(1)  A major project permit lapses –

(a) after a period of 5 years from the day on which the major project permit was granted; or

(b) where the Commission has granted an extension under subsection (2)  – after a further period of 2 years –

if the principal use or development in respect of which the major project permit was granted is not substantially commenced.

(2)  If the principal use or development in respect of which a major project permit was granted is not, or is unlikely to be, substantially commenced before the permit would otherwise lapse under subsection (1)(a) , the Commission may grant (once only) a 3-year extension of the period during which that use or development must be substantially commenced.