Environment and sustainability are key issues for the policy maker. A policy should be first designed and realistically inserted in its proper context (regional, national, European) in order to be correctly assessed. After that, suitable models need to be chosen consistently with the policy context and with the evaluation purpose, to make easier the policy maker task. The aim of this paper is twofold. Firstly, to propose a Statistical Information System (SIS) approach in order to correctly write the policy and verify its internal and external consistency; secondly, to conceive model building with an evaluation purpose and not only with an
analytical one. This means that the model could be able to produce indicators useful to monitoring the policy other than macro indicators whose function is to verify its long term sustainability. These concepts are applied to a specific regional environmental policy: the premium/penalty system conceived to implement the separate collection in waste management. The SIS approach allows us to verify the quality of disposable information, to complete and eventually integrate them with ad hoc surveys, in order to build the environmental extended Social Accounting Matrix, the ESAM. This modelling, evaluation oriented, aims at verifying the policy effects in the long term, i.e. looking at structural change concerning all institutional sectors (households, firms and government).