CONCRETE & STONEWORK
The biggest misconception held on CBPP systems is that they require a far greater level of maintenance than a standard construction and if this is not done then debris and weeds will clog the wider joint within a very short period of time.
Brett Landscaping’ s technical team wanted to demonstrate this effectiveness using installations the company had supplied CBPP products to more than a decade ago. To prove that the joints of the Concrete Block Permeable Pavements still perform after numerous years of trafficking, weathering and low maintenance Brett Landscaping conducted tests at two sites with Wakefield Council’ s boundaries, at Poppy Fields Crescent in Castleford, and Bubwith Close at Stump Cross, Pontefract using industry recognised American testing methodology.
At both sites Brett Landscaping identified that due to a risk assessed maintenance plan being put in place in the years leading up to the testing has not had an adverse effect on the CBPP performance. The average flow rate for the 3 tests done to each of the pavements at the test sites were both well in excess of the 10 % requirement for the design infiltration rate:
• Poppy Fields Crescent: 1,593 mm / h
• Bubwith View: 1,099 mm / h
We were so impressed with the findings that we have published the research on our website in a paper entitled Consistent efficiency: Assessing the long term hydraulic performance of Concrete Block Permeable Paving joints, which also includes our recommendations for a working maintenance plan in the initial months following installation undertaken by the developer, and then a longer term approach for when the highway areas fall under local authority control.
CBPP from Brett Landscaping is playing a major role on the UK’ s largest SuDS scheme, the £ 76m Mansfield Flood Resilience Scheme, which is designed to create a surface water drainage system that can hold 58 million litres of rainwater.
Working with Severn Trent Water, Brett Landscaping supplied 50,000m2 of its Omega Flow and Invicta Flow permeable paving for a range of retrofitting measures within highway land such as residential parking areas to tackle the runoff of surface water. The permeable paving has been designed as either infiltrating with a geotextile base or non-infiltrating with an impermeable liner with
a return to the sewer system. The unique‘ male’ and‘ female’ interlock to Brett Flow blocks creates a 6mm joint, allowing surface water to infiltrate through into the sub-base below whilst providing superior levels structural integrity to the surface of the pavement and peace of mind to the client and designers.
These CBPP systems will naturally reduce storm overflow activation by attenuating surface water and delaying or preventing it entering the combined sewer network, without requiring any further land-take. This will mitigate future overloads of the drainage system and reduce storm overflow activations into water courses.
This scheme could be the first of many across the country as local authorities and water companies investigate the possibility of retrofitting SuDS.
Sustainable drainage is due to be mandatory in all new housing schemes, but existing communities shouldn’ t be forgotten when it comes to mitigating flood risk and preserving water, and it could also offer a way for local authorities to change the mindset on their approach to highways maintenance.
www. brettlandscaping. co. uk
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