Hi Virgil,
How long is the run?.
15kV would be under-kill, because of the line current.
7.2kV lines are roughly twice the size of 15kV for the same capacity of line.
Higher Voltage=Lower Current.
Regardless of that, get yourself some good Hot Gloves and Leather Outers.
ASTM Grade 2.
I can only say so much here, but I'll give a hand should it be required.
Sorry Virgil, I never saw the 1300 foot part of your post title.
Run it through HDPE or Rigid PVC,as your Codes allow.
In my own opinion I'd use 1 Core URD, for this run.
Also bear in mind, with this sort of run, ask your PoCo or read any guidelines they may have (you may be able to find them on the web), with regard to the burying of HV Lines.
My understanding of the rules is that you either cover the thing with cement or you bury a very hard and flat "Signal Strip" at half depth of the excavation.

[This message has been edited by Trumpy (edited 06-18-2005).]