Contaminant limits 'some years' away

The Marlborough District Council has no immediate plans to cap the contaminants dairy farmers can release to waterways, environmental scientist Nicky Eade says.

The Government's national fresh-water policy statement required local government to set contaminant limits for each catchment by 2030, Ms Eade said.

Setting those limits would need a huge amount of data, which was not yet available. "The Marlborough District Council will defer anything specific for some years," she told dairy farmers at a field day last week.

Nitrate and potassium pollution was minor in Marlborough compared with intensively farmed regions, Ms Eade said.

Dairy farms might fill 10 per cent to 15 per cent of a catchment, shared with native bush or forestry, compared with about 80 per cent in the Waikato. That could change if farmers increased the size of their herds, she said.

Bacteria from dairy cows was a problem, Ms Eade said. Faecal tracking confirmed E. coli from cows in three of four samples collected by the council in 2010 from sites including Moenui Bay, at the head of Pelorus Sound.

The council would do more faecal tracking at poor sites this summer to check whether bacterial pollution came from cows, humans or sources such as birds.

The council starts its dairy-shed effluent surveys this week with a focus on silage leachate, she said.

The building of bridges and culverts stressed in previous years was mostly complete, with only a few priority sites still outstanding.

There was room for two more farmers to take up the council offer of a farm plan identifying ways of keeping effluent out of waterways, Ms Eade said. Three of the 10 budgeted for this year were finished and five were booked.

Farmers were charged $1500 for the three-year work plans, which cost up to $4000, Ms Eade said.

Most dairy-farm pollution came from just a few hotspots and problems could often be easily fixed, she said.

Water testing showed urban waterways such as the Taylor and Opawa rivers were among the worst-polluted in Marlborough, she said. The council was reviewing stormwater systems with the aim of making improvements.

The Marlborough Express