Beau Miller and Travis Rogers, Dow AgroSciences
For U.S. utility companies, employing a carefully constructed vegetation management program keeps transmission lines and service areas free from potentially damaging natural obstructions such as falling trees and wildfires. But they must also account for issues such as compliance standards, public pressure and environmental concerns.
At Pacific Gas and Electric Co. (PG&E) in North Carolina and Progress Energy in California, vegetation management programs have been developed to help accomplish these objectives. From partnering with the right contractors to using the appropriate herbicide treatments, these utilities have vegetation management programs to ensure the power flows to customers.
PG&E Fights, VM Battles
Managing a utility system in a 70,000-square-mile service area is difficult, especially when every mile of line must be inspected every year. For PG&E’s Pam Money, relying on her skilled team of contractors is crucial to complying with federal and state mandates, addressing environmental concerns and keeping the power flowing to customers.
Money, the transmission right-of-way program manager, is responsible for the transmission tree-clearing projects and follow-up enhancements to those areas, usually accomplished using herbicide applications.
PG&E’s service area in northern and central California consists of 18,610 circuit miles of interconnected transmission lines that deliver power to more than 5 million customers.
The vegetation management department has taken a long-term approach to help make the system manageable for years. Money’s contractors play a big role.
“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 in California. Brenton helps manage PG&E area including substations, transmission and distribution lines and hydroelectric facilities. A big concern during the dry summer months is wildfire potential, as evident in the October 2007 wildfires that swept through 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.”
As partners in the U.S. Environmental Protection Agency Pesticide Environmental Stewardship Program, PG&E is committed to reducing the potential health and environmental risks associated with herbicide use. Money and her team have set up best management practices for the entire system.
|Pam Money, PG&E|
“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, involving many microclimates and plant species, a one-size-fits-all herbicide treatment cannot treat problem vegetation. The model for which the vegetation is maintained, however, is the same for the entire system.
Introduced by Drs. William Bramble and William Byrnes, the wire zone-border zone method is used where possible. This philosophy consists of managing for 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, Money said.
“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 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.”
Many PG&E substations run through suburban areas with gardens and ornamental plants. In these instances, it can be difficult to apply a typical bare ground treatment for fear of off-target damage.
After conducting some trials, Brenton concluded that Milestone VM, Garlon 3A and Dimension specialty herbicides and GoalTender herbicide all have a good fit in these sensitive-site situations.
“Although there is no single prescription for bare ground, we generally use a Dimension and Telar 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).”
Another tool PG&E is considering is to encourage plant species that can out compete species that are incompatible with electric transmission lines. One example is squaw carpet (Ceanothus prostrates), a California native common to the northern Sierras at 3,000 to 7,000 feet elevation. Bermuda grass is another example. Money sees the advantage to encouraging it along some of her rights-of-way although Bermuda grass is not native to California. A big reason for the success of Bermuda grass 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 is always evolving. 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.
Bidding for Success With Progress Energy
Before they write their herbicide bids, the four senior forest managers at Progress Energy, headquartered in Raleigh, N.C., meet to determine which products will be needed throughout the service area. Later, each tailors the prescription to suit his or her specific needs.
In 2007, the foresters wrote the bid to specify only branded herbicides. It was a great decision, said David Smith, one of the four senior foresters.
The 34-year employee of Progress Energy manages 1,883 miles of transmission line and bare ground control at the utility’s substations. Throughout his tenure, he has learned to value working with basic herbicide manufacturers.
“Because this is our first year of a large-scale herbicide program, it was important for us to have the support of manufacturers who will stand behind their herbicides,” Smith said. “We rely on the expertise of the field reps to help us make the right decisions for our rights-of-way.”
Smith and his team considered wildlife and sensitive surroundings before choosing which herbicides to include on the bid. The four foresters cited the Gamelands 33 research from Bramble and Byrnes to help improve the wildlife habitat–something Smith’s applicator, Billy Moye from Progressive Solutions, has seen firsthand.
“Using herbicides to clear undesirable plants from the right-of-way has greatly improved wildlife populations,” Moye said. “I’ve especially seen a dramatic improvement along the edges of the lines.”
In his area where 1,061 miles of line are evaluated under the North American Electric Reliability Corporation (NERC) standards, Smith deals with many wetland areas. Other sites contain desirable endangered plants. As a result, crews must be careful about where they apply herbicides while still keeping lines clear and extending treatment cycles, Smith said.
“The NERC regulations add a lot of pressure to keep tall vegetation away from the lines,” Smith said. “Simply trimming the trees back is not cost-effective anymore. We have to remove them with herbicides.”
Moye said that one of the most difficult things to do is identify various tall-growing species and control them before they create problems for transmission lines. He relies heavily on the field support of his branded manufacturers, such as sales specialists with Dow AgroSciences.
“The brush density we have along some of the lines makes it nearly impossible to use a direct treatment method,” Moye said. “Where we have to use high-volume treatments, (the specialist) really helps us find better ways to get things done.”
To battle against the most common problem species such as oak, pine and hickory, crews use tractors to apply a mixture of 2 gallons of Accord XRT herbicide, 25 ounces of Arsenal PowerLine herbicide and 1 ounce of Escort herbicide per hundred gallons of spray mixture per acre.
In areas that have been cleared or have easier access points, low-volume foliar applications are made with Accord XRT and Arsenal PowerLine. Sometimes crews run up against hard-to-control waxy species that require a different control solution. In these situations, a Garlon 3A herbicide and Arsenal PowerLine mixture is used.
Smith said the herbicide treatments make better use of his budget compared with mowing.
“It is much more cost-effective for us to manage the vegetation with herbicides when it is low rather than treat it mechanically when it is taller,” Smith said. “I’m more confident about what herbicides can do for our electrical reliability.”
Tracking Herbicide Applications
Moye strives to ensure that the vegetation is being managed efficiently and effectively. Tracking herbicide applications is a big part of that.
A large percent of Smith’s territory contains swamps and wetlands, sites that require herbicides with special label language for use in these areas. Crews spot treat with Garlon 3A in wetland areas where the high- and low-volume herbicide mixtures cannot be used.
When high-volume foliar applications go out, crews generally treat a large right-of-way area, but this can make it difficult to identify where skips around wetland areas have been made. To avoid missing areas with applications, Moye uses GPS units to help ensure application accuracy.
A GPS device on each tractor helps keep the amount of herbicide spray mixture precise to the intended volume, which helps ensure the control needed. The units take into account the speed of the tractor and will adjust the calibration of the sprayer to apply the herbicide as accurately as possible. The devices also are able to accurately map these skipped areas and come back with an herbicide mix approved for that site.
This tool, in combination with herbicide applications, has helped make the first major year of spraying a success, Smith said.
“We have seen great results with the herbicide program that has been put into effect,” Smith said. “We’ve lowered our maintenance cost compared with using mechanical treatments and believe we have a better means of keeping tall-growing vegetation away from our transmission lines.”
After the first major year of spraying, Smith is satisfied with the vegetation management program’s success. And with the service and support that comes with bidding herbicides from basic manufacturers, he is optimistic about the program’s future.
Beau Miller is a vegetation management specialist at Dow AgroSciences in Sacramento, Calif.
Travis Rogers is a vegetation management specialist for Dow AgroSciences in Charleston, S.C.