESIGN

For many years, water and sewerage companies have been recognised as the most suitable owners and operators of the country’s sewerage network. The legislation applying to water companies supports this and every year, using that legislation, responsibility for sewers for many new developments is transferred by a site developer to the local water and sewerage company.

Over recent years, both government and other interested parties including drainage engineers and environmental NGOs have come to the view that traditional sewerage systems, relying largely on pipes and hard engineered structures, are not always the best way to deal with the drainage of surface water.

It may be preferable if surface water – rainwater falling on hard surfaces like roofs and hard standing around houses – is left to infiltrate into the ground or returned to a watercourse, rather than flowing directly into a piped sewer system.

The aim is to mimic natural processes through a range of techniques which are often described as sustainable drainage systems (SuDS). Not only will this reduce the chances of the sewer pipes overflowing in times of heavy rain, but it could create additional headroom in the sewer system to allow for more housing development. Such systems often provide other benefits as well, such as enhancing the amenity value of an area by creating green spaces and absorbing certain pollutants in surface water.

A number of water and sewerage companies have already taken steps to encourage this approach, but there has until now been no national approach on the part of the water and sewerage companies towards the transfer to them (technically called “adoption”) of these types of sewer.

A new brochure Sewerage Sector Guidance (SSG) provides an introduction to new rules on surface water sewers that will apply to all water and sewerage companies in England. These new rules, which are part of the Sewerage Sector Guidance documentation has been approved by Ofwat under its Code for Adoption Agreements, was implemented as of the 1st April 2020.

The rules, which can also be found in the Design and Construction Guidance (DCG) implemented under the Sewerage Sector Guidance, will allow English water and sewerage companies to adopt a wider range of sewer types, including those with sustainable elements, than they have done to date.