Silt and Sediment Control

This page outlines the Silt and Sediment Control Bylaw adopted by Porirua City Council on 9 April 2008.

Guidance on silt and sediment control

In this section, there is also further guidance on silt and sediment control for small building sites in Porirua City  This has a number of web pages stepping you through the Council's expectations, along with images of acceptable and unacceptable practices.  See the link below to Small Building Sites Minimum Erosion and Sediment Control Requirements.

The purpose and principles of Porirua's Silt and Sediment Control Bylaw supplements the purpose and principles of the Resource Management Act 1991.

Photo showing aerial view of Porirua Harbour. Reason for Silt and Sediment Control Bylaw

The main aim of erosion and sediment control Bylaw is to save Porirua's Harbour (which includes Pauatahanui Inlet).

Porirua Harbour needs saving because it is silting up, becoming shallower and its aquatic life is being smothered and killed by contaminants, which includes sediment off small building sites.

Development in Porirua is increasingly on small sites from 50 to 2,500 square meters.  Sediment leaving these small building sites, is causing significant problems with the way the Harbour operates and exists.

A lot of people do not realise that once material gets into the Council's stormwater drains, it is generally not filtered out of stormwater, but simply gets discharged into the Harbour.

Almost everything that does down the stormwater drains will end up in the Harbour.

A lot of people also do not realise that cumulatively across the City, and from further a field, sediment coming off small and large building sites, which gets into the Council's stormwater drains and then into the Harbour, is having a massive bad effect on the quality of Porirua's Harbour.

Scientists predict that unless significant changes are made now, to the way we are operating in Porirua, Porirua will have no harbour in approximately 200 years time.

Porirua's biggest asset is in jeopardy and the time for education and action must occur now.  The Council has therefore introduced the Bylaw to address this problem.

The Bylaw

The Bylaw states that owners of properties must ensure that any development activity disturbing the soil is carried out in a way to prevent soil erosion and to stop silt and sediment from entering the stormwater system or watercourses as required under the Resource Management Act 1991 and the Building Act 2004 and their amendments.

The Bylaw states that no person shall carry out any development activity in relation to any land without first ensuring that:

  • surface runoff from the site is isolated from other sites and roading systems; and
  • surface runoff from the site containing silt and sediment is prevented from entering the stormwater system or watercourses; and
  • silt and sediment control measures are installed, where necessary.

Guidance of how this can be achieved in relation to small building sites is set out below.

Application of Bylaw

The provisions of the Silt and Sediment Control Bylaw are in addition to any other measures that may be imposed by Resource Consent or under any provision of the Resource Management Act 1991 by either the Greater Wellington Regional Council (GWRC) or Porirua City Council. In the case of Porirua City this extends to the controls contained in the Operative Porirua City District Plan.

Compliance with the Bylaw does not remove the need for any property owners to obtain all or any consents required under the Resource Management Act 1991, the Building Act 2004, or any other Act, regulation or bylaw and their amendments prior to their commencing any site work.

If a request made by Council officers to undertake work so as to comply with the Bylaw, is not met, is ignored or not completed sufficiently, this could result in formal enforcement action and/or the Council undertaking the work on your behalf and recovering the costs under section 187 of the Local Government Act 2002.

Links to more silt and sediment control information

Porirua City Council links:


  • 'Living Waters' website with interesting 3 minute clips about various qualities of Porirua Harbour, which Porirua City Council is committed to protect and enhance.