The Hawke's Bay Regional Council's investment company HBRIC has decided not to appeal against a board of inquiry decision on the $600 million Ruataniwha water storage project.
The Regional Council earlier announced that it would also not appeal.
The council's lawyers told a meeting on Wednesday that they don't believe the limit placed by the board on nitrogen leaching in the Tukituki River is based on robust science.
But they said an appeal regarding nitrogen limits would be unlikely to succeed because appeals are limited to points of law.
Radio New Zealand News understands some environmental groups are still considering whether to appeal.
The project still has some major hurdles to overcome, including finding enough investors and customers.