BS 5837:2012 Trees in relation to design, demolition and construction – Recommendations

30 April 2012 sees the withdrawal of BS 5837:2005 Trees in relation to construction – Recommendations and its replacement with BS 5837:2012 Trees in relation to design, demolition and construction – Recommendations.

A number of significant changes have been introduced into this new issue of the standard which, when taken together, have resulted in a significantly better document for the arboriculturist, and so for the trees affected by the proposed development.   By seeking to standardise the way arboricultural matters and all the other issues in the planning process are dealt with the standard may also help the project arboriculturist climb the ladder of esteem with all the other professionals involved in a particular development proposal – no longer will the arboriculturist be talking about a different timetable from the designers and developers for example.

A significant commercial consideration for all parties involved in the planning application is that the standard suggests that the arboricultural method statement with the application be submitted simply as heads of terms as an acknowledgment that the detail of the application may change as it is considered by the local planning authority.   Once planning permission has been granted then greater input will be from the project arboriculturist to produce a suitably detailed arboricultural method statement, including an auditable system for monitoring a schedule of specific site arboricultural events on site.   All parties need to understand this shift in the balance of the arboriculturist’s work profile compared to the requirements that have existed for the past 7 years under the 2005 release of the standard.

The 2012 standard states:

5.4          Arboricultural impact assessment

5.4.1 The project arboriculturist should use the information detailed in 5.2 [Constraints posed by existing trees] and 5.3 [Proximity of structures to trees] to prepare an arboricultural impact assessment that evaluates the direct and indirect effects of the proposed design and where necessary recommends mitigation.

5.4.2 The assessment should take account of the effects of any tree loss required to implement the design, and any potentially damaging activities proposed in the vicinity of retained trees.   Such activities might include the removal of existing structures and hard surfacing, the installation of new hard surfacing, the installation of services, and the location and dimensions of all proposed excavations or changes in ground level, including any that might arise from the implementation of the recommended mitigation measures.   In addition to the impact of the permanent works, account should be taken of the buildability of the scheme in terms of access, adequate working space and provision for the storage of materials, including topsoil.

and:

6          Technical design

COMMENTARY ON CLAUSE 6

Technical design [RIBA stage E, see Table 1 below] includes information sufficient to provide a high level of confidence in the outcome for trees retained on development sites.   Where planning permission or other statutory controls apply, details might need to be submitted in draft form or heads of terms to allow for changes to the design that might occur after permission has been granted.   In these cases, it will be necessary for the project arboriculturist to set out a series of parameters for construction activity (e.g. where service routes and/or construction activity should not occur), based on the RPA and the physiological needs of the tree, to which the finalized specifications and statements will apply.

 6.1          Arboricultural method statement

6.1.1 A precautionary approach towards tree protection should be adopted and any operations, including access, proposed within the RPA (or crown spread where this is greater) should be described within an arboricultural method statement, in order to demonstrate that the operations can be undertaken with minimal risk of adverse impact on trees to be retained.

6.1.2 The arboricultural method statement should be appropriate to the proposals and might typically address some or all of the following, incorporating relevant information from other specialists as required:

a)   removal of existing structures and hard surfacing;

b)   installation of temporary ground protection (see 6.2.3);

c)   excavations and the requirement for specialized trenchless techniques (see 7.7.2);

d)   installation of new hard surfacing – materials, design constraints and implications for levels;

e)   specialist foundations – installation techniques and effect on finished floor levels and overall height;

f)    retaining structures to facilitate changes in ground levels;

g)   preparatory works for new landscaping;

h)   auditable/audited system of arboricultural site monitoring, including a schedule of specific site events requiring input or supervision.

6.1.3 The arboricultural method statement should also include a list of contact details for the relevant parties.

 The table below is taken from Annex B of the standard and refers to the nature and level of detail of information required of the project arboriculturist at particular stages of the planning process to enable a local planning authority to properly consider the implications and effects of development proposals upon the existing tree stock:

Stage of process	Minimum detail	Additional information
Pre-application (RIBA Work Plan stages A – D)	Tree survey	Tree retention/removal plan (draft)
Planning application (RIBA Work Plan stage D)	Tree survey (in the absence of pre-application discussions) Tree retention/removal plan (finalized) Retained trees and RPAs shown on proposed layout Strategic hard and soft landscape design, including species and location of new tree planting Arboricultural impact assessment	Existing and proposed finished levels Tree protection plan Arboricultural method statement – heads of terms Details for all special engineering within the RPA and other relevant construction details
Reserved matters / planning condition	Alignment of utility apparatus (including drainage), where outside the RPA or where installed using a trenchless method Dimensioned tree protection plan Arboricultural method statement – detailed Schedule of works to retained trees, e.g. access facilitation pruning Detailed hard and soft landscape design	Arboricultural site monitoring schedule Tree and landscape management plan Post-construction remedial works Landscape maintenance schedule

