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Southwest Environmental Limited
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Environmental Consultancy Services to Industry, Business and Individuals

Foul and Surface Water Drainage

It has become more an more common over the last 2 years to include fairly detailed Foul and Surface Water Drainage Strategies, as a part of a planning application. These can be applied during the application, rather than conditioned, which was more typically the case.

This is likely because many of the new drainage features required in the SUDs manual have impacts of site layout. Quite often they are extensive, visible features that need to be incorporated from the out set. Designers have become very used to seeing a certain type of layout for schemes which they tend to repeat for site to site. However, this can lead to problems.

"Hidden" Drainage features such as attenuations tanks are rapidly falling out of favour with planners, and in there place we see the requirement for visible, open SUDs features such as Swales, Filter Strips and Permeable Pavement.

On the vast majority of site we are requested to provide reports for both Foul snd Surface Water elements are required to be described. The surface water is the major obstacle to overcome, but application of Capacity Enquiry can be time consuming.

Surface Water Drainage Strategy

Below are a selection of subjects we regularly deal with although we will try to help with any problem you might have.

Surface Water Management Plans

 

CIRIA Mitigation Indices

 

BRE 365 Soak-Away

 

Attenuation Volume Calculation

  Surface Water Sewers
More recently these have been referred to as Strategies, although they can often grow in to a Document verging on a Specification.   Mitigation Indices are a new addition to the revise SUDs Manual. They need to be considered from the outset of a project to avoid complications.   Soak-Away Testing is now often required at planning. It is not often conditioned, or left to building regulation stage.   Attenuation Volume Calculations can be carried out to provide a volume based on drained areas and anticipated rain fall.   Look Up who owns Surface Water Sewers in Your Area, with our handy page.

If you then Google for "Asset Maps" you can normally buy these to show where a connection point can be found.

For planning you may be required to undertake a capacity enquiry.
Build Over Lateral Drains or Sewers   Fire Water Management Plan            
If you intend to build over or close to a public sewer or lateral drainage, you will be required to make an application to your sewerage undertaker, and provide certain details to them.   There are often requirements to manage fir water, in the unlikely event of a fire on you site. To extinguish a fire take a lot of water, and this may run in to the ground or a river, if not managed correctly.
           

Foul Water Drainage Strategy

It is often the case that you be required to provide evidence that capacity for you development can be provided by the local drainage undertaker. You can look up your local sewerage undertaker on our website.

We can carry out the following services on your behalf:

Typically we charge a modest fee, and you will be expected to pay application fees directly. Evidence that capacity is existing will then be included in any Foul and Surface Water Drainage Strategy that we are currently preparing.

Building Over (or close to) a Public Sewer or Lateral Drainage

If you intend to build over or close to a public sewer or lateral drainage, you will be required to make an application to your sewerage undertaker, and provide certain details to them. Consent is required if you build is over sewer, which should be fairly obvious to determine or near  a sewer. Being near a sewer is represented a a 45 degree "bulb of influence" extending out wards from the base of you proposed footings.

In order to make the recommended checks listed on mots application forms it takes considerable time and effort, and very many details relating to proposed and current drainage arrangements on your site require to be undertaken. They may include the following:

  •  CCTV Surveys
  • Condition Checks of the Drain
  • Precise Layout
  • Exclusion of Infill Structures
  • Protection of Drain
  • Sufficient Headroom
  • Review of Historic Blockages
  • Invert Levels
  • If you require assistance in filling out a "build over" form or similar drainage form then please contact us.

    45 degree rule