Gareth is bang on to describe the Mokihinui Dam proposal as ‘far-fetched’ and ‘unconsentable’. It’s the Conservation Act not the the RMA that makes the dam proposal ‘unpermit-able’ (if thats even a word!).
The Mokihinui River is conservation land. The Minister of Conservation can’t just give away conservation areas for non-conservation purposes.
The case law is a 1995 High Court declaration Buller Electricity Ltd v Attorney-General  3 NZLR 344 that said that the Minister of Conservation was correct to decline to give away the Ngakawau River for a hydro dam as it wasn’t a conservation purpose.
Meridian and its advisors have only themselves to blame for the $18m dead-loss (and also DOC’s costs). When they initially scoped out the feasibility of the proposal, they should have realised that the Buller Electricity precedent was a very high hurdle to cross.
I can only presume that their initial scoping suffered from ‘optimism bias’. It was also their choice to pursue resource consents before receiving formal access to the conservation land from the Minister of Conservation.