Darley Road, Bradford, United Kingdom

In 2007 the City of Bradford Metropolitan District Council began plans to modernise the pedestrian areas around Bradford’s primary shopping area. Darley Road is one of these areas. Last renovated in the 1980s, the concrete paving and other features were looking drab and unattractive. In an effort to encourage people into the heart of the city – employers as well as the general public – an interesting new design, incorporating quality infrastructure and trees, was created by Bradford Council landscape architects. Public consultations were undertaken and an exhibition day held at the shopping centre.

The aim was to create high quality streets which would be attractive and safe for pedestrians and enhance the setting for Bradford’s beautiful buildings. Darley Street was re-paved using natural Yorkstone flags and setts. Ribbed Chinese Granite forms the flush kerb line, providing tactile delineation for the visually impaired. New trees, lighting, stainless steel seating, cycle racks, bollards and waste bins were installed which complement the sophisticated yet simple paving.

The design included the planting of nine trees and European Hornbeam was the variety selected. Trial excavations were undertaken which revealed the predicable rubble under the existing paving. In some places the excavation went down to the original stone. Because the landscape architects wanted to create a high quality, durable streetscape with trees that would thrive for at least 30 years, they looked beyond the concrete manhole rings they had typically used for tree planting in the past.

The Council landscape architects researched the tree planting and maintenance systems available and approached Greenleaf, the UK distributor of Citygreen® urban landscape solutions, for advice on the most effective way to plant the trees. After much discussion with Greenleaf the Council decided to use several of the fully compatible products within the Citygreen advanced tree planting and maintenance system. The Council’s priorities were to ensure the long term health of the trees and to prevent the surrounding paving from heaving or sinking around the tree pit. Citygreen Stratacell™ was to be used in conjunction with RootDirector, RootRain and Castle tree grilles. BIRSE Civil Engineering was awarded the project as part of a four year partnering contract with the Council.

Citygreen Stratacell consists of patented, load-bearing, engineered plastic modules with vertical and lateral interlocks, for creating void space beneath pavements. Suitably large tree pits were dug to suit the anticipated size of the mature tree roots then the cells assembled within the pit to form a skeletal matrix. A high quality top soil was used to fill the matrix which is able to support adjacent pavement loads while preventing soil compaction. A very high percentage of space is available for tree root growth within the matrix – over 94% in fact.

To prevent tree root swirl and divert the roots downwards and outwards, Citygreen Root Director was used in conjunction with the Stratacell modules. Root Director is a modular root protection system designed for to protect pavements and hard landscaped areas. In this case it was used as a barrier to protect the gas and water mains being invaded by tree roots. Root Director has the added benefits of improving drought tolerance, enhancing tree stability and is simple to install.

RootRain was also used. An irrigation system, root rain consists of a perforated pipe in a circuit around the rootball of the tree, with a T-Piece and riser. At ground level, the grid inlet sits discreetly just above the surface and a tough alloy cap covers the entrance to the pipe. The Civic cover is secured to the grate, and is finished in a matt black epoxy paint finish.

The Darley Road project also utilised square Castle Tree Grilles. Concentric square sections were used, the inner sections of which are removable to adjust to further tree growth. Castle has a recessed design and can be manufactured in depths and widths to suit various block infill sizes, and to suit various paving patterns. The outer edge frame is supplied in bolt together sections.

The tree grilles were constructed as a tray with grooves across to let rain water in. The grilles were then paved to match surrounding paving so that, at the surface, only a slot running all the way around is visible.

The Council is very pleased with the renovation of this important road.

“The area looks completely different with the paving, trees, stainless steel bollards, benches and bins – a much more aesthetically attractive streetscape” commented a Council Officer.

Since completion the trees have thrived and the system proved durable, despite the warmer than usual spring weather. The experience of working with Greenleaf was very positive and the Council anticipates specifying this product line in future tenders.