Testing the Waters

26 January 2010

Ocean Swim participants this weekend and other users of Wellington's many beaches can feel safe in the knowledge that we're checking water quality every week - and continuing millions of dollars worth of stormwater and sewerage network improvements.

Ocean swimmers won't need to worry this weekend when competing

Ocean swimmers won't need to worry this weekend when competing

The City Council, along with Greater Wellington Regional Council, other local authorities and Regional Public Health, is again well into the summer water-testing programme - which started in November.

Until March, staff and contractors will collect water samples from 21 Wellington beaches every week. Princess Bay and Breaker Bay are checked on a fortnightly basis. The water is tested for a particular type of bacteria (enterococci), which indicates that sewage may be present.

"Monitoring the bacteria level is a way of keeping swimmers and people who enjoy other water sports safe," says City Council engineer Nicci Wood.

Water quality in Wellington harbour and on the South Coast has improved in the past decade, says Nicci.

Some of the improvements put in place by the City Council in the past 15 years have included:

  • Opening the Moa Point and Karori West wastewater treatment plants in 1998.
  • Construction of 21 sewage holding tanks as part of a $72 million project to eliminate sewage from the harbour, streams and coast.
  • Construction of a giant tank under the Michael Fowler Centre car park in Wakefield Street, central Wellington, in 2004. It can hold 850,000 litres of sewage and thus take pressure off the wastewater system and pumping stations in the event of very heavy rain or disastrous power failure.
  • The progressive detection and removal of illegal private 'cross-connections' that allow stormwater into the sewage system (the stormwater and sewage systems must not to be connected in any way). Generally these illegal cross-connections involve stormwater downpipes being connected to sewers on private property. In heavy rain, stormwater can then overload the sewers - causing overflows and pollution.

Nicci says that, because of Wellington's urban environment, it's impossible to completely remove pollution from the city's beaches. Runoff from city streets includes everything from petrol and cigarette butts to dog excrement.

"So it's not wise to swim near stormwater outlets at any time - or swim at beaches for up to 24 hours after heavy rain."

Wellingtonians have a major role to play to minimise stormwater pollution, Nicci says. "People should remember that when paint, chemicals, oil, cigarette butts and dog droppings enter the drain outside someone's house they will go into our stormwater system and end up polluting our harbour.

"It's always far easier to stop pollutants going into our drains and into the stormwater system than to have to deal with the problem at the outfall, once they're in our streams and in the harbour. Please help us by thinking before you pour something into your stormwater drain."

Greater Wellington Regional Council's website carries weekly water-quality updates in the 'Our Environment' section.