(13)In order to ensure that the integrated urban wastewater management plans are cost-effective, it is important that they be based on best practices that have already been applied in urban areas. Therefore, the measures to be considered should be based on a thorough analysis of the local conditions and should favour a preventive approach aimed at limiting the collection of unpolluted rain waters and optimising the use of existing infrastructure to generate energy savings and contribute to emission reduction. With a preference for green and blue developments and investments, new grey infrastructure should be envisaged only where absolutely necessary.