You are joking aren't you? Never heard of go around, late touchdown etc? Now on to the subject matter........If there is just 3 conductors it is likely it is the HV supply to the area feeding a step down transformer along the route somewhere. Probably 11,000 volt but may be higher.
A good guide as to the voltage is have a look at the insulators on the poles. That's those grey things (usually) but can be black or clear. How many rings are they along the insulator? If only 3 then around the 11,000 volt is my guess. More is higher 110,000 volt will have 8 or 10 rings etc.
The higher the voltage the more it will cost to put them underground because a higher grade insulated cable will be required along with the ducting etc. I don't know what the rules are in your state but usually only the power network will carry out this work so your at their mercy as to the cost. My rough guess is at least $20,000 depending on what type of soil your dealing with . Rock, clay etc. The obvious thing to do is go and see them and ask for an estimate before you do anything.
Hope that helps. Good luck.