As a consultant I have heard many clients discuss at length how wonderful trees are and how they add an air of maturity to a development. Trees offer many benefits but it is amazing how opinions can change once they are deemed to be ‘in the way’. The simplest, and usually the most cost effective, option for a developer is to fell the tree. However this is not always possible, either due to legislative restrictions where the tree does not belong to the client, or simply because the client wishes to keep the tree for amenity purposes.
One such case involved installation of a foul water pipe within close proximity of a Sycamore (Acer pseudoplatanus) which was subject to a Tree Preservation Order (TPO). The pipe was required to connect a new development with the existing water network which was located 22m from the development. At its closest the pipe passed 3.2m from the stem of the tree. Due to the development layout and location of the existing infrastructure, no alternative route for the pipe was possible.
The presence of a TPO provides a degree of protection to the Sycamore tree and as such its removal was undesirable. The installation of the pipe using traditional methods (excavation with a mechanical excavator)would result in large scale severance, damage and loss of roots, potentially leading to the death of this tree. This is when the Middlemarch Arboriculture Team was called for assistance!
First, the Arboricultural Team reviewed the options. To comply with legislation and prevent damage to the protected tree a precautionary approach was required for the pipe installation. Three options were considered: hand digging and spoil removal with hand tools; excavation with an ‘air-spade’ and spoil removal with hand tools; and excavation with an ‘air-spade’ and spoil removal via vacuum. The first two options, which use traditional hand tools, were considered unsuitable as the use of spades, picks and forks would still result in root severance and a long term impact upon the protected tree. Excavation with an ‘air-spade’ and removal of spoil with a vacuum was consequently selected as the most appropriate method.
Vacuum excavation of soil uses a high power vacuum suction system. A jet of air (delivered via an air-spade) is used to first loosen soils. The soil is then extracted using an air vacuum hose which transports it to a spoil/debris tank for later disposal or backfilling, which is a bit like a giant vacuum cleaner. The use of this technique allows the tree roots to be exposed and therefore avoided (and not damaged) during the installation of the pipe.
To further ensure the Sycamore tree was not damaged during the works, Middlemarch attended the site to supervise the excavation works. The vast majority of roots could be retained and were covered with hessian sacking to prevent desiccation while the trench was open. Any minor roots that were damaged were severed using secateurs to leave a clean wound which reduced the potential for infection with pathogens. The pipe was successfully installed and no impact upon the tree is envisaged.
This example demonstrates there are usually options available to allow retention of trees which are seen to be ‘in the way’. Middlemarch’s Arboricultural Team are more than happy to discuss ideas with clients. You might be surprised how simple some options are and what a difference retaining trees makes to a development.