Diverting existing surface drainage from an existing Combined POC to SW via a new SW POC

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Network Impact

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 any 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.

Therefore, Anglian Water is supportive in principle to the diversion of existing SW flow from Combined networks to SW networks. This will have an incremental effect of separating surface water from the combined network and potentially creating headroom for new FW connections. We will need to establish that the relative benefit, in terms residual operational risk is justifiable.

Process

As the developer is responsible for providing the appropriate surface water disposal infrastructure. As such, all the work to determine the feasibility of a connection to the existing surface water sewer complete with all upgrades to the consented outfall is to be carried out by the developer at their cost.

The impact on the SW network would still need to be assessed in line with a new contributing area connection (see Scenario 3: New surface area draining to an existing SW sewer); however, emphasis will be placed on resultant balance of risk across the Combined and SW networks. If you wish Anglian Water to carry out the evaluation of an increase in flow to the surface water sewer, a cost and timescale estimate for this analysis can be provided. Please contact planningliaison@anglianwater.co.uk.

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.

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

Environmental Incentive

This is considered a more sustainable solution with a net environmental impact as a more sustainable surface water discharge method is used for the new development. Anglian Water will offer an environmental incentive to such and this amount to 50% of the wastewater infrastructure charge for the development. More information on the environmental incentive is available on our website here.

Network Reinforcement

Should network reinforcement be required as a consequence of additional surface water flow to an existing public surface water sewer, Anglian Water will request a planning condition to ensure no additional flow will be connected until sufficient capacity in the network has been confirmed.

Reinforcement of the existing network, when required as a consequence of a new surface water connection, is not included within the Infrastructure Charge. These works may be requisitioned under Section 98 of the Water Industry Act 1991 or implemented by a self-lay provider under Section 151 of the Water Industry Act 1991. , with the capital cost fully chargeable to the applicant. A cost and timescale estimate can be provided for requisitioned network reinforcement.

Alternative Disposal Options

i) 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, 1991.

ii) New drainage infrastructure and outfall

The alternative is that a new surface water sewer is constructed which is used 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

A new surface water sewer can be used as a mechanism to discharge surface water to a watercourse or as part of a SuDS scheme where appropriate. 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 of our PDSA service.