How trees should be treated during development projects

WHILE out with my family one weekend, I was shocked to see the very real consequences of not installing any tree protection measures on a local development site. As an arb specialist, I know there are rigorous regulations in place related to the treatment of trees under the Town and Country Planning Act that all developers and construction site managers should be aware of.

It was clear these were not being adhered to on this site. A significant limb had been ripped from the trunk of a pedunculate oak leaving a wound exposed to pathogens. As well as this, excavated soil was being dumped on already compacted clay-rich soil, right up to the base of the only two retained trees at a new housing development and there was no tree protection fencing in place to prevent physical damage to the tree, with soil compaction from heavy plant machinery moving through the root protection area (RPA).

Equally worrying was the condition of an ash tree. Already a tree in decline, the soil compaction and increased ground levels will certainly not help the tree and I do not hold out much hope for its long-term survival. This is a shame as, with suitable remedial actions, the tree could have contributed to the amenity value of the development for a good number of years.

Neil Francis, Thomson Environmental Consultants.

HOW TREES ARE PROTECTED BY LAW

Under the UK planning system, local planning authorities (LPA) have a statutory duty to consider the protection and planting of trees when granting planning permission for proposed developments.

Government policies are clear that special consideration should be given to veteran trees – a tree that is of interest biologically, culturally or aesthetically because of its age, size or condition – and planning authorities encourage the conservation of these trees as part of development proposals. Because of this, most local planning authorities have a policy on tree preservation in their local planning documents.

Where trees may be impacted by a proposed development, the LPA will usually require an arboricultural impact assessment (AIA) which identifies those trees that can realistically be retained, and recommends any necessary mitigation, and an arboricultural method statement (AMS) which details how trees that are to be retained will be protected during the development works. Planning permission may not be granted for developments that affect trees with a tree preservation order (TPO) unless the local authority is convinced the need for the development outweighs the amenity value of the trees. In this case, there would usually be a requirement to plant trees to compensate for the loss either on or near the site.

A fundamental part of the AIA and AMS is the tree protection plan (TPP), which shows the location of tree protection fencing, the extent and type of ground protection and other physical measures that protect the trees and their root protection area.

WHAT HAPPENS IF YOU DON’T COMPLY

On returning to the same development site a few weeks later, I found the excavated soil had been graded and harrowed to a coarse tilth. Levels had also increased significantly. Even more surprising was the fact that suitable tree protection fencing was available and could have been used to create a construction exclusion zone (CEZ) and prevent damage to the tree and the soil structure, but this had not been done.

As this example shows, developers do not always abide by the regulations attributed to tree protection, so our role as arb specialists on site is to make sure they do, preparing the necessary surveys and reports while ensuring construction staff and managers follow the correct procedures. Where local planning laws are not followed, alleged breaches are investigated. More specifically, if trees are at risk from a breach of planning control, the council has various options, including enforcement notices, stop notices, breach of condition notices and county or high court injunctions.

Any of these could put a project in jeopardy, so it is in the interests of all developers to take expert advice.

MITIGATION TECHNIQUES

During early surveys, one of the key considerations for the arb team is to preserve any mature trees within the site. Trees that are kept should be protected carefully during the development process. Damage can occur all too easily from root severance during excavations and soil compaction by vehicles or material. Protective fencing, if installed according to the AMS and TPP, can be an effective barrier to construction activity through the creation of a CEZ, a protected zone equivalent to the root protection area from which access is prohibited during the project lifespan.

When planting new trees, planting native species of local provenance is the standard we aim for. Newly planted trees are likely to require a period of aftercare until they become established.

EXAMPLES OF GOOD TREE PROTECTION

Briefing construction workers properly is key to good tree protection on site. At a development site where my arb team was working recently, robust and secure tree protection fencing had been installed around a silver birch tree to create a suitable CEZ. The construction staff on site had been briefed about tree protection and were respectful of this.

Where retained trees are not sufficiently protected and, crucially, the CEZ is breached, the LPA or tree officer may intervene to ensure compliance with the AMS and TPP. For example, Solihull Metropolitan Borough Council routinely monitors a proportion of new approved developments to ensure planning conditions are complied with.

It is obvious that not complying with the relevant legislation can result in project delays, budget overrun and unwelcome publicity. It is therefore in everybody’s interests to ensure the correct procedures are followed.