[TowerTalk] new member with tower question

[Jim Hoge]

Patrick,
   
  There is another issue you must contend with- drainage of water and condensate from the tower legs of any tubular tower. I am a tower monkey in the DFW area and I cannot begin to tell you how many freeze splits I have seen in the tower legs because of inadequate drainage. I removed one Rohn 25 tower that was very similar to what you have proposed. The tower base was dug down about 2 1/2 feet until the caliche was hit. The tower legs rested on the caliche rather than a bed of gravel and the concrete was poured. The freeze split on one tower leg was 4 1/2 feet above ground, far above the normal 1 foot I see in the area. Rohn specifies a gravel bed for drainage for this very reason. By only digging down until you hit the caliche, you are compromising the mass of the base and if you put in the gravel, even more so. The caliche can be dug out with effort, something you will need to do for the guy posts anyway. A hammerdrill can be used to to start a hole and once you have an
 area to break off the  caliche into, it will break. One step up the tool ladder is a demolition hammer. The bottom line is don't cut corners on the installation. Follow the manufacturer's specs. They are there for a reason. If you can't make it work, don't guess, get a engineer involved. BTW, do you have overhead powerlines or a drop nearby? My personal safety factor is 2 times the height of the tower to the nearest line.
   
  73 es gl,
  Jim W5QM