Hazardous tree inspection for TPO

NWS Aborist Jim Allitt recently advised on the management of a substantial oak tree subject to a Tree Preservation Order and within the Broads National Park.

Our client, Mr Coleman, had concerns over the extent of deadwood in the canopy, especially where it was close to his and a neighbouring property, but as also keen to retain it as a beautiful feature of his home.

Mr Coleman asked NWS to determine the condition of the tree and make future management recommendations. The tree was surveyed to look at issues such as weak unions or forks, cavities, and especially any defects hidden higher in the canopy.

Hazard tree feature – Branch failure

Sometimes hazards are obvious but subtler hazards may go unnoticed and mechanical failure may occur without specialist management.

Under the Occupiers’ Liability Act (1957 and 1984) the ‘occupier of the land’ where the tree is rooted has a duty of care to ‘take reasonable steps to prevent or minimise the risk of personal injury or damage to property’, both for visitors to the occupiers land (1057) and other persons (1984). The law is quite complicated.

To avoid or deal with risks while retaining the tree, a reasonable and balanced approach to future management requirements is needed, with a full understanding of calculated risk involved. In this case, NWS suggested a 2m, crown reduction and to clear larger deadwood from the canopy so that ‘sailing’ from the wind stressed the branch unions less.

Aerial tree inspection by Jim

Since the tree was protected, the works had to be agreed with the local planning authority, the Broads Authority. NWS’s successful application demonstrated that the works retained the screening the tree provided but were also necessary to reduce the risk the tree posed to the adjacent house and property.

Trees as assets : 7 rules for designing with trees

Trees on a site increase visual attractiveness, are great for wildlife and add considerably to property values. Maximising use of existing tree assets in designs will maximise the financial benefits for new developments. Here are NWS’s 7 tips:

  1. To maximise value from tree assets start at the concept stage; here a simple tree survey will suffice: a ‘Tree Constraints Plan’ with ‘Root Protection Areas’ (RPA).
  2. RPAs are minimum core areas to protect your trees; seek specialist advice if RPA conflicts with your design as to whether redesign is required.
  3. On sites with many trees, use BS5837 categorisation to prioritise the importance of individual trees, based on amenity, wildlife and landscape value.
  4. Allow room for future growth based on tree’s longevity; shading plans help design building orientation and fenestration.
  5. Allow for “hidden” issues for trees such as visibility splays, drainage (esp SUDS) and utility connection; trees with faults may need intervention to help them.
  6. An Arboricultural Impact Assessment (AIA) will help when instructing the contractor to protect trees plus organise site clearance, construction and final landscaping and planting.
  7. Find an arborist you can work with, seek their advice early and get their regular input.

If you are interested in how much your trees might add in value to your site, there are various techniques from the Capital Asset Value for Amenity Trees (CAVAT) through to ecosystem services calculations.

Jim calculates a tree’s RPA

 

Which tree survey do I need ?

Sycamore canopy in spring bud

Clients are often asked by planners or others for a tree survey, but are not always sure what type is needed.   We have outlined the different types of tree surveys and the reasons they are needed.

A. Development survey = BS5837:2012 ‘Trees in relation to design, demolition and construction- Recommendations’

A Development Survey also called BS5837 survey is the one normally required by Local Planning Authorities (LPA) for development and planning permission.

A competent “arboriculturalist” [ = tree person ] must inspect the trees on and adjacent to the site. The trees on site are assessed in terms of their retention value which includes their health, longevity and amenity impact.

Trees that are marked for retention, as well as any adjacent trees not on site but affected by development need to be protected from any potential harm that may occur during the demolition and construction phases of the project. This involves both above and below ground precautions. Above ground, the crown spread and dimensions of the tree will need protecting, below ground the roots of the tree are a constraint governed by the Root Protection Area (RPA).

( The RPA is the area the tree’s roots occupy – this requires fencing and ground cover to protect it from above ground operations.) Information on protective measures for the trees on site will be provided as part of the BS5837 report.

B. Tree Hazard Surveys

Where you are concerned about your “duty of care” over a tree, then a Tree Hazard Survey is the one you require.

All tree owners have a legal responsibility as their “duty of care” to ensure others are not at risk from falling trees and branches. You need to assess the level of risk involved on your land. The risk is generally assessed based on :

  1. The level, extent and type of access that people have to the land on which the tree stands or where the branches could fall.
  2. The condition and health of the tree.

The factors underlying the condition and health of the tree will dictate how often the tree should be re-inspected for potential hazards. Advice on mitigating hazards by undertaking tree work can be suggested as part of the inspection, which you need to act upon.

C: Advice on Tree Works

Tree works on trees in Conservation Areas or on those with Tree Protection Orders on them need a “Tree Works” application.

When carrying out any tree work it is always advised that a competent arborist be consulted, whether it is a consultant or a tree surgeon. Work should be carried out in line with the British Standard, BS3998:2010 ‘Tree Work- Recommendations’. Trees should be inspected before the work is carried out too ensure the best management practices are employed.

Trees in Conservation Areas and with TPOs often have high amenity value and are well loved by their owners, so are felt to be worth the extra investment.

D: Surveys for underground utility installations

As stated in NJUG Guidelines for the Planning, Installation and Maintenance of Utility Apparatus in Proximity to Trees, there are generally low incidence of damage to underground apparatus by trees where these installed within hard surfaces ( e.g. pavements ). However trees can have variable growing patterns in term of root structure, especially if there are below ground obstructions to root growth. This can make any changes on site in the trees RPA potentially hazardous. Work on operational land for utilities often requires no LPA application, however it is considered good practice to follow BS3857 to implement tree protection methods where possible.