Westport, Aug 4 NZPA - A company proposing a northern Buller hydro scheme has accused Meridian Energy of making a nuisance submission.

Hydro Developments Ltd (HDL) wants consent to build a hydro scheme on the Stockton Plateau.

Meridian officially supports the scheme, but its submission to yesterday's hearing in Westport contains several proposed conditions, including that HDL not be able to feed power to the national grid.

HDL project manager John Easther today called Meridian's submission an embarrassment, put together purely for commercial gain to stymie a rival hydro development.

Meridian submitted in support, adding the conditions because it could not be seen to oppose a hydro scheme, he said.

The state-owned enterprise had decided to frustrate the process with its proposed conditions, in order to stay part of the process.

Meridian is awaiting word on its own northern Buller hydro scheme on the Mokihinui River. Despite adjourning months ago, commissioners have not returned with a decision, which is expected this month.

In Meridian's written brief, it revealed it had serious misgivings about HDL's scheme.

Meridian said that while it recognised that more power generation was a good thing, HDL's scheme lacked detail. The submission noted that the West Coast regional and Buller District councils shared these concerns in their joint planning report.

Meridian said commissioners must consider whether they could approve a scheme lacking in detail about effects.

Without a clear articulation of exactly what was proposed and a complete assessment of effects the granting of consents may be premature. In particular, there was lack of evidence about visual effects, technical information on whether ground was suitable for dams at Mt William and Weka Creek, and lack of evidence to support the generation claim.

Meridian called on the commissioners to view the power generation landscape on the West Coast as if its own Mokihinui and TrustPower's Arnold River power schemes had the go-ahead. The three schemes would put a serious load on the electricity grid.

It asked the commissioners to limit HDL's scheme to supplying the West Coast.

HDL appeared to believe that the proposal was a stand-alone project, however the reality of the matter was that everything in the electricity system is inter-connected to ensure supply met demand while avoiding over or under supply.

HDL wants to harness branches of the Ngakawau River on the Stockton Plateau through a series of tunnels, power stations and reservoirs, diverting water to an offshore outfall 600m offshore from Granity.

Two power stations would generate electricity. Scheme backers say it would provide a continuous base load of about 25 megawatts.

A drop of more than 555m between the highest reservoir and ocean outfall would be the means of generating electricity from small water volumes. The proposal would decontaminate the Ngakawau River by diverting its mining-polluted branches.

The hearing is set down until the end of this week. It is before three commissioners, two representing the Buller district and West Coast regional councils, and one representing Conservation Minister Tim Groser.