Development areas often have trees occupying a substantial part of the site. In many cases, particularly in urban environments, trees can become a very emotive issue with project stakeholders. The loss of, or damage to, a tree may, at best, require complex mitigation and, at worst, be considered unacceptable.
agb Environmental’s top tips for building near trees ensures you remain informed about the possible challenges ahead.
1. Carry out an arboricultural assessment – quickly.
An Arboricultural Implications Assessment – AIA (to British Standard BS5837:2012 Trees in relation to design, demolition and construction. Recommendations) is the standard requirement of Local Planning Authorities when considering trees in development projects.
The AIA is made up of several parts; first the tree survey detailing the existing tree stock, namely it’s quality and potential longevity. This creates a crucial baseline to evidence and justify further actions.
Second is the Tree Constraints Plan, which uses standardised formulas (adjusted where necessary using professional judgment) to detail the Root Protection Areas (RPAs). These RPAs become the zone within which any construction activity may adversely affect the tree. When combined with the Tree Survey, this becomes an excellent feasibility assessment for any development project. If undertaken, it is essential this report is passed to the design team.
Finally is the Tree Protection Plan, which can only be completed when the scale of the development is known. This details the specific protection measures required, including tree fencing and signage. Combined with this is an outline Arboricultural Method Statement that provides guidance on the methods required to oversee the protection of the trees during construction.
Once the AIA is approved by the Local Planning Authority, a detailed Arboricultural Method Statement (AMS) can then be produced and approved. The requirements of the AMS will be specific to each project, and may require a significant amount of project team input.
2. Be aware of potential root damage.
Approximately 90-95% of tree root systems are located within the top metre of soil and within the set distance from the tree based on the size of the tree. The plan view of this area is termed the Root Protection Area (RPA) and is the area that requires the greatest consideration prior to any disturbance.
By making the project team aware of the RPA and mapping it on any feasibility plans, the project won’t incur the expense of changing plans as a result of tree constraints further into the project. Any interactions with the RPA should be discussed with the agb Environmental Arboricultural specialist as soon as possible.
An arboricultural feasibility report from agb Environmental can help to support the development feasibility study and understand what constraints may require detailed consideration.
3. Mark construction zone boundaries.
On development plans, the developer should mark areas where heavy equipment is likely to be used, where building materials will be stockpiled and where soil will be permanently added or removed. This will give an indication if any trees are close to these disturbed areas.
The Tree Protection Plan will detail how and where to mark out the tree fencing so that trees are protected on site during the construction process.
4. Protect and preserve soil for future tree planting.
Sometimes it is not possible to avoid an interface between the Root Protection Areas (RPAs) and the construction activities or the development itself.
Any RPAs that are likely to be impacted by construction activities will need protecting if they are to continue to support a healthy and viable tree. This can be achieved in a variety of ways, including using a geo-cell type surfacing. This helps to reduce the ground pressure and avoid compaction which can damage roots and tree health.
Where the development plan has a direct interface, a variety of methods can be employed, including using piles, high level beams and careful arboricultural techniques to manage roots etc. In fact, in most circumstances, a workaround can be found. However, the question becomes one of the value of the tree and the cost of the revised development proposal.
5. Consider the wider implications.
Trees offer more than simply a visual amenity; they can be important locations for protected species, and may have an impact on the ground conditions for areas of hard standing or foundations.
Understanding the wider implications is important when considering which trees should be protected and remain, and which are marked to go. agb Environmental can assist with this through our ecology and geotechnical services.
For further advice on tree preservation and other aspects of arboriculture please contact Alex Brearley on 01638 663226 or email firstname.lastname@example.org.