A MANAGED SYSTEM FOR DISTRIBUTION FORESTRY

The maintenance of vegetation that affects or has the potential to affect electric distribution lines goes beyond the periodic treatment of existing trees and brush. Utility managers must understand and continuously address why the brush and trees are there. Tree and brush density has to be managed as a prerequisite to actually doing the physical work. The managed system, applied to distribution forestry maintenance, sets performance standards for doing the work and utilizes reliability as a measure of effectiveness. The system which is based on the distribution feeder, categorized by customer type, right of way location and/or landscape is dynamic and can be changed or adjusted in response to quantitative results from the performance indices. These performance indices, when fully developed, will help the manager to determine which areas of the operation require corrective attention. The treatment of vegetation affecting an electrical distribution systems costs a lot of money, and for some, this expenditure represents the highest cost component of distribution maintenance. I will explain how Ontario Hydro proposes to manage its distribution forestry program. Initially, let me state some basic statistics on Ontario Hydro: We are a publicly owned corporation supplying electricity at the wholesale level to 321 municipalities serving 2.2 million customers and 103 direct customers. Our installed capacity is 24.7 million kW and utilizes 35% nuclear, 34% hydraulic and 3 1 % coal. Our own distribution system has approximately 101,000 km (60,000 miles) of line and serves 760,000 customers. The service area covers 650,000 square kilometers (250,000 square miles), 1,000 km (600 miles) north to south and 1,600 km (1,000) miles) east to west. Utility arborists and foresters must know what kind of forests, or countryside, supports their system. Ontario is characterized by four forest zones; Deciduous, Great Lakes, Boreal and Tundra. Our authority to do work is provided by government statute, the Power Corporation Act. This document gives us the legal right to maintain the vegetation as it affects our facilities. It is corporate policy to obtain occupation rights to clear and keep clear vegetation on our rights of way, and to treat any danger trees off the right of way. We have an electrical distribution system with over 100,000 ha (260,000 acres) of right of way, capable of supporting literally millions of trees. Historically, the forestry operation was managed using the standard tree treated (trim or remove) as the basis for resource decisions. Unfortunately, its use did not give management sufficient knowledge for adequate control, and it was easily abused. For example, as crews became more mechanized in the 1960s and '70s, aerial lift devices were replacing manual climb crews. We found that aerial lift crews would treat more trees on any given right of way than manual climb. A man in the bucket, at one set up, would trim perhaps 3 or 4 trees, where a climber may ascend and trim only 1. The tree count goes up, manhour per tree decreases and more aerial devices are required, if this production information is to be believed. That's the reason utility management must look into why the trees are there, and implement the required processes to manage tree density and establish a tolerable workload. Some examples we use to manage tree density are (1) A chemical brush control program. (2) Tree replacement program. We remove weed trees and provide the landowner with a slow-growing replacement planted away from our lines. (3) Billing stuffers to customers and handouts to nurseries and municipalities on where not to plant trees. (4) Periodic newspaper advertisements. Any managed system, whether manufacturing automobiles or clearing vegetation from power 1. Presented at the annual conference of the International Society of Arboriculture in Indianapolis, Indiana in August 1983. Journal of Arboriculture 10(6): June 1984 185 lines, can be depicted as in Fig. 1. For utility arborists, it is clearing brush and trees to a certain reliability standard by means acceptable to the general public. Initialy one needs a plan that includes programmed cycles (to determine required clearances) and job specifications. One then must organize. At Ontario Hydro we have our 55 administrative locations headed by forestry foremen, functionally guided by forestry supervisors in the six Regions who, in turn are functionally guided by Head Office. Resources, either our own forces or external contractors, are given the required training for the work. Direction is the supervision given to crews, contractors, Areas and Regions. The control must be expressed both quantitatively (relationship of work done to production standards) and qualitative (relationship of work done to tree caused outages and adherence to arboricultural specifications). Starting with the plan, Ontario Hydro has opted for the job package approach with the distribution feeder as the basis for planning and executing forestry work. In our system, there are approximately 2,400 feeders, which seems to be a good population for work management purposes. The feeder has advantages over other work packages, such as geography (land feature or political boundaries): Clearing By Feeder vs. 1. Better Reliability 2. Crew knowledge of electrical system an asset for safety and storm repair. 3. Facilitates planning program changes. Clearing by Geography 1. Political boundaries facilitate municipal contacts. all locations which contain a high proportion of intensive farming. An on or off-road aerial device could complete the majority of necessary work. Low tree densities are encountered and perhaps enhanced by the continuously managed land on both sides of the R/W by farmer and road authority. B. Rangeland (marginal farming). This includes all locations having adjacent land classified as marginal for farming. On or off-road equipment can complete the majority of the work. Tree density and brush problems are greater than in the agricultural setting. C. Urban residential. This consists of locations high in customer density; hence, is characterized by having a large number of primary and secondary services and three-wire "bus." Mature tree trimming and removals are the major portion of the work-load. An on-road aerial device can complete the majority of the necessary work. There are few brush control problems, e.g. subdivisions and beach locations. D. Rural estate. This encompasses all residential areas of much lower customer density than category C and usually has higher tree densities. Work can normally be completed by on-road equipment. The trees in question make up a significant portion of the landscape scene and constitute a higher dollar value. E. Mixed-hardwood (on-road). This includes non-agricultural land containing a high percentage of on-road trim work. The major work load involves the treatment of hardwood tree species. There is a high density of trees per kilometer and brush control is a substantial portion of the cycle right of way maintenance program. The next step in the planning process is to categorize these 2,400 job packages by existing vegetation type, so feeders possessing similar landscape characteristics can be grouped ORGANIZE together for quantitative (production) and qualitative (reliability) comparisons. We came up with nine different categories for feeders, which are described as follows: Management unit categories A. Agriculture (intensive farming). This includes Figure 1. TRAIN