Why the Emphasis on Groundline Inspection?
"We had an ice storm. All the poles that broke off, broke at about 6 feet above groundline. Why are you inspecting the pole at and below the groundline?"
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Surprisingly, no one has ever asked me that question, but it occurred to me that someone might be thinking this logical question.
When you hold a pencil in your hand, one end in one hand and the other end in the other hand and apply enough pressure, it breaks. Where does it break? Never within an inch of where your hand is unless there is an abnormality at that point.
This is not a perfect analogy, but a good one. If you are able to hold one hand totally stationary and apply all of the pressure with the second hand, this would be an accurate analogy. The stationary hand is the groundline area of the pole. The pole at groundline does not move. The hand applying the pressure is the load. On the pole this is the wires, any icing and wind, equipment and weight of the pole.
In this description, assuming an eight-inch pencil with a mid point of four-inches, and uniform strength, the pencil will virtually always break between 1 and 3 inches from the stationary end.
The analogy to the pole holds, given a healthy pole, it will act in the same manner. There are two differences between a pencil and the pole. The two factors are 1) A pole is generally tapered to the groundline. This actually gives it greater strength in this area. 2) The groundline area is by far the most dynamic part of the pole, where strength-reducing activities (decay) take place.
What do I mean by “dynamic part of the pole”. Stepping back and taking a look at the big picture: Everything has a life span. Given the proper conditions, the lifespan can be greatly enhanced or severely diminished. A human lifespan of 80 years can be reduced quickly to only 3 days in the 120 degree heat of the Sahara desert with no water.
Given enough time and the proper conditions, every wood product will decay. Decay is the main determining factor in the lifespan of the average utility pole.
The key words are “time” and “proper conditions” The proper conditions for decay only naturally occur in one zone, which is typically referred to as the “groundline zone”.
What are these conditions? Decay is an organic process, which involves living organisms. For these organisms to exist and thrive, they need essentially the same things that we do:
From day one, all of the factors stated above exist on your typical utility pole except one: The food source. The pole has been treated with a wood preservative which takes it out of the “food” category. Over time the preservative will break down to a point where it become available as a food source to some fungi. This is the onset of decay.
Proper inspections and retreatments of poles in the groundline are will prevent this dynamic area from falling into the food category and will provide a “booster shot” of wood preservative in the vulnerable region.
The current recommendation for inspecting a pole is to begin when it has been in service for between 10 and 15 years.
Best Regards.
Joel
When you hold a pencil in your hand, one end in one hand and the other end in the other hand and apply enough pressure, it breaks. Where does it break? Never within an inch of where your hand is unless there is an abnormality at that point.
This is not a perfect analogy, but a good one. If you are able to hold one hand totally stationary and apply all of the pressure with the second hand, this would be an accurate analogy. The stationary hand is the groundline area of the pole. The pole at groundline does not move. The hand applying the pressure is the load. On the pole this is the wires, any icing and wind, equipment and weight of the pole.
In this description, assuming an eight-inch pencil with a mid point of four-inches, and uniform strength, the pencil will virtually always break between 1 and 3 inches from the stationary end.
The analogy to the pole holds, given a healthy pole, it will act in the same manner. There are two differences between a pencil and the pole. The two factors are 1) A pole is generally tapered to the groundline. This actually gives it greater strength in this area. 2) The groundline area is by far the most dynamic part of the pole, where strength-reducing activities (decay) take place.
What do I mean by “dynamic part of the pole”. Stepping back and taking a look at the big picture: Everything has a life span. Given the proper conditions, the lifespan can be greatly enhanced or severely diminished. A human lifespan of 80 years can be reduced quickly to only 3 days in the 120 degree heat of the Sahara desert with no water.
Given enough time and the proper conditions, every wood product will decay. Decay is the main determining factor in the lifespan of the average utility pole.
The key words are “time” and “proper conditions” The proper conditions for decay only naturally occur in one zone, which is typically referred to as the “groundline zone”.
What are these conditions? Decay is an organic process, which involves living organisms. For these organisms to exist and thrive, they need essentially the same things that we do:
- Moisture (25% and greater is ideal)
- Temperature (55 F to 90 F is good)
- Oxygen (below 18) this is in short supply
- Food Supply (once the original preservative breaks down chemically)
From day one, all of the factors stated above exist on your typical utility pole except one: The food source. The pole has been treated with a wood preservative which takes it out of the “food” category. Over time the preservative will break down to a point where it become available as a food source to some fungi. This is the onset of decay.
Proper inspections and retreatments of poles in the groundline are will prevent this dynamic area from falling into the food category and will provide a “booster shot” of wood preservative in the vulnerable region.
The current recommendation for inspecting a pole is to begin when it has been in service for between 10 and 15 years.
Best Regards.
Joel
