BRE365 Percolation Test

BRE365 PERCOLATION TEST

BRE365 Percolation Tests establish whether the ground at the site of a new development is suitable for infiltration forms of Sustainable Urban Drainage Systems (SuDS), such as soakaways. The BRE365 infiltration or percolation test measures the water absorption rate of the soil to determine whether the ground conditions are appropriate, and ultimately whether the surface water arising as the result of development proposals can be dealt with and treated at source, and ultimately not having to be conveyed to the surface water networks or rivers, and overloading these to cause flooding.

These reports are often used as part of planning applications or planning condition discharge, especially where infiltration forms of Sustainable Urban Drainage Systems (SuDS) are recommended. Sustainable Urban Drainage Systems (SuDS) aim to alleviate drainage problems by dealing and treating surface water runoff at source, or by attenuating this and then releasing it back into the surface water network at a much lower rate.

Soakaway

WHAT IS A SOAKAWAY?

Soakaways are underground drainage systems designed to store surface water run-off before gradually allowing it to infiltrate into the ground. They are a key component of Sustainable Drainage Systems (SuDS) and sit high in the SuDS hierarchy, as they ensure that surface water run-off remains within the site and does not enter local surface water networks, watercourses, or rivers, which could otherwise lead to overloading and flooding.

A soakaway must be capable of releasing the stored water into the ground relatively quickly, maintaining sufficient capacity to receive high volumes of run-off during periods of heavy rainfall or storms.

Soakaways are a sustainable and effective solution for developments, as the infiltration process helps recharge underlying aquifers and requires minimal maintenance. When properly designed and installed, soakaways can have a lifespan of at least 100 years.

Percolation + Soakaway Importance

WHY ARE PERCOLATION AND SOAKAWAY TESTS IMPORTANT?

Percolation tests should be carried out in the design stage of development, as part of the ground investigation, before construction commences.

BRE 365 Percolation Tests follow the guidance of the Building Research Establishment (BRE). The process will calculate the Soil Infiltration Rate, which then allows us to calculate the size of any proposed Soakaway or other infiltration device, based on a 1 in 100-year storm event plus 40% climate change allowance.

In simple terms, a BRE365 percolation or infiltration test measures how fast water drains from the soil. Once established, the correct Soakaway or infiltration device size can be calculated which ultimately informs our final design.

According to the BRE365 guidance, soakaways should discharge from full to half-volume within 24 hours, and this is to ensure that the soakaway or other proposed infiltration device has enough capacity to deal with another storm event within that 24 hours.

WHY AM I BEING ASKED TO HAVE A BRE365 PERCOLATION TEST CARRIED OUT AT PLANNING APPLICATION STAGE?

Local Planning Authorities (LPA) and Lead Local Flooding Authorities (LLFA) request SuDS reports at planning application stage, to ensure that development proposals have considered the surface water runoff arising from a development and have feasible proposals in place prior to commencing a development. The main reason for this is that SuDS do require space, and all infiltration devices must be located a minimum of 5 metres away from a habitable building.

Obviously, most developers want to make the most of the available space on a development therefore, there may not be any space for a soakaway. Therefore, should the BRE365 percolation pass and there not be available space for a soakaway, the planning authority may ask the client to change the site layout in order to provide space to allow infiltration.

Therefore, typically for major developments where a desktop geological study shows underlying geology with potential for infiltration, the LPA and LLFA will request that a BRE365 infiltration test is carried out on the site, in order to show that the SuDS hierarchy has been followed, and also should the test fail, this allows us to investigate further methods of restricted surface water disposal in order to ensure that SuDS can be included in the development and that there is somewhere for any restricted surface water discharge to be conveyed.

Moreover, sites with high clay content soil and/or a high water table are also not suitable areas for a Soakaway.

Carrying out a Percolation Test demonstrates to your local authority you have conducted the necessary steps to find out this information as part of your planning application.

Choose Nimbus

CHOOSE NIMBUS FOR YOUR PERCOLATION TESTING

We provide on-site Percolation Tests to BRE365 to provide you with the infiltration rate at your development site, our team work closely with our engineers and liaise with them during the test process, this allows us to keep the whole process in house.

If your planning application requires a Sustainable Urban Drainage Strategy (SuDS), and a desktop geological assessment shows the underlying geology to be suitable. A BRE365 Percolation test will be essential to determine whether a Soakaway is feasible for your site, as well as allowing us to calculate the size of this.

Get in touch with us today to discuss your site’s requirements. As experts in specialising in Flood Risk, Surface Water Management & Drainage Design (including SuDS Design) we would be happy to help!

Nimbus Engineering

CHOOSE NIMBUS

We always provide the most up-to-date advice about surface water drainage and SuDS and can provide you with fast and cost-effective reports that deliver you a drainage strategy that will always meet national and local policies. We are confident we can produce a report that will achieve you planning approval through providing the information needed by local planning authorities.

As environmental consultants, we can give you early-stage advice for sustainable drainage designs to integrate into your development, allowing you to work around any constraints or risks, in a natural and ecological way. We can then provide the reports and assessments that will give you SuDS strategy, with the required level of detail, to minimise surface water run-off from your proposed development, using best practice methods and calculations.

Customer Reviews

“I am very happy with the work Nimbus have carried out for me over the last 10 years. They always deliver a good service at a very good price and always high quality reports and fast turn around. They have carried out work on many of my projects in Croydon and I have never had a problem with their work.”

George Christodoulou • Director

“I have worked with Nimbus Engineering for many years. I can always count on them to deliver comprehensive flood risk assessments, drainage strategy and SuDS reports, on time and at a competitive price. More importantly, I can’t think of a single occasion where a council has not accepted the report’s.”

Andy Hollins • Director

“I have used Nimbus Engineering for a number of projects over the last 10 years and have always found them to be flexible, highly skilled and great value for money. Anyone looking for Flood Risk and/or Sustainable Urban Drainage System advice need look no further, Nimbus have the solution.”

Derek GC White • Sustainability Consultant

Get A Quote Today

Get in touch with Nimbus Engineering Consultants for SuDS reports, drainage design, or general engineering enquiries. Our team will be happy to provide advice or a quotation for your project.

BRE365 Percolation Test