A report on the geological studies for the potential sites for water storage dams on the Ruataniwha Plains has assisted both Hawke’s Bay Regional Council and the project leadership group to assess the viability of several sites.
During the prefeasibility process the Regional Council started with an initial list of 30 potential sites. This was then worked through and reduced to down to 14 sites of which 6 were considered most likely.
These original 14 shortlisted sites have had on-ground, physical geological/seismic assessments over the last 2 months. Of these, 5 are now considered unsuitable because of ground condition risks. Some of the remaining set of sites is looking very positive but further assessment work is still underway. Relevant landowners in these areas are being contacted by Hawke’s Bay Regional Council and informed as sites are removed off the list.
“This is a completely normal part of the process to assess potential dam sites. It’s a complex project and our feasibility study as much about excluding sites that have risks as including sites needing further investigation,” said Bruce Corbett, Group Manager, Water Initiatives for Hawke’s Bay Regional Council.
The study report was presented to the Ruataniwha Water Storage Dam Leadership group chaired by Sam Robinson earlier this month. The group is working with Hawke’s Bay Regional Council to step through the feasibility work for the proposed water storage dams.
The geological studies have shown that there is ample dam site capacity in the north of the Ruataniwha Plains area but in the south there is less available storage capacity which reduces options, particularly in Takapau.
The Council will focus further assessments now on sites where geological fatal flaws are not apparent, and where sufficient and economically achievable storage can go ahead. Fortunately, there is very good geological data available for the area which identifies a lot of the numerous fault lines and unsuitable soils.
Eight of the potential sites now being studied can provide 90 – 110 million cubic metres compared to the maximum storage requirement of 90 million cubic metres to serve the entire area of 22, 500 ha. Likely dam positions close to those originally identified are also being looked at.
The new and repositioned sites will reduce pumping requirements as they are more gravity fed. Two sites also offer hydropower potential.
GNS seismic studies are currently underway to confirm the geological assessments. This will also provide dam design parameters which will influence construction costs and therefore further decisions.
Parallel to this, the Regional Council’s water project team will be working with the Ruataniwha Water Users Group, and will meet with current irrigators and major dryland farmers in the irrigation zones to gauge and prioritise demand for stored water.