ProtectaWeb is a proven no-dig method of reducing the imposed loads on the soil and tree roots beneath. It is a matrix that contains and confines granular infill. Its perforated cell walls permit lateral drainage, thus minimising hydrostatic build-up and ensuring the maximum supply of water to the tree roots.
The Arboraft tree planting system combines a high-strength pre-formed void creator with a specially designed soil. It prevents compaction of the subsoil ensuring the roots are not inhibited and growth is unrestricted. Tree anchors and irrigation can simply be incorporated into the system to provide a total tree pit solution.
An aerated and lightweight solution was provided to raise the garden level over the RPA of the constraining oak tree using Arboraft crates and 3D cellular confinement ProtectaWeb in layers.
Gaseous exchange to underlying tree roots has been facilitated using air funnels and pipes, located every 2m around the edge of the 11m x 11m garden. The garden edging was supported by high-quality green oak sleepers bolted into the Arboraft crates and supported by hand-dug and lined concreted oak sleeper posts.
The crated garden base was lined with specially treated permeable geotextile with ‘wicking’ properties that enable it to ‘hold’ water. This will prevent the 300mm garden topsoil from drying out and allow water to percolate to lower levels.
Below the wicking geotextile, a thick dpc plastic sheet ‘tray’ is located to within a crate’s width of the garden edge to capture and hold water. This prevents drying out but also allows excess water to drain away around the edges to the tree roots below.
Finally, 11 specially designed Wrekin ‘Tree Boxes’ were used to form part of the edging of the garden to allow the planting of 11 topiary yew and four mop-headed hawthorn. A base has been created which has allowed the stunning Flower Show garden to be relocated and installed for the patients and their families to enjoy at St John’s.
The construction was consultant-led and supervised by arboricultural consultants from Landscape Planning Ltd. with the help of geos team, using specially selected contractor C M Maintenance Ltd.
