Before the residual waste treatment options can be evaluated it is desirable for the Authority to have a clear idea as to how much residual waste will arise, where it will arise and where it might be treated. This allows the Authority to include considerations relating to facility size, transport and transfer issues and the treatment site into the appraisal process. Therefore, before the appraisal process starts it is advisable for the Authority to begin work on waste flow modelling and site identification.