Mike [SRMJ1]Hodson Esq.,

BSI

389 Chiswick High Road

London

W4 4AL

27th September 1999

Dear Sir

Ref.: Possible Revision of BS5837: 1991, Guide For Trees in Relation to Construction.

As you can see from the above letterhead I am an independent Arboricultural Consultant, and I deal with the guidelines of BS5837 on almost a daily basis. May I make the following comments on the current content of the standard? (Possible amendments are made within my text).

1. Paragraph 4.4.1. – May I suggest that “Arboricultural Consultants” are added to the list of bodies included in this paragraph? (i.e. “………survival through development ultimately depends on co-operation between Site Owners, Developers, Arboricultural Consultants, Contractors and Local Authorities”).

2. Paragraph 5.1.2. – Can I suggest that this paragraph recommends that any trees outside though within one tree length of the boundaries of the site, that could be affected by the proposed development, should also be includedconsidered in the land survey.

3. Paragraph 5.2.1. – I do not think “a person experienced in arboriculture” is a sufficient qualification for carrying out an assessment of species and condition of trees in a survey. Many surveyors themselves are experienced in arboriculture to some (minor) degree; this does not mean that they have the qualifications or underpinning knowledge to present an informed arboricultural opinion are qualified to assess species or condition. I suggest that the wording or this paragraph should be changed to: “the species and condition of all trees included in the land survey should be assessed by a qualified Arboricultural Consultant, or by a person qualified and experienced in Arboriculture.

4. Paragraphs 5.2.1, 7.4.5, 7.5.1 and 7.5.4. – Some of these paragraphs recommend that items should be assessed by a person experienced in arboriculture, others state that prior consultation should be with an Arboricultural Specialist. Surely these descriptions need standardising? In my viewIt may be generally more helpful if itshould either read either “A qualified Arboricultural Consultant” or “A qualified Arboricultural Specialist “. (Or maybe “a qualified arboricultural consultant or specialist”.)

5. Paragraph 5.2.2. (B)(1) – I would likeIt would make sense to see the word “slightly” removed from this paragraph. Virtually every mature tree is in a “slightly” impaired condition: the use of this word in this positioncontext means that very few trees can be judged as category “A” specimens. Removing this word would mean that many large healthy trees, which probably have minor defects, can be included in the “A” category.

6. Paragraph 5.2.2. [C)(2) – I don’t think that the term “immature trees” in this paragraph is sufficiently well qualified to distinguish it from “immature trees” in paragraph 5.2.2. (B)(2). Would it not be better to state here: “immature trees, which do not have the potential to develop into the high category”?

7. Paragraph 6.4.1. – ObviouslyPerhaps– this paragraph should now refer to NJUG10.

8. Paragraph 6.5.2. – Obviously – Perhaps this should refer to APN1(1996).

9. Paragraph 6.9. Implementation. – Within this section (or perhaps within a new section) I suggest that comments are inserted regarding the fact that the effects of construction on trees are often not fully understoodappreciated by people from other professions and trades, and that consequently it is advised that the following measures are taken.

A. An Arboricultural Impact Assessment should be drawn up by an Arboricultural Consultant, commenting on the likely effect of the proposals on the adjacent trees. This should include a Method Statement outlining the methods and sequencing of works in proximity of the trees to be retained. This should cover the position and type of all protective fencing and any other types of tree protection deemed necessary.

B. A pre-contract site meeting should be held between the Arboricultural Consultant, the Site Manager, and if deemed necessary, the LPA Tree Officer. At this meeting the methods of tree protection outlined in the Method Statement should be fully discussed, so that all aspects of their implementation and sequencing are made clear to all parties. Any clarifications or modifications to the Method Statement should be recorded, and circulated to all parties in writing. If appropriate, the tree surgery contractor should also attend this meeting.

C. Adequate Arboricultural Supervision should be implemented where necessary. This will normally be necessary to cover the position and compliance of the protective fencing (see Section 8.2 of the Standard), compliance with additional precautions (see Section 8.4 of the Standard), and direct supervision of any ground works that are carried out within the root protection areas of trees. Supervision should be carried out by a qualified Arboricultural Consultant/Specialist.

10. Paragraph 7.5.5. – In my view This is the worst paragraph in the current Standard, and may through misinterpretation have led to a large amount of unacceptable root damage since the publication of the document. It states that “If it is deemed acceptable tofor construction works to occur closer than the minimum distance” …………deemed acceptable by whom? This must again be related to our (now standardised) qualified Arboricultural Consultant or Specialist. In my view The minimum distances should not be reduced by up to one third on one side with any mature trees. It should only be done with semi-mature and young trees; or there may be cases where certain trees have an obviously restricted root run on a particular side, where a reduction could therefore be appropriate. be determined by the qualified arboricultural specialist/consultant on each and every occaision.

