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In this week’s Protecting our Water series Guardians of Lake Wanaka chairman Dr Don Robertson considers the Queenstown Lakes District Council’s application for a 35-year consent to discharge wastewater into waterways.

A licence to put sewage in our lakes and rivers?

The Queenstown Lakes District Council (QLDC) has announced that under the Resource Management Act it is seeking consent from Otago Regional Council (ORC) for permission to “discharge water or contaminants to water”.

QLDC states that the source of the water is “sewage” and the contaminant is “wastewater/sewage from the public system”. It seeks a consent to discharge sewage to water for 35 years.

At first glance this request might seem outrageous. In fact, it is.

But if we look closely, we see there are many accidental overflow events resulting from bad planning, bad behaviour or just plain bad luck.

Over the last four years, these events resulted in 206 sewage spills from the 421km QLDC drain network, and 17 spills have flowed into water.

For some of these spills, QLDC has been fined by ORC because QLDC does not have a consent to spill sewage into water.

Risks of spills are real. Of 47 pumping stations, 17 are in a position to allow sewage to flow into a lake, and of these 11 have a “high” or “moderate to high” probability of causing wastewater to enter a lake.

As a concerned community we face a choice.

The community can let ORC know how it feels about the application. Do we allow sewage spills to continue or do we use this consent application as an opportunity to recommend that ORC sets in place strong conditions?

These could require QLDC to invest in global best practice for ongoing management of the entire district sewage/wastewater reticulation and all aspects of potential negative impact. Why would we do anything less?

The conditions could place requirements on QLDC on how to avoid, mitigate, and remedy sewage spills into water, including aquifers. We could insist on steps to reduce the frequency of overflows and consequent risks to human health. Concentration of Norovirus in sewage, for example, can range up to 10million infectious units per litre.

Part of the application examines many of the issues and likely effects of the spills, but concludes for most that negative effects are “no more than minor” or “less than minor”. Each of these should be carefully revisited during the consenting process and conditions developed to ensure impacts are in fact “less than minor” or “no more than minor”.

One of the consent application reports, by Niwa, addresses microbial risk assessment of sewage spills into water. Ideally, the report would have provided a Quantitative Microbial Risk Assessment (QMRA) to quantify health risks to recreational water users. The author of the Niwa report would have done this, but was unable to because “much of the data required to undertake a QMRA do not exist”. This conclusion points to the need for consent conditions which ensure that measurements are made so that such risk assessments are possible.

Understanding and managing effects of sewage spills into our lakes is limited by absence of research on water flows, retention times, mixing, ecosystem effects and the way a spill into each lake at any of the points of risk will behave when it enters the lake.

Dr Robertson is also a member of the Guardians of Lake Hawea and trustee of the Upper Clutha Lakes Trust.