The presentation is aimed to give all partners general comments on the decision trees they have proposed till now and to have a look to their formal correctness. We have established guidelines that may be useful in carrying out the decision tree design. In particular, we identified critical aspects or questions to be discussed, reviewed the methodological choices of the multi criteria analysis and suggested operational guidance. The first operational guidance we suggested is the use of Documentation Form within the Sesamo application. A question to be discussed was the spatial relation: if the effects of the alternatives will occur on more than one river stretch, we suggested to organize the decision tree in two ways: structure a subtree for each river stretch or split each indicator in relative values for the river stretches. Then, we have briefly reminded them the methodological choices for designing the decision trees (how to identify alternatives, criteria and indicators), we proposed common macro-criteria, that may be helpful in structuring the evaluation tree. Finally, we described all properties that indicators should have to design formally corrected trees.