Surface water management is a key part of modern construction, so developments are both environmentally friendly and compliant with local regulations. BRE 365 testing, developed by the Building Research Establishment, is a standardised way to test surface water drainage systems like soakaways.
This article covers the process, importance and benefits of BRE 365 testing and looks at soil infiltration rate, surface water networks and local planning authorities.
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What is BRE 365 Testing?
BRE 365 testing, also known as a soakaway test, measures how well the soil can absorb water to support an underground drainage system. It calculates the infiltration rate at a specific location to inform the design of sustainable urban drainage systems (SuDS) such as soakaways and other infiltration devices.
Why BRE 365 Testing is ImportantSurface Water Management
BRE 365 testing is part of designing systems that can handle large volumes of surface water runoff, especially after a storm event or heavy rainfall. It ensures the proposed system has enough capacity to prevent flooding and protect the surrounding area.
Flood Risk Reduction
Testing helps determine if the site’s soil and ground conditions can cope with a large volume of water. This is especially important for clay soils or areas with high water tables where additional drainage solutions may be required.
Regulatory Compliance
Local planning and lead local flood authorities often require BRE 365 testing as part of the planning process to approve drainage strategies for development proposals. Providing data on soil infiltration rates and a compliant drainage strategy at the planning application stage is key for developers.
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How is BRE 365 Testing Done?
The testing follows a strict protocol to get accurate results:
- Trial Pit Excavation
A test hole, 1m x 1m x 2m, is dug at the location of the proposed soakaway or infiltration device. This pit is a replica of the planned drainage system. - Filling and Monitoring
The pit is filled with water and the rate of water into the ground is measured. This is also known as percolation testing or soakage testing. - Recorded Observations
The time it takes for the water level to drop by half volume is recorded. This helps calculate the water absorption rate which is a key design parameter for soakaways. - Analysis and Reporting
The data is collated into a report which is often required by local planning authorities and environmental consultants. This report is key to designing a system that fits the SuDS hierarchy.
BRE 365 Testing ChallengesClay Soils and Gravel Soils
Soils with low permeability like clay soils may not absorb water while highly permeable gravel soils may require additional measures to prevent waterlogging or erosion.
High Water Table
A high water table can affect testing as groundwater may contaminate the results or limit the effectiveness of a soakaway system.
Space Constraints
In urban developments with limited space, designing a soakaway system that meets the capacity requirements without disrupting the site layout can be tricky.
Storm Event Planning
Developers need to ensure the system can handle the increased runoff from extreme weather or a storm event. This requires testing and planning at the design stage.
Soakaway Design Considerations
- Soil Type and Conditions: Make sure the underlying geology and soil conditions are suitable for soakaway installation.
- Drainage Strategy: Align the drainage system with the planning application and SuDS requirements.
- Installed Correctly: Work with experts to ensure the system is installed correctly.
- Local Authority Requirements: Comply with local flood authorities and provide the required suds reports.
BRE 365 and Sustainable Development
Including BRE 365 testing in the planning application stage ensures developments are water managed sustainably. By creating natural underground drainage systems, it reduces reliance on surface water networks, minimises environmental impact and helps flood risk.
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Summary
BRE 365 testing is key to good surface water drainage solutions. It gives you the data on soil infiltration rates, supports SuDS design and ensures compliance with local regulations. Whether you’re building a residential, commercial or infrastructure project, get the testing and drainage strategy right and you’ll be set for long term success.
For testing and advice on your drainage systems talk to geotechnical and environmental experts to get your project right.
