A fine of up to $200,000 could be slapped on Gore District Council after a silt-removal process carried out at the Mataura water-supply dam resulted in the contamination of the Pleura Stream.
Environment Southland (ES) is investigating the contamination of the stream, which came about when a system using straw bales to remove silt from the dam failed, ES compliance manager Mark Hunter said.
The incident happened shortly before Christmas and ES had a timeframe of six months to carry out an investigation and decide on a course of action, Mr Hunter said.
Gore District Mayor Tracy Hicks said bales of straw were used to filter water from the dam in order to remove silt, and that system had worked in the past.
However, he believed the wrong type of straw had been used on this occasion and silt ended up in the creek.
Gore District Council utilities manager Ross Haslemore said the same method of removing sediment from the dam had been used in 2004 and on one other previous occasion with success.
The council used large bales of straw in the process. However, in this instance the bales had moved, allowing silt to contaminate the stream.
‘‘It was unfortunate they [the bales] moved,'' Mr Haslemore said.
The silt-removal process was prompted by having to shut down the Mataura water treatment plant while silt was cleaned out of the filters.
The silt influx into the treatment station was caused by a combination of a heavy rainfall and stock being moved which caused a lot of sediment to be washed into the dam in addition to the build-up of sediment that was already there, Mr Haslemore said.
After the contamination occurred, the council carried out remedial work on the stream, he said.
Council chief executive Steve Parry said ES halted work once the contamination was discovered.
ES was prompted to investigate the contamination after receiving complaints from the public, Mr Hunter said.
The straw bales were placed in the stream with the intention they would act as a filter to remove sediment. However, that did not happen.
Instead, the bales which were placed on the stream floor dislodged and floated to the top and the effectiveness of the method was compromised, Mr Hunter said.
‘‘What we are concerned about is the amount of sediment going down that small waterway and the effect that sediment will have on the life of that stream,'' Mr Hunter said.
Of particular concern was the impact the contamination would have on invertebrates living in the stream, he said.
Ferndale farmer Cyril McFadzien, whose land the dam is on, said his son David had questioned the council about the legality of flushing out the dam using that method.
Mr McFadzien contacted ES to check if the council had a discharge permit and was told they did not.
Because the matter was under investigation, Mr Hunter said he did not wish to comment on whether a consent had been issued or not.
Mr McFadzien said if a dairy farmer had done the same thing they would be in jail by now.
‘‘It [the creek] was just a slurry. I was devastated. It kills everything in the creek,'' Mr McFadzien said.
‘‘It's actually still quite contaminated on the banks,'' Mr McFadzien said.
ES has the authority to take action under the Resource Management Act.
Potential penalties include a fine of up to $200,000 or a prison sentence of up to two years.
However, given the body under investigation was not a person, the imposition of a prison sentence was not an option, Mr Hunter said.
Environment Southland's investigation will include gathering scientific data and compiling a report.
Mr Hunter expected the investigation to be completed within two months.
