Building over or near a sewer

Developer ServicesDEV 005G – Guidance notes and procedure

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Wessex Water owns and has a duty to maintain more than 30,000 kilometres of public sewerage pipes. Many of theseare located within private land and often run down the side or rear of domestic properties. For all types of works,including extensions, conservatories and garages etc., you must apply to Wessex Water if these are proposed withinthree metres of any public sewer. For large/critical sewers this distance is likely to be greater than three metres.

What is a public sewer? Most sewers that are shared by more than one property or lateral drains (pipe outside of property boundary but onlyserving one unit) are public and will be owned and maintained by Wessex Water. The diagram below illustrates sometypical drainage arrangements. There are some exceptions. The only sewers that remain private are those that:• Serve only a single property within that property boundary.• Are maintained privately as part of a documented property management scheme.• Do not connect to the existing public system.

Does a public sewer run through my site?Our asset records may be viewed to help establish whether a public sewer will likely be affected by your proposal.However it is important to note that not all public sewers, particularly those within private land, will be shown andfor those that are their illustrated position will be approximate only.

In all cases, therefore, it will be important to undertake a full survey of the site to determine the actual drainagearrangements. Please do not rely on our asset records as these should be used for guidance purposes only.

Can I build over or near to a public sewer?Our preference is that you amend your proposal to avoid our public system. If your works will not be within threemetres of our assets then we will require confirmation in writing and a simple sketch for our records. Whereappropriate we will then issue a response of no objection, which you can add to your property deeds for futurereference.

If the works cannot be altered then we can consider your proposal. Whether it is viable will depend on the size,depth and catchment of the public sewer, as well as the location and nature of the proposed works. Every proposal isconsidered on its own merits, and unfortunately there will be occasions where an application is refused. In somecases a sewer may need to be diverted (where technically possible), rather than built over/near. If a minor diversion isrequired, we will advise if any additional fees apply (please note that major diversion work is an entirely separateprocess and further information is on our website).

Please note that under no circumstances will we permit building over a sewer where:

• The sewer is a pressurised pumping main.• A manhole would be inside a building.• Strategic sewers are affected or those that may require future upgrading.• Entirely new dwellings/buildings are constructed.

Flats/apartments Terraced Semi-detached Detached

Key

Footpath

Public highway

Responsibility of Wessex WaterPrivate drain, responsibility of homeowner

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What is the normal process?Step 1 Application & Payment

Please complete the application form and return it with a single set of design drawings plus the application fee of£325 to our Sewer Protection team. Payment can be by cheque made payable to Wessex Water Services Ltd, or wecan invoice so you can pay by BACS. You can also pay by credit card.

Step 2 CCTV survey (for building over or piling works only)

We will arrange to carry out a CCTV camera survey to check the structural condition of our sewer. We will thenadvise if any remedial works are necessary. For piling works, a post works CCTV survey will also be required.

Step 3 Decision

If your proposal is acceptable we will approve your works. If no drainage works are required then you mayproceed to step 6 and begin your project. However, if drainage works are necessary (e.g. sewer remedial works,moving a manhole chamber etc.), then our approval will be conditioned as appropriate pending completion ofthese works.

Step 4 Drainage works (if applicable)

If any drainage works on the public sewer are required then these will need to be completed and inspected. Iftrench excavations are required then you need to complete these before Wessex Water attends to fix the pipe.

Step 5 Completion (if applicable)

Once the required drainage work has been carried out to our satisfaction, we will send you a completion letterwhich confirms this to be the case.

Step 6 Construction

Your works can commence and any further inspections will be undertaken by the Council’s Building Controldepartment or your Private Inspector as part of their normal regime.

What information do I need to provide?You need to send the following information when you apply:

• Application form.

• The fee.

• Design drawings. These should include a plan and section showing the position of your proposed works and foundations relative to our sewer. 1:50 or 1:100 scales are preferred. Drawings submitted for Building Regulationsare usually sufficient, as long as the sewer is clearly marked. Do not scale directly from our asset records as these are approximate only.

How much will it cost?We have a set charge of £325 for all applications to build over or near to a public sewer. This covers:

• Administering & evaluating the proposal.

• Engineering consultation and/or site inspection if necessary.

• Liaison with Building Control or your Private Inspector.

