Imagine this: It's your job to control high-density vegetation on a transmission line R/W that spans 89,169 sq mile (143,472 km) in a remote region. The terrain is highly irregular, far from villages and inaccessible by mechanical vegetation-management methods or herbicide treatments on foot. In addition, crews have less than two summer months to control a variety of softwood and deciduous species whose sole purpose is to grow into power lines.

Welcome to Baie-Comeau, Quebec, Canada, where Hydro-Quebec (HQ) must manage this vast geographic R/W in the Manicouagan region of northeastern Quebec. HQ's main objective for this R/W is to control undesirable vegetation at the lowest possible cost while meeting regional environmental concerns. To achieve this objective, the utility chose herbicides--the most economical way to maintain R/Ws and prevent undesirable trees from growing into transmission lines.

While an aerial herbicide application is the ideal choice for managing high-density vegetation in remote areas inaccessible to ground equipment, environmental concerns in this area including waterways and wildlife habitats--necessitate herbicide application precision within a matter of feet.

To surmount this vegetation-management challenge, HQ developed a vegetation-control method that incorporates a global positioning system (GPS) into its aerial herbicide application. GPS, a satellite-positioning system, allows HQ to ensure a precise application of herbicides by helicopter while taking into account the environmental constraints that previously limited aerial herbicide spraying.

Technology Gains Acceptance Developing a solution wasn't the only obstacle HQ had to overcome. Before it could proceed with its vegetation-management program, the utility needed to gain government authorization to conduct aerial herbicide applications. To obtain the authorization, a team of specialists from HQ, including economists, biologists and chemists, prepared a detailed environmental impact study. This report looked at the utility's product of choice--Tordon 101 herbicide, by DowElanco. It reviewed the product's toxicological profile, environmental impact and treatment specifics. After presenting this study at public hearings, HQ gained acceptance from the Quebec government.

In addition to the public hearings, the utility used radio spots, advertisements in local newspapers, and direct phone calls to landowners to inform the public why using herbicides to control vegetation was necessary. For example, since an electric utility must limit service interruptions to maintain its effectiveness, vegetation management plays a major role in ensuring that trees do not contact power lines. In addition, during routine maintenance and repair, crews must be able to access substations, power lines, poles and towers easily and safely. Then, in the event of an outage, crews can quickly and cost effectively restore service without inconveniencing customers for extended periods.

Once it gained government and public support for the aerial herbicide application, HQ proceeded with its program aimed at controlling softwood species such as black spruce and balsam fir, and deciduous trees like poplar, cherry and birch.

Implementing the High-Tech Solution HQ first used GPS to map and photograph the entire Manicouagan region's R/Ws and towers within the aerial-herbicide program. Using a computer to interpret the aerial photographs, foresters noted treatment areas and vegetative species. In addition, HQ marked the Sensitive-Sites(tm), such as waterways and wildlife habitats, that needed to remain untreated. This effort was important because HQ's permit for this aerial spraying project was conditioned on its using measures aimed at protecting the environment. Following the data analysis, HQ developed a prescriptive herbicide treatment that took into account the problem species present and the sensitivity of the terrain.

To integrate this data, HQ joined forces with Naturam Environnement, a consulting firm from Baie-Comeau. After numerous trials, these consultants adapted software to the mapping program, guiding the helicopter pilot along the herbicide application sites. A control module in the helicopter cockpit receives and corrects data provided by satellites at a frequency of five times per second. This system indicates to the pilot the precise flight lines to follow. It also commands the spray nozzles on the helicopter to automatically start and stop spraying at the appropriate times by accounting for the time it takes for herbicide droplets to reach the ground.

The result is a sophisticated methodology that allows a precision aerial application of herbicides to within approximately 3 ft (91 cm). Crews now boast of little encroachment in the buffer zones along waterways and other sensitive areas in the environment. In fact, only 5% of the cases encroached more than 30 ft (9 m) into buffer zones, and two-thirds never reached buffer zones. Buffer zones in this area, ranging in width from 200 ft to 1600 ft (61 m to 488 m), serve as a neutral site between treated R/Ws and sensitive areas such as rivers that cross the R/W.

This precise application not only helps pilots avoid environmentally sensitive areas, it also eliminates residual strips of untreated vegetation. Previously, with visual landmarks, pilots often veered slightly from the line of flight, leaving untreated strips on the ground. A team then had to return and manually cut this residual vegetation, adding to program costs. With the GPS technology, a light-emitting diode (LED) bar on the helicopter dashboard indicates when the pilot deviates from the correct line of flight.

To further enhance the system's integrity, HQ built a portable meteorological station that is moved from site to site as work progresses. This station transmits weather information directly to a computer that continually informs the team of the area's weather conditions. Since a distance of up to 40 miles (64 km) can separate the operations base from the treatment site, this technology saves time and money because there is no need to visit the site to verify weather conditions.

On With The Treatments Back at the treatment sites, HQ uses only products that are most acceptable for the environment and practices good stewardship during application to protect workers and the population. For aerial spraying, crews apply 2.7 gal of Tordon 101 per acre, mixed in 9.1 gal of water and Sylgard 309 surfactant. The solution is then applied using the helicopter's Thru-Valve Boom and adapted nozzle because they minimize drift of the product into areas that shouldn't be treated.

In the treated R/Ws, compatible herbaceous vegetation continues to establish itself, leaving little room for undesirable trees. Growth of desirable plant species also promotes a beneficial wildlife habitat. Grasses, forbs and shrubs increase food prospects for small field animals and deer, while songbirds enjoy increased nesting and escape-cover opportunities. Finally, a dense grass and forb ground cover on the R/W lengthen the intervals between herbicide and/or mechanical vegetation treatments. This cuts down on labor and treatment costs, saving the utility thousands of dollars each year. In fact, treatment cycles in the region now vary from five to 10 years for mechanical cutting methods to nine to 20 years for aerial herbicide applications.

The end result: a much-improved bottom line. HQ estimates that using GPS saves 15 to 25% over traditional aerial herbicide applications and 60% over manual cutting.

Implementing an environmentally acceptable aerial herbicide program to manage R/W vegetation in remote, inaccessible areas typically creates headaches for utilities. But now, thanks to global positioning system technology, utility managers can meet these criteria while reducing costs.

Jean Turbide has been a forestry technician at Hydro-Quebec, Montreal, Quebec, Canada, for the past 15 years. He is responsible for vegetation control in power line R/Ws in the Manicouagan region in northeastern Quebec. Turbide has participated in several technical innovations in the course of his duties. Over the years, he has developed an adaptive vegetation-management approach by using control methods suited to field conditions.

Global positioning systems (GPS) can bring definite advantages to aerial herbicide applications. To implement a program similar to the one established at Hydro-Quebec, consider the following steps:

1. Determine site. With any prescription herbicide application, it's important to become familiar with the treatment area. This includes the height and density of species present. 2. Photograph R/Ws. Taking aerial photos allows planners to thoroughly evaluate the site's topography from the ground. 3. Localize sensitive areas. It's important to determine the sections of the R/Ws that cannot be sprayed. This helps determine the location and width of the buffer zones. 4. Interpret aerial photos. Using a computer, the utility can input the photos for further analysis and planning. 5. Arrange a third-party audit. Invite an external firm to evaluate the utility's proposed application plan. 6. Conduct numerous validations. Provide both internal and external tests on the ground to ensure application accuracy before treating. 7. Choose applicator. Select a competent applicator that will help ensure a precise herbicide application. 8. Attend herbicide spraying. Show project commitment and involvement by being present during the actual application.