Extract from the Executive summary

The Auckland Council has developed the Auckland Unitary Plan (the Unitary Plan) to help shape the way  Auckland grows. The Unitary Plan will replace the Auckland Regional Policy Statement (ARPS) and the 12 existing district and regional plans (legacy plans), many of which are already more than 10 years old.

It has long been recognised that stormwater runoff is a predominant contributor to water quality and stream and coastal ecosystem health in Auckland. As a result, stormwater management has been a significant component of the approach to managing fresh and marine waters in the operative ARPS and the Auckland Regional Plan: Air, Land and Water (ALW Plan) and Auckland Regional Plan: Coastal (Coastal Plan).

The Unitary Plan continues to develop and refine this approach to improve environmental and community outcomes and address gaps in the current approach to stormwater management. In particular the Unitary Plan seeks to better integrate the management of land use and development and associated adverse effects, with a greater focus on the generation and management stormwater at or near‐source. This is consistent with the direction provided by the National Policy Statement for Freshwater Management 2011 (NPSFM), the New Zealand Coastal Policy Statement 2010 (NZCPS) and the Auckland Plan.

As part of development of this broader approach, Auckland Council has also reconsidered the performance requirements for the management of stormwater contaminant and flows that is currently required by the legacy plans and current practice. The reconsideration of stormwater contaminant management has stemmed from concerns that the current performance requirement for stormwater quality, generally 75 % removal of total suspended solids (TSS), does not adequately address the contaminants of concern (which may not be sediment) from an activity. Also the specification of a removal percentage does not guarantee the effluent quality from a device (as this is dependent on influent quality). ...

Auckland Council technical report, TR2013/035

Auckland Council, August 2013