Deleting projects from your project portfolio requires a
role with Manage Projects permissions. Projects can be deleted in two
ways:
•Single projects can be deleted using the trash can icon in the last column of the project list. Only users with Manage Projects permissions will see this icon. To delete a single project, simply locate the trash can icon in the project list row for the project you wish to delete. Click the trash can icon. You will be prompted to confirm before the project is deleted. Be careful – there is no “undo” option once a project is deleted!
•One or more projects can be deleted by selecting the desired
project(s) in the list and clicking the Delete button in the power
editing menu at the top left side of the page above the project list grid and
filtering fields. Again, this button will only be visible to users logged in
with Manage Projects permissions. You will be prompted to confirm before
proceeding. 
Again, there is no “undo” option
once a project is deleted, so use the multi-project delete option with
caution.