The Hawke's Bay Regional Investment Company approached the Trust in late May and numerous internal meetings with its members had been held since.
The company chief executive Andrew Newmam said an investment by Heretaunga Tamatea would align extremely well with the scheme's fundamental values of making a positive contribution to improving the health of the Tukituki River and building economic resilience, including offering employment opportunities to local iwi.
"If this investment is made it will give them a strong voice at the table in relation to cultural, social and environmental issues which are clearly extremely important to tangata whenua."
Mr Newman said the group's willingness to talk publicly about the relationship they had developed was a positive development.
Having the hapu show interest gave the scheme increased confidence, "all investors are very keen to see iwi involved as it helps ensure the scheme is grounded in the community it serves," Mr Newman said.
"We have strong confidence in this investment proposal, provided all the other elements come together."
At a meeting tomorrow, regional councillors will be asked to confirm that all pre-conditions necessary for the release of $80 million in ratepayer funding for the Ruataniwha irrigation scheme have been met.
If they have, the project can proceed.
This discussion, along with one on Deloitte's independent financial review, will be held in a public-excluded session.
The "secrecy of proceedings" has angered a group of ratepayers who will protest at the meeting. Organiser and Central Hawke's Bay mother Paula Fern said it was past time the "bare facts" were revealed as to why Hawke's Bay Regional Investment Company recommended public funds should be invested in the scheme.
"There's not one river that's ever been improved by being dammed, and we need more transparency of process when councils attempt to justify backing such schemes, not less," she said.
Regional councillor Tom Belford labelled the process an "abomination".
"If one were specifically tasked with concocting a decision-making process offering the absolute minimum of transparency, due diligence and responsible financial and legal stewardship on the part of councillors, this would be the process," he said.