Minor Applications – Developments of <½ hectare / <10 houses draining to an existing SW sewer

Network Impact

Anglian Water recognise that minor developments of less than 10 houses or ½ hectare represent amongst them, reasonably anticipated infill development as well as localised redevelopment necessary to maintain the viability of existing amenities. Such developments generally present minimal additional risk to the operation of the sewer networks. However, in some cases even a minor development can provide a pathway that exposes the sewer network to excess surface water or create new points of flood vulnerability. The result in these cases is to generate a level of operational risk that is disproportionate to the scale of the development and impracticable to mitigate.

Process

It is also recognised that minor development will not usually have the necessary resource to undertake complex and specialist detailed analysis expected of larger developments. We also note that the more precise conclusions derived from modelling would offer limited value to understanding the changes posed to sewer network operation by a minor development.

Similarly, there is likely to be very limited space on a minor development site, particularly brownfield sites, for attenuation that functions without the need to pump flow or a drainage field to be sustainably operated / compliant with Building Regulations.

A best practical option could be acceptable if the risk imposed to the sewer network is judged to be minimal. Therefore, the process for minor applications will employ a more empirical approach, examining the evidence to establish the pre-developed drainage characteristics of the site and identify the likely proportional changes presented by its development.

The following criteria will be used to determine our acceptance of a SW connection from minor developments:

Some analysis of the existing sewer network will be necessary and this would usually be a desk-top assessment of existing data. In some cases, asset surveys may be necessary to confirm the assessment.

As the developer is responsible for providing the appropriate surface water disposal infrastructure, work to determine the feasibility of a connection to a surface water sewer is considered to be part of the developer’s evaluation of surface water disposal options to a consented outfall.

Anglian Water will need to ensure the surface water hierarchy has been followed. We require you to provide evidence to prove that alternative disposal routes are unfeasible. If we are satisfied that, based upon evidence, no other option is viable then a connection point may be made, subject to the specific requirements to mitigate additional risk to the network.

Anglian Water will request a planning condition to ensure the agreed drainage strategy is implemented. If you have any queries on this process, please contact planningliaison@anglianwater.co.uk.

Network Reinforcement

Network reinforcement is not economically viable.

Other Drainage Infrastructure

There may be highway drainage within the vicinity of your development that could accommodate the additional flow. Subject to agreement with the Highway Authority, a connection for surface water may be made under the provisions of Section 115 of the Water Industry Act.

New drainage infrastructure and outfall

A new surface water sewer constructed to convey your surface water to a watercourse or as part of a SuDS scheme, where appropriate. Subject to the sewer being designed in accordance with the current version of Sewerage Sector Guidance, the sewer can be put forward for adoption by Anglian Water under Section 104 of the Water Industry Act 1991.

If the outfall is to a watercourse, the applicant may be required to obtain consent to discharge via the appropriate body in addition to approval of the drainage strategy from LPA. The applicant will also need to secure a Deed of Grant of Easement, in Anglian Water’s favour for the right to convey water into the watercourse in perpetuity from the riparian land owner, prior to a sewer requisition.

Installation of offsite sewers

If your site has no means of drainage without crossing third party land then you may be able to requisition Anglian Water, under Section 98 of the Water Industry Act 1991, to provide a connection to the public sewer or an approved outfall for domestic drainage purposes. Guidance on sewer requisition under Section 98 is provided here.

Alternatively, you may wish to enter into a works agreement in accordance with Section 30 of the Anglian Water Authority Act 1977. This will allow you to design and construct the public sewer using Anglian Waters’ statutory powers in accordance with Section 159/168 of the Water Industry Act 1991.

Sewer Adoption

SuDS are classed as sewers; therefore, subject to them being designed in accordance with the Design and Construction Guidance (DCG) Sewerage Sector Guidance, the sewer can be put forward for adoption by Anglian Water under Section 104 of the Water Industry Act 1991.

A pre-design consultation service is available if you would like to further advice on the adoptable standards for SuDS features. View details on our PDSA service.

As you may be aware, Anglian Water will consider the adoption of SuDS provided that they meet the criteria outline in our SuDS adoption manual. This can be found on our website. We will adopt features located in public open space that are designed and constructed, in conjunction with the Local Authority and Lead Local Flood Authority (LLFA), to the criteria within our SuDS adoption manual. Specifically, developers must be able to demonstrate:

1. Effective upstream source control,

2. Effective exceedance design, and

3. Effective maintenance schedule demonstrating than the assets can be maintained both now and in the future with adequate access.

If you wish to look at the adoption of any SuDS then an expression of interest form can be found on our website.