OAR 860-024-0016: Minimum Vegetation Clearance Requirements

(1) For purposes of this rule: (a) "Cycle Buster" means vegetation that will not make it through the routine trim cycle without encroaching on the required minimum clearances and, therefore require pruning midterm before the routine cycle is completed. (b) “Readily climbable” means vegetation having both of the following characteristics: (A) Low limbs, accessible from the ground and sufficiently close together so that the vegetation can be climbed by a child or average person without using a ladder or other special equipment; and (B) A main stem or major branch that would support a child or average person either within arms’ reach of an uninsulated energized electric line or within such proximity to the electric line that the climber could be injured by direct or indirect contact with the line. (c) “Vegetation” means trees, shrubs, and any other woody plants. (d) “Volts” means nominal voltage levels, measured phase-to-phase. (2) The requirements in this rule provide the minimum standards for conductor clearances from vegetation to provide safety for the public and utility workers, reasonable service continuity, and fire prevention. Each Operator of electric supply facilities must have a vegetation management program and keep appropriate records to ensure that timely trimming is accomplished to keep the designated minimum clearances in section (4) below. These records must be made available to the Commission upon request. If clearances are not being maintained, the Commission may require the Operator to implement an alternative vegetation management program and/or specific trim cycles. (3) Each Operator of electric supply facilities must trim or remove readily climbable vegetation as specified in section (4) of this rule to minimize the likelihood of direct or indirect access to a high voltage conductor by a member of the public or any unauthorized person.. (4) Under reasonably anticipated operational conditions, an Operator of electric supply facilities must maintain the following minimum clearances of vegetation from conductors: (a) Ten feet for conductors energized above 200,000 volts. (b) Seven and one-half feet for conductors energized at 50,001 through 200,000 volts. (c) Five feet for conductors energized at 600 through 50,000 volts. (A) Clearances may be reduced to three feet if the vegetation is not readily climbable. (B) Intrusion of limited small branches and new tree growth into this minimum clearance area is acceptable provided the vegetation does not come closer than six inches to the conductor. (5) For conductors energized below 600 volts, an Operator of electric supply facilities must trim vegetation to prevent it from causing strain or abrasion on electric conductors. Where trimming or removal of vegetation is not practical, the Operator of electric supply facilities must install suitable material or devices to avoid insulation damage by abrasion. (6) In determining the extent of trimming or vegetation removal required to maintain the clearances required in section (4) of this rule, the Operator of electric supply facilities must consider at minimum the following factors for each conductor: (a) Voltage; (b) Location; (c) Configuration; (d) Sag of conductors at elevated temperatures and under wind and ice loading; and (e) Growth habit, strength, and health of vegetation (including rates of tree mortality) growing adjacent to the conductor, with the combined displacement of the vegetation, supporting structures, and conductors under adverse weather or routine wind conditions; and (f) The amount of trimming or vegetation removal required to minimize Cycle Buster vegetation interference of energized conductors. (7) Each Operator of communications facilities must ensure vegetation around communications lines do not pose a foreseeable danger to the pole or electric supply Operator's facilities.