SPECIFICATION FOR TREE FELLING,

SPECIFICATION FOR TREE FELLING,

PROTECTION AND TRANSPLANTING

1.00 TREE FELLING AND TREE PROTECTION

1.10 Tree Felling

1.20 Work Near Existing Trees

1.30 Protection of Existing Trees and Woodland Areas

1.40 Pruning of Existing Trees

2.00 TRANSPLANTING

2.10 Transplanting of Existing Trees

2.20 Tree Surgery Works

2.30 Sequence of Transplanting Operations

2.40 Maintenance Operations

1.10 TREE FELLING

Prior to starting any tree felling works all trees to be retained shall be identified and the necessary tree protection fencing installed. (See 1.30)

Felling of trees to be removed shall involve the complete removal of trees indicated, including stumps, by one of the following methods to be approved by the Architect before work commences:

(a) Bulldozer

A bulldozer shall be used to push over the whole tree, which shall then be cut by chain saw and removed, from Site. The method shall only be used where no trees are to be retained.

(b) Winches

Power mounted or hand winches shall be used for pulling over the whole tree, the main support roots having first being severed either by mechanical means or by hand grubbing. Preserved trees shall not be used as anchor points for winching without approved adequate protection.

Felling by this method shall be in accordance with BS 3998 (1989), either felling the whole tree at once or in sections. The stump shall be removed by hand grubbing and winching, stump cutting machine, hydraulic lifting or another method approved by the Architect before work commences.

1.20 WORKS NEAR EXISTING TREES

(a) Where excavation is required near existing trees for construction of works, the following precautions shall be taken to protect the roots:-

(i) Roots temporarily exposed during excavation shall be wrapped with damp straw or hessian during construction of the works. Cutting of the roots shall be kept to a minimum;

(ii) Before backfilling, roots shall be cut cleanly back to undamaged tissue and treated with an approved fungicidal gel.

(iii) Excavated trenches around tree roots shall be backfilled with topsoil mixed with an approved conditioner as specified, including sufficient slow release fertilizer to assure a rate of application of 500 g/m.

1.20 (b) Trench excavation for services, including drainage and sewage, should not come within the spread of the tree crown. Detailed location of services shall be agreed with the Architect before excavation commences if this minimum cannot be achieved. Large roots (i.e. greater than 75mm in diameter), exposed in trench excavations and above the final line of the installation shall be preserved, and excavation close to trees shall be carried out with particular care to ensure this. Following installation of the services, severed roots shall be cut back cleanly to undamaged tissue and treated with an approved fungicidal gel. Trenches shall be backfilled with topsoil as required, including approved soil conditioner and slow release fertilizer to achieve a rate of application of 500 g/m³.

(c) Trees and woodland areas to be retained shall be protected during the contract work by sturdy, impenetrable fencing, as specified in Clause 1.30 (d).

1.30 PROTECTION OF EXISTING TREES AND WOODLAND AREAS

(a) In respect of all existing trees and woodland the Contractor shall ensure, for the whole duration of the Contract, the following:-

- no unnecessary intrusion into areas of woodland or shrubland is made;

- The Architect shall approve all access routes to construction areas, which need to pass through woodland or scrub;

- The limits of site clearance are to be agreed by the Architect on site before site clearance commences. All trees to be cleared shall be marked by the Contractor and approved by the Architect before felling;

- No nails or other fixings shall be driven into trees;

- No fencing or signs shall be attached to trees;

- No materials or machinery shall be stored within the area of a tree's crown diameter.

- No workshop, canteens, or similar shall be installed beneath trees, nor shall equipment maintenance etc. be carried out under trees;

- No trees shall be used as anchors for ropes or chains used in guying, pulling and the like.

1.30 (b) The Contractor shall exercise the greatest care during the progress of the

Work to avoid damage to any tree, which the contract does not require to be cleared.

