Vegetation management has been a concern for Clallam County PUD since its inception. During the early decades of the PUD when population growth was flat and district crews had more time at their disposal, teams of laborers would ground brush the regrowth of trees under and around our power lines while the line crews would identify older, established trees threatening the integrity of our electrical system and trim or remove them accordingly. By the late 1970s a new trend developed in Clallam County with a surge in new industry and an explosion in population growth. All of that required extensive expansion of our infrastructure, thereby effectively reducing the available manpower necessary to address any vegetation concerns.
By the mid-1980s, as increasing demands were being placed on the nation’s power grids, a loosely-defined mandate filtered down from the Federal government requiring all utility companies, as well as the railroad and highway departments, to incorporate some sort of integrated vegetation management program in order to ensure the safe, reliable delivery of goods and services. In an effort to be in compliance, Clallam County PUD instituted its first-ever integrated vegetation management program with specific goals in 1985. Realizing crews were not available to trim trees, other options were considered, not the least of which were utilizing outside contract crews and aerial trimming with helicopters.
It was also apparent that crews of laborers could not keep pace with the regrowth of trees, especially in the West End of Clallam County, which is a rainforest environment. Because the area enjoys a mild, temperate climate with rainfall measured in feet rather than inches, tree growth far surpasses any other areas. It is common for deciduous trees like alder, willow, and maple to grow six to nine feet a year, depending upon soil conditions. With well over a thousand miles of overhead line, as well as hundreds of miles of access roads, it was apparent an alternative to teams of laborers was needed to address the District’s vegetation problems.
In 1986, Clallam County PUD took possession of its first mechanical brushing device, a tractor with a “brush hog” on the end of a hydraulic boom. This machine was capable of removing more trees in a day’s time than could be accomplished with several teams of laborers using chainsaws. Management also took into consideration the probable growth rate of trees and tentatively decided upon trying to maintain a five-year cycle for mowing.
Another weapon in our arsenal is the ability to use herbicides, specializing strictly in basal application targeting nothing but the fresh-cut stumps. Although our vegetation management crew maintains continuous certification through the Washington State Department of Agriculture, the use of herbicides has always been limited, mainly due to self-imposed restrictions, and always within the guidelines of the law. For the most part, the use of herbicides has been reserved for those areas both inaccessible to the brushing machine and extremely difficult to reach on foot.
Over time, vegetation removal by mechanical means has proven extremely effective. The brushing machine actually breaks open the stumps of the trees exposing the root system to the elements. That is usually sufficient to prevent regrowth. When cutting trees by hand using chainsaws, cutting them as low to the ground as possible removes most laterals (potential for limbs,) thereby increasing the odds of the root system dying before it has a chance to regenerate. This method also eliminates the potential for injury to crews from high, sharp stumps in the event they have to work in the area during outages.
In 1985, every circuit in every service area maintained by Clallam County PUD bore massive tree growth under the lines, with many of those trees growing up through the lines and burning. At least 50% of all the spans within the District were saturated with 75% to 100% of tree regrowth, and at least 10% of those trees were burning. Although two-thirds of our overhead lines are in the east end of Clallam County, the tree growth was heaviest in the West End from Lake Crescent to the Hoh Reservation, as well as from Sappho to Neah Bay, especially under the highline. For that reason, it was initially decided to devote six months in each of the two areas and, because rainfall was so intense during the fall and winter months in the West End, making it difficult to operate the brushing machine off road, it was further decided the brushing machine would work west during the driest six months of the year. After completing four 5-year cycles, that type of growth has become rare, and burning trees are scarce.
With each completed cycle, it became easier to cover more miles, thereby affording an opportunity to introduce three-year cycles in some areas. That was a critical turning point in our efforts to retard tree growth, especially in the West End of Clallam County. Growth rates vary considerably, nearly span by span, depending upon soil conditions, amount of rainfall, exposure to sunlight, and competition with other types of foliage. And contrary to popular belief, brush does not inhibit tree growth. As a matter of fact, it provides a nurturing environment for trees by shading young trees against the heat of summer and the freezing temperatures of winter. Brush retains moisture in the ground, even in the summer, thus keeping tree roots vibrant and healthy, and decaying foliage in the winter acts as mulch to protect young tree roots from exposure to freezing conditions. The succession of plant life and how plants interact with one another is outlined in what is termed the “Terminal Forest” theory. In essence, a patch of bare ground exposed to direct sunlight is immediately taken over by the grasses, which, in turn, are eventually supplanted by low-foliar growth, such as ferns as salal. Low-foliar plants are replaced by larger foliage, such as salmonberry bushes, elderberry, and mountain ash, and even the noxious weed scotch broom. During all of this transition, tree seedlings are being nurtured and it isn’t long before this dense brush is overcome by the emergence of alder, willow, and maple, to name a few. These deciduous trees can maintain their dominance for many years by human measurements of time, but from a geological standpoint, they are quickly displaced by evergreen trees. Initially, spruce and hemlock prevail, but the ultimate terminal forest ends up being Douglas Fir and Western Red Cedar, depending upon which soil conditions favor which trees.
From the perspective of an electrical utility company, the ideal vegetation to encourage would be the grasses and the low-foliar growth. Anything larger not only creates working hazards for line crews during power outages, but these larger plants have a tendency to intrude upon roads and highways not only obstructing the vision of motorists, but also making it difficult for motorists to see wildlife about to leap into traffic. This same dense foliage also impedes the ability of emergency teams to respond to victims of vehicle accidents when the vehicles have left the road.
With those considerations in mind, Clallam County’s vegetation team has made efforts to remove as much dense brush as possible in the course of removing trees, keeping in mind both employee and public safety as well as the need to provide for the safe, reliable transmission of power to our customers.