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A claim that raw sewage was pouring into Millstream, behind shops in Elizabeth Street Warkworth, during heavy rain last week, has been confirmed by Watercare.
According to information provided to Mahurangi Matters, raw sewage discharges into the creek are now a regular occurrence and have happened at least nine times since May 21. The largest volume was on July 15 when 225 cubic metres (225,000 litres) went into the stream.
Watercare wastewater planning manager Andrew Deutschle says Warkworth’s wastewater network currently has a ‘bottleneck’ in Elizabeth Street – a low point in the network – and the pipes in this area are nearing capacity.
“When it rains, stormwater can enter the wastewater network and exceed the capacity of the system, causing it to overflow,” he says.
He says engineered overflow points in the network are there to minimise public health risks by reducing the likelihood of overflows of sewage onto private property.
As a result, the untreated sewage is going straight into the river with no public health warnings or water testing. Watercare says testing and signage are an Auckland Council responsibility.
Council’s environmental health response team leader Alan Ahmu says council has not carried out testing or erected signage along the Mahurangi River in response to this week’s overflow as it is not considered “an immediate risk to public health”, especially outside of the recreational bathing season.
Ahmu says long term water quality monitoring is done monthly in the freshwater section of Mahurangi River but is not designed to specifically detect events such as overflows nor is it suitable as surveillance testing for human health risks.
Watercare was asked why it did not install a holding tank at the Elizabeth Street discharge point, which could then be pumped into a tanker and properly disposed of at a treatment plant. It responded that it wasn’t feasible to build a tank in this location big enough to collect the combined sewage and stormwater during heavy rain.
“The long-term solution to these overflows at Elizabeth Street is the north-west growth servicing pipeline,” Deutschle says.
The raw sewage flows into the river are also threatening the long-term viability of oyster growers on the river, with some saying their businesses will close before the new pipeline is even operational.
