Volume One 15. Resource Quality (Water, Air, Soil) (d) For coastal waters, limited to the extent necessary to achieve effective mixing, having regard to: (i) the characteristics of the discharge, including the contaminant type, concentration and volume; (ii) the coastal processes that exist at and near the point of discharge; and (iii) the nature, sensitivity and use of the coastal waters. Discharges of contaminants to water authorised under discharge permit must meet water quality classification standards set for the receiving waters after “reasonable mixing”. Reasonable mixing is the process of wastewater dispersing through the receiving waters and this occurs in a mixing zone, an accepted area of non-compliance. The policy establishes how to size the mixing zone. In the case of discharges into freshwater, a prescribed formula ensures a consistent and equitable approach. Such an approach is not possible for coastal water due to variation in the coastal environment caused by (among other things) tides and currents. Instead, the policy provides criteria for determining the size of an appropriate mixing zone. This policy assists to give effect to Policy 23 of the NZCPS. [R, C] Policy 15.1.15 – With the exception of stormwater discharges, the water quality classification standards will be met at the point of discharge, where a discharge is: (a) within one kilometre upstream of an intake for a registered drinking water supply from a river; or (b) to a river where the receiving waters are to be maintained in a natural state; or (c) within 500 metres of any marine farming activity in freshwater or coastal waters. Some waterbodies and coastal waters are particularly sensitive to the point source discharge of contaminants. In these circumstances, a zone of reasonable mixing will generally be incompatible with the values supported by the waterbody or coastal waters. The policy identifies those circumstances where a zone of non-compliance should not be established. This policy assists to give effect to Policy 23 of the NZCPS. [R, C] Policy 15.1.16 – The duration of any new discharge permit will be either: (a) Up to a maximum of 15 years for discharges into waterbodies or coastal waters where the discharge will comply with water quality classification standards for the waterbody or coastal waters; or (b) up to ten years for discharges into rivers identified in Policies 15.1.4, 15.1.5, 15.1.6 or 15.1.7 (where the water quality is to be enhanced) and the discharge will comply with water quality classification standards for the waterbody or coastal waters; or (c) no more than five years where the existing discharge will not comply with water quality classification standards for the waterbody or coastal waters. With the exception of regionally significant infrastructure, no discharge permit will be granted subsequent to the one granted under (c), if the discharge still does not meet the water quality classification standards for the waterbody or coastal waters. To provide greater certainty to resource users, the policy identifies the appropriate duration for discharge permit applications if they are to be granted. The duration varies depending on compliance with water quality classification standards and the state of water quality in the waterbody or coastal waters. Longer durations are warranted where compliance with water quality classification standards will be achieved and there is currently no water quality issue, while 15 – 17