We are thinking of getting a pool for the yard, the pool place said you can't use extension chrods and the best bet is to have a electrican come in and build a trench out side and run the wires underground. I have no clue what so ever about wiring.
Does anyone have any idea how much that might cost.
Doug.

That would really be hard to say. How far is it from you house to the pool? Are there other underground wires or pipes to work around. If you are not comfortable hooking up the electricity yourself, have an electrician come and look at the job. Ask for 2 prices, him doing the whole job, and him making the connections, but you burying the wire. Chances are, burying the wire will cost you no more than the minimum rental of the smallest trencher you can find.

I am sure the pool requires a ground fault interrupter. If your breaker box has extra space, adding a GFI breaker is no big deal. Often electrical wires are more hid in the dirt than buried. Code calls for the service into the house to be down 4'. I am not sure about lines to pools, etc. Last summer I buried my cable about a foot using nothing more than an ice scraper and lots of water. I softened the ground up with the water and shoved the scraper down wiggling it around to make a little slot, then pushed the cable down with my hand. Very little disturbance to the lawn.

Note, unless you are absolutely sure of where ALL your lines are, and they are well out of the way, call locate first. Do not count on wires being buried in a straight line.

I had the same issue when I had to run a line to my pool light. The pool guy said to hire an electrican to run the line, but I got crafty and did it myself.

Since I recently had a sprinkler pump installed, I followed the previous electricians lead and re dug up his original trench. Down here in FL, it was only about a foot down since after a foot of topsoil, it all rock hard coral. I ran 3 lines of 12 gauge stranded copper. One Power, one return line and one ground, (Black, White and Green). I had them run through the dark grey plasitc conduit and made sure everything was sealed.

It took a couple of trips to HomeDepot to get everything right, but it all worked out in the end. I'm guess you would have to have your conduit stick out of the ground near your pool pump mounted on a pole or stack.
If you are adding another GFI breaker, you can get the GFCI breaker. It costs a bit more, like $40 but everything on that break is now protected against shorts from water.

I am not an electrician, so good luck!