69. Rules relating to water quality---(1) Where a regional council---
   (a) Provides in a plan that certain waters are to be managed for any
         purpose described in respect of any of the classes specified in
         the Third Schedule; and
   (b) Includes rules in the plan about the quality of water in those
         waters,---

 the rules shall require the observance of the standards specified in
 that Schedule in respect of the appropriate class or classes unless, in
 the council's opinion, those standards are not adequate or appropriate
 in respect of those waters in which case the rules may state standards
 that are more stringent or specific.

   (2) Where a regional council provides in a plan that certain waters
 are to be managed for any purpose for which the classes specified in the
 Third Schedule are not adequate or appropriate, the council may state in
 the plan new classes and standards about the quality of water in those
 waters.

   (3) Subject to the need to allow for reasonable mixing of a discharged
 contaminant or water, a regional council shall not set standards in a
 plan which result, or may result, in a reduction of the quality of the
 water in any waters at the time of the public notification of the
 proposed plan unless it is consistent with the purpose of this Act to do
 so.