• Formal approval

If you are building over a public sewer, we will survey the pipe and complete any necessary remedial works beforeyou proceed. If an application is rejected, your application fee will be refunded.

Are there any sewer protection/foundation requirements? We normally expect strip foundations to be used wherever possible. However, in certain circumstances alternative foundation designs may be considered with our prior agreement.These may include pads/piling, cantilever or raft designs, however they are non-preferred and should you wish toutilise such a design then this will need to be fully justified and approved. Foundations will normally need to betaken down to a specified depth to avoid any loading on the sewer pipe and provide a stable environment for anyfuture excavations.

When building over a sewer, your load bearing walls will extend over the sewer pipe. In most circumstances you willneed to bridge over the sewer using pre-stressed concrete lintels in accordance with our standard detail. Ourrequirements will vary on a site by site basis and we will advise you of these as part of the application process.

Where foundations to the buildings are at any point within 1m from the sewer, they are to be carried down at least 150mm below the invert of the sewer.

Existing dwelling

Typical ‘build near’

Public sewer

Lateral drain (public)

Private drain

Pre-stressed concrete lintel(s)

Public manhole

Private rodding eye / manhole

Abandoned private drain

Diverted private drain

New public manhole

Removed public manhole

Key

‘Build over’ withrelocation of manhole

outside the new extension

Typical ‘build over’ ‘Build near’ – all workswithin 3m of a lateral drain

require approval

A

A

Public highway

Existing dwelling Existing dwelling Publicland

Existing dwelling

B

B < 3m

C

C

Section A – ABuilding close to a public sewer

Section B – BLoad bearing wall construction detail

Foundations less than 1m fromthe sewer

Foundations more than 1m fromthe sewer

At a greater distance than 1m, an angle of 45 degrees can be taken to determine the required footing level.

Where foundations to the buildings are at any point within 1m from the sewer, they are to be carried down at least 150mm below the invert of the sewer.

Important

The information on this page is intended to show examples of typical scenarios and should be used for general guidance puposes only. Significant variations on a site by site basis are to be expected and it is in no way implied that meeting any of the above will guarantee approval.

Drawings are not to scale.

Ground level

More than 1m45˚ Publicsewer

Foundation

Groundlevel

Floor level

Floorlevel

Ground level

1m or less Publicsewer

Publicsewer

1m or less

Foundation

Floorlevel

150mm

300mm

150mm

150mm

Section C – CBuilding over a public sewer

Foundations less than 1m fromthe sewer

Foundations more than 1m fromthe sewerAt a greater distance than 1m, an angle of 45 degrees can be taken to determine the required footing level.

Foundation

Groundlevel

Floor level

FoundationMore than 1m 45˚Publicsewer

Mass fill foundation

Block or brickwork

50mm celotex or polystyrene

Granular bedding material

Sub soil or bedrock150mmminimum

150mmminimum

Technical Guidance

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Please find below a number of common build over or near examples. Sewers must be designed and builtaccording to the current edition of ‘Sewers for Adoption’, which is available from the Water Research Council.Foundations and walls should be designed and built so they do not put any loading on the sewer.

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Can I build over a manhole chamber? No Where a manhole/inspection chamber would fallwithin your proposal, please be advised that thesewould need to be re-located as appropriate at yourexpense. This is necessary to ensure that we havecontinued access to our public systems for operationaland maintenance purposes. Internal chambers can alsopose an increased risk of sewage flooding and odourissues.

Can I connect rainwater to the sewer?Not normally. On many projects there will be a need toadequately dispose of rainwater; however this can leadto or exacerbate sewer flooding within our network. Allother means (e.g. soakaways) must be properlyinvestigated before a connection could be considered.

A separate application is necessary for all new proposedconnections (both foul and rainwater) that will be madedirect to an existing sewer. Further information isavailable via our website.

Who can carry out my drainage works?This will depend on the type of works on your site. Forremedial works on public sewer pipes Wessex Water willundertake the required works (historical defects only –should your works cause a new defect to the sewer thenthis must be made good at your cost). Please note iftrench excavations are required, you need to completethese before we attend to fix the pipe.

