Outline for an arboricultural method statement

An arboricultural method statement outline has one job: to show, operation by operation, how the trees that are being kept will survive the construction of the thing that was approved. It is written after the impact assessment, usually to discharge a condition, and it is the document that the council's tree officer reads with a drawing in the other hand.

Most method statements are refused for the same reason. They describe intentions rather than operations. A statement saying that care will be taken near trees is worthless. A statement saying that the bay window footing within the root protection area will be hand dug in 300 mm lifts under supervision, with roots over 25 mm diameter retained and severed cleanly, is a document an officer can discharge.

How the method statement follows the impact assessment

The sequence under BS 5837:2012 runs from survey to constraints to impact assessment to method statement. The survey records the trees and their categories. The tree survey and arboricultural impact assessment identifies what the proposal does to them. The method statement explains how the retained trees are protected during the works, and the tree protection plan shows it on a drawing.

Write the method statement against the approved drawings, not the planning application drawings, where these differ. Where the layout changed at committee or by condition, the method statement has to match what is actually consented, and tree officers check.

State at the outset which trees are being removed with consent, which are retained, and which are on adjoining land. Trees on a neighbour's side of the boundary cause more disputes during construction than trees on site.

Root protection areas and the construction exclusion zone

The root protection area is calculated from stem diameter under the method in BS 5837, giving an area that is then plotted as a polygon adjusted for known constraints such as a building, a road or a change in level. Two points that get lost in practice: the area may be reshaped but not reduced without justification, and the plotted shape has to be consistent between the method statement and the tree protection plan.

The construction exclusion zone is the part of the site that is fenced off and kept clear. Set it at the root protection area unless there is a reason to vary it, and say what the reason is.

List, for each tree or group:

• stem diameter and the resulting root protection area
• the shape of the plotted area and any adjustment, with the reason
• whether the construction exclusion zone matches it
• what, if anything, is proposed inside it

That last line is the one the officer reads first.

Tree protection barriers and ground protection

Specify the barrier rather than naming it. For most sites that means a scaffold framework with vertical and horizontal members, braced, with weldmesh panels fixed to the uprights and the whole standing around 2.3 metres high, carrying signs identifying it as a construction exclusion zone. Say where it goes, when it is erected, and who checks it.

The timing is the part that fails. Barriers erected after the site strip protect nothing. Put the erection of fencing as the first operation in the sequence, before any plant arrives, and make it a hold point requiring the arboriculturist's sign off.

Ground protection is for areas where access inside the root protection area is unavoidable. Specify the build up: a geotextile separation layer, a load-bearing surface such as interlocking ground protection panels or a scaffold board platform on scaffold frame, or an engineered granular layer over geogrid where heavy plant is involved. Give the design loading the surface is intended to carry, and say what it must not be used for.

No dig construction and cellular confinement

Where a driveway, path or parking area falls within a root protection area, no dig construction is the usual answer. The principle is to build up rather than dig down, so the existing soil profile is not excavated and the roots are not severed.

A typical specification describes the removal of soft landscaping only, a geotextile layer laid on the existing grade, a cellular confinement system filled with angular no fines stone, a binding layer, and a permeable surface course. The permeability matters for the tree as much as for drainage, because sealing the surface above roots removes the air and water exchange the tree depends on.

Set out the levels. No dig means the finished surface sits above the existing ground, and the resulting step at the edge of the construction has to work with thresholds, gullies and adjoining levels. A no dig driveway that has to meet an existing garage threshold at the same level is not a no dig driveway.

Where the structure needs engineering input, say so and name the discipline. The arboriculturist specifies the arboricultural requirements; the engineer designs the construction to carry the loads.

Services, drainage runs and trenching near trees

Underground services kill more retained trees than foundations do, because the route is drawn late and dug fast. Deal with them explicitly.

The method statement should show the route of every service and drainage run against the root protection areas, then state for each one whether it is outside the area, routed around it, or installed by a method that avoids root severance. Trenchless techniques, a shared service corridor outside the protection areas, and hand digging with root retention are the three usual answers.

Where hand digging is used, specify it: excavation in shallow lifts using hand tools or compressed air soil displacement, roots over a stated diameter retained and bridged, smaller roots cut cleanly with sharp tools rather than torn, exposed roots wrapped and kept damp, and backfill with a suitable material rather than compacted spoil.

Supervision, hold points and site monitoring

Conditions requiring a method statement usually also require arboricultural supervision. Set out who supervises, their qualification, and the specific operations they attend rather than a vague monitoring commitment.

A workable schedule looks like this:

1. Pre-commencement site meeting and inspection of erected barriers, with written confirmation to the authority.
2. Attendance during demolition and site strip adjacent to retained trees.
3. Attendance during any excavation inside a root protection area.
4. Attendance during no dig construction, at subgrade and at completion of the cellular layer.
5. Attendance during service installation where routes pass near protection areas.
6. Final inspection and a closing report before barriers are removed.

Record each attendance in a site monitoring log with dates, photographs and any instruction given. That log is what you send the council if a complaint arrives about a machine inside the fencing. The log sits alongside the site controls in the construction management plan checklist for a tight site, and the two documents should not contradict each other on access routes or material storage.

The tree protection plan drawing and what it shows

One drawing, at a readable scale, showing: retained trees with reference numbers matching the survey, trees to be removed, root protection areas plotted as polygons, the line of protective fencing, areas of ground protection, no dig construction areas, service routes, site access, and the position of material storage, site cabins, the wheel wash and the concrete washout.

The last items are the ones tree officers look for, because the fencing is usually drawn correctly and the welfare cabins are usually parked under the biggest tree on site. Mark a dedicated storage and parking compound outside all protection areas, and say that no storage, mixing or vehicle movement is permitted inside the construction exclusion zone.

Discharging the condition and the monitoring schedule

Submit the method statement and the tree protection plan together, with a short covering note listing the condition number, what is submitted, and where in the statement each requirement of the condition is answered. Officers discharge conditions faster when they can see the requirement and the answer side by side.

Expect to be asked for the supervision schedule in writing and for confirmation that fencing is in place before works start. Build the fencing inspection into the programme as an activity with a date, and keep the written confirmation. And if the layout changes during construction, submit a revised statement rather than relying on a verbal agreement with the officer, because the condition is discharged against a specific document. A closing check on consistency between drawings and text, along the lines of an internal quality check before anything leaves the office, catches most of the errors that cause a refusal to discharge.

This is general guidance, not legal advice, and British Standard 5837:2012 should be read in full by the person preparing the statement. Councils usually expect an arboricultural method statement to be prepared by a suitably qualified arboriculturist, and professional review is strongly advised before submission.

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