SelecTree: Trees and Utilities

Overhead Utility Services

Extreme care and understanding of the hazards associated with power lines should be acknowledged before any tree planting or tree maintenance is performed.

levels of serviceNational electric standard requires that poles supporting electrical conductors carry the highest voltage at the highest point of attachment. Simply stated, voltage decreases as points of attachment move down the pole. Any conductor (wire) carrying more than 750 volts are considered "high voltage" a high voltage placard (as seen in yellow in the diagram) should be visible. Only qualified line clearance tree workers should work on trees within 10ft. of high voltage power lines.

"Secondary" conductors carry electricity pole to pole. Working on trees near secondary wires should only be done by competent tree workers who are familiar with tree care tools and the potential hazards surrounding these electrical facilities.



customer equipment"Service Wires" carry electricity from a pole to a home. The point of attachment to a home is called the "periscope". The periscope delivers power to a customer's meter. Tree limbs should be maintained away from service wires and doing so is the responsibility of the property owner, not the utility company. Service wires can be re-routed through a tree should strain or abrasion to the wire become evident. Utility companies can perform this work with advanced notice, but an interruption in power will result. Maintenance on service wire should always be preventative. Tree planting near any power line should be avoided, if pruning becomes necessary, try to do so before a hazard is created.

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State Clearance Regulations

Trees and other vegetation growing in proximity to overhead utility facilities must adhere to federal and state regulations. These laws address potential vegetation conflicts with public safety, service reliability, and fire prevention. In California, three state regulations apply to vegetation and power line/utility clearances.

General Order 95., Rule 35

The first regulation is General Order 95., Rule 35. This rule requires a minimum of 18" (inches) of clearance between vegetation and energized conductors (wires) carrying more than 750 volts. This law covers all of California regardless of location and defines the minimum clearance required at all times. Utility vegetation management programs must often achieve greater clearance than 18" to address regrowth of affected vegetation and all potential weather/climatic conditions which can affect the vegetation and the conductors. Length of time between maintenance cycles can also increase the amount of clearance required.
Visit CPUC website for complete regulations. (search for General Order 95 Rule 35)

Public Resource Code 4293

The second regulation is Public Resource Code 4293. This code requires a minimum of 4' (feet) of clearance between vegetation and energized conductors (wires) carrying more than 750 volts. This law covers all "State Responsibility Areas" in California. State responsibility lands are generally outside city limits where the California Department of Forestry and Fire Protection (CDF) is the Direct Protection Agency. Utility vegetation management programs must often achieve greater clearance than 4' (feet) to address regrowth of affected vegetation, higher voltage transmission lines, and all potential weather/climatic conditions which can effect the vegetation and the conductors. Length of time between maintenance cycles can also increase the amount of clearance required.

Public Resource Code 4292

The third regulation is Public Resource Code 4292. This code requires a minimum of 10' (feet) radial clearance at the base of poles carrying certain protective equipment and connectors of ground vegetation clearance and the limbing of tree branches to 8' (feet) in height around these poles. This law also covers all "State Responsibility Areas" in California. State responsibility lands are generally outside city limits where the California Department of Forestry and Fire Protection (CDF) is the Direct Protection Agency. Utility vegetation management pole clearing programs must also address regrowth of affected vegetation, and all potential weather/climatic conditions which can effect the vegetation. Length of time between maintenance cycles can also change the amount of clearance required.

Title 14, California Code of Regulations (further defines the Public Resource code)

Section 1254
Minimum Clearance Provisions PRC 4292

Section 1256
Minimum Clearance Provisions - PRC 4293

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Quercus ilex

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