"We do have two institutional investors sitting there in negotiation with us," he told an audience of about 80 at yesterday's lunchtime meeting.
"One of those institutional investors is capable of doing that entire amount of money on their own, and in fact would be willing to do more subject to a couple of key issues being sorted out."
Mr Newman declined to name the companies HBRIC was in discussions with but said one "could fit quite nicely with Ngai Tahu".
Ngai Tahu said this week its reasons for withdrawing included that a replacement co-investor had not been found after Trustpower's departure.
A board of inquiry issued a draft decision last month granting consents to build the Ruataniwha scheme but setting strict environmental conditions in the Tukituki catchment which will affect farming and growing businesses in the area where irrigation from the scheme would be available.
Mr Newman said HBRIC's investment process with the dam was "in a bit of a holding pattern while we understand what the final impact of the board of inquiry decision is".
The board is considering submissions on its draft decision and is due to issue a final ruling by late June.
Mr Newman said if the final decision resulted in the scheme being "operable" and sufficient water user agreements were signed, "then I'm not concerned about raising the capital".
HBRIC director Sam Robinson, who was also at the Havelock North meeting, said he believed a workable set of environmental rules for the Tukituki catchment would result in farmers and growers signing up to take at least 40 million cubic metres of water a year from the scheme - a minimum level set by HBRIC to make the scheme viable.
However, no water users had yet signed up, he said.
"Farmers are, appropriately, not signing until they know what the board of inquiry is going to do," Mr Robinson said.
"They're ready to sign and I predict if the board of inquiry come out with a decision which is workable for farmers, the 40 million [cubic metres of water] is in the bag."
Mr Newman said the corporate investors HBRIC was talking with were New Zealand companies. Infratil, the listed infrastructure company and major shareholder in Trustpower, was not one.