Residents living near wastewater oxidation ponds in eastern Christchurch are being plagued by “apocalyptic like” swarms of midges, a community board member says.
Coastal community board member and New Brighton local Alex Hewison said the insects had caused some people to temporarily move out of their homes.
Midges have been a problem for the community for more than a decade, but Hewison said recent damp weather had created ideal breeding conditions for them at the nearby Christchurch City Council wastewater treatment plant.
“When you have a wet summer the midges tend to come but we haven’t seen to this extent ever in my opinion,” he said.
“It’s very apocalyptic like. There’s thousands and thousands of them swarming in little clusters together.
“We’ve got residents that can’t open their windows or doors, the midges are swarming and breeding in any stagnant body of water they can find, and when people are packing up and temporarily moving out, something needs to be done.”
Hewison said midges had impacted a larger area this year, from Southshore to North Beach.
“Our east side community has been through so much with the impacts of the wastewater treatment plant fire, and now that we have a solution to that it’s time that we find a solution to the midges and prevent this from getting worse as soon as possible.”
Christchurch City Council head of Three Waters Gavin Hutchison said the council was monitoring the situation closely.
He said the increase in midges had come from algae flourishing at the wastewater treatment plant’s oxidation ponds after recent wet weather.
“Algae are a food source for midges and the increase in algae has resulted in a surge in the number of midges on and around the oxidation ponds, with numbers much higher than the previous few summers,” he said.
“Algae helps the pond system operate well by generating oxygen within the ponds and preventing the anoxic conditions which can cause odour. We’re still waiting on odour monitoring for the holiday period but we are anticipating that this will show a decrease in odour coming from the ponds which were a source at the end of last year.”
The council had been running a midge control programme since 2018, which included native planting around the oxidation ponds.
“Native plants encourage midges to stay close to the ponds rather than spreading to local residential and commercial areas. Since 2018 we have planted approximately 75,000 native plants around the oxidation ponds,” Hutchison said.
“In the past, when the ponds were healthy, we dredged the bottom of the ponds and altered the flow paths through the ponds to reduce midge numbers. We’ve considered these control options but have decided against them at this time as there is a real risk of disturbing and unsettling the health of the ponds, which could generate odour.”
