Water contaminant reduction

Contaminant reduction project objectives

The purpose of the contaminant reduction programme is to reduce litter and pollutants in our waterways and marine environment.

The programme’s key aims are to:

• reduce sediment in the Kaipara Harbour by improving stream stabilisation and preventing erosion – a key source of sediment
• reduce litter, sediment and heavy metals concentrations to Omaru Creek and Tamaki Estuary
  improve erosion and sediment controls on small building sites that would not otherwise be captured as part of monitoring and inspection
• reduce contaminants captured and transported in stormwater to help meet national water quality standards incorporated into the National Policy Statement for Freshwater Management.

Historical network legacy

In many parts of Auckland, our stormwater networks were constructed at a time when water quality management was not a design requirement.

These areas would often capture stormwater in pipes that discharge directly to the natural environment, including streams and coastlines.

Urban contaminants – including road dust, hydrocarbons, heavy metals, sediment, grass clippings and litter – also get transported in these stormwater networks when it rains and end up in the environment.

Current contaminant reduction work

A number of major projects are already underway.

Closing the Gap project

Improving erosion and sediment controls on small building sites has shown the effectiveness of enforcement in protecting the environment. Small sites with correct erosion and sediment controls in place increased from 11 per cent to approximately 20 per cent by the end of the initial trial period.

Glen Innes Town Centre contaminant reduction project

This project aims to retrofit water quality treatment devices in the existing stormwater network to capture contaminants and improve the water quality of Omaru Creek. Devices have been selected specifically to treat the water quality issues identified at Omaru Creek, including elevated copper and zinc concentrations from the commercial and light industry around the town centre.

Root Tensile Strength project

This project measures the physical properties of 10 native waterway plant species found in Auckland. This information will be used to develop erosion management planting plans and then be trialed at erosion hotspots around the Kaipara.