Sometimes a good pole line can go bad, not because of decay or aging but because the soil around the pole just won't hold it up straight. Sandy soil, muddy gumbo-type soils, swamp land are just a few conditions that many utilities have to deal with to some degree. Entergy, headquartered in New Orleans, serves more than 2.3 million retail customers in parts of Arkansas, Louisiana, Mississippi and Texas — some parts of which can get pretty wet and muddy.
Everyone has heard of the Mississippi and Louisiana swamps, but there is muddy gumbo even in the northeastern portion of Entergy's 112,000-sq-mile service territory. Entergy has found that pole lines in soft soil or wet soil become vulnerable to wind loading. In addition, the sheer weight of the conductors on its ever-expanding system adds more stress to the pole line foundation. Over the years, these soil conditions have continued to be a challenge. And, Entergy pole crews have tried everything to keep poles straight and upright.
One solution that has been around awhile is polyurethane foam or “PoleCrete” as one manufacturer, BMK Corp. (Earth City, Missouri), calls it. Once the formula is mixed the foam begins to expand immediately, making an indestructible foundation around the circumference of the pole that is three times stronger than undisturbed dirt. But even the polyurethane foam is put to the test when trying to mix it in a wet hole.
In wet conditions and high-water table situations, the pole hole often fills up with water. And when the hole is full of water, you have only a few options. Sometimes you can pump the water out of the hole, and then fill it with foam. You can fill it with pea gravel if you have good access and can get the gravel to the hole.
But one solution that Entergy crews discovered that works is what they call “bagging the pole.” Before setting the pole in the hole, the crew first puts the butt of the pole in a plastic bag. This foam mixture is then poured into the bag. A crew member holds the bag in place while the pole is dropped into the hole. By doing this, the foam expands inside the bag without being diluted. It actually pushes the water out of the hole and sets the pole.
This process is now used throughout the Entergy maintenance system. This bag-the-pole process sometimes requires a little more PoleCrete for a normal dry-hole situation, but the problem of an unstable pole foundation is solved. Recently, when a crew removed a pole that was set in PoleCrete, the mature polyurethane foam around the pole came out attached to the pole along with some of the surrounding earth.
In many cases, the foam around the pole also acts as an erosion deterrent, like washout area along roadway embankments and along river and creek areas.
Polyurethane foam is truly unique. Once you see it in action, you won't forget it. Once it is mixed, in a few seconds it begins to expand. The foam comes in several kit sizes. The 1-gallon kit is used for straightening poles, the 3-gallon kit is used to set distribution poles and the 5-gallon kit is used for setting transmission poles.
So far in 2006, Entergy pole crews have used an estimated 4000 1-gallon kits and 6400 3-gallon kits on nonstorm-related pole installations.
Robby Canterbury has worked for Entergy for 23 years. In his present position as senior procurement specialist, he is responsible for supporting 26 satellite storm rooms in southern Arkansas and northern Louisiana. He is based in Little Rock, Arkansas, at the Entergy North Distribution Center. email@example.com