Wastewater network under pressure

By Joseph Aldridge


Tauranga residents are using their toilets as rubbish disposal units, flushing away unwanted objects with the push of a button and causing hundreds of thousands of dollars damage, a drainage manager says.

Every day, dozens of nappies, cotton buds, condoms and cigarette butts are flushed down suburban toilets and into the city's wastewater network.

Mobile phones, rings, wallets, driver licences and false teeth also find their way into the system although it's doubtful they were intentionally flushed.

Then there's the infamous deep fry unit found blocking the pipes in Arataki, or the hard hat that council contractors initially mistook for a human skull.

Some of these 'foreign objects' make it all the way to the sewage treatment plant where they are removed and thrown away.

However many objects get lodged in wastewater pipes and cause a blockage or an overflow.

Tauranga City Council drainage services manager Graeme Dohnt said blockages can cost as much as $3000 to fix, while overflows need to be investigated, cleaned up and water quality monitored, costing up to $5000 per incident.

Last year, there were 11 overflows and 60 blockages in the Tauranga area.

This figure is significantly down from the 47 overflows and 192 blockages reported in Tauranga in 2007.

The reduction is largely due to an education programme launched by the council in 2007 which uses street signs and booklets to educate people on what not to flush down the toilet, Mr Dohnt said.

While incident numbers have decreased, foreign objects and fat blockages still cause the majority of problems.

Just last week a build up of fat in the pipes near Bayfair shopping centre caused a sewer blockage.

"When fat's in hot water it's okay, it keeps flowing, but it comes out into a pipe and it cools down rapidly and solidifies and just goes into lumps and gets hooked up on anything inside the pipe," Mr Dohnt said.

People should wipe cooking fat out of pans with a paper towel and dispose of it in the rubbish, he said.

Pollution prevention officer Toby Barach has a simple catchphrase he uses to educate people - "if you didn't do it, don't flush it".

While the council contracts out the work of fixing pipes and cleaning up overflows, Mr Barach always attends incidents to assess the impact on the environment and set off warnings if necessary.

If an overflow of raw sewage gets into a waterway, the harbour could become unsafe to fish in and beaches may become hazardous for swimmers.

Warning signs are put up at such locations when there is a health risk, Mr Barach said.

The council was proud of its record in recent years, Mr Dohnt said, with the number of blockages falling from 11.6 per 100km of pipe in 2009/2010 to 5.5 in 2011/2012.

This compares to a national average of 34 blockages per 100km of pipe (2002/2003) and 49.5 blockages per 100km of pipe in Auckland's North Shore (2007/2008).

Fed by a network of pipes stretching 1098km, Tauranga's two treatment plants process an average of 24,000cu m a day.

Between 7am and 9am was the major peak flow period of each day, followed by a smaller peak between 6pm and 8pm, Mr Dohnt said.


- Bay of Plenty Times

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