Stockton fish survey shows mine water-improvement working

13 March 2012

Stockton fish survey shows mine water-improvement programme is working

A survey of native fish in the Ngakawau River and its tributary streams shows Solid Energy’s programme to improve the quality of water leaving Stockton Opencast Mine is succeeding.

Results from the fish survey, completed in late 2011, were shown to members of the Stockton Community Consultative Group on Thursday (8 March). Negotiation with this group in 2005 set the objectives for the water improvement programme, including focusing on the health of native fish as an indicator of overall river health.

The survey results compare favourably to a baseline study done in 2005, with much larger overall numbers, a greater proportion of younger fish which have successfully returned from the sea and a wider distribution throughout the survey area. The survey looked at a native fish called koaro, one of New Zealand’s five migratory whitebait species. Koaro is a good climber and strong swimmer, able to overcome the river’s fast-flowing gorge and substantial waterfall to reach the headwaters.

Mark Pizey, Solid Energy General Manager Environment, says the survey results are very encouraging to the company and its neighbours. “In one of the headwater streams, the survey team recorded 24 times as many fish as in 2005 and a good number are younger, recently-returned fish,” he says. “The report indicates that if we can continue to counter the acidity and keep making progress on the water cloudiness – and I believe we will – then it seems likely that several more fish species will colonise the river and its tributaries.”

In recent years Solid Energy has spent many millions of dollars on a range of systems to avoid, reduce or treat contaminated water from current and historic mining at Stockton Mine. They deal with sediment, coal fines and acid rock drainage, created when water and air come into contact with the naturally occurring pyrite in much of the rock on Stockton Plateau.

That spending will continue as mining on the plateau moves to new resource areas. The prevention and treatment systems are now fully deployed across the Mangatini Stream catchment, one of three main catchments which flow from the mine to the Ngakawau River, and plans are in place for their staged deployment in the other two catchments – those of St Patrick Stream and Mine Creek. Large-scale Mangatini catchment works started in 2006. The first of the St Patrick Stream catchment works began last year, with the refurbishment of the old St Pats dam as a sediment detention structure.

The Ngakawau River fish survey was undertaken for Solid Energy by Golder Associates. Golder’s Dr Richard Allibone says the results show the upper Ngakawau catchment has had significant increase in koaro recruitment (from the sea) in the past three years. The present population of koaro appears to have undergone a substantial shift from low numbers of large, ageing fish to a population with much higher juvenile recruitment. These changes coincide with the water-quality improvements occurring in the Mangatini Stream, he says.

The March 2012 Golder Associates report, Native Fish Distributions and Recruitment in the Ngakawau River Catchment, is available on the Solid Energy website, under Publications and Resources -- Reports and Submissions.

ENDS

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