Read the full story about Maimed Trees Reveal Flaws in Contract Oversight
By CWA Architect (LPD-1)
1. “Protected Zone” for existing trees: before beginning any demotion or construction operations, the contractor shall install temporary fencing around all existing trees within the construction zone that are to be saved.
The fence shall be installed no closer to the tree than the edge of the tree’s protected zone, generally defined as the area beginning five feet outside of the trees dripline and extending towards the tree (or as far away from the trunk as practicable). The fencing shall be of a material and height acceptable to the landscape architect.
All contractors and their crews shall not be allowed inside this “protected zone” nor shall they be allowed to store or dump foreign materials within this area.
No work of any kind, including trenching, shall be allowed within the protected zone except as described below. The fencing shall remain around each tree to be saved until the completion of construction operations.
2. Temporary Mulch: To alleviate soil compaction in anticipated areas of high construction traffic, and only where fencing cannot be set five feet outside of the dripline, the contractor shall install a layer of mulch, 9”- 12” thick, over all exposed earth from the tree trunk to 5’ outside of the dripline. This layer shall be maintained at all times during construction. When planting operations are completed, the mulch shall be redistributed throughout all planting areas in a 3” thick “permanent” mulch layer.
3. Necessary Work: When it becomes necessary to enter the “protected zone,” such as for fine grading, irrigation installation and planting operations, the contractor shall strictly adhere to the following rules:
A. Every effort shall be made to preserve the existing grade around protected trees in as wide an area as possible.
B. Trenching within the protected zone of existing trees shall be performed by hand, and with extreme care not to sever roots 1-1/2” in diameter and larger. Where roots 1-1/2” in diameter and larger are encountered, the contractor shall tunnel under said roots. Exposed roots that have been tunneled under shall be wrapped in wet burlap and kept moist while the trench is open.
C. Where roots 1-1/2” in diameter or larger must be cut due to extensive grade changes, those roots must be exposed by hand digging and cut cleanly. Ragged cuts generally do not heal properly and may leave the tree open to pests and pathogens.
D. Where trenching near trees has already occurred from previous construction operations, the contractor shall make every effort to confine his trenching operations to the previously-created trenches, while adhering to the conditions set forth in 3-B.
4. Potential Conflicts: the contractor shall notify the owner and arborist should any potential conflicts arise between these specifications and/or large roots encountered in the field and construction operations. The contractor shall not take any action in such conflicts without the arborist’s written approval. The arborist shall have final authority over all methods necessary to help ensure the protection and survival of existing trees.
[Items 5 and 6 dealt with pruning and landscape irrigation.]
This is part of the August 27, 2010 online edition of The Mountain Enterprise.
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