The New Zealand Plant Conservation Network

Does Pittosporum tenuifolium have deep roots that might enter an old clay sewer? My neighbour intends to plant them as a hedge on our common boundary right up against my old 2 storeyed wooden cottage and right over my sewer. His landscaping plan has been approved by WCC.

No idea. Try asking Dr Chrissen Gemmil at University of Waikato. I don't have her email but you can find it easily enough. She is the Pittosporum expert in this country.