Environmental Services
Guidelines For Installing Underground Utilities Near Trees
Revised: May 7, 2003
- Plans must indicate whether the line is to be installed by direct boring or by trenching.
- Plans must show all trees within:
- 20 feet of lines to be bored
- 25 feet of lines to be trenched
- 25 feet of bore pits, handholes and manholes
- 25 feet of test pits
- Boring Depths - When a line is to be installed by boring near the roots of a tree, it must be deep enough to avoid serious damage to the roots, and must not interfere with any underground drainage system installed for the trees. The farther the line is from the tree (horizontally), the less line depth matters. The following will be used as guidelines:
- Trees 6" dbh (diameter at 4 1/2 feet above the ground) and less - When a line is 10 feet or less from the trunk of the tree, the bore shall be a minimum of 6 feet deep.
- Trees greater than 6" dbh - When a line is 15 feet or less from the trunk of the tree, the bore shall be a minimum of 10 feet deep.
- Trench, Bore Pit, Handhole, and Manhole Distances - When a line is to be installed by trenching (and the similar excavations listed), it must be far enough away from trees to avoid serious damage to the roots. The following will be used as guidelines:
- Trees 6" dbh and less - Trench, Bore Pit, Handhole, or Manhole shall be a minimum of 10 feet away from the trunk of the tree.
- Trees greater than 6" dbh - Trench, Bore Pit, Handhole, or Manhole shall be a minimum of 20 feet away from the trunk of the tree.
- Trees 42" dbh and greater, or otherwise significant - Arlington County may require more than 20 feet of clearance.
- Test Pits - Test pits must be located a minimum of 20 feet from all trees.
- If a line is to be installed in the area of public space trees, the following condition will be made part of the permit. The intent of this condition is to protect Arlington County in the event of inadvertent damage to its trees:
- If any public space tree is severely damaged or dies as a result of this construction, it shall be replaced by the Applicant in accordance with the Arlington County Tree Replacement Guidelines. Whether or not a tree must be replaced, as well as the number, size, and species of the replacements, shall be determined by Arlington County.
- There may be situations where the Applicant would prefer to remove a tree rather than relocate the line. Arlington County will consider such requests on a case by case basis. In the event that Arlington County determines that tree removal is possible, the County will inform the Applicant as to what the tree replacement requirements will be. Final approval by Arlington County will be dependent on the Applicant agreeing to the tree replacement requirements.
If there are any questions concerning these guidelines, contact:
Vincent Verweij Urban Forester (703) 228-1863
