Big increase in sewage overflows likely to continue

12 April 2018

Communities around the country will continue to face big increases in sewage overflows unless steps are taken to significantly upgrade storm and waste water infrastructure.

Last year there was a massive 379-percent increase in the number of sewage overflows to the environment caused by wet weather.

These findings have just been published in Water New Zealand’s National Performance Review, which benchmarks council performance around drinking water, waste water and stormwater.

Water New Zealand CEO, John Pfahlert says the impact of climate change means that without a concerted focus, more and frequent sewage overflows are likely to become the norm.

“Data in the National Performance Review reveals that in some networks the volume of sewage in wet weather can be more than ten times the volume as in dry weather.

“When it rains stormwater makes its way into the sewers in a variety of ways such as cracks in aging pipes or gully traps being incorrectly hooked up into the wastewater system and so on.

“When the capacity of pipes is exceeded, a combination of wastewater and sewage overflows into the environment.”

He says the cost of fixing infrastructure issue can be huge. For instance, Auckland is spending $1.2-billion on its new Central Interceptor to separate wastewater and stormwater flows. It is expected that will reduce the annual overflow volume to its harbours and waterways by 80 percent.

“But it’s far from just an Auckland problem. The NPR data revealed that 35 out of 41 authorities in the review report some level of sewage overflows caused by wet weather.”

He says fewer than half of the authorities in the NPR have reported design standards for preventing overflows and fewer than a quarter have standards for the frequency of overflows communities can expect.

“With local council long term plan consultations underway around the country, this is the time for communities to have the tough discussions about the level of protection we expect to afford our waterways and the price we’re willing to pay for that protection.”

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