Could you get them to lower the line?   It has been done here, but the line is usually in the middle of the field.  

Last year we removed a little finger of trees that jutted out into a field, the pipeline went through it, the trees were the size of a 5 gallon bucket, of course we had to cut those with a saw.    We put a field tile down that ditch and found out the line was abandoned and there wasn't even a pipe there.  You would think their paperwork would show it.