The increase in visitor number at Harcourt Arboretum put pressures on parking availability on site and the additional parking bays and vehicular access paths were required to cope with the extra traffic.
The only viable space to use was situated to the north of the Arboretum, in an area that was populated by a large number of mature, extremely valuable trees.
There were obvious concerns that using this area for car parking would damage the long term health of the trees, due to the soil compaction that would occur from your traffic driving over the root protection area (RPA).
The architects for the project, Peter Brett and Associates, commented: "We carried out some research into the pavement construction options for a proposed car park in an existing arboretum. The most non-evasive option to reduce the excavation between the tree roots involved the use of a product like CellWeb".
The practice contacted the Geosynthetics technical team to provide a suitable solution.
Geosynthetics Ltd proposed the use of a Cellweb 150mm tree root protection system (TRP) with a non-woven needle-punched Treetex geotextile placed directly on the formation.
The Cellweb 150mm TRP was infilled with a clean 20–40mm angular stone to promote aeration and positive water transfer through to the ground. The granular material was simply placed inside the Cellweb with no compaction required.
The grading of the infill means that voids are created, ensuring that water and air are able to pass through to the sub soils. The CellWeb was surcharged by 50mm of granular fill to give a rustic look to the final surface.
For this project, granular material depths were reduced by using CellWeb, and in most cases, sub-base thickness can be reduced by 50%.
Independent testing concluded that CellWeb has a significant effect on reducing sub-soil compaction around existing tree roots. The final installed system provides a suitable platform for all intended vehicular traffic at the aboretum.