I have always wondered how much of the telephone pole is buried under the ground versus the amount extending above the ground, and whether they cement the pole into the ground or just pack dirt around the pole.
Telephone poles are extremely stable, although some of their stability is due to the guy (sp?) wires that are often used to anchor the pole to the ground.
I’m referring to a standard wooden-style pole as you might see on the side of country road, not a concrete-style pole found in some cities.
Watched them put in a new wood power pole today. Looked to be about 3 1/2’ or so in the ground. You’ll notice that most poles have no guy wires attached. They are usually added if there’s a direction change in the line or a transformer mounted.
Around me I think it’s generally 6 feet putting it at least some of it below the frost line. They only put in guy wires when they think it may be necessary. In some cases the guy wire also serves as a ground for the transformers. They usually are not cemented but again they might opt to for more stability.
Keep in mind there is usually only limited regulations for utilities. They get to set their own guidelines and assume limited liability when something bad happens. One week they might think 6 foot is the optimum depth the next they might decide 4 is enough.
I work at an electric utility. At my company, the standard minimum wood pole setting depth is 10% pole height + 2ft. So a 45ft pole will be set 6.5 ft deep, a 50ft pole will be set 7ft deep, etc. Although our standards are guidelines, and can be deviated from, to my knowledge this one is never compromised. Among other things, it is a safety issue for the crews who will be climbing the pole.
One of our power poles (we have 2 on our property) got condemned a couple of years ago, so I got to watch them replace it. They buried it 6 feet deep (which is 2 feet deeper than a normal footing would be sunk in my area) and they did not put any concrete at the base. Both of our power poles have guy lines. I assume they use these just to make lawn mowing more fun :D.
Back in the '60s they used to coat the poles with creosote. Anybody know what they use now?
Former BellSouth tech here. The 10% + 2 feet is generally the rule. The one thing I wanted to comment on was the statement that the poles look Extranet stable, for the most part they are, but they do trend to move side to side quite a bit when climbing them. Also, when climbing a pole one of the most important things to check prior to mounting is the base for rot, either due to termites or general decay. The wrong time to discover the pole is rotted away 4 inches below the ground is when you twenty feet up on it. This is usually done by taking a long screwdriver and prodding the base of the pole below the surface. If you screwdriver penetrates the pole it isn’t a good idea to climb it. One of my coworkers didn’t and the pole broke off. He laid with a pole on top of him for a few hours until he was discovered.
As for me, my pole climbing days ended in 2003 when I cut out at 20 foot. The fall want bad, but that landing was a real bitch!
Thanks. Helpful info. I have acquired some telephone poles for ham radio use and this is helpful. I think new poles (2015) are generally “green,” as in “Wolmanized” or “pressure treated,” as opposed to creosoted like the old ones. For those of us reinstalling them, I think there are paints and or treatments we can heavily coat the in-ground part with that should help resist rot.
Also, I may use a couple for running AC overhead to a barn and perhaps even further, to a couple deer stands, and maybe a couple of the appropriate length as light stands for my daughter to ride her horse after dark in our fields. (best time of day, perhaps, in the hot summertime!) Also, they are quite good, the shorter ones, to use as really sturdy gate posts, like an 8’ length with a couple feet in the ground. Really solid. They are also useful horizontal for a garden on a slope, kind of a retaining wall, like railroad ties would be used.
I don’t ever recall poles being treated with creosote. It leaves too much residue on the surface, although there may have been some smaller utility companies that used it. Normally crosote is used for pilings. I do know that many third world countries used creosoted poles.
Most poles in North America are treated with a green preservative with one of the most common called CCA. If I recall, it stands for copper, chromium, arsenate.
They also use pentachlorophenal, which is an oil based preservative. Environmentalists have hit it pretty hard, but then have a look at what’s in CCA.
Also, poles in NA are multiples of 5’, with the most common lengths being 35, 40 and 45 feet. Normally, a 35’ pole is set 5’6" in the ground, a 40’ is 6’ and 45’ is 6’6". These are standard depths but can go deeper depending upon soil conditions and load factor. This is for distribution poles.
Longer poles are called transmission poles and can run up to 100’ and more.
With regard to the formula for calculating sink depth - is the in-ground length in addition to the height above-ground, or part of it i.e. is a 100’ pole actually 112’ long, or is it 100’, but only 88’ above ground?
I’d be curious to know under what circumstance this is allowed. In all my years in the electrical game, I never saw this practice. In fact, I was under the impression that it is expressly forbidden to allow any possibility that a guy wire might become energized. That’s why the installation of a strain insulator (“johnny ball”) is necessary: to protect the public.
Like everything else in this world wood poles are graded and sized. Last I was aware (about 10 years ago) The classifications in the US are
Class 1
Class 2
Class 3
Class 4
Class 5
H1
H2
H3
You can buy them in 5 foot increments and up to 110 feet long.
My brother works for a phone company. They use the same formula, but deviation is always to bury more of the pole, never less. That is usually because of the type of soil in the location – they have many marshy, unstable soils to deal with.
