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.”