The standard suggests a number of minor changes to the parameters required to be captured by the initial tree survey in clause 4.4.2, for example:

·         the exiting height above ground and direction of growth of the lowest branch is to be recorded,

·         the way that the estimated remaining life expectancy is expressed has been changed,

·         Category U replaces R – whilst the trees may have no value there may well be no overriding need to remove them.

In addition the standard changes the way the RPA is to be calculated and plotted and no longer allows an RPA to be off-set but will accept a modified RPA when it can be justified (clause 4.6.3) on defendable arboricultural grounds.

Table 1 below is an adaption of that included as Figure 1 on page 2 of the standard; I have added the descriptions from the RIBA Plan of Work from http://www.pedr.co.uk/textpage.asp?menu=1a&sortorder=130&area=main viewed on 30 April 2012:

 

RIBA work stages			Description of tasks under RIBA plan of work	BS 5837 reference and clause number	Site operations under BS 5837 (clause number)
Preparation	A	Appraisal	Identification of client's needs and objectives, business case and possible constraints on development. Preparation of feasibility studies and assessment of options to enable the client to decide whether to proceed.	Topographical survey and soil assessment (4.2 and 4.3) Tree survey (4.4) Tree categorisation (4.5)	Vegetation clearance if required for survey.
	B	Design brief	Development of initial statement of requirements into the Design Brief by or on behalf of the client confirming key requirements and constraints. Identification of procurement method, procedures, organisational structure and range of consultants and others to be engaged for the project	Identify tree constraints and root protection areas (4.5, 4.6 and Clause 5).
Design	C	Concept	Implementation of Design Brief and preparation of additional data. Preparation of Concept Design including outline proposals for structural and building services systems, outline specifications and preliminary cost plan. Review of procurement route.	Identify and review potential trees for retention and removal (Clause 6)
	D	Design development	Development of concept design to include structural and building services systems, updated outline specifications and cost plan. Completion of Project Brief. Application for detailed planning permission.	Produce new planting and landscape proposals (5.6) Produce tree protection plan (5.5)
	E	Technical design	Preparation of technical design(s) and specifications, sufficient to co-ordinate components and elements of the project and information for statutory standards and construction safety.	Resolve tree protection proposals (6.2) Agree new utility apparatus locations, routes and arboricultural methodologies (6.1 and clause 7)
Pre-construction	F	Production information	Preparation of production information in sufficient detail to enable a tender or tenders to be obtained. Application for statutory approvals. Preparation of further information for construction required under the building contract.	Schedule trees for removal and pre-construction tree works (including access facilitation (5.4 and 8.8)
	G	Tender documentation	Preparation and/or collation of tender documentation in sufficient detail to enable a tender or tenders to be obtained for the project.	Identify tree protection measures and include them in all relevant documents (6.2)
	H	Tender action	Identification and evaluation of potential contractors and/or specialists for the project. Obtaining and appraising tenders; submission of recommendations to the client.
Construction	J	Mobilisation	Letting the building contract, appointing the contractor. Issuing of information to the contractor. Arranging site hand over to the contractor.	Site monitoring and intervention as required (6.3)	Physical barriers erected (6.2) Site clearance and demolition (clause 7) Access, storage and working areas installed (clause 6)
	K	Construction to practical completion	Administration of the building contract to Practical Completion. Provision to the contractor of further Information as and when reasonably required. Review of information provided by contractors and specialists.		Construction (clause 7) New planting (clause 8)
Use	L	Post practical completion	Administration of the building contract after Practical Completion and making final inspections. Assisting building user during initial occupation period. Review of project performance in use.	Inspection of trees and surrounding environment (including relationship to new structures) (8.8) Recommendations for post-completion management (8.8)	Remedial tree works if required

Another change from the 2005 release refers to the barriers and ground protection that may be required to prevent damage to the retained trees or their RPA – under the previous release of the standard the technical specification was clearly laid out, under the current issue the requirement is that the barriers be effective, which will mean different things on different sites.

One thing that has not changed with the introduction of the new standard is the opportunity for carefully considered arboricultural interpretation at every stage of the planning process when following the a particular development proposal.