can't let that shit get into the leach fields!
just keepin' my shit to myself.

note: it would be easier to use a "hackzall" than a sawzall because you could cut behind the pipe without worrying about falling into the tank. ...you could cut far enough back so as to get behind the joint that you cut off, then add an extension, whether or not it's SDR or schedule 40. after using the extension, make sure you get an SDR to schedule 40 adapter, if necessary for your pipes, and then install the unit.
Chiseling could be completely avoided this way.
In the unlikely case that the septic installers used better adhesive, chiseling will be more difficult.