Scientists engaged by environmental groups including Forest & Bird, Fish & Game and the Environmental Defence Society have disputed the validity of a nutrient impact model developed for the council, TRIM, which they say plays down the environmental harm the dam would cause.
The groups had asked the board of inquiry to appoint an independent expert to assess the TRIM model but in a written decision released yesterday, inquiry chairman Justice Lester Chisholm ruled against that course of action.
"Both sides rely on numerous expert witnesses to support or discredit the TRIM model (as the case may be)," Justice Chisholm said.
"Undoubtedly this evidence will be carefully tested by cross- examination at the hearing."
The ruling came on the same day HBRIC announced a joint venture between Spanish contractor Obrascon Huarte Lain (OHL) and New Zealand's Hawkins Infrastructure had won a two-way contest for the right to build the dam and associated water distribution infrastructure.
OHL-Hawkins beat off competition from French contractor Bouygues Construction, although the council said Bouygues "remains as the consortia in reserve if negotiations with OHL-Hawkins do not reach a satisfactory outcome".
OHL says on its website it has significant operations in 30 countries and is ranked 21st among the world's largest international contractors. Hawkins Infrastructure is New Zealand's largest privately owned construction company.
HBRIC said there was an ongoing "comprehensive process" to determine the exact design and cost of the scheme and a final construction contract would not be signed until resource consent was obtained (following the board of inquiry decision), investors had been confirmed to fund the project and farmers had signed up to take water.
Two potential investors, South Island iwi investment company Ngai Tahu Holdings and power company TrustPower, had been briefed by the expert panel which weighed up the competing construction bids.
Hawke's Bay iwi Ngati Kahungunu has opposed the scheme but says if it is approved, the size of the dam should be scaled back by a third.
Yesterday Ngai Tahu confirmed it had agreed with Ngati Kahungunu that environmental, cultural and economic factors would determine if it proceeded with an investment in the scheme.
"We see infrastructure projects as core investments but they do have to be environmentally sustainable and in line with intergenerational aspirations," said Ngai Tahu Holdings chief executive Mike Sang.
Sustainability issues will come to the fore when the five-member board of inquiry begins five weeks of scheduled hearings on the Ruataniwha scheme and an associated change to the council's regional plan in Hastings on November 18.
