This case study brings us back home to our very own Head Office in East Sussex. After many years of consultations and negotiations, the land adjacent to our Head Office Building and Manufacturing Plant was obtained for developing a Gospel Hall, allowing the local community to gather.
In July 2019, the detailed designs for the Gospel Hall surface water drainage system were generated internally by our GreenBlue Urban qualified CAD/BIM designers. Our team of experts were able to monitor the excavation from initial planning stage through to installation and the build was a key opportunity to demonstrate our ArborSystem SuDs TreePits within a car park scenario.
Collaboratively working with Hillier’s Tree Nursery, 6 trees were selected; 2 Betula Utilis Edinburgh (Belonging to the Silver Birch family) 2 Hippophae Salicifolia (Streetwise) and 2 were Acer Freemalnii Autumn Blaze; all of which excel within a SuDS TreePit solution. The beautiful colours of these trees (such as the Betula’s slick white bark, and the Acers rich red leaves) helps break up the large tarmacked space of the car park, bringing a vibrant positive ribbon of colour to the area. Once these trees are established, their canopy interception will have huge benefits holding up to 80% of a 25ml rainfall on their leaves.
The connected ArborFlow TreePit trench, (which is fully tanked) runs continuously across the site containing the RootSpace Soil Cell system complete with ancillary components, allowing surface water runoff to drain down into a 450ml bioretention soil. This healthy soil can break down both petrol and oils coming off from the cars and at these depths isolates and retains pollutants, never allowing them to leave the system. Evidence suggests that the gradual percolation through these types of bioretention soils can remove anywhere from 50%-80% of our hydrocarbons without losing public footpath space developing above ground basins, creating a healthy below ground eco-system with microbiological activity.
One tree within a 25m3 GreenBlue Urban Rootspace system has a minimum 5000 litres of volume available for stormwater attenuation.
The Gospel Hall site design allows water to enter the TreePit system through a range of ways; firstly, permeable paving covers the whole tree pit system; Castle Tree Grilles which have spacer slots and irrigation inlets enabling water ingress, and the aeration ArborVents also add extra channels. Once the storm water enters the ArborSystem, it distributes across the whole RootSpace system through the contiguous ArborFlow Deck, reaching a 200mm clean stone drainage layer. This then flows into the 100mm land drain pipe within the stone layer and positively drained into the local watercourse.
GreenBlue Urban’s ArborFlow System supports all 4 pillars of SuDS within hard paving. Tree planting on this site gives back the amenity and biodiversity through green and blue infrastructure, as well as dealing with the quantity of water and enabling the soil and roots to satisfy water quality.
The Met office have confirmed we are 7 times more likely to receive extreme water rainfall and floods due to the climate crisis.
GreenBlue have used the convenient positioning of Gospel Hall as a means of training, allowing staff members time on site to learn the effects of the rainfall into our TreePits in real time. Our Team were appointed as the main contractors working alongside Performance Foundations for the groundworks and Orchard Paving for the permeable paving.
We continue to use the trees as a monitoring tool by using IOT equipment. We often lift the inspection chamber to record the flow of water the system is releasing into the adjacent watercourse. Our findings evidenced that after 24 hours of dry weather, the TreePits still release water proving the sheer volume the trees hold after a rainfall event.
GreenBlue encourage our industry colleagues to invest in our storm water infrastructure for a more efficient and long-term solution. Thinking of alternative ways we can deal with water at source rather than it flowing into our treatment plants, we have been actively working with the European project Interreg to collaboratively enable local authorities to create sustainable spaces. This movement focuses on solutions that deal with our changing climates implementing new ideas, different perspectives, and collective learning.
I can confirm GreenBlue have successfully launched several new brochures that contain a vast amount of beneficial information: The Trees and Sensitive Urban Design and in collaboration with McCloy Associates The Hydraulic Modelling MicroDrainage Guide.
GreenBlue pro-actively continue to enable sustainable drainage systems for future generations. We welcome customers, advocates, and friends to visit us at our Head Office for a tour of our new SuDs solutions in situ at Gospel Hall.