Quality upgrade costed at $1800 per household
Invercargill residents' rates could double overnight if high water quality standards are imposed on local councils.
Invercargill City Council chief executive Richard King said an Environment Ministry report using Invercargill as a case study was "grim reading".
The report shows that if water quality standards were imposed by the Government, requiring the council to reduce key pollutants phosphorous by 50 per cent, heavy metals by 80 per cent and all hydrocarbons and solids by 80 per cent, the financial implications could put a lot of pressure on ratepayers.
"The effects of quality limits on stormwater are likely to be significant. In order to ensure all stormwater in Invercargill complies with higher water quality limits i.e. to reduce key pollutants, it is expected to cost more than $1800 per ratepayer household per year," the report says.
King said the report was concerning, but he could not see how the Government could expect councils to foot the bill.
"It's not a viable option, it would bankrupt New Zealand.
"It's very very difficult and extremely costly to fix if that is going to become regulation."
The report did not take Bluff or areas beyond urban Invercargill into account.
"It would double rates overnight, in fact it might even go higher. The ramifications are absolutely huge."
However, the report outlines three possible options for the council to pursue to improve water quality - avoidance of contamination, treatment at source and treatment before discharge.
Invercargill City Council solid waste and drainage manager Malcolm Loan said the council was already working on educating people about what they put down their drains.
It was necessary because the council's consent with Environment Southland was up for renewal in three years and they had to meet the water standards already in place, he said. The city had 150 discharge sites, going into five different catchments.
The council would have to improve the water before it went into the pipe, or fix it when it came out, he said.
That left the council with two options - educate people about what they were putting down their drains or treating the water before it went into waterways.
The water could not be put through the sewerage system because the large volumes during high rainfall could cause it to overflow and it would be a large expense to pipe it there, he said.
When the city council applied to Environment Southland for consent two years ago, traces of faeces were found in the water and the council had been asked to monitor the water quality during its consent period and file reports to Environment Southland.
The council was trying to improve the storm water quality, he said.
The report states the true cost of improving storm water quality would not be known until the Government set the bottom line for water quality and Environment Southland set a timeframe in which the council had to improve its water quality.
The Government can set the new limits through the National Policy Statement under the Resource Management Act or create new legislation under the act.
Regional councils will then be able to set the quantity and quality limits for their region as long as they are above those standards, the report says.