If you need to move or re-build an existing publicmanhole chamber, or construct a new one for yourworks, this can be completed by your ground worker (atyour cost). If the sewer is deeper than 500mm, you mustuse one of our approved contractors who hold WessexWater permits. A list is available upon request. If yourground worker is not on our list they would need toprove to us that they have the required skills andexperience to complete the works to the correctstandard.

Moving or re-building a public non-man entryinspection chamber can be completed by yourgroundworker (at your cost) and they will not normallyrequire these permits.

For works involving private drainage (pipes serving onlyyour property), you can employ any ground worker tocomplete the work (at your cost) with the agreement ofBuilding Control or your Private Inspector.

What happens if I don’t obtain approval?If you carry out building works near or over our sewerwithout written approval, you may encounter problemsat a later date. We have a duty to operate and maintainour sewerage apparatus. If temporary or permanentstructures are constructed in such a way that theyobstruct us carrying out this duty, we can take action toremove the obstruction.

When you sell your property, you need the correctpaperwork to prove the sewer build over or build nearwas agreed by Wessex Water. Solicitor searches willreveal if an agreement is in place on our records. Youmay encounter difficulties selling your property if ourapproval has not been obtained.

Is Wessex Water still responsible for the sewer?If we give permission for you to build over or nearour sewer, we still have a statutory right of access tothe sewer now and in the future. If we need torepair, unblock or maintain it, we will do so at ourown expense.

Send your application to:Sewer ProtectionDeveloper Services,Wessex Water,Claverton Down,Bath BA2 7WW

Tel: 01225 526333email sewer.protection@wessexwater.co.uk

www.wessexwater.co.uk

E Other detailsPlease confirm the type of public sewer to be built over/near:

Foul Surface

Combined Unknown

Please confirm the size of sewer (if known) 100mm 150mm

225mm 300mm

Depth of any manholes indicated on the site plan: _____________ (metres)

Do you need to make a new connection to the public sewer? Yes No

(If yes, a separate application will be necessary which can be downloaded from our website at

www.wessexwater.co.uk/developerservices or can be sent to you on request).

F FeesWe have a set charge of £325 for all applications to build over or near to a public sewer. This covers:

• Administering and evaluating the proposal.

• Engineering consultation and/or site inspection if necessary.

• Liaison with Building Control or your Private Inspector.

• Formal approval.If you are building over a public sewer,we will survey the pipe and complete any necessary remedial

works before you proceed.Cheques should be made payable to Wessex Water with the reference number (if known)

written on the back.If you wish to pay by credit card please tick here

Contact name and tel. no: _________________________________________________________________

G Checklist and declaration (please ensure that you have included the following):

Drawings

Appropriate fees

Has the sewer(s) been accurately located on site

Yes No

Has the precise route of the sewer(s) been plotted on the submitted drawingsYes

No

PLEASE NOTEFailure to include any of the above may be deemed as an incomplete application and result in the

application being delayed/returned.

By signing this application, you are not automatically granted approval.

No works should start until full payment has been received and formal written approval has been granted.

I confirm to the best of my knowledge the above information to be complete and correct.

Signed ______________________________________________ Date: ______________________

Print Name _____________________________________________________________________www.wessexwater.co.uk

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A Applicant's detailsCompany/Name __________________________________ Contact name__________________________

Company Reg. no._________________________________ Signature _____________________________

Your address ____________________________________________________________________________

_____________________________________________________________Postcode__________________

Phone number __________________________________________________________________________

Email address ___________________________________________________________________________

B Agent’s details (if different from A)

Agent’s name (company name where appropriate) ____________________________________________________

Address ________________________________________________________________________________

_____________________________________________________________Postcode__________________

Phone number __________________________________________________________________________

Email address ___________________________________________________________________________

C Site detailsSite address ____________________________________________________________________________

_____________________________________________________________Postcode__________________

Site contact name _______________________________________________________________________

Site agent's name and number _____________________________________________________________

D Development detailsType of development

Side extensionRear extension

Other

Please specify________________________________________________________

Local authority area ______________________________________________________________________

Have you applied for building regulations approval?

Yes

No

If yes, please state the local authority/approved inspector reference number _______________________

Local authority/approved inspector contact name _____________________________________________

Date of application/notice_________________________________________________________________

Building over or near to a public sewer

Developer ServicesDEV 005A – Application form (please refer to the guidance notes before completing this form)

Buildover ref:

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