If the water is standing above the drainlines, then the lines are not the problem. The ground is not absorbing the water, either because the field has become contaminated with soap and grease due to a non-funcitoning septic tank, or the ground has never been able to absorb water, or the ground water level is just that high. In any case, you can forget about saving the existing pipe. And probably the other one also, unless this one is lower that the other one, since the water could not rise up that high unless the other pipe was not also filled to that level. You have to run to a new area of the yard, or excavate the existing field and replace it with new pipe, gravel, etc. and test the ground for absorption before spending the money.