Testing stormwater

In the interest of public health and the environment, the Council monitors stormwater pollution throughout the city.

There are thorough sampling schedules and standards to test for pollution from sewerage, heavy metals and other contaminants. Our testing schedules and standards meet the requirements of both the Health Act and Resource Management Act.

Testing locations

Samples are taken from 83 sites around Wellington, from Tawa to Breaker Bay:

  • 32 beaches
  • 24 streams
  • 27 culverts (large stormwater pipes discharging into the sea)

Every site is tested fortnightly for sewage pollution. Tests for other environmental health indicators are performed throughout the year.

Testing schedule

Wellington's stormwater is sampled and analysed by an independent IANZ-accredited laboratory.

  • Fortnightly - all 80 sites are tested fortnightly for faecal indicator bacteria (faecal coliforms, E.coli and Enterococci).
  • Monthly - nine stream sites are tested monthly for environmental health indicators including pH, oxygen levels, water clarity and colour.
  • Quarterly - 13 sites are monitored every 3 months for visual indicators of environmental degradation including oil and grease films on the water.
  • Twice a year - six large stormwater culverts are sampled for traces of heavy metals including copper, zinc, aluminium and iron. These metals can enter the stormwater network from cars, pipes or roofs.

Improving water quality

The Council commits resources each year to improving water quality in streams flowing into the inner harbour and along the south coast.

Stormwater sampling is used to find problems in our network such as damaged pipes, cross-connections or sewage overflows.

If a high result is reported, more testing is conducted on nearby pipes to isolate the source of the problem. Closed-circuit TV is also used to identify specific faults with pipes and to develop an appropriate response.

The Council holds consents with the Greater Wellington Regional Council (GWRC) to discharge contaminated stormwater to the coast. We report our test results to GWRC at the end of each financial year.