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(21) We have therefore come to the conclusion that the Board should be given' power by an amendment of the Drainage Act to prescribe by by-law what charges undertakings should be required to pay for the disposal of their trade wastes. We also consider that the Board should be empowered to require an undertaking to install and maintain at its own expenses such meters or other appliances as may be required in orderto measure the volume of the wastes. (22) The next question requiring consideration is how the cost of providing the sewers necessary to convey the wastes from industries to the main sewers should beborne. We consider that where the waste can be discharged into existing local sewerswhich are connected with main sewers it is unnecessary to make any special provision. If, however, it is necessary for a new local sewer to be provided, the expense of this : should depend on whether this sewer is to be used only for trade wastes or for trade wastes and domestic sewage combined. If the sewer is to be used for wastes only, then the cost should be borne by the Board. If, however, it is to be used for both wastes and domestic sewage, the cost should be proportioned between the Board and the local authority on an equitable basis. If an existing local sewer has to be altered to taketrade wastes, the Board should bear the expense. It would be advisable, we think, for any disputes arising in connection with the cost of providing or altering local sewers to be determined by arbitration. (23) We have given careful consideration to the question whether, pending the establishment of sewers by the Board to enable the trade wastes which are now discharged into the Manukau Harbour to be received by the Board, it is possible to take action to abate the nuisance that now exists. It will necessarily be some time beforetrade wastes can be discharged into any sewerage system constructed by the Board. In the meantime, however, the pollution that exists in and about the Mangere Inlet is,, as we have pointed out, very serious, and we consider that it is imperative that action should be taken to effect at least an improvement. We recognize that it might be unreasonable and impracticable to require an industrial undertaking to install expensive equipment for treatment of trade wastes on their premises which, on the completion of the sewerage system, may become unnecessary or quite useless. On the other hand, there appears to be no'reason why the more harmful of the wastes should not be disposed of by incineration or other suitable means without undue expense so that to some extent at least the menace to health at Mangere Inlet would be at least mitigated.. We recommend that the Harbour Board and Health Department should, without delay, consider what steps can be taken to effect an improvement. It is possible that thepowers possessed by them at present may not be adequate. If this is the case,, additional powers should be given. We recognize that the Harbour Board and Health Department have for some years been concerned about this matter, and we understand that the only reason why effective action has not been taken before was the expectation held by them that the Drainage Board scheme would be constructed without much further delay. It seems clear, however, that, even if complete plans for a sewerage system were to be decided upon within a short time, some years must elapse before that system can be put into operation, and in the meanwhile, unless action is taken, the existing' nuisance at the Mangere Inlet will continue and possibly be aggravated. (24) In addition to action being taken to bring about an improvement pending the execution of the scheme, we think that action on the following lines could also be adopted. When a scheme is adopted it is probable that the sewers and outfall in connection with the scheme could be constructed without much delay and that the construction of treatment-works will take a longer time. We think, therefore, that the Board should ensure that the construction of the sewers and outfall is put in hand as soon as possible as well as the construction or alteration of any local sewers that may be required so that, as soon as possible, the trade wastes, even if in an untreated condition, may be discharged into the Purakau Channel. Their discharge into this channel would mitigate the serious position which exists in and near Mangere Inlet and, in addition, would bring about a substantial general improvement.

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