Category Archives: Drainage

BRE365 Soak-Away Testing in Gloucester

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BRE365 Soak-Away Testing in Gloucester

SWEL recently received a phone call from a company in Gloucester who needed a BRE 365 soak-awat report for a planning application. They happened to have a digger and a water supply on site, so we attended site on the same day to take measurements etc. and produce a report (the following day).

We also included some surface water drainage strategy in the report, and made a robust conclusion that will hopefully see that the planning related matters are satisfied.

A Large Excavator

The digger used was really rather karge for the job, we would normally use a 2.5 ton digger. But in this instance we had a 20 ton beast, with a 1.5m wide bucket. Needless to say the holes were quite large.

If you require some soak-away testing undertaking we can help out, maybe not on the same day as we did here but we will do our best.

Foul and Surface Water Drainage

Sewage Treatment Plant Decommissioning – Devon

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Treatment Plant Decommissioning – Devon 

Acting on instructions from a property owner in Bishopsteignton, Devon, Southwest Environmental Limited have been commissioned to draft a Decommissioning Strategy for a Sewage Treatment Plant.

The plant was around 30 years old, and used to treat water prior to discharging it to a river (surface water). However, around 10 years ago the development was hooked up to the mains sewers, and the treatment plant is now no longer required.

Although there is very extensive guidance available for the decommissioning of underground structures in the “Blue Book” for petrol filling stations, guidance for the removal of sewage related tanks, is some what limited. The Binding Rules for example give very scant advice, and further information given in PPG27 has now been withdrawn with no replacement made.

In this instance we authored a removal strategy based on international guidance, parallel sector guidance and review of case studies.

If you would like an opinion on decommissioning of a septic tank, treatment plant read bed or other foul water treatment system, then please contact us, and we provide a no obligation initial appraisal. We provide advice and reporting for a wide range of drainage systems.

Drainage Strategy – Amersham, Buckinghamshire

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Southwest Environmental were contact my a firm of architects who required a Surface Water Management Plan (Drainage Strategy) for their site is amersham. The project involves the extension of an existing warehouse.

The additional roof area has the potential to create run-off. A design was put forward to counter this problem.

Run-Off is when water falls on a hard surface, and does not soak in to the ground. It then will “run-off” . . . but where will it go. Perhaps it is caused flooding elsewhere. This is the purpose of a Surface Water Drainage Strategy. It sets out a method for dealing with Run-Off

The report was prepared on a quick turnaround (5 working days) and submitted for review. Pending some minor amendments at request of the client the report was submitted to Chiltern District Council for Scrutiny.

Are current design avoids the use of soak-away drainage although is does recommend for some attenuation.

Drainage Report – Cullompton

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Drainage Report – Cullompton

Some areas of Cullompton are designated as a critical drainage area. You may have a planning condition which states that:

“As the application site falls within the Cullompton Critical Drainage Area, please submit a Flood risk Assessment”



A flood risk assessment typical is focused on flood risk to the site, when what is required in a Critical Drainage is a Surface Water Drainage Strategy.

The way to deal with most domestic / residential drainage requirement is permeable paves, with added features. Mots consider this an expensive option, but this is due to lack of understanding.

In order to capture run off you must provide a volume of “holding” (an attenuation volume) this usually provided my the spaces between gravels in a soak-away trench.

But why not use these same gravel as a sub-base for permeable paving? You will have to import fill for driveways anyhow. You end up using the aggregate twice for soak-away and for sub-base.

Water from roofs can be fed in to the sub base, and drive water just soaks straight in, avoid the requirement for gullies etc. There are no blockages from leaves.

Application for Connection to Thames Water – Barking

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Application for Connection to Thames Water – Barking

Southwest Environmental Limited have recent applied for a connect to thames water sewers, on behalf of a repeat client. The application procedure is not overly onerous, but it does help to have background knowledge of the site.

Back in 2014 SWEL produce a Surface Water Drainage Strategy for this site and so we are familiar with the asset arrangement in the area, along with the flow rates from surface and foul water outputs.

It helps if the assets in the area are understood. . . 

. . . location plans were sourced. . . 

. . . invert levels should also be considered. 

This is the more recent of numerous applications we have undertaken on behalf of developers in London. The process does take a while Fees to Thames Water are around £500, and then we would charge time on top of this.

If you need any help with applications to Thames Water or Anglian Water or others, then please get in touch.

Environmental Consultants London 

Foul and Surface Water Drainage Strategy – Seaton

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Foul and Surface Water Drainage Strategy – Seaton

Southwest Environmental Limited have recently produced a Foul and Surface Water Drainage Strategy for a client in Seaton, Devon.

The report included specification of surface water sewers with calculation for attenuation in line with CIRIA guidance.

Sewers both surface and foul were specified in line with Sewers for Adoption 7.

The strategy took in the account the current sewers on site, and the locality of mains sewers in the area.