As soon as the site or any part thereof becomes available the Contractor shall erect Temporary Protective Fencing around each such tree or group of trees, preferably to protect the whole area within the spread of the tree's crown, but no closer than 2m from the trunk of any such tree. The Contractor shall inform the Architect if works are to be carried out within such fenced areas and, save with the express permission of the Architect or on his order, all such work shall be executed using only hand-held tools. The rates in the Contract shall include for this restriction.

(c) The Contractor shall maintain the Temporary Protective Fencing in good repair and subsequently remove it. Removal shall be subject to the permission of the Architect, which shall not normally be given earlier than the substantial completion of an adjacent part of the Works other than Landscape Softworks.

The Contractor may seek permission to remove the fencing temporarily if its removal is necessary for the satisfactory execution of the Works. The Contractor shall reinstate the temporary protective fencing as soon as possible.

(d) Temporary Protective Fencing shall be 1500-2000mm high, and shall ideally be constructed of strong, impenetrable material such as steel sheet or wooden board (See Fig. 1.1).

In certain circumstances where space for tree protection is a particular problem, protection of the tree trunk with planks may be acceptable (See Fig. 1.2). In these cases, the ground within the root zone should be protected from compaction with mats and gravel or boards/tracks for vehicles. (It should be noted that these treatments should only be used temporarily so that anaerobic soil conditions do not build up in the root zone).

(e) Unless adequate proof is submitted by the contractor to demonstrate that death or damage of existing vegetation was caused by circumstances beyond his control, replacement of dead or damaged plants of similar sizes of the same species will be required as instructed by the Architect. When instructed by the Architect, slow release fertilizer shall be applied to existing mature trees in a feeding band 1.5m either side of the branch spread as and when required. Holes shall be drilled at an angle at 450-600mm centers in the feeding bands, they shall be 300-600mm deep and approximately 37-50mm in diameter.

Slow release fertilizer shall be inserted in the holes, bulked up if necessary with sand or fine peat, at the rate of 1kg/25mm of trunk diameter at a height of 1.2 meters from ground level.

The fertilizer shall be applied between March and June or as directed by the Architect.

1.40 PRUNING OF EXISTING TREES

(a) Existing trees, which are to be retained, shall be pruned to remove dead or dangerous branches and to produce a balanced crown. All work shall be carried out in accordance with good horticultural practice and British Standard 3998 (1989) "Recommendations for the Tree Work," and shall be directed by the Architect. A fully qualified arboriculturalist should undertake tree pruning and surgery. Safety precautions shall be taken to protect those engaged in operations as well as people and property in the vicinity. Pruning and removal of branches shall be done using sharp, clean implements to give a single flat, sloping face (See Fig. 1.3). Ragged edges of bark or wood are to be trimmed with a sharp knife. Large branches shall be removed in stages beginning with removal of the main weight of the branch, with the final cut on a line outside the "branch bark ridge" and "branch collar". All cuts shall be made to avoid splintering or tearing of bark, which would catch water and encourage rot. Twigs less than 15mm diameter may be cut with sharp secateurs. Cleanly cut boughs on healthy trees will not normally require a bituminous sealant to close the wound. Instead an application of an approved fungicidal gel formula is recommended.

(b) Where cavities or rotten wood exist, all rotten or dead wood can be removed. However, cutting back to live wood is not recommended as this may cause new infection. Filling cavities is not recommended. Trees weakened by large cavities may require specialized arboricultural treatment such as bracing. The Architect will instruct on these situations following detailed arboricultural advice.

(d) Trees requiring pruning or thinning treatment will be categorized as follows:

(i) Hard prune

This shall include the removal of a substantial number of branches of up to 200mm in diameter. The objectives for hard pruning may include raising the crown in a street situation or preparing a tree for transplanting. The final shape of the reduced crown should be even and balanced and provide the basis for the growth of a well-shaped new crown.

(ii) Light prune

This shall include the removal of a few branches up to 75mm in diameter. The same objectives are required as with the hard prune.

(iii) Thin crown

This shall include the removal of overcrowded branches up to 50mm in diameter in the crown of the tree. The overall shape of the tree should be preserved, but all weak, decaying, damaged or crossing branches should be removed. A proportion of other branches can be removed to create a balanced and attractive crown (See Fig. 1.4).

