Before you dig call Miss Utility, it's the law!
You hit a power main I don't think a puny irrigation pipe is going to be of concern, you'll be dead instantly although granted
that may be what some folks want during hard times, I don't know but there's also like a thousand dollar fine associated.
Failure to call Miss Utility can and will result in serious headaches!
The more the homeowner insists that there's nothing there, the bigger the headache.
Purposefully not making the call is a crime.
Oh, one more thing...
You can't cut below ground level with a chainsaw.