If the project relates solely to the earthworks, the Materials Management Plan will in essence cover the bulk of the requirements of a Site Waste Management Plan (to be compliant with the Site Waste Management Plans requirements the Materials Management Plan would have to be top and tailed).
Where the project is larger than just earthworks, the detail within the Materials Management Plan would be a subset of the Site Waste Management Plans i.e. dealing with one waste stream – excavated arisings).