London is and always has been a tree lined city. Some of the benefits are obvious, trees are beautiful to look at – marking the seasons with blossom, seeds and changing leaf colours, they provide homes to a variety of wildlife and on a more practical level create shade and shelter.
Trees have invisible benefits too; absorbing carbon dioxide from the atmosphere as part of the photosynthesis process which allows them to grow. This removal of CO2 from the atmosphere trees can reduce the effects of pollution by cleaning the air and reducing temperatures. Large leaf canopies catch rainfall and slow down the water’s progress from sky to the ground, helping to reduce flash flooding.
Trees also release oxygen into the atmosphere and their leaves catch dust and pollutants in the air preventing them from spreading further, they reduce smog formation, radiant energy from the sun is absorbed or deflected by leaves, this combination of factors reduces the incidence of asthma, skin cancer and stress-related illness.
Trees can even reduce crime! The presence of trees creates a more pleasant environment that people want to go out and enjoy. Simply having more people around to potentially discover and report crime and this deters criminal activity.
Many London Boroughs have embraced the need to preserve existing trees, replace diseased and dead trees and plant new trees, but planting and maintaining trees in an urban environment is not without problems.
A tree’s root system obviously needs access to water in order for the tree to survive, the roots also need to be able to move as they grow. However a natural earth setting is not possible in a pedestrianised street as it can get very muddy, slippery and be hard to keep leaf and litter free and trees are at risk of root damage or being uprooted entirely. Traditional tree grilles provide irrigation and protection for the tree roots but they are difficult to keep clean as litter, dog waste, cigarette stubs and even hypodermic needles get deposited or trapped between the bars.
The London Borough of Hackney asked Civil Engineering Contractor Volker Fitzpatrick to solve the problem of protecting the roots of the many trees which enhance the streets of Hackney, situated on the doorstep of the Olympic site.
RonaDeck Tree Pit System from Ronacrete was recommended for its SuDS compliance, ease of maintenance, flexibility and for the appearance of the resin bound gravel.
RonaDeck Tree Pit System is a natural aggregate finish surround for planted trees in public and private areas. RonaDeck Tree Pit System surrounds the tree in a solid yet flexible construction that is easily swept clean and has a porous structure that allows rainwater to seep immediately through to the root system and reduces the burden on surface water drainage.
Sub contractor AJ O’Connor purchased the RonaDeck Tree Pit System through specialist construction industry distributor WT Burdens and gradually the system has been applied over a large area.
AJ O’Connor excavated around each tree to a depth of 150-200mm and filled the excavation with gravel to within 50 mm – 75 mm of the surface, the required depth of RonaDeck Tree Pit System, depending on expected traffic. The two-part resin was mixed with a drill and paddle before being added to the kiln-dried aggregate component in a high capacity forced action mixer. The mixture was then laid on the prepared gravel base and levelled off; allowing a curing time of four hours for foot traffic and one day for vehicles.