In 2016 the Brimmon Oak tree in Newtown, Powys, was named Tree of the Year by judges in the UK final and came second for the European tree of the year in 2017, just missing out on becoming the first British winner.
The Brimmon Oak has a girth of approximately 600mm and is 500 years old. It’s historical to locals and the Jones family has tended to it for generations.
The tree recently came under threat due to the Newtown bypass development plans. The initial proposed route would see the bypass constructed within close proximity to the tree, raising concerns over the tree’s possible destruction. Due to its historic nature and an extensive petition from the locals, it was decided that the bypass could be moved 3.5 metres away. However due to the size of the tree and its large roots, 15 metres was the recommended distance from experts. This led to a campaign which went viral and soon the plea was broadcasted in the news. Due to the mass exposure and the strong community spirit Mervyn Jones and the Brimmon Oak won their battle with the Welsh Government and it was announced the bypass would be moved.
Unfortunately the problem didn’t end there. There was still a worry about damaging the large roots due to the size of the tree. A new solution was needed to protect the tree. This was going to be difficult due to the fact the bypass couldn’t be moved any further away than 15 metres.
Geosynthetics Ltd were approached by the contractors Alun Griffiths’, looking for a possible solution. An embankment would need to be constructed on the peripheries of the tree’s RPA. This would create a 1 in 1 gradient, from the new road surface to the existing ground level within the RPA. Geosynthetics Ltd recommended their tree root protection system Cellweb® TRP which is the market leading solution and Alun Griffiths’ decided to move forward with this.
The construction of the embankment would require a build-up of approximately 500mm within the RPA. Construction of the embankment utilising conventional, compacted subbase materials would prevent continued water permeation and gas exchange between the atmosphere and roots beneath. This may ultimately cause root death, reducing the tree’s ability to obtain the water and nutrients that it requires.
The embankment would need to be constructed using multiple layers of Cellweb® Tree Root Protection. This would ensure the continued health of the tree and comply with the arboricultural method statement.
Cellweb®TRP is the only cellular confinement system specifically designed and sold for tree root protection applications. The unique cell size, cell depth and cell wall perforations combine to create the market leading tree root protection system offering a ‘no dig’ solution for sub base construction within root protection areas, preventing root severance.
The embankment installation was carried out on Monday 26th of March. The construction was overseen by arboricultural clerk of works, Jerry Ross. Geosynthetics Ltd in house arboriculturalist was also present and provided free onsite installation advice.
The construction of the embankment would comprise three layers of 150mm deep Cellweb® TRP. Photo 1 below, shows the installation of the Treetex Geotextile and the first layer of Celllweb®. The Treetex Geotextile acts as a separation layer, preventing the migration of the infill material into the ground beneath. Where the system is used for road construction, the Treetex lay also acts as a pollution control measure.
Each layer of Cellweb® is installed on top of the other. Each layer is located 150mm inside the outer edge of the layer beneath. This achieves the required gradient of 1 in 1. Each of the outer cells are left empty of the stone infill material. These will hold the topsoil layer. The right hand side of the Cellweb® installation will form the transition between the conventional road construction and the Cellweb® embankment.
Site topography within new developments often requires level changes within the RPAs of retained trees. This project shows how, with careful design, levels can be increase within RPAs while maintaining favourable conditions for retained trees.
Geosynthetics Ltd couldn’t be prouder to assist with such an important project of saving the 2016 tree of the year.
The project should be complete by late 2018 to early 2019.
Geosynthetics Ltd offer a range of products. We also offer free technical support from our in-house engineering team and site visits to assist you in any way we can. For more information please visit www.geosyn.co.uk .