09Jun 2020

A guide to the DCG

David Strang, Water UK


The SuDS community has rightly taken a lot of interest in the new approach to sewer adoption that water and sewerage companies (WaSCs) have developed. For the first time, national standards have been set out for the adoption of sewers which are not traditional, piped surface water sewers-many of which fall into the category of SuDS.


The essence of this approach can be found in a new document, the “Design and Construction Guidance” or “DCG”. This has been published by Water UK on behalf of its WaSC members in England and can be found here.


But what is the DCG and what does its publication really mean for local authorities, developers, drainage engineers, landscape architects and others involved in designing, approving and installing SuDS on new developments?


For nearly 100 years, WaSCs and their predecessors (local authorities) have been able to agree to “adopt” new sewerage-in other words take over responsibility for sewerage assets built by others so that they become part of the national sewerage network and are looked after as such. Many, but not all developers will take advantage of this option as it offers clear benefits to householders knowing that their drainage is in the hands of an enduring body with significant experience of running and maintaining sewerage assets.


WaSCs have understandably insisted that if they are to take over assets for the long term, these need to be built to the standards they lay down. For many years, those standards have been published through the “Sewers for Adoption” or “SfA” series-the last one of which was SfA 7, published in 2010.


So, offering a sewer for adoption was a voluntary act and the development of suitable construction standards was equally a voluntary act for the WaSCs.


The second half of that equation has now changed both for water and sewerage as a result of the implementation by Ofwat of an adoption code. This requires WaSCs to devise procedures, service levels, adoption agreements, redress provisions and a formal change control mechanism. The code also requires WaSCs to publish “Design and Construction Guidance for all aspects of Contestable works”. “Contestable works” includes most sewers built for new developments.


All this new documentation has been prepared in consultation with a range of stakeholders and has been vetted and approved by Ofwat.


Compliance with this new framework is mandatory for all English WaSCs (the position being different in Wales and Scotland). A parallel arrangement is being developed for the adoption of water assets and that is expected to come into force later in 2020.


If therefore a party wants to have its assets adopted by the local WaSC, it is now the DCG, which came into effect in April 2020, that governs the standards to which the asset must be built. There is only limited room for local variation.


As mentioned, for SuDS practitioners, the interesting element of the DCG is the incorporation of rules governing the adoption of certain types of sustainable drainage asset.


Note however that the underlying legislation, the Water Industry Act 1991, has not changed and only assets meeting the legal definition of “sewer” under that Act can be adopted. But, if your asset is a sewer that meets the definitions in the DCG, you are entitled to insist on its adoption by the WaSC.


In order to supplement the very sparse legal definition of a surface water sewer, the WaSCs have developed some further guidance which can be found here.


This sets out both positive and negative criteria for assets to be adoptable and also provides information on the extent of adoption and adoptable asset types.


The positive criteria include the following:


  • It is constructed to drain a building or yard
  • It has a channel
  • It conveys and returns flows to a sewer or waterbody
  • It has an effective outfall Where there are disputes on adoption, this is a matter for Ofwat to resolve.


This background does explain why the WaSCs have been limited in the extent to which they can promote the multiple benefits of SuDS. While these are referred to in the DCG, they cannot be the primary focus of the WaSC-its interest legally is in fulfilling its sewerage functions under the legislation. Quantity not quality is necessarily the main interest.


The intention of the WaSCs is that their approach will dovetail with the approach of the Local Planning Authority when approving SuDS as part of their planning function. It is for the LPA to approve the overall design and in doing so, it can now rely on the WaSCs’ standards, included in the DCG, to assist with the question of adoption. An awareness on the part of LPAs as to the content of the DCG can only be helpful in allowing the approval of SuDS which will meet the requirements of the local WaSC.


While most interested parties see the development of these new standards as positive, it does still leave open the possibility for developers not to offer their sewerage for adoption at all. While exact figures do not exist, it seems that over 50% of all such assets are not adopted. Is it not time for the mandatory adoption provisions of the Flood and Water Management Act to be brought into force?”

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