**Utility Poles Grade**Utility poles are divided into ten classes, from 1 to 10. The classes'
definition specifies a minimum circumference that depends on the species of tree and the
length of the pole. This circumference is measured 6 feet from the butt of the pole. There
is also a minimum top circumference that is the same for all species and lengths.
For example, a class 1 pole has a minimum top circumference of 27
inches. If it is 25 feet long and cedar (most utility poles are cedar), the circumference
measured 6 feet from the bottom must be at least 43.5 inches.
The higher the class number, the skinnier the pole. Pole lengths
start at 16 feet and increase by 2-foot steps to 22 feet, then by fives from 25 feet to 90
feet. A 90-foot class 1 western red cedar pole weighs about 6,600 pounds. A 16-foot pole
weighs only about 700.
Standards (from ANSI) severely limit or exclude various types of
damage, including bird holes and insect boring, and describe ways of specifying the pole's
straightness.
On curves, hillsides, or other locations where there's an unbalanced
pull on the pole, standard practice calls for increasing the portion of the pole that is
buried. For example, for poles being set along a straight line, 6 feet of a 35-foot pole
would be buried, but if the pole were on a curve, 6.5 feet.
A 35-foot pole is a typical length used in cities to carry one or
two crossarms. Poles are spaced about 100 feet to 150 feet apart, with 125 feet being
typical. |