Mass of wipes and fat behind Lake Taupo wastewater spill

A wastewater system blockage at the top of Matuku St in Taupo caused a manhole cover to pop on Sunday evening. Wastewater then got into stormwater grates and from there, into Lake Taupo.

A fatberg — a collection of wet wipes mixed with congealed fat — has caused the latest wastewater spill into Lake Taupo, this time at Two Mile Bay.

But the real culprits behind the spill, the ninth into the lake since January last year, are people flushing wet wipes down their toilets and pouring fat into their sinks.

Increasingly frustrated Taupo District Council staff are mounting a public education campaign, calling on people to protect the lake by taking more care with what goes down the drain.

Wastewater includes water flushed down the toilet and water from bath, sink, washing machine and other domestic sources.

Of the nine wastewater spills, four were caused by drain blockages, including road seal, roots, wipes and fat, and council operational services group manager Kevin Strongman said it was predominantly wet wipes and fat that caused the most trouble.

Blockages in wastewater pipes cause the water to back up, increasing pressure. This causes manhole covers to lift and wastewater to escape.

Mr Strongman said this week's spill at Two Mile Bay came when a manhole cover at the top of Matuku St near Richmond Ave popped because of a wastewater blockage. The wastewater then flowed on to the street and into nearby stormwater grates which empty into Lake Taupo.

The latest spill was discovered at 9pm last Sunday and workers found the blockage 50m from the manhole, he said. A sucker truck was used to try and recover as much of the spill as possible where it exited the stormwater outlet.

"It doesn't necessarily matter where the overflow is, if it gets into the stormwater pipes, it'll go into the lake."

Mr Strongman said wet wipes, even those marketed for toilet use, did not biodegrade quickly enough to be able to be flushed into the wastewater system.

"As far as we are aware the toilet ones are just as much of an issue."

Mr Strongman said everybody was frustrated by the recurring wastewater blockages, and said thinking about what went down the drain was "probably not front of mind" for most people.

"It's a pretty disgusting job [clearing the blockages] but it's our job and we'd like to not have to deal with so many of them."

Wet wipes and nappy liners should go into the rubbish bin and fat could be left to cool down and disposed into the rubbish or wiped out with paper towels and put into the bin.

"People tend to flush [fat] down the sink with hot water so it doesn't block their own personal pipes but it goes into ours and congeals there."

The council spends $100,000 each year using CCTV cameras to inspect pipes, another $50,000 per year flushing pipelines clean with high-pressure water and $700,000 on renewing pipes each year.

The first round of post-spill water testing at Two Mile Bay showed bacteria and E. coli in the water. Further results were expected yesterday morning.

The no swimming warning applies to the area immediately around the stormwater outlet at the end of Hawai St. The council is planning a leaflet drop and advertising campaign to raise awareness of the problem.

A spill last week at Acacia Bay was caused by human error, when contractors failed to restart a water pump.