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Director Blog: Utility Wildfire Risk Mitigation Through Fuel Management Policies; Importance of Vegetation Management for Utility Wildfire Hazard Mitigation

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Below is a blog from Elizaveta Malashenko, the Director of the CPUC's Safety and Enforcement Division.

In a previous blog I introduced an approach of considering policy actions in three broad categories following the fire triangle model - fuel management, ignition control, and weather preparedness policies. This blog will dive into fuel management policies, specifically focusing on utility vegetation management and planting practices.

The leading cause of fires ignited by utility infrastructure is a contact between electric equipment and an object, without equipment failure as a contributing factor. More than 50 percent of those incidents are due to vegetation (as opposed to vehicles, animals, balloons, etc.).  As such, vegetation management is critical for fire hazard mitigation. Vegetation management is also critical for reliability, as contact between utility facilities and vegetation is the leading cause of outages nationally. An attempt by people to trim trees in proximity to electric lines is also one of the leading causes of injuries and fatalities related to the electric system. While it varies between utilities, it is generally accepted that utility vegetation management expenses are one of the largest expense items associated with maintaining overhead transmission and distribution electrical systems. California investor-owned utilities spend more than $250 million a year on vegetation management on distribution lines alone. If vegetation management activities were calculated for all utilities in the state (including electric transmission, gas transmission and distribution, municipal utilities, and telecommunication companies) the total vegetation management costs for the state likely exceed $1 billion a year.

The traditional approach to vegetation management is establishing and maintaining a required clearance level. The North American Electric Reliability Corporation (NERC) sets vegetation management requirements for transmission. California and Oregon are the only states that have clearance requirements for the electric distribution system. Most other states that have any safety regulations for electric distribution facilities adopt the National Electric Safety Code (NESC) by reference, which has vegetation clearance guidelines for utilities, but not hard requirements.

However, vegetation clearance requirements by themselves are not sufficient to prevent wildfires or to otherwise ensure that vegetation does not cause safety and reliability incidents. Clearance requirements by themselves are insufficient for two main reasons:

  • Clearance requirements do not address the issue that vegetation outside of clearance levels can come into contact with electric facilities under specific circumstances, such as storm or a dead tree falling down. As a simple concept, if there is a 100 foot tree growing 75 feet away from an electric line it can potentially fall and contact an electric line and cause a fire.
  • Wind causes trees to fail unexpectedly. Arborists are not able to predict which trees will fail under wind conditions exceeding 55 miles per hour, but even tree failure with winds of 25 miles per hour are hard to predict. With winds of more than 25 miles per hour, healthy tree branches can break off and trees can split. Winds exceeding 55 miles may uproot healthy trees. It is therefore not possible to predict with any reliable accuracy which trees will fail in storm conditions.

Consequently, any tree that is tall enough to contact an electric facility if it falls theoretically constitutes a fire hazard. This is something that's recognized by Federal Energy Regulatory Commission (FERC) and NERC. (This is from a study completed by FERC and NERC after snowstorms in the Northeast in 2011. It concluded that a "great number of healthy trees, most outside of utility rights-of-way, being uprooted and falling onto distribution and transmission lines" were the cause of the widespread outages. This lead to NERC issuing an alert to utilities to address risks posed by trees outside of the utility right of way.)

Therefore, the only reliable way to reduce fire hazards and other risks associated with contact between vegetation and electric lines is to reduce the population of trees that can grow or fall into utility lines. While this may seem infeasible at first, there is significant opportunity for movement in that direction, especially in urban areas and anywhere where vegetation is planted.


Planting Management Presents an Opportunity to Improve Fire Safety

Under the current vegetation management paradigm, there are very few incentives that promote planting of vegetation that's compatible with electric facilities. The land/property owners do not directly bear the cost of ongoing vegetation management of vegetation planted in proximity to electric lines. Often, landscaping decisions are made with no consideration for the electric infrastructure. Utilities have no control over vegetation planted outside of their right of way and generally become aware of vegetation once it's already in existence. Utility vegetation management is typically performed by third-party contractors hired by utilities. Vegetation management contractors benefit from needing to perform inspection and frequent pruning, while for utilities this cost is typically an Operations and Maintenance (O&M) cost passed through to consumers. In this traditional approach to vegetation management, there is no effort dedicated to ensuring that vegetation that may grow or fall into power lines is not planted in the first place. As population density increases, the costs only grow.

The lack of incentives to plant the right vegetation in the right place has a major impact. For example, in a study done in Phoenix, more than 70 percent of trees surveyed were found to be planted such that they would need to be removed. As an illustration of this problem in California, Pacific Gas and Electric Company (PG&E) reported an incident in which a developer planted 300 redwood trees directly under power lines and declined to move them when it was pointed out that the trees would need to be pruned or removed. These situations happen due to an absence of rules guiding planting decisions on private property, even though they are estimated to comprise nearly half of vegetation in urban environments. Local ordinances, where they exist, typically only apply to trees in public space and rarely address interaction of vegetation with power lines.

In order to systematically reduce the risk of wildfires, we need to focus on reducing the availability of fuel in proximity to potential sources of ignition. While the prospect of reducing hazardous vegetation may seem daunting at first, there is a path towards systematic improvements. The lifespan of naturally occurring trees in California typically exceeds 100 years, with many tree species having a life expectancy exceeding 300 or 400 years. However, planted trees, especially in urban environments, have an average lifespan of 19 to 28 years, with a half-life of 13 to 20 years (i.e., only 50 percent of trees make it to 13-20 years).  There are several causes for this, but frequent pruning is one of the drivers of the short life-span for urban trees. This relatively short lifespan of planted trees presents a realistic opportunity to reduce the population of trees that are not compatible with electric infrastructure over time, while also introducing other environmental benefits (one simple environmental benefit is that if trees are planted that don't require frequent pruning due to their proximity to electric lines they will have longer lifespans and therefore more environmental benefits). Policies for managing tree species in areas that were impacted by wildfires can also over time result in improvement in compatibility of vegetation and electric lines.

Obviously, complete elimination of all vegetation that may come into contact with electric facilities is not feasible, especially for a state the size of California. However, it should be possible to at least stop compounding existing challenges by making sure that vegetation that's under our control is planned to be compatible with utility infrastructure.

The good news is that there are solutions and existing programs to build upon. In future blogs, I will explore possible actions that can be taken to promote planting practices that are fire-resilient, beneficial to the environment, and cost effective.

Elizaveta Malashenko was named Director of the CPUC's Safety and Enforcement Division in February 2015. 

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