Marlborough Sounds Resource Management Plan The water quality standard is the minimum needed to achieve Objective 5.3.2 of the Marlborough Regional Policy Statement, “that water quality in the coastal marine area be maintained at a level which provides for the sustainable management of the marine ecosystem.” Shellfish are a good water quality indicator species because of their filter feeding characteristics and their accumulation and harbouring of contaminants. The policies identified work to achieve the standard set by Objective 9.3.2.1. Discharges of contaminants from a point source to the coastal marine area have the potential to significantly affect coastal water. In particular, human sewage, even when treated, carries with it a greater potential for the transmission of disease than any other contaminant. Its discharge to water is also intolerable to Maori, therefore the necessity for stringent control over this. However, as a result of the introduction of sections 15A, 15B and 15C of the Act control of discharges of contaminants and dumping from ships will be controlled by the Resource Management (Marine Pollution) Regulations 1998. Run-off from land is possibly the most pervasive form of pollution in the Marlborough Sounds. The Plan acknowledges this both above and throughout the Plan. Control is needed at the source of the problem, namely on land. (Refer to Chapter 13: Soil Conservation and Chapter 14: Discharges of Waste to Land). 9.3.3 Methods of Implementation Rules Rules are used to control discharges to water within the coastal marine area. In particular, the discharge of human sewage as a point source discharge will be assessed as a Discretionary Activity in order to establish the impact of any contaminants on the water quality standard. The Council will ensure that appropriate assessment, monitoring and enforcement of rules will be undertaken. Mixing Zone For each resource consent application to discharge contaminants, a zone of reasonable mixing will be determined (by way of condition on the resource consent) as a means of ensuring compliance with the water quality standard (SG). Criteria to be taken into account in determining the extent of the zone of reasonable mixing include: a) The need to minimise the size of the mixing zone; b) The need to avoid, remedy or mitigate adverse effects within the mixing zone; and c) The characteristics of the discharge and receiving environment including: • Design of the outfall (eg; single or multi-point diffuser); • Depth of water over the outfall; • Density difference between the effluent (usua lly freshwater) and the receiv ing water (often saline) which determines its buoyancy; • Speed and orientation o f currents across the outfall; 9 - 12