11. Paragraph 7.5.7/7.5.8. – This should again be related to NJUG10.

12. Table One.

12.1. Tree “Vigour” should correctly be called Tree “Vitality”, since vigour is genetic.

12.2. Might it be an idea to relate tree vitality to the categories of (vigour) to be found in the Arboricultural Association subsidence risk assessment handbook? I don’t suggest the British Standard uses eight different classifications of “vigour”, simply that the terminology is compatible. Perhaps we should remove all reference to such notions and leave the whole tree assessment process to the arboricultural consultant specialist?

12.3. I am aware that work on the tolerance of disturbance of individual species is still at an early stage. Despite this I feel that it may be helpful to add such a column to Table one, even if it is fairly basic at this stage. It would certainly assist the retention of those species which are known to be particularly susceptible to disturbance, such as beech and oak.

12.4. The minimum distance for young trees of normal vigour with trunk diameters of under 200mm is quoted as 2m. I believe that this is too small and that a minimum of 3m should be recommended. 2m may give protection for extremely young trees that have been planted within the last few years, but does not give them much room for future growth; it is certainly not enough for some quite large specimens of long lived species (such as oak), which have not yet reached one third life expectancy. See 12.1 12.2 above.

12.5. As this table is often used alone, without reference to the rest of the document, I think it would be a good idea to put some clarification under the headings, as is currently done under tree age. To be specific, “trunk diameter” should state “at 1.5m above ground level”, and minimum distance should state “between centre of trunk and protective fencing or nearest point of disturbance” (see paragraph below). The centre of the trunk is a point unobtainable for accurate measurement, it would be of arboricultural benefit to measure from the nearest part of the stem or root buttress to the actual or proposed nearest point of construction or ground alteration.

12.6. In my experience This table (“minimum distances for protective fencing around trees”) is all too often taken to mean “minimum distances between trees and the nearest point of a proposed building”. This ignores the fact that trenches for foundations, particularly on sandy soils, often have to be graded back and can reach at least a metre further towards the tree in some circumstances, and that space is needed for access and scaffolding. The result is often that root protection areas are ‘eaten into’, and un-necessary damage done. The idea of a minimum distance between a tree and protective fencing is not so easily grasped by architects, planners, developers etc. as is the distance between a tree and a proposed building or structure, both of which appear in black and white on a layout plan. So, might it not be a good idea to re-title the Table “minimum distances between trees and proposed structures”, and increase all the minimum distances by 2m, thus giving a 2m safety margin for trenching, scaffolding etc? Guidance on the position of protective fencing could then be given separately, specifying that it should either be erected at the minimum distance as given, or at a maximum of 2m from the proposed structure if this is not possible. This would be easier for architects and developers to understand, and would give all trees a 2m safety margin. See 12.5 above.

12.7. Under trunk diameter: further guidance should be given regarding multi-stemmed trees. In my view a twin-stemmed tree should be assessed as the diameter of the larger stem plus fifty percent, and a three-stemmed tree as the diameter of the larger stem plus seventy-five percent. (But I would be interested to hear what the AAIS may have to say about this.) With multi-stemmed trees the branch spread as shown in Figure 2 may be the best solution: this should be pointed out. See 12.5 above.

13. Paragraph 8.2.2. – This paragraph should include reference to “Heras” fencing, but noting that :

It must also be supported by horizontal framework of scaffolding,

That is only suitable for level ground and should not be used on slopes.

14. Paragraph 8.2.2. – This paragraph states that the framework of scaffolding should be “supporting either chestnut pale fencing or chain link fencing”. I suggest that whether chestnut pale fencing, chain link fencing or Heras fencing is used, all should be attached to the scaffold framework by clamps, or by stout galvanised wire. On some sites the chestnut fencing appears to be just leant against the scaffolding framework, and can easily be rolled back or be blown over.

15. Paragraph 8.3.1. - This paragraph shouldmight refer to APN1, and refer to the already mentioned need for any works within root protection areas to be supervised by a qualified Arboricultural Consultant/Specialist. It should also make allowance for the use of “rolling road” type of temporary roadways.

16. Paragraph 9.1.1. – This paragraph should refer to who should prepare the plan or list of all trees for removal or surgery. Once again, I think this should be a qualified Arboricultural Consultant/Specialist.

17. Section 11. Hard Surfaces Around Existing Trees. – ObviouslyPerhaps this should be revised in the light of APN1, and Figure seven shouldcould be replaced by the drawing in APN1. Perhaps APN1 in its entirety could be used as chapter 11 of The British Standard?

18. Paragraph 13.1.2. – Here we have another variation in the description of a tree specialist:: in this case it is a “Specialist with experience in the detection of early signs of decline in tree health” (!). Again this should be standardised with the rest of the document “Qualified Arboricultural Consultant/Specialist”.

19. Paragraph 13.3.1. – Again, this should refer to the qualified Arboricultural Consultant/Specialist.

20. Paragraph 16.1, 16.3. – As above, the qualified Arboricultural Consultant or Specialist should be mentioned in these paragraphs, to replace the “person experienced in Arboriculture” (16.1).

I hope you will find some of these comments and suggestions helpful. If you have any comments or queries, please do not hesitate to contact me at the above number or address.

Yours sincerely,

Simon Jones

[SRMJ1]1Ready to edit 270999 AMP