Changed surface area draining to a Combined via an existing POC

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Network Impact

The impact of surface water flow to a combined sewer significantly increases the risk of flooding and pollution from the receiving network and diminishes the ability of assets to operate within statutory enforced permitted limits. Anglian Water will use opportunities presented by new development to reduce exposure to pollution risk in the existing sewer network. As such, we expect new development to exploit all practicable opportunities to reduce surface water flow to the combined sewer network, in terms of volume and discharge flow rate. Our aim will be to obtain the maximum achievable benefit without introducing a need to pump flow.

Process

Anglian Water needs to ensure the surface water hierarchy has been followed. We require you to liaise with the relevant LLFA as they are the Statutory Consultee for all surface water drainage strategies on major development sites and are required by law to advise on the broader area drainage constraints. LLFA approval is an essential pre-requisite to Anglian Water accepting a SW drainage strategy. In the absence of an agreed SW drainage strategy Anglian Water would seek, through planning condition, to ensure surface water is restricted to the discharge rate advised in our policy.

Once approval in principle has been reached with LLFA detailed analysis can be undertaken to establish the receiving surface water network capacity. Detailed analysis will be required to establish whether there is existing capacity to accommodate the proposed connection and if not, to advise on the extent of network reinforcement required.

The SW strategy must clearly identify existing SW drainage arrangements, so that the extent of change in the SW discharge can be reasonably quantified and to ensure there will be a reduction in the volume and rate of flow to the combined sewer network during critical operating phases.

Please note that we will require evidence to demonstrate discussions with the LLFA have taken place and that the drainage strategy has been approved by them.

Network Reinforcement

Not required as no increase in flow.

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.