by Beau Miller, Dow AgroSciences
Managing a 70,000-square-mile utility system is difficult?especially when every mile of line must be inspected annually. The only way to comply with federal and state mandates, address environmental concerns and keep power flowing to customers is to rely on skilled contractors who understand herbicide applications.
 Substation areas are required to be maintained as bare ground, but surrounding ornamental vegetation must be taken into account. |
Pacific Gas and Electric Company (PG&E)'s northern and central California area consists of 18,610 circuit miles of interconnected transmission lines that deliver power to more than 5 million customers. Pam Money is the transmission right-of-way program manager responsible for transmission tree-clearing projects and their follow-up enhancements.
Reliable, safe power
The PG&E vegetation management department has taken a long-term approach to help make the system manageable for years to come. Money's contractors play a big role, she said.
"Our main driving factors are reliability of the line and clearance compliance," Money said. "Especially in the summer, we cannot afford an outage because of how tight the electric supply is during the hot weather. And the contractors we work with are always focused on both safety and reliability."
One of those contractors is Bob Brenton, a certified pest control adviser (PCA) in California. He helps manage PG&E substations, transmission and distribution lines and hydroelectric facilities. Wildfires present a concern during the dry, summer months, as evident during the October 2007 wildfires that burned southern California.
"Fire prevention is a huge concern for us since we may have a summer without rain and we average less than 15 inches of rain annually," Brenton said. "The rights-of-way can serve as a firebreak, which can help slow down an existing wildfire or serve as a line from which to backfire."
Environmental stewards
As a partner in the U.S. Environmental Protection Agency (EPA) Pesticide Environmental Stewardship Program, PG&E is committed to reducing potential health and environmental risks associated with herbicide use. Money and her team have set up best-management practices for the entire system.
"Being in California, we have exceedingly high standards when it comes to water-quality and other environmental issues," Money said. "We are always looking for new ways to be better stewards to the environment."
Because the service area is so large and includes many microclimates and plant species, a one-size-fits-all herbicide treatment cannot treat problem vegetation. The model for which vegetation is maintained, however, is the same throughout the system.
Introduced by Drs. William Bramble and William Byrnes, the wire-border zone method is used wherever possible. Their philosophy consists of managing low-growing shrub and grass communities directly under the transmission wires plus 10 feet on both sides in the wire zone. The border zone is the portion of the right-of-way that extends from 10 feet outside of the wire to the edge of the right-of-way and is managed for taller shrubs and brush.
"We use this method because of the research that Bramble and Byrnes have done," Money said. "In some cases, we can't use it because of a property owner's refusal to treat. All of our contractors are PCAs and are great at addressing property-owner concerns. But where we are able to use it, we've seen an increase in biodiversity, especially in areas that had previously been impenetrable."
Sensitive-site preemergence
Many of the PG&E substations run through suburban areas with gardens and ornamental plants surrounding them. In these instances, it can be difficult to apply typical bareground treatments for fear of off-target damage.
After conducting trials, Brenton concluded that Milestone VM, Garlon 3A, Dimension, GoalTender and Telar herbicides fit these sensitive-site situations.
"Although there is no single prescription for bareground, we generally use a Dimension and Telar herbicide mix as a preemergence application in areas where the surroundings are more sensitive," Brenton said. "If we need to follow up on vegetation that broke through, a postemergence application of Garlon 3A mixed with glyphosate will be applied. If the follow-up requires selective broadleaf weed control, we will apply Garlon 3A with Milestone VM. We also will use GoalTender as a sequential treatment with Milestone VM where we have trouble with marestail (horseweed)."
 Bob Brenton, a pest control adviser for PG&E, deals with many line compliance challenges. |
Another tool PG&E is considering is to encourage plant species that can outcompete species that are incompatible with electric transmission lines. One example is squaw carpet (Ceanothus prostratus), a California native common to the northern Sierras at 3,000 feet to 7,000 feet elevation. Bermuda grass is another example. Money sees the advantage to encouraging it along some of her rights-of-way despite it's not being a native species to California. A big reason for its success is the use of Milestone VM.
"Bermuda grass is something that helps keep undesirable vegetation from encroaching, doing some of the work for us," Money said. "The selective properties of Milestone VM allow this competitive grass to establish and make our job easier."
While dealing with public concerns, environmental issues, climate changes, compliance standards and a large service area, the vegetation management program at PG&E constantly evolves. Thanks to Money and her strong group of PCA contractors, PG&E customers get reliable power while the vegetation management program benefits the surrounding environment.
Author
Beau Miller is a vegetation management specialist with Dow AgroSciences in Sacramento, Calif. He has more than 15 years of IVM experience. Reach him at bjmiller@dow.com.