Wastewater pre-design strategic assesment

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For large/complex sites one of our engineers can discuss with you the early stages of your design and proposals for maintaining a sewerage system.
This communication can be requested at any point before the submission of a sewer adoptions application (S104) through a pre-design strategic assessment application.
Whether a site is large or complex can be determined by whether it has:
Multiple phases
Multiple landowners/customers
Multiple points of connection
Pumped discharges
A storage component
A Wastewater Treatment Works
Sustainable Drainage System

However, the above list isn’t exhaustive. So you may request a pre-design strategic assessment based on your understanding of a complex element of the development that you want to discuss with us before submitting a sewer adoption application.
All pre-design strategic assessment applications should be made by downloading the pre-design strategic assessment application form. Before you fill in the application form, please read the wastewater pre-design strategic assessment guidance, which you'll find below.

Please also check the water and wastewater asset maps for your site – if you’d like to buy a sewer or water plan from us, please see our sewer and water maps page.

Guidance for Stage 1b

The aim of the pre-design strategic assessment is to discuss the intricate, site-specific details for anything proposed for adoption – whether that’s taking into account a system that needs cyclical operational and maintenance requirements, discussions over ownership or considering the standards needed before a formal S104 application is requested.
Providing this information at an early stage will allow us to determine whether the details you have proposed will meet the requirements for adoption and allow us to provide early advice without you having to apply for a S104.

Responses to this section will enable us to understand:
What are the feasible drainage options that the development site is capable of delivering safely.
What is the overall drainage strategy for the development.
The restrictions that can affect site drainage plans.
How will the existing and proposed flows will arise and be managed.
Whether the ground conditions are capable of accommodating the surface water flows safely.
Dealing with all these elements at an early stage allows them to be managed through to completion and should reduce queries from either party during the application process.

Once we receive your application, one of our engineers will contact you within 14 days to review and agree the requirements with you. A site visit may be required as part of this review and a date will be agreed with you.
Within seven days of completing the review, our engineer will set out their guidance in writing to you. This guidance will provide an indication of requirements for design, adoption and legal requirements to support your future S104 application. Please note, this will be solely guidance at this stage and is not technical approval.

We're conscious there’s replication with the information you’re asked to submit for a pre-planning enquiry and a pre-design strategic assessment. Therefore, should you have already submitted a pre-planning enquiry application when submitting a pre-design strategic assessment application, please provide the sewerage reference number where requested on the application form and only provide the additional information requested in sections two and seven. However, if you have not submitted an application for a pre-planning enquiry, please complete all of the pre-design strategic assessment application form.

Please click *

Development Type(Please tick all that apply): *
No of units
General Housing Equivalent L/S
0 to 50
< 2.3
51 - 250
< 11.6
251 - 500
< 23.2
> 500
> 23.2
Is the site identified in the local plan? *
Have you approached us about this site previously? *
Is the development part of a larger site that will be developed in phases? *
Table 1 Foul water flows before development (l/s if known, enter ‘n/a’ if not known) Surface water flows before development (l/s if known, enter ‘n/a’ if not known)
Foul connection: How are you proposing to drain foul flows from the site?
Surface water connection: You should follow the surface water hierarchy. Please indicate below and provide evidence to support your strategy as an attachment to this enquiry. H3 Building Regulations Guidance is available here: * gov.uk/government/publications/drainage-and-waste-disposal-approved-document-h
Please confirm that the following list of information has been provided to support with your enquiry:

  • Site boundary clearly shown
  • Roads clearly shown
  • Adjacent buildings clearly shown
  • Private pipe run to Southern Water network clearly shown
  • Maximum file limit is 50MB
  • Allowed file types are DOCX, DOC, PDF, XLS, XLSX, JPG, JPEG, BMP, PNG, DWG (auto cad), DXF (auto cad), DGN (microstation), PRP (microstation), PRW (microstation)
Warning! File size too big. Maximum file size 50MB.

I formally request that this development now proceeds to the Pre Development Strategic Assessment (PDSA) stage.

I confirm that to the best of my knowledge the information I have supplied is complete and correct.

Failure to include any of the requested information will be deemed as an incomplete application and may result in this application being delayed/returned. This application does not mean approval has been granted. No work should commence until written approval has been given by Southern Water.

This application does not mean approval has been granted. No work should commence until written approval has been given by Southern Water. In some cases the pre-design strategic assessment cannot be completed due to incomplete or insufficient records. In this instance, we may ask the applicant to provide surveys of drainage in the area. These would be conducted at the applicant’s expense.The contents of the report are for direct use only by the applicant and are to be kept private and confidential. They may only be disclosed to third parties with the written approval of Southern Water. Such third parties to have no subsequent implied or other right to disclose the contents and information to any other parties.


Service levels: We plan to acknowledge receipt of your application within 7 calendar days of receipt and provide a full response to your query within 21 calendar days unless an extension is agreed.

About us: Southern Water supplies water to 2.5 million customers residing in 1.1 million properties and provides wastewater services to 4.6 million living at 2 million properties. See what is happening in your area at: southernwater.co.uk/your-area/your-area Registered number 2366670