The four primary functions in a waste retrieval system are as follows: accessing all of the waste within the tank configuration; mobilizing all of the waste, which can have varying physical properties; removing the bulk and residual mobilized waste; and transferring the waste to storage or processing equipment. Selection of retrieval and transfer systems must include all of these functions. Limitations on any one of these areas affect the whole process. This section categorizes according to function many available retrieval and transfer processes, with positive attributes and limitations. Additional information on these systems is referenced in the annexes.