IT sounds like these are the phone/cable lines that serve your house. Most likely a rear yard feed coming off of a pedestal that is in a ROW off the back of your lot line.
You should be fine putting the pool over them. If your excavation is too deep, and it will hit the lines, ask to have them moved. They will call for a mark out, then once it is done, come by with a plow, and will plow in a new line. Depending on when you development was built and how it was built, sometimes things get changed and service drops go across yards. Most of the time, when placing buried service, they try to do so logically, along the edge of the property for example, but sometimes that does not work out. Other times it is a sub-contractor doing the work, and the shortest path (in other words, least amount of copper/fiber) is a straight line.
-dave