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Northland should escape serious pollution problems from mass milk dumpings provided farmers follow suggested local guidelines, the Northland Regional Council says.
The region’s farmers are among those affected by a major Taranaki gas leak which has left dairy factories out of action and unable to collect milk – possibly for some days to come.
This has left local farmers with no choice but to dump milk and the Northland Regional Council today reiterated its earlier advice to farmers about the best way to do this.
Dennis Wright, an Environmental Monitoring Officer – Farm Waste, with the regional council says milk must not be discharged in any way that enables it to reach drains or watercourses due to the serious environmental consequences.
Initially, uncollected milk should be fed to stock, but Mr Wright says by now, most pig farmers and calf rearers will already have all their storage full.
He says the next best option is to spray irrigate the milk, but it must be diluted at a ratio of one part milk to 10 parts water and applied to pasture.
Mr Wright says of the roughly 900 farms in the region which supply dairy giant Fonterra, at least 550 have land application systems.
“Once again though, land application can only be done if the spray application is kept well clear of drains and watercourses and farmers have enough water on hand to ensure it’s sufficiently diluted.”
“Those farms which don’t have a permanent land application system should consider hiring a contract slurry wagon or wagons and we suggest farmers join forces with their neighbours to do this.”
Where land application is not an option, the council recommends digging an emergency trench or pit and again suggests farmers with diggers or similar equipment help out their neighbours who don’t.
“Farmers need to choose a pit site away from drains and streams and make sure they’re constructed to minimise any leakage.”
Mr Wright says with the typical Northland farm milking 300 cows and producing roughly 8000 to 10,000 litres of milk a day, a trench five metres wide, 15 metres long and two metres deep should have enough room to store up to six days of milk.
(Those dimensions allow for sufficient slope on the pit walls and enough spare capacity to handle any rain which may fall.)
However, there will be odour from such a pit as the milk rots and the trench will need to be back-filled later.
Mr Wright says milk can also be discharged into effluent storage ponds – but only if it can be irrigated to land and those ponds do not discharge to water.
He says dumping milk into effluent treatment ponds which discharge to water isn’t an option given that just one day’s milk would exceed the ponds’ treatment capacity by up to 30 times.
“There’s a real danger that dumping milk into effluent treatment ponds which discharge to water will overwhelm the crucial bacteria living in them and which make the ponds work. It could take weeks for the ponds to recover and in the meantime any resulting discharges will almost certainly breach your consent conditions and cause long-term damage to our waterways.”
Mr Wright says few people realise that milk which is inappropriately released into the environment is actually many times more polluting than even farm dairy effluent.
“This is because it virtually eliminates oxygen from the water, kills stream life (including fish and eels) and has many other long-lasting adverse environmental effects. It also gives off very offensive odours as it decays.”
However, Mr Wright says provided farmers follow the council’s advice, Northland’s environment – in particular its water quality - should emerge relatively unscathed despite the scale of the milk dumping likely to be necessary over the next few days.
He says a number of farmers have already contacted the council for advice and anyone uncertain about how best to dispose of their milk should call the regional council on (0800) 002 004.