| Impact to Tree |
Construction Activity |
Methods/Treatments To Minimize Damage |
| Branch and trunk damage |
Injury from equipment |
Fence trees to enclose low branches and protect trunk. Report all damage promptly so arborist can treat appropriately. |
| Pruning for vertical clearance for building traffic, and construction |
Prune to minimum height required prior to construction. Consider minimum height requirements of construction equipment and emergency vehicles over roads. All pruning should be performed by an arborist, not by construction personnel. |
| Felling trees in construction area |
Require that trees being removed be felled away from, rather than into, tree protection zones. |
| Root Damage or loss |
Stripping site of organic surface soil |
Restrict stripping of topsoil around trees. Any woody vegetation to be removed adjacent to trees to remain should be cut a ground level by hand and not pulled out by equipment, or root injury to remaining trees will result. |
| Digging into topsoil layer and killing roots while loading piles of soil, sand, gravel, etc. |
Store outside fenced protection zones and away from root zones. Place plastic tarp, straw, plywood or geotextile material beneath pile. |
| Lowering grade, scarifying, preparing subgrade for fills, structures |
Use retaining walls with discontinuous footing to maintain natural grade as far as possible from the trees. Excavate to finish grade by hand and cut exposed roots with a saw to avoid root wrenching and shattering by equipment. Soil beyond cut face can be removed by equipment sitting outside the dripline of the tree. |
| Subgrade preparation for pavement |
Use paving materials requiring a minimum amount of excavation (e.g. reinforced concrete instead of asphalt). Design traffic patterns to avoid heavy loads adjacent to trees (heavy lead-bearing pavement require thicker base material and subgrade compaction). Specify minimum subgrade compaction under pavement within root zone. Install aeration pipes if necessary. |
| Excavation for footings, walls, foundations |
Design walls/structures with discontinuous footings and pier foundations. Excavate by hand near major roots. Avoid slab foundations, use post-and-beam footings. |
| Trenching for utilities, drainage |
Coordinate utility trench locations with installation contractors. Consolidate utility trenches and try to have them placed next to driveways and walks. Excavate trenches by hand in areas with roots larger that one inch diameter. Tunnel under woody roots rather than cutting them. Curve trenches rather than using straight lines. |
| Fill dirt over roots |
Avoid adding soil over root zone. If unavoidable, insert aeration pipes per directions in Arboriculture by Richard Harris. |
| Unfavorable conditions for root growth; chronic stress from reduced |
Compacted Soils |
Fence trees to keep traffic an storage out of root area. In areas of engineered fills, specify minimum compaction (usually 85%) if fill will not support a structure. Provide a storage yard and traffic areas for construction activity well away from trees. Protect soil surface from traffic compaction with 12" to 14" of wood chip mulch. Following construction, vertical mulch compacted areas. Install aeration vents. |
| root systems |
Spills, waste disposal |
Post notices on fences prohibiting dumping and disposal of waste around trees. Require immediate cleanup of accidental spills. |
| (e.g. paint, oil, fuel) |
| Concrete wash-out and waste dumping |
Designate wash-out area. Dig pit an remove after construction, if necessary. |
| Soil sterilants (herbicides) applied under pavement |
Use herbicides safe for use around existing vegetation and follow directions on the label. |
| Impervious surface over soil surface |
Utilize pervious paving materials (e.g. interlocking blocks set on sand). Install aeration vents in impervious paving. |
| Inadequate soil moisture |
Rechannelization of stream flow; redirecting runoff; lowering water table; lower grade |
In some cases it may be possible to design systems to allow low flows through normal stream alignments and provide bypass into storm drains for peak flow conditions. Provide supplemental irrigation in similar volumes and seasonal distribution as would normally occur. |
| Excess soil moisture |
Underground flow backup; raising water table |
Fills placed across drainage courses must have culverts placed at the bottom of the low flow so that water is not backed up before rising to the elevation of the culvert. Study the geotechincal report for ground water characteristics to see that walls and fills will not intercept underground flow. |
| Lack of surface drainage away from tree |
Where surface grades are to be modified, make sure that water will flow away from the trunk, i.e. that the trunk is not at the lowest point. If the tree is placed in a well, drainage must be provided from the bottom of the well. |
| Irrigation of exotic landscapes |
Some species cannot tolerate frequent irrigation required to maintain lawns, flowers, and other shallow-rooted plants. Use free form mulch areas or avoid landscaping under those trees, or utilize plants that do not require irrigation. |
| Increased exposure |
Thinning stands, removal of undergrowth |
Save groups or clusters of trees when working with species that perform poorly in the open or as single trees. Maintain the natural undergrowth. |
| Excessive pruning |
Prune sparingly, especially in stands of shade-tolerant species. Remember, leaves manufacture the food needed for root growth and recovery from shock. |
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| All information obtained from The National Arbor Day Foundation |
