Old cess pit

[eigoya]

Buying a home near ocean in HPP. Surprised to find it on a cess and not septic. It's 30 years old, but we want to add a bath eventually. I imagine a new permit will trigger an upgrade. Should I pay to inspect or just figure Ill need to replace in the next year or so? What I read on-line says to beware of walking near cess pits but here I have never come across that worry. Is the engineering in Puna different than other places (UK) ?
Any info greatly appreciated