(iv) Treat for pest and/or disease attack

This shall include the application of a suitable pesticide or fungicide, approved by the Architect, to the infected areas in accordance with the manufacturer's instructions.

(e) Where treatment of wounds is required, trim all damaged tissue and dead wood with a clean, sharp implement. Treat with an approved fungicidal gel (See Fig. 1.5).

2.00 TRANSPLANTING

2.10 TRANSPLANTING OF EXISTING TREES

All transplanting works should ideally be undertaken in early spring (March to April) to increase the chances of the trees' successful re-establishment. Transplanting operation should be timed so as to avoid strong sun or drying winds. The new position or storage facilities should be prepared before the tree is moved, so that the tree can be repositioned within two hours of lifting. The trunk and major boughs should be wrapped in damp hessian to protect from damage in transport and to reduce transpiration. Anti-transpiration spray can also be used on foliage. Crown thinning before transplanting is recommended. All stages of transplanting should be supervised or preferably undertaken by qualified arboriculturalists.

2.20 TREE SURGERY WORKS

Tree pruning and thinning should be carried out as instructed by the Architect during the preparation period before transplanting. All tree surgery work should be in accordance with British Standard 3998 (1989) "Recommendations For Tree Work". (See Section 1.0 of this specification). Minor pruning of additional limbs may be required after replanting.

2.30 SEQUENCE OF TRANSPLANTING OPERATIONS

Transplanting operations should be in accordance with British Standard 4043 (1989) "Transplanting Root-balled Trees". Preparation for moving should ideally begin several months before the transplanting operation is required (See Fig. 2.1).

(a) A root ball area, which incorporates at least half of the area of the tree crown, should be marked out and later a trench is dug around this area. Roots should be carefully pruned and treated with an approved fungicidal gel. Ideally this operation should be completed at least 6 months before moving so that the tree can establish new fibrous root within the rootzone. The root zone should be watered. A root feed with an approved slow release fertilizer is recommended (See Section 1.30 (3)).

(b) Crown thinning and shaping should be undertaken during this period.

(d) Precautions against desiccation can include hessian wrapping or anti-transpiration paints and these should be applied before transplanting operations begin.

(e) The rootball should be kept intact with all soil. At lifting, a spade or specialized lifting bucket can be slipped under the rootball and a strip of hessian or geotextile fabric pulled around the rootmass. The rootball and tree should be kept moist at all times.

(f) The whole tree should be lifted, using specialized equipment if necessary, and moved to its new position within 2 hours. The new planting position should be prepared as for any new tree, using fertilizer in the backfill material and soil conditioner as necessary. The tree should be orientated to best suit the new position and thoroughly watered in.

(g) The tree should be firmly secured using either well-anchored guy, with ratchet turnbuckles for adjustment, or a sturdy bamboo tripod arrangement (with poles of a minimum diameter of 75mm), as instructed by the Architect. Ties should be adjustable and should include wrapping to prevent chafing.

(h) Watering should be thorough and regular (at least twice a week) for the first months of establishment.

(i) Any damaged or additional branches should be pruned after planting.

(j) The contractor should keep an accurate photographic record (dated), of all stages of the transplanting operation for submission to the Architect.

2.40 MAINTENANCE WORKS

(a) Keeping Transplanted Trees in Temporary Position

When transplanted plants cannot be immediately re-planted in the intended final position, a secure, sheltered and otherwise the Contractor for approval by the Architect should designate suitable storage nursery. Keeping transplanted trees in the temp position within this period will be the same as for the Establishment Works, (see below), but will not constitute part of the Establishment Period. The length of temporary off-site keeping the transplanted trees shall be proposed by the contractor for Architects approval but shall in no case be less than 12 months.

(b) Establishment Works

Establishment Works are those works to establish the transplanted tree and to be carried out during the Establishment Period.

The Establishment Period shall commence upon completion of the re-planting of the trees to the nursery as designated by the property owner or to the location as directed by the Architect and shall extend through one growing season after the re-planting work in the Defects Liability Period of the Site Formation & Foundation Contract but in no case be earlier that the end of the Defects Liability Period.

(d) Dead Plants

The contractor will replace, at own expense, any plant, which in the opinion of the Architect dies, is seen to be dying, or fails to thrive, during this period as a result of bad workmanship, poor quality maintenance or neglect.

(e) Replacement Planting

Replace dead or ailing plants as Clause 2.40(d) within two (2) weeks of being identified, the largest available good quality nursery stock, but at least Extra Heavy Standard size, of similar species unless otherwise instructed by the Architect.

(f) Extra Heavy Standard Trees

Extra Heavy Standard Trees to have all the following characteristics:

i) a sturdy, straight stem, not less than 2000mm in height from soil level to the lowest branch,

ii) a stem diameter, greater than 150mm when measured at a point one metre above the root collar.

iii) a well balanced branching head, or a well defined straight and upright leader with branches growing out from the stem with good symmetry, and a minimum length of 1500mm,

iv) a total height above soil level greater than 6000mm,

v) "grown on" in Hong Kong,

vi) a root ball not less 1200mm in diameter and 600mm in depth,

vii) a root system previously under cut a minimum of one year prior to lifting, to encourage compact fibrous growth.

(g) Damaged Plants due to Vandalism

The contractor is not responsible for replacing dead or damaged stock resulting from proven vandalism. The onus is at all times on the Contractor to prove that death or damage was so caused by circumstances beyond his control and in any event, no claim shall be considered unless submitted in writing to the Architect within three working days of the event happening.

(h) Damaged Plants due to Typhoons

Within 48 hours of Typhoon signal No. 8 or above being lowered, replant all plants blown over, firm up all other plants, provide the Architect with a photographic record of the Site, and prepare a detailed report of all plants which have suffered structural damage. As soon as practical thereafter remove dead plants and clear the Site of all debris providing the replanting works are carried out each day. "The Employer" will accept responsibility for dead or dying plants recorded one month after the typhoon, excepting those plants recorded as being dead or dying prior to the typhoon. Thereafter responsibility reverts to the contractor. Should the planting not be carried out within the time period, or the works not carried out satisfactorily, than the Contractor shall be held responsible for all plant re-placements.

(i) Records

Ensure that the Approved Foreman reports to the Architect's office before and after carrying out the day's maintenance work and make a countersigned record of the work carried out available for inspection at that office. These reports shall contain operations undertaken or specific tree locations and materials used. Provide monthly photo record showing the condition of the plants.

(j) Water

The Contractor is required to provide non-toxic water throughout the establishment period.

(k) Weeding

Keep all planted areas weed-free. Undertake a weeding operation at least once a month. Replace any aggregate or soil disturbed or removed during this process.

(l) Weed Disposal

Collect all weeds and rubbish during these operations and remove from the Site to a properly designated tip.

(m) Firming Up

Undertake firming-up of plants from time to time during the period and particularly after heavy rain and/or wind.

(n) Tree Ties

Tighten, or slacken tree ties as necessary for the healthy growth of the tree, and adjust or replace the protective pad as necessary to prevent chafing of the bark.

(o) Pruning

Carry out pruning when instructed during the Establishment Period, to encourage bushy growth good form. Remove dead, damaged or crossing branches.

(p) Pests and Fungal Growth

Regularly check for any insect attack or fungus infestation particularly during known periods of activity. Report to the Architect any such occurrence and carry out remedial measures by use of sprayed effective approved insecticide or fungicide in strict accordance with the manufacturer's instruction. Take due care and have regard to the safety and convenience of the general public and carefully control the spraying to avoid unnecessary dispersion.

(q) Final Handover

Carry out an inspection and formal check of the Works at the end of the Establishment Period, with the Architect. Carry out the final visit for all regular operations included in the specification, immediately prior to the final handover of the transplanted trees. Satisfactory completion of any outstanding defective and replacement work is also one of the Architects consideration in issuing the Make Good Defects Certificate for the Site Formation and Foundation Contract.