Environment and sustainability are key issues for the policy maker. A policy should be first designed and realistically inserted in his proper context (regional, national, european) in order to be correctly assessed. After that, suitable models need to be choose 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. It means that the model could be able to produce indicators useful to monitoring the policy other then macro indicators whose function is to verify its long term sustainability. We apply these concepts 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. Our modeling, evaluation oriented, aims at verify the policy effects in the long term, i.e. looking at structural change concerning all institutional sectors (households, firms and government).