Stormwater Consent

5 July 2010

Water quality in Wellington Harbour and the Cook Strait has been steadily improving in recent years as a result of hundreds of millions of dollars' investment in infrastructure upgrades and renewals.

DOC and Capacity staff beside a stormwater outlet in Island Bay

DOC and Capacity staff beside a stormwater outlet in Island Bay

And it's in that favourable light that Wellington City Council is making a publicly-notified application to Greater Wellington Regional Council for a 10-year resource consent to discharge stormwater into the harbour and on the south coast.

At the moment the City Council has consents that apply to discharges from just 12 big stormwater mains around the city.

However the proposed single consent would cover hundreds of stormwater outfalls between Horokiwi, just south of Petone, to the Taputeranga Marine Reserve on the south coast.

City Council Infrastructure Planning Manager Maria Archer says the new consent application recognises the fact that stormwater enters the sea from a vast number of sites - and that all of them should contribute to cleaner natural waters and be subject to monitoring aimed at keeping harbour and coastal water quality as good as practicably possible.

Maria says just 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
  • the replacement of some 75 km of our older wastewater pipes
  • construction of 21 sewage holding tanks as part of a $72 million project to eliminate
  • sewage from the harbour, streams and coast
  • thousands of repairs on our wastewater pipes
  • the progressive detection and removal of illegal private 'cross-connections' that allow stormwater into the sewage system (the stormwater and sewage systems are not supposed to be connected in any way).

Most of these illegal cross-connections involve stormwater downpipes being connected to sewers on private property, but there are many occasions where wastewater has been connected to the stormwater pipes.

As a result, there have been dramatic reductions in contamination levels in the harbour and around the south coast, as revealed by monitoring results. In most cases faecal-coliform levels per 100 ml of water have dropped from the tens of thousands to the hundreds.

Along with the Regional Council and the Department of Conservation, the City Council is also involved in ongoing public education programmes designed to deter people from polluting the stormwater system - this will include the installation of cast-iron drain lids featuring aquatic life to remind people of the direct and untreated route that rainwater takes from the street to the harbour.

Over the past 15 years we have concentrated on ensuring that wastewater doesn't enter our waterways, but now we are focusing our attention on the other pollutants that enter waterways such as heavy metals, oils and litter.

The discharge consent will set conditions for further investigation of the effects of these pollutants in stormwater on the local marine environment and management of the risks associated with the stormwater discharges.

Maria says the public has a major role to play to minimise stormwater pollution. "People should remember that when their paint, chemicals, oil, cigarette butts and dog droppings enter the drain outside someone's house or workplace 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 in our streams and in the harbour. Please help us - don't allow anything into your stormwater drain - except, of course, rainwater."

Public submissions on the consent application are welcomed - see the link below to the Greater Wellington Regional Council website.