When conducting development work or highway improvement works near to trees, it is essential that everyone working on the site adopts all the measures identified to retain trees and minimise damage. It is also essential that all site operatives (site managers, clerks of works, all contractors’ operatives including subcontractors etc.) understand what is needed.
A meeting should be arranged before work begins with everyone involved to establish good communication and identify all the requirements for retaining trees. Regular meetings and toolbox talks should then take place while the works are ongoing to identify additional requirements and potential problem areas. It is important that all appropriate practices and protection methods are written into contracts, along with penalty clauses which provide an incentive to adopt good practice.
Tree protection measures must be thorough and should be put in place before the works begin and maintained until the works are finished. Inadequate or inappropriate protection measures are a waste of money and can lead to significant damage, which may only become apparent months or years after the works are completed. A damaged or deteriorating tree due to poor site management can present a significant danger to users of the highway and loss of important local amenity and natural capital.
Figure 38: Retained mature tree showing signs of stress and damage from construction activity. New buildings have been erected too close to the existing mature tree which is, leading to health and safety problems in the future.
Figure 39: Building so close to retained trees leads to problems with shade and leaf litter. This can result in trees being mutilated and high future maintenance costs.
The council’s forestry officer and/or the consultant arboriculturalist should be involved at an early stage so that they advise on retaining existing trees and planting new specimens. The potential growth of retained trees, their future compatibility with new and existing highway features and how near new and existing service runs will be all must be considered. An appropriate protection zone must be provided around trees that are to be retained. All necessary tree maintenance work, both before and after construction, must be carried out by trained operatives in consultation with the council’s forestry officer.
Avoiding damage to trees during construction works
Installing Highway Equipment
When designing and planning highway equipment, consider the location of trees, whether they are on the highway or on nearby property. Care should be taken to avoid installing this equipment within a tree’s potential rooting area and within its crown or potential growing space. Site equipment such as road signs, street lights etc. should be sited to avoid damage to trees during installation and to avoid the need for regular pruning to maintain visibility.
Excavating trenches |
To install and maintain services, for |
---|---|
Alterations in soil level |
Raising or lowering the soil level. |
Installing non-porous surfaces |
Affects soil aeration and drainage. |
Compacting the surface |
By plant, vehicles and storing material. |
Soil pollution |
Storing toxic materials (for example, diesel |
Physical damage |
By plant and machinery to a tree’s roots, |
Changes to soil hydrology
|
Caused by changes to drainage which |
Fires |
Burning unwanted material within the tree’s root spread can cause considerable damage to the tree’s roots, trunk and branches. |
Exposure |
Damage caused by increased levels of sunlight and wind when neighbouring trees are removed. |
Figure 39: Damage to trees during construction works
A tree’s root system can extend radially (outwards) to a distance much greater than the tree’s height. Ideally the whole of this area should be protected and remain undisturbed during construction work.