Underground Utilities Near Trees

  • Plot locations and trees and their Critical Root Zones (CRZ) for all trees near the work to be performed; include any additional detail for protecting and preserving trunks and roots.
  • Plans must indicate whether the line is to be installed by direct boring or trenching.
  • Design standards: CRZ determination | Root protection in utility trench | Protection for underground utility installation
  • 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, hand holes and manholes
    • 25 feet of test pits
    • Show and install tree protection measures where there may be an impact to a tree, or the critical root zone of a tree.
    • Show the staging area on the plan, including where excavated soil will be placed. Keep these areas away from trees and their critical root zones
  • Boring depths: When a line is installed by boring near the roots of a tree, it must be deep enough to avoid serious damage to the roots and 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 are guidelines:
    • When a line is 10 feet or less from the trunk of a tree 6 inches (or less) in diameter at breast height (diameter at 4 1/2 feet above the ground, herein abbreviated as “DBH”), the bore must be a minimum of 6 feet deep.
    • When a line is 15 feet or less from the trunk of a tree greater than 6 inches DBH, the bore must be a minimum of 10 feet deep.
  • Trench, bore pit, hand hole 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 roots. The following are guidelines:
    • For trees 6 inches DBH and less, the trench, bore pit, hand hole or manhole must be a minimum of 10 feet away from the trunk of the tree.
    • For trees greater than 6 inches DBH, the trench, bore pit, hand hole or manhole must be a minimum of 20 feet away from the trunk of the tree.
    • Trees 42 inches DBH and greater, or otherwise significant, may require more than 20 feet of clearance.
  • Test pits: Test pits must be located a minimum of 20 feet from all trees.
  • When a line is installed in an area of public space trees, by permit provision, the installer is responsible for tree stewardship. If any tree is severely damaged or dies as a result of construction, the installer may be responsible for tree replacement. Whether a tree must be replaced, as well as the number, size and species of the replacement, will be determined by the County. See the tree replacement guidelines for details.
  • There may be situations in which the applicant would prefer to remove a tree rather than relocate the line. The County will consider such requests on a case-by-case basis. If the County determines that tree removal is possible, it will inform the applicant of the tree replacement requirements. Final approval will be dependent on the applicant’s agreement to these requirements.
  • Plans must indicate the name and contact information for the responsible party or parties.

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