Tree Condition Survey
Kingston Village Green
Undertaken by Nicholas D Jones NCH Arb A I Hort
On behalf of Kingston Parish Council
May 2008
Contents
Introduction
The Survey
General Observations
Conclusions and Recommendations
Introduction
This survey has been commissioned by Kingston Parish Council to ascertain the general condition of the mature trees within the boundary of Kingston village green. The site was visited on 12th May 2008 and the survey undertaken.
Particular attention has been paid to potential Health and Safety risks with appropriate remedial action recommended. All trees have been assessed from ground level only using non invasive methods of inspection.
The Survey
Trees over 750mm diameter at around breast height have been individually tagged with a reference number.
The survey information collated is as follows:
More over all trees surveyed have been given an amenity value score which gives an indication of the trees importance with in the local environment. The scale is scored between 1 and 5 with 1 being low 5 being high. Factors such as species diversity, dimensions, ecological value and aesthetic worth are key factors in determining the value. This information is of key importance when determining the extent of any prescribed works when considering the hazard risk rating.
Furthermore all trees have been risk assessed and assigned a hazard risk rating which is defined as: 1 = low risk (Green), 2 = medium risk (Amber), 3 = high risk (Red).
In a generic sense, all trees have the potential to cause damage to differing degrees. A risk assessment exercise such as this survey is undertaken for each situation, considering the type and likelihood of damage. There is, therefore, no such thing as a perfectly safe tree, and there is always a residual risk even in a tree with no defects. The purpose of this survey is to evaluate the hazard that any defects present, and the risk of damage to people or property if a tree or part of it fails, and to take appropriate action to reduce the risk to an acceptable level. Health and safety legislation recognises that it is unfeasible and in many cases unrealistic to eliminate risk entirely.
Green - Trees displaying no evident major defects and are therefore assumed safe at the time of inspection. Recommendations for work are based on abating nuisance or obstruction issues. Furthermore to promote good form and eliminate so far as possible any future risk. Green works should be undertaken with in 18-36 months.
Amber - Trees displaying a defect which has the potential to fail. Although at the time of inspection not deemed significant enough to warrant urgent attention. Amber works should be undertaken with in 6-18 months.
Red - Trees displaying significant defects and posing an immediate risk to health and safety. Red works should be undertaken within 6 months. Recommendations will be made for remedial health and safety works to preserve trees or make safe where practicable.
General Observations
In general terms the trees on the village green are in reasonable condition. Incidence of decay is low as is that of infectious disorders. There are as always exceptions with decay evident in two of the trees adjacent to the highway boundary with St Pancras Green. However this risk is easily manageable with remedial action.
On the southern most boundary there are six Sycamores that have previously been heavily reduced/pollarded. There is dense regrowth as a result of this drastic pruning and the pollard points are showing signs of decay.
Furthermore in this area tree number 92 has a significant structural defect in the form of an included bark union (Plate 1). The above ground failure of trees or sections of trees in weather extremes is largely attributable to such defects.
Plate 1
This form of defect is duplicated in tree number 90 (Plate 2).
Plate 2
Tree number 101 is a prominent tree in the locale. It leans significantly to the north and there is evidence of the root system lifting the adjacent flint wall boundary of the St Pancras Church (Plate 3).
Plate 3
Plate 4
Furthermore this tree is leaning over the electricity sub station (Plate 5). Should it fail structurally then the results could potentially be catastrophic.
Plate 5
Tree number 103 is another principle tree in the environment (Plate 6). It abounds the church yard of St Pancras Church and has been previously reduced. I am confident this tree is a veteran and has been coppiced historically which accounts for its multi stemmed nature (Plate 7). There is evidence of decay at the base of the tree however this appears not to be extensive. The exact extent of any decay is difficult to map however innovative technology now allows accurate mapping using a Picus Tomograph.
The Picus Tomograph utilises sound wave technology. The measuring is based on the fact that sound wood is a better sound wave conductor than wood damaged by decay. The device uses a series of sonic sensors which detect waves induced and propagated through the wood. Typically eight to twelve sensors are strategically placed around the tree at the level to be tested at known locations; these locations can be assigned with the use of the software or mapped quickly and accurately with the use of callipers. Each sensor is connected to a nail which is tapped through the bark and into contact with the wood. A small tap on a metal pin is all that is required to send sound waves through the tree, which are received and measured by all the other sensors.
Data collection software then takes all of these measurements and will generate a two dimensional colour tomogram of the tree stem at the test level.
The Resistograph functions by driving a micro drill (3mm tip, 1.1mm shaft) into the timber at constant speed using a Bosch drill attachment.
The differences in torque required to drill through different wood types are recorded, [less torque (power/force) is required to drill through decayed wood]. This is especially useful for drilling into the tree at an angle to determine the extent of decay below ground level.
Both tools are a useful means to determining the extent of decay present making risk management decision making more informed. This service is provided locally by J Harraway Tree Services (01903 756153/07831 651090). His web site is www.hts.gb.com.
Plate 6
Plate 7
Given this trees location and prominence in the local environment its retention is of paramount importance. In the absence of any diagnostic testing to ascertain the exact extent of any decay it is my professional opinion that this tree should be reduced by a further 30-40% to reduce the weight within the upper canopy and subsequently reduce the weight and wind loading stresses on the basal decay. Should this tree fail structurally the resultant damage could potentially run into several if not tens of thousands of pounds.
The woodland group of trees, numbers 58-90 adjacent to the southern boundary path contains some significant specimens. Only those worthy of note have been recorded in this survey with the remainder little more than overgrown scrub.
Conclusions and recommendations
The trees on and around the green are a valuable local resource that are individually and collectively of immeasurable amenity value. Their management is essential to retain this resource in a safe manner for both residents and visitors to enjoy. Whilst this involves a reasonable investment from the Parish Council to bring the trees to a standard the ongoing cost f maintenance should reduce annually if proactive maintenance is undertaken. I would advise that the trees are re-assessed every 12 months and that a full re-surveying is undertaken every 3-5 years.
Location map
