Chepstow Street Case Study

Earlier on in 2012, Green-tech was approached by Red Rose Forest (RRF) a partnership between six local authorities in the North West looking for a tree planting solution that also considered surface water management. The project required the planting of 3 trees in a 16m permeable trench.

System Benefits:
• Superior strength, can  support 70t per SQM.
• Simple and quick to install.
• Directs roots away from the surface, preventing pavement damage.
• No additional support required.
• Accomodates a variety of project scenarios.
• Manufactured from recycled materials.

RRF with the support of the project
funders INTERREG IVB and Viridor wanted to pioneer a tree planting specification in Greater Manchester that would demonstrate the value of the Permavoid raft system and permeable paving as a means for ensuring a good rate of oxygen, moisture, nutrient exchange from the surface to the tree roots below. The project also demonstrated the value of permeable paving in a city centre environment, prone to flash flooding, as a means for reducing surface water run-off.
Green-tech Ltd, representatives from RRF and Manchester City Council worked in partnership on this project to ensure that all aspects of water management and the tree’s healthy root development were considered from the beginning. Green-tech prepared the Permavoid CAD drawings for the 16m trench with the help of RRF. Each drawing was considerate of the hard landscaped environment and the proximity of the trees to the road.
Peter Stringer, Special Projects Manager for Red Rose Forest added:
‘Permavoid’s load-bearing properties prevents compaction, the interaction
between the nutrient rich soil mixture in the Permavoid and the percolation of rain through the permeable block pavers provides a slow release feed system to the roots below.
When the nutrients are washed through over a long period of time it
will leave voids which when encountered by tree roots will air
prune their growth to arrest any further upward growth and subsequent damage to the paving above. This system will demonstrate the sustainability & long term cost savings of this approach in terms of tree welfare and eradicating root damage to pavments. ‘

After the tender was awarded,
representatives from Green-tech's
product specification team visited the site at Chepstow Street Manchester to assist the contractor (UPM Tilhill) with the installation of Permavoid. Certain  obstacles were overcome during the two-day installation, including proximity to sewers and disused caverns located underneath the tree pit. Due to the flexibility of the Permavoid system, the team was able to overcome all the issues whilst on site and the
project continued without delay.

Barry Browne, Green-tech’s Technical Specification Manager commented:
‘The project at Chepstow Street
demonstrated the flexibility of the
Pemavoid raft system. Whilst on site we were able to make changes to the tree pits without returning to the drawing board or affecting the overall pit volume. The Permavoid raft system is designed to offer all the benefits of a healthy tree pit and and installation with minimal fuss or

t: 01423 332100

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