Consent sought to spill wastewater into pristine South Island lakes for decades

Monday, 17 June 2019

A fly fisherman on the southern shores of Lake Wakatipu in Queenstown.

Some of New Zealand's cleanest and most scenic lakes could be on the receiving end of wastewater overflows for several decades.

Lake Wanaka and Queenstown's Lake Wakatipu, as well as numerous rivers and streams, are included in a Queenstown Lakes District Council resource consent application to discharge wastewater – usually comprising raw faeces, food waste, heavy metals and industrial waste – to freshwater when pipes break or block.

The overflows are partly a consequence of both population growth and rising tourism in the district, which is the fastest growing in the country. Queenstown Lakes has a relatively high number of overflows compared to other councils, Water NZ data shows.

The region's high water quality and popularity with tourists form an important part of New Zealand's projected image overseas as a clean, green tourism destination.

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Such overflows already happen, but are outside any resource consent regime. The council has received multiple infringement notices for wastewater overflows and was in 2018 fined $37,500 for allowing wastewater to enter the Kawerau River.

The consent, lodged with the Otago Regional Council, would effectively legitimise existing activity, on the condition the effects were mitigated as best as possible.

The council's data shows around 200 overflows have happened over a three-year period. In 2018, the number of overflows was 50 per cent higher than each of the previous two years. A minority of the overflows ended up in freshwater.

Lake Wanaka is one of New Zealand's cleanest lakes.

The resource consent application shows wastewater is likely to occasionally end up in some of the country's most iconic lakes and rivers, over the course of several decades. It requested a consent duration of 35 years, the maximum allowed, meaning discharges could continue beyond 2050.

The council highlighted 35 sites that could leak wastewater into freshwater, as well as a further 12 that could be affected in the future. The majority of those sites were deemed to have either a 'moderate' or 'high' risk of wastewater entering a waterway in the event of an overflow.

Among the high-risk sites are bustling lakefront areas in central Queenstown and central Wanaka. In some cases, the source of a likely overflow is less than 30m from the water.

An ecological report commissioned by the council raised several concerns about the environmental impact of the overflows, particularly in the parts of large, clean lakes where the wastewater would enter.

Swimmers take water samples from Lake Wanaka as part of a water quality project started by environmental scientist Chris Arbuckle. (Video first published in July 2017)

Both Wakatipu and Wanaka are microtrophic, indicating very high water quality. It makes them sensitive to even minor changes in nutrient concentrations.

'Given the extremely low nutrient concentrations in these lakes, even seemingly small individual discharges may contribute significant nutrient loads to these systems and may contribute to eutrophication, at least locally,' ecologist Dr Dean Olsen wrote in the report.

He said most discharges would likely be short-term in nature and would not individually affect the overall health of lakes, but they could cause 'significant, localised adverse effects in the vicinity of the discharge'.

The effect would also be high on small creeks and streams, which were 'expected to be highly sensitive to wastewater discharges'. Some of those small waterways would provide habitat for species such as kōaro (a small native fish), which could be affected by pollution.

The council also commissioned a public health report from Niwa, which examined the risk of negative health effects from the wastewater discharges. Those effects would likely be low to very low, if the council's proposed response process was followed, the report concluded.

In its application, the council acknowledged raw wastewater flowing into waterways would be contentious. 'Public perception of raw wastewater directly entering a freshwater environment from an overflow is not anticipated to be favourable or acceptable' to locals and visitors, it said.

Wastewater discharges are generally seen as culturally offensive to Māori, as they reduce the mauri of freshwater. Ngāi Tahu, who are mana whenua, prepared a cultural values report for the council detailing the cultural significance of the waterways.

The view from a pumping station at Lake Wakatipu with a 'high' likelihood of wastewater overflows. It is around 30m from the lake.

In a statement, the council said its application was not driven by capacity issues, but by blockages that were 'relatively random in nature' and could not be predicted.

It said it had 'robust processes in place to investigate and respond to such incidents,' but they were not allowed under the Resource Management Act.

'[The council] is working to reduce overflows from its wastewater networks and a large part of reducing overflows will be ongoing and increased community education on what should and shouldn't be put into the wastewater system and future upgrades to the network,' a council spokesman said.

'Identifying the need for the application is indicative of council's increasing maturity and its desire to apply industry best practice in its operations and maintenance as well as infrastructure planning.'

Tourists and locals regularly pan for gold in the Arrow River.

The council acknowledged growth would put pressure on its infrastructure, and said it had planned $101m in spending on wastewater infrastructure over the next decade.

Wastewater overflows happen when there's a breakage or a blockage in the pipe system, causing wastewater to back up and spill out of a manhole or a pumping station.

They can happen during severe weather events, but in the Queenstown Lakes District, they almost always happen in dry conditions in response to a blockage.

Pipe blockages can be caused by foreign objects, such as wet wipes or building material waste, entering the system. They can also be caused by fat accumulation – so called 'fatbergs' – as well as damaged by tree roots.

Because manholes tend to be placed at the lowest points in the network, the spillages are often near lakes and other waterways.