In a recent blog, we discussed how to overcome the constraints that we come up against when planning urban tree planting and discussed the solutions that GreenBlue Urban offer to overcome these above and below ground issues.

Stockton High Street – RootSpace tree pit cross-section.

One question that gets asked regularly is whether utilities can be accommodated within a GreenBlue Urban RootSpace soil cell system. There is an incorrect assumption that utilities and tree roots cannot mix, and this has often meant that planned planting has been cancelled – we believe – unnecessarily.

Below ground utilities are an ever-present reality within our urban areas, and if we are to retain and improve our canopy cover, we need a strategy to integrate them within tree pits.

Because tree roots are opportunistic, the provision of good quality uncompacted soil is critical to the baiting of tree roots into the zone that has been designated for their establishment. It is often the lack of accessible soil volume that forces the tree to seek out nutrient, water, and air from other areas. When installing utility ducts and pipes, the excavated sub-soil is backfilled, usually with sand or gravel surrounding the service run, and this tends to aerate the soil, creating a more root-friendly medium. Many utility runs have condensation forming on their external surface due to the temperature differential between the surrounding soil and the internal of the service, which also encourages fibrous root growth in this area. Recent research indicates that tree roots can “sense” water movement below ground and it appears that roots will actively grow towards a drain, even if there is no obvious water leak from the pipework! This does mean that careful consideration must be given where utility runs are present in or adjacent to tree planting pits.

Service heavy StrataCell tree pit.

So how can we provide this uncompacted soil volume needed below a hard surface for long term tree health? GreenBlue Urban provide a useful guide to soil volumes necessary for different species of trees, but we understand that it is not always possible to achieve optimum volumes in congested urban spaces. It is far more beneficial to have a lesser volume of uncompacted soil than a bigger volume of a poor growing medium such as products known as “structural soils”, and therefore a method needs to be found which protects the good quality soil from compaction and anaerobic conditions.

Twenty years ago, GreenBlue Urban launched the world’s first soil cell system, the RootCell. This innovation has probably made the biggest difference in global urban tree mortality of any product in the market. Recreating forest floor soil conditions enables trees to flourish, as they would in their natural habitat, and the proof is that canopies continue to grow in urban trees installed with these solutions.

As GreenBlue continued to innovate and develop the concept, the StrataCell soil cell was launched in 2007, and the RootSpace system in 2016, all manufactured from 100% recycled, recyclable polymer, saving landfill or incineration of end of life plastics. This latest soil cell has proven exceptionally popular, having the highest soil volume ratio of any soil cell in the world, allowing larger utility runs through the system, being more cost-effective and having an inbuilt aeration deck, which gives even gaseous exchange across the whole soil area. Service ducts and pipes up to 300mm diameter can be accommodated within the RootSpace construction, and examples of integrating utilities can be seen below.

RootSpace works around utilities with ease.

Utility companies have been complimentary of the concept and use of RootSpace, as the system does offer some protection to their assets. When access to the utility is required, the RootSpace lid is accessed first, reducing the chances of a utility strike, which can be expensive to repair. GreenBlue Urban also recommend the use of warning tape installation on top of the RootSpace system, to enable anyone working around the tree to have early awareness of services, preventing accidents from occurring.

As the need for more urban trees to help with combatting climate change becomes ever more obvious, it is solutions such as RootSpace that will have to be deployed; GreenBlue Urban are committed to the environment by increasing our green infrastructure, managing our blue stormwater challenges and reducing our reliance on fossil fuels by recycling and using recycled materials in manufacture. GreenBlue Urban – the future’s greener and cleaner.