Milton Keynes Council's Master Plan to redevelop and regenerate land in and around Bletchley town centre included a high-quality public realm to increase pedestrian activity and create a thriving and safer outlook.
The quality of hard and soft landscape was a fundamental contribution to the value of the development. Consideration was given to the movement of vehicles, people, storm water and road gritting and to the practicality of maintenance over the long term.
The project offered an excellent opportunity to combine tree planting with best practice in water sensitive urban design. GreenBlue Urban provided design support and technical input to the tree pit design. By utilising a RootSpace tree system, large volumes of uncompacted soil could be provided, with a high-strength air deck support allowing flood dispersion and air replenishment to the soil zone.
One of the key success criteria for allowing long-term water attenuation within soil is to maintain uncompacted soil structure. This means that the macro pores as well as the micro pores, so critical to water and air transport and storage within the soil, are protected.
With the Bletchley project tree pit design, a modular, scalable rootzone construction allowed tree pits to be linked below ground that could accommodate a large volume of storm water. In this project, the system has eight trees, and has a minimum combined storm water capacity of 19,511 litres - equating to 2438 litres of attenuation per tree.
Using trees in this application means that every year the tree grows, canopy volume expands, and rainfall interception capacity increases.
This finished scheme could arguably be described as a truly multi-role example of green and blue infrastructure. If one considers the multiple benefits trees bring to urban space, not least in improving air quality, increasing real estate values and many other health and social economic benefits, it is difficult to imagine anything else that could bring the equivalent value and benefit to the urban realm.