Trees on the Edge - Assessing Impacts of Highway Construction
Maryland Forest Service developed a methodology for assesing and managing impacts to trees from highway construction. This process was pubished in the National Arborist Association's Magazine, Tree Care Industry (Vol.X No.11, Nov 1999) The following is a synopsis of this article.
Engineering drawings are generated, either by MD State Highway Administration (MD SHA) or a contractor, for the proposed highway construction. The engineering plans are then provided to an environmental consultant. The consultant goes to the site, identifies forest stands, wetlands, streams, and other sensitive areas that will be impacted by the proposed construction, and calls out any specimen trees within or adjacent to the limits of disturbance. After these items are mapped, they are submitted to MD DNR-FS for review and comment.
MD DNR-FS and MD SHA then go through an interactive process of modifying the plans, where possible within engineering constraints, to minimize forest clearing and specimen tree Critical Root Zone Impacts. An ISA Certified Arborist that is a MD Licensed Tree Expert is required by the contract documents, where appropriate, to evaluate trees which are pre-selected by MD DNR-FS. If it is determined by the Certified Arborist that an edge tree will not, either mechanically or biologically, tolerate the construction impact, it is removed. If the Arborist deems the tree viable, a series of specifications are invoked, including crown cleaning, crown reduction adjacent to the impact, fertilization and mycorrhizal inoculation.
Example: Tree Retention / Removal Evaluation
In the foreground is the stump of the 25" D.B.H. White Oak, which could not be retained. To the rear is the retained 28" Southern Red Oak, misidentified as Red Oak on the plan. The Limit of Disturbance (L.O.D.) for the clearing will be approximately where the white post is located in